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 [(CuIIL)2NaI](ClO4) (1), [(CuIIL)2KI](ClO4) (2), [{CuIIL(H2O)}CaII(CuIIL)](ClO4)2 (3), [(CuIIL)(µ-ClO4)SrII{CuIIL(MeOH)0.6}](ClO4)·1.2MeOH (4) and [(CuIIL)(µ-ClO4)BaII{CuIIL(MeOH)}](ClO4)·MeOH (5), where H2L = N,N′-bis(3-ethoxysalicylidene)-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 L2− ligands. While NaI, KI and CaII are eight-coordinated, SrII and BaII are nine-coordinated due to additional coordination by an oxygen atom of a bridging perchlorate ligand. In all of 1–5, the two CuII and MI/II are positioned in almost linear way (CuII–MI/II–CuII angle range = 168.24–175.39°). 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 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.