Theoretical Study Of Excited State Intramolecular Proton Transfer Process For HPI-Ac Molecular

The excited state intramolecular proton transfer(ESIPT)process refers to the isomerization process in which protons transfer from donor to acceptor after the molecular upon to the excited state.This process is one of the hot issues in the field of atomic and molecular physics.These molecules have been widely used to design and develop the organic luminescent materials,fluorescent probes.The proton transfer undoubtedly leads to the redistribution of charge in the whole molecule,which changed the interaction between the molecule and its surrounding solvent.In this work,density functional theory(DFT)and time-dependent density functional theory(TDDFT)methods were employed to investigate the different influence mechanisms of hydroxyl-substituted tetraphenyclimidazole acetate-containing derivative(HPI-Ac)molecules on the ESIPT process in non-polar solvent chloroform(CHCl3)and strong proton affinity solvent dimethylsulfoxide(DMSO).The optimized geometric structure and electrostatic potential distinctly indicated that the intermolecular hydrogen bonding was formed between the HPI-Ac and the DMSO solvent.Based on the optimized HPI-Ac and HPI-Ac-DMSO hydrogen bond complexes in the ground state(S0 state)and excited state(S1 state)geometries,we analyzed the corresponding hydrogen bond lengths.Moreover,the analysis of absorption and fluorescence spectra,frontier molecular orbitals(MOs),potential energy curves and infrared(IR)vibration spectra of the HPI-Ac and HPI-Ac-DMSO hydrogen bond complexes.Our results indicate that upon photo-excitation intramolecular H-bonding strengthen to promote the ESIPT reaction of HPI-Ac monomer,while DMSO has a great proton affinity likely to break the intramolecular H-bonding,concomitantly with forming an intermolecular H-bonding to restrain the ESIPT process of HPI-Ac-DMSO complex.