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[Display omitted] • Increasing the number of conjugated C=C bonds can inhibit the occurrence of ESIPT reaction. • The ICT process can be promoted by increasing the number of conjugated C=C bonds. • The difficulty of the ESIPT reaction can be judged by the potential energy curves. The electronic structure of the molecule is significantly influenced by the number of conjugated C=C bonds. In this work, the influence of the conjugated C=C bonds of the SNCN derivatives on the excited state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) properties are studied by density functional theory (DFT) and time-dependent density functional theory (TDDFT). The calculation level is proved to be reasonable by calculating electronic spectra. The hydrogen bond parameters, infrared vibrational frequency (IR), reduction density gradient (RDG) isosurface, topological analysis and potential energy curves of SNCN derivatives in ground state (S0) and the first excited state (S1) are analyzed. According to theoretical research results, ESIPT reaction has a higher likelihood of occurring in the S1 state. Moreover, the ESIPT reaction becomes more challenging to occur with the number of conjugated C=C bonds rising. Finally, the analyses of the frontier molecular orbitals (FMOs), dipole moment and charge transfer transition confirm that the ICT effect is aided by the increased number of conjugated C=C bonds. This work indicates that the number of conjugated C=C bonds can regulate the ESIPT and ICT processes, which provides guidance for the study of fluorescent groups with similar characteristics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Eight new organic dyes were designed. • The photovoltaic parameters of designed dyes were evaluated. • The theoretical PCEs of M4 , M7 , and M6 are as high as 19.93%, 15.80% and 15.38%. • M4 , M7 , and M6 are potential candidates as efficient sensitizers. In this work, a series of ZL003 -based free-metal sensitizers with the donor-acceptor-π- conjugated spacer-acceptor (D-A-π-A) structure were designed by modifying auxiliary electron acceptors for the potential application in dye-sensitized solar cells. The energy levels of frontier molecular orbitals, absorption spectra, electronic transition, and photovoltaic parameters for all studied dyes were systematically evaluated using density functional theory (DFT)/time-dependent DFT calculations. Results illustrated that thienopyrazine (TPZ), selenadiazolopyridine (SDP), and thiadiazolopyridine (TDP) are excellent electron acceptors, and dye sensitizers functionalized by these acceptors have smaller HOMO-LUMO gaps, obviously red-shifted absorption bands and stronger light harvesting. The present study revealed that the photoelectric conversion efficiency (PCE) of ZL003 is around 13.42 % with a J SC of 20.21 mA·cm−2, V OC of 966 mV and FF of 0.688 under the AM 1.5G sun exposure, in good agreement with its experimental value (PCE = 13.6 ± 0.2 %, J SC = 20.73 ± 0.20 mA·cm−2, V OC = 956 ± 5 mV, and FF = 0.685 ± 0.005.). With the same procedure, the PCE values for M4 , M6 , and M7 were estimated to be as high as 19.93 %, 15.38 %, and 15.80 % respectively. Hence, these three dyes are expected to be highly efficient organic sensitizers applied in practical DSSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mechanisms of the p -methoxyphenylpiperazine motif absorption and emission are studied. • While the excitation is based on a n,π → π* transition, the emission is π*→π. • The N(4) atom as a part of a 6-membered aliphatic ring adopts specific geometries. • DFT calculations with NBO and QTAIM analysis support the spectroscopic data. The p -methoxyphenylpiperazine motif can be found in many biologically active molecules, including approved drugs. It is characterized by a relatively weak fluorescence, which can be employed in different types of studies involving molecules with this motif. In this work, a thorough analysis of the absorption, excitation and emission spectra of the diphenyl(aminomethyl)phosphine and tris(aminomethyl)phosphine derivatives of p -methoxyphenylpiperazine, supported by the DFT calculations (ωB97XD/6-311++G(d,p)) with NBO and QTAIM analysis also for different model molecules (e.g. 1-(4-methoxyphenyl)-4-methylpiperazine) enabled determination of the mechanisms underlying beneath the electronic transitions and allowed to rationalize mixed solvent effects observed in electronic spectra of the studied compounds. Electronic transition from the ground state to the first excited state can be regarded as the n,π → π* transition with no solvatochromic effects, however the hydrogen bonds between the HBD solvent molecules and the nitrogen atom bound directly to the aromatic ring (N(4)) are shifting strongly the 1st absorption or excitation band maxima to the higher energies. Fluorescence band, as a result of the electron transition from the equilibrated 1st excited state to the ground state, can be described as the π*→π with positive solvatochromism. N(4) in the excited states adopts a sp2 hybridization and is no longer able to form HBs. On the other hand, increased electron density on the aromatic ring makes the emission processes vulnerable to its direct environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Structures of cyclic dimers and tetramer of adenine were studied by DFT calculations. • The characteristics of N-H···N interactions were studied by NBO and AIM calculations. • Complete vibrational assignments of cyclic dimers are presented. • Vibronic bands are observed in the electronic spectra. • Different scaled force constants values show the cyclic dimers of adenine. In this work, three different cyclic dimers and a tetramer of adenine taken from the experimental structure determined by X-ray diffraction have been studied by combination of experimental FT-IR, FT-Raman and UV–Visible spectra with hybrid B3LYP/6–311++G** and scaled quantum mechanical force field (SQMFF) calculations in order to perform the complete assignments of bands observed in the vibrational spectra. The characteristics of different N-H···N interactions of those three cyclic structures together with the group of IR bands observed between 2865 and 2599 cm−1 have been elucidated considering the tetrameric structure. The cyclic dimers and the tetramer of adenine confirm that the bands observed between 2865 and 2599 cm−1 are not due to N-H···N interactions but to bands of combination, as was previously suggested. The experimental available deuterated IR and terahertz spectra have allowed the complete assignments of regions of higher and lower wavenumbers. Good correlations were acquired comparing the theoretical IR, Raman and UV spectra of three species and the tetramer with the analogous experimental ones, suggesting the presence of all species in both phases. Vibronic bands are observed in the electronic spectra when adenine concentration is increased in aqueous solution evidencing the presence of monomer, tautomers and dimers, as reported by different studies. Similar characteristics of H bonds interactions are predicted for dimers 1 and 2 but different from the dimer 3, as revealed by using NBO and AIM calculations. Different scaled force constants values were found for the cyclic dimers 1 and 2, as compared to the corresponding to dimer 3. [ABSTRACT FROM AUTHOR]

