Patent ID: 8779133

Claim:
A compound represented by General Formula (1) or (2) and having a total of 15 to 110 carbon atoms: R 1 R 2 R 3 A (1) R 1 R 2 A-Y-AR 3 R 4 (2) wherein A is phosphorus or arsenic; R 1 , R 2 , R 3 and R 4 are each independently a pyridyl group having optionally different electron-withdrawing groups bonded to both positions meta to the atom A as well as hydrogen atoms bonded to both positions ortho to the atom A; and Y is a divalent group derived from a C 2-20 , optionally substituted and optionally heteroatom-containing, aliphatic, alicyclic or aromatic compound or from ferrocene, and provided that the nitrogen atom in the pyridine ring has the lowest number (1-position), the positions meta to the atom A are the 2-position and the 6-position, and the optionally different electron-withdrawing groups are bonded to both the 2-position and the 6-position, and the positions ortho to the atom A are the 3-position and the 5-position, and hydrogen atoms are bonded to both the 3-position and the 5-position.