Search

A series of Ba–MII complexes with allylmalonic acid anions (Amal) [BaMII(Amal)2(H2O)3]n (MII = Mn (1), Co (2), Cu (3), and Zn (4)) were synthesized by the reaction of the corresponding transition metal sulfates and barium allylmalonate. The complexes were characterized by IR and EPR spectroscopy, elemental analysis, magnetochemical and solid phase thermal decomposition studies as well as powder and single-crystal X-ray crystallography. The main structural block {MII(Amal)2(H2O)x} (x = 1 for M = Cu, x = 2 for M = Mn, Co, and Zn) in 1–4 is formed by two chelate allylmalonate anions and water molecule(s), which are surrounded by Ba2+ ions. The magnetic measurements of paramagnetic compounds revealed weak ferromagnetic interactions between copper(II) ions in 3, and slow magnetic relaxation in non-zero field (HDC = 1500 Oe) for 2. According to the TGA data of 1–4, they are decomposed via different pathways in the case of MnII, CoII, CuII, and ZnII since the metal ions catalyze different types of processes. However, all the complexes undergo polymerization of the allyl fragment. [ABSTRACT FROM AUTHOR]

The interaction of the pivalate complexes of iron(III), [Fe3O(Piv)6(H2O)3]·HPiv, and cadmium(II), [Cd(Piv)2], in Et2O resulted in one more type of "ferric wheel" family complex, namely [Fe8(Piv)16{Cd(Piv)2}(μ-OH)8]·Et2O (1). The complex is an octanuclear iron(III) wheel with a {Cd(Piv)2} moiety asymmetrically incorporated into the ring. [ABSTRACT FROM AUTHOR]

A new 1D coordination polymer {[Ba2Cr2(OH)2(Me2mal)4(H2O)6]·2H2O}n (1) containing binuclear structural units [Cr2(OH)2(Me2mal)4]4– was synthesized by the reaction of an inorganic chromium(III) salt with a barium salt of dimethylmalonic acid (H2Me2mal). Depending on the nature of the counterion of the starting chromium salt, the addition of an excess of H2Me2mal to the reaction mixture resulted in the formation of a new 2D polymer {[Ba2Cr(Me2mal)2(HMe2mal)2(NO3)(H2O)5]·3.55H2O}n (2) containing mononuclear units [Cr(Me2mal)2(HMe2mal)2]3– or a new 3D polymer {[BaCr(Me2mal)2(HMe2mal)(H2O)2]·H2O}n (3) composed of two types of mononuclear units, [Cr(Me2mal)2(HMe2mal)2]3– and [Cr(Me2mal)2(H2O)2]–. Magnetic measurements, EPR spectroscopy studies, and quantum chemical calculations demonstrated that compound 1 exhibits ferromagnetic exchange interactions between CrIII ions in the binuclear unit (2J = 6.77 cm–1) and displays slow relaxation of the magnetization in external dc‐magnetic field. Compound 3 has porous structure, with channels occupied by solvent water molecules. However, the dehydration of 3 is accompanied by a structural rearrangement and the collapse of the porous structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • Binuclear, polymeric binuclear, and 16-nuclear copper(II) complexes with Chinese lantern building blocks were studied by EPR. • EPR spectroscopy studies were performed in the X-, Q- and W-ranges. • Electronic exchange between two copper(II) atoms forming dimers were found. • No interactions between adjacent binuclear fragments were revealed. In this work, binuclear, polymeric binuclear, and molecular 16-nuclear copper(II) complexes [Py 2 Cu 2 (Piv) 4 ] (1), {[(EtOH) 2 Cu 2 (Chda) 2 ]·EtOH} n (2) and [K 2 (H 2 O) 6 (Py) 8 Cu 16 (OH) 2 (Chda) 16 ]·EtOH·MeCN·3H 2 O (3) (piv is pivalate, Chda is 1,1-cyclohexanediacetate) have been studied by EPR spectroscopy in the X-, Q- and W-bands. Polynuclear copper(II) complexes are formed by binuclear fragments bonded by bridging carboxylate anions. In compounds 1 – 3 , only pairwise interactions between copper ions are observed, despite the fact that in 2 and 3 there may be additional interactions between copper ions belonging to different dimers. [ABSTRACT FROM AUTHOR]

The phase behavior of the melt of the symmetric V-shaped molecules has been inspected within the Landau–de Gennes approach. The arms of V-shaped molecule are modeled by rod-like segments connected at an external angle α ; these segments are assumed to be composed of monomer units. The phase diagram of the system contains regions of stability of the isotropic, homogeneous nematic, and modulated nematic phases: nematic twist bend (N TB ) phase that is characterized by the three directors which move on a helix and one of these directors forms a fixed nonzero cone angle with the helix axis, and the N0 modulated phase in which one director is parallel to the helix axis while two others are orthogonal to the helix axis. The characteristic periods of modulated structures were found to be of order a few molecular lengths. [ABSTRACT FROM AUTHOR]

