A cyclometallated organometallic light emitting complex having a first tridentate ligand portion coordinated with a first metal and a second tridentate ligand portion coordinated with a second metal, the complex having a structure according to Formula or: wherein: A is selected from the group consisting of pyrimidine, pyridazine and pyrazine wherein W 1 and W 2 are nitrogen; A' is selected from the group consisting of pyrimidine, pyridazine and pyrazine wherein W 1 and W 2 are nitrogen; M 1 and M 2 are each independently selected from the group consisting of iridium, palladium, osmium, rhenium, ruthenium, platinum and gold; said first tridentate ligand portion includes atoms X 1, X 2 and W 1 coordinated to metal atom M 1; said second tridentate ligand portion includes atoms Y 1, Y 2 and W 2 coordinated to metal atom M 2; wherein at least one of atoms X 1, X 2 is connected to said metal atom M 1 via an organometallic bond and/or wherein at least one of atoms Y 1, Y 2 is connected to said metal atom M 2 via an organometallic bond; X 1, X 2, Y 1 and Y 2 are independently selected from carbon and nitrogen wherein at least one of X 1 and X 2 is carbon and at least one of Y 1 and Y 2 is carbon; R X represents one or more groups selected from H and a substituent, which substituents may be the same or different, wherein the substituent is selected from the group consisting of a hydroxy, carboxy, carboxamido, imino, alkanoyl, cyano, cyanomethyl, nitro, amino, halogen, C 1-12 haloalkyl, C 1-12 alkoxy, C 1-12 haloalkoxy, hydrocarbyl or hydrocarbyloxy group, which may be each independently unsubstituted or substituted, wherever chemically possible, with from 1 to 11 substituents selected from the group consisting of: hydroxy, carboxy, carboxamido, imino, alkanoyl, cyano, cyanomethyl, nitro, amino, halogen, C 1-12 alkyl, C 1-12 haloalkyl, C 1-12 alkoxy, C 1-12 haloalkoxy, C 3-6 cycloalkyl, aryl, aryl-C 1-12 alkyl or C 1-12 alkyl aryl; R 1 to R 14 are each independently selected from the group consisting of H and a substituent; Z 1 and Z 2 are single bonds; T 1 and T 2 are auxiliary ligands in which m and n are 0 or an integer sufficient to satisfy the respective coordination requirements of M 1 and M 2, and where m and n are 2 or more, each respective auxiliary ligand may be the same or different. A is selected from the group consisting of pyrimidine, pyridazine and pyrazine wherein W 1 and W 2 are nitrogen; A' is selected from the group consisting of pyrimidine, pyridazine and pyrazine wherein W 1 and W 2 are nitrogen; M 1 and M 2 are each independently selected from the group consisting of iridium, palladium, osmium, rhenium, ruthenium, platinum and gold; said first tridentate ligand portion includes atoms X 1, X 2 and W 1 coordinated to metal atom M 1; said second tridentate ligand portion includes atoms Y 1, Y 2 and W 2 coordinated to metal atom M 2; wherein at least one of atoms X 1, X 2 is connected to said metal atom M 1 via an organometallic bond and/or wherein at least one of atoms Y 1, Y 2 is connected to said metal atom M 2 via an organometallic bond; X 1, X 2, Y 1 and Y 2 are independently selected from carbon and nitrogen wherein at least one of X 1 and X 2 is carbon and at least one of Y 1 and Y 2 is carbon; R X represents one or more groups selected from H and a substituent, which substituents may be the same or different, wherein the substituent is selected from the group consisting of a hydroxy, carboxy, carboxamido, imino, alkanoyl, cyano, cyanomethyl, nitro, amino, halogen, C 1-12 haloalkyl, C 1-12 alkoxy, C 1-12 haloalkoxy, hydrocarbyl or hydrocarbyloxy group, which may be each independently unsubstituted or substituted, wherever chemically possible, with from 1 to 11 substituents selected from the group consisting of: hydroxy, carboxy, carboxamido, imino, alkanoyl, cyano, cyanomethyl, nitro, amino, halogen, C 1-12 alkyl, C 1-12 haloalkyl, C 1-12 alkoxy, C 1-12 haloalkoxy, C 3-6 cycloalkyl, aryl, aryl-C 1-12 alkyl or C 1-12 alkyl aryl; R 1 to R 14 are each independently selected from the group consisting of H and a substituent; Z 1 and Z 2 are single bonds; T 1 and T 2 are auxiliary ligands in which m and n are 0 or an integer sufficient to satisfy the respective coordination requirements of M 1 and M 2, and where m and n are 2 or more, each respective auxiliary ligand may be the same or different.