Theoretical calculation of circular dichroic exciton-split spectra in presence of three interacting 2-naphthoate chromophores.
Ample experimental evidence shows that the principle of pairwise additivity holds in exciton coupled CD systems consisting of three or more interacting chromophores. This principle is one of the most important from a practical viewpoint. However, the rule has so far not been proven theoretically. In order to prove the additivity principle by calculation, three ouabagenin bisnaphthoates and 1,3,19-tris-naphthoates were chosen as models. Since this represents a challenging case where the 2-naphthoate chromophore can adopt s-cis or s-trans conformations and, moreover the C-19 side chain of ouabagenin is flexible, Monte Carlo conformational search was performed prior to the CD calculation. The pi-electron SCF-CI-DV MO calculation of CD was applied to all conformers within 3 kcal/mol range from the lowest energy. Good agreement between experimental and theoretical CD spectra was obtained for the ouabagenin bisnaphthoates and trisnaphthoate.
Dong
J G
JG
Department of Chemistry, Columbia University, New York, NY 10027, USA.
Akritopoulou-Zanze
I
I
Guo
J
J
Berova
N
N
Nakanishi
K
K
Harada
N
N
D002264:Carboxylic Acids / Q000737:chemistry; D002942:Circular Dichroism; D008958:Models, Molecular; D009010:Monte Carlo Method; D009281:Naphthalenes / Q000737:chemistry; D010042:Ouabain / Q000031:analogs & derivatives* / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
D002264:Carboxylic Acids; D009281:Naphthalenes; C085312:1-naphthoic acid; D010042:Ouabain; C008721:ouabagenin