Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, Jan 1, 2010
In this work, we report a theoretical study on molecular structure, vibrational spectra and nonli... more In this work, we report a theoretical study on molecular structure, vibrational spectra and nonlinear optical properties of orthoarsenic acid–tris-(hydroxymethyl)-aminomethane (OATA). The theoretical geometrical parameters in the ground state have been investigated by density functional method (B3LYP and BLYP) with 6-311G(d,p) basis set. The influence of intermolecular interactions effects on molecular properties has been considered by calculation performed on (OATA) dimer. The optimized geometric bond lengths and bond angles are in well agreement with the experimental data. As compared to theoretical frequencies of the monomer, the calculated values obtained for (OATA) dimer are in much better agreement with the experiment. All experimental vibrational bands have been discussed and assigned to normal modes on the basis of our theoretical calculations. B3LYP method has shown better fit to experimental ones than BLYP in calculation vibrational frequencies. To investigate nonlinear optical behaviour, the electric dipole moment μ, the polarizability α and the hyperpolarizability β were computed using DFT//B3LYP/6-311G(d,p) method.
This paper presents the results of our calculations of the geometric parameters, vibrational spec... more This paper presents the results of our calculations of the geometric parameters, vibrational spectra and hyperpolarizability of a non linear optical material, l-histidine bromide. Due to the lack of sufficiently precise information on the geometric structure available in literature, theoretical calculations were preceded by re-determination of the crystal X-ray structure. Single crystals of l-histidine bromide have been grown by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in the non-Centro symmetric space group P212121 of the orthorhombic system. Raman spectra have been recorded in the range [200–3500 cm−1]. All observed vibrational bands have been discussed and assigned to normal mode or to combinations and overtones on the basis of our calculations. The optimized geometric bond lengths and bond angles obtained by using HF and DFT (B3LYP and BLYP) show good agreement with the experimental data. Comparison between the measured and the calculated vibrational frequencies indicate that B3LYP is superior to the scaled HF approach for molecular vibrational problems. To investigate microscopic second order non linear optical properties of l-histidine bromide, the electric dipole μ, the polarizability α and the hyperpolarizability β were computed using DFT//B3LYP/6-31G(d) method. According to our calculations, the title compound exhibits non-zero β value revealing microscopic second order NLO behaviour.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, Jan 1, 2010
This paper presents the results of our calculations on the geometric parameters, vibrational spec... more This paper presents the results of our calculations on the geometric parameters, vibrational spectra and hyperpolarizability of a non-linear optical material l-histidine chloride monohydrate. Due to the lack of sufficiently precise information on geometric parameters available in literature, theoretical calculations were preceded by re-determination of the crystal X-ray structure. Single crystal of l-histidine chloride monohydrate has been growing by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in the non-Centro-symmetric space group P212121 of orthorhombic system. IR spectrum has been recorded in the range [400–4000 cm−1]. All the experimental vibrational bands have been discussed and assigned to normal mode or to combinations on the basis of our calculations. The optimized geometric bond lengths and bond angles obtained by using DFT//B3LYP/6-31G (d) method show a good agreement with the experimental data. The calculated vibrational spectra are in well agreement with the experimental one. To investigate microscopic second-order non-linear optical NLO behavior of the examined complex, the electric dipole μ, the polarizability α and the hyperpolarizability β were computed using DFT//B3LYP/6-31G (d) method. The time-dependent density functional theory (TD-DFT) was employed to descript the molecular electron structure of the title compound using the B3LYP/6-31G (d) method. According to our calculations, l-histidine chloride monohydrate exhibits non-zero β value revealing microscopic second-order NLO behavior.
In this work, we report a combined experimental and theoretical study on molecular structure and ... more In this work, we report a combined experimental and theoretical study on molecular structure and vibrational spectra of l-histidinium dihydrogen phosphate-phosphoric acid, with particular emphasize on the correlation between the intermolecular hydrogen bonds and the hyperpolarizability. Single crystal of l-histidinium dihydrogen phosphate-phosphoric acid has been subjected to X-ray diffraction and Raman spectroscopy. The title compound crystallises in the non-centrosymmetric space group P21. Raman spectra have been recorded in the frequency range [150–3350 cm−1]. To obtain a more reliable assignment of the Raman and IR spectra, we have calculated the geometry and the frequencies using HF and DFT methods. All the experimental vibrational bands have been discussed and assigned to normal mode or to combinations and overtones on the basis of our calculations. The optimized geometric bond lengths and bond angles obtained by using HF and DFT (B3LYP and BLYP) are in well agreement with the experimental data. The results of DFT-B3LYP method have shown better fit to experimental ones than HF in evaluating vibrational frequencies. To investigate microscopic second order non-linear optical behaviour of the examined complex, the electric dipole μ, the polarizability α and the hyperpolarizability β were computed using DFT//B3LYP/6-31 G(d) method. According to our calculation, the title compound exhibits non-zero β value revealing microscopic second order NLO behaviour.
