TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Ligand: The organic ligand is a heterocyclic aromatic ring system with carboxylic acid functional group(s). The dye material comprises an organometallic compound incorporating the ligand and metal ion.Preferred Dye: The dye material is a ruthenium complex of formula: RuL2(SCN)2, where L is 2,2'-bipyridine-4,4'-dicarboxylic acid.Preferred Process: The organic ligand is absorbed on the inorganic oxide in an aqueous solution of dilute chromic acid and the oxide with the absorbed ligand is isolated by filtration. The filtered material is then dispersed in concentrated nitric acid allowing the ligand to dissolve. The dissolved ligand is removed by filtration and thus the organic ligand is purified. The dye material is absorbed on the inorganic oxide in an alkaline medium in which trifluoroacetic acid is added to convert the alkali salt of the ligands to reactive carboxylic acid functional groups and the oxide with the absorbed ligand is filtered. The filtered material is then dispersed in an alkaline aqueous medium and the dye material is dissolved. The dissolved dye material is precipitated with trifluoroacetic acid and isolated by filtration.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Materials: The alkaline medium is an aqueous solution of sodium hydroxide. The inorganic oxide comprises silica, alumina and/or titania. The inorganic oxide is in a form providing a high surface area achieved by using porous particles of the inorganic oxide. The inorganic oxide is provided in the form of a porous film on a substrate. The substrate has an internal surface of long tubes or capillaries. The metallic oxide film is preferably a nanoporous titanium oxide layer deposited on transparent conductive layer on a substrate. SPECIFIC COMPOUNDS - The ligand is 2,2'-bipyridine-4,4'-dicarboxylic acid (L).    EXAMPLE - 4,4'-Dimethyl-2,2'-bipyridine was oxidized with chromic acid to produce an incompletely oxidized ligand. The obtained product was interacted with titania having particle size of 50-100 microns in a diluted solution of the oxidizing chromic acid medium. Titania was taken in the weight ratio of 4:1 with respect to ligand in order to ensure that the surface area of the metallic oxide was sufficient to absorb all the ligand. The chromium ions and other by-products were removed with water by filtration. The precursor ligand was completely oxidized, dissolved in concentrated nitric acid and separated from the metallic oxide by filtration. The dissolved ligand was diluted with cold water and pure oxidized 2,2'-bipyridine-4,4'-dicarboxylic acid (L) ligand was obtained. The obtained insoluble pure ligand was filtered and dried under vacuum.