The reaction of two structurally related bridging ligands bis[5-(2-pyridyl)-1,2,4-triazole-3-yl]methane (H2L1) and bis[5-(2-pyridyl)-1,2,4-triazole-3-yl]ethane (H2L2) with copper(ii) salts resulted in a surprising wide variety of complex structures [Cu2(H2L1)Cl2]Cl2·4CH3OH (1), [Cu4(L1)4]·4H2O (2), [Cu(H2L2)(ClO4)2] (3) and [Cu3(OH)Na2(L′)6](ClO4)·5H2O·C3H6O (4), where HL′ is 3,5-bis-(pyridin-2-yl)-1,2,4-triazole, which were structurally characterized by the X-ray diffraction method. Complexes 1 and 2 were prepared on the H2L1 basis and have binuclear and tetranuclear structures, respectively, demonstrating strong impact of the type of counter anion on the coordination mode of the ligand. In contrast, the reaction between Cu(ClO4)2 6H2O and H2L2 led to the preparation of mononuclear complex 3. The reaction of H2L2 with Cu(ClO4)2 under alkaline conditions led to oxidative rearrangement of the ligand and the homoleptic pentanuclear complex 4 with anionic ligand L′ was prepared. Magnetic properties were studied for compounds 1, 2 and 4 and for all of them the antiferromagnetic interactions between the Cu atoms were confirmed and analyzed by the spin Hamiltonian formalism. Furthermore, the occurrence of the antisymmetric exchange was confirmed in 4. The magnetic data analysis was supported by the X-band EPR measurements performed for complexes 1, 2 and 4. [ABSTRACT FROM AUTHOR]

Compounds containing bis‐chelate dianionic blocks {M(3d)(cbdc)2}2– (M(3d)=VIVO, CuII) with cations VO2+ and Cu2+ chelated by two anions of dicarboxylic acid have been prepared as crystals when aqueous solutions of vanadyl sulfate VOSO4⋅3H2O or copper sulfate CuSO4⋅5H2O have been allowed to react with sulfates of d‐metals (MnII, CoII, NiII, ZnII, and CdII) and barium salt of cyclobutane‐1,1‐dicarboxylic acid (H2cbdc=C4H6(CO2H)2) in the 1:1:2 ratio. The nature of the M(3d) metal center has been found to influence on the structure of the heterometallic compounds formed. 1D polymers [M(VO)(cbdc)2(EtOH)2(H2O)3]n (M=Mn (1), Co (2), Ni (3)), molecular dinuclear complex [Zn(VO)(cbdc)2(H2O)5]⋅H2O (4), and 1D polymer {[Cd(VO)(cbdc)2(H2O)5]⋅H2O}n (5) are formed when M(3d)=VIVO, whereas in the case of the bis‐chelate block with the CuII atom, ionic compounds [M(H2O)6][Cu(cbdc)2(H2O)] (M=Mn (6), Co (7), Ni (8), Zn (9)) and 2D polymer {[CdCu(cbdc)2(H2O)2]⋅2H2O}n have been synthesized. The isolation of paramagnetic centers in compounds 1–10 is confirmed by magnetic measurements and EPR spectroscopy. The structure of M(3d)‐M heterometallic compounds (M(3d)=VO2+, Cu2+; M=Mn2+, Co2+, Ni2+, Zn2+, Cd2+) with cyclobutane‐1,1‐dicarboxylic acid anions is influenced not only by the nature of the heterometal M at the same M(3d) but also the nature of this M(3d) center, which forms a bis‐chelate block with two anions of substituted malonic acid. [ABSTRACT FROM AUTHOR]

The reaction of VOSO4 with K2cbdc (cbdc2– is cyclobutane‐1,1‐dicarboxylate anion) and Ln(NO3)3 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Tm, Yb, Lu) yielded 17 novel heterometallic LnIII‐VIV compounds comprising stable bis‐chelate units {VIVO(cbdc)2(H2O)}. Three structural types of compounds are formed depending on the nature of the rare‐earth metal: 1D polymers {[Ln(VO)(cbdc)2(H2O)7]·0.5[VO(cbdc)2]}n (structural type I) [Ln = La (1), Ce (2)], 3D polymers {[KLn(VO)2(cbdc)4(H2O)9]·3.5H2O}n (structural type II) [Ln = La (3), Ce (4), Pr (5), Nd (6), Sm (7), Eu (8), Gd (9), Tb (10), Dy (11), Ho (12)] comprising trinuclear units {LnV2}, and octanuclear complexes {[KLn(VO)2(cbdc)4(H2O)11]·2H2O}2 (structural type III) [Ln = Y (13), Er (14), Tm (15), Yb (16), Lu (17)] containing dinuclear units {LnV}. Magnetic properties were investigated for all isolated compounds. The GdIII‐VIV compound has ferromagnetic and antiferromagnetic exchange interactions between isotropic VIV and GdIII ions. Calculations using the DFT method at the UB3LYP/6‐31G(d,p)/SDD level of theory were performed in order to explain the different nature of exchange interactions in two GdIII‐VIV pairs. The YbIII‐VIV complex displays single‐molecule magnet properties; the effective energy barrier was estimated at ΔEeff/kB = 26 K. The magnetic properties of LnIII‐VIV compounds with heavy lanthanide ions (LnIII = Er, Tm, Yb) were rationalized in terms of crystal‐field calculations for LnIII ions. Three structural types of heterometallic LnIII‐VIV substituted malonates were synthesized from the bis‐malonate vanadyl unit and were characterized by single‐crystal and powder XRD and by magnetic measurements. The structures of the new compounds depend on the nature of the rare‐earth metal: a decrease in the LnIII ionic radius is accompanied by a decrease in the nuclearity of the {LnIII‐VIV} unit. [ABSTRACT FROM AUTHOR]

