Photophysical Properties of C₆₀(C₆H₅)₅Cl:  A Laser Flash Photolysis and Pulse Radiolysis Study

Abstract

Photophysical and photochemical properties of the singlet and triplet excited states of monochloropentaphenylfullerene [C60(C6H5)5Cl, MCPPF] have been characterized in two different solvents, benzene and benzonitrile, using two complementary transient absorption techniques, namely picosecond laser flash photolysis and nanosecond electron pulse radiolysis. Singlet−singlet and triplet−triplet absorption spectra have been recorded. The quantum yield of triplet formation (φT = 0.45 ± 0.05) and the intrinsic lifetime of the triplet (τ = 100 ± 10 μs) have been determined. Apart from the intrinsic decay of the triplet to the singlet ground state, another two processes, namely T−T annihilation and quenching by the ground state, make important contribution towards the overal triplet decay rate. Weak charge transfer (CT) complexes are formed between MCPPF and the electron-rich amines diphenylamine (DPA) and triphenylamine (TPA) in benzonitrile solution. On laser excitation, the CT complex undergoes charge separation, but the radical ions undergo very fast geminate recombination to form the triplet state of MCPPF.

Photophysical and Electron Transfer Properties of C60(C6H5)5OH and C60(C6H4F)5OH: A Laser Flash Photolysis and Pulse Radiolysis Study

“…The absorption spectra of both of the molecules have similar features with the absorption peaks at 215, 231, and 255 nm and weak shoulders in the 330−370, 380−430, and 450−550 nm regions. These features are very similiar to those of C 60 (C 6 H 5 ) 5 Cl as reported earlier . The absorption peaks of C 60 in cyclohexane at 231, 257, and 329 nm are very sharp as compared to the absorption peaks of these three fullerene derivatives.…”

“…The Fullerene Science Centre at the University of Sussex, U.K. has synthesized a series of pentaaryl derivatives of fullerene[60] in which the nonlinear and electron transfer properties are expected to be significantly modified. Recently we have reported the results of our investigations of the photophysical and photochemical properties of one of these derivatives, namely monochloropentaphenylfullerene, C 60 (C 6 H 5 ) 5 Cl (MCPPF) . In this present paper the photophysical and photochemical properties of the other two derivatives of the same series, namely, pentaphenylfulleren-2-ol (C 60 (C 6 H 5 ) 5 OH, PPF) and penta-4-fluorophenylfulleren-2-ol [C 60 (C 6 H 4 F) 5 OH, PFPF], are being reported.…”

“…The physicochemical properties of these fullerene derivatives have been shown to be very different from pristine fullerene[60] and this effect has been rationalized in terms of the perturbation of the electron distribution on the surface of the spherical molecule due to the presence of the functional groups . The functionalization of the fullerenes has led to derivatives with increased solubility in water, − modified electron transfer, , and better nonlinear optical properties. − The increased solubility of the fullerenes in water provides the flexibility for their use in photodynamic therapy. However, due to the introduction of the functional groups onto the fullerene[60], two important properties, namely the quantum yield and the lifetime of the triplet state, which are responsible for high quantum yield of singlet oxygen in the photochemical reactions involving the fullerene[60], are reduced considerably. − Water-soluble fullerenes also show strong aggregation properties in aqueous solutions .…”

“…The functionalization of the fullerenes has led to derivatives with increased solubility in water, − modified electron transfer, , and better nonlinear optical properties. − The increased solubility of the fullerenes in water provides the flexibility for their use in photodynamic therapy. However, due to the introduction of the functional groups onto the fullerene[60], two important properties, namely the quantum yield and the lifetime of the triplet state, which are responsible for high quantum yield of singlet oxygen in the photochemical reactions involving the fullerene[60], are reduced considerably. − Water-soluble fullerenes also show strong aggregation properties in aqueous solutions . Pyrrolidino fullerenes have recently been shown to have excellent nonlinear properties and efficient photocurrent response .…”

Photophysical Properties of a 1,2,3,4,5,6-Hexasubstituted Fullerene Derivative

“…Previous reports have shown that small perturbations in the π system give similar photophysical properties as those of pristine fullerene, but a larger number of substitutions result in more significant changes. [18][19][20][21][22][23][24][25][26][27][28][29] In light of the large number of applications for these novel compounds, there has been widespread effort to elucidate the relationship between the structure of these derivatives and their photophysical properties. [30][31][32][33][34] Pratt et al have reported a homologous series of methanofullerenes showing that the number of perturbations of the π system at different sites within the fullerene framework cause systematic changes in the triplet state properties.…”