CONTROL OF THE J-AGGREGATION PHENOMENON BY VARIATION OF THE N-ALKYL-SUBSTITUENTS .5.

Cyanine dyes (1a-d) with the 5,5',6,6'-tetrachloro-1,1'-dialkyl-3,3'-di-(3-carboxypropyl)-benzimidocarbocyanine chromophore differing only in the chain length of their alkyl groups in 1,1'-position have been synthesized, spectroscopically characterized, and compared with 5,5',6,6'-tetrachloro-1,1'-diethyl-3,3'-di-(4-sulfobutyl)-benzimidocarbocyanine (TDBC). In aqueous solution the dyes form J-aggregates which, depending on the alkyl group chain length, exhibit J-bands differing in spectral position, bandwidth, and in the number of peaks.