An efficient oxygen evolution reaction by Ru(ii) polypyridyl complex-based AIEgen

Abstract

Ruthenium polypyridyl complexes are known for their excellent photophysical properties and rich electrochemical behavior. Thus, developing complexes with multifunctional behavior showing potential applications in multiple fields is of great importance. Herein, we report a new aggregation-induced emission (AIE) active bis-heteroleptic ruthenium(II) complex (Ru-4) of 4,7-diamino 1,10-phenanthroline along with a series of other bis-heteroleptic Ru(II) polypyridyl complexes (Ru-1, Ru-2 and Ru-3) containing 4,7-disubstituted 1,10-phenanthroline and two homoleptic complexes (Ru-5 and Ru-6) of 2,2′-bipyridine and 1,10-phenanthroline. Complex Ru-4 shows aggregation-induced emission and 2.7-fold and 5-fold increments in the luminescence intensity were observed in the presence of H₂O and PEG, respectively. The AIE of complex Ru-4 is due to nanoaggregate formation and radiative decay from the ³MLCT excited state, which is supported by dynamic light scattering (DLS) and scanning electron microscopy (SEM). The electronic transitions responsible for absorption and emission are assigned with the help of ground and excited state time-dependent density functional theory (TD-DFT) calculations. The complexes were effectively utilized for studying the electrocatalytic oxygen evolution reaction (OER), which revealed that among all the catalysts, Ru-4 is highly feasible for the OER due to its large, exposed surface sites (j_ESCA = 18.76 mA cm⁻²) and low charge transfer resistance (R_ct = 8.15 Ohm). The turnover frequency (TOF) and Tafel slope values were found to be 4.16 × 10⁻⁵ and 157 mV dec⁻¹, respectively, for Ru-4, suggesting its excellent electrocatalytic water oxidation properties.