In this work, the structure–property relationship of push–pull chalcone derivative (3DPNP) has been studied through spectroscopic experiments and density functional theory calculations. The figure on the right side shows the non-linear absorption and non-linear refraction curves of 3DPNP. [Display omitted] • The structure–property relationship of a chalcone-based push–pull molecule (3DPNP) was explored using combined experimental and theoretical studies. • The vibrational and electronic contribution to NLO activity of 3DPNP was estimated. • Frequency-dependent NLO calculations shows abrupt changes when the incident frequency is doubled which confirms SHG efficiency of 3DPNP. • Z-scan studied indicated that the molecule 3DPNP is suitable for optical limiting application in CW laser regime. • The optical limiting threshold of 3DPNP is found to be 3.26 kJ/cm2. In this work, the optical limiting response of a highly π-conjugated push–pull chalcone derivative (2 E)-3-(2,3-dimethoxyphenyl)-1-(3-nitrophenyl)prop-2-en-1-one (abbreviated as 3DPNP) has been investigated. The structure–property relationship of 3DPNP was explored through spectroscopic investigation and quantum chemical computations. The existence of weak-non-covalent interactions and charge transfer species that responsible for the chemical stability of 3DPNP were studied by AIM and NBO analyses. The quantitative and qualitative analysis of vibrational and electronic contribution to non-linear optical (NLO) response of 3DPNP were discussed in detail. The normal vibrational modes associated with a change in the dipole moment, polarizability, first- and second-order hyperpolarizabilities of 3DPNP were identified using DFT calculations followed by potential energy distribution (PED) analysis using Gaussian 09 W software and Gar2ped program, respectively. The changes in the NLO parameters with respect to the varying frequencies and electric dipole fields were studied. The abrupt changes in the NLO properties were noticed when the frequency doubled, confirming the second harmonic generation (SHG) efficiency of 3DPNP. From the non-linear absorption and refraction studies through the z-scan experiment, the optical limiting threshold value of 3DPNP is determined to be 3.26 kJ/cm2, which shows the suitability of the material for optical limiting applications in the continuous wave (CW) laser regime. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electronic spectra of various chalcones in different solvents were interpreted. • The effect of substituents on the CT band of chalcone derivatives was established. • The converged gas-phase geometries of the studied chalcones was optimized. • Optimized geometrical structures were optimized using DFT PBE0 functional with the basis set 6-311++G** • Spectral properties of substituted chalcones are compared with parent and related ketones. • The theoretical calculations were comparable with the experimental data. The electronic spectra of the title compounds were measured in ethanol and cyclohexane. Three band systems are distinguished in the spectra of which the first and second band systems are attributed to local excitation of Ph CH and Ph CO rings. The third absorption band is assigned to a charge transfer (CT) band and is associated with the CO−CH=CH moiety. The solvent plays an important role in the absorption spectra and causes the CT band to consist of two electronic transitions. The effect of substituents on the phenyl rings on the charge transfer band of chalcone derivatives was also established in the two solvents. The converged gas-phase geometries of the studied chalcones was optimized using the DFT PBE0 functional with the basis set 6-311++G**. DFT calculations has been performed for an ethanol solution (using TD-PBE0/6-311++G**) level to understand electronic transitions on terms of energies and oscillator strengths to study the substituent effect on the electronic transitions of the chalcone derivatives. To consider the solvation effect of ethanol on the absorptions, the integral equation formalism variant of the polarizable continuum model (IEFPCM) was used. The calculated energies were in good agreement with experiment results. The molecular modelling technique was followed to monitor the effect of substitutions on the HOMO/LUMO energy and total dipole moment. Transitions between natural transition orbitals are also described as part of this study. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Gabapentin derivative Schiff base was synthesized by condensing of Gabapentin with salicylaldehyde. • Microcrystals of Cu(Gasa) 2 were structurally determined by spectroscopic characterizations. • Cu(Gasa) 2 exhibited excellent visible-light driven photocatalytic activity towards organic dyes. A novel Gabapentin derivative Schiff base Gasa was synthesized by condensing Gabapentin with salicylaldehyde, which was further coordinated with Cu2+ in methanol to give a microcrystalline Cu(II) complex Cu(Gasa) 2. The synthesized Gasa and Cu(Gasa) 2 were further characterized by single-crystal X-ray diffraction, scanning electron microscopy (SEM), as well as the FT-IR, Raman, electronic and fluorescence spectra. Cu(Gasa) 2 exhibited excellent visible-light driven photocatalytic activities in removal of Congo red (CR) and Methylene blue (MB) dyes from aqueous solution in the presence of H 2 O 2 as oxidant. It was revealed that ∙OH radicals played the most important role in the photodegradation processes of organic dyes, and the photodegradation of CR and MB fitted well with the pseudo-first-order kinetic model. In addition, solid state luminescent properties of Gasa and Cu(Gasa) 2 were also studied in detail. [ABSTRACT FROM AUTHOR]

The article highlights a quinoline-based probe for the detection of Cd2+ over other metal ions with a nanomolar level detection limit. Both DFT and TD-DFT studies were carried out to explore the sensing mechanism as well as the theoretical electronic spectra. The utilization of the probe in real-life applications has been investigated in live cells. [Display omitted] • A quinoline-based probe for the detection of Cd2+ in near-aqueous medium. • Binding mode is confirmed by single crystal XRD analysis. • Nanomolar detection limits of Cd2+. • DFT and TD-DFT analysis of both ligand and its Cd2+ complex. • Positive response towards bioimaging in live RAW 264.7 cell line. The present investigation highlights a quinoline-based small molecule probe (DEQ) for the detection of Cd2+ among other metal ions in near-aqueous media. The probe DEQ and its Cd2+ complex (DEQ-Cd) have been synthesized and characterized by all possible spectroscopic methods. The weakly emissive DEQ showed its strong emission in the presence of Cd2+, which is attributed to the photoinduced electron transfer (PET) along with the chelation-enhanced fluorescence (CHEF) mechanism. The 1:1 binding mode between ligand and Cd2+ is confirmed by single crystal XRD analysis, which is further supported by Job's plot and HRMS. The detection limit of the probe to recognize Cd2+ was found to be as low as 89 nM. Furthermore, DEQ can act as a reversible fluorescence probe with the off-on-off mechanism by the alternative addition of Cd2+ and EDTA. DFT and TD-DFT studies exposed the proposed mechanism after Cd2+ insertion and the obtained results for electronic spectra are in line with the experimental results. The response towards pH was quite interesting and allowed us to study its application in live cell imaging. With all the positive results, the proposed ligand DEQ can be used as a potential probe for the detection of Cd2+ in real-life applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Photoinduced NO-linkage isomers were investigated in K 2 [RuF 5 NO].H 2 O ([RuFNO]). • Samples of [RuFNO] at 77 K were irradiated with laser light in a 260–1064 nm range. • The photoisomer generated by light were evidenced by IR spectroscopy. • A novel method to explore the electronic structure of [RuF 5 NO]2- ion is proposed. • The onset decay temperature for the MS1 photoisomer is about 180 K. Some mononitrosyl complexes of transition metals exhibit one or two metastable states (linkage isomers, MS1 and MS2) when irradiated at low temperatures with appropriate wavelengths. In this work, the generation of metastable state one (MS1) (or Ru-ON linkage isomer) in K 2 [RuF 5 NO].H 2 O at 77 K was studied by sample excitation using laser light in a wide range of wavelengths. The effects of irradiation was monitored by infrared spectroscopy. ν(NO) in the ground state was shifted by −161 cm−1 when the complex was excited to MS1, a magnitude similar to that observed in other transition metal nitrosyls for a such state. We report on the excitation and deactivation of metastable states by using a wide variety of laser lines. A novel method for exploring the electronic structure of [RuF 5 NO]2- through the generation of MS1 is proposed. For this purpose, a sample was carefully irradiated with the same intensity of light for all laser lines in the spectral region 260–1064 nm. The integrated area under the ν(NO) MS1 band was used as a measure of MS1 population. The profile peaks of the MS1 population (ν(NO) MS1 band area) vs. the irradiation wavelength fit well with those of the electronic spectrum of the [RuF 5 NO]2- ion in an aqueous solution. The onset temperature for MS1 decay in K 2 [RuF 5 NO].H 2 O, at approximately 180 K, is slightly lower than the average reported for other ruthenium-nitrosyl systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of ferrocenyl hetaryl ketones was studied by quantum chemical methods. • UV–vis, IR and NMR characteristics of the ketones were calculated. • Various hetaryl groups were included to establish patterns in these characteristics. • The patterns were elucidated in terms of structural and electronic parameters. • Recommendations for suitable computational protocols were presented. Quantum chemical calculations have been carried out to elucidate the electronic structure as well as to draw structure-property relationships for a series of ferrocenyl hetaryl ketones by means of simulated NMR, IR and UV–vis spectra. In this series, the list of hetaryl groups included furan-2-yl, thiophen-2-yl, selenophen-2-yl, 1 H -pyrrol-2-yl and N -methylpyrrol-2-yl. Density functional theory was employed to determine the ground-state properties of the five ketones while their excited-state properties were modeled using a broad range of theoretical methods, namely from time-dependent density functional theory to multiconfigurational and multireference ab initio approaches. The patterns in the 13C and 17O chemical shifts of the carbonyl group were explained by the geometrical twist of hetaryl rings and by the electronic parameters corresponding to π -bonds conjugation and group hardness. Furthermore, the corresponding 13C and 17O shielding constants were analyzed in terms of both their dia/paramagnetic and Lewis/non-Lewis contributions within the framework of natural chemical shielding theory. The pattern in the vibrational frequency of the carbonyl bond was connected with changes in its bond length and bond order. It was established that the electronic absorption spectra of the studied ketones are largely characterized by low-intensity d → π * transitions in the visible region and the dominant high-intensity π → π * transition in the UV region. Finally, the theoretical methods best suited for modeling the excited-state properties of such ketones were designated. [ABSTRACT FROM AUTHOR]

