scholarly journals Theoretical modeling of defects in the molecular crystal of 2-(2'-hydroxyphenyl)benzothiazole

2020 ◽  
Vol 28 (1) ◽  
pp. 43-48
Author(s):  
Y. Syetov
Keyword(s):  
Hydrogen Bond ◽  
Density Functional ◽  
Periodic Structures ◽  
Tight Binding ◽  
Energy Difference ◽  
Intramolecular Proton Transfer ◽  
Hydrogen Bond Energy ◽  
Stable Conformation ◽  
Equilibrium Number ◽  
Isolated Molecules

2-(2'-hydroxyphenyl)benzothiazole is a photoreactive compound that exhibits excited state intramolecular proton transfer in the structure with an OH...N hydrogen bond. Energy of various structures is calculated for isolated molecules, clusters and periodic structures of 2-(2'-hydroxyphenyl)benzothiazole by density-functional based tight-binding methods. It is shown that the most stable conformation of the isolated molecule is a planar structure with an OH...N hydrogen bond. Other conformations have significantly larger energy in comparison with the average room temperature heat energy that implies a low equilibrium number of those structures in non-polar solvents. In crystal the defect with lowest energy is non-hydrogen-bonded conformation formed by rotation of the OH bond. The energy of this defect is close to the energy difference for corresponding conformations of the isolated molecule. For other conformations, the energy values of the defects are larger than the energy differences for isolated molecules. In contrast to the crystal of 2-(2'-hydroxyphenyl)benzoxazole, energy of the defect caused by the entire molecule reorientation is comparable with the energy of defects caused by different conformations.

scholarly journals Lattice vibrations and disorder in crystalline benzoxazoles undergoing excited state intramolecular proton transfer: DFTB modeling

2018 ◽  
Vol 26 (1) ◽  
pp. 57-62
Author(s):  
Y. Syetov
Keyword(s):  
Density Functional ◽  
Tight Binding ◽  
Intramolecular Proton Transfer ◽  
Lattice Vibrations ◽  
Molecular Vibrations ◽  
Out Of Plane ◽  
Symmetry Structure ◽  
Internal Crystal ◽  
Internal Vibrations ◽  
Isolated Molecules

Structure and crystal lattice vibrations are calculated for 2-(2'-hydroxyphenyl)bezoxazole and bis-(2,5-benzoxazolyl)hydroquinone by density functional based tight-binding methods. Despite lowering of the molecular symmetry, structure parameters of the molecules in crystal and forms of the internal vibrations are similar to those of isolated molecules. Weak interaction between the molecules in the molecular crystals leads to appearance of the external vibrations, splitting and mixing of the vibrations of the isolated molecules into internal crystal vibrations. External and internal vibrations are not separated well; contribution of the translations and librations is noticeable in the region below 150 cm-1. The magnitude ofthe splitting does not exceed 4 cm-1 for the most vibrations. The internal vibrations that correspond to the out-of plane molecular vibrations demonstrate larger molecule-to-crystal frequency shift than in-plane modes, mostly to higher frequencies, whereas the modes involving torsion motion of the OH bond are shifted toward lower frequencies. Mixing occurs for the molecular vibrations with frequencies that are different by less than 16 cm-1. Calculations performed for model molecular clusters show that the defectcaused by different molecule orientation has lower energy than the defect related to the formation ofrotamers.

scholarly journals Lattice vibrations of the molecular crystal of photoreactive substance with defects

2019 ◽  
Vol 27 (2) ◽  
pp. 77-80
Author(s):  
Y. Syetov
Keyword(s):  
Hydrogen Bond ◽  
Density Functional ◽  
Tight Binding ◽  
Intramolecular Proton Transfer ◽  
Frequency Region ◽  
Model Structure ◽  
Lattice Vibrations ◽  
Unit Cells ◽  
Intramolecular Hydrogen ◽  
Internal Vibrations

