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Luminescent diimine-Pt(IV) complexes [Pt(N^N)(Me)2(PhSe)2], (N^N = 2,2′-bipyridine (bpy, 1b), 1,10-phenanthroline (phen, 2b), and 4,4′-dimethyl-2,2′-bipyridine (Me2bpy, 3b), PhSe− = phenyl selenide were prepared and identified using multinuclear (1H, 13C{1H} and 77Se{1H}) NMR spectroscopy. The PhSe− ligands were introduced through oxidative addition of diphenyl diselenide to the non-luminescent Pt(II) precursors [Pt(N^N)(Me)2], N^N = (bpy, 1a), (phen, 2a), (Me2bpy, 3a), to give the luminescent Pt(IV) complexes 1b–3b. The UV-vis absorption spectra of 1b–3b are characterised by intense bands in the range 240–330 nm. We assigned them to transitions of essentially π−π* character with small metal and PhSe− ligand contributions with the help of TD-DFT (time-dependent density functional theory) calculations. The weak long-wavelength bands in the range 350–475 nm are of mixed ligand-to-metal charge transfer (L'MCT) (n(Se)→d(Pt)/intra-ligand charge transfer (IL'CT) (n(Se)→π*(Ph) or π(Ph)→π*(Ph))/ligand-to-ligand' charge transfer (LL'CT) (L = N^N, L' = PhSe−, M = Pt and n = lone pair) character. The Pt(IV) complexes showed broad emission bands in the solid state at 298 and 77 K, peaking at 560–595 nm with a blue shift upon cooling. Structured emission bands were obtained in the range 450–600 nm, with the maxima depending on the N^N ligands and the solvent polarity (CH2Cl2 vs. dimethyl sulfoxide (DMSO) and aqueous tris(hydroxymethyl)aminomethane hydrochloride (tris-HCl) buffer). The emissions originate from essentially ligand-centred triplet states (3LC) with mixed IL'CT/L'MCT contributions as concluded from the DFT calculation. Such dominating PhSe contributions to the emissive states are unprecedented in the world of luminescent diimine-Pt(IV) complexes. [ABSTRACT FROM AUTHOR]

[Display omitted] • 1,4-bis(4-vinylpyridyl)benzene (bvpb), a double heterostilbene, was synthesized and characterized. • Electrochemical Surface-Enhanced Raman Spectra (SERS) of bvpb put in evidence a resonance process at −1.0 V with 785 nm excitation line. • The study of dynamic relaxation processes by femtosecond Transient Absorption Spectra (TAS) shows a first excited state (S 1) at 607 nm in which a trans–cis rotation of the vinyl bond is involved. • DFT potential energy curve of vinyl torsion predicts a low barrier height between trans- and cis -conformers in S 1 state with a S 1 /S 0 conical intersection corresponding to a twisted vinylpyridyl bond. • The synergy of experimental data, SERS and TAS, and DFT calculations shows bvpb can act as a conformational molecular switch addressed by electric potential under a selected wavelength. The electrochemical surface-enhanced Raman spectra (SERS) of 1,4-bis(4-vinylpyridyl)benzene (bvpb) recorded at different electrode potentials with three excitation wavelengths (785, 532 and 473 nm) point out there exists a resonance process involved at more negative voltage with the 785 nm line, giving two strongly enhanced SERS bands at about 1500 and 1150 cm−1. This result agrees with the VIS-NIR transient absorption spectrum characterized by a strong band at 607 nm and a weaker one at 1163 nm, corresponding to the first singlet (S 1) and triplet (T 1) excited electronic states. The DFT potential energy curve corresponding to the trans – cis (E-Z) isomerization in the S 0 state and in the two lowest S 1 and T 1 excited states, indicates that the S 1 state exhibits a significant lower barrier height than S 0 state, showing also a S 1 /S 0 conical intersection at a structural conformation in which the vinyl double bond twists by 90°. TD-DFT resonance Raman spectra of the planar and twisted conformation in a simple model of surface complex, Ag 2 0-bvpb, yield that the twisted molecule is able to predict the selected enhancement of the two SERS bands. Therefore, bvpb could act as an electroactive conformational molecular switch under a selected wavelength in nanoelectronic devices. [ABSTRACT FROM AUTHOR]