In this study, the therapeutic activity of a series of water-soluble triphenylamine (TP) photosensitizers (Ps) was explored by using theoretical simulations. The key photophysical parameters which determined the efficiency of Ps, such as absorption electronic spectra, singlet-triplet energy gaps and spin-orbit matrix elements were calculated at density functional theory and its time-dependent extension (DFT, TD-DFT). The calculated results showed that these TP photosensitizers possessed large two-photon absorption cross-section in the near-infrared region (NIR), efficient intersystem crossing (ISC) transition from the first singlet excited state to the low lying triplet excited states and sufficient energy for generating reactive oxygen species (ROS). These suitable features made these TP series holding great promise for applications in two-photon photodynamic therapy (PDT). These TP photosensitizers studied here in principle extended the application range of two-photon PDT in water solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • The π-π stacking interactions affect the fluorescence-related properties and the excited state proton transfer mechanism of hydroxyanthraquinone fluorophore. • The vertical transition is characterized with strong HOMO-LUMO transition of charge transfer character in the complexes. • The complexes exhibit an exothermic excited state intramolecular proton transfer in the solution media. • The π-π stacking interactions affect the absorption and emission bands of HA, and provide a large Stokes shifts resulting of the favorable ESIPT process. • The desirable fluorescence properties of π-π complexes are cross-validated by geometries, potential energy curve scanning, electronic and vibrational spectra, and frontier molecular orbital analysis. The impact of π-π stacking interactions on photo-physical properties of hydroxyanthraquinone (HA) has been investigated using the density functional (DFT) and time-dependent density functional theory (TD-DFT) calculations in the gas phase and solution media. The vertical transition is characterized with strong HOMO-LUMO transition in the complexes. The intramolecular hydrogen bond (IHB) made in the HA and π-π complexes is strengthened after S 0 → S 1 excitation, such that the proton transfers is facilitated in the first excited state. The complexes exhibit an exothermic excited state intramolecular proton transfer (ESIPT) in the solution media, which is a barrierless process for some complexes. The π-π stacking interaction affects the absorption and emission bands of HA, and provides a large Stokes shift. This indicates the desirable fluorescence properties of π-π complexes, which are cross-validated by geometries, potential energy curve scannings, electronic and vibrational spectra, and frontier molecular orbital analyses. [ABSTRACT FROM AUTHOR]

We measured the attenuated total reflectance-far ultraviolet (ATR-FUV) spectra of poly(ethylene glycol) (PEG; average molecular weights of 200, 300, and 400) and related materials in the liquid state in the 145–200-nm wavelength region. For appropriately assigning the absorption bands, we also performed theoretical simulation of the unit-number dependent electronic spectra. The FUV spectra of PEGs contain three bands, which are assigned to the transitions between n(CH 2 OCH 2 )-3s Rydberg state (176 nm), n(CH 2 OCH 2 )-3p Rydberg state (163 nm), and n(OH)-3p Rydberg state (153 nm). Since the contribution of n(OH) decreases compared to n(CH 2 OCH 2 ) with increase in the number of units, the ratios of the molar absorption coefficients, ε, at 153 nm relative to 163 nm, decrease. On the other hand, the ratio of ε at 176 nm to that at 163 nm increases with increase in the number of units, because of the difference in the number of unoccupied orbitals in the transitions. The calculated results suggest that n orbitals form two electronic bands. In the upper band, the electrons expand over the ether chain, whereas in the lower band, the electrons are localized in the terminal OH in the PEGs. [ABSTRACT FROM AUTHOR]

The S 0 → S i , i = 1–5 electronic transitions of four 8-(4-aniline)-BODIPY and four 8-( N , N -dimethyl)-BODIPY dyes, differ by number and position of methyl substituents in the BODIPY frame, were investigated theoretically using ab initio the coupled cluster doubles (CC2) and TD-CAM-B3LYP methods. Methyl substituents in the BODIPY frame and the aniline fragment at the meso position disturb energy of local excitations S 0 → S 1 , S 0 → S 3 , and S 0 → S 4 weakly in comparison with the fully unsubstituted BODIPY molecule. These transitions in experimental spectra form the most long-wave absorption bands at ca . 500 nm as well as absorption bands in the region of 300–400 nm. At the same time, the presence of aniline fragments leads to the appearance of new S 0 → S 2 transitions of the charge transfer character in electronic spectra of BODIPYs. We also found a linear relationship between vertical energy of these charge transfer transitions and the electron donating power of an aniline fragment and electron accepting power of the BODIPY core depending on the number and position of methyl groups. The CC2 method provides the best overall description of the excitation energies in line with the experimental observations. On average, the quality of TD-CAM-B3LYP is almost equal to that of CC2, however the TD method with the CAM-B3LYP functional slightly underestimates the CT excitation energy. [ABSTRACT FROM AUTHOR]

The Schiff base of the title has been synthesized and its crystal structure determined by single-crystal X-ray diffraction. The compound was characterized by IR, Raman, 1 H NMR, 13 C NMR and electronic absorption spectra. DFT calculations provide the quantum chemical basis for the observed molecular conformation. A study of intermolecular interactions of the title compound is compared with seven other closely related structures and reveals that molecules in most of the compounds are linked by a cooperative effect of strong and weak hydrogen bonds, C H … π, and π … π stacking interactions, and also lp … π contacts. Lattice energy calculations indicate that the dispersion component is the major contribution, with the coulombic term playing a significant role in the total energy. Interaction energies for molecular pairs involving N H···N bonds indicate a dominant contribution to packing stabilization coming from coulomb component. Hirshfeld surfaces and 2D–fingerprint plots allowed us to visualize different intermolecular contacts and its relative contributions to total surface in each compound. The analysis of electrostatic potential (ESP) maps correlates well with the computed energies providing evidences on the dominant electrostatic nature of N H···N and N H···O interactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • VCD spectroscopy as a powerful tool to distinquish structurally similar substances. • Detailed 3D structures of three new synthetic cannabinoids. • The stabilizing hydrogen bond was revealed. An increasing number of products containing synthetic cannabinoids pose a growing crisis to public health worldwide. Recently, a rising number of cases of serious adverse health effects, intoxications, and death cases associated with synthetic cannabinoids were reported. The current study represents the comprehensive structural analysis of three new synthetic cannabinoids (AB-, ADB- and AMB-FUBINACA) in solution investigated by electronic and vibrational circular dichroism together with the conventional methods of infrared and ultraviolet absorption spectroscopy, all supported by the density functional theory (DFT) calculations. The best level of theory to reproduce the experimental wavenumbers and wavelengths was found to be the B3PW91 method with a 6-311++G(d,p) basis set including the implicit solvent effect simulation. Very good agreement between the experimental and simulated spectra allowed us to determine the absolute configuration and a detailed interpretation of the IR absorption, VCD, ECD and UV spectra of AB-, ADB- and AMB-FUBINACA. In addition, the HOMO and LUMO electronic transitions were calculated. [ABSTRACT FROM AUTHOR]

