Crystal structures of trans-diaqua(3-R-1,3,5,8,12-pentaazacyclotetradecane)copper(II) isophthalate hydrates (R = benzyl or pyridin-3-ylmethyl)

Abstract

The asymmetric units of the title compounds, trans-diaqua(3-benzyl-1,3,5,8,12-pentaazacyclotetradecane-κ4N1,N5,N8,N12)copper(II) isophthalate monohydrate, [Cu(C16H29N5)(H2O)2](C8H4O4)·H2O, (I), and trans-diaqua[3-(pyridin-3-ylmethyl)-1,3,5,8,12-pentaazacyclotetradecane-κ4N1,N5,N8,N12]copper(II) isophthalate 0.9-hydrate, [Cu(C15H28N6)(H2O)2](C8H4O4)·0.9H2O, (II) consist of one diaqua macrocyclic cation, one dicarboxylate anion and uncoordinated water molecule(s). In each compound, the metal ion is coordinated by the four secondary N atoms of the macrocyclic ligand and the mutually trans O atoms of the water molecules in a tetragonally distorted octahedral geometry. The average equatorial Cu—N bond lengths are significantly shorter than the average axial Cu—O bond lengths [2.020 (9) versus 2.495 (12) Å and 2.015 (4) versus 2.507 (7) Å for (I) and (II), respectively]. The coordinated macrocyclic ligand in the cations of both compounds adopts the most energetically favorable trans-III conformation. In the crystals, the complex cations and counter-anions are connected via hydrogen-bonding interactions between the N—H groups of the macrocycles and the O—H groups of coordinated water molecules as the proton donors and the O atoms of the carboxylate as the proton acceptors. Additionally, as a result of O—H...O hydrogen bonding with the coordinated and water molecules of crystallization, the isophthalate dianions form layers lying parallel to the (\overline{1}01) and (100) planes in (I) and (II), respectively.

Keywords

• crystal structure
• azamacrocyclic ligand
• azacyclam
• copper
• isophthalic acid
• hydrogen bonds