Lattice vibrations are studied theoretically by density-functional based tight-binding methods for the model structure of 2-(2'-hydroxyphenyl)benzoxazole crystal with defects. 2-(2'-hydroxyphenyl)benzoxazole is a photoreactive compound that exhibits excited state intramolecular proton transfer in the structure with an OH...N hydrogen bond. The unit cell of the model structure consists of two crystal unit cells where the molecules have the structure with intramolecular hydrogen bonds OH...N and one molecule is supposed to have a different orientation of the whole molecule or its fragment. The different orientation of the fragment forms the structure with an intramolecular hydrogen bond OH...O. It is calculated that defect caused by the different orientation of the molecule have a lower energy than the defect caused by the different orientation of the fragment. In the frequency region where the contribution of external vibrations of the molecules is significant, the vibrations mainly involve several molecules in the cell. In the region of internal vibrations there are modes, which are local vibrations of the defects. These local vibrations involve mainly motion of the atoms constituting the defect molecule. The number of local vibrations is larger for the defect that corresponds to the formation of the structure with the OH...O hydrogen bond than for the defect that corresponds to the different  orientation of the whole molecule with the OH...N hydrogen bond. The internal vibrations of the defect molecule formed by the different orientation of phenol fragment in the lattice undergoes frequency shift in relation to the frequency of the modes of isolated molecule.

A Density Functional Study for Hydrogen Bond Energy by Employing Real Space Grids

2000 ◽  
Vol 29 (3) ◽  
pp. 222-223 ◽  
Author(s):  
Hideaki Takahashi ◽  
Takumi Hori ◽  
Tadafumi Wakabayashi ◽  
Tomoshige Nitta
Keyword(s):  
Hydrogen Bond ◽  
Bond Energy ◽  
Density Functional ◽  
Real Space ◽  
Functional Study ◽  
Hydrogen Bond Energy ◽  
Density Functional Study

Elaborating a new excited state intramolecular proton transfer (ESPT) mechanism for a new π-conjugated dye 2, 2′-((5-(2-(4-methoxyphenyl)ethenyl)-benzene-1,1-diyl)-bis-(nitrilomethylylidene)-diphenol)

2018 ◽  
Vol 96 (3) ◽  
pp. 351-357 ◽  
Author(s):  
Dapeng Yang ◽  
Min Jia ◽  
Xiaoyan Song ◽  
Qiaoli Zhang
Keyword(s):  
Hydrogen Bond ◽  
Excited State ◽  
Charge Transfer ◽  
Hydrogen Bonds ◽  
Proton Transfer ◽  
Density Functional ◽  
Dynamical Behavior ◽  
Intramolecular Proton Transfer ◽  
Intramolecular Hydrogen Bonds ◽  
Intramolecular Hydrogen

In this work, the excited state dynamical behavior of a novel π-conjugated dye 2,2′-((5-(2-(4-methoxyphenyl)ethenyl)-benzene-1,1-diyl)-bis-(nitrilomethylylidene)-diphenol) (C1) has been investigated. Two intramolecular hydrogen bonds of C1 are tested to pre-existing in the ground state via AIM and reduced density gradient. Using a time-dependent density functional theory (TDDFT) method, it has been substantiated that the intramolecular hydrogen bonds of C1 should be strengthened in the S1 state via analyzing fundamental bond length, bond angles, and corresponding infrared vibrational modes. The most obvious variation of these two hydrogen bonds is the O4–H5···N6 bond, which might play important roles in excited state behavior for the C1 system. Furthermore, based on electronic excitation, charge transfer could occur. Just due to this kind of charge re-distribution, two hydrogen bonds should be tighter in the first excited state, which is consistent with the variation of hydrogen bond lengths. Thus, the phenomenon of charge transfer is reasonable evidence for confirming the occurrence of the excited state proton transfer (ESPT) process in the S1 state. Our theoretically constructed potential energy surfaces of C1 show that excited state single proton transfer should occur along with the O4–H5···N6 hydrogen bond rather than the O1–H2···N3 bond. We not only clarify the ESIPT mechanism for C1 but put forward new affiliation and explain a previous experiment successfully.

scholarly journals A Theoretical and Experimental Study on Hydrogen-bonding Interactions between 4H-1,2,4-triazole-3,5-diamine and DMSO/water

2020 ◽  
Vol 39 (1) ◽  
pp. 65
Author(s):  
Mustafa Tuğfan Bilkan
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Density Functional ◽  
Energy Difference ◽  
Water Molecules ◽  
Hydrogen Atoms ◽  
Hydrogen Bond Acceptor ◽  
Functional Theory ◽  
Hydrogen Bonding Interactions ◽  
Aqueous Complexes

