Synthesis, Crystal Structures and Magnetic Properties of Trinuclear {Ni2Ln} (LnIII = Dy, Ho) and {Ni2Y} Complexes with Schiff Base Ligands

The reaction of the Schiff base ligand o-OH-C6H4-CH=N-C(CH2OH)3, H4L, with Ni(O2CMe)2∙4H2O and lanthanide nitrate salts in a 4:2:1 ratio lead to the formation of the trinuclear complexes [Ni2Ln(H3L)4(O2CMe)2](NO3) (Ln = Dy (1), Ho (2), and Y (3)) which crystallize in the non-centrosymmetric space group Pna21. The complex cation consists of the three metal ions in an almost linear arrangement. The {Ni2Ln} moieties are bridged through two deprotonated Ophenolato groups from two different ligands. Each terminal NiII ion is bound to two ligands through their Ophenolato, the Nimino atoms and one of the protonated Oalkoxo groups in a distorted octahedral. The central lanthanide ion is coordinated to four Ophenolato oxygen from the four ligands, and four Ocarboxylato atoms from two acetates which are bound in the bidentate chelate mode, and the coordination polyhedron is biaugmented trigonal prism, which probably results in a non-centrosymmetric arrangement of the complexes in the lattice. The magnetic properties of 1–3 were studied and showed that 1 exhibits field induced slow magnetic relaxation.

Synthesis and structural analysis of cis-bis(1,10-phenanthroline)dicarbonyl ruthenium(II) 1.72-trifluoromethanesulfonate 0.28-hexafluoridophosphate

Ruthenium(II) complexes containing both 1,10-phenanthroline (Phen) and carbonyl (CO) ligands are important molecules for various applications including catalysis. In this work, the molecular structure of [Ru(Phen)2(CO)2]2+ was determined via X-ray diffraction analysis for the first time. The complex exhibits substitutional disorder of one of counter-anions in the asymmetric unit, with different occupancies for CF3SO3- (0.72) and PF6- (0.28). The ruthenium atom is coordinated in a distorted octahedral environment by two carbonyl carbon atoms and four nitrogen atoms from bis-Phen ligands. The cation displays a cis configuration of the carbonyl ligands. Several hydrogen bonds and π-π interactions are present in the crystal. In addition to structural characterization, IR spectral data for the complex is compared with calculated values. These results provide fundamental data for understanding various properties of related ruthenium complexes.

Enhancement of superexchange due to synergetic breathing and hopping in corner-sharing cuprates

Cuprates with corner-sharing CuO4 plaquettes have received much attention owing to the discoveries of high-temperature superconductivity and exotic states where spin and charge or spin and orbital degrees of freedom are separated. In these systems spins are strongly coupled antiferromagnetically via superexchange mechanisms, with high nearest-neighbour coupling varying among different compounds. The electronic properties of cuprates are also known to be highly sensitive to the presence, distance and displacement of apical oxygens perpendicular to the CuO2 planes. Here we present ab initio quantum chemistry calculations of the nearest-neighbour superexchange antiferromagnetic (AF) coupling J of two cuprates, Sr2CuO3 and La2CuO4. The former lacks apical oxygens, whilst the latter contain two apical oxygens per CuO2 unit completing a distorted octahedral environment around each Cu atom. Good agreement is obtained with experimental estimates for both systems. Analysis of the correlated wavefunctions together with extended superexchange models shows that there is an important synergetic effect of the Coulomb interaction and the O–Cu hopping, namely a correlated breathing-enhanced hopping mechanism. This is a new ingredient in superexchange models. Suppression of this mechanism leads to drastic reduction in the AF coupling, indicating that it is of primary importance in generating the strong interactions. We also find that J increases substantially as the distance between Cu and apical O is increased.

