Bipyridine-based metal complex and ink composition comprising the same

An ink composition comprising an aqueous medium and a bipyridine-based metal complex represented by formula (I):

• R1, R2, and R3 are respectively mono-substituents, or the same or different multi-substituents, and are selected from the group consisting of a hydrogen atom, a halogen atom, a nitro group, —SO3H, —COOH, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C1-C20 heteroalkyl group, a hydroxy group, an amino group, a cyano group, a substituted or unsubstituted C2-C20 alkenyl group, a substituted or unsubstituted C1-C20 alkoxy group, a substituted or unsubstituted C1-C20 alkylsulfonamide group, a substituted or unsubstituted C6-C20 arylsulfonamide group, a substituted or unsubstituted C1-C20 acylamino group, a C1-C20 alkylureido group, a C6-C20 arylureido group, a C2-C20 alkoxycarbonyl group, a C2-C20 alkoxycarbonylamino group, a carbamoyl group, a sulfamoyl group, a sulfo group or its salt, a carboxy group or its salt, a substituted or unsubstituted C1-C20 hydroxyalkyloxyalkyl group, a substituted or unsubstituted C1-C20 dialkylaminoalkyl group, a substituted or unsubstituted C6-C20 pyridylalkyl group, a substituted or unsubstituted C5-C20 pyridyl group, a substituted or unsubstituted C6-C20 imidazolyl group, a hydrazine group, a hydrozone group, a substituted or unsubstituted C1-C20 pyridylalkyl group, a substituted or unsubstituted C6-C20 aryl group, a substituted or unsubstituted C6-C20 arylalkyl group, a substituted or unsubstituted C6-C20 heteroaryl group, or C6-C20 heteroarylalkyl group, a substituted or unsubstituted C6-C20 heteroarylalkenyl group, and a substituted or unsubstituted C3-C20 heterocycloalkyl group, wherein not all of R1, R2 and R3 are a hydrogen atom;
• M is a metal atom of one of groups III to XIV;
• and
• Z is a counter ion.