TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preparation (disclosed): The new dye is obtained by reacting a bipyridine derivative with dichloride (p-cymene) ruthenium dimer in the presence of a solvent. Preferred Definitions:    M=ruthenium;and    R4 and/or R5=aryl or complex aromatic group substituted by optionally substituted alkyl, optionally substituted alkoxy, optionally substituted aryloxy, optionally substituted alkylthio, optionally substituted alkylamino, or optionally substituted arylamino.    SPECIFIC COMPOUNDS - 3 specific ruthenium metal complexes of formulae (A-C) are disclosed as the dye.    EXAMPLE - 4,4'-dimethyl-2,2'-bipyridine (in g) (11) was dissolved in tetrahydrofuran (300 ml), mixed with lithium diisopropyl amide solution (35 ml) and tetrahydrofuran (31 ml), and maintained at -70degreesC. The mixture was stirred and heated to 0degreesC. The temperature was maintained for 60 minutes. Tetrahydrofuran solution (88 ml) of p-methoxy benzaldehyde (7.5 ml) was dripped over 60 minutes and stirred for 120 minutes. The mixture was heated to room temperature and stirred for 12 hours. After distillation, dichloromethane (300 ml) and ion-exchange water (500 ml) were added, and water and organic layers were separated. The water layer was extracted twice by dichloromethane (300 ml). The extract was mixed with organic layer, washed with ion-exchange water (300 ml) twice, and dried. The solvent was distilled, to obtain a yellow solid (21). The yellow solid was purified to obtain 4-(2-(4-methoxy phenyl)-2-hydroxy ethyl)-4'-methyl-2,2'- bipyridine (9.8). The product (7.2) and ammonium p-toluene sulfonate (11) were dissolved in toluene (2000 ml) and heat-refluxed at 90degreesC. The reaction mixture was washed with ion-exchange water (600 ml) and dried. The solvent was distilled, and the mixture was dried to obtain 4-methyl-4'-(4-methoxy styryl)-2,2'-bipyridine (4.5) as yellow powder. 4-methyl-4'-(4-methoxy styryl)-2,2'-bipyridine (149 mg) was added to a solution obtained by adding N,N-dimethyl formamide (75 mL) to dichloride (p-cymene) ruthenium (II) dimer (150 mg) and stirred at 60degreesC for 4 hours. 2,2'-bipyridine-4,4'-dicarboxylic acid (121 mg) was added and refluxed at 150degreesC for 4 hours. Potassium thiocyanate (483 mg) was added and refluxed at 150degreesC more for 4 hours. The mixture was concentrated, water (45 mL) and nitric acid were added, and stirred at room temperature. The pH was adjusted to 2.5, and the product was filtered to obtain a dye (121 mg) of formula (A) with a yield of 32%.