Theoretical study of substituents effects on characteristics of resonance-assisted hydrogen bond in (Z)-(thionitrosomethylene)hydrazine and its derivatives in ground and electronic excited state

Abstract

The molecular geometry, intramolecular hydrogen bond strength, vibrational frequencies, 1H NMR chemical shift, and nuclear quadrupole resonance parameters of 14N, 35S and 2H atoms and several well-established indices of aromaticity in (Z)-(thionitrosomethylene)hydrazine molecule and its derivatives were studied by density functional theory method. The results of calculations were obtained at B3LYP/6-311++G** level of approximation on model species, with the resonance-assisted hydrogen bonds. A set of simple and mostly common substituents having different properties in resonance effect according to values of substituents constants were chosen to simulate the influence of substitution in R position of title molecule on the quasi-delocalization and H-bonding. The following substituents have been taken into consideration: F, Cl, NO2, OCH3, OCF3, SCH3, SH, and OH. The excited-state properties of intramolecular hydrogen bonding in substituted systems have been investigated theoretically using the time-dependent density functional theory method. Also, the possible charge transfer and the topological properties of investigated molecule and its derivatives were studied by means of natural bond orbital and atoms in molecules (AIM) theory. The energy of the N–H···S interactions studied here was found medium in strength ( $$ E_{\text{HB}}^{*} $$ = −36.5 to −45.3 kJ mol−1). The electron density (ρ), Laplacian (∇2 ρ) properties and the total electron energy density (HC), estimated by AIM calculations, indicate that H···S bond possesses low ρ, positive ∇2 ρ and HC < 0 which are in agreement with partially covalent character of HB.