Diazene is the smallest member of the azo compound which has distinct chemical properties widely used in synthetic chemistry. In order to understand the structures and properties of diazene through different stages, the intermolecular interactions need to be studied. We have reported the many-body interactions of linear and cyclic diazene oligomers (mono to pentamer) in gas and water solvent in addition to spectroscopic characterization. It is observed that the sum of two body interaction energy contributes more to binding energy than relaxation energy. Upon solvation, significant changes have been observed in infrared and electronic absorption spectra of linear and cyclic diazene oligomers in the gas phase compared to the water solvent state. [Display omitted] • Spectroscopic study of linear and cyclic diazene oligomers in gas and water solvent. • Upon solvation, significant changes observed in the spectroscopic characterization. • NTOs studied for diazene oligomers in gas & solvent, IEFPCM used for solvent effect. • Many-body interaction of linear and cyclic diazene oligomers in gas and water solvent. • Sum of 2-body interaction contributes more to binding energy than relaxation energy. The present study reports the many-body analysis and spectroscopic characterization of linear and cyclic diazene oligomers in gas and water solvent states. The oligomers of diazene from monomer to pentamer have been considered for the study. The spectroscopic studies such as geometrical parameters, infrared spectra, electronic absorption spectra, and natural transition orbitals (NTOs) were reported. Many-body analysis techniques have been implemented to study the interactions among the diazene oligomers. These calculations have been performed using exchange and correlation functional (B3LYP) and 6–311++G (d,p) basis set. The geometrical parameters and infrared modes of monomer diazene in the gas state are well-matched with the available experimental determinations at this level of theory. A significant change in vibrational modes of linear and cyclic diazene oligomers has been observed in the gas phase-to-water solvent state. The time-dependent density functional theory (TD-DFT) has been used to calculate the electronic absorption spectra of diazene oligomers. The Wavelength of electronic transitions, oscillator strength, and HOMO to LUMO gap has been reported. Many-body analysis shows that two-, three-, four-, and five-body energies have a remarkable contribution to the binding energy in addition to relaxation energies. All these calculations have been performed using Gaussian 16 program package. [ABSTRACT FROM AUTHOR]

Diazene is the smallest member of the azo compound which has distinct chemical properties widely used in synthetic chemistry. In order to understand the structures and properties of diazene through different stages, the intermolecular interactions need to be studied. We have reported the many-body interactions of linear and cyclic diazene oligomers (mono to pentamer) in gas and water solvent in addition to spectroscopic characterization. It is observed that the sum of two body interaction energy contributes more to binding energy than relaxation energy. Upon solvation, significant changes have been observed in infrared and electronic absorption spectra of linear and cyclic diazene oligomers in the gas phase compared to the water solvent state. [Display omitted] • Spectroscopic study of linear and cyclic diazene oligomers in gas and water solvent. • Upon solvation, significant changes observed in the spectroscopic characterization. • NTOs studied for diazene oligomers in gas & solvent, IEFPCM used for solvent effect. • Many-body interaction of linear and cyclic diazene oligomers in gas and water solvent. • Sum of 2-body interaction contributes more to binding energy than relaxation energy. The present study reports the many-body analysis and spectroscopic characterization of linear and cyclic diazene oligomers in gas and water solvent states. The oligomers of diazene from monomer to pentamer have been considered for the study. The spectroscopic studies such as geometrical parameters, infrared spectra, electronic absorption spectra, and natural transition orbitals (NTOs) were reported. Many-body analysis techniques have been implemented to study the interactions among the diazene oligomers. These calculations have been performed using exchange and correlation functional (B3LYP) and 6–311++G (d,p) basis set. The geometrical parameters and infrared modes of monomer diazene in the gas state are well-matched with the available experimental determinations at this level of theory. A significant change in vibrational modes of linear and cyclic diazene oligomers has been observed in the gas phase-to-water solvent state. The time-dependent density functional theory (TD-DFT) has been used to calculate the electronic absorption spectra of diazene oligomers. The Wavelength of electronic transitions, oscillator strength, and HOMO to LUMO gap has been reported. Many-body analysis shows that two-, three-, four-, and five-body energies have a remarkable contribution to the binding energy in addition to relaxation energies. All these calculations have been performed using Gaussian 16 program package. [ABSTRACT FROM AUTHOR]

The vibrationally resolved electronic spectra of five metal-free NKX-2587 derivatives containing heteroatom with different atomic sizes and electronegativity, were simulated within the Franck-Condon approximation including the Herzberg-Teller and Duschinsky effects, aimed at exploring the correlation of vibronic structure associated with the spectrum and efficiency of dye sensitized solar cells (DSSCs). The parameters of short-circuit current density ( J sc ) and open circuit voltage ( V oc ) involving efficiency of DSSCs, such as total dipole moments (μ normal ), the light harvesting efficiency ( LHE ), injection driving force ( ∆ G inject ), and the number of electrons in the conduction band ( n c ), were calculated and discussed in detail. Results showed that the heteroatoms in the same period with large size and weak electronegativity and the ones in the same main group with large size and weak electronegativity are beneficial to V o c . The sizes and electronegativity of the heteroatoms have a weak effect on J sc . The low-frequency modes play important roles in enhancing the intensities of the electronic spectra and structures can affect light harvesting efficiency ( LHE ). In this sense, our results provided guidance for understanding the sources of spectral intensities of dye molecules, and a valuable help for rational design of new molecules to improve the energy conversion efficiency ( η ) of DSSCs. [ABSTRACT FROM AUTHOR]

Theoretical and experimental bands have been assigned for the Fourier Transform Infrared and Raman spectra of the bis(diethyldithiocarbamate)Mn(II) complex, [Mn(DDTC)2]. The calculations have been based on the DFT/B3LYP method, second derivative spectra and band deconvolution analysis. The UV–vis experimental spectra were measured in acetonitrile solution, and the calculated electronic spectrum was obtained using the TD/B3LYP method with 6-311G(d, p) basis set for all atoms. Charge transfer bands and those d-d spin forbidden were assigned in the UV–vis spectrum. The natural bond orbital analysis was carried out using the DFT/B3LYP method and the Mn(II) hybridization leading to the planar geometry of the framework was discussed. Surface enhanced Raman scattering (SERS) was also performed. Mulliken charges of the normal modes were obtained and related to the SERS enhanced bands. [ABSTRACT FROM AUTHOR]

The molecular structure of a new complex of copper (II) with (E)-9-ethyl-3-(2-(6-(4-methylpyridin-2-yl)pyridin-3-yl)vinyl)-9H-carbazole ([Cu 2 (emppc) 2 Cl 2 ]Cl 2 ) was optimized with B3LYP/LanL2DZ, PBE1PBE/LanL2DZ and M062X/LanL2DZ theoretical level. The ligand, (E)-9-ethyl-3-(2-(6-(4-methylpyridin-2-yl)pyridin-3-yl)vinyl)-9H-carbazole (emppc), binds to Cu(II) ions with a bi-dentate mode, two Cl − serve as bridging ligand, each Cu(II) ion has a highly distorted tetrahedron coordination geometry. With M062X/LanL2DZ theoretical level, the calculated interaction energies of Cu(II) with coordination atoms N are between 183.3–200.0 kJ mol − 1 for α spin and 319.4–324.9 kJ mol − 1 for β spin, and interaction energies of Cu(II) with coordination atoms Cl atom are 248.0–252.4 kJ mol − 1 for α spin and 332.6–333.6 kJ mol − 1 for β spin. The experimental Fourier transform infrared spectrum was assigned. The calculated IR based on B3LYP/LanL2DZ, PBE1PBE/LanL2DZ and M062X/LanL2DZ methods were performed and compared with experimental results. The UV–Vis experimental spectra of [Cu 2 (emppc) 2 Cl 2 ]Cl 2 was measured in methanol solution. The calculated electronic spectrum was performed with TD/M062X and PCM-TD/M062X methods with LanL2DZ basis set. The nature bond orbital analysis and temperature dependence of the thermodynamic properties were calculated with the same methods. [ABSTRACT FROM AUTHOR]

