Chiral assembly of achiral pseudoisocyanine with D- and L-phenylalanine

Supramolecular chirality and molecular self-assembly are important and interesting phenomena in living and non-living systems. In this work, supramolecular chirality of achiral pseudoisocyanine (PIC) J-aggregates was successfully induced by D-, L-phenylalanine (Phe) and other amino acids in NaCl solution. The chiral J-aggregates showed a characteristic, induced circular dichroism (ICD) in the visible region of J-band chromophore which depends on the absolute configuration, concentration and side groups of α-amino acids, as well as temperature. The atomic force microscopy images indicated that the J-aggregates exist in large bundles of entangled nanofibers, and the observed ICD might result from the macroscopic helical arrangement of the assemblies. Supported by the National Natural Science Foundation of China (Grant Nos. 20571085, 20604033 & 20877099), the Fund of the State Key Laboratory of Natural and Biomimetic Drugs (Grant No. 20080208), Graduate University of Chinese Academy of Sciences (Grant No. 2007-2009) and Jiangsu Provincial Key Laboratory of Organic Chemistry Foundation and Natural Science Foundation of Jiangsu Province (Grant No. BK2007047).