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The new copper(II) complex, namely, di-μ-chlorido-bis­{chlorido­[meth­yl(pyri­din-2-yl­methyl­idene)amine-κ²N,N′]copper(II)}, [Cu2Cl4(C7H8N2)2], (I), with the ligand 2-pyridyl­methyl-N-methyl­imine (L, a product of Schiff base condensation between methyl­amine and 2-pyridine­carbaldehyde) is built of discrete centrosymmetric dimers. The coordination about the CuII ion can be described as distorted square pyramidal. The base of the pyramid consists of two nitro­gen atoms from the bidentate chelate L [Cu—N = 2.0241 (9), 2.0374 (8) Å] and two chlorine atoms [Cu—Cl = 2.2500 (3), 2.2835 (3) Å]. The apical position is occupied by another Cl atom with the apical bond being significantly elongated at 2.6112 (3) Å. The trans angles of the base are 155.16 (3) and 173.79 (2)°. The Cu...Cu separation in the dimer is 3.4346 (3) Å. In the crystal structure, the loosely packed dimers are arranged in stacks propagating along the a axis. The X-band polycrystalline 77 K EPR spectrum of (I) demonstrates a typical axial pattern characteristic of mononuclear CuII complexes. Compound (I) is redox active and shows a cyclic voltammetric response with E1/2 = −0.037 V versus silver–silver chloride electrode (SSCE) assignable to the reduction peak of CuII/CuI in methanol as solvent. [ABSTRACT FROM AUTHOR]

A new organic-inorganic hybrid salt [L]2[MnCl4] (I) where L+ is the 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium cation, is built of discrete organic cations and tetrachloridomanganate(II) anions. The L+ cation was formed in situ in the oxidative cyclocondensation of 2-pyridinecarbaldehyde and CH3NH2·HCl in methanol. The structure was refined as a two-component twin using PLATON (Spek, 2020[Spek, A. L. (2020). Acta Cryst. E76, 1-11.]) to de-twin the data. The twin law (-1 0 0 0 - 1 0 0.5 0 1) was applied in the refinement where the twin component fraction refined to 0.155-(1). The compound crystallizes in the space group P21/c with two crystallographically non-equivalent cations in the asymmetric unit, which possess similar structural conformations. The fused pyridinium and imidazolium rings of the cations are virtually coplanar [dihedral angles are 0.89-(18) and 0.78-(17)°]; the pendant pyridyl rings are twisted by 36.83-(14) and 36.14-(13)° with respect to the planes of the remaining atoms of the cations. The tetrahedral MnCl42- anion is slightly distorted with the Mn-Cl distances falling in the range 2.3469-(10)-2.3941-(9)-Å. The distortion value of 0.044 relative to the ideal tetrahedron was obtained by continuous shape measurement (CShM) analysis. In the crystal, the cations and anions form separate stacks propagating along the a-axis direction. The organic cations display weak π-π stacking. The anions, which are stacked identically one above the other, demonstrate loose packing; the minimum Mn...Mn separation in the cation stack is approximately 7.49-Å. The investigation of the fluorescent properties of a powdered sample of (I) showed no emission. X-band EPR data for (I) at 293 and 77-K revealed broad fine structure signals, indicating moderate zero-field splitting. [ABSTRACT FROM AUTHOR]

