title: Noncovalent interactions from electron density topology and solvent effects on spectral properties of Schiff bases.
abstract: Two Schiff bases were prepared by the condensation of o-allyl substituted 2,4-dihydroxy acetophenone with 1,2-diaminopropane (L1) and ethanediamine (L2) and characterized by elemental analysis, and ESI-MS, IR, UV-Vis,1H and13C NMR spectral techniques. The effect of solvents with respect to different polarities on UV-Vis and emission spectra of L1 and L2 was investigated at room temperature show that the compounds exist in keto and enol forms in solution and may be attributed to the intramolecular proton transfer in the ground state. The solute-solvent interactions, change in dipole moment and solvatochromic properties of the compounds were studied based on the solvent polarity parameters. For L1 and L2, the ground and excited state electronic structure calculations were carried out by DFT and TD-DFT at B3LYP/6-311G (d,p) level, respectively. The IR, NMR and electronic absorption spectra computed were compared with the experimental observations. The intramolecular charge transfer within the molecule is evidenced from the HOMO and LUMO energy levels and surface analysis. The noncovalent interactions like hydrogen bonding and van der Waals interactions were identified from the molecular geometry and electron localization function. These interactions in molecules have been studied by using reduced density gradient and graphed by Multiwfn.
authors.affiliation: Chemistry Research Centre, National Engineering College, K.R. Nagar, Kovilpatti, 628503 Thoothukudi District, Tamil Nadu, India; Department of Chemistry, Sri Paramakalyani College, Alwarkurichi, 627412 Tirunelveli District, Tamil Nadu, India.
authors.forename: S
authors.initials: S
authors.lastname: Gandhimathi
authors.affiliation: Chemistry Research Centre, National Engineering College, K.R. Nagar, Kovilpatti, 628503 Thoothukudi District, Tamil Nadu, India.
authors.forename: C
authors.initials: C
authors.lastname: Balakrishnan
authors.affiliation: Chemistry Research Centre, National Engineering College, K.R. Nagar, Kovilpatti, 628503 Thoothukudi District, Tamil Nadu, India.
authors.forename: M
authors.initials: M
authors.lastname: Theetharappan
authors.affiliation: Chemistry Research Centre, National Engineering College, K.R. Nagar, Kovilpatti, 628503 Thoothukudi District, Tamil Nadu, India. Electronic address: drmaneelakantan@gmail.com.
authors.forename: M A
authors.initials: MA
authors.lastname: Neelakantan
authors.affiliation: Department of Chemistry, Sri Paramakalyani College, Alwarkurichi, 627412 Tirunelveli District, Tamil Nadu, India.
authors.forename: R
authors.initials: R
authors.lastname: Venkataraman
keywords: DFT and TD-DFT; Electron localization function; Reduced density gradient; Schiff bases; Solvatochromism