One Pot Ultrasonic Assisted {[Ni(tptz)Cl(H2O)2][Ni(tptz)(H2O)3]}-3Cl.5H2O Complex Formation Using Triazine Ligand, XRD/HSA-Interactions, and Spectral and Thermal Investigation

Under room temperature ultrasonic conditions, mixing the neutral 2,4,6-tri(pyridin-2-yl)-1,3,5-triazine (tptz) ligand with Ni(II) salt resulted in the preparation of a unique {[Ni(tptz)Cl(H2O)2]-[Ni(tptz)(H2O)3]}3Cl.5H2O complex with two different nickel(II) centers in a high yield. The crystal structure of {[Ni(tptz)Cl(H2O)2][Ni(tptz)(H2O)3]}3Cl.5H2O revealed the existence of distorted octahedral around both Ni(II) centers. The complex structure was further supported by FT-IR, UV-Vis., CHN-EA, TGA and EDX. The computed HSA was also performed to support the XRD interaction types. The existence of the H2O molecules in the crystal lattice was examined by FT-IR and TG/DTG measurements that proved the presence of coordinated and uncoordinated water molecules. Moreover, the thermal stability of the desired complex was evaluated at open atmosphere via TG/DTG and showed stability up to ~400 °C and multistep thermal decomposition.

The structures of 1:1 and 1:2 adducts of phosphanetricarbonitrile with 1,4-diazabicyclo[2.2.2]octane

In the structures of 1:1 and 1:2 adducts of phosphanetricarbonitrile (C3N3P) with 1,4-diazabicyclo[2.2.2]octane (C6H12N2), the 1:1 adduct crystallizes in the orthorhombic space group, Pbcm, with four formula units in the unit cell (Z′ = 0.5). The P(CN)3 unit lies on a crystallographic mirror plane while the C6H12N2 unit lies on a crystallographic twofold axis passing through one of the C—C bonds. The P(CN)3 moiety has close to C 3v symmetry and is stabilized by forming adducts with two symmetry-related C6H12N2 units. The phosphorus atom is in a five-coordinate environment. As a result of the symmetry, the two trans angles are equal so τ5 = 0.00 and thus the geometrical description could be considered to be square pyramidal. However, the electronic geometry is distorted octahedral with the lone pair on the phosphorous occupying the sixth position. As would be expected from VSEPR considerations, the repulsion of the lone-pair electrons with the equatorial bonding electrons means that the trans angles for the latter are considerably reduced from 180° to 162.01 (4)°, so the best description of the overall geometry for phosphorus is distorted square pyramidal. The 1:2 adduct crystallizes in the monoclinic space group, P21/m with two formula units in the asymmetric unit (i.e. Z' = 1/2). The P(CN)3 moiety lies on a mirror plane and one of the two C6H12N2 (dabco) molecules also lies on a mirror plane. The symmetry of the P(CN)3 unit is close to C 3v. There are three P...N interactions and consequently the molecular geometry of the phosphorus atom is distorted octahedral. This must mean that the lone pair of electrons on the phosphorus atom is not sterically active. For the 1:1 adduct, there are weak associations between the phosphorus atom and one of the terminal nitrogen atoms from the C[triple-bond] N moiety, forming chains in the a-axis direction. In addition there are weak C—H...N interactions between a terminal nitrogen atoms from the C[triple-bond]N moiety and the C6H12N2 molecules, which form sheets perpendicular to the a axis.

Tris[triphenylantimony(V)]hexa(μ-oxido)tellurium(VI): a molecular complex with six Te—O—Sb bridges

In the structure of the title compound [systematic name hexa-μ-oxido-1:2κ4 O:O;1:3κ4 O:O;1:4κ4 O:O-nonaphenyl-2κ3 C,3κ3 C,4κ3 C-triantimony(V)tellurium(VI)], [Sb3Te(C6H5)9O6], the hexaoxidotellurate(VI) ion is coordinated to three SbV ions via pairs of cis-positioned O atoms to form a discrete molecular unit. The TeVI and SbV central ions exhibit distorted octahedral [TeO6] and distorted trigonal–bipyramidal [SbC3O2] coordination geometries, respectively. The linking of these polyhedra, by sharing the dioxide edges, results in the Te-based octahedron having a mer-configuration. The packing of the molecules is dominated by C—H...O hydrogen bonding and weak dispersion forces, with a minor contribution from C—H...π bonds and π–π stacking interactions. According to the Hirshfeld surface analysis, the contributions of the H...H, H...C/C...H and H...O/O...H contacts are 58.0, 32.6 and 7.8%, respectively. The title structure provides a model for the bonding of triorganoantimony dications to octahedral oxoanions, and the observed doubly bridged motifs, Te(μ-O)2Sb, may find application in the functionalization of polyoxometalate species.