A series of CuII halide complexes, Cu(HL1)Cl2·CH3OH (1), [Cu(L1)Cl]2·H2O (2), [Cu(HL2)Cl2]2·2DMF (3), [Cu(HL2)2Cl]nCln·2nH2O (4), and [Cu(L3)Cl]n (5), containing pyridyliminebenzoic acids HL1, HL2, and HL3 derived from o‐, m‐, and p‐aminobenzoic acids, respectively, have been obtained as single crystals and characterized by elemental analysis, IR, EPR spectroscopy, magnetic measurements, and single‐crystal X‐ray diffraction techniques. The results obtained show the formation of molecular (1), dimeric (2, 3), and polymeric structures (4, 5) based on chloride (1–4) and carboxylate bridges (5) with copper(II) ions in the square pyramidal geometry of varying degrees of distortion. In the case of 2 and 5 the ligand deprotonation was completely achieved even in the absence of a base. The closest Cu···Cu separations are found in the crystal lattices of the polymer 5 (3.33 Å) and dimers 2 (3.35 Å) and 3 (3.38 Å). The X‐band polycrystalline EPR spectra of 1–3 with typical axial patterns show no indication of exchange interactions between copper ions in the range 295–77 K. The observed rhombic features of the EPR spectra of 4 arise from the coupling of g‐tensors from differently oriented CuII coordination polyhedra in the solid state. A characteristic spin‐triplet EPR spectrum of 5 at 77 K was simulated by using the spin‐Hamiltonian parameters for S = 1, gx = 2.08, gy = 2.11, gz = 2.37 and the value of the zero‐field splitting parameter D of 0.137 cm–1. Magnetic susceptibility measurements revealed antiferromagnetic (1–3, 5) and ferromagnetic coupling (4) between the metal atoms at low temperatures. Theoretical methods were employed to provide additional insight into magnetic interactions in the studied compounds. [ABSTRACT FROM AUTHOR]

Comparative properties of lecithin-based liposomes prepared from the mixed phospholipids of sunflower seeds, soybean and egg yolk were investigated by electron paramagnetic resonance (EPR) spectroscopy. For these investigations, stable nitroxide radicals, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl 5,7-dimethyladamantane-1-carboxylate (DMAC-TEMPO), 5-doxylstearic acid (5-DSA) and 16-doxylstearic acid (16-DSA) were used as spin probes. Binding of the spin probes to the liposome membranes resulted in a substantial increase of the apparent rotational diffusion correlation times. The EPR spectra of the incorporated nitroxides underwent temperature-dependent changes. For every spin probe, values of apparent enthalpy and entropy of activation were calculated from the temperature dependence of rotational diffusion correlation timesviaArrhenius equation. In case of DMAC-TEMPO, the data point to differences between the phospholipid bilayer of liposomes derived from sunflower and soy lecithin, and some similarity between the sunflower and egg yolk liposomes. Anisotropic hyperfine interaction constants of DMAC-TEMPO and 16-DSA included in the liposomes have been analyzed and attributed to different micropolarity of the surroundings of the spin probes. The kinetics of EPR signal decay of DMAC-TEMPO in the presence of 2,2′-azobis(2-amidinopropane) suggest the better stability of the sunflower liposomes to lipid peroxidation as compared to the liposomes prepared from soy lecithin. [ABSTRACT FROM PUBLISHER]

A new organic-inorganic hybrid salt [L]2[MnCl4] (I) where L+ is the 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium cation, is built of discrete organic cations and tetrachloridomanganate(II) anions. The L+ cation was formed in situ in the oxidative cyclocondensation of 2-pyridinecarbaldehyde and CH3NH2·HCl in methanol. The structure was refined as a two-component twin using PLATON (Spek, 2020[Spek, A. L. (2020). Acta Cryst. E76, 1-11.]) to de-twin the data. The twin law (-1 0 0 0 - 1 0 0.5 0 1) was applied in the refinement where the twin component fraction refined to 0.155-(1). The compound crystallizes in the space group P21/c with two crystallographically non-equivalent cations in the asymmetric unit, which possess similar structural conformations. The fused pyridinium and imidazolium rings of the cations are virtually coplanar [dihedral angles are 0.89-(18) and 0.78-(17)°]; the pendant pyridyl rings are twisted by 36.83-(14) and 36.14-(13)° with respect to the planes of the remaining atoms of the cations. The tetrahedral MnCl42- anion is slightly distorted with the Mn-Cl distances falling in the range 2.3469-(10)-2.3941-(9)-Å. The distortion value of 0.044 relative to the ideal tetrahedron was obtained by continuous shape measurement (CShM) analysis. In the crystal, the cations and anions form separate stacks propagating along the a-axis direction. The organic cations display weak π-π stacking. The anions, which are stacked identically one above the other, demonstrate loose packing; the minimum Mn...Mn separation in the cation stack is approximately 7.49-Å. The investigation of the fluorescent properties of a powdered sample of (I) showed no emission. X-band EPR data for (I) at 293 and 77-K revealed broad fine structure signals, indicating moderate zero-field splitting. [ABSTRACT FROM AUTHOR]

