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Developing effective strategies to improve the hydrophilicity or aqueous solubility of hydrophobic molecular scaffolds is meaningful for both academic research and industrial applications. Herein, we demonstrate that stepwise and precise N/O heteroatoms doping on a polycyclic aromatic skeleton can gradually alter these structures from hydrophobic to hydrophilic, even resulting in excellent aqueous solubility. The Hansen solubility parameters (HSP) method shows that the three partial solubility parameters are closely related to N/O doping species, numbers and positions on the molecular panel. The hydrogen bonding solubility parameter indicates that the hydrogen bonding interactions between N/O doped molecules and water play a key role in enhancing hydrophilicity. Moreover, three optimized water-soluble molecules underwent a self-assembly process to form stable nanoparticles in water, thus facilitating better hydrogen bonding interactions disclosed by HSP calculations, NMR and single crystal X-ray analysis. These ensembles even show quasi-solid properties in water from NMR and luminescence perspectives. Enhancing the hydrophilicity of hydrophobic molecular scaffolds allows to increase their aqueous solubility and therefore their usability for a range of applications. Here, N/O heteroatom doping of polycyclic aromatic hydrocarbons is shown to switch the skeleton from hydrophobic to hydrophilic, enhancing aqueous solubility and facilitating self-assembly in water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen removal efficiencies by zeolite wetland was better than ceramists and lava. • Selective inhibition of amo B and hao gene abundance on different substrates. • Denitrification is a key pathway for nitrate removal in constructed wetland (CW) • Dissimilatory nitrate reduction process was enhanced in CW- zeolite. This study conducted an analysis of the variations in nitrogen metabolism pathways within constructed wetlands (CWs) using zeolite (CW-Z), ceramsite (CW-C), and lava (CW-L) under high concentration sulfamethoxazole (SMX) stress. The introduction of SMX hindered the formation of hydrogen bonds on the substrate surfaces; however, these surfaces still maintained a dense and thick biofilm. CW-Z exhibited superior removal efficiencies for ammonium nitrogen (NH 4 +-N) and nitrate nitrogen (NO 3 –-N) compared to CW-C and CW-L, with removal rates of 92.54 ± 2.88 % and 89.39 ± 6.74 %, respectively. Interestingly, the proportion of genes involved in nitrification, denitrification and nitrate reduction genes in CW-C (36.05 %) were higher than that in CW-C (29.81 %) and CW-L (29.70 %) but the interactions among nitrogen functional bacteria in CW-Z were much more complex. Further analysis of the nitrogen metabolism pathway indicated that under CW-Z enhanced dissimilatory nitrate reduction SMX stress, while CW-L enhanced assimilatory nitrate reduction process compared to CW-C. [ABSTRACT FROM AUTHOR]

A comparison about excited state intramolecular proton transfer (ESIPT) mechanism of a new sensor 3-(1,3-benzothiazol-2-yl)-2-hydroxynaphthalene-1-carbaldehyde ( 3BHC) in polar solvent dimethylformamide (DMF) and nonpolar solvent toluene have been investigated within the framework of the time-dependent density functional theory (TD-DFT) method. The reproduced previous experimental absorption and emission spectra via our calculations reveals the reasonability of the DFT and TD-DFT theoretical level. The staple bond lengths, bond angles, and corresponding infrared vibrational spectra demonstrate that the intramolecular hydrogen bond of 3BHC should be strengthened in both polar DMF and nonpolar toluene. Two kinds of ESIPT mechanisms for different solvents have been put forward; there is a low potential barrier in the ESIPT process in the DMF solvent, whereas there is almost a nonbarrier for the ESIPT process in the toluene solvent. Hence, we could conclude that the ESIPT process of 3BHC sensor is more likely to occur in the nonpolar solvent upon the photoexcitation, based on which, the excited state behavior of 3BHC could be controlled. [ABSTRACT FROM AUTHOR]

