Intermolecular interaction and magnetic coupling mechanism on a mononuclear CoII complex

Anti-ferromagnetic interaction was observed in a new crystal that consists of mononuclear Co^II complexes, namely [Co(PMP)(N₃)] (PMP?=?2,9-bis(pyridin-2-methoxyl)-1,10-phenanthroline); in the mononuclear complex Co^II has a distorted trigonal-bipyramidal geometry. Analysis for the crystal structure indicates six magnetic coupling pathways among adjacent complexes, in which three involve π–π stacking and the other three deal with intermolecular interactions. The fitting for the variable-temperature magnetic susceptibilities with the Curie–Weiss formula shows an anti-ferromagnetic interaction between adjacent Co^II ions with θ?=??5.49 K?=??3.82?cm^?1. Theoretical calculations on the spin section reveal that the three π–π stacking systems result in magnetic coupling constants 2J?=??0.10?cm^?1, ?0.10?cm^?1, and 1.24?cm^?1, respectively, and the three intermolecular interactions lead to weak anti-ferromagnetic interactions with 2J?=??0.36?cm^?1, ?0.26?cm^?1, and ?0.32?cm^?1, respectively. The theoretical calculations and the experimental magnetic data imply that the anti-ferromagnetic interaction involves the orbital contribution of the relevant Co^II ions.     

Intermolecular interaction and magnetic coupling mechanism of a 2-D mixed-valence CuIICuI coordination polymer containing μ 1,1,3-SCN bridge

A 2-D Cu^ICu^II mixed oxidation state coordination polymer, [Cu^IICu^I(μ _1,3-SCN)₂(μ _1,1,3-SCN)(PhenE)] _n (PhenE: 2-ethoxy-1,10-phenanthroline), has been prepared and its crystal structure determined by X-ray crystallography. In the polymer, Cu^II is a distorted trigonal bipyramidal geometry and Cu^I has distorted tetrahedral coordination. Thiocyanate bridges in two modes, μ _1,3-SCN and μ _1,1,3-SCN, resulting in a 2-D coordination sheet. The crystal structure analysis shows that there is a splipped π–π stacking in the sheet. The fitting for the variable-temperature magnetic susceptibility data gave the magnetic coupling constant 2J?=??2.72?cm^?1 and zJ′?=??2.07?cm^?1. The magnetic interaction may be mainly ascribed to intermolecular π–π magnetic coupling.     

Intramolecular and Intermolecular Magnetic Coupling Mechanism of a Dinuclear Copper(II) Complex

Abstract. A new dinuclear complex, [Cu₂(μ_{1, 3}‐NCS)₂(Ophen)₂(OH₂)₂], (HOphen = 1, 10‐phenanthrolin‐2‐ol) was synthesized and its crystal structure was determined by X‐ray crystallography. In the complex, the Cu^II ion assumes a distorted square pyramidal arrangement and the thiocyanate anion functions as bridged ligand and Ophen as capped ligand. The analysis of the crystal structure shows that there exists a π–π stacking interaction between the adjacent complexes. The theoretical calculations reveal that the magnetic coupling pathways from the thiocyanate anions bridge ligand and the π–π stacking magnetic coupling pathway resulted in the weak ferromagnetic interactions with 2J = 18.46 cm^–1 and 2J = 10.46 cm^–1, respectively. The calculations also display that the spin delocalization and the spin polarization occur in the bridge magnetic coupling system and the π–π stacking magnetic coupling system, and the magnetic coupling mechanism of the π–π stacking can be explained with McConnell I spin‐polarization mechanism. The fitting for the data of the variable‐temperature magnetic susceptibility with dinuclear Cu^II formula gave the magnetic coupling constant 2J = 2.84 cm^–1 and zJ′ = 0.03 cm^–1, in which the 2J = 2.84 cm^–1 is attributed to the magnetic coupling from the bridge dinuclear Cu^II unit and the zJ′ = 0.03 cm^–1 is ascribed to the π–π stacking magnetic coupling system. The study may benefit to understand the magnetic coupling mechanism of π–π stacking system.     

Synthesis,crystal structure and magnetic property of a one-dimensional copper(II) complex with 2,5-dimethylpyrazine-1,4-dioxide as bridging ligand

A one-dimensional polynuclear copper(II) complex [Cu(μ_1,6-dmpzdo)(SCN)₂] _n (where dmpzdo?=?2,5-dimethylpyrazine-1,4-dioxide) has been synthesized and its crystal structure determined by X-ray crystallography. The coordination geometry of Cu(II) atom is a square plane and each Cu(II) ion is connected by two μ_1,6-dmpzdo bridging ligands, leading to the formation of a one-dimensional chain. ESR spectra indicate magnetic coupling between the bridged Cu(II) ions. The fitting of the variable-temperature magnetic susceptibility data (4–300?K) gave 2J?=??68.69?cm^?1.     

