Muhammad Usman Khan, Shabbir Hussain, Muhammad Adnan Asghar, Khurram Shahzad Munawar, Rasheed Ahmad Khera, Muhammad Imran, Mohamed M.
This article is cited by 276 publications. The nature of the spacer between C 60 and ferrocene, weak electronic ground-state interactions, steady-state fluorescence, and picosecond-resolved photolysis suggest two different quenching mechanism: through-bond electron transfer for dyads 2, 5, and 6 and formation of a transient intramolecular exciplex for dyads 3 and 4. Nanosecond-resolved photolysis of dyads 3 and 4 in degassed benzonitrile revealed long-lived charge separated states (τ 1/2 = 1.8 μs ( 3) and τ 1/2 = 2.5 μs ( 4)) with characteristic fullerene radical-anion bands at λ max = 1055 nm. Picosecond resolved photolysis of dyads 2− 6 in toluene showed light-induced formation of the excited singlet state which undergoes rapid intramolecular quenching, with rate constants of 28 × 10 9 s -1, 6.9 × 10 9 s -1, 3.4 × 10 9 s -1, 14 × 10 9 s -1, and 2.3 × 10 9 s -1, respectively.
A rapid intersystem crossing (τ 1/2 = 1.2 ps) to the excited triplet state was observed with characteristic absorption around 705 nm. Excitation of N-methylfulleropyrrolidine revealed the immediate formation of the excited singlet state, with λ max around 886 nm. The fluorescence of the investigated dyads 2 (Φ rel = 0.17 × 10 -4), 3 (Φ rel = 0.78 × 10 -4), 4 (Φ rel = 1.5 × 10 -4), 5 (Φ rel = 0.7 × 10 -4), and 6 (Φ rel = 2.9 × 10 -4) in methylcyclohexane at 77 K were substantially quenched, relative to N-methylfulleropyrrolidine 1 (Φ rel = 6.0 × 10 -4), indicating intramolecular quenching of the fullerene excited singlet state. A systematic steady-state fluorescence and time-resolved flash photolytic investigation of a series of covalently linked fullerene/ferrocene based donor−bridge−acceptor dyads is reported as a function of the nature of the spacer between the donor site (ferrocene) and acceptor site (fullerene) and the dielectric constant of the medium.
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