Ternary hydrogels composed of poly[acrylamide- co -2-(dimethylamino)ethyl methacrylate] [P(AM- co -DMAEMA)], poly(vinyl alcohol) (PVA) and β -cyclodextrin ( β -CD) were fabricated based on the multiple physical interactions such as inclusion complexation, hydrogen bonding and polymer crystallinity, and exhibited high storage modulus. To illustrate the individual role of each physical interaction, symmetrical investigation has been performed. P(AM- co -DMAEMA)s with two compositions, prepared by radical polymerization at −20 °C below the freezing point of reaction medium of water, were served as the inclusion guest for the inclusion host of β -CD. The inclusion complex between dimethylaminoethyl group of DMAEMA and β -CD was identified through 2D NOESY NMR spectroscopy. Hydrogen bonding between each pairs of hydrogel components was confirmed with FTIR analysis and contributed the second form of crosslinkage. Under freezing polymerization and further freezing-thawing treatment, PVA component tended to crystallize to serve as the third type of physical crosslinkage, which was recognized with X-ray diffraction. Rheological and thermo-gravimetrical analysis was used to inspect the modulus and thermal stability of the hydrogels, respectively. Three hydrogels of P(AM- co -DMAEMA)/PVA-g- β -CD, P(AM- co -DMAEMA)/PVA/ β -CD and P(AM- co -DMAEMA)/PVA were synthesized under the same condition to make the comparison. The whole results disclosed the strong dependence of hydrogel properties on the hydrogel components, reflecting the synergistic effects of different physical crosslinkages for the formation of those physical hydrogels. [ABSTRACT FROM AUTHOR]

[Display omitted] • The enhanced hydrogen bonding provides the impetus to promote the ESIPT reaction. • Photo-induced increased electronic densities around O 14 atom plays vital roles in attracting hydroxyl proton. • Atomic electronegativity could be more favorable for the ESIPT behavior of 4M3HF system. In view of the potential applications via regulating excited state behaviors, in this work, excited state dynamics of 4-methoxy-3-hydroxyflavone (4M3HF) with different atomic electronegativities (i.e., 4M3HF-O, 4M3HF-S and 4M3HF-Se) are explored theoretically. Dominating chemical parameters, infrared (IR) spectra, and bond critical point (BCP) analyses reveal hydrogen bond could be enhanced in S 1 state. Via light-induced excitation, by comparing the energy gaps of frontier molecular orbitals (MOs) and charge recombination, we find low atomic electronegativity promotes ESIPT reaction. Insights into potential energy curves (PECs) and transition state (TS) forms, we present low atomic electronegativity facilitates ESIPT behavior for 4M3HF system. [ABSTRACT FROM AUTHOR]

Abstract: A new cobalt complex, [Co(L)2·(H2O)2](HL = 4-hexanoyl-3-methyl-1-phenyl-1H -pyrazol-5(4H)-one), was synthesized by us. The complex was characterized by single crystal X-ray diffraction, IR, UV, fluorescence spectra and thermogravimetric analysis. The results of characterization showed that the crystal is monoclinic system with crystal parameters: a =15.2439(12)Å, b =7.4101(6)Å, c =15.7381(18)Å, and Z =2, S =1.074. It was found that the Co2+ is located in the inversion center of the complex. The Co(II) had an ideal octahedral coordination environment with four oxygen atoms of HL ligands in the equatorial plane and two water molecules in axial positions. The complex exhibits yellow emission as the result of the fluorescence from the intraligand emission excited state. [Copyright &y& Elsevier]

