Electrocatalytic water oxidation studies of a tetranuclear Cu(ii) complex with cubane-like core Cu4(μ3-O)4

• Published in: New journal of chemistry 2019-01, Vol.43 (11), p.4640-4647
• Main Authors: Wei-Song, Gao, Jin-Miao, Wang, Ning-Ning, Shi, Chang-Neng, Chen, Yu-Hua, Fan, Wang, Mei
• Format: Article
• Language: English
• Subjects: Antiferromagnetism; Apexes; Biomimetics; Clusters; Crystallography; Cubane; Electrochemistry; Magnetic permeability; Oxidation; Photosynthesis; Temperature dependence; X ray analysis
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c8nj06263c

To mimic the strategy used by natural photosynthesis in Photosystem II, which adopts the cubic Mn4CaO5 cluster as a natural oxygen-evolving complex, a bio-inspired cubane-like tetranuclear cluster [Cu4(pdmH)4(OAc)2](NO3)2·3H2O (1) has been synthesized successfully with pyridine-2, 6-dimethanol as the ideal ligand, and investigated by X-ray crystallography, PXRD, in situ UV-vis-NIR spectroelectrochemical analysis, and magneto- and electrochemistry. By X-ray analysis, it is shown that the distorted cubane-like core Cu4(μ3-O)4 is composed of four CuII and four μ3-O which arrange at the vertices of a slightly distorted cube. Electrochemical studies indicate that complex 1 presents potential properties as an effective molecular catalyst for electrocatalytic water oxidation under aqueous alkaline conditions at a potential of ∼1.20 V vs. NHE with a relatively low overpotential of ∼400–665 mV vs. NHE, which may result from the unique covalent metal–oxo bonding. Magnetic susceptibility measurements reveal that complex 1 displays overall antiferromagnetic exchanges between the Cu(ii) ions within the clusters. Temperature dependence of in-phase (χM′) ac susceptibility signals display frequency-dependence, whereas the out-of-phase (χM′′) signals show no significant frequency-dependence for complex 1, which indicates that the complex may not be a SMM.