Synthesis, X-ray structure, spectroscopic properties and DFT studies of a novel Schiff base

Int J Mol Sci. 2014 Oct 17;15(10):18706-24. doi: 10.3390/ijms151018706.

Abstract

A series of Schiff bases, salicylideneaniline derivatives 1-4, was synthesized under mild conditions and characterized by 1H NMR, HRMS, UV-Vis and fluorescence spectra, and single-crystal X-ray diffraction. In solid and aprotic solvents 1-4 exist mainly as E conformers that possess an intramolecular six-membered-ring hydrogen bond. A weak intramolecular C-H···F hydrogen bond is also observed in fluoro-functionalized Schiff base 4, which generates another S(6) ring motif. The C-H···F hydrogen bond further stabilizes its structure and leads it to form a planar configuration. Compounds 1-3 exhibit solely a long-wavelength proton-transfer tautomer emission, while dipole-functionalized Schiff base 4 shows remarkable dual emission originated from the excited-state intramolecular charge transfer (ESICT) and excited-state intramolecular proton transfer (ESIPT) states. Furthermore, the geometric structures, frontier molecular orbitals (MOs) and the potential energy curves for 1-4 in the ground and the first singlet excited state were fully rationalized by density functional theory (DFT) and time-dependent DFT calculations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aniline Compounds / chemical synthesis
  • Aniline Compounds / chemistry*
  • Crystallography, X-Ray
  • Hydrogen Bonding
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Quantum Theory
  • Schiff Bases / chemical synthesis
  • Schiff Bases / chemistry*
  • Spectrophotometry, Ultraviolet

Substances

  • Aniline Compounds
  • Schiff Bases
  • salicylideneaniline