Salen and [Al(salen)(H2O)2]+: The combination model of organic AIEgen and metal complex self-assembly

Abstract

Salen demonstrates aggregation-induced emission (AIE) effect in aqueous solution and solid state with green fluorescence (salen=N,N′-Ethylenebis(salicylimine)). The reaction of salen with Al3+ results in [Al(salen)(H2O)2]+ directly. [Al(salen)(H2O)2]+ exhibits an obvious assembly phenomenon: monomer exists in organic solution with blue fluorescence while self-assembly polymer forms in aqueous solution and crystal state emitting green fluorescence, we rename it as Restriction of Coordinated Water Motions (RCWM) effect. Moreover, the self-assembly of [Al(salen)(H2O)2]+ has been observed in different part of cells: green fluorescence in hydrophilic region and blue fluorescence in hydrophobicity region in the same time. The photophysical processes are verified by fluorescence spectra, ESI–MS, X-ray diffractometer. ESIPT effect of salen and fluorescence spectra of [Al(salen)(H2O)2]+ have been certified by theoretical calculation. Therefore, salen and [Al(salen)(H2O)2]+ can act as an ideal model for the combination of organic AIEgen and metal complex self-assembly both in aqueous solution and crystal state.