The excited-state intramolecular proton transfer (ESIPT) reaction in 1-hydroxy-11H-benzo[b]fluoren-11-one (HBF) is found to be highly sensitive to the presence of specific substituents in positions C2, C4 and C8 with respect to the hydroxyl group, leading to different fluorescent behaviors of HBF with different substituents (J. Phys. Chem. C, 2018, 122, 21833). However, a systematic and comprehensive computational study of the influence of alkyl-substitutions at various positions of HBF on the intramolecular hydrogen bond strength, adsorption and fluorescence spectra and finally the proton transfer energy barriers is scare up to now. Therefore, in this work, the excited-state overall perspective of the proton transfer process of HBF and its seven tert -butyl substituted derivatives (Scheme 1) have been theoretically studied at TD-PBE0/TZVP theory level with the DFT and TDDFT methods. It is concluded that alkyl-substitution at positions C2 and C4 of the parent molecule should increase the strength of intramolecular hydrogen bonding O 1 -H⋯O, which decrease both the S 1 -state forward proton transfer energy barriers and the energy differences between forms S 1-PT and S 1 and eventually facilitate the ESIPT process, whereas alkyl-substitution at position C8 of the parent molecule should have slight opposite effect. • Alkyl-substitution at positions C2 and C4 increase the hydrogen bonding strength of O 1 -H⋯O. • Strengthened O 1 -H⋯O decreases the S 1 -state forward proton transfer energy barrier and facilitates the ESIPT process. • Alkyl-substitution at position C8 of the parent molecule has slight negative effect on the ESIPT process. • Balance between acidity of proton and basicity of proton donor and proton accepter subtly tunes the ESIPT equilibrium. [ABSTRACT FROM AUTHOR]

In this work, based on density functional theory (DFT) and time‐dependent DFT (TDDFT) methods, we theoretically explore the excited state behavior for a novel dye molecule 3,3′‐(5,5′‐((1E,1E′)‐hydrazine‐1,2‐diylidenebis (methanylylidene))bis(2‐morpholinothiazole‐5,4‐diyl))bis(4‐hydroxy‐2H‐chromen‐2‐one) (CS‐Azine). Coupling with atoms in molecules, we investigate the intramolecular dual hydrogen bonds of CS‐Azine system and verify the formation of them. Via study the primary bond distances, bond angle, and infrared vibrational spectra involved in hydrogen bonding moieties, we find O1‐H2···N3 and O4‐H5···N6 of CS‐Azine should be strengthened in the S1 state. When exploring the photo‐excitation process, we confirm that the charge redistribution around hydrogen bonding moieties reveals the tendency of ESIPT reaction. To further investigate whether single or double proton transfer occurs in the S1 state, we consider two kinds of reaction paths (ie, the stepwise and synergetic ESIPT reactions). And the constructed potential energy curves demonstrate that only the single proton transfer reaction should be the most supported in the S1 state from CS‐Azine to CS‐Azine‐SPT form due to the low potential energy barrier. This work not only clarifies the excited state behavior and mechanism about CS‐Azine system but also paves the way for further applying CS‐Azine dye in future. Highlights: Although two hydrogen bonds exist for CS‐Azine system, only the single proton transfer reaction should be the most supported one in the S1 state. [ABSTRACT FROM AUTHOR]

Abstract A novel fluorescence molecule (2‑hydroxy‑4‑methoxyphenyl)(phenyl)‑methanone azine (HMPM) has been explored theoretically in this present work. Based on density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, we investigate the excited state hydrogen bonding behaviors and excite state intramolecular proton transfer (ESIPT) process for HMPM molecule. Via simulating the reduced density gradient (RDG) versus sign(λ 2)ρ, we firstly verify the double intramolecular hydrogen bonds (O1 H2⋯N3 and O4 H5⋯N6) for HMPM system. Comparing with the changes about these two hydrogen bonds (i.e., bond distances, bond angles and infrared (IR) vibrational spectra), we find that they should be enhanced in the first excited state upon the photo-excitation. The shortened hydrogen bonding distance of H2⋯N3 and H5⋯N6 provide the possibility for ESIPT reaction. Given the photo-excitation process, we confirm the charge redistribution around the hydrogen bonding moieties plays an important role as a driving force for the ESIPT process. Further, via constructing S 0 -state and S 1 -state potential energy surfaces (PESs), we confirm the excited state double proton transfer (ESDPT) is excludable since the high optimized energy and high potential energy barrier. While the low potential barrier for excited state single proton transfer path results in the ultrafast ESIPT reaction, which explains why the initial HMPM fluorescence peak cannot be detected in previous experimental phenomenon. This work not only clarifies the excited state dynamical behavior for HMPM system, but also explains previous experimental phenomenon and attributions about steady state spectra. We hope this work can facilitate novel applications based on the novel HMPM system in future. Graphical Abstract Unlabelled Image Highlights • Hydrogen bond of HMPM should be strengthened in the first excited state. • Charge transfer facilitates the ESIPT process for HMPM molecule. • Only the excited state single proton transfer process occurs for HMPM molecule. [ABSTRACT FROM AUTHOR]

