N,N′-Bis(3-methoxysalicylidene)propane-1,2-diamine mononuclear 4f and heterodinuclear Cu-4f complexes: Synthesis, crystal structure and electrochemical properties

Reactions of H2L [H2L = N,N′-bis(3-methoxysalicylidene)propane-1,2-diamine] and Ln(NO3)3 · 6H2O give rise to two different mononuclear 4f complexes, namely, {[(H2L)La(NO3)3(MeOH)] · H2O}n (1) and [(H2L)Nd(NO3)3] (2). Further additions of Cu(Ac)2 · H2O to the mononuclear 4f complexes yield expected heterodinuclear Cu-4f complexes [LCu(Me2CO)Ln(NO3)3] (3, Ln = Nd; 4, Ln = Eu; 5, Ln = Dy). Complex 1 is a unique 1D polymeric chain structure, and 2 is one of the few structurally characterized discrete hexadentate salen-type mononuclear 4f complexes. Complexes 3–5 are similar to their analogues. However, they are prepared by a reversed synthetic route in contrast to their isomorphic complexes. Electrochemical behavior of heterodinuclear Cu-4f complexes 3–5 has been examined by cyclic voltammetry in acetonitrile. The redox potential of heterodinuclear Cu-4f complexes 3–5 shows significant anodic shift comparing to that of mononuclear copper complex (LCu). A tendency of anodic shift was observed in a sequence of 3 < 4 < 5. This results from the modulating effect of coordination geometry around Cu(II) ion on redox potential.