Copper(II) coordination compounds containing chiral functional groups as pendants: Syntheses, crystal structures, and physical properties

Chiral mononuclear copper(II) complexes, [Cu(LR,R)(ClO4)2] (1) and [Cu(LS,S)(ClO4)2] (2) and chiral polymeric compound, [Cu(LS,S)(CrO4)]·6H2O (3) have been synthesized (LR,R/S,S = 1,8-di((R/S)-α-methylbenzyl)-1,3,6,8,10,13-hexaazacyclotetradecane). These compounds were characterized by X-ray crystallography, circular dichroism, and molecular magnetism. The copper(II) ions in 1–3 have a distorted octahedral geometry by coordinating four nitrogens of a macrocyclic ligand in a square planar conformation and two oxygens in the axial positions. 3 exhibits weak antiferromagnetic coupling via the chromate ions within the 1D chain. The circular dichroism (CD) spectrum of 1 has shown a negative and positive peak at 474 and 562 nm, and that of 2 has displayed an enantiomeric pattern. The CD spectrum of 3 appears positive signal above 610 nm.

Graphical abstractChiral mononuclear copper(II) complexes (1, 2) and chiral polymeric compound 3 have been synthesized. All copper(II) ions have a distorted octahedral geometry by coordinating four nitrogens and two oxygens. 3 exhibits weak antiferromagnetic coupling via the chromate ions. The CD spectra of 1 and 2 are shown an enantiomeric pattern.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights►Chiral mononuclear copper(II) complexes 1 and 2 and chiral polymeric compound 3 have been synthesized and characterized. ►The X-ray single-crystal structures of 1–3 are obtained and analyzed in detail. ►The magnetic properties of 3 are measured and analyzed in detail. ►The circular dichroism spectra of 1–3 are measured and analyzed in detail.