Electrochemical Screening of Nickel, Copper, and Manganese meso-Aryl Dipyrrinato Complexes Probing Electrocatalytic...

A series of homoleptic meso-aryl dipyrrinato 1(a-c) and 2(a-c) complexes namely, [(p-R-C₆H₄)C(C₄H₃N)₂]_nM [where, R = OMe, n = 2, M = Ni (1a), Cu (1b) and n = 3, Mn (1c); and R = t-Bu, n = 2, M = Ni (2a), Cu (2b) and n = 3, Mn (2c)] have been synthesized in moderate (ca. 21%-31%) yields. The spectral and structural studies revealed that nickel(II) (1-2)a and copper(II) (1-2)b complexes adopted distorted square planar geometry, whereas Mn(III) (1-2)c exhibited octahedral geometry metal centre. Electrochemical studies highlighted a reversible Cu(II/I) redox couple in the representative copper(II) (1b) complex, accompanied by a modest hydrogen evolution reaction (HER) activity, which is triggered following the formation of the Cu(I) state. On the other hand, the nickel(II) (1a) and the Mn(III) (1c) complexes remained inactive for electrochemical HER, primarily due to the low basicity of the reduced metal sites. The controlled potential electrolysis and spectroelectrochemical studies further demonstrated the stability of the copper(II) (1b) complex under electrolytic conditions. These findings underscore the potential of meso-aryl dipyrrinato complexes as versatile platforms for future electrocatalytic applications.