Synthesis and Photoinduced Electron‐Transfer Properties of Phthalocyanine–[60]Fullerene Conjugates

Abstract

A series of three novel ZnPc-C60 conjugates (Pc=phthalocyanine) 1 a-c bearing different spacers (single, double, and triple bond) between the two electroactive moieties was synthesized and compared to that of ZnPc-C60 conjugate 2, in which the two electroactive moieties are linked directly. The synthetic strategy- towards the preparation of 1 a-c- involved palladium-catalyzed cross-coupling reactions over a monoiodophthalocyanine precursor 4 to introduce the corresponding spacer, and subsequent dipolar cycloaddition reaction to C60. Detailed photophysical investigations of 1 a-c and 2 prompted an intramolecular electron transfer that evolves from the photoexcited ZnPc to the electron-accepting C60. In particular, with the help of femtosecond laser photolysis charge separation was indeed confirmed as the major deactivation channel. Complementary time-dependent density functional calculations supported the spectral assignment, namely, the spectral identity of the ZnPc(*+) radical cation and the C60 (*-) radical anion as seen in the differential absorption spectra. The lifetimes of the correspondingly formed radical ion-pair states depend markedly on the solvent polarity: they increase as polarity decreases. Similarly, although to a lesser extent, the nature of the linker impacts the lifetime of the radical ion-pair states. In general, the lifetimes of these states tend to be shortest in the system that lacks any spacer at all (2), whereas the longest lifetimes were found in the system that carries the triple-bond spacer (1 a).

Roles of Molecular Wires between Fullerenes and Electron Donors in Photoinduced Electron Transfer

“…1 © 10 8 s ¹1 in toluene at RT. 37 This trend is consistent with Marcus theory, predicting that instability of ZnPc…”

“…On the other hand, phthalocyanine (ZnPc) and C 60 dyads with acetylene bridges have been recently reported by Quintiliani et al 37 Quite fast intramolecular CS and CR processes were evaluated. The rate constants for CS and CR of ZnPcacetyleneC 60 , in which the acetylene moiety is directly connected to both ZnPc and C 60 , are almost the same as those of the indirect connection cases (i.e., insertions of an ethane linkage), suggesting that CS and CR take place via the superexchange mechanism.…”

A Bis(C60)–Bis(phthalocyanine) Nanoconjugate: Synthesis and Photoinduced Charge Transfer

“…[15] When relating the lifetimes of the radical-ion-pair state in 1 with those measured for comparable ZnPc-C 60 dyads, a stabilizing trend is only seen relative to systems that carry either no spacer or short spacers (i.e., single, double, or triple bonds). [16] In this case, the stabilization is as large as an order of magnitude. However, a destabilizing trend is noted when systems that contain aromatic spacers (i.e., [2,2]paracyclophane-vinylene or phenylene-vinylene) are considered.…”

Synthesis and characterization of novel fluoroether-substituted phthalocyanines

“…All the phthalocyanines were obtained by the cyclotetramerization of a phthalonitrile and synthesized according to reported methods [39][40][41][42][43][44][45][46]. The synthesis of both the octa and tetra substituted metal phthalocyanines (1a-3a, 1b-3b, 1d-3d) was achieved in anhydrous amyl alcohol using 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) as a base in the presence of anhydrous zinc(II) acetate, cobalt(II) chloride or nickel(II) chloride, respectively, at 140 8C under an argon atmosphere (Fig.…”