Exploring Electrochemiluminescence Behaviours and Absolute Quantum Efficiencies of Substituted Metal-Free Phthalocyanine and Unsubstituted Zinc Phthalocyanine

Abstract

The electrochemiluminescence (ECL) properties and absolute quantum efficiencies (ΦECL) of octabutoxy-substituted metal-free phthalocyanine (H2Pc(α-OC4H9)8) and unsubstituted zinc phthalocyanine (ZnPc) were systematically investigated using spectroelectrochemical and photoelectrochemical techniques. H2Pc(α-OC4H9)8 exhibited negligible ECL in the annihilation pathway but showed a substantial increase in emission with the addition of benzoyl peroxide (BPO), resulting in an ΦECL of 0.00075 ± 0.00003%. Spectroscopy revealed Q-band transitions at 635 and 780 nm along with the formation of an exciplex at 880 nm in the coreactant ECL system, and a excimer emission at 900 nm were observed via PL. ZnPc demonstrated enhanced ECL with BPO, producing an exciplex emission at 775 nm and an ΦECL of 0.0099 ± 0.0001%, which is lower than that of Ru(bpy)32+ but exceeds that of related porphyrin derivatives. These results highlight the ECL behaviours of phthalocyanines and provide insight into their use as ECL luminophores.