We systematically studied the vibrational-resolved electronic spectra of group IV dichlorides using the Franck–Condon approximation combined with the Duschinsky and Herzberg–Teller effects in harmonic and anharmonic frameworks (only the simulation of absorption spectra includes the anharmonicity). Calculated results showed that the band shapes of simulated spectra are in accordance with those of the corresponding experimental or theoretical ones. We found that the symmetric bend mode in progression of absorption is the most active one, whereas the main contributor in photoelectron spectra is the symmetric stretching mode. Moreover, the Duschinsky and anharmonic effects exert weak influence on the absorption spectra, except for PbCl 2 molecule. The theoretical insights presented in this work are significant in understanding the photophysical properties of MCl 2 (M = C, Si, Ge, Sn, Pb) and studying the Herzberg–Teller and the anharmonic effects on the absorption spectra of new dichlorides of this main group. [ABSTRACT FROM AUTHOR]

[Display omitted] • CoP-TBO and NiP-TBO both have worse planarity and smaller dipole moments than other compounds. • MgP-TBO and H 2 P-TBO seem to have potential to be new donors. • Metal substitutions blue-shift the wavelength of absorption peaks and lower total absorption strength. Porphyrin compounds have unique advantages because of their wide absorption range (about 300–1000 nm) and good planarity. At present, the effects of metal substitutions of porphyrin compounds on their photovoltaic properties are still not clear. In this paper, we have systematically modelled a series of porphyrin donors MP-TBO (M = 2H, Mg, Cu, Fe, Co, Zn and Ni), in which ZnP-TBO has been experimentally synthesized and the power conversation efficiency of organic solar cell based on it is up to 12.08 %. The photovoltaic properties of these MP-TBO molecules have been investigated via density functional theory (DFT) and time-dependent DFT. We find that CoP-TBO and NiP-TBO both have worse planarity and smaller dipole moments than other compounds. The electronic absorption spectra of these porphyrin donors all show three main absorption peaks. However, metal substitutions blue-shift the wavelength of absorption peaks and lower total absorption strength in the visible and near-infrared regions. Finally, we find that MgP-TBO and H 2 P-TBO seem to be potential donors because both have more red-shifted wavelength of absorption peaks and higher absorption strength than other metal substitutions. [ABSTRACT FROM AUTHOR]

[Display omitted] Recently, based on the mechanism of excited-state intramolecular proton transfer (ESIPT), a new fluorescent probe named 3-(benzo[d]thiazol-2-yl)-5-bromosalicylaldehyde-4N-phenyl thiosemicarbazone (BTT) was successfully synthesized [Analyst 146 (2021) 4348–4356.]. However, the importance of ESIPT processes of BTT probe and the mechanism of detecting Zn2+ ions have not been studied in detail. In this study, the photochemical behavior of ESIPT-chromophore and the photophysical changes of detecting Zn2+ ions were explained at the molecular level for the first time. The calculated spectral values were in agreement with the experiment. We not only confirmed the excited state hydrogen-bond strengthening by interaction region indicator (IRI), but also scanned the potential energy curves of BTT molecule in different electronic states, which confirmed that the hydrogen proton is easier to transfer in the first excited state. In addition, we had given the reasonable structure of the BTT-Zn2+ complex (L1) by comparing the binding free energies. The hole-electron distribution and interfragment charge transfer (IFCT) methods proved the excitation type of intraligand charge transfer (ILCT). Finally, the photophysical phenomenon of BTT for detecting Zn2+ ions is explained by calculating the electronic spectra and the energy gap (E gap) between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). [ABSTRACT FROM AUTHOR]

[Display omitted] • Zr(IV), Hg(II) and U(VI) complexes of albendazole. • Spectrophotometry determination of Zr(IV), Hg(II) and U(VI) as albendazole complexes in many samples. • The microbial and molecular docking studies. Spectrophotometry was used to determine trace amounts of Zirconium(IV), Mercury(II) and Uranium(VI) in environmental, biological, pharmaceutical and industrial samples. The determination depend on the complexation reactions between albendazole reagent and metal ions [Zr(IV), Hg(II) and U(VI)] at 555 nm, 485 nm and 510 nm, respectively. The experimental conditions were explored to reach the optimum conditions for albendazole-metal ions interaction, including detection of a suitable wavelength, medium (pH), reagent concentration, surfactants effect, reaction time and temperature. Under optimum conditions, the complexes displayed apparent molar absorptivities of 0.8350 × 104, 0.6210 × 104 and 0.7012 × 104 L mol−1 cm−1; Sandell's sensitivity of 0.01092, 0.03230 and 0.03394 µg cm−2 and with linearity ranges of 1.0–120.0, 3.0–200.0 and 1.0–150.0 µg mL−1 for the developed methods, respectively. Furthermore, Elemental analysis, thermal analysis (TGA, DTG), IR, 1HNMR, spectroscopies, electrical molar conductivity and magnetic moment measurements were used to determine the structures and characteristics of the complexes. A careful examination of the IR spectra revealed that the ligand interacted with all of the metal ions described as a bidentate via the oxygen of the carbonyl of the ester moiety and the nitrogen atom of the heterocyclic C N group. An octahedral geometry for Zr(IV), Hg(II) and U(VI) complexes has been postulated based on magnetic and electronic spectrum data. The band gap values indicated that these complexes were semi-conductors and belong to the same class of extremely effective solar materials. The albendazole ligand and its complexes have been biologically tested against a variety of bacterial and fungal strains, and molecular docking studies have been conducted to evaluate the optimal binding site and its inhibitory action. [ABSTRACT FROM AUTHOR]

Schiff condensation of 2,6-diformyl 4-methylphenol with semicarbazide hydrochloride in 1:2 molar ratio produces the bis (semicarbazone) ligand, herein called H 3 L. A comprehensive spectroscopic analysis of the compound was performed by 1 H and 13 C NMR, FTIR and electronic spectroscopies. Assignments to the UV–vis spectrum of H 3 L were supported by semi-empirical quantum mechanics ZINDO/S calculations. The ligand H 3 L forms monoclinic crystals in the space group P2 1 / c and its structure is stabilized by classic hydrogen bonds with propanone molecules. It promptly reacts with first row metal ions to produce the following coordination compounds: [Co 2 (L)(μ-NO 3 )]·DMF, [Ni 2 (H 2 L)(μ-CH 3 COO)(CH 3 COO) 2 ]·2H 2 O, [Cu 2 (L)(μ-NO 3 )(H 2 O) 2 ]·H 2 O, [Cu 2 (L)(μ-CH 3 COO)(H 2 O) 2 ]·H 2 O and [Cu 2 (H 2 L)(μ-Cl)Cl 2 ]·3H 2 O, that have different compositions, depending on the degree of deprotonation of the ligand upon coordination. Electronic and EPR spectroscopies as well as effective magnetic moment measurements of the complexes were used in an attempt to better understand their mode of coordination, the microsymmetry around the metal ions and magnetic properties. [ABSTRACT FROM AUTHOR]

