Anion directed templated synthesis of mono- and di-condensed Schiff base compounds of Cu(II)

A mono-condensed Schiff base ligand has been prepared as the Cu(II) compound, [Cu2(L1)2(N3)2]·2H2O (1) (HL1 = 1-(N-3-methoxysalicylaldimine)-2-aminoethane), by the reaction of 1,2-diaminoethane, Cu(II) perchlorate and 3-methoxysalicyaldehyde in a 1:1:1 ratio in methanol, followed by the reaction with a large excess of NaN3. In absence of NaN3, a di-condensed compartmental ligand has been trapped as its Cu(II) compound [Cu2(L2)2⊂(H3NC2H4NH3)][{CuL2}2⊂(H3NC2H4NH3)](ClO4)4 (2) (H2L2 = N,N′-ethylenebis(3-methoxysalicylaldimine). Both compounds were characterized by elemental analyses, spectral and electrochemical studies and single crystal X-ray diffraction. In compound 2, Cu(II) has a square planar coordination geometry, while in 1, Cu(II) exhibits a distorted square pyramidal geometry (Addison parameter (τ) = 0.116). [CuL1(py)](ClO4) (3) is produced by following the preparation method of compound 1, but replacing NaN3 with pyridine. Formation of the compounds has been explained by an anion directed template effect.

Reaction of 1,2-diaminoethane, 3-methoxysalicyaldehyde and Cu(II) perchlorate in 1:1:1 ratio in methanol, followed by the addition with a large excess of NaN3, produces [Cu2(L1)2(N3)2]·2H2O (1). In the absence of NaN3, a tetradentate di-condensed compartmental ligand H2L2 (H2L2 = N,N′-ethylenebis(3-methoxysalicylaldimine) is trapped as its copper compound [Cu2(L2)2⊂(H3NC2H4NH3)][{CuL2}2⊂(H3NC2H4NH3)](ClO4)4 (2). Formation of the compounds has been explained by an anion directed cation templating effect.Figure optionsDownload as PowerPoint slideHighlights
► Cu(II) compounds with mono-condensed tridentate or tetradentate di-Schiff bases have been synthesized.
► The molecular structures of the two have been elucidated on the basis of X-ray crystallography.
► Formation of the compounds has been explained by an anion directed cation templating effect.