A Mononuclear and a Mixed-Valence Chain Polymer Arising from Copper(II) Halide Chemistry and the Use of 2,2′-Pyridil

Reactions of 2,2′-pyridil (pyCOCOpy) with CuCl2 · 2H2O and CuBr2 in EtOH yielded the mononuclear complex [Cu(pyCOOEt)2Cl2] · H2O (1) and the one-dimensional, mixed-valence complex [Cu2ICuII(pyCOOEt)2Br4]n (2), respectively. Both complexes crystallize in the triclinic space group P 1¯. The lattice constants are a = 8.382(2), b = 9.778(2), c = 7.814(2), α = 101.17(1), β = 114.55(1), γ = 94.14(1)° for 1 and a = 8.738(1), b = 9.375(2), c = 7.966(1), α = 79.09(1), β = 64.25(1), γ = 81.78(1)° for 2. 2,2′-pyridil undergoes a metal-assisted alcoholysis and oxidation leading to decomposition and yielding the ethyl picolinate (pyCOOEt) ligand. The autoredox process associated with the reduction of copper(II) to copper(I) in the case of complex 2 is discussed in terms of the increased redox activity of the copper(II) bromide system relative to the copper(II) chloride system

A Mononuclear and a Mixed-Valence Chain Polymer Arising from Copper(II) Halide Chemistry and the Use of 2,2'-Pyridil

Reactions of 2, 2 -pyridil (pyCOCOpy) with (2) , respectively. Both complexes crystallize in the triclinic space group P 1. The lattice constants are a = 8.382(2), b = 9.778(2), c = 7.814(2), α = 101.17(1), β = 114.55(1), γ = 94.14(1) • for 1 and a = 8.738(1), b = 9.375(2), c = 7.966(1), α = 79.09(1), β = 64.25(1), γ = 81.7

Experimental Evidence of a Haldane Gap in an S = 2 Quasi-linear Chain Antiferromagnet

The magnetic susceptibility of the $S = 2$ quasi-linear chain Heisenberg antiferromagnet (2,$2'$-bipyridine)trichloromanganese(III), MnCl_{3}(bipy), has been measured from 1.8 to 300 K with the magnetic field, H, parallel and perpendicular to the chains. The analyzed data yield $g\approx 2$ and $J\approx 35$ K. The magnetization, M, has been studied at 30 mK and 1.4 K in H up to 16 T. No evidence of long-range order is observed. Depending on crystal orientation, $M\approx 0$ at 30 mK until a critical field is achieved ($H_{c\|} = 1.2\pm 0.2 T$ and $H_{c\bot} = 1.8\pm 0.2 T), where M increases continuously as H is increased. These results are interpreted as evidence of a Haldane gap.Comment: 11 pages, 4 figure

A general synthetic route for the preparation of high-spin molecules: Replacement of bridging hydroxo ligands in molecular clusters by end-on azido ligands

Abstract A general method of increasing the ground-state total spin value of a polynuclear 3d-metal complex is illustrated through selected examples from cobalt(II) and nickel(II) cluster chemistry that involves the dianion of the gem-diol form of di-2-pyridyl ketone and carboxylate ions as organic ligands. The approach is based on the replacement of hydroxo bridges, that most often propagate antiferromagnetic exchange interactions, by the end-on azido ligand, which is a ferromagnetic coupler

Families of Polynuclear Manganese, Cobalt, Nickel and Copper Complexes Stabilized by Various Forms of Di-2-pyridyl Ketone

The synthetic and structural chemistry of polynuclear manganese, cobalt, nickel and copper carboxylate complexes, stabilized by various forms of di-2-pyridyl ketone, is discussed. The structural diversity displayed by the described complexes stems from the ability of the doubly and singly deprotonated forms of the gem-diol form of di-2-pyridyl ketone, or the monoanion of the hemiacetal form of this ligand, to adopt a variety of coordination modes. The nuclearities of the clusters vary from four to fourteen. Perhaps the most aesthetically pleasing families are the “flywheel Cu-12 clusters, and the Co-9 and Ni-9 complexes in which the nine metal ions adopt a topology of two square pyramids sharing a common apex. A means of increasing the ground-state total spin value of a polynuclear 3d-metal cluster is also proposed. The approach is based on the replacement of hydroxo bridges, that most often propagate antiferromagnetic exchange interactions in clusters, by the end-on azido ligand, which is a well known ferromagnetic coupler. This approach involves “true” reactivity chemistry on pre-isolated clusters and the products are not undergone significant structural changes, except for the azido-for-hydroxo substitution, compared to the starting materials/clusters

Copper(I) and Copper(II) Halogeno Polymers with 2,1,3-benzothiazole: Variation of 1D and 2D Polymeric Structures as a Function of Reaction Conditions

The study of coordination polymers continues to be ofgreat interest in the context of their possibility to offer newfunctional materials with interesting magnetic, electrical oroptical properties. Much work has been done in theemployment of linear bidentate molecules as bridgingligands, because the dimensionality of the resultantpolymeric structures can be varied with the geometry ofmetal ion. Much less work has been carried out on the useof the non-linear bidentate bridging ligands; an interestingsuch ligand with a fixed bridging angle is 2,1,3-benzothiazole (btd). The present work describes theemployment of the non-chelating, bent potentially bridgingligand btd in the construction of copper(I) and copper(II)halogeno polymers. The complexes [CuCl2(btd)]n,[CuCl(btd)]n, [CuBr(btd)]n, [CuBr(btd)0.5]n, [CuI(btd)]n and[Cu2I2(btd)]n have been prepared and characterized bysingle-crystal and powder X-ray crystallography. Thecoordination polymers adopt 1D or 2D structuresdepending on the oxidation state of copper, thestoichiometry of the complexes, the nature of the anioniccoligand and the coordination (monodentate, bidentate) ofbtd. The magnetic properties of [CuCl2(btd)]n have alsobeen studied