Synthesis,structure, and properties of a 1-D copper(II) complex with nitronyl nitroxide radicals

A 1-D chain complex [Cu(NIT4Py)(IDA)]_∞ (NIT4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and IDA = iminodiacetate) has been prepared and characterized by single-crystal X-ray diffraction, IR, TGA, and magnetic analysis. Each Cu(II) is five-coordinate with distorted square pyramidal geometry. Each IDA bridges two Cu(II) ions via one carboxylate which occupies the axial site of Cu(II), leading to a chain structure composed of Cu(II)-radical cations and IDA anions. In the complex, there exist three magnetic exchange pathways, (i) interaction between units of (Cu(II)-NIT4Py) through IDA, (ii) Cu(II)-NIT4Py interaction, and (iii) NIT4Py-NIT4Py interaction through space. Compared with the first two magnetic interactions, the last magnetic exchange interaction should be too weak to be counted because of the large distance of the neighboring NIT4Py molecules (4.993 Å). Analysis of the magnetic properties was performed using the Bleany–Bowers (dimer) model, showing that the complex exhibited both weak antiferromagnetic interaction between the Cu(II) and NIT4Py, and between the units of (Cu(II)-NIT4Py) through IDA with exchange coupling parameters J = ?7.28 cm^?1 and zJ′ = ?0.40 cm^?1.     

A novel three-dimensional mixed bridging–ligand complex with an unexpected 1,3-diaminopropane bridge

Reaction of K₃[Fe(CN)₆] with [Cu(tn)₂](ClO₄)₂ (tn=1,3-diaminopropane) leads to a novel mixed cyano and tn bridged three-dimensional (3D) bimetallic assembly (1), in which each [Fe(CN)₆]⁴⁻ anion connects six copper(II) cations via six CN⁻ groups, whereas each copper(II) cation is linked to three [Fe(CN)₆]⁴⁻ ions and two other copper(II) ions through Cu–NC–Fe and Cu–tn–Cu linkages, respectively. Magnetic studies reveal weak antiferromagnetic interactions between the nearest Cu^II (S=1/2) ions through the diamagnetic [Fe(CN)₆]⁴⁻ anion.     

Configurational stabilization of mixed-valence states in the star-burst tetranuclear ruthenium complex bridged with acetylene links

A new tetranuclear ruthenium complex in which a metal was bridged radially to three identical metals with acetylene links showed a mixed-valence state in cyclic voltammograms. The peak potential difference for the mixed-valence state was twice the potential difference for a mixed-valence state of the corresponding binuclear complex. This fact suggests stabilization of the mixed-valence state twice by configurational modification of redox centers. However, this is inconsistent with the prediction from the additive pair model of the redox interaction. A quantum chemical model of the redox interaction was presented, in which the potential difference was expressed by the overlap integral S and the nearest neighbor interaction energy between the reduced center and the oxidized one. Application of the theory gave a negative value of S, which demonstrated reasonably the stabilization of the mixed-valence state from a quantum chemical viewpoint.     

A new double asymmetric μ 1,1-azido bridged binuclear copper(II) complex: crystal structure and magnetic properties

A new double asymmetric μ_1,1-azido bridged binuclear copper(II) complex, [Cu₂(μ_1,1-N₃)₂(Him2-py)₂(N₃)₂] (Him2-py?=?2-(2′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-hydroxy), has been synthesized and characterized structurally and magnetically. The crystal structure shows this complex is binuclear with copper(II) in a distorted square-pyramidal geometry, bridged by double asymmetric end-on azide ligands. The variable temperature magnetic susceptibility analyses reveal weak antiferromagnetic interaction mediated by the bridge.     

Synthesis,crystal structure and magnetic properties of a new macrocyclic trinuclear CuII-CuII-CuII complex

A new oxamido-bridged trinuclear copper(II) complex [(CuL)₂Cu](ClO₄)₂·0.5H₂O (L?=?the dianion of 2,3-dioxo-5,6,14,15-dibenzo-7,13-bis(ethoxycarbonyl)-1,4,8,12-tetraazacyclotetradeca-7,12-diene) has been synthesized by self-assembly and characterized. X-ray diffraction analysis reveals that the title complex is monoclinic, space group P2₁, with a?=?16.213(5), b?=?9.811(3), c?=?18.802(6)?Å, β?=?96.790(5)°. The central copper(II) ion lies in a distorted octahedral environment. Terminal coppers have square pyramidal coordination geometry. Magnetic measurements show there is strong antiferromagnetic interaction between the central and the terminal Cu(II) ions.     