Wavelength‐independent conversion of organic photoswitches in the photostationary state is a rare phenomenon that opens up a way for many practical applications. In this work, three fused bis(hemi‐indigo) derivatives with different substitution patterns were synthesized and their photoswitching was investigated by optical spectroscopy, real‐time NMR spectroscopy and TD‐DFT calculations. We disclosed that the Z‐E photoisomerization of the meta‐bis(hemi‐indigo) derivative was remarkably independent of the irradiation wavelength from UV up to yellow light. The wavelength‐independent forward photoswitching together with the inhibited backward photoisomerization, high thermal stability of the photoinduced isomers as well as significant overlap between the photoswitch absorption and the solar spectrum allows to suggest bis(hemi‐indigo) derivatives as promising candidates for molecular solar thermal energy storage (MOST) systems. [ABSTRACT FROM AUTHOR]

A set of donor‐acceptor (D‐A) substituted phenothiazine based chromophores (D‐π‐D‐π‐A, D′‐π‐D‐π‐A, D‐A′‐D‐π‐A and D′‐A′‐D‐π‐A) were designed and synthesized. The phenothiazine was substituted with the 4‐ethynyl‐1,8‐naphthalimide (NPI) on one side and a variety of donors (phenothiazine, carbazole, ferrocene and triphenylamine) were introduced on the other side of phenothiazine via Pd‐catalyzed Sonogashira cross‐coupling reaction resulting PTZ8–11. In order to tune the optoelectronic properties of the phenothiazine chromophores, cyano‐based acceptor 1,1,4,4‐tetracyanobuta‐1,3‐diene (TCBD) was incorporated by [2+2] cycloaddition‐electrocyclic ring‐opening reaction of phenothiazine derivatives PTZs 8–11 and tetracyanoethylene (TCNE). The photophysical and electrochemical studies showed that the incorporation of TCBD acceptor in the phenothiazine chromophores PTZs 12–15 facilitated the donor‐acceptor strength to greater extent. The electronic absorption spectra exhibited red shifted absorption bands for the TCBD substituted phenothiazines as compared to the alkynylated phenothiazines which led to much lower optical band gaps in the formers. The experimental values were also supported by the DFT and TD‐DFT calculations. [ABSTRACT FROM AUTHOR]

The time‐dependent density functional theory was used to calculate the vibronic absorption spectrum of berberine (BER) in an aqueous solution. The best agreement with the experimental spectrum gives the O3LYP functional. Functionals with long‐range correction showed poor agreement with experiment. The molecular orbitals of BER involved in the electronic transition during light absorption in the visible spectral region have been obtained. The dipole moments and atomic charges of the ground and excited states of the BER molecule have been calculated. Maps of BER electron density and electrostatic potential have been drawn. A significant photoinduced electron transfer from the outer di‐oxygen five‐membered heterocycle to the center of the BER chromophore has been found. According to our calculations, vibronic coupling and Boltzmann distribution play a significant role in the absorption spectrum of BER. [ABSTRACT FROM AUTHOR]