In the present work, a new phenylbenzimidazole derivatized fluorescent sensor ( L ) (J. Lumin. 147 (2014) 179), has been investigated on the excited state proton transfer (ESPT) based on the time-dependent density functional theory (TDDFT) method. The calculated absorption and fluorescence spectra based on the TDDFT method are in agreement with the experimental results. Two kinds of structures of L chromophore are found in the first excited (S 1 ) state, which may be due to the proton transfer reactive. Hydrogen bond strengthening has been testified in the S 1 state based on comparing staple bond lengths and bond angles involved in hydrogen bonding between the S 0 state and the S 1 state. In addition, the calculated infrared spectra at the N–H stretching vibrational region and calculated hydrogen bond energy also declare the phenomenon of hydrogen bond strengthening. The frontier molecular orbitals (MOs) and Mulliken's charge distribution analysis method as well as natural bond orbital (NBO) demonstrate the charge distribution, which provides the tendency of ESIPT reaction. The potential energy surfaces of the S 0 and S 1 states are constructed to explain the mechanism of the proton transfer in the excited state in detail. In addition, the ESIPT process of sensor L is dependent on different solvents. [ABSTRACT FROM AUTHOR]

B3LYP is one of the most widely used functional for the prediction of electronic circular dichroism spectra, however if the studied molecule contains aromatic nitro group computations may fail to produce reliable results. A test set of molecules of known stereochemistry were synthesized to study this phenomenon in detail. Spectra were computed by B3LYP and CAM-B3LYP functionals with 6–311 ++G(2d,2p) basis set. It was found that the range separated CAM-B3LYP gives better predictions than B3LYP for all test molecules. Fragment population analysis revealed that the nitro groups form highly localized molecule orbitals but the exact composition depends on the functional. CAM-B3LYP allows sufficient spatial overlap between the nitro group and distant parts of the molecule, which is necessary for the accurate description of excited states especially for charge transfer states. This phenomenon and the synthesized test molecules can be used to benchmark theoretical methods as well as to help the development of new functionals intended for spectroscopical studies. [ABSTRACT FROM AUTHOR]

In the present work, TDDFT has been used to investigate the excited state intramolecular proton transfer (ESIPT) mechanism of a new chromophore II [Sensors and Actuators B: Chemical. 202 (2014) 1190]. The calculated absorption and fluorescence spectra agree well with experimental results. In addition, two types of II configurations are found in the first excited state (S 1 ), which can be ascribed to the ESIPT reaction. Based on analysis of the calculated infrared (IR) spectra of O–H stretching vibration as well as the hydrogen bonding energies, the strengthening of the hydrogen bond in the S 1 state has been confirmed. The frontier molecular orbitals (MOs), Hirshfeld charge distribution and the Natural bond orbital (NBO) have also been analyzed, which displays the tendency of the ESIPT process. Finally, potential energy curves of the S 0 and S 1 states were constructed, demonstrating that the ESIPT reaction can be facilitated based on the photo-excitation. [ABSTRACT FROM AUTHOR]

Diterpenoid forskolin was isolated from Coleus forskolii. The electronic absorption and emission studies of forskolin were investigated in various solvents with an aim to improve its detection limits. The two chromophores present in the diterpenoid are not conjugated leading to the poor absorption and emission of UV light. The absorption and fluorescence spectra were solvent specific. In the presence of a monodentate ligand, triethylamine the detection of forskolin is improved by 3.63 times in ethanol with the fluorescence method and 3.36 times in DMSO by the absorption spectral method. The longer wavelength absorption maximum is blue shifted while the lower energy fluorescence maximum is red shifted in the presence of triethylamine. From the wavelength of fluorescence maxima of the exciplex formed between excited forskolin and triethylamine it is concluded that the order of reactivity of hydroxyl groups in the excited state forskolin is in the reverse order to that of the order of the reactivity of hydroxyl groups in its ground state. [ABSTRACT FROM AUTHOR]

Based on the time-dependent density functional theory (TDDFT), the excited-state intermolecular proton transfer (ESIPT) mechanism of water-bridged 7-azaindole has been investigated theoretically. The calculations of primary bond lengths and the IR vibrational spectra between the S 0 state and the S 1 state that verified the intramolecular hydrogen bond were strengthened. The fact that reproduced experimental absorbance and fluorescence emission spectra well theoretically demonstrate that the TDDFT theory we adopted is reasonable and effective. In addition, intramolecular charge transfer based on the frontier molecular orbitals demonstrated the indication of the ESIPT reaction. The constructed potential energy curves of ground state and the first excited state based on keeping the H 2 ···O 3 and H 6 ···N 7 distances fixed at a series of values have been used to illustrate the ESIPT process. A relative lower barrier of 5.94 kcal/mol in the S 1 state potential energy curve for type II (lower than that of 9.82 kcal/mol in the S 1 state for type I) demonstrates that type II ESIPT process occurs firstly in 7Al-2H 2 O complex. [ABSTRACT FROM AUTHOR]

The environmental pollutant 2-nitrobenzanthrone (2-NBA) poses human health hazards, and is formed by atmospheric reactions of NO X gases with atmospheric particulates. Though its mutagenic effects have been studied in biological systems, its comprehensive spectroscopic experimental data are scarce. Thus, vibrational and optical spectroscopic analysis (UV–Vis, and fluorescence) of 2-NBA was studied using both experimental and density functional theory employing B3LYP method with 6-311 + G(d,p) basis set. The scaled theoretical vibrational frequencies show good agreement to experiment to within ~ 5 cm − 1 and < 20 cm − 1 for frequencies < 1800 cm − 1 and 2700–3200 cm − 1 , respectively. In addition, predictions of the DFT frequencies below 1800 cm − 1 yield an overall root mean square (RMS) of ± 20.1 and ± 20.6 cm − 1 for benzanthrone and 2-NBA, respectively. On the basis of normal coordinate analysis complete assignments of harmonic experimental infrared and Raman bands are made. The influence of the nitro group substitution upon the benzanthrone structure and symmetric CH vibrations, and electronic spectra is noted. This study is useful for the development of spectroscopy–mutagenicity relationships in nitrated polycyclic aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

The electronic absorption spectra of some 2-azidobenzothiazoles were measured in different solvents. The effects of solvent and substitution on the spectra were investigated. Substitution by a bromine atom and by a nitro group have significant effects on both band maxima and band intensity. Correlation between the spectra of the studied compounds and the corresponding hydrocarbons proved to be weak, whereas the correlation between the observed spectra and those calculated is adequate. Theoretical treatment of the ultraviolet spectra of the studied compounds was carried out by using the TD–DFT procedures, at the B3LYP level and the 6-311+G ∗∗ basis sets, the results compared well with the experimental values. The computed molecular orbitals of the ground state indicate that some orbitals are “localized- π ” or “localized σ ” molecular orbitals while the others are delocalized orbitals. The calculated functions of the excited states lead to an accurate assignment of the bands observed in the spectra. [ABSTRACT FROM AUTHOR]

Geometrical optimizations of the ground and first excited states of benzimidazole and indene were performed using the density functional theory (DFT) and its time-dependent extension methods (TD-DFT), respectively. Their vibrationally resolved 1 L b ( 1 A′) ↔ S 0 ( 1 A′) absorption and fluorescence spectra were simulated within the Franck–Condon approximation including the Herzberg–Teller (HT) and Duschinsky effects. Calculated results revealed that, with the HT and Duschinsky effects getting involved, the simulated weak 1 L b ( 1 A′) ↔ S 0 ( 1 A′) electronic spectra of the two molecules excellently reproduce the experimental findings. Based on the experimental data and other theoretical results, we tentatively assigned most of the vibrational normal modes which emerged in the experimental spectra of the two molecules. The present theoretical insights are expected to help us understand the nature of electronic transitions in the vibrationally resolved absorption and fluorescence spectra of benzimidazole and its analogues. [ABSTRACT FROM AUTHOR]

