868368-43-8Relevant articles and documents
Probing the electronic factors responsible for the cyclic electron-transfer induced isomerism fac ? mer: Synthesis, electrochemical and spectroscopic studies of fac-[Mn(CO)3(L′-L′)L] 0/+ complexes
Pereira, Cid,Ferreira, Heber G.,Schultz, Mario S.,Milanez, Juliana,Izidoro, Marta,Leme, Paulo C.,Santos, Regina H.A.,Gambardella, Maria Teresa P.,Castellano, Eduardo E.,Lima-Neto, Benedito S.,Carlos, Rose M.
, p. 3735 - 3744 (2008/10/09)
Spectroscopic (IR, 31P NMR and UV-Vis) and electrochemical studies on fac-[Mn(CO)3(L′-L′)(L)]0/+,where L′-L′ = 1,2-bis(diphenylphosphino)ethane (dppe) or 1,10-phenanthroline (phen) and L = bromide, triflate, imidazole (im), isonicotinamide (isn) or N-(2-hydroxyethyl)isonicotinamide (heisn), were undertaken to understand the effect of various ligands on the CO-Mn-L and CO-Mn-(L′-L′) bonding characteristics of these complexes. Crystal structures for L = triflate/L′-L′ = dppe, L = triflate/L′- L′ = phen and L = isn/L′-L′ = phen are reported and they show that the two Mn-O(OSO2CF3) and Mn-N(isn) distances are similar. The tricarbonyl complexes exhibit two major bands in the 250-300 and 350-450 nm region of the UV-Vis spectrum. The lowest energy bands have been assigned as a contribution from both the metal-centered (MC) and metal to ligand (dπ → L′-L′) charge transfer (MLCT) transitions. The energy of this maximum absorption decreases in the order Br- ～ triflate > im > isn ～ heisn. The cyclic four-component mechanism fac-Mn(I)→-efac-Mn(II)→mer-Mn(II)→+emer-Mn(I)→fac-Mn(I) was observed at room temperature by voltammetric techniques for all the cases. On the basis of d metal orbital splitting, an electronic molecular orbital diagram is proposed. In this model, the ligands along the z-axis play a relevant role in the reverse of the HOMO energies of the fac/mer isomers by stabilizing the metal dz2 orbital relative to dxy in mer-Mn(II).
