New organometallic Ru(II) and Fe(II) complexes with tetrathia-[7]-helicene derivative ligands

A series of organometallic complexes possessing new tetrathia-[7]-helicene nitrile derivative ligands [TH-7] as chromophores, of general formula [MCp(P-P)(NC{TH-[7]-Y}Z)][PF6] (M = Ru, Fe, P-P = DPPE, Y = H, NO2, Z = H, C≡N; M = Ru, L-L = 2PPh3, Y = H, Z = H) has been synthesized and fully characterized. 1H NMR, FT-IR and UV-Vis. spectroscopic data were analyzed with in order to evaluate the existence of electronic delocalization from the metal centre to the coordinated ligand to have some insight on the potentialities of these new compounds as non-linear optical molecular materials. Slow crystallization of compound [RuCp(PPh3)2(NC{TH-[7]-H}H)][PF6] 2Ru revealed an interesting isomerization of the helical ligand with formation of two carbon-carbon bonds between the two terminal thiophenes, leading to the total closure of the helix (2*Ru).