Copper(II) mixed-valence complex, [Cu(II)Cu(I)(R)3(RH)2L4].CH3COCH3 (R = C6H5COO; L = CH3COCH2C(OH)(CH3)2) (1), is a potential photovoltaic material with low bandgap It is formed as a black solid from a facile carbon-carbon bond-forming reaction involving [Cu2(C6H4COO)4(C2H5OH)2] (2) and CH3COCH3 under acidic condition. The complex was soluble in most common organic solvents, but insoluble in water. Its formula was deduced from FTIR, UV-vis, and 1H-NMR spectroscopies, TGA and GCMS. Its effective magnetic moment was 1.33 B.M. at 298 K, suggesting strong antiferromagnetic coupling between the two Cu centres. Cyclic voltammetry shows an anodic peak at +0.70 V and two cathodic peaks at +0.53 V and -1.0 V. The HOMO and LUMO energy levels are 4.9 eV and 3.7 eV respectively, and hence the bandgap energy is 1.2 eV.