LAUSR

Abstract This paper presents the syntheses, crystal structures and electrospray ionization mass spectra (ESI-MS) of four copper(II)–s-block metal ion compounds of composition [{CuIILNaI(H2O)2}(CuIIL)](ClO4) (1), [(CuIIL)2CaII](ClO4)2·2CH3CN·H2O (2), [CuIILSrII(ClO4)2(H2O)]n (3) and [CuIILBaII(ClO4)2(H2O)]n (4), where H2L is the compartmental acyclic Schiff base ligand, obtained on [2 + 1] condensation of 3-ethoxysalicylaldehyde and trans-1,2-diaminocyclohexane. Compound 1 is a [2 × 1 + 1 × 1] cocrystal of one dinuclear [CuIILNaI(H2O)2]+ moiety and one mononuclear [CuIIL] moiety; the reason of cocrystallization is the hydrogen bonding interaction of a coordinated water molecule of the dinuclear unit with the O(phenoxo)2O(ethoxy)2 compartment of the mononuclear unit. [(CuIIL)2CaII](ClO4)2·2CH3CN·H2O (2) is a trinuclear, non-sandwiched compound where the second metal ion (CaII) is situated in between two O(phenoxo)2O(ethoxy)2 compartments of two [CuIIL] moieties. [CuIILSrII(ClO4)2(H2O)]n (3) and [CuIILBaII(ClO4)2(H2O)]n (4) are isomorphous and dinuclear CuIIMII (M = Sr or Ba) based one-dimensional systems, where polymerization takes place through the perchlorate ligands. A number of peaks are observed in the ESI-MS and those are well assigned. Although the compositions of 1, 2 and 3/4 are different, the ESI-MS of all the four compounds reveal the appearance of trinuclear, dinuclear and mononuclear ions. The peculiar/interesting aspects of the four compounds are discussed.