Enantioselective gel collapsing: a new means of visual chiral sensing

An optically active BINOL-terpyridine based Cu(II) complex (R)-2 was prepared. Sonication of (R)-2 in CHCl(3) led to the formation of a stable gel. The interaction of this gel with chiral amino alcohols was studied. It was found that (S)-phenylglycinol (0.10 equiv) could break the gel network of (R)-2 (3.75% w/v, g/mL) in CHCl(3) to cause gel collapsing but (R)-phenylglycinol (0.10 equiv) could not. Similar enantioselective gel collapsing was also observed with (R)- and (S)-1-amino-2-propanol. This study demonstrates that chiral molecular gels are potentially useful for visual chiral discrimination. Complex (R)-2 in solution also exhibited significant enantioselective fluorescent enhancement in the presence of a variety of amino alcohols.