NOVELTY - Preparation of ruthenium bis(dicarboxybipyridine) dichloride complex comprises: (i) suspending ruthenium trichloride and dcbH2 in dimethylformamide; (ii) irradiating with microwaves for 8-20 minutes; (iii) evaporating the solvent; (iv) stirring the solid in 2M HCl for 4 hours in the dark; and (v) filtering and vacuum drying the solid to give an 80-85% yield of pure Ru(dcbH2)2Cl2.    USE - The compounds are used for: (1) sensitization of wide band gap n-type semiconductors e.g. TiO2, SnO2 or ZnO, (2) absorbing dyes on the surface of wide band gap semiconductors or of amorphous silica to produce a photosensitive material which undergoes a color change following irradiation in the UV-visible region (200-800 nm), (3) molecular sensitizers in photoelectrochemical regenerating cells based on nanocrystalline electrodes of TiO2. (4) conversion of solar energy into electricity in solar cells based on sensitized nanocrystalline TiO2. (all claimed).    ADVANTAGE - High yields of the complexes can be obtained.    DETAILED DESCRIPTION - Preparation of Ru(dcbH2)2(Cl)2 complex, which is an intermediate for the preparation of carboxylate and phosphonate ruthenium polypyridine dyes of formula (I) or (II):    Ru(dcbH2)2(X)2 (I)    Ru(dcbH2)2(Y) (II)    dcbH2 = 4,4'-dicarboxy-2,2'-bipyridine or 5,5'-dicarboxy-2,2'-bipyridine;    X = a monodentate ligand such as CN-, NCS-, py, NC-(CH2)2-CN, NC-(CH2)3-CN, NC-(CH2)4-CN, halide, CO, NO, pyridine, 4-cyanopyridine, dicyanobenzene, H2O, NH3 or NO2-; and    Y = a bidentate ligand of the type 2,2'-bipyridyl, 1,10-phenanthroline or 2,2'-biquinoline (all optionally substituted by one or two -COOH, -B(OH)2, -PO3H2 or -R-PO3H2 groups, where R is a saturated or aromatic spacer group e.g. methylene or phenylene)    comprises:    (i) suspending 150-500 (250) mg of ruthenium trichloride and 250-800 (420) mg of the dcbH2 ligand in 30-100 (50) ml of dimethylformamide;    (ii) irradiating with microwaves for 8-20 (12) minutes at a power of 250-450 W;    (iii) evaporating the solvent;    (iv) stirring the solid in 30-80 (40) ml of 2M HCl for 4 hours in the dark; and    (v) filtering and vacuum drying the solid at 60-90 (80) deg. C to give a yield of 80-85 (82) % of pure Ru(dcbH2)2Cl2.    INDEPENDENT CLAIMS are also included for the following:    (1) Preparation of Ru(dcbH2)2(NCS)2 from Ru(dcbH2)2(Cl)2.    (2) Preparation of Ru(trpy(COOCH3)3)(Cl)3 which is a reaction intermediate for terpyridine complexes of formula Ru(trpy(COOH)3)(X)3 (III) (trpy(COOH)3 = 4,4',4''-tricarboxy-2,2',6',2''-terpyridine).    (3) Preparation of (TBA)3(Ru(trpy(COOH)(COO-)2)(NCS)3 from (III).    (4) Preparation of carboxylate and phosphonate ruthenium polypyridine dyes of formula Ru((PO3H2)n(CH2)mbpy)2(X)2 (IV) and Ru((PO3H2)n(CH2)mbpy)2(Y) (V) utilizing Ru((PO3R2)n(CH2)mbpy)2(C2O4) as intermediate (R = alkyl).