The star-shaped polymer with trans-tetrapyridyl complex of Ru(II) as a core was pre pared by complexation of ester-linked pyridyl-terminated poly(oxyethylene) (($) over bar(n) = 2000) with a Ru5Cl122-; cluster. The unimodal peak of the star-shaped polymer in the gel-permeation chromatogram was shifted to a higher molecular weight region than that of the starting prepolymer. The electron-withdrawing ester substituent in para position of the pyridine ring shifted the metal-to-ligand charge transfer (MLCT) band into the visible region.