Absorption spectrophotometric, fluorescence, transient absorption and quantum chemical investigations on fullerene/phthalocyanine supramolecular complexes

The present paper reports the photophysical investigations on supramolecular interaction of a phthalocyanine derivative, namely, 2,9,16,23-tetra-tert-butyl-29H,31H-Pc (1) with C60 and C70 in toluene. The binding constants of the C60 and C70 complexes of 1 are estimated to be 27,360 and 25,205 dm3, respectively. Transient absorption measurements in the visible region establishes that energy transfer from C60*T (and C70*T) to 1 occurs predominantly in toluene which is subsequently confirmed by the consecutive appearance of the triplet states of 1. Quantum chemical calculations at DFT level of theory explore the geometry and electronic structure of the supramolecules and testify the significant redistribution of charge between fullerenes and 1.

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► The present article introduces a newly designed Pc-derivative, namely, 2,9,16,23-tetra-tert-butyl-29H,31H-Pc (1), which is a very unique molecule in terms of its important photophysical features.
► The monophthalocyanine, 1, is unable to serve as an effective and selective molecular tweezers for C70.
► Binding of C60 and C70 in the cleft of 1 is clearly demonstrated by the stereoscopic structures generated by DFT calculations.
► The mechanism of energy transfer phenomenon from 1 to C60 and C70 is nicely demonstrated by the transient absorption study in our present investigations.
► The results reported in the present investigations would provide a viable environment to see the various interactive processes involved in fullerene/phthalocyanine systems at ground and excited states.