Divalent manganese, cobalt and nickel chloride complexes with neutral N2- and N3-based ligands derived from 2-pyridinecarbaldehyde: Synthesis, structural features and spectroscopic studies. (17th February 2016)

• Record Type: Journal Article
• Authors: Buvaylo, Elena A.; Melnyk, Andrii K.; Trachevsky, Vladimir V.; Vassilyeva, Olga Yu.; Skelton, Brian W.
• Is Part Of: Polyhedron. Volume 105(2016)
• Page Start: 238
• Page End: 245
• Publication Date: 2016-02-17
• Subjects: 2-Pyridinecarbaldehyde -- Schiff base ligand -- Mn(II), Co(II) and Ni(II) metal complexes -- X-band EPR -- Co(II) low-spin and high-spin complexes; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2015.12.025
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: The Schiff base ligand bearing a protonated carboxylic group imposes M II N4 Cl2 coordination in M(HL1)2 Cl2 ·Solv (M = Mn, Co, Ni) complexes and serves as a source of 2-pyridinecarbaldehyde to produce heterocyclic methanone ligand L2 in the interaction of HL1 with ammonium salt. Electronic properties of the complexes were probed by EPR spectroscopy. Abstract: A series of dihalide M(II) mononuclear complexes in a cis configuration, Mn(HL1)2 Cl2 ·CH3 OH·H2 O (1 ), Co(HL1)2 Cl2 ·CH3 OH·H2 O (2 ), Ni(HL1)2 Cl2 ·2H2 O (3 ) and CoL2Cl2 ·0.5dmf (4 ) (HL1 – Schiff base ligand 4-N-(2′-pyridylimine)benzoic acid; L2 – pyridin-2-yl(3-(pyridin-2-yl)imidazo[1, 5- a ]pyridin-1-yl) methanone, both formed in situ from 2-pyridinecarbaldehyde), have been obtained as single crystals and characterized by elemental analysis, IR and EPR spectroscopy, and single-crystal X-ray diffraction techniques. The neutral M(L1)2 Cl2 and CoL2Cl2 molecules in1 –3 and4, respectively, show no crystallographically imposed symmetry with the metal atoms in a MN4 Cl2 distorted octahedral (1 –3 ) and CoN3 Cl2 (4 ) elongated trigonal–bipyramidal geometries. In the crystal lattice molecules of1 –3 are arranged in columns propagating along the c axis; the structure of4 can be described as layers of CoL2Cl2 and dmf molecules alternating along the a axis. The minimum M⋯M separations in a column (1 –3 ) and inside a layer (4 ) are above 8 Å. The X-band solid-state EPR spectra of1 at room temperature and 77 K exhibit broad fine structure signals at 1600 and 3000 G ( g eff ∼ 4.14 and 2.22, respectively) resulting from ZFS of the spin states for the high-spin d 5 metal ion. The solid-state EPR spectra of2 are temperature dependent showing a wide unresolved line at g eff ∼ 2.09 at room temperature and a very broad signal (Δ H pp = 2500 G) at g eff ∼ 4.21 at 77 K. The Ni analogue3 is EPR-silent. The EPR spectra of4 at both temperatures show a broad asymmetrical signal centred at g ∼ 2 suggesting the low-spin configuration; the line width is nearly independent of temperature.