Reducing ESIPT energy barrier of [(E)-(2-hydroxyphenyl) methylidene] [(E)-pyrenylmethylidene] hydrazine by solvent polarity cooperates with intermolecular H-bonding interaction.

Excited-state intramolecular proton transfer (ESIPT) process as one of significant excited-state dynamic processes has been extensively applied in fluorescence probes, photoelectric sensors and fluorescence imaging fields. In this article, we regulated ESIPT energy barrier of [(E)-(2-hydroxyphenyl) methylidene] [(E)-pyrenylmethylidene] hydrazine (PMHMP) molecule via solvent polarity coorperates with intermolecular H-bonding utilizing time-dependent density functional theory method. Intramolecular H-bonding of PMHMP enhanced after being stimulated. Moreover, H-bonding strength enhances as solvent polarity increases. And intermolecular H-bonding interaction can further enhance intramolecular H-bonding strength. The potential energy curves reveal that increasing solvent polarity reduces ESIPT energy barrier and intermolecular H-bonding between PMHMP and methanol further reduces ESIPT energy barrier. Our study not only verified ESIPT for PMHMP can be regulated by solvent polarity cooperates with intermolecular H-bonding, but also explain previous experimental phenomenon reasonably. We hope our work can promotes further development of probe molecules in photochemical and biomedical fields.