V. Kannappan

Ultrasonic, spectrophotometric and theoretical studies of sigma and PI interactions of iodine with substituted benzene

The charge transfer (CT) interaction between three structurally different benzenoid compounds (donors), namely, chlorobenzene (1), phenol (2), anisole (3), and iodine (I2, acceptor) were investigated by experimental methods (ultrasonic and UV-Visible analysis) and theoretical calculations. Notably, strong solute–solute interactions and the existence of a CT type of interaction between 1–3 and I2 is clearly analyzed from the trend in acoustical and excess thermo acoustical parameters with concentration at 303 K in an n-hexane medium. The formation of 1 : 1 complexes between iodine and 1–3 was established by the UV-visible spectroscopic method. The structure and stabilization energies of 1–3 and I2 were further calculated by DFT calculations. Among the σ- and π-type interactions, a π-type complex (1a–3a) with an atom-centered orientation is found to be the preferred and stable geometry for all the CT complexes. The stability constant of the CT complexes was calculated by spectroscopic and ultrasonic methods, which show a similar trend with the DFT computed stabilization energies. Furthermore, AIM and NBO analyses were used to quantify the nature of the stabilizing interactions that exist in 1–3 and the I2 CT complexes. Our computed results are in good agreement with the experimental observations.

Ultrasonic studies on the molecular interaction of gallic acid in aqueous methanol and acetone solutions and the role of gallic acid as viscosity reducer

Abstract Gallic acid (GA), a basic structural unit of hydrolysable tannin has been chosen as a model compound to investigate the solute-solvent interactions in polar media and to obtain clear insight into the more scientific facts in the extraction of hydrolysable tannins from plant source. Ultrasonic velocities (u), densities (ϱ), and viscosities (η), are measured for aqueous methanol and aqueous acetone solutions of GA in the temperature range 20–40°C. Acoustical parameters such as characteristic impedance (Z), adiabatic compressibility (β), free volume (V f ), internal pressure ( π i ), available volume (V a ), absorption coefficient (α/f 2 ), viscous relaxation time (τ), free length (L f ), molecular interaction parameter (χ) and cohesive energy are calculated for these solutions to study solute-solvent interactions. An attempt has been made to optimise the condition for efficient extraction of GA from the results obtained in acoustical and viscosity studies. Interestingly, it has been found that GA functions as viscosity reducer for aqueous acetone at a characteristic composition.

Hydrogenation of dinitrogen to ammonia in [WF(PH2(CH2)2PH2)2N2] using H2: Insights from DFT calculations

A new methodology has been proposed to reduce the molecular dinitrogen to ammonia in [WF(PH2(CH2)2PH2)N2] (1) and tested for thermodynamic feasibility by DFT calculations in three different solvents. The calculated barriers for 1 revealed that N2 can be reduced by H2 in organic solvents.

Structural Analysis and Reactivity of Tetramethylcopper(III) Complex towards Nitrogen Donor Ligands by Density Functional Theory

DFT studies are carried out on some ligand substitution reactions of tetramethylcuprate(III) (TMC) complex with five different nitrogen donor ligands as probe ligands. The geometry optimization of the possible nine model systems and the frequency calculations are carried out at DFT level using LANL2DZ basis set. The selected structural parameters of optimized model systems of Cu(III) complexes are reported and discussed. The change in the M-C bond distance in TMC due to substitution by probe ligands is explained. Natural population analysis (NPA) has been carried out for these complexes to establish the charge of copper in these complexes. A detailed population analysis of valence orbitals of copper complexes supports the existence of d8 configuration for metal in complexes and there is evidence for the transmission of electrons from the nitrogen donor atom to , , and 4s orbitals. Bond order calculations have been performed for all the complexes to probe the interaction between Cu(III) and the ligand. The stability of the complexes is ascertained from the computed chemical hardness. In order to understand the nature of Cu(III)-L (L = N donors) and Cu(III)-Me bonds in different complexes, Energy Decomposition Analysis (EDA) has been carried out for all the complexes chosen in the theoretical study. Thermodynamic feasibility of these reactions is investigated in terms of free energy changes of these reactions.