Photoinduced electron transfer processes in three component rotaxanes with porphyrins, [60]fullerene and triphenylamine

Abstract

Electron transfer processes occurring through-space and through-bond were studied for novel mechanically linked triad [2]rotaxanes, which contain a porphyrin (MP) unit as a pendant and [60]fullerene (C 60 ) and triphenylamine (TPA) moieties as stopper groups at the axle ends (abbreviated as (MP;C 60 -TPA) rot+ with MP = H 2 P or ZnP. The photophysical properties were investigated by means of time-resolved fluorescence and transient absorption measurements with changing solvent polarity. The charge separation took place mainly via ( 1 MP*;C 60 -TPA) rot+ and (MP; 1 C 60 *-TPA) rot+ in polar solvents. Within the charge-separated states of triads (MP;C 60 -TPA) rot+ , hole-shift and/or back electron transfer took place competitively. The lifetime of the charge separation state of (ZnP;C 60 -TPA) rot+ was similar to that of dyad (C 60 -TPA) rot+ (140 ns in dimethylformamide), whereas that of (H 2 P;C 60 -TPA) rot+ was as long as 230 ns, suggesting two final charge separation states such as (MP;C 60•--TPA •+ ) rot+ and (MP •+ ;C 60•--TPA) rot+ depending on the kind of porphyrin.

Self-assembled tetrapyrrole–fullerene and tetrapyrrole–carbon nanotube donor–acceptor hybrids for light induced electron transfer applications

“…The extension of the above work of developing rotaxanes was successfully achieved by developing a mechanically linked triad rotaxanes, which contain a porphyrin (MP) unit as a pendant and fullerene (C 60 ) and triphenylamine (TPA) moieties as stoppers at the axle ends, 23. 38 The photophysical properties were investigated by means of time-resolved and transient absorption studies in solvents of varying polarity. These experiments results revealed multi-step electron transfer, combination of through-space and through bond, within this donor-acceptor complex.…”

Fullerene-Stoppered Bistable Rotaxanes

“…When 9A was acylated with a ferrocene electron-donating unit a similar behaviour as in 9B was observed [25]. However, when 9A was acylated with a triphenylamine derivative a hole shift from the porphyrin to the triphenylamine unit became apparent [26,27]. This chapter illustrates that the design and the synthesis of fullerene-stoppered bistable rotaxanes are important and relevant topics of research.…”

Carbon Nanostructures in Rotaxane Architectures

“…In a triad rotaxane consisting of one electron‐acceptor (C 60 ) and two electron‐donors (ZnP and TPA moieties), it was demonstrated that the position of the components made possible an efficient CS process . The authors carried out a comparison with previously synthesized triad rotaxanes showing longer axles,, concluding the existence of longer lifetimes in this particular case, where a short axle with C 60 and TPA at both terminals was penetrating through a crown‐ether as an electron acceptor and a hole‐shift. The main advantage of this system was that the ZnP moiety was positioned quite near the C 60 and TPA moieties (Scheme ).…”