The magnetic exchange interaction in bi- and tetranuclear copper(II) complexes with the bis-azomethine of 1, 3-diaminopropanol-2 and 4-hydroxy-3-formylcoumarin with an azide exogenous bridge. (15th October 2017)

• Record Type: Journal Article
• Authors: Pankov, Ilia V.; Shcherbakov, Igor N.; Tkachev, Valeriy V.; Levchenkov, Sergey I.; Popov, Leonid D.; Lukov, Vladimir V.; Aldoshin, Sergey M.; Kogan, Victor A.
• Is Part Of: Polyhedron. Volume 135(2017)
• Page Start: 237
• Page End: 246
• Publication Date: 2017-10-15
• Subjects: Cu(II) complex -- Magnetic exchange interaction -- Crystal structure -- DFT calculations -- Broken symmetry approach; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2017.07.014
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: Cu(II) bi- and tetranuclear complexes with a Schiff base ligand – the bis -azomethine of 1, 3-diaminopropanol-2 and 4-hydroxy-3-formylcoumarin – and an exogenous μ2-1, 1 -azide bridge were synthesized and characterized by X-ray analysis, magnetic measurements and DFT modeling. Abstract: By the reaction of Cu(II) perchlorate with the condensation product of 1, 3-diamino-2-propanol and 4-hydroxy-3-formylcoumarin (H3 L ) in the presence of sodium azide, a tetranuclear copper(II) complex with the composition [Cu2 L(μ2-1, 1 -N3 )]2 (I ) was obtained. On crystallization from a pyridine solution, the crystalline adduct [Cu2 L(μ2 -N3 )(py)2 ] (II ) (py = pyridine) was obtained and further characterized by XRD. The copper ions in (II ) are coordinated by ONO'NO donor atoms of the triply deprotonated pentadentate ligand and the azide anion is coordinated in an asymmetric µ2-1, 1 fashion, favoring a "roof"-like conformation of the molecule. The pyridine molecules are coordinated to each copper center, completing the distorted square-pyramidal coordination environment, but in a different way – for one copper ion the solvent molecule populates an apical position, for the other – a position in the basal plane. The tetranuclear complex is formed by linking two binuclear [Cu2 L] units by two bridging μ2–1, 1 –N3 groups in a head-to-tail fashion. The temperature dependence of the magnetic susceptibility was studied for bothI andII samples, showing a medium strength overall antiferromagnetic exchange forI and a weak ferromagnetic one with 2 J = +5 cm −1 forII . Two major superexchange pathways inI – through an alkoxide oxygen atom of the polydenate ligand and through the bridging azide-anion are characterized by opposite magnetic interaction characters – antiferromagnetic (2 J O = −328 cm −1 ) and ferromagnetic (2 J N = +132 cm −1 ), correspondingly. Quantum-chemical modeling using the broken symmetry approach was performed forII and possible binuclear isomers ofI, differing in the azide-anion coordination mode and conformation of the polydentate ligand, and for two possible tetranuclear dimers.