Molecular switch with pH-controlled absolutely switchable dual fluorescence

ORGN 593

Go Nishimura, Yasufumi Tokitoh, Yasuhiro Shiraishi, shiraish@cheng.es.osaka-u.ac.jp, and Takayuki Hirai. Research Center for Solar Energy Chemistry, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, 560-8531, Japan
Design and development of supramolecular systems with a switching function is an area of intense research activity. A vast variety of switches have been synthesized based on systems whose emission properties can be modulated by external input; however, most of these show only "on/off switching" function of single fluorescence emission. Herein, we describe a simple-structured molecule (L1), containing anthracene fragments at both ends of diethylenetriamine, behaves as a fluorescent molecular switch with pH-controlled absolutely switchable dual-mode fluorescence; each mode consists of monomer (pH < 9) and excimer (pH > 9) emissions, where the latter mode is "on" according to the formation of the intramolecular change transfer (ICT) complex in the ground state, via pH-induced pi-stacking interaction of two fluorophores and solvation of water molecules.