A 1, 4 bidentate ligand comprising first and second ligand centres, wherein the first ligand centre is an sp2-hybridised carbon or a nitrogen atom; wherein the second ligand centre is a nitrogen atom in a five- or six-membered aromatic or hetero-aromatic ring, said ring having a substantially linear substituent T1 meta or para to the nitrogen atom; wherein T1 has the formula 1: —Ar1a—Y1b—Ar2—[Y2c—Ar2]d—S—B  (1) and wherein T1 is attached to the ring by X1, wherein X1 is a bond, a methylene group, a substituted methylene group, an oxygen atom or a sulphur atom, wherein each Ar1 and Ar2 are independently selected from the group of C6 to C20 aromatic and C4 to C20 heteroaromatic groups, wherein Y1 and each Y2 is independently an optionally substituted C2 or acetonitrile trans double-bond linking moiety, wherein a is 0, 1, 2 or 3, wherein b is 0, 1 or 2, wherein each c is independently 0, 1 or 2, wherein d is 0, 1, 2, 3 or 4, S is a flexible spacer, and B represents a moiety having one or more cross-linkable functionalities. Network polymers, complexes, compositions, and devices based on this ligand. Method for forming devices based on this ligand.