Patent ID: 7923442

Claim:
A compound of formula 1: wherein, the compound of formula 1 is a ring; and X is O or NH M is Se or Te n is 0 or 1 R 1 is: oxygen and forms an oxo complex with M; oxygen and forms together with the metal, a 4-7 membered ring, which optionally is substituted by an oxo or amino group; or oxygen and forms together with the metal, a first 4-7 membered ring, which is optionally substituted by an oxo or amino group, wherein said first ring is fused with a second 4-7 membered ring, wherein said second 4-7 membered ring is optionally substituted by alkyl, alkoxy, nitro, aryl, cyano, hydroxy, amino, halogen, oxo, carboxy, thio, thioallcyl, or —NH(C═O)R A , —C(═O)NR A R B , —NR A R B or —SO 2 R where R A and R B are independently H, alkyl or aryl; R 2 , R 3 and R 4 are independently hydrogen, alkyl, alkoxy, nitro, aryl, cyano, hydroxy, amino, halogen, carboxy, thio, thioalkyl, or —NH(C═O)R A , —C(═O)NR A R B , —NR A R B or —SO 2 R where R A and R B are independently H, alkyl or aryl; or R 2 , R 3 or R 4 together, with the organometallic ring to which two of the substituents are attached, form a fused 4-7 membered ring system wherein said 4-7 membered ring is optionally substituted by alkyl, alkoxy, nitro, aryl, cyano, hydroxy, amino, halogen, oxo, carboxy, thio, thioallcyl, or —NH(C═O)R A , —C(═O)NR A R B , —NR A R B or —SO 2 R where R A and R B are independently H, alkyl or aryl; wherein R 4 is not an alkyl; wherein if R 2 , R 3 and R 4 are hydrogens and R 1 forms an oxo complex with M, n is 0 then M is Te; or if R 2 , R 3 and R 4 are hydrogens and R 1 is an oxygen that forms together with the metal an unsubstituted, saturated, 5 membered ring, n is 0 then M is Te; or if R 1 is an oxo group, and n is 0, R 2 and R 3 form together with the organometallic ring a fused benzene ring, R 4 is hydrogen, then M is Se; or if R 4 is an oxo group, and R 2 and R 3 form together with the organometallic ring a fused benzene ring, R 1 is oxygen, n is 0 and forms together with the metal a first 5 membered ring, substituted by an oxo group a to R 1 , and said ring is fused to a second benzene ring, then M is Te.