• Bulletin of the Korean Chemical Society
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• v.24 no.11
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• pp.1671-1674
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• 2003

The effects of amine donors ($a:NH_2,\;b:NMe_2,\;c:NMePh,\;d:NPh_2$) and conjugation length on the molecular hyperpolarizabilities of a series of dipolar molecules have been theoretically investigated by using CPHF/6-31G method. The first hyperpolarizabilities (${\beta}$) of p-nitrobenzene derivatives increase with the donor in the order, $NH_2\;<\;NMe_2\;<\;NMePh\;<\;NPh_2$, whereas slightly different order is observed in more conjugated derivatives, i.e., $NH_2\;<\;NPh_2\;<\;NMe_2\;<\;NMePh$. The result has been attributed to the extent of charge transfer and torsion angle. Moreover, the results show that "non-traditional" ${\pi}$-conjugation effect exists in small compounds and decreases as the conjugation length between donor and acceptor increases.

• Journal of the Korean Chemical Society
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• v.57 no.4
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• pp.461-471
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• 2013

Optimized geometrical structure, atomic charges, molecular electrostatic potential, nonlinear optical (NLO) effects and thermodynamic properties of the title compound N-(2,5-methylphenyl)salicylaldimine (I) have been investigated by using ab initio quantum chemical computational studies. Calculated results showed that the enol form of (I) is more stable than keto form. The solvent effect was investigated for obtained molecular energies, hardneses and the atomic charge distributions of (I). Natural bond orbital and frontier molecular orbital analysis of the title compound were also performed. The total molecular dipole moment (${\mu}$), linear polarizability (${\alpha}$), and first-order hyperpolarizability (${\beta}$) were calculated by B3LYP method with 6-31G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311+G(d) and 6-311++G(d,p) basis sets to investigate the NLO properties of the compound (I). The standard thermodynamic functions were obtained for the title compound with the temperature ranging from 200 to 450 K.

• Journal of Photoscience
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• v.8 no.2
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• pp.79-82
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• 2001

2-(p-Diethylaminostyryl)pyrrole (I) and 2-[5-diethylaminothienyl]vinyl]pyrrole (II) derivatives with systematic variation of the acceptors have been synthesized and their first hyperpolarizabilities were measured. The $\beta$ values increased systematically as the aromatic resonance energy decreased. Moreover, the value of $\beta$ for the former increased gradually as the acceptor strength increased. The opposite trend observed in the latter series of compounds has been attributed to the distorted structure caused by the steric hindrance between the N-methyl group and the acceptor moiety.

• Bulletin of the Korean Chemical Society
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• v.17 no.8
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• pp.693-695
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• 1996

The steric effect on the first order hyperpolarizability of the β-nitrostyrene derivatives has been investigated by comparing the β values and the dihedral angles between the aryl and nitroalkenyl groups. In general the β value increased with the electron-donating ability of the substituent. The larger β value for 3,4-dimethoxy-β-nitrostyrene than that for p-methoxy-β-nitrostyrene has been attributed to the lower charge transfer energy for the former. The most striking substituent effect was observed in the β-methyl-β-nitrostyrene derivatives. Thus the β values for 3,4-dimethoxy- and p-methoxy derivatives of the latter decreased to near zero, probably because of the large distortion from planarity caused by the steric repulsion between the β-methyl and the aryl groups. The larger β value for p-dimethylamino-β-methyl-β-nitrostyrene has been interpreted with an increased electron-donating ability of the substituent and increased co-planarity.

• Bulletin of the Korean Chemical Society
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• v.29 no.3
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• pp.546-550
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• 2008

The title compound of nicotinato lead(II) complex [Pb$(C_5H_4NCOO)_2$] has been optimized at B3LYP/LANL2DZ and HF/LANL2DZ levels of theory. The calculated results show that the lead(II) ion adopts 2- coordinate geometry, which is the same as its crystal structure and different from the 4-coordinate geometry of isonicotinato lead(II) complex. Atomic charge distributions indicate that during forming the title compound, each nicotinic acid ion transfers their negative charges to central lead(II) ion. The electronic spectra calculated by B3LYP/LANL2DZ level show that there exist two absorption bands, which have some red shifts compared with those of isonicotinato lead(II) complex and the electronic transitions are mainly derived from intraligand $\pi$ -$\pi$ transition and ligand-to-metal charge transfer (LMCT) transition. CIS-HF method is not suitable for the system studied here. The thermodynamic properties of the title compound at different temperatures have been calculated and corresponding relations between the properties and temperature have also been obtained. The second order optical nonlinearity was calculated, and the molecular hyperpolarizability was $1.147754{\times}10^{-30}$ esu.