The alkoxylation effects on the excited‐state intramolecular proton transfer behaviors for 2,6‐bis(benzothiazolyl‐2‐yl)phenol fluorophore: A theoretical research

Abstract

AbstractGiven the unique luminescent properties, the excited‐state intramolecular proton transfer (ESIPT) materials have attracted lots of eyes in recent years. In view of the promising highly efficient red‐emitting material, the 2,6‐bis(benzothiazolyl‐2‐yl)phenol (DBTP) under alkoxy groups at the 4‐position reveals important properties. In this work, modification of DBTP fluorophore, that is, DBTP‐OMe (methoxy), DBTP‐OEt (ethoxy), DBTP‐OPr (propoxy), and DBTP‐OBt (butoxy) derivatives, have been explored theoretically. Based on the analyses of chemical structural variations and infrared (IR) vibrational spectra in both S0 and S1 states, the enhanced intramolecular hydrogen bonding interactions could be clearly found, which will promote the ESIPT tendency. Particularly, the DBTP‐OMe with stronger hydrogen bond reveals the easier PT tendency upon photo‐induced excitation. Paying attention to the changes of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), it could be found the charge transfer happens in the excited‐state molecules, and the reorganization of charge densities should be conducive to promoting the ESIPT process. Simulated potential energy curves indicated the ultrafast ESIPT reaction occurs for DBTP‐OMe, DBTP‐OEt, DBTP‐OPr, and DBTP‐OBt derivatives. The searched transition state (TS) structures in S1‐state reaction path suggested the derivatives with few alkyl groups might be more probe to occur the ESIPT reaction than the more alkyl ones for DBTP system.