Premium
Chiral polymethine dyes, IV. Synthesis, absolute configuration, spectroscopic and chiroptical properties of chiral tri‐ and pentamethinium cyanine dyes with 1,2,3,4‐tetrahydro‐6‐methylquinolyl end groups
Author(s) -
Reichardt Christian,
Harms Klaus,
Kinzel Manuela,
Schäfer Gerhard,
Stein Jörg,
Wočadlo Sigrid
Publication year - 1995
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199519950240
Subject(s) - cyanine , chemistry , absolute configuration , merocyanine , diastereomer , stereochemistry , optical rotation , photochemistry , fluorescence , organic chemistry , photochromism , physics , quantum mechanics
We have repeated and significantly improved the syntheses of the symmetrical tri‐ and pentamethinium cyanine dyes 10 and 11 in their monochiral forms ( 10a, b; 11a, b ) and in the meso form ( 11d ) as well as of the unsymmetrical monochiral pentamethinium cyanine dye 14a , first realized by König and Langbein in 1928. Their spectroscopic properties have been studied for the first time. The monochiral starting compounds 4a , b , and hence all related monochiral polymethine dyes, have been obtained with high enantiomeric excess (e.e. >99%) by recrystallization of their diastereomeric 3‐bromocamphor‐8‐sulfonates 6a , b. The absolute configuration of 4a , b , and thus the absolute configuration of all monochiral polymethine dyes derived from 4a , b , has been determined by X‐ray structural analyses of the tetrahydroquinolinium perchlorate 7a and the pentamethinium bromide 11a . Partial hydrolysis of the monochiral pentamethinium dye 11a gave the monochiral pentamethine merocyanine dye 12a , which was allowed to react either with 13 to yield the unsymmetrical monochiral pentamethinium dye 14a or with monochiral 7b to afford the symmetrical achiral meso ‐pentamethinium dye 11d . The pentamethinium cyanine dyes 11a , b , d and 14a were used to examine the proposed additivity in calculating the overall molecular optical rotation of 11a , b (Table 1).