HOMOLEPTIC FE(II) COMPLEXES OF NEW 2,2' 6',2''-TERPYRIDINE LIGANDS WITH 4'-P-HYDROQUINONYL OR 4'-P-QUINONYL PENDANTS/

Preparations of three new ligands, 4'-p-dimethoxyphenyl-2,2':6',2''-te rpyridine (L(1)), 4'-p-hydroquinonyl-2,2':6',2''-terpyridine (L(2)) an d 4'-p-quinonyl-2,2':6',2''-terpyridine (L(3)), and their homoleptic i ron(II) complexes, [Fe(L)(2)](2+) (L= L(1)-L(3)), are described. The i ron complexes are highly coloured due to metal-to-ligand charge-transf er (MLCT) transitions, the energies of which do not vary significantly . Thus switching the 4'-groups has little effect on the energies of th e MLCT bands. The electrochemistries of the complexes have been charac terised by cyclic voltammetric and by bulk electrolysis experiments. E ach complex displays a combination of the redox processes expected for the Fe(tpy-)(2)(2+) (tPY-=2,2':6',2''-terpyridyl) core and for the tw o 4'-groups. Under protic conditions, the following redox reaction is chemically reversible: [Fe(L(2))(2)](2+)reversible arrow [Fe(L(3))(2)] (2+) +4H(+) +4e(-).