In the present work, 3, 3′, 4′, 7-tetrahydroxyflavone (fisetin), as one of the most extensive distributed flavonoids, has been investigated on the excited state proton transfer (ESPT) based on the time-dependent density functional theory (TDDFT) method. The calculated absorption and fluorescence spectra based on the TDDFT method are in agreement with the experimental results. Two kinds of structures of fisetin chromophore are found in the first excited ( S 1 ) state, which may be due to the proton transfer reactive. Hydrogen bond strengthening has been testified in the S 1 state based on comparing staple bond lengths and bond angles involved in hydrogen bonding between the S 0 state and the S 1 state. In addition, the calculated infrared spectra at the O–H stretching vibrational region and calculated hydrogen bond energy also declare the phenomenon of hydrogen bond strengthening. The frontier molecular orbitals (MOs) analysis and Natural bond orbital (NBO) manifest the intramolecular charge transfer of fisetin chromophore, which reveals the tendency of proton transfer. The potential energy surfaces of the S 0 and S 1 states are constructed to explain the mechanism of the proton transfer in excited state in detail. [ABSTRACT FROM AUTHOR]

In this study, computational calculations of a new quinoline derivative: 8-((4-(methylthio)-2,5-diphenylfuran-3-yl)methoxy)quinoline is carried out using ab initio methods. The geometry optimization as well as fundamental frequencies of the most stable configuration of the title compound is reported. A detailed study of Infrared spectrum, chemical shifts and electronic spectrum of the title compound is also presented. The Gauge-Invariant Atomic Orbital approach is used to calculate the proton and carbon chemical shifts of the title compound. The natural bond orbital analysis of the title compound is also reported in order to understand the stability of the molecule which arises from hyper conjugative interactions and charge delocalization. The theoretical electronic absorption spectrum is also reported using the time dependent density functional approach. The molecular structure along with vibrational frequencies as simulated for binding of iron with the title compound is also reported using ab initio methods. [ABSTRACT FROM AUTHOR]

By using atomic force microscopy, birth and spread has proved to be the primary growth mechanism for l -prolinium phosphate (LPP). The phenomenon of newly formed islands expanding to the edge of the preceding terrace was observed. The optimized molecular structure and the molecular properties were calculated by density functional theory method. Natural bond orbital analysis was carried out to demonstrate the various inter and intramolecular interactions that are responsible for the stabilization of LPP leading to high NLO activity. Molecular electrostatic potential, frontier molecular orbital analysis and thermodynamic properties were investigated to get a better insight of the molecular properties. Global and local reactivity descriptors were computed to predict the reactivity and reactive sites on the molecules. Non-linear optical (NLO) properties such as the total dipole moment ( μ ) and first order hyperopolarizability ( β ) were also calculated to predict NLO behavior. [ABSTRACT FROM AUTHOR]

The crystal structure of a new coordination compound tri(2-(2,6-dichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) Co(II) complex ([Co(dcpip) 3 ]Cl 2 ) was measured with X-ray diffraction measurements. The compound is crystallizes triclinic, Pī space group. The ligand, 2-(2,6-dichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline(dcpip), binds to Co(II) ions with a bis-dentate mode, and each Co(II) ion with a distorted octahedral coordination geometry. The calculated interaction energies of Co(II) with coordination atoms N are between 101.7–206.5 kJ/mol and 115.3–230.9 kJ/mol for B3LYP/6-31+G ∗ and PBE1PBE/6-31+G ∗ theoretical methods, respectively. The experimental Fourier transform infrared spectrum was assigned. The calculated IR based on B3LYP/6-31+G ∗ and PBE1PBE/6-31+G ∗ methods were performed and compared with experimental results. The UV–Vis experimental spectrum of [Co(dcpip) 3 ]Cl 2 was measured in methanol solution. The calculated electronic spectrum was performed with TD/B3LYP and TD/PBE1PBE methods with 6-31+G ∗ basis set. The first and second order hyperpolarizability for the compound was calculated. The calculated values of γ tot are −1.5551344 × 10 −33 esu for B3LYP method and −1.3323259 × 10 −33 esu for PBE1PBE method. The nature bond orbital analysis and temperature dependence of the thermodynamic properties were calculated with the same methods. [ABSTRACT FROM AUTHOR]

The platinum complexes of Schiff base ligands derived from 4-aminoantipyrine and a few substituted aldehydes were synthesized and characterized by elemental analysis, mass, 1 H NMR, IR, electronic spectra, molar conductance, and powder XRD. The structure of one of the ligands L 5 was confirmed by a single crystal XRD analysis. The Schiff base ligand crystallized in the triclinic, space group P-1 with a = 7.032(2) Ǻ, b = 9.479(3) Ǻ, c = 12.425(4) Ǻ, α = 101.636(3)°, β = 99.633(3)°, γ = 94.040(3)°, V = 795.0(4) Ǻ 3 , Z = 2, F (0 0 0) = 352, D c = 1.405 mg/m 3 , μ = 0.099 mm −1 , R = 0.0378, and wR = 0.0967. The spectral results show that the Schiff base ligand acts as a bidentate donor coordinating through the azomethine nitrogen and the carbonyl oxygen atoms. The geometrical structures of these complexes are found to be square planar. Antimicrobial studies indicate that these complexes exhibit better activity than the ligand. The anticancer activities of the complexes have also been studied towards human cervical cancer cell line (HeLa), Colon Cancer Cells (HCT116) and Epidermoid Carcinoma Cells (A431) and it was found that the [Pt(L 3 )Cl 2 ] complex is more active. [ABSTRACT FROM AUTHOR]

Ground state properties of 2,4-diphenyl-1,4-dihydrobenzo[4,5]imidazo[1,2-a]pyrimidine, compound 1 , and its derivatives are investigated experimentally and theoretically in Dioxane and DMF. The calculations show that all the studied compounds ( 1 – 7 ) are non-planar, resulting in a significant impact on the electronic and structural properties. The ground state properties of compounds 1 – 7 at B3LYP/6-311G (d, p) show that compound 5 has the lowest E HOMO , E LUMO , and Δ E indicating highest reactivity. Compound 7 is found to have the highest polarity. The observed UV spectra in Dioxane and DMF of compounds 1 – 4 show 2 bands, while compounds 5 – 7 show 4 bands in both solvents. Band maxima ( λ max ) and intensities of the spectra are found to have solvent dependence reflected as blue and red shifts. The theoretical spectra computed at TD-B3LYP/6-311G (d, p) in gas phase, Dioxane and DMF indicate a good agreement with the observed spectra. [ABSTRACT FROM AUTHOR]

In the present paper the vibrational, electronic and nonlinear optical properties of three N-aryl ring substituted (Z)-N-(4-amino-5-(4-chlorophenyl)-3-phenylthiazol-2(3H)-ylidene)benzamide compounds have been investigated by UV–vis, FT-IR and FT-Raman spectroscopic measurements. The electrochemical properties of the compounds were measured by cyclic voltammetry. Density functional theory calculations with B3LYP/6-31 + G(d,p) basis set was used to determine the ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities and Raman activities of title compounds. Potential energy distributions (PEDs) and normal modes, for the spectral data computed at B3LYP/6-31 + G(d,p) level, have also been obtained from force-field calculations. A comparison of the theoretical spectra and experimental FT-IR and FT-Raman spectra of the title molecule has been made and full vibrational assignments of the observed spectra have been proposed. The substituent effect on the electronic properties of the title compounds were investigated by time-dependent density functional theory calculations. [ABSTRACT FROM AUTHOR]