In this paper, 4TZDA-DMSO/water complexes formed by hydrogen bonding interactions were investigated by a combined experimental and computational approach. Two conformations of 4TZDA molecule were considered. Seven hydrogen-bonded 4TZDA-DMSO/H2O complexes were characterized in terms of geometries, energies and vibrational frequencies. The optimizations and calculations were performed for the complexes by Density Functional Theory. In the experimental part, the DMSO/H2O solutions of 4TZDA were prepared and infrared spectra of the solutions were recorded. After the solvation process, significant shifts in the existing bands and new band rising were observed in the experimental spectra of 4TZDA. Following results are found from this study: 1) 4TZDA (I) is more stable than 4TZDA (II). 2) Seven 4TZDA-DMSO and 4TZDA-H2O complexes are investigated and it is seen that all nitrogen atoms of 4TZDA are hydrogen bond acceptor and all hydrogen atoms are hydrogen bond donors. 3) Aqueous complexes of 4TZDA are found to form stronger hydrogen bonds compared to DMSO complexes. 4) It is determined that the most stable structures are intermolecular interactions of lpO⋯H-N and lpN⋯H-O type for the complexes. For these interactions, h-bond lengths are calculated as 1.78 and 1.90 Å and interaction energies are -7.10 kJ/mol for 4TZDA-DMSO and -50.5 kJ/mol for 4TZDA-H2O. Because of this energy difference in the complexes, it can be said 4TZDA forms more stable complexes with water molecules compared to DMSO molecules and with this property, it is an ideal molecule for pharmacological purposes.

Theoretical study of the ground and excited states of 1-methylamideanthraquinone and its complex with fluoride anion

2016 ◽  
Vol 15 (04) ◽  
pp. 1650033
Author(s):  
Bing-Qiang Wang ◽  
Xiao-Fen Yin ◽  
Yan-Yun Dong ◽  
Cai-Yun Zhang
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Bond ◽  
Proton Transfer ◽  
Density Functional ◽  
Intermolecular Hydrogen Bond ◽  
Emission Spectra ◽  
Intramolecular Proton Transfer ◽  
Fluoride Anion ◽  
Functional Theory ◽  
Intramolecular Hydrogen

We have performed a series of calculations using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) for 1-methylamideanthraquinone (MAAQ). In the S0 state of MAAQ, amide group is coplanar with anthraquinone, and an intramolecular hydrogen bond [Formula: see text] is formed. The [Formula: see text] transition has an intramolecular charge transfer character. Two stable structures (planar nMAAQ and twisted tMAAQ) have been obtained in the S1 state of MAAQ. Thereinto, nMAAQ is lower by 0.105[Formula: see text]eV than tMAAQ in energy, so nMAAQ is the dominant conformation in the S1 state of MAAQ and the emission spectra of tMAAQ cannot be observed in the solution of MAAQ. Excited state intramolecular proton transfer (ESIPT) between C[Formula: see text]O and N–H was not observed in the S1 state of MAAQ. Upon addition of fluoride anion, only twisted conformations were obtained in both S0 and S1 states of MAAQ-F[Formula: see text]. An intermolecular hydrogen bond [Formula: see text] is formed in the S0 state, and intermolecular proton transfer happens in the S1 state for MAAQ-F[Formula: see text].

scholarly journals Theoretical Investigation of Excited-State Intramolecular Double-Proton Transfer Mechanism of Substituent Modified 1, 3-Bis (2-pyridylimino)-4,7-dihydroxyisoindole in Dichloromethane Solution

2021 ◽  
pp. 1-12
Author(s):  
Xiumin Liu ◽  
Heyao Yuan ◽  
Yuxi Wang ◽  
Yaping Tao ◽  
Yi Wang ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Excited State ◽  
Proton Transfer ◽  
Density Functional ◽  
Photophysical Properties ◽  
Substituent Effects ◽  
Intramolecular Proton Transfer ◽  
Hydrogen Bond Formation ◽  
Dichloromethane Solution ◽  
Double Proton Transfer

In this paper, density functional theory (DFT) and time-dependent DFT (TDDFT) methods were used to investigate substituent effects and excited-state intramolecular double-proton transfer (ESIDPT) in 1, 3-bis (2-pyridylimino)-4, 7-dihydroxyisoindole (BPI–OH) and its derivatives. The results of a systematic study of the substituent effects of electron-withdrawing groups (F, Cl and Br) on the adjacent sites of the benzene ring were used to regulate the photophysical properties of the molecules and the dynamics of the proton-transfer process. Geometric structure comparisons and infrared (IR) spectroscopic analysis confirmed that strengthening of the intramolecular hydrogen bond in the first excited state (S1) facilitated proton transfer. Functional analysis of the reduced density gradient confirmed these conclusions. Double-proton transfer in BPI–OH is considered to occur in two steps, i.e., BPI–OH (N) [Formula: see text] BPI–OH (T1) [Formula: see text] BPI–OH (T2), in the ground state (S0) and the S1 state. The potential-energy curves (PECs) for two-step proton transfer were scanned for both the S0 and S1 states to clarify the mechanisms and pathways of proton transfer. The stepwise path in which two protons are consecutively transferred has a low energy barrier and is more rational and favorable. This study shows that the presence or absence of coordinating groups, and the type of coordinating group, affect the hydrogen-bond strength. A coordinating group enhances hydrogen-bond formation, i.e., it promotes excited-state intramolecular proton transfer (ESIPT).