The new copper(II) complex, namely, di-μ-chlorido-bis-{chlorido-[meth-yl(pyri-din-2-yl-methyl-idene)amine-κ 2 N , N ']copper(II)}, [Cu 2 Cl 4 (C 7 H 8 N 2 ) 2 ], (I), with the ligand 2-pyridyl-methyl- N -methyl-imine ( L , a product of Schiff base condensation between methyl-amine and 2-pyridine-carbaldehyde) is built of discrete centrosymmetric dimers. The coordination about the Cu II ion can be described as distorted square pyramidal. The base of the pyramid consists of two nitro-gen atoms from the bidentate chelate L [Cu-N = 2.0241 (9), 2.0374 (8) Å] and two chlorine atoms [Cu-Cl = 2.2500 (3), 2.2835 (3) Å]. The apical position is occupied by another Cl atom with the apical bond being significantly elongated at 2.6112 (3) Å. The trans angles of the base are 155.16 (3) and 173.79 (2)°. The Cu ⋯ axis. The X-band polycrystalline 77 K EPR spectrum of (I) demonstrates a typical axial pattern characteristic of mononuclear Cu a axis. The X-band polycrystalline 77 K EPR spectrum of (I) demonstrates a typical axial pattern characteristic of mononuclear Cu II complexes. Compound (I) is redox active and shows a cyclic voltammetric response with E 1/2 = -0.037 V versus silver-silver chloride electrode (SSCE) assignable to the reduction peak of Cu II /Cu I in methanol as solvent., (© Vassilyeva et al. 2020.)

A new organic-inorganic hybrid salt [ L ] 2 [MnCl 4 ] (I) where L + is the 2-methyl-3-(pyridin-2-yl)imidazo[1,5- a ]pyridinium cation, is built of discrete organic cations and tetra-chlorido-manganate(II) anions. The L + cation was formed in situ in the oxidative cyclo-condensation of 2-pyridine-carbaldehyde and CH 3 NH 2 ·HCl in methanol. The structure was refined as a two-component twin using PLATON (Spek, 2020 ▸) to de-twin the data. The twin law (-1 0 0 0 - 1 0 0.5 0 1) was applied in the refinement where the twin component fraction refined to 0.155 (1). The compound crystallizes in the space group P 2 1 / c axis direction. The organic cations display weak π-π stacking. The anions, which are stacked identically one above the other, demonstrate loose packing; the minimum Mn⋯Mn separation in the cation stack is approximately 7.49 Å. The investigation of the fluorescent properties of a powdered sample of (I) showed no emission. X-band EPR data for (I) at 293 and 77 K revealed broad fine structure signals, indicating moderate zero-field splitting.4 2- anion is slightly distorted with the Mn-Cl distances falling in the range 2.3469 (10)-2.3941 (9) Å. The distortion value of 0.044 relative to the ideal tetra-hedron was obtained by continuous shape measurement (CShM) analysis. In the crystal, the cations and anions form separate stacks propagating along the a- axis direction. The organic cations display weak π-π stacking. The anions, which are stacked identically one above the other, demonstrate loose packing; the minimum Mn⋯Mn separation in the cation stack is approximately 7.49 Å. The investigation of the fluorescent properties of a powdered sample of (I) showed no emission. X-band EPR data for (I) at 293 and 77 K revealed broad fine structure signals, indicating moderate zero-field splitting., (© Vassilyeva et al. 2020.)