A diamine ligand with long “arms” and its corresponding dinuclear rhenium(I) complex: Synthesis, characterization, photophysical property, and sensing activity towards molecular oxygen

In this paper, we synthesize a novel diamine ligand of 4,7-dinonadecyl-1,10-phenanthroline (DN-Phen) with two long alkyl chain arms serving as a shield and its corresponding dinuclear Re(I) complex of Re2(CO)6(bpy)(DN-Phen)2 (bpy=4,4′-bipyridine), aiming at an optical sensor immune to the surrounding interferences. Its geometric and electronic structures are investigated, which suggest that the introduced long alkyl chains act as a shield for the excited state of emissive center. The promising photophysical parameters of Re2(CO)6(bpy)(DN-Phen)2, including the immunity of emission towards the surrounding interferences and long excited state lifetime, make itself a potential probe for oxygen detection. By doping Re2(CO)6(bpy)(DN-Phen)2 into two silica matrixes of MCM-41 and SBA-15, oxygen sensing performances of the resulted composite materials are investigated. Finally, a high sensitivity of 20.1 is realized, with short response/recovery time of 8 s/42 s. Here, sensitivity is defined as the ratio of emission maximum under pure nitrogen to emission minimum under pure oxygen, response and recovery times are the times for a sample to lose (response time) or recover (recovery time) 95% of its emission maximum upon periodically changed atmosphere.