The tri (dimetylammonium) hexa-iodobismuthate of general formula [(CH3)2NH2]3[BiI6] is an organic... more The tri (dimetylammonium) hexa-iodobismuthate of general formula [(CH3)2NH2]3[BiI6] is an organic–inorganic hybrid material. The crystal lattice is composed of discrete [BiI6] anions surrounded by dimethylamine cations. The X-ray diffraction pattern was obtained and indexed on the basis of rhombohedra unit cell with the R3¯ space group. Room temperature IR and Raman spectra of the title compound were recorded and analyzed. Semi-empirical Parameter Model three (PM3) method as well as density functional theory (DFT) calculations have been performed to derive the equilibrium geometry, vibrational wave numbers and a prediction of IR and Raman spectral activities. In this compound the bands corresponding to the cation vibrational modes show that the symmetry of these cations is distorted and they are strongly hydrogen bonded to the respective anions. The frontier molecular orbital and the energy gap between the highest occupied molecular orbital (HOMO) and the lowest un-occupied molecular orbital (LUMO) were calculated with time dependent density functional theory (TD-DFT). The results show good consistent with the experiment and confirm the contribution of metal orbital to the HOMO–LUMO boundary.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, Jan 1, 2011
This paper presents the results of our calculations on the geometric parameters, vibrational spec... more This paper presents the results of our calculations on the geometric parameters, vibrational spectra and hyperpolarizability of a nonlinear optical material l-histidine oxalate. Due to the lack of sufficiently precise information on geometric structure in literature, theoretical calculations were preceded by re-determination of the crystal X-ray structure. Single crystal of l-histidine oxalate has been growing by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in the non-Centro symmetric space group P212121 of orthorhombic system. The FT-IR and Raman spectra of l-histidine oxalate were recorded and analyzed. The vibrational wave numbers were examined theoretical with the aid of Gaussian98 package of programs using the DFT//B3LYP/6-31G(d) level of theory. The data obtained from vibrational wave number calculations are used to assign vibrational bands obtained in IR and Raman spectroscopy of the studied compound. The geometrical parameters of the title compound are in agreement with the values of similar structures. To investigate microscopic second order non-linear optical NLO behaviour of the examined complex, the electric dipole μtot, the polarizability αtot and the hyperpolarizability βtot were computed using DFT//B3LYP/6-31G(d) method. According to our calculation, the title compound exhibits non-zero βtot value revealing microscopic second order NLO behaviour.. In acid-base hybrid crystals, hydrogen bonds play an important role not only in the creation of crystal structure and its stability, but also in the enhancement of the polarizability α and the hyperpolarizability β of the crystal due to the perturbation of the electronic structure of l-histidine and also due to the strong electron–phonon coupling.► In this study, l-histidine oxalate crystallizes in the space group P212121 of orthorhombic system. ► All the experimental vibrational bands have been discussed and assigned to normal mode. ► The non linear optical properties of l-histidine oxalate have been investigated by DFT method. ► The results indicate hydrogen bonding increased the hyperpolarizability of the crystal.
Journal of Molecular Structure-theochem, Jan 1, 2009
Theoretical calculations were performed using density functional theory for studying the molecula... more Theoretical calculations were performed using density functional theory for studying the molecular structure and vibrational spectra of the asymmetric squaraine [(2-dimethylamino-4-anilino) squaraine] (ADTCH3) in the ground state. The influence of intermolecular interactions effects on molecular properties have been considered by calculation performed on (ADTCH3) dimer. The optimized geometric bond lengths and bond angles obtained by using B3LYP/6-31G(d) show a good agreement with the experimental data. As compared to theoretical frequencies of the monomer, the calculated values obtained for (ADTCH3) dimer are in much better agreement with the experiment. All the experimental vibrational bands have been discussed and assigned to normal modes on the basis of our calculations. With respect to the study of Silva et al., some modes have been reassigned in the light of present theoretical results. In virtue of time dependent density functional theories (TD-DFT), the low-lying excited states of (ADTCH3) are determined using 6-31G(d) basis set. The calculations show that using TD-B3LYP/6-31G(d) approach, experimental absorption spectrum has been well reproduced. It has been concluded that the lowest singlet excited state (S1) of the title compound is mainly derived from the (HOMO → LUMO) (π → π∗) electron transition located on oxocarbon ring.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, Jan 1, 2010
In this work, we report a theoretical study on molecular structure, vibrational spectra and nonli... more In this work, we report a theoretical study on molecular structure, vibrational spectra and nonlinear optical properties of orthoarsenic acid–tris-(hydroxymethyl)-aminomethane (OATA). The theoretical geometrical parameters in the ground state have been investigated by density functional method (B3LYP and BLYP) with 6-311G(d,p) basis set. The influence of intermolecular interactions effects on molecular properties has been considered by calculation performed on (OATA) dimer. The optimized geometric bond lengths and bond angles are in well agreement with the experimental data. As compared to theoretical frequencies of the monomer, the calculated values obtained for (OATA) dimer are in much better agreement with the experiment. All experimental vibrational bands have been discussed and assigned to normal modes on the basis of our theoretical calculations. B3LYP method has shown better fit to experimental ones than BLYP in calculation vibrational frequencies. To investigate nonlinear optical behaviour, the electric dipole moment μ, the polarizability α and the hyperpolarizability β were computed using DFT//B3LYP/6-311G(d,p) method.
