Azido Bridges Research Articles

Preparation, Crystal Structure, Thermal Decomposition, and Explosive Properties of [Cd(en)(N3)2]n

AbstractA new multi‐ligand coordination polymer of cadmium(II) ethylenediamine azide, [Cd(en)(N3)2]n (en=ethylenediamine), was synthesized and characterized by using elemental analysis and FT‐IR spectrum. Its crystal structure was determined by means of X‐ray single crystal diffraction. The obtained results show that this crystal belongs to monoclinic, P21/n space group, a=0.6548(1) nm, b=1.0170(2) nm, c=1.2246(2) nm, β=90.23(1)°, V=0.8156(2) nm3, Dc=2.090 g⋅cm−3, Z=4, R1=0.024, wR2 (I>2σ(I))=0.0416 and S=0.998. The Cd(II) ion is six‐coordinated with four azido ligands by μ‐1, 1 azido bridges, and two ethylenediamine molecules which serve as bidentate ligands through the nitrogen atoms. The thermal decomposition mechanism of the title complex was studied by using differential scanning calorimetry (DSC) and thermogravimetry‐differential thermogravimetry (TG–DTG) techniques. Under nitrogen atmosphere with a heating rate of 10 K⋅min−1, the thermal decomposition of the complex contains two main successive exothermic processes between 519 and 701 K in the DSC curve, and the final decomposed residue at 725 K is Cd. The non‐isothermal kinetics parameters were calculated by using the Kissinger's method, Ozawa–Doyle's method, pervasive integration method, and differential method, respectively. The sensitivity properties of [Cd(en)(N3)2]n were also determined with standard methods.

Structural and magnetic characterization of 1-D complexes constructed from pyrazole-3,5-dicarboxylate bridging multi copper(II) centers

In aqueous solution, the reaction of Cu(ClO4)2 and di(2-pyridylmethyl)amine, DPA with the disodium salt of pyrazole-3,5-dicarboxylate (Na2Hpzdc) in presence of sodium azide afforded the azido complex [Cu3(DPA)3(μ-pzdc)(μ-N3)](ClO4)2·2H2O (1) whereas when reaction was conducted in absence of sodium azide the perchlorato complex [Cu3(DPA)3(μ-pzdc)(μ-ClO4)](ClO4)2·3H2O (2) was obtained. The complexes were structurally characterized by physicochemical techniques and by single crystal X-ray crystallography in case of 1. The coordination sphere of the two complexes which are iso-structural polymeric 1D systems consist of three independent Cu(DPA) units, one pzdc bridging ligand and one end-on bridging azido group in 1 or one bridging perchlorato group in 2. The three Cu(II) centers in both complexes may be described as axially elongated octahedral. Magnetic susceptibility measurements reveal the weak anti-ferromagnetic coupling in the two complexes (J=−23.2cm−1 for 1 and −14.8cm−1 for 2).

Magneto-Structural Correlation Studies and Theoretical Calculations of a Unique Family of Single End-to-End Azide-Bridged NiII4 Cyclic Clusters

The work in this paper aims to portray a complete structural, magnetic, and theoretical description of two original end-to-end (EE) μ(1,3)-azide-bridged, cyclic tetranuclear Ni(II) clusters, [{Ni(II)(L(1))(μ(1,3)-N(3))(H(2)O)}(4)] (1) and [{Ni(II)(L(2))(μ(1,3)-N(3))(H(2)O)}(4)] (2), where the ligands used to achieve these species, HL(1) and HL(2), are the tridentate Schiff base ligands obtained from [1 + 1] condensations of salicylaldehyde with 1-(2-aminoethyl)-piperidine and 4-(2-aminoethyl)-morpholine, respectively. The title compounds, 1 and 2, crystallize in a monoclinic P2(1) space group. Overall, both species can be described in a similar way; where all Ni(II) centers within each molecule are hexacoordinated and bound to [L(1)](-) or [L(2)](-) through the phenoxo oxygen, imine nitrogen, and piperidine/morpholine nitrogen atoms of the corresponding ligand. The remaining coordination sites are satisfied by one molecule of H(2)O and two nitrogen atoms from N(3)(-) anions. The latest act as bridges between Ni(II) ions, and eventually, only four azido groups are linked to the same number of Ni(II) centers resulting in the formation of cyclic Ni(II)(4) systems. Interestingly, compounds 1 and 2 are the two sole examples of tetranuclear clusters generated exclusively by EE azide-bridging ligands to date. All the N(azide)-Ni-N(azide) moieties are almost linear in 1 and 2 indicating trans arrangement of the azido ligand. Variable-temperature (2-300 K) magnetic susceptibilities of 1 and 2 have been measured under magnetic fields of 0.04 T (from 2 to 30 K) and 0.7 T (from 30 to 300 K), and magneto-structural correlations have been performed. Despite the presence of both ferromagnetic and antiferromagnetic interactions in both compounds, significant differences have been observed in their magnetic behaviors directly related to the arrangement of the bridging azido ligands. Hence, compound 1 has an overall moderate antiferromagnetic behavior due to the presence of an exchange pathway with an unprecedented Ni-N···N-Ni torsion angle close to 0°, meanwhile complex 2 exhibits a predominant ferromagnetic behavior, with torsion angles between 50 and 90°. Density functional theory calculations have been performed to provide more insight into the magnetic nature of this new family of Ni(II)-azido complexes and also to corroborate the fitting of the data.

Magneto-structural correlations and DFT calculations in two rare tetranuclear copper(II)-clusters with doubly phenoxo and end-on azido bridges: Syntheses, structural variations and EPR studies

By slightly changing the synthetic conditions, we have prepared two closely related linear tetranuclear Cu II complexes with the symmetrical ONNO donor tetradentate Schiff-base ligand [ H 2L = (OH)C 6H 4(CH 3)C N(CH 2) 3N C(CH 3)C 6H 4(OH)] and with azide ions. These two distinctly coloured crystalline products were characterized by elemental analysis, IR and UV–Vis spectroscopy, CV, EPR spectra and variable temperature magnetic measurements. Single crystal X-ray diffraction studies of the green [Cu 4(μ-L) 2(μ 1,1-N 3) 2(N 3) 2] ( 1) and the red [Cu 4(μ-L) 2(μ 1,1-N 3) 2(N 3) 2(H 2O) 2] ( 2) crystals show that the coordination environment of the two μ-phenoxo and μ 1,1-azido bridged isomorphous tetranuclear Cu II complexes are slightly different. Thus, both complexes are formed by very similar building units, although with a significant variation in the bridging Cu–O(phenoxo)–Cu and Cu–N(azido)–Cu bond angles. The consequences of these structural variations on the magnetic properties have been investigated from both the experimental and theoretical points of view