화학공학소재연구정보센터
International Journal of Molecular Sciences, Vol.15, No.10, 18706-18724, 2014
Synthesis, X-ray Structure, Spectroscopic Properties and DFT Studies of a Novel Schiff Base
A series of Schiff bases, salicylideneaniline derivatives 1-4, was synthesized under mild conditions and characterized by H-1 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 center dot center dot center dot F hydrogen bond is also observed in fluoro-functionalized Schiff base 4, which generates another S(6) ring motif. The C-H center dot center dot center dot 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.