Synthesis and photochemical studies of a tris(4-iodophenoxy) subphthalocyaninato boron(III)-fulleropyrrolidine dyad

Abstract

A subphthalocyanine-fullerene dyad, 1 was newly synthesized through axial functionalization via central boron of subphthalocyanine with [Formula: see text]-hydroxybenzaldehyde, and subsequent dipolar cycloaddition reaction of fullerene. The subphthalocyanine entity was peripherally functionalized with moderately electron rich 4-iodophenoxy substituents to probe their effect on photoinduced processes within the SubPc-C[Formula: see text] dyad. Optical absorbance studies revealed presence of both entities of the dyad while steady-state fluorescence studies revealed quenching of subphthalocyanine emission in the dyad in both nonpolar toluene and polar benzonitrile solvents. Further, redox potentials of the donor and acceptor entities were obtained by differential pulse voltammetry, and energy of different photochemical processes was evaluated. Femtosecond transient absorption studies revealed occurrence of charge separation in the SubPc-C[Formula: see text] dyad either from the 1SubPc* or 1C[Formula: see text]* in both nonpolar and polar solvents. That is, transient peaks in the 665 nm range corresponding to SubPc[Formula: see text] and at 1015 nm corresponding to C[Formula: see text] was possible to spectrally identify. The measured rate of charge separation, [Formula: see text] was found to be ∼7.0 × 10[Formula: see text] s[Formula: see text] irrespective of the solvent. The rate of charge recombination, [Formula: see text] from the decay of the C[Formula: see text] peak was found to be 1.1 × 109 s[Formula: see text] in toluene and 1.3 × 109 s[Formula: see text] in benzonitrile, respectively. The SubPc[Formula: see text]-C[Formula: see text] radical ion-pair populated the low-laying 3SubPc* prior returning to the ground state.