In this work, density functional theory (DFT) and time‐dependent density functional theory (TDDFT) methods are used to explore the excited‐state intramolecular proton transfer (ESIPT) mechanism of a novel system 4′‐dimethylaminoflavonol (DAF). By analyzing the molecular electrostatic potential (MEP) surface, we verify that the intramolecular hydrogen bond in DAF exists in both the S0 and S1 states. We calculate the absorption and emission spectra of DAF in two solvents, which reproduce the experimental results. By comparing the bond lengths, bond angles, and relative infrared (IR) vibrational spectra involved in the hydrogen bonding of DAF, we confirm the hydrogen‐bond strengthening in the S1 state. For further exploring the photoexcitation, we use frontier molecular orbitals to analyze the charge redistribution properties, which indicate that the charge transfer in the hydrogen‐bond moiety may be facilitating the ESIPT process. The constructed potential energy curves in acetonitrile and methylcyclohexane solvents with shortened hydrogen bond distances demonstrate that proton transfer is more likely to occur in the S1 state due to the lower potential barrier. Comparing the results in the two solvents, we find that aprotic polar and nonpolar solvents seem to play similar roles. This work not only clarifies the excited‐state behaviors of the DAF system but also successfully explains its spectral characteristics. Hydrogen bond should be formed in the S0 state for 4′‐dimethylaminoflavonol (DAF), as shown via Atoms in Molecules (AIM) analysis. The intramolecular hydrogen bond of DAF should be strengthened in the S1 state, which provides the tendency for the excited‐state intramolecular proton transfer (ESIPT) reaction. The charge redistribution and low potential energy barriers of DAF facilitate the ESIPT reaction. [ABSTRACT FROM AUTHOR]

In this work, density functional theory (DFT) and time‐dependent DFT (TDDFT) methods were used to investigate the excited‐state dynamics of the excited‐state hydrogen‐bonding variations and proton transfer mechanism for a novel white‐light fluorophore 2‐(4‐[dimethylamino]phenyl)‐7‐hyroxy‐6‐(3‐phenylpropanoyl)‐4H‐chromen‐4‐one (1). The methods we adopted could successfully reproduce the experimental electronic spectra, which shows the appropriateness of the theoretical level in this work. Using molecular electrostatic potential (MEP) as well as the reduced density gradient (RDG) versus the product of the sign of the second largest eigenvalue of the electron density Hessian matrix and electron density (sign[λ2]ρ), we demonstrate that an intramolecular hydrogen bond O1–H2···O3 should be formed spontaneously in the S0 state. By analyzing the chemical structures, infrared vibrational spectra, and hydrogen‐bonding energies, we confirm that O1–H2·O3 should be strengthened in the S1 state, which reveals the possibility of an excited‐state intramolecular proton transfer (ESIPT) process. On investigating the excitation process, we find the S0 → S1 transition corresponding to the charge transfer, which provides the driving force for ESIPT. By constructing the potential energy curves, we show that the ESIPT reaction results in a dynamic equilibrium in the S1 state between the forward and backward processes, which facilitates the emission of white light. Highlights: The excited state dynamical equilibrium in ESIPT process of 1 compound facilitates mingling white light emitting. [ABSTRACT FROM AUTHOR]

