Synthesis and optical properties of 3,5-bis(10-phenylanthracen-9-yl)benzene-appended porphyrins

Abstract

Singlet–singlet and triplet-triplet energy-transfer processes between anthracenes and porphyrins have received considerable attention in materials chemistry. Herein, we report the first examples of 3,5-bis(10-phenylanthracen-9-yl)benzene-appended porphyrins (BPABPs) designed to study intramolecular energy transfer between two chromophores. The Curtius rearrangement of 3,5-bis(10-phenylanthracen-9-yl)benzoyl azide in the presence of the platinum(II) complex of 5,10,15-tris(3,5-di-tert-butylphenyl)-20-(3-hydroxyphenyl)porphyrin or its free base in toluene afforded the corresponding BPABP. Spectroscopy, cyclic voltammetry, and density functional theory calculations revealed that the anthracene and porphyrin [Formula: see text]-electron systems of the BPABPs are not conjugated and consequently do not affect each other’s absorption properties. In contrast, the BPABPs exhibited considerably different luminescence properties to those of phenyl 3,5-bis(10-phenylanthracen-9-yl)carbamate and 5,10,15-tris(3,5-di-tert-butylphenyl)-20-(3-methoxyphenyl)porphyrins; the anthracene units of the BPABPs show considerably quenched fluorescence compared to that of the reference anthracene, indicative of efficient intramolecular singlet–singlet energy transfer from the anthracene to the porphyrin unit. The phosphorescence quantum yield of the Pt complex of BPABP is comparable to that of the reference Pt-porphyrin, which suggests that intramolecular triplet-triplet energy transfer from the Pt-porphyrin to the anthracene unit is inefficient. The present findings improve our understanding of how structural factors and excited-state energy levels affect energy transfer and triplet-triplet annihilation upconversion processes of covalently linked bisanthracene-appended porphyrins.