In this work, the influence of substituents on the electronic transitions of model 8-R-BODIPY dyes (R = NMe 2 , NH 2 , OH, CH 3 , H, F, SH, Cl, Br, CF 3 , CN, and NO 2 ) was investigated theoretically using time-dependent density functional theory (TD-DFT) and ab initio coupled-cluster doubles (CC2) quantum chemical calculations. Quantum chemical modeling shows a direct relationship between the electron donating and electron withdrawing character of substituents expressed by Hammett substituent constants ( σ p ) and changes in energy of the HOMO–LUMO gap modulating spectral shifts of the S 0 → S 1 transition. Good linear correlations of the calculated LUMO energies and σ p as well as the shape of the HOMO and LUMO allow to obtain a reasonable explanation for the observed effects of substituents. [ABSTRACT FROM AUTHOR]

In this study, FT-IR, FT-Raman, NMR and UV spectra of 1-phenyl-1-propanol, an intermediate of anti-depressant drug fluoxetine, has been investigated. The theoretical vibrational frequencies and optimized geometric parameters have been calculated by using HF and density functional theory with the hybrid methods B3LYP, B3PW91 and 6-311+G(d,p)/6-311++G(d,p) basis sets. The theoretical vibrational frequencies have been found in good agreement with the corresponding experimental data. 1 H and 13 C NMR spectra were recorded and chemical shifts of the molecule were compared to TMS by using the Gauge-Independent Atomic Orbital (GIAO) method. A study on the electronic and optical properties, absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies are performed using HF and DFT methods. The thermodynamic properties (heat capacity, entropy and enthalpy) at different temperatures are also calculated. NBO analysis is carried out to picture the charge transfer between the localized bonds and lone pairs. The local reactivity of the molecule has been studied using the Fukui function. NLO properties related to polarizability and hyperpolarizability are also discussed. [ABSTRACT FROM AUTHOR]

The FTIR and FT-Raman spectra of 2-(cyclohexylamino)ethanesulfonic acid were recorded in the regions 4000–400 cm −1 and 4000–50 cm −1 respectively. The structural and spectroscopic data of the molecule in the ground state were calculated using Hartee–Fock and Density functional method (B3LYP) with the correlation consistent-polarized valence double zeta (cc-pVDZ) basis set and 6-311++G(d,p) basis set. The most stable conformer was optimized and the structural and vibrational parameters were determined based on this. The complete assignments were performed based on the Potential Energy Distribution (PED) of the vibrational modes, calculated using Vibrational Energy Distribution Analysis (VEDA) 4 program. With the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound were carried out. Thermodynamic properties and Atomic charges were calculated using both Hartee–Fock and density functional method using the cc-pVDZ basis set and compared. The calculated HOMO–LUMO energy gap revealed that charge transfer occurs within the molecule. 1 H and 13 C NMR chemical shifts of the molecule were calculated using Gauge Including Atomic Orbital (GIAO) method and were compared with experimental results. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using Natural Bond Orbital (NBO) analysis. The first order hyperpolarizability ( β ) and Molecular Electrostatic Potential (MEP) of the molecule was computed using DFT calculations. The electron density based local reactivity descriptor such as Fukui functions were calculated to explain the chemical reactivity site in the molecule. [ABSTRACT FROM AUTHOR]

A combinational study of structural chemistry and dyestuff chemistry has been carried out to reveal the structure–performance relationship for eight disperse azo dyes by comparing their structures, electronic spectra, solvatochromism and theoretic computations. All eight structural analogues have the same 4-nitro-4′-amino-azobenzene donor– π –acceptor skeleton but different substituted groups, namely, R 1 and R 2 in ring A, R 3 , R 4 and R 5 in Ring B. X-ray single-crystal diffraction analyses indicate that four azo dyes have severely twisted aminoazobenzene structures because of the steric hindrance of ortho dichloro/dibromo radicals of 4-nitrobenzene moiety, while the other four dyes show essentially planar conformation due to the ortho monosubstituted 4-nitrobenzene amine and 4′-amino-azobenzene units. It is noted that the electronic spectra are closely related to their molecular structures, where the presence of different auxochrome groups and the spatial crowding effects in the aminoazobenzene backbone lead to significant alterations of the bathochromic and hypsochromic shifts. [ABSTRACT FROM AUTHOR]

The compound 9-p-tolyl-9H-carbazole-3-carbaldehyde (HCCD) was synthesized and characterized by X-ray diffraction, FT-IR, FT-Raman and UV–Vis spectra. The X-ray diffraction study showed that HCCD has a Z-configuration. The benzene ring including methyl is twisted from the mean plane of the carbazole group by 59.7(3)°, which is comparable with the calculated result 65° for B3LYP/6-311++G(d, p) method. Vibrational spectra and electronic spectra measurements were made for the compound. Optimized geometrical structure and harmonic vibrational frequencies were computed with B-based DFT (BLYP, B3LYP and cam-B3LYP) methods, and WB-based DFT (WB97, WB97X and WB97XD) methods and ab initio RHF method using 6-311++G(d, p) basis set. Assignments of the observed spectra were proposed. The equilibrium geometries computed by all of the methods were compared with X-ray diffraction results. The absorption spectra of the title compound were computed both in gas phase and in DMF solution using TD-(cam)B3LYP/6-311++G(d, p) and PCM-(cam)B3LYP/6-311++G(d, p) approaches, respectively. The calculated results provide good descriptions of the bands maxima in the observed electronic spectrum. Temperature dependence of thermodynamic parameters in the range of 100–1000 K was determined. The natural atomic hybrids were calculated and discussed. [ABSTRACT FROM AUTHOR]

In the present work, the characterization of 4-Amino-3-phenyl-1H-1,2,4-triazole-5(4H)-thione (APTT) molecule was carried out by quantum chemical method and vibrational spectral techniques. The FT-IR (4000–400 cm −1 ) and FT-Raman (4000–100 cm −1 ) spectra of APTT were recorded in solid phase. The UV–Vis absorption spectrum of the APTT was recorded in the range of 200–400 nm. The molecular geometry, harmonic vibrational frequencies and bonding features of APTT in the ground state have been calculated by HF and DFT methods using 6-311++G(d,p) basis set. The complete vibrational frequency assignments were made by normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMF). The molecular stability and bond strength were investigated by applying the natural bond orbital analysis (NBO) and natural localized molecular orbital (NLMO) analysis. The electronic properties, such as excitation energies, absorption wavelength, HOMO and LUMO energies were performed by time depended DFT (TD-DFT) approach. The 1 H and 13 C nuclear magnetic resonance chemical shift of the molecule were calculated using the gauge-including atomic orbital (GIAO) method and compared with experimental results. Finally, the calculation results were analyzed to simulate infrared, FT-Raman and UV spectra of the title compound which shows better agreement with observed spectra. [ABSTRACT FROM AUTHOR]

Highlights: [•] Dye is used to study the onset of micellisation and probing the homomicellar phase. [•] Dipolarity–polarisability, H-bond donation ability of micellar phase is estimated. [•] In catanionic vesicle the dye distributes itself between two regions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Geometric structures of clusters 4AP-(H2O) n (n =1–7) in states S0 and S1 were optimized. [•] In S1 state, A-type hydrogen bond is weakened whereas B- and C-type hydrogen bonds are strengthened. [•] Weakening of A causes blueshifts of absorption and infrared spectra. [•] Strengthening of B and C leads to redshifts of electronic and infrared spectra. [ABSTRACT FROM AUTHOR]

Highlights: [•] Experimental spectra in the mid- and near-IR and DFT calculations for the vibrational and electronic spectra are reported. [•] Good agreement between theory and experiment for the vibrational frequencies of the neutral species. [•] The intensity of the 1440cm−1 band grows with molecular size. [•] B3LYP fails for ions, BP86 is in reasonable agreement with experiment. [•] The large molecules show electronic transitions in the mid-IR and theory gives insight into these transitions. [Copyright &y& Elsevier]