Substituted [Cu(I)(POP)(bipyridyl)] and related complexes: synthesis, structure, properties and applications to dye-sensitised solar cells. 
The synthesis and subsequent spectroscopic, electrochemical, photophysical and computational characterisation of a series of heteroleptic Cu(I) complexes of general formula: [CuPOP{4,4'(R)-bipyridyl}][BF(4)] and [CuPOP{4,4',6,6'(R)-bipyridyl}][BF(4)] is described (POP = bis{2-(diphenylphosphanyl)phenyl} ether; R = Me, CO(2)H, CO(2)Et.  The steric constraint imposed by the POP ligand can impede distortion towards square planar geometry upon MLCT excitation or oxidation and this is explored in the context of varying substituents on the bipyridyl ligand.  The insight gained opens new avenues for design of functional Cu(I) systems suitable for photophysical and photoelectrochemical applications such as sensitisers for dye-sensitised solar cells (DSSCs).