scholarly journals Theoretical Investigation of Excited-State Intramolecular Double-Proton Transfer Mechanism of Substituent Modified 1, 3-Bis (2-pyridylimino)-4,7-dihydroxyisoindole in Dichloromethane Solution

2021 ◽  
Author(s):  
Xiumin Liu ◽  
Wenzhi Li ◽  
Yuxi Wang ◽  
Yaping Tao ◽  
Yi Wang ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Excited State ◽  
Proton Transfer ◽  
Density Functional ◽  
Photophysical Properties ◽  
Substituent Effects ◽  
Intramolecular Proton Transfer ◽  
Hydrogen Bond Formation ◽  
Dichloromethane Solution ◽  
Double Proton Transfer

Abstract Density functional theory (DFT) and time-dependent DFT (TDDFT) methods were used to investigate substituent effects and excited-state intramolecular double-proton transfer in 1, 3-bis (2-pyridylimino)-4, 7-dihydroxyisoindole (BPI-OH) and its derivatives. The results of a systematic study of the substituent effects of electron-withdrawing groups (F, Cl, and Br) on the adjacent sites of the benzene ring were used to regulate the photophysical properties of the molecules and the dynamics of the proton-transfer process. Geometric structure comparisons and infrared spectroscopic analysis confirmed that strengthening of the intramolecular hydrogen bond in the first excited state (S1) facilitated proton transfer. Functional analysis of the reduction density gradient confirmed these conclusions. Double-proton transfer in BPI-OH is considered to occur in two steps, i.e., BPI-OH (N) →BPI-OH (T1) →BPI-OH (T2), in the ground state (S0) and the S1 state. The potential-energy curves for two-step proton transfer were scanned for both the S0 and S1 states to clarify the mechanisms and pathways of proton transfer. The stepwise path in which two protons are consecutively transferred has a low energy barrier and is more rational and favorable. This study shows that the presence or absence of coordinating groups, and the type of coordinating group, affect the hydrogen-bond strength. A coordinating group enhances hydrogen-bond formation, i.e., it promotes excited-state intramolecular proton transfer.

Accurate Hydrogen Bond Energies within the Density Functional Tight Binding Method

2015 ◽  
Vol 119 (14) ◽  
pp. 3535-3544 ◽  
Author(s):  
A. Domínguez ◽  
T. A. Niehaus ◽  
T. Frauenheim
Keyword(s):  
Hydrogen Bond ◽  
Density Functional ◽  
Tight Binding ◽  
Bond Energies ◽  
Tight Binding Method ◽  
Hydrogen Bond Energies

scholarly journals Vacancies in the molecular crystal of 2-(2'-hydroxyphenyl)benzothiazole

2021 ◽  
Vol 29 (1) ◽  
pp. 81-84
Author(s):  
Y. Syetov
Keyword(s):  
Excited State ◽  
Ground State ◽  
Molecular Crystal ◽  
Density Functional ◽  
Tight Binding ◽  
Intramolecular Proton Transfer ◽  
Dihedral Angles ◽  
Empirical Correction ◽  
Planar Conformation ◽  
Periodic Model

Structure of molecular units is calculated for the periodic model corresponding to the crystal lattice of 2-(2'-hydroxyphenyl)benzothiazole with vacancies. 2-(2' -hydroxyphenyl)benzothiazole is a luminescent organic substance undergoing excited state intramolecular proton transfer. The calculations are performed with density-functional based tight-binding methods usding Van der Waals interaction empirical correction. It is found that the dihedral angles formed by benzothiazole and phenol parts of the molecules deviate in the vicinity of the vacancy. The vacancy provides enough space for non-planar conformation of the molecules in the ground state. At the same time the increase in energy of the periodic structure with the vacancies caused by appearance of the non-planar conformation is larger than the corresponding increase in the isolated molecule.

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