Polypyridine heteroleptic Cu(I) complex with 4-methyl-2,2´-bipyridine-4´-carbonitrile: synthesis and characterization

TOMAS, FEDERICO M.L A.; SALOMÓN, FERNANDO F; FAGALDE, FLORENCIA

Virtual

Simposio; 8th Latin American Symposium on Coordination and Organometallic Chemistry; 2022

Institute of Advanced Materials, INAM

In this work, we focus on the synthesis and physicochemical characterization of a heteroleptic complex of Cu(I), containing 6,6´-dimethyl-2,2´-bipyridine (dmb) and 4-methyl-2,2´-bipyridine-4´-carbonitrile (MebpyCN). The CN stretching frequency was founded at 2170 cm-1 by solid FTIR, showing a shift with respect to that of the free ligand. This phenomenon was assigned to solid-state effects by comparison with the compound’s FTIR spectrum measured in CH¬2Cl2. The electronic transitions were studied by UV-Vis spectroscopy in CH2Cl¬¬2 solution. The structure of the complex was rationalized by analyzing the decrease in the band I, typical of diiminic Cu(I) complexes, contrasted to those containing sterically unhindered ligands at key positions [1]. This result allows us to propose an almost tetrahedral (quasi D2d) structure for the complex. In turn, a bathochromic shift of the MLCT transition band (band II, λmax= 460 nm) was observed with respect to the homoleptic complex with dmb, indicative of the stabilization of the LUMO by the presence of the nitrile group. Electrochemical measurements were carried out in CH2Cl2, with NBu4PF6 as supporting electrolyte, Pt as working electrode, a Pt wire as counter electrode and ferrocene as internal reference, from which a single, totally irreversible process was found and assigned to the Cu(II)/Cu(I) couple. The Cu(II)/Cu(I) potential founded and the UV-Vis spectroscopy measured over time, justify the stability of the complex in, as opposed to unhindered homoleptic complexes. DFT calculations support the experimental results, and helped to raise a perspective on the application of the complex as dye in dye-sensitized solar cell (DSSC) devices.