A rotaxane made from a bisphenanthroline Cu-I complex and two C-60 units acting as stoppers has been synthesized, Electrochemical, spectroscopic and photophysical properties of the individual components, a methanofullerene and a Cu-I catenate, were determined. The properties of the methanofullerene were also compared with those of plain C-60 and rationalized with the aid of semiempirical calculations, The changes in the photophysical properties detected in the rotaxane with respect to the models were assigned to the occurrence of intramolecular processes. The excited singlet state localized on the fullerene and the MLCT excited state centred on the Cu-I complex are both quenched. Deactivation of the fullerene excited singlet state occurs by energy transfer to the Cu-I-complex moiety which competes with intersystem crossing to triplet fullerene, whereas the Cu-I-complex excited state is mainly quenched by electron transfer to form the charge-separated slate consisting of the oxidized metal centre [Cu(phen)(2)](2+) and the fullerene radical anion, The fullerene triplet, formed in reduced yield with respect to the model, is also quenched by electron transfer to the same charge-separated state. The ability of both model components to sensitize singlet oxygen is completely suppressed in the rotaxane. The occurrence of a fast back-electron-transfer reaction is postulated, as spectroscopic detection of the charge-separated state has not been achieved.
A copper(I)-complexed rotaxane with two fullerene stoppers: Synthesis, electrochemistry, and photoinduced processes.
Armaroli N;
1998
Abstract
A rotaxane made from a bisphenanthroline Cu-I complex and two C-60 units acting as stoppers has been synthesized, Electrochemical, spectroscopic and photophysical properties of the individual components, a methanofullerene and a Cu-I catenate, were determined. The properties of the methanofullerene were also compared with those of plain C-60 and rationalized with the aid of semiempirical calculations, The changes in the photophysical properties detected in the rotaxane with respect to the models were assigned to the occurrence of intramolecular processes. The excited singlet state localized on the fullerene and the MLCT excited state centred on the Cu-I complex are both quenched. Deactivation of the fullerene excited singlet state occurs by energy transfer to the Cu-I-complex moiety which competes with intersystem crossing to triplet fullerene, whereas the Cu-I-complex excited state is mainly quenched by electron transfer to form the charge-separated slate consisting of the oxidized metal centre [Cu(phen)(2)](2+) and the fullerene radical anion, The fullerene triplet, formed in reduced yield with respect to the model, is also quenched by electron transfer to the same charge-separated state. The ability of both model components to sensitize singlet oxygen is completely suppressed in the rotaxane. The occurrence of a fast back-electron-transfer reaction is postulated, as spectroscopic detection of the charge-separated state has not been achieved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
