Crystal structure, spectroscopic (FT-IR, 1 H and 13 C NMR) characterization and density functional theory calculations on Ethyl 2-(dichloromethyl)-4-methyl-1-phenyl-6-thioxo-1,6-dihydropyrimidine-5-carboxylate

The effect of complex formation on the static and frequency-dependent nonlinear optical properties: A combined experimental and theoretical investigation

A novel mixed ligand Mn(II) complex of 6-Bromopyridine-2-carboxylic acid (6Brpca) and 4,4'-dimethyl-2,2'-dipyridyl has been prepared and structurally characterized using single-crystal X-ray diffraction. The spectroscopic properties were also analyzed by using FT-IR and UV-Vis spectral techniques. The coordination complexes having transition metal ions are known to have promising optical nonlinearity behavior. Therefore, B3LYP level density functional theory was used to investigate first- and second-order hyperpolarizabilities (β and γ) and provide a deep understanding of the relation between the structure and NLO properties. The calculations of frequency-dependent α, β, and γ at frequencies of ω = 0.0856252 and 0.0428126 au. for 6Brpca and Dmdpy ligands as well as Mn(II) complex have been also carried out using B3LYP/LanL2DZ level. Especially second harmonic generation (SHG) first and second hyperpolarizabilities (β(-2ω;ω,ω) and γ (-2ω;ω,ω,0)) parameters for Mn(II) complex have been calculated as 11448 × 10-30 and 680035 × 10-36 esu, respectively. It has been determined that there is a tremendous increase in β and γ parameters when 6Brpca and Dmdpy ligands coordinate to the high spin multiplicity Mn(II) ion. Theoretical calculations revealed that the large first- and second-order hyperpolarizabilities are caused by strong intramolecular charge transfer between the transition metal and the coordinated ligands. These results indicate that the the organometallic complex under investigation is valuable candidate for optoelectronic and photonic applications.

First and second order hyperpolarizabilities of flavonol derivatives: A density functional theory study

In this study, seventeen flavonol derivatives (1-17) were evaluated with regard to their first- and second-order hyperpolarizability parameters. For this purpose, the molecular geometries of 1-17 were optimized by using B3LYP/6-311++G(d,p) level. Spectroscopic characterizations for 1-17 were executed through the calculations of IR, UV-vis, ¹H NMR and ¹³C NMR spectra. The quantum chemical parameters such as electronegativity, chemical hardness, chemical potential and electrophilicity indexes were obtained by using the frontier molecular orbital (FMO) energies. The potential energy distribution (PED) analysis was used to provide a detailed assignment of vibrational bands. Important contributions to electronic absorption bands from FMOs were also evaluated. The distribution of FMOs to the whole molecule was investigated to determine the nature of electronic charge transfers in 1-17. The static and dynamic first- and second-order hyperpolarizability parameters for 1-17 were calculated by using B3LYP/6-311++G(d,p) level. The static β and γ were calculated at the ranges of 9.8279-0.0303 × 10^-29 esu and 80.200-268.40 × 10^-36 esu. The dynamic β and γ (ω = 532 nm) were also obtained in the field of 1.0440-71.786 × 10^-29 esu and 306.20-3607.00 × 10^-36 esu. This wide range of β and γ values indicate that flavonol derivatives with rational substitution may be promising candidates for first- and second-order NLO applications.