A novel aggregation-induced emission material 2-(5-(4-carboxyphenyl)-2-hydroxyphenyl)benzothiazole (2-CHBT) has been investigated based on density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. Via reduced density gradient (RDG) versus sign(λ2)ρ analyses, we firstly verify the formation of intramolecular hydrogen bond in 2-CHBT system. Analyzing the primary geometrical parameters in 2-CHBT and comparing the changes about infrared (IR) vibrational spectra, we confirm that the hydrogen bond O-H···N is strengthened in the S1 state upon excitation. Exploring photo-excitation process, the frontier molecular orbitals (MOs) and charge density difference (CDD) analyses have been performed using TDDFT/B3LYP/TZVP theoretical level, based on which we verify the charge transfer phenomenon referring to the S0 → S1 transition. And the CDD around the hydrogen bond moiety provides the tendency of ESIPT for 2-CHBT molecule. Comparing the energy gap between HOMO and LUMO orbitals in cyclohexane, toluene, chloroform, and DMSO solvents, we predict the ESIPT reaction might be more active in non-polar solvents. In addition, constructing potential energy curves and searching transition state (TS) structures, we further clarify the ESIPT mechanism and verify that non-polar solvents might facilitate the ESIPT process. Our simulated results reappear experimental spectral results and successfully explain experimental phenomenon. [ABSTRACT FROM AUTHOR]

A novel 3‐hydroxyflavone derivative, 4‐methoxy‐3‐hydroxyflavone (4M3HF), is theoretically investigated regarding its excited state intramolecular proton transfer (ESIPT) mechanism based on density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. By comparing the solvent polarity, we selected acetonitrile and toluene in this work. First, based on atoms in molecules (AIM) analyses, we verified the formation of intramolecular hydrogen bond of the 4M3HF structure. On investigating the geometrical parameters (i.e., bond lengths and bond angles), we found that the hydrogen bond strength should be enhanced in the S1 state. By calculating the infrared vibrational spectra, we confirmed the strengthening of the intramolecular hydrogen bond in the S1 state. We further studied the excitation process using the frontier molecular orbitals method, based on which we concluded that the charge redistribution in solvents facilitates the ESIPT tendency. For exploring the ESIPT behavior, we constructed the potential energy curves along with ESIPT paths in both solvents (acetonitrile and toluene). We found that low potential energy barriers facilitate the ESIPT process in the 4M3HF system, which was also verified by searching the transition state (TS) structure. Comparing these two solvents, we concluded that solvent effects play little role in the ESIPT reaction in the 4M3HF system. And we could successfully explain the previous experimental result. The intramolecular hydrogen bond of the 4M3HF structure should be strengthened in the S1 state in both acetonitrile and toluene. The charge redistribution of the hydrogen‐bonding moieties of 4M3HF system provides the tendency of ESIPT reaction. By constructing the potential energy curves and searching the TS structures of the 4M3HF system, we clarify the ESIPT mechanism and conclude that the solvent effects play little role in the ESIPT reaction. [ABSTRACT FROM AUTHOR]