This paper presents the results of our calculations of the geometric parameters, vibrational spec... more This paper presents the results of our calculations of the geometric parameters, vibrational spectra and hyperpolarizability of a non linear optical material, l-histidine bromide. Due to the lack of sufficiently precise information on the geometric structure available in literature, theoretical calculations were preceded by re-determination of the crystal X-ray structure. Single crystals of l-histidine bromide have been grown by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in the non-Centro symmetric space group P212121 of the orthorhombic system. Raman spectra have been recorded in the range [200–3500 cm−1]. All observed vibrational bands have been discussed and assigned to normal mode or to combinations and overtones on the basis of our calculations. The optimized geometric bond lengths and bond angles obtained by using HF and DFT (B3LYP and BLYP) show good agreement with the experimental data. Comparison between the measured and the calculated vibrational frequencies indicate that B3LYP is superior to the scaled HF approach for molecular vibrational problems. To investigate microscopic second order non linear optical properties of l-histidine bromide, the electric dipole μ, the polarizability α and the hyperpolarizability β were computed using DFT//B3LYP/6-31G(d) method. According to our calculations, the title compound exhibits non-zero β value revealing microscopic second order NLO behaviour.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, Jan 1, 2010
This paper presents the results of our calculations on the geometric parameters, vibrational spec... more This paper presents the results of our calculations on the geometric parameters, vibrational spectra and hyperpolarizability of a non-linear optical material l-histidine chloride monohydrate. Due to the lack of sufficiently precise information on geometric parameters available in literature, theoretical calculations were preceded by re-determination of the crystal X-ray structure. Single crystal of l-histidine chloride monohydrate has been growing by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in the non-Centro-symmetric space group P212121 of orthorhombic system. IR spectrum has been recorded in the range [400–4000 cm−1]. All the experimental vibrational bands have been discussed and assigned to normal mode or to combinations on the basis of our calculations. The optimized geometric bond lengths and bond angles obtained by using DFT//B3LYP/6-31G (d) method show a good agreement with the experimental data. The calculated vibrational spectra are in well agreement with the experimental one. To investigate microscopic second-order non-linear optical NLO behavior of the examined complex, the electric dipole μ, the polarizability α and the hyperpolarizability β were computed using DFT//B3LYP/6-31G (d) method. The time-dependent density functional theory (TD-DFT) was employed to descript the molecular electron structure of the title compound using the B3LYP/6-31G (d) method. According to our calculations, l-histidine chloride monohydrate exhibits non-zero β value revealing microscopic second-order NLO behavior.
In this work, we report a combined experimental and theoretical study on molecular structure and ... more In this work, we report a combined experimental and theoretical study on molecular structure and vibrational spectra of l-histidinium dihydrogen phosphate-phosphoric acid, with particular emphasize on the correlation between the intermolecular hydrogen bonds and the hyperpolarizability. Single crystal of l-histidinium dihydrogen phosphate-phosphoric acid has been subjected to X-ray diffraction and Raman spectroscopy. The title compound crystallises in the non-centrosymmetric space group P21. Raman spectra have been recorded in the frequency range [150–3350 cm−1]. To obtain a more reliable assignment of the Raman and IR spectra, we have calculated the geometry and the frequencies using HF and DFT methods. All the experimental vibrational bands have been discussed and assigned to normal mode or to combinations and overtones on the basis of our calculations. The optimized geometric bond lengths and bond angles obtained by using HF and DFT (B3LYP and BLYP) are in well agreement with the experimental data. The results of DFT-B3LYP method have shown better fit to experimental ones than HF in evaluating vibrational frequencies. To investigate microscopic second order non-linear optical behaviour of the examined complex, the electric dipole μ, the polarizability α and the hyperpolarizability β were computed using DFT//B3LYP/6-31 G(d) method. According to our calculation, the title compound exhibits non-zero β value revealing microscopic second order NLO behaviour.
