"Specific examples of substituents of rings A1 and A2 each forming the ligand of general formula (K) include halogen atoms such as chlorine atom, bromine atom, iodine atom and fluorine atom; substituted or unsubstituted alkyl group such as methyl group, ethyl group, propyl group, butyl group, s-butyl group, t-butyl group, pentyl group, hexyl group, heptyl group, octyl group, stearyl group, trichlor" . . . .