In this present work, combing density functional theory (DFT) and time-dependent DFT (TDDFT) methods, we investigate a novel white light material 2,2′-(thiazolo[5,4-d]thiazole-2,5-diyl)bis(4-tert-butylphenol) (t-HTTH) about its dual intramolecular hydrogen bonding behaviors and relative excited state intramolecular proton transfer (ESIPT) process in detail. Via testing functional and basis set, the DFT//TDDFT/MPW1PW91/6–311+G(d,p) theoretical level has been decided in three kinds of solvents (cyclohexane (CYH), dichloromethane (DCM) and toluene (Tol)), which can well reappear experimental phenomenon. Exploring molecular electrostatic potential (MEP), primary bond lengths, bond angles and infrared (IR) vibrational spectra for t-HTTH system in both S 0 and S 1 states, we find the double hydrogen bonds O1-H2···N3 as well as O4-H5···N6 should be strengthened in the S 1 state. Investigating the photo-excitation process, we find that the S 0 → S 1 transition corresponds to charge transfer, which provides the driving force for ESIPT. And analyses about frontier molecular orbitals (MOs) and relative energy gaps between HOMO and LUMO orbitals, we deduced the ESIPT process may occur more likely in nonpolar solvents. Constructing potential energy curves, we reveal that the ESIPT reaction results in the dynamic equilibrium in S 1 state between forward and backward processes, which facilitates white light. We not only clarify the excited state hydrogen bond dynamical behavior of t-HTTH material, but also elaborate the ESIPT mechanism and explain previous experimental phenomenon reasonably. [ABSTRACT FROM AUTHOR]

Abstract: In this present work, using density functional theory and time‐dependent density functional theory methods, we theoretically study the excited‐state hydrogen bonding dynamics and the excited state intramolecular proton transfer mechanism of a new 2‐phenanthro[9,10‐d]oxazol‐2‐yl‐phenol (2PYP) system. Via exploring the reduced density gradient versus sign(λ2(r))ρ(r), we affirm that the intramolecular hydrogen bond O1‐H2⋯N3 is formed in the ground state. Based on photoexcitation, comparing bond lengths, bond angles, and infrared vibrational spectra involved in hydrogen bond, we confirm that the hydrogen bond O1‐H2⋯N3 of 2PYP should be strengthened in the S1 state. Analyses about frontier molecular orbitals prove that charge redistribution of 2PYP facilitates excited state intramolecular proton transfer process. Via constructing potential energy curves and searching transition state structure, we clarify the excited state intramolecular proton transfer mechanism of 2PYP in detail, which may make contributions for the applications of such kinds of system in future. [ABSTRACT FROM AUTHOR]

In the present work, using density functional theory and time-dependent density functional theory methods, we investigated and presented the excited-state intramolecular proton transfer (ESIPT) mechanisms of a novel Compound 1 theoretically. Analyses of electrostatic potential surfaces and reduced density gradient (RDG) versus sign(λ2)ρ, we confirm the existence of intramolecular hydrogen bond O1-H2···N3 for Compound 1 in the S0 state. Comparing the primary structural variations of Compound 1 involved in the intramolecular hydrogen bond, we find that O1-H2···N3 should be strengthened in the S1 state, which may facilitate the ESIPT process. Concomitantly, infrared (IR) vibrational spectra analyses further verify the stability of hydrogen bond. In addition, the role of charge transfer interaction has been addressed under the frontier molecular orbitals, which depicts the nature of electronical excited state and supports the ESIPT reaction. The theoretically scanned and optimized potential energy curves according to variational O1-H2 coordinate demonstrate that the proton transfer process should occur spontaneously in the S1 state. It further explains why the emission peak of Compound 1-enol was not reported in previous experiment. This work not only presents the ESIPT mechanism of Compound 1 but also promotes the understanding of this kind of molecules for further applications in future. [ABSTRACT FROM AUTHOR]

The excited-state intramolecular proton transfer (ESIPT) mechanism of a new compound ( E)-1-((2,2-diphenylhydrazono)methyl)naphthalen-2-ol ( EDMN) sensor, reported and synthesized by Mukherjee et al. [ Sensors Actuat. B-Chem. 2014, 202, 1190], is investigated in detail theoretically. The calculations on primary bond lengths, bond angles, and the corresponding infrared (IR) vibrational spectra and hydrogen-bond energy involved in intramolecular hydrogen bond between the S0 and S1 states confirm that the intramolecular hydrogen bond is strengthened in the S1 state, which reveals the tendency of ESIPT reaction. The fact that the experimental absorption and emission spectra are well reproduced demonstrates the rationality and effectiveness of the time-dependent density functional theory (TDDFT) level of theory we adopt here. Furthermore, intramolecular charge transfer based on the frontier molecular orbitals (MOs) gives indication of the ESIPT reaction. The constructed potential energy curves of both the S0 and S1 states while keeping the O─H distance of EDMN fixed at a series of values are used to illustrate the ESIPT process. The lower barrier of ~3.934 kcal/mol in the S1 state potential energy curve (lower than the 8.254 kcal/mol in the S0 state) provides the transfer mechanism. [ABSTRACT FROM AUTHOR]

