Crystal engineering of salen type cerium complexes tuned by various cerium counterions

A series of five new salen type cerium complexes, namely [Ce(H2L)2CH3OH](PF6)3·2H2O·CH2Cl2 (1), [Ce(IV)L2] (2), [Ce(H2L)(NO3)3CH3OH] (3), [Ce2(H2L)3(NO3)6]·4H2O (4) and {[Ce(H2L)2(NO3)2](PF6)·2CH3CN}n (5) (H2L = N,N′-bis(3-methoxysalicylidene)cyclohexane-1,2-diamine), have been isolated by reactions of H2L with various cerium salts and/or NH4PF6. All complexes 1–5 have been fully characterized by elemental analysis, FT-IR spectroscopy, UV spectroscopy, powder X-ray diffraction, TG–DSC analysis, and single-crystal X-ray diffraction. X-ray crystallographical analysis reveals that complexes 1–3 are of discrete mononuclear structures, 4 is of a discrete binuclear structure, and complex 5 is of a unique quartz 3D topological structure. The electrochemical behavior of this series of salen type cerium complexes has been examined by cyclic voltammetry in acetonitrile. Cyclic voltammograms of complexes 1 and 3–5 show two quasi-reversible redox processes within the electrochemical window of acetonitrile.