The tri (dimetylammonium) hexa-iodobismuthate of general formula [(CH3)2NH2]3[BiI6] is an organic... more The tri (dimetylammonium) hexa-iodobismuthate of general formula [(CH3)2NH2]3[BiI6] is an organic–inorganic hybrid material. The crystal lattice is composed of discrete [BiI6] anions surrounded by dimethylamine cations. The X-ray diffraction pattern was obtained and indexed on the basis of rhombohedra unit cell with the R3¯ space group. Room temperature IR and Raman spectra of the title compound were recorded and analyzed. Semi-empirical Parameter Model three (PM3) method as well as density functional theory (DFT) calculations have been performed to derive the equilibrium geometry, vibrational wave numbers and a prediction of IR and Raman spectral activities. In this compound the bands corresponding to the cation vibrational modes show that the symmetry of these cations is distorted and they are strongly hydrogen bonded to the respective anions. The frontier molecular orbital and the energy gap between the highest occupied molecular orbital (HOMO) and the lowest un-occupied molecular orbital (LUMO) were calculated with time dependent density functional theory (TD-DFT). The results show good consistent with the experiment and confirm the contribution of metal orbital to the HOMO–LUMO boundary.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, Jan 1, 2011
This paper presents the results of our calculations on the geometric parameters, vibrational spec... more This paper presents the results of our calculations on the geometric parameters, vibrational spectra and hyperpolarizability of a nonlinear optical material l-histidine oxalate. Due to the lack of sufficiently precise information on geometric structure in literature, theoretical calculations were preceded by re-determination of the crystal X-ray structure. Single crystal of l-histidine oxalate has been growing by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in the non-Centro symmetric space group P212121 of orthorhombic system. The FT-IR and Raman spectra of l-histidine oxalate were recorded and analyzed. The vibrational wave numbers were examined theoretical with the aid of Gaussian98 package of programs using the DFT//B3LYP/6-31G(d) level of theory. The data obtained from vibrational wave number calculations are used to assign vibrational bands obtained in IR and Raman spectroscopy of the studied compound. The geometrical parameters of the title compound are in agreement with the values of similar structures. To investigate microscopic second order non-linear optical NLO behaviour of the examined complex, the electric dipole μtot, the polarizability αtot and the hyperpolarizability βtot were computed using DFT//B3LYP/6-31G(d) method. According to our calculation, the title compound exhibits non-zero βtot value revealing microscopic second order NLO behaviour.. In acid-base hybrid crystals, hydrogen bonds play an important role not only in the creation of crystal structure and its stability, but also in the enhancement of the polarizability α and the hyperpolarizability β of the crystal due to the perturbation of the electronic structure of l-histidine and also due to the strong electron–phonon coupling.► In this study, l-histidine oxalate crystallizes in the space group P212121 of orthorhombic system. ► All the experimental vibrational bands have been discussed and assigned to normal mode. ► The non linear optical properties of l-histidine oxalate have been investigated by DFT method. ► The results indicate hydrogen bonding increased the hyperpolarizability of the crystal.
Journal of Molecular Structure-theochem, Jan 1, 2009
Theoretical calculations were performed using density functional theory for studying the molecula... more Theoretical calculations were performed using density functional theory for studying the molecular structure and vibrational spectra of the asymmetric squaraine [(2-dimethylamino-4-anilino) squaraine] (ADTCH3) in the ground state. The influence of intermolecular interactions effects on molecular properties have been considered by calculation performed on (ADTCH3) dimer. The optimized geometric bond lengths and bond angles obtained by using B3LYP/6-31G(d) show a good agreement with the experimental data. As compared to theoretical frequencies of the monomer, the calculated values obtained for (ADTCH3) dimer are in much better agreement with the experiment. All the experimental vibrational bands have been discussed and assigned to normal modes on the basis of our calculations. With respect to the study of Silva et al., some modes have been reassigned in the light of present theoretical results. In virtue of time dependent density functional theories (TD-DFT), the low-lying excited states of (ADTCH3) are determined using 6-31G(d) basis set. The calculations show that using TD-B3LYP/6-31G(d) approach, experimental absorption spectrum has been well reproduced. It has been concluded that the lowest singlet excited state (S1) of the title compound is mainly derived from the (HOMO → LUMO) (π → π∗) electron transition located on oxocarbon ring.
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