Syntheses, crystal structures and spectroscopy of di/tri/tetranuclear discrete and co-crystalline copper(II)-NaI/ZnII/CdII complexes derived from a compartmental ligand: Inconsistency in the shifting of the copper(II) d-d band

The work in this report presents the syntheses, characterization, crystal structures and electronic spectra of the six heteronuclear complexes [(CuLNaI)-L-II-Na-1(mu-BF4)2Na(I)L(1)Cu(II)]center dot 2CH(3)COCH(3) (1), [(CuLNaI)-L-II-Na-1(NO3)(MeOH)] (2), [(CuLZnII)-L-II-Zn-1(H2O)(2)(LCuII)-Cu-1](ClO4)(2) (3), [Cu-II(MeOH)(LZnCl2)-Zn-1-Cl-II] (4), [(CuLCdII)-L-I-Cd-1(H2O)(MeOH)(2)](ClO4)(2) (5) and [(CuLCdCl2)-L-II-Cd-1-Cl-II(MeOH)]center dot[Cu-II(MeOH)(LCdCl2)-Cd-1-Cl-II] (6), where H2L1 is N,N'-ethylenebis(3-methoxysalicylaldimine). The crystal systems and space groups are as follows: 1 and 2, triclinic, P (1) over bar; 3 and 6, monoclinic, P2(1)/c; 4, orthorhombic, P2(1)2(1)2(1); 5, monoclinic, C2/c. While the N(imine)(2)O(phenoxo)(2) compartment accommodates the copper(II) center, the larger and open O(phenoxo)(2)O(methoxy)(2) compartment interacts with the second metal ion. Compounds 2, 4 and 5 are diphenoxo-bridged dinuclear systems, compound 3 is a trinuclear system in which the two (CuZnII)-Zn-II pairs are monophenoxo-bridged, compound 1 is a tetranuclear system in which two diphenoxo-bridged (CuNaI)-Na-II units are interlinked by two tetrafluoroborate moieties, and compound 6 is a [2x1+2x1] co-crystal of two dinuclear (CuCdII)-Cd-II units. The solid state electronic spectra of compounds 1-6 and also the mononuclear compound [(CuL1)-L-II(H2O)] have been recorded in the range 400-800 nm. While correlating the d-d band position with the structural parameters and a previously proposed correlation, some inconsistency has been found, indicating that this area should be explored further. (c) 2013 Elsevier Ltd. All rights reserved.