Spin-orbit coupling in sulphur-containing purine and pyrimidine derivatives. A comparison of caffeine and 6-thiocaffeine

✍ Scribed by G. Lancelot; C. Helene

• Book ID: 103013073
• Publisher: Elsevier Science
• Year: 1971
• Tongue: English
• Weight: 581 KB
• Volume: 9
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(71)80232-4

✦ Synopsis

Replacing

an oxygen atom of caffeine by a sulphur atom leads to a red-shift of the absorption spectrum. a quenching of fluorescence, an incrcnse in the phosphorescence quantum yield and a drastic shortening of the phosphorcecence lifetime. Polarization studies sh;w that phosphorescence transitions from the triplet states of cnffoinc and 6-thiocaffeine are mainly polarized perpendicular to and in the moIecular plane, respectively. Several mcchantunw of spin-orbit cnuplhg arc propmod to cxpb_in the obwrvcd differences. The possible role of sulphur d-orbitals is suggested.