For the first time the nonlinear optical (NLO) activity of indolizine-based push-pull chromophores with different acceptor moieties was studied and compared. All the chromophores demonstrate strong absorption band in the visible (orange-red) part of the spectrum, with ε of ca. 10 5 L∙cm −1 ∙M −1 notably dependent on medium polarity. Replacement of Ph-TCF acceptor by Hex-TCP one results in twofold increase of the first hyperpolarizability value. Energy gaps estimated by electrochemical methods decrease in the series ΔE 1a,b >ΔE 3a,b >ΔE 2a,b for compounds with Ph-TCF, DCM and Hex-TCP acceptors, respectively, good agreement with DFT estimations is obtained. The nonlinear optical coefficient for poled PMMA-based films, containing 20 wt% of isomeric indolizine chromophores with weaker dicyanomethylene (DCM) acceptor and with π- bridge expanded by isophorone moiety, achieves 36 pm/V, thus exceeding those for materials containing chromophores with stronger Ph-TCF or Hex-TCP acceptors and with short vinylene π-bridge. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) approaches were applied to explore the effect of central transition metals and the dye/TiO 2 interface on dye-sensitized solar cell (DSSC) performance and supply a promising way to estimate and screen possible candidates for DSSC applications. The interaction properties, bonding characteristics, sensitized mechanisms, charge transfer, frontier molecular orbitals, energy gap, partial densities of states (PDOS), non-covalent interactions (NCI), and electronic absorption spectra were examined and analyzed to provide the photovoltaic characteristics of Sc, Cu, and Ti tetrasulfonic acid phthalocyanine sensitizer@TiO 2 interface in both gas phase and polar solvent as acetonitrile. The interfacial of TiPc-(SO 3 H) 4 with TiO 2 , which facilitates the driving force for the electron injection of photosensitizers ( Δ G inj ) , increases the charge separation, open-circuit voltage (V oc), and high light-harvesting efficiency (LHE) values. However, minimize the charge recombination, lifetime of the excited state (τ), regeneration driving force ( Δ G reg). Our results reveal that TiPc-(SO 3 H) 4 @TiO 2 is superior to those of ScPc-(SO 3 H) 4 , CuPc-(SO 3 H) 4 , TiPc-(SO 3 H) 4 and Pc-(SO 3 H) 4 /TiO 2 , indicating the novel TiPc-(SO 3 H) 4 @TiO 2 interface could be promising candidates for DSSC photovoltaic devices performance. In addition, the static mean polarizability and first hyperpolarizability of all six dyes elucidated that the TiPc-(SO 3 H) 4 @TiO 2 interface can be regarded as a potential performer in non-linear optical (NLO) properties. These theoretical identifications may provide novel perspectives and instructions for future experimental researchers to promote the synthesis and application of TiPc-(SO 3 H) 4 @TiO 2 interfaces to improve the photo-to-current conversion efficiency. [Display omitted] • The studied dyes showed a good performance of Δ G inj , V OC , J SC and dye regeneration. • TiPc-(SO 3 H) 4 /TiO 2 with the longest τ showed the most prominent charge transfer efficiency. • The reported dye interfaces illustrated red-shift absorption spectra and high IPCE. • TiPc-(SO 3 H) 4 /TiO 2 is expected as the promising candidates with a superior performance. • The solvent effects were investigated for all the studied dyes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The drug-loading capacity for anticancer 5FU drug at Fe 6 @B 40 was investigated. • (5FU) 6 @[Fe 6 @B 40 ] has a high capacity for delivering of multiple 5FU molecules. • The 5FU can be separated from Fe 4 @B 40 and Fe 6 @B 40 at ambient temperature. • The solvent effects of 5FU at M@B 40 nanocages (M = Na, Mg and Fe) were examined. • NBO, PDOS, NCI, AIM, ELF and NLO of have been analysed. The potential of exohedral metalloborospherene (Na@B 40 , Mg@B 40 , Fe@B 40 , Fe 4 @B 40 and Fe 6 @B 40) for delivery of anti-cancer 5-fluorouracil (5FU) have been investigated using DFT calculations. The NBO analysis, statistical thermodynamics, PDOS characteristics, NCI and QTAIM descriptors of these systems were investigated to analyze the interaction process. UV–visible electronic absorption spectra in the gas and aqueous phases were simulated using TD-DFT calculations. In addition, to examine the drug-loading capacity and biocompatibility, up to six 5FU molecules can be attached to Fe 6 @B 40. The solvent effects tend to lower the 5FU adsorption energies to be easily released from nanocages. The greater polarizability and first hyperpolarizability of the 5FU@[Mg@B 40 ], (5FU) 4 @[Fe 4 @B 40 ] and (5FU) 6 @[Fe 6 @B 40 ] systems imply their applications in photonic and extremely effective to improve the NLO performance. These theoretical identifications can provide new insights and guidelines for the future experimental researchers to promote the synthesis and application of metalloborospherenes (Fe 4 @B 40 and Fe 6 @B 40) in drug-loading capacity. [ABSTRACT FROM AUTHOR]

The electronic structure, chemical bonding, and excitation spectra of neutral, cationic, and anionic diatomic molecules of Cu and 14 group elements formulated as [CuE]+/0/− (E = C, Si, Ge, Sn, Pb) were investigated by density functional theory (DFT) and time-dependent (TD)-DFT methods. The electronic and bonding properties of the diatomics analyzed by natural bond orbital (NBO) analysis approch revealed a clear picture of the chemical bonding in these species. The spatial organization of the bonding between Cu and E atoms in the [CuE]+/0/− (E = Si, Ge, Sn, Pb) molecules can easily be recognized by the cut-plane electron localization function representations. Particular emphasis was given on the absorption spectra of the [CuE]+/0/− which were simulated using the results of TD-DFT calculations employing the hybrid Coulomb-attenuating CAM-B3LYP functional. The absorption bands have thoroughly been analyzed and assignments of the contributing principal electronic transitions associated to individual excitations have been made. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Vertical electronic transitions to singlet valence states of an antipsychotic drug, Risperidone (Risperdal), in its neutral, mono-, and diprotonated forms have been calculated within the time-dependent density functional theory using the PBE0 hybrid functional with the 6-31+G basis set. The results of the computations show that the lowest-energy allowed π-π electronic excitation is affected by protonation effects, the spectral shifts of this transition being potentially useful to individuate the different forms of risperidone [ABSTRACT FROM AUTHOR]

Abstract: The electronic structure of the 1,4-bis(pyrrol-2-ylmethyleneamino)butane nickel(II) complex has been studied using electronic absorption spectroscopy and density functional theory (DFT) calculations. The DFT optimised structure is in excellent agreement with the X-ray crystal structure of the complex and time-dependent DFT calculations have been used to probe the nature of the transitions observed in the electronic absorption spectrum. [Copyright &y& Elsevier]

Abstract: The complexes of the general formulae [Ru(terpy)(dcbpy)X] q (dcbpy=4,4′-dicarboxy-2,2′-bipyridine; X=Cl−, 1; NO+, 2; , 3; q =1+, 3+ and 1−, respectively) have been synthesized and characterized. The DNA binding properties of structurally similar complexes [Ru(terpy)(dcbpy)NO2]−, 3, [Ru(terpy)(4-CO2-4′-Mebpy)NO2], 4, and [Ru(terpy)(bpy)NO2]+, 5, were studied, and their DNA affinities (K b) were calculated as 6±0.3×104 M−1, 8±1.1×104 M−1 and 9.7±0.02×106 M−1. The structural and spectroscopic properties of complexes 3–5 were investigated by DFT and TD DFT electronic structure calculations. The equilibrium geometries of complexes 3–5 in vacuum correspond to a distorted octahedral stereochemistry. The high-lying peaks of the absorption spectra of the complexes, ranging from 440 to 529nm, are assigned to MLCT/LLCT transitions. These transitions are red-shifted upon adding carboxy substituents to the bipyridine ligand while the low-lying LLCT transitions, absorbing at 779 and 659nm, are blue-shifted. Noteworthy is the excellent agreement of the TD DFT simulated absorption spectra in aqueous solution with the experimental ones. [Copyright &y& Elsevier]

Time-dependent density functional theory (TD-DFT) calculations were carried out in a comparative study of the electronic absorption spectra of lead(II) phthalocyaninate (PbPc), tin(II) phthalocyaninate (SnPc), tin(IV) dichlorophalocyaninate (PcSnCl2), germanium(II) phthalocyaninate (GePc), and germanium (IV) dichlorophalocyaninate (PcGeCl2) with the B3LYP method and LANL2DZ basis set. Our calculated bands correspond well with the experimental results. The electronic natures of all the bands in the absorption spectra are assigned and analyzed comparatively according to the calculated electronic transition contributions. With the increase of the dielectric constant from CHCl3 to DMSO, all the electronic absorption bands are somewhat red shift, consistent with the shift rules measured experimentally. The radius of the central metals has great influence to the absorption spectra, especially for the B bands. The influence of the radius of the central metals to the absorption spectra of PcSnCl2 and PcGeCl2 is smaller than to the spectra of the nonplanar MPcs (M = Pb, Sn, and Ge). Axial ligands also greatly changed the electronic absorption spectra due to the change of the orbital energy level and the molecular symmetry. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [ABSTRACT FROM AUTHOR]

Silicon-inserted triazacorrole, its μ-oxo dimer, and tetrabenzotriazacorrole have been obtained by ring contraction when metal-free tetraazaporphyrin (TAP) and phthalocyanine (Pc), respectively, were reacted with trichlorohydrosilane (HSiCl3) in the presence of tributylamine in refluxing benzene. The triazacorrole has very sharp absorption at ca. 400 nm, which is suitable for blue-laser applications. [Copyright &y& Elsevier]

The drastic differences in absorption spectra of structurally close quinoxalinone derivatives, containing electron-donor and -acceptor units, are rationalized, by means of theoretical tools. They are ascribed to the difference in the intramolecular charge-transfer character of the electronic transition corresponding to the experimental longest-wavelength absorption bands of these systems. Charge-transfer compounds are not luminescent in solutions, in contrast to their analogs with weaker charge-separation and longer π-conjugated backbone, which suggests that the main factor "switching-off" emission is related to their "push-pull" properties and the balance between the length of the π-conjugated backbone and the donor-acceptor strength. Furthermore, the protonation of the studied quinoxalinones is shown to result in a weakening of the donor-acceptor strengths and conjugation efficiency, thus limiting charge-transfer and producing the emission response in the acidified solutions. • The drastic differences in absorption spectra of structurally close quinoxalin-2-one isomers are theoretically rationalized. • The difference of ICT character of electronic excitations strongly influences the absorption spectra intensities. • The balance between the π-conjugation length and the D-π-A strength allows to fine-tune of electronic spectral properties. • The protonation results in weakening of the D-π-A strengths and conjugation efficiency decreasing CT and raising the emission. • ab initio molecular dynamics revealed a formation of strong ion pairs with the added acid affecting the spectral properties. [ABSTRACT FROM AUTHOR]