Investigating Solvent-Induced Changes in Structure and Nonlinear Optical Behavior of Thiazine Derivatives

In this study, we examine the effects of solvent media on the structural and optical behaviors of two isomers of thiazine derivatives: rac-2-(4-nitrophenyl)-3-phenyl-2,3,5,6-tetrahydro-4H 1,3 thiazin-4-one and (2S)-2-(3-nitrophenyl)-3-phenyl-2,3,5,6-tetrahydro-4H-1,3-thiazin-4 one. The solvent effects were modeled using the polarizable continuum model through density functional theory. Electrical parameters for rac-2-(4-nitrophenyl)-3-phenyl-2,3,5,6-tetrahydro-4H 1,3-thiazin-4-one and (2S)-2-(3-nitrophenyl)-3-phenyl-2,3,5,6-tetrahydro-4H-1,3-thiazin-4 one were determined using the density functional theory at the CAM-B3LYP/6-311+G(d) level. We studied the influence of isomer structures in various solvent media on the Hyper-Rayleigh-Scattering first hyperpolarizability, considering both static and dynamic scenarios. This research particularly emphasizes the implications of relocating the NO₂ group from the meta-position (2S)-2-(3-nitrophenyl)-3-phenyl-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-one to the para-position rac-2-(4-nitrophenyl)-3-phenyl-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-one on molecular geometries, linear and nonlinear optical parameters, and gap energies across different solvent media. Bond dissociation energy calculations for hydrogen atoms and all other single acyclic bonds were performed for both derivatives to assess degradation and autoxidation properties. Additional insights from non-bonding orbitals, molecular electrostatic surface potential, Fukui calculations, electron localization function, and localized orbital locator are detailed.

Keywords:
Hyper-Rayleigh-Scattering first hyperpolarizability; electrostatic surface potential; electron localization function; localized orbital locator