Mononuclear {Cu(Me2mal)2}2- dianion has been used as a building block for the synthesis of six new coordination polymers: {Li2(H2O)2(µ-H2O)[Cu(µ4-Me2mal)(µ-Me2mal)]} n ( 1), {Na2(µ-EtOH)2[Cu(µ5-Me2mal)2]} n ( 2), {K8(µ-H2O)6[Cu(µ-H2O)(µ3-Me2mal)(µ6-Me2mal)]2[Cu2(µ5-Me2mal)4]} n ( 3), {K2M(H2O)5(µ-H2O)3[Cu(µ-Me2mal)(µ3-Me2mal)][Cu(µ-H2O)(µ-Me2mal)(µ3-Me2mal)]} n (M = MgII ( 4) or NiII ( 5); isostructural compounds), and {K4Co3(H2O)8(µ-H2O)4(µ3-OH)2[Cu(H2O)(µ-Me2mal)(µ3-Me2mal)]2[Cu(µ-H2O)(µ3-Me2mal)2]2} n ( 6). It was shown that the structures of the compounds depend on the nature and ionic radius of the heterometal. In particular, the dimensionality of the complexes increases from 1D to 2D and 3D with increasing radius of the s-metal in compounds 1, 2, and 3, respectively. Partial replacement of K+ in 3 by Mg2+, Ni2+, or Co2+ leads to the formation of heterometallic coordination polymers 4 and 5, with 2D structure, and 3D complex 6. The compounds were characterized by single-crystal X-ray diffraction and EPR spectroscopy, and the magnetic properties of compounds 1, 2, and 4- 6 were also studied. Further, the topological analysis of the structures and another 794 known mal-derivatives complexes from Cambridge Structural Database (CSD, version 5.36) was performed. The main regularities determining the coordination modes of ligands and metal cations in relation to structure topology have been established and are discussed. [ABSTRACT FROM AUTHOR]

A series of new manganese(ii) pivalate–phosphonate complexes with various nuclearities (Mn4, Mn10, and Mn20) under aerobic conditions was synthesized by self-assembly of simple reagents. The constitution of polynuclear architectures is affected by the reaction temperature. The structures of the complexes were determined by single crystal X-ray analysis. Magnetic behavior of the compounds points to dominant antiferromagnetic exchange interactions. Antiferromagnetic coupling with JMn–Mn = −0.097(1) cm−1, gMn = 1.993(1) for an equilateral tetrahedron model simulates the magnetic behavior of the tetranuclear complex Mn4 with a cube-like core. [ABSTRACT FROM AUTHOR]

Trinuclear copper(II) complex [Cu II 3 (bipy) 6 (μ 3 -CO 3 )][B 12 H 12 ] 2 ·4.5DMF·2H 2 O is isolated as a result of the redox reaction proceeding when [Ag I 2 B 12 H 12 ] was allowed to react with Cu I Cl in the presence of bipy. Crystal structure, magnetic properties, and EPR spectrum of the compound are studied. It has been found that in the range 300–2 K, magnetic moment decreases from 1.98 to 1.33 µ B with decreasing the temperature. In the EPR spectrum, the transition ΔM = ±3 transition is observed indicating the existence of the S  = 3/2 state. This transition is explained by the effect of fine coupling tensor which admixes the |−1/〉 state into the |3/2〉 state and the |1/2〉 state into the |−3/2〉 state. The EPR spectrum is simulated by the spin Hamiltonians for S  = 3/2 and S  = 1/2. [ABSTRACT FROM AUTHOR]

The complexation of copper and 1,10-phenanthroline ( phen ) in the presence of the [B 12 H 12 ] 2− anion is studied in organic solvents. The starting reagents contain copper(I) salts. The reactions are carried out in air and accompanied with oxidation of copper(I). Varying solvents and starting reagents, we succeeded in synthesizing selectively copper(I), copper(II), and heterovalent copper(I,II) complexes. Mononuclear, tetranuclear, and polymeric copper(II) complexes as well as a mononuclear copper(I) complex and a mixed cationic mononuclear copper(I)/copper(II) complexes are isolated and characterized by IR-spectroscopy and X-ray diffraction. The electronic structure of mononuclear copper(II) complex [Cu II ( phen ) 2 Cl] 2 [B 12 H 12 ] 2CH 2 I 2 is studied by EPR. [ABSTRACT FROM AUTHOR]