Smart Ligands for Efficient 3d-, 4d- and 5d-Metal Single-Molecule Magnets and Single-Ion Magnets

There has been a renaissance in the interdisciplinary field of Molecular Magnetism since ~2000, due to the discovery of the impressive properties and potential applications of d- and f-metal Single-Molecule Magnets (SMMs) and Single-Ion Magnets (SIMs) or Monometallic Single-Molecule Magnets. One of the consequences of this discovery has been an explosive growth in synthetic molecular inorganic and organometallic chemistry. In SMM and SIM chemistry, inorganic and organic ligands play a decisive role, sometimes equally important to that of the magnetic metal ion(s). In SMM chemistry, bridging ligands that propagate strong ferromagnetic exchange interactions between the metal ions resulting in large spin ground states, well isolated from excited states, are preferable; however, antiferromagnetic coupling can also lead to SMM behavior. In SIM chemistry, ligands that create a strong axial crystal field are highly desirable for metal ions with oblate electron density, e.g., TbIII and DyIII, whereas equatorial crystal fields lead to SMM behavior in complexes based on metal ions with prolate electron density, e.g., ErIII. In this review, we have attempted to highlight the use of few, efficient ligands in the chemistry of transition-metal SMMs and SIMs, through selected examples. The content of the review is purely chemical and it is assumed that the reader has a good knowledge of synthetic, structural and physical inorganic chemistry, as well as of the properties of SIMs and SMMs and the techniques of their study. The ligands that will be discussed are the azide ion, the cyanido group, the tris(trimethylsilyl)methanide, the cyclopentanienido group, soft (based on the Hard-Soft Acid-Base model) ligands, metallacrowns combined with click chemistry, deprotonated aliphatic diols, and the family of 2-pyridyl ketoximes, including some of its elaborate derivatives. The rationale behind the selection of the ligands will be emphasized

Hydrogen bonded networks based on lanthanide(III) complexes of N,N ‘-dimethylurea (DMU): preparation, characterisation, and crystal structures of [Nd(DMU)(6)][NdCl6] and [Nd(NO3)(3)(DMU)(3)]

In order to examine the possibilities of using lanthanide(III) ions in the crystal engineering of hydrogen bonded coordination complexes, the compounds [Ln(DMU)(6)][LnCl(6)] and [Ln(NO3)(3)(DMU)(3)] (Ln = Pr, Nd, Gd, Er; DMU = N,N’-dimethylurea) have been prepared from the reactions of DMU with the appropriate lanthaniae(III) salts in alcohols. The representative complexes [Nd(DMU)(6)][NdCl6] (2) and [Nd(NO3)(3)(DMU)(3)] (6) have been structurally characterised by single-crystal X-ray studies. The structure of 2 consists of distorted octahedral [Nd(DMU)(6)](3+) and [NdCl6](3-) ions. In the molecules of 6, the Nd(III) ion is in a ninecoordinate, monocapped square antiprismatic geometry, surrounded by three O-bonded DMU ligands and three bidentate chelating nitrate groups. The [Nd(DMU)(6)](3+) cations and [NdCl6](3 -) anions self-assemble to form a hydrogen-bonded 3D architecture in 2. The hydrogen bonding functionalities on the molecules of 6 create also a 3D structure. Two main motifs of interionic/intermolecular hydrogen bonds have been observed: N-H... Cl in 2 and N-H... O(NO3-) in 6; weak C-H... Cl hydrogen bonding interactions are also present in 2. The complexes were characterised by magnetic susceptibilities at room temperature and spectroscopic (IR, far-IR, Raman) techniques. The vibrational data are discussed in terms of the nature of bonding and the known structures of the neodymium(III) complexes. (C) 2003 Elsevier Science Ltd. All rights reserved

Hydrogen bonded networks based on lanthanide(III) complexes of N,N’-dimethylurea (DMU): preparation, characterisation, and crystal structures of [Nd(DMU) 6][NdCl6

Abstract In order to examine the possibilities of using lanthanide (III) 3( anions self-assemble to form a hydrogen-bonded 3D architecture in 2. The hydrogen bonding functionalities on the molecules of 6 create also a 3D structure. Two main motifs of interionic/intermolecular hydrogen bonds have been observed: N Ã/HÁ Á ÁCl in 2 and N Ã/HÁ Á ÁO(NO 3 ( ) in 6; weak CÃ/HÁ Á ÁCl hydrogen bonding interactions are also present in 2. The complexes were characterised by magnetic susceptibilities at room temperature and spectroscopic (IR, far-IR, Raman) techniques. The vibrational data are discussed in terms of the nature of bonding and the known structures of the neodymium(III) complexes.

Di-2-pyridyl Ketone/Benzoate/Azide Combination as a Source of Copper(II) Clusters and Coordination Polymers: Dependence of the Product Identity on the Solvent

The reactions of di-2-pyridyl ketone with Cu(O2CPh)(2) in the presence of NaN3 and LiOH have led to an antiferromagnetically coupled (S = 0) Cu(II)6 cluster with a novel core and to (Cu-8(II))(n) and (Cu-2(II)), coordination polymers (the former 1D and the latter 2D) with interesting structures. The cluster or polymer formation depends on the reaction solvent