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The longest wavelength VIS absorptions of the deeply colored CF 3 CO,H solutions of the 4,4′-chalcogenobis-(triphenylmethylium) ions 4 ++ , Y[C 6 H 4 C(C 6 H 5 ) 2 ] 2  (Y = O,S,Se,Te) resemble closely those of the corresponding monocationic 4-arylchalcogenotriphenylmethylium systems 5 + , ArYC 6 H 4 C(C 6 H 5 ) 2 , and not those of the structurally directly related 4,4′-bis(arylchalcogeno)triphenylmethylium ions 3 + , C 6 H 5 C(C 6 H 4 YAr) 2 . This is in striking contrast to the results obtained previously for analogous nitrogen systems, where “inverse”, 2 ++ , RN[C 6 H 4 C(C 6 H 5 ) 2 ], and “conventional” malachite green systems 1 + , (Ar 2 NC 6 H 4 ) 2 CR, yield almost indentical A max  values. A rationalization of these observations can be achieved based on the assumption of largely delocalized dications 2 ++  versus more or less orthogonal “double monocationic” systems 4B ++  separated due to torsional twist. Whereas the formal push-pull systems 6 + , ArSC 6 H 4 YC 6 H 4 C(C 6 H 5 ) 2  (Y = O,S,Se) behaved practically like the corresponding standard systems 5 + , the mono- and bis-triphenylmethylio-substituted dibenzofurane, dibenzothiophene and thioxanthene derivatives 8 + , 9 ++ , 10 +  and 11 ++  displayed hypsocromic shifts of their color bands relative to their noncyclic analogues which are only partly in accordance with predictions based on a simple frontier orbital Hückel model. The  1 H and  13 C NMR spectra of all these cationic species comply with their respective charges.

zeitschrift für naturforschung b

Chalcogeno-substituierte Triphenylmethylium-Ionen vom inversen Malachitgrün-Typ / Chalcogeno-Substituted Bis-triphenylmethylium Ions of the Inverse Malachite Green Type