Crystal structure, Hirshfeld surface analysis and DFT studies of tetrakis(μ-3-nitrobenzoato-κ2 O 1:O 1′)bis[(N,N-dimethylformamide-κO)copper(II)] dimethylformamide disolvate

The title compound, [Cu2(C7H4NO4)4(C3H7NO)2]·(C3H7NO)2, is a binuclear copper(II) complex located on an inversion center midway between the two copper(II) cations. The asymmetric unit consists of one CuII cation, two 3-nitrobenzoato ligands, and two dimethylformamide (DMF) molecules, one of which coordinates to the CuII cation and one is a solvate molecule. The carboxylate groups of the ligands bridge two CuII cations with a Cu—Cu distance of 2.6554 (6) Å, completing a distorted octahedral O5Cu coordination environment. The dihedral angles between the carboxylate and the aromatic ring planes of the two independent ligands are different from one another, viz. 5.2 (3) and 23.9 (3)°. The three-dimensional structure is consolidated by weak C—H...O interactions and stabilized by π–π stacking interactions between the aromatic rings. The complex and the free ligand were further characterized by Fourier-transform infrared spectroscopy (FT–IR), and the energies of the frontier molecular orbitals of the complex were determined by DFT calculations at the B3LYP/def2-TZVP level of theory.

Crystal structure and Hirshfeld surface analysis of di-μ-chlorido-bis[(acetonitrile-κN)chlorido(ethyl 5-methyl-1H-pyrazole-3-carboxylate-κ2 N 2,O)copper(II)]

The title compound, [Cu2Cl4(C5H10N2O2)2(CH3CN)2] or [Cu2(μ2-Cl)2(CH3—Pz-COOCH2CH3)2Cl2(CH3CN)2], was synthesized using a one-pot reaction of copper powder, copper(II) chloride dihydrate and ethyl 5-methyl-1H-pyrazole-3-carboxylate (CH3—Pz-COOCH2CH3) in acetonitrile under ambient conditions. This complex consists of discrete binuclear molecules with a {Cu2(μ2-Cl)2} core, in which the Cu...Cu distance is 3.8002 (7) Å. The pyrazole-based ligands are bidentate coordinated, leading to the formation of two five-membered chelate rings. The coordination geometry of both copper atoms (ON2Cl3) can be described as distorted octahedral on account of the acetonitrile coordination. A Hirshfeld surface analysis suggests that the most important contributions to the surface contacts are from H...H (40%), H...Cl/Cl...H (24.3%), H...O/O...H (11.8%), H...C/C...H (9.2%) and H...N/N...H (8.3%) interactions.

Synthesis and crystal structure of a new chiral α-aminooxime nickel(II) complex

A dinuclear nickel complex with (S)-limonene based aminooxime ligand has been isolated and its crystal structure determined. The resolved structure of dichloridobis{(2S,5R)-2-methyl-5-(prop-1-en-2-yl)-2-[(pyridin-2-yl)methylamino]cyclohexan-1-one oxime}dinickel(II), [Ni2Cl2(C16H23ClN3O)2], at 100 K has monoclinic (P21) symmetry. The two NiII ions in the dinuclear complex are each coordinated in a distorted octahedral environment by three nitrogen atoms, a terminal chloride and two μ bridging chlorides. Each oxime ligand is coordinated to nickel(II) by the three nitrogen atoms, leading to two five-membered chelate rings, each displaying an envelope conformation. In the crystal, numerous intermolecular and intramolecular hydrogen bonds lead to the formation of a three-dimensional network structure.