Journal of Theoretical and Computational Chemistry

The d${}^{10}\cdots {\text{d}}^{10}$ metallophilic host clusters [Au(NHC)₂]${}^{+}\cdots$ [M(CN)₂]${}^{-}\cdots$ [Au(NHC)₂]${}^{+}$(NHC $=$ N-heterocyclic carbene, $\mathrm{\text{M}}=\mathrm{\text{Au}}$, Ag) with high phosphorescence are synthesized recently and their phosphorescent modulation by solvents is investigated in theory. In this paper, the guest anions (F⁻, Cl⁻, Br⁻, NO${}_3^{-}$, and BF${}_4^{-})$ are used to elucidate their effects on metallophilic interactions and phosphorescence of hosts, and also they served as the probes to study the recognition characters of metallophilic hosts. The calculation shows that the guest anions can mutually interact with the host clusters and further, which can modulate the metallophilic Au$\cdots$M distances and the phosphorescence spectra of the hosts.

The Fourier transform infrared and Raman spectra of the adamantane-based compound ethyl 4-[3-(adamantan-1-yl)-4-phenyl-5-sulfanylidene-4,5-dihydro-1H-1,2,4-triazol-1-yl]methylpiperazine-1-carboxylate were recorded in the ranges of 3200–650cm${}^{-1}$ and 3200–150cm${}^{-1}$, respectively. The UV/Vis spectrum of solution of the title compound in ethanol was measured in the range of 450–200nm. The DFT calculations at the B3LYP/cc-pVDZ and B3LYP/cc-pVTZ levels of the theory were performed to obtain the equilibrium geometric structure and to predict vibrational IR and Raman spectra of the title molecule. The TDDFT calculations at the CAM-B3LYP/cc-pVTZ level of the theory, as well as MRPT calculations at the CASSCF(4,5)/XMCQDPT2 level of the theory were carried out to reproduce the electronic absorption spectrum. The experimental IR, Raman and UV/Vis spectra were interpreted on the basis of results of quantum chemical modeling. Based on Mulliken and Löwdin atomic population analysis, it was established that the compound under study exhibits features of an intramolecular charge transfer.

In the present investigation, for the first time, we have performed a thorough study about different functionals and basis sets for linear and nonlinear optical (NLO) properties of para-nitroaniline ($p$-NA), which is considered as proto-type NLO molecule, among organic NLO materials. There is a dire need of such data base for $p$-NA because many investigators are using such values of $p$-NA for comparative analysis. A range of different functionals including HF, BLYP, PW91, PBE, B3LYP, M06, M06-2X, PBE0, BHandHLYP, CAM-B3LYP, LC-BLYP, and B3LYP-D3 are applied in conjugation with several commonly basis sets such as 6-31G*, 6-311G*, 6-311G**, 6-311+G**, cc-pVDZ, and cc-pVTZ. A variety of functional and basis sets combinations are calculated and graphically compared with each other. The calculated total dipole moment for the $p$-NA is found to be 6.79D which is quite closer to experimentally determined value. The lowest calculated value for linear isotropic polarizability at HF/6-31G* level of theory is $11.74\times 10^{-24}$ esu while higher values observed with remaining all methods especially 14% polarizability increases in presence of basis set with diffuse functions and similar trend of variation is also observed in linear anisotropic polarizability. Similarly, the calculated value of frequency dependent second-order polarizability is found to be $9.59\times 10^{-30}$ esu at PBE0/6-311+G** level of theory which is quite closer to experimental value of $9.6\times 10^{-30}$ esu. A comparison between the calculated and experimental results shows good agreement among geometries, dipole moments and NLO polarizabilities for $p$-NA. Moreover, the frontier molecular orbital (FMO) and electron density difference map (EDDM) analysis along with density of state (DOS) plots are also presented to get more physical intuitions into the structure–property relationship and electronic communications between terminal accepter and donor groups through $\pi$-conjugation. The present investigation provides benchmark data including various commonly used functionals and basis sets for the calculation of NLO properties of $p$-NA. Thus, the present investigation will put straight several future studies when it comes to comparative NLO study of organic materials.

The Nitric Oxide Synthase inhibitory activity of two dietary phytocompounds naringenin and quercetin that belong to the family of flavonoids was studied by spectroscopic and computational methods. The determining role played by the global reactivity parameters that were calculated using spectroscopic and computational methods were correlated with the Nitric Oxide Synthase inhibitory activity by a Quantitative Structure–Activity Relationship (QSAR) study. The inter and intramolecular charge–transfer interactions responsible for the biological activity of naringenin and quercetin were studied using Natural Bond Orbital Analysis. The reactive sites of the title compounds were studied using their molecular electrostatic map. The likelihood of naringenin and quercetin to be a small drug molecule was determined by Lipinski’s rule. The molecular dynamics and docking studies were carried out to test the energetic and structural favorability of the inhibition of Nitric Oxide Synthase by small drug molecules naringenin and quercetin. Experimental cell culture-based in vitro assays were done to test theoretical predictions. A QSAR study revealed that for Nitric Oxide Synthase inhibitory activity to be better, the compounds belonging to the family of flavonoids ought to have a more negative ionization energy and chemical softness while bandgap and electrophilicity index ought to be more positive.