Fluorescent molecular rotors (FMRs) of organoboron derived from Schiff bases and their multi-stimuli responsive

Abstract A series of bi-nuclear fluorescent Boron Schiff bases (BOSCHIBAs) bis(1-B)Ph ( 5 ), bis(2-B)Ph ( 6 ), bis(3-B)Ph ( 7 ), and bis(4-B)Ph ( 8 )) have been synthesized and the effects of temperature, pH, viscosity, and pressure on their fluorescence have been investigated. The compound 6 present a high response to various stimuli: shows 18 fold increase in fluorescence quantum yield with the increase in viscosity of the medium due to the restriction rotation at 90% glycerol. The boron compound 6 under basic conditions of pH the emission bands exhibited poor emission intensities and when the pH value is adjusted slightly below of neutral pH value, the fluorescence peak exhibited a hypsochromic shift from 421 to 400 nm. In state solid it compound was exposed to compression at 8t (t: metrics tons), its color changed from yellow to dark yellow and it was gradually lost its fluorescence property; this binuclear exhibit the property of reversible thermochromism. Compounds 5 – 8 have also been investigated using DFT. Computational work shows that the compound 6 has a free rotation about carbon-boron bond.