Exploring electrochemiluminescence behaviours and absolute quantum efficiencies of substituted metal-free phthalocyanine and unsubstituted zinc phthalocyanine

The electrochemiluminescence (ECL) properties and absolute quantum efficiencies (Φ ECL ) of octabutoxy-substituted metal-free phthalocyanine (H 2 Pc(α-OC 4 H 9 ) 8 ) and unsubstituted zinc phthalocyanine (ZnPc) were systematically investigated using spectroelectrochemical and photoelectrochemical techniques. H 2 Pc(α-OC 4 H 9 ) 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 Φ ECL 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 an excimer emission at 900 nm were observed via PL. ZnPc demonstrated enhanced ECL with BPO, producing an exciplex emission at 775 nm and an Φ ECL of 0.0099 ± 0.0001%, which is lower than that of Ru(bpy) 3 2+ but exceeds that of related porphyrin derivatives. These results highlight the ECL behaviours of phthalocyanines and provide insight into their use as ECL luminophores.