Patent ID: 8106198

Claim:
A bivalent transition metal complex expressed by the formula (I): ML 1 L 2 A 2 (I) where, in the formula (I), M is a bivalent iron ion, ruthenium ion, or osmium ion, each A is independently an isothiocyanato group (—NCS), an isocyanato group (—NCO), or an isoselenocyanato group (—NCSe), L 1 in the formula (I) is expressed by the formula (a1): where, in the formula (a1), each R 1 is independent with at least one being a carboxyl group, a phosphate group, a sulfonate group, or a salt of any of the above, and each remaining R 1 , if any, being a hydrogen atom, and each R 2 is independent with at least one being a carboxyl group, a phosphate group, a sulfonate group, or a salt of any of the above, and each remaining R 2 , if any, being a hydrogen atom, and L 2 in the formula (I) is expressed by the formula (b1): where, in the formula (b1), each n independently denotes an integer of no less than 0 and no more than 3, each Y independently denotes a hydrogen atom or Ar, with each Ar independently being expressed as structural formulae (c1): where, in the formula (c1), X denotes a sulfur atom, oxygen atom, or nitrogen atom, each Z independently denotes a hydrogen atom or an alkyl group or alkoxy group having 1 to 16 carbons that may be substituted with a fluoro group, with at least one Z being an alkyl group or alkoxy group.