In the title compound, [Mn2(C8H4O7S)2(C10H8N2)2(H2O)2], pairs of hexacoordinated manganese(II) centres are bridged by 2-sulfonatoterephthalate(2−) anions to form cyclic centrosymmetric dimers, which are linked into sheets by O—H...O hydrogen bonds. [ABSTRACT FROM AUTHOR]

The asymmetric unit of the title compound, C6H16N+·C9H5O6−·C9H6O6·2H2O, consists of a protonated triethylamine cation, one singly deprotonated trimesate anion, one trimesic acid molecule, and two water molecules. The trimesic acid molecules form stacks, while pairs of parallel anions also have π–π interactions; the perpendicular distances between adjacent parallel benzene rings are 3.291 (1), 3.347 (1) and 3.390 (1) Å. Intermolecular hydrogen bonds are found, with all O—H and N—H groups as donors, forming a three-dimensional network. [ABSTRACT FROM AUTHOR]

In this present work, we theoretically investigate a novel system 3‐hydroxy‐2‐(5‐(5‐(5‐(3‐hydroxy‐4‐oxo‐4H‐chromen‐2‐yl)thiophen‐2‐yl)thiophen‐2‐yl)thiophen‐2‐yl)‐4H‐chromen‐4‐one (FT) based on density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. Via calculating the reduced density gradient (RDG) versus sign(λ2) ρ, we firstly verify the formation of the dual intramolecular hydrogen bonds (O1─H2···O3 and O4─H5···O6) for FT form in the S0 state. Then comparing the primary structural parameters and corresponding infrared (IR) vibrational spectra involved in hydrogen bonds between S0 and S1 state, we demonstrate that these two intramolecular hydrogen bonds should be strengthened in the S1 state. Insights into the vertical excitation process, our theoretical results reproduced experimental absorption nature, which confirms that the theoretical level (B3LYP/TZVP) is reasonable and effective in this work. And frontier molecular orbitals (MOs) depict the nature of electronically excited state and support the excited‐state intramolecular proton transfer (ESIPT) reaction. According to the calculated results of potential energy curves along stepwise and synergetic O1─H2 and O4─H5 coordinates, we verify that only the excited‐state single‐proton transfer could occur for FT molecule in the S1 state, although it possesses two intramolecular hydrogen bonds. We not only investigate the detail excited‐state behaviors for FT system and elaborate the ESIPT mechanism but also explain previous experimental results. Dual intramolecular hydrogen bonds should be strengthened upon photoexcitation. The charge redistribution reveals the tendency of ESIPT reaction. We confirm that only single proton transfer occurs in the S1 state. [ABSTRACT FROM AUTHOR]

