Synthesis, physicochemical properties and theoretical calculations of a subphthalocyanine peripherally substituted by multiple anthryl-ethynyl-aniline moieties

Abstract

We report here the synthesis of a novel [Formula: see text]-subphthalocyanine (SubPc)-based electron donor-acceptor conjugate (1) in which the macrocycle has been functionalized at its peripheral positions with three anthryl-ethynyl-[Formula: see text],[Formula: see text]-dimethylaniline groups. The latter moiety, besides conferring increased stability and solubility to the resulting system, substantially broadens its absorption capability. In-depth spectroscopic, spectrometric, and electrochemical analyses as well as theoretical calculations carried out on 1 suggest a moderate ground state intramolecular interaction between the macrocycle and the orthogonally-arranged anthryl-ethynyl-[Formula: see text],[Formula: see text]-dimethylaniline moieties. Interestingly, such electronic communication significantly increases in the excited state in a process strongly depending on the polarity of the solvent. On the one hand, in toluene, upon photoexcitation of the anthryl-ethynyl-aniline, the formation of a [Formula: see text](SubPc) state is observed which decays into a [Formula: see text](SubPc) manifold before deactivating to the ground state. On the other hand, increasing the polarity of the solvent to tetrahydrofuran and benzonitrile, significantly modifies the fate of the photoexcited state. In this new scenario, the [Formula: see text](SubPc) state, formed directly upon 550 nm light stimulation or by [Formula: see text](anthryl-ethynyl-aniline) sensitization upon 405 nm excitation, transforms into a charge transfer (SubPc)[Formula: see text]-anthryl-ethynyl-aniline[Formula: see text] state which further evolves into a fully charge-separated (SubPc)[Formula: see text]-anthryl-ethynyl-aniline[Formula: see text] species before deactivating to the ground state.