Synthesis,crystal structure,and magnetic properties of an octacyanometallate-based Ni/Mo bimetallic complex with the diamond topological network

Reaction of [NiL]²⁺ (L = 3,10-diethyl-1,3,5,8,10,12-hexaazacyclotetradecane) with [Mo(CN)₈]^4? leads to a new Ni₂Mo complex [Ni(L)]₂[Mo(CN)₈] · 8H₂O (1), which displays a 3-D diamond topological network. Magnetic study indicates a combination of zero-field splitting of Ni²⁺ in an axially distorted octahedral coordination and weak antiferromagnetic interactions between Ni²⁺ centers through diamagnetic [Mo(CN)₈]^4? bridges.     

Crystal structure,thermal and magnetic studies of a dinuclear Mn(II) complex with decadentate picolinate based ligand

The reaction of the decadentate ligand tpmen (H₄tpmen?=?N,N,N′N′-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylenediamine) with MnCl₂·4H₂O in aqueous solution gives a homodinuclear complex [Mn₂(H₂O)₂(tpmen)]·16H₂O, which has been characterized by elemental analysis, thermal gravimetric and single-crystal X-ray diffraction analysis. The complex crystallizes in the orthorhombic system, space group Cmca, a?=?28.786(5) Å, b?=?11.5033(19) Å, c?=?14.437(2) Å, Z?=?8, R ₁?=?0.0432, wR ₂?=?0.0786. The tpmen ligand contains four picolinate groups, two of which bind each Mn(II) to form a dinuclear complex. The geometry around the Mn(II) is distorted octahedral with two nitrogen and two oxygen atoms from the picolinate groups and two oxygen atoms from coordinated water. The variable-temperature (2–300?K) magnetic susceptibilities shows an antiferromagnetic interaction between Mn(II) ions.     

Crystal structure,and thermal and magnetic properties of 2,4-dinitrobenzoatoterbium(III) complex

The Tb(III) complex containing 2,4-dinitrobenzoate (2,4-DNB), Tb(2,4-DNB)₃(H₂O)₂]?·?C₂H₅OH has been synthesized and its crystal structure analyzed by X-ray diffraction methods. The complex crystallizes in the triclinic space group P 1, as a linear polymeric chain in which terbium ions are bridged by carboxylate groups. The eight-coordinate Tb ion with six carboxylate groups and two water molecules forms a slightly distorted square antiprism. Thermal and magnetic properties of the terbium complex were also studied.     

Synthesis,crystal structure,and magnetic properties of a linear trinuclear Cu(II) complex

A new linear trinuclear Cu(II) complex, [Cu₃(NTA)₂(4,4′-bpt)₄(H₂O)₂]?·?10H₂O (H₃NTA?=?nitrilotriacetic acid, 4,4′-bpt?=?4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole) (1), was obtained from evaporation of an aqueous solution containing Cu(NO₃)₂?·?6H₂O, 4,4′-bpt, nitrilotriacetic acid (H₃NTA), and NaOH. 1 was characterized using single-crystal X-ray diffraction, IR, and elemental analysis. In the trimer, the three linear copper ions are bridged by two NTA carboxylate groups in a syn–anti conformation and connected by 4,4′-bpt to produce a 1-D array. Temperature-dependent magnetic susceptibilities reveal the presence of weak antiferromagnetic exchange between metal centers.     

A one-dimensional azido-bridged manganese(III) complex with bidentate Schiff base: Crystal structure and magnetic properties

The synthesis, structural characterization, and magnetic behavior of a novel one-dimensional azido-bridged manganese(III) complex of formula [Mn(L)₂N₃] (1) is reported, where HL is the bidentate Schiff base obtained from the condensation of salicylaldehyde with 4-methoxy aniline. Complex 1 crystallizes in the monoclinic system, space group P2₁/n, with a=11.743(4) Å, b=24.986(9) Å, c=13.081(5) Å, β=95.387(7)° and Z=2. The complex is of one-dimensional chain structure with single end-to-end azido bridges and the manganese(III) ion has an elongated octahedral geometry. Magnetic studies show that the weak antiferromagnetic interaction is mediated by the single end-to-end azido bridge with the exchange parameter J=−5.84 cm⁻¹.     

Synthesis,crystal structure,and magnetic properties of a new Fe(II) complex with reduced radical ligands

A new Fe(II) complex, [Fe(HIM2Py)₂(N(CN)₂)₂]?·?2H₂O (HIM2py?=?1-hydroxyl-2(2′-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1?H-imidazole), has been synthesized and characterized. The X-ray analysis reveals that HIM2py ligands are coordinated to iron as an unusual six-membered bidentate chelate with κ²N(py), O(HIM) mode. The variable-temperature magnetic susceptibility suggests that weak antiferromagnetic interactions exist in the complex.