In this work, using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, we theoretically explore the excited state dynamical process about a novel DHDA-23-00 system [Phys. Chem. Chem. Phys. 19 (2017) 28641-28646]. Combining electrostatic potential surface (EPS) and the reduced density gradient (RDG) methods, we can affirm the two intramolecular hydrogen bonds (O1-H2⋯O3 and O4-H5⋯O6) should be formed in the S 0 state for DHDA-23-00. Exploring primary chemical structural changes (bond lengths and bond angles involved in hydrogen bonds) upon the photo-excitation, we verify these two hydrogen bonds are strengthening in the S 1 state. In view of the infrared (IR) vibrational spectra, the phenomenon of strengthening O1-H2⋯O3 and O4-H5⋯O6 can be confirmed once again. Analyses about frontier molecular orbitals (MOs) in the excitation process, it can be found charge redistribution around hydroxide radical moiety could play important roles in enhancing intramolecular hydrogen bonds O1-H2⋯O3 and O4-H5⋯O6. Given this kind of charge transfer may facilitate excited state proton transfer (ESPT) process, we construct the potential energy surfaces (PESs) along with two hydrogen bonds to provide the excited state dynamical overall perspective. For DHDA-23-00, even though the charge transfer supports the ESPT process in acetonitrile solvent, excited state potential energy barriers confirm ESPT reaction does not occur for DHDA-23-00 system that is consistent with experimental phenomenon. [ABSTRACT FROM AUTHOR]

[Display omitted] • Full-range structural coloration is enabled through temperature stimulation. • A rapid and linear response to temperature is realized in terms of color switching. • Reversible and stable color switching is achieved at least 100 cycles. • The color switching is used for sensors, decoration, and information encryption. Bioinspired dynamic structural-colored materials have shown wide applications in sensing, display, information encryption and security. However, because of restrictions of design principles, it remains a big challenge to break limitations of color control, color-changing rate, and repeatability. Here, we demonstrate fast, linear, and reliable structural-color modulations with a one-component chiral nematic mesophase following a thermally-induced phase separation mechanism. Molecular dynamic simulation reveals that the hydrogen bonding tunability between the mesophase and solvent dominates the fast and reversible phase transition behaviors that account for the fast and repeatable color responses. The photonic crystal displays wide-range (red-to-purple) colorations by controlling the mesophase concentration and external temperature. Due to the linear change of turbidity upon temperature stimuli, linearly programmable color regulations are enabled without color hysteresis. These features allow the development of multi-functional devices with applications for portable sensors, painting decoration, and information security encryption. [ABSTRACT FROM AUTHOR]

In the title ZnII complex, [ZnCl2(C6H10N2O)2], the Zn atom is coordinated by two Cl atoms and two imidazole N atoms in a distorted tetra­hedral geometry. Weak inter­molecular C—H⋯O hydrogen bonding occurs between the methyl and meth­oxy groups. [ABSTRACT FROM AUTHOR]

Using the density functional theory (DFT) and time‐dependent density functional theory (TDDFT) methods, we theoretically explore a novel fluorescent sensor molecule (abbreviated as "2") (Sensors Actuat B‐Chem. 2018, 263, 585). Because of its symmetry, three stable structures can be located, ie, 2‐enol, 2‐SPT, and 2‐DPT forms in both S0 and S1 states. Via comparing the bond lengths and bond angles involved in the hydrogen bonding moieties, we find the dual intramolecular hydrogen bonds should be strengthened in the S1 state. And based on infrared (IR) vibrational simulations, we further confirm the strengthening dual hydrogen bonds. Upon the photo‐excitation process, the charge redistribution via frontier molecular orbitals (MOs) reveals the tendency of excited state intramolecular proton transfer (ESIPT) reaction. In addition, the constructed S0‐state and S1‐state potential energy curves demonstrate that the excited state single proton transfer (ESSPT) should be the most supported one from 2‐enol to 2‐SPT form. In view of the S1‐state stable 2‐SPT and 2‐DPT structures as well as the fluorescence peaks of them, we can further confirm the ESSPT mechanism for 2 chemosensor. This work not only clarifies the excited state behaviors of 2 system but also successfully explain the previous experimental phenomenon. The strengthening dual intramolecular hydrogen bonds (O1H2···N3 and O4H5···N6) of 2 provides the possibility for ESIPT process.The redistribution of charge involved in the hydrogen bonding moieties facilitates the ESIPT reaction.Potential energy curves and emission spectra confirm that the excited state single proton transfer should occur for 2 system. [ABSTRACT FROM AUTHOR]