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Chirality inversion in the bilirubin molecular exciton
Author(s) -
Boiadjiev Stefan E.,
Lightner David A.
Publication year - 2001
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.1027
Subject(s) - chemistry , chirality (physics) , circular dichroism , exciton , cotton effect , spectroscopy , amine gas treating , stereochemistry , crystallography , physics , condensed matter physics , quantum mechanics , chiral symmetry , organic chemistry , nambu–jona lasinio model , quark
Abstract The bichromophoric pigment bilirubin acts as a molecular exciton in its UV‐visible and circular dichroism (CD) spectroscopy. In both polar and nonpolar solvents, an optically active analog, (β R, β′ R )‐dimethylmesobilirubin‐XIIIα ( 1 ), exhibits intense bisignate CD Cotton effects in the region of its long wavelength UV‐vis absorption near 400 nm: Δϵ 434 max+ 337, Δϵ 389 max− 186 (CHCl 3 ), and Δϵ 431 max+ 285, Δϵ 386 max− 177 (CH 3 OH). However, introduction of an amine into a CHCl 3 solution of 1 causes the Cotton effect signs to become inverted, e.g., after addition of NH 3 , Δϵ 433 max− 345, Δϵ 389 max+ 243, and after addition of ethylene diamine, Δϵ 435 max− 420, Δϵ 390 max+ 299. The sign inversions imply inversion of molecular chirality of the bilirubin and the phenomenon appears to be general for amines, including α,ω‐diamines. 1,8‐Diaminooctane was found to be more effective than longer or shorter chain analogs in producing CD sign inversion. Chirality 13:251–257, 2001. © 2001 Wiley‐Liss, Inc.