Induced Circular Dichroism and Structural Assignment of the Cyclodextrin Inclusion Complexes of Bicyclic Azoalkanes

• Published in: Journal of organic chemistry 2005-01, Vol.70 (1), p.39-46
• Main Authors: Bakirci, Hüseyin, Zhang, Xiangyang, Nau, Werner M
• Format: Article
• Language: English
• Subjects: Azo Compounds - chemistry; Bridged Bicyclo Compounds, Heterocyclic - chemistry; Chemistry; Circular Dichroism; Cyclodextrins - chemistry; Exact sciences and technology; Fluorometry; General and physical chemistry; Magnetic Resonance Spectroscopy; Molecular Conformation; Solution properties; Solutions; Spectrophotometry, Ultraviolet; Stereoisomerism; Thermodynamics
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo048420k

The stoichiometries and binding constants of the host−guest complexes between the bicyclic azoalkanes 1−6 and α-, β-, and γ-cyclodextrins (CDs) and the induced circular dichroism (ICD) of the complexes were analyzed. Assisted by proximity relationships obtained from 2D ROESY NMR spectra, the signs and intensities of the ICD spectra are interpreted in terms of the solution structures (co-conformations) of the CD complexes. The ICD assignments are based on the orientation-intensity ICD rules of Harata and Kodaka, which relate the ICD signs and intensities to the relative orientation of the electric dipole transition moment of the n,π* azo chromophore to the CD axis. The influence of the size of the guest and the host is discussed and the effect of introducing an additional chromophore (either a phenyl or a second azo group) on the ICD spectra is demonstrated.