LAUSR

Two high efficient excited state intramolecular proton transfer (ESIPT) compounds (i.e., 3-(5-([1,1′-biphenyl]-4-yl)oxazol-2-yl)-4′-(N,N-diphenylamino)-[1,1′-biphenyl]-4-ol (1) and 4′-(N,N-diphenylamino)-3-(5-(4′-(diphenylamino)-[1,1′-biphenyl]-4-yl)oxazol-2-yl)-5-methyl-[1,1′-biphenyl]-4-ol (2)) are explored theoretically. Based on DFT and time-dependent DFT (TDDFT) methods, we investigate the hydrogen bonding interactions and ESIPT mechanism. Via B3LYP/TZVP/IEFPCM (toluene) theoretical level, we reappear the experimental steady-state spectra, which demonstrate that the theoretical manner is reasonable and effective. Based on reduced density gradient (RDG) versus sign(λ2)ρ analyses, we confirm intramolecular hydrogen bond for both 1-enol and 2-enol. Investigating geometrical parameters and infrared (IR) vibrational spectra, we verify the O-H···N should be strengthened in the S1 state for 1-enol and 2-enol systems. Exploring frontier molecular orbitals (MOs) and charge density difference (CDD) maps, we find charge redistribution provides the tendency of ESIPT. The constructed potential energy curves demonstrate that the proton transfer should happen in the S1 state. Particularly, the low potential energy barriers of forward and backward ESIPT process for both 1 and 2 systems, the dynamical equilibrium could be verified, which means 1 and 2 systems should be potential for novel white light LEDs materials. This work not only explores and explains previous experimental phenomenon, but also makes a reasonable assignment about the ESIPT mechanism.