Synthesis, spectral characterisation, and electrochemistry of bis-(2,2′-bipyridine)(1-alkyl-2-(naphthylazo)imidazole)ruthenium(II) complexes: X-ray crystal structure of [bis-(2,2′-bipyridine)-{1-ethyl-2-(naphthyl-α-azo)imidazole}ruthenium(II) perchlorate