ISSN:
1434-4475
Keywords:
Association
;
Bilirubin and derivatives
;
Tautomerism
;
Variable temperature UV-VIS spectra
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract ByLambert−Beer-experiments at different temperatures in the range from 290 to 80K of solutions containing Bilirubin (2), its dimethylester3, its dimethoxydimethylester derivative4 and aetiobilirubin-IV-γ (1) in 2-methyltetrahydrofurane the preponderance of an association equilibrium determining the spectral changes upon cooling in the case of1 and3 was deduced. By protonation studies of partial structures5 and6 as well as of the integral pigments3 and4 the lactam-lactim equilibrium was proved to be on the side of the lactam tautomer at low temperatures as well. Upon cooling a zwitterionic species was detected in case of compound2. The conformational aspects in cases where a disturbance by the equiblibria given above could be ruled out are discussed. A warning is given to use low temperatures measurements of absorption and luminescence properties to gain structural and photochemical informations without previously establishing the nature of the solutions very carefully.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00814344
