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

Abstract

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.