Beiträge zur Chemie der Pyrrolpigmente, 79. Mitt. Zum strukturellen Einfluß stark raumerfüllender Reste bei 10-substituierten 1,19-Bilindionen

Summary 1,19-Bilindiones bearing a phenanthryl, mesityl,tert-butyl, and isopropyl substituent at the C-10 position were synthesized. Conformational analysis using¹³C- and¹H-NMR spectroscopic techniques and absorption spectroscopy together with semiempirical calculations revealed that the aryl derivatives adopt the common circular helical geometry, whereas thetert-butyl derivative is heavily distorted. The mean planes of the two dipyrrinone moieties are orthogonally positioned to each other. The 10-isopropyl-bilindione tautomerizes to the 10-isopropyliden-biladiene-ac.