Dimerization of C70 under high pressure : thermal dissociation and photophysical properties of the dimer C140

• We have recently shown that solid C70 efficiently converts into a cap-to-cap dimer C2hC140 at pressure of ~1 GPa and temperature of ~200 °C [1]. Here we report on measurements of the thermal dissociation of C140 (purified by chromatography) at ambient pressure and its photophysical properties, in particular photogeneration of singlet oxygen (1O2). The kinetics of dissociation of C140 in the solid state between 130 and 200 °C is well described by a simple first-order process, with an activation energy of 1.6±0.03 eV (compare to 1.75±0.05 eV for the C60 dimer C120 [2]). In contrast, the thermal dissociation of C140 dissolved in o-dichlorobenzene shows different, non-Arrhenius behavior, suggesting a strong influence of the molecular surroundings. The quantum efficiency of 1O2 generation in solutions of C140 and C120 is close to unity, i.e. similar to that of C70 and C60.

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NATURVETENSKAP  -- Fysik -- Annan fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Other Physics Topics (hsv//eng)

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