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 [CuIIL1NaI(μ-BF4)2NaIL1CuII]·2CH3COCH3 (1), [CuIIL1NaI(NO3)(MeOH)] (2), [CuIIL1ZnII(H2O)2L1CuII](ClO4)2 (3), [CuII(MeOH)L1ZnIICl2] (4), [CuIIL1CdII(H2O)(MeOH)2](ClO4)2 (5) and [CuIIL1CdIICl2(MeOH)]·[CuII(MeOH)L1CdIICl2] (6), where H2L1 is N,N′-ethylenebis(3-methoxysalicylaldimine). The crystal systems and space groups are as follows: 1 and 2, triclinic, P1¯; 3 and 6, monoclinic, P21/c; 4, orthorhombic, P212121; 5, monoclinic, C2/c. While the N(imine)2O(phenoxo)2 compartment accommodates the copper(II) center, the larger and open O(phenoxo)2O(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 CuIIZnII pairs are monophenoxo-bridged, compound 1 is a tetranuclear system in which two diphenoxo-bridged CuIINaI units are interlinked by two tetrafluoroborate moieties, and compound 6 is a [2×1+2×1] co-crystal of two dinuclear CuIICdII units. The solid state electronic spectra of compounds 1–6 and also the mononuclear compound [CuIIL1(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.

Graphical abstractThis report presents the syntheses, crystal structures, characterization and electronic spectroscopy of six heteronuclear copper(II) complexes derived from the N,N′-ethylenebis(3-methoxysalicylaldimine) ligand. Solid state electronic spectra of the compounds are correlated with the displacement of the copper(II) centers from the basal N2O2 plane.Figure optionsDownload full-size imageDownload as PowerPoint slide