Luminescent compounds

A luminescent compound represented by the general formula: wherein X represents one of a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom or a selenium atom; r represents an aromatic group and/or an aliphatic group; p is an integer of 1 or 2; q and s are independently integers of 1, 2, 3 or 4; y1, Y2 and Y3 independently comprise, consist of or represent a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a bromine atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a polyether chain, a polyglycol group, an oxygen atom, a nitrogen atom, a cyano group or a nitro group; two or more of Y1, Y2, and/or Y3 may be combined together to form a fused ring; wherein one or more of Y1, Y2 and/or Y3 comprises a spacer comprising a continuous chain of 3 to 20 atoms and further comprising a functional group capable of forming a covalent bond with the second substance, said functional group being selected from one or more of a carboxylic acid, an ester,