Linear trinuclear copper(II)-alkali/alkaline earth metal compounds derived from a compartmental ligand

Abstract

The work in this investigation deals with syntheses, crystal structures and ESI-MS positive of five compounds of composition [(Cu II L)2Na I ](ClO4) (1), [(Cu II L)2K I ](ClO4) (2), [{Cu II L(H2O)}Ca II (Cu II L)](ClO4)2 (3), [(Cu II L)(µ-ClO4)Sr II {Cu II L(MeOH)0.6}](ClO4)•1.2MeOH (4) and [(Cu II L)(µ-ClO4)Ba II {Cu II L(MeOH)}](ClO4)•MeOH (5), where H2L = N,N'-bis(3ethoxysalicylidene)-1,4-butanediamine. The s-block metal ion in all of these five compounds occupies an O8 (four phenoxo and four ethoxy) site provided by two L 2ligands. While Na I , K I and Ca II are eight-coordinated, Sr II and Ba II are nine-coordinated due to additional coordination by an oxygen atom of a bridging perchlorate ligand. In all of 1-5, the two Cu II and M I/II are positioned in almost linear way (Cu II-M I/II-Cu II angle range = 168.24-175.39º). The geometries of the coordination environments have been understood from SHAPE analyses. A disagreement has been observed for the first time between the results of SHAPE analyses and Addison's geometric parameter for the pentacoordinated environment. Some interesting structural features regarding composition, metal-ligand bond lengths and twisting of the aromatic rings have been observed. UV-Vis spectra indicates two d-d absorption of copper(II) centers in each of the five compounds. ESI-MS positive reveals the appearance of some tri/di/mononuclear ions.