A Copper( I )‐Complexed Rotaxane with Two Fullerene Stoppers: Synthesis, Electrochemistry, and Photoinduced Processes

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 state 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.

Photoactive mono- and polynuclear Cu(i)–phenanthrolines. A viable alternative to Ru(ii)–polypyridines?

“…36 This makes it an attractive partner for [Cu(NN) 2 ] + in the design of photoactive multicomponent systems.…”

“…36 Remarkably, the typical excited state properties of each moiety are strongly quenched, e.g. MLCT emission of the [Cu(NN) 2 ] + core, C 60 fluorescence, and the C 60 triplet absorption.…”

Factors affecting the threading of axle molecules through macrocycles: Binding constants for semirotaxane formation

“…Thereafter, the anchor group may or may not be removed. Early studies used templates featuring metal ion as anchors, as exemplified by the elegant rotaxanes of Gibson (14) and of Sauvage (15) and their coworkers (Fig. 2).…”

Novel Electron Donor Acceptor Nanocomposites

“…As donors a wide variety of chromophores including porphyrins [35][36][37][38][39][40][41][42][43][44][45], phthalocyanines [46,47], amines [48], polycondensed aromatics [49], transition complexes [50][51][52], carotenoids [53], ferrocenes [54,55], tetrathiafulvalenes (TTF) [56], and others [57] have been employed. Here the photodynamics of zinc porphyrin-C 60 linked dyad 1 is presented to understand the typical relaxation processes of the excited states in donor-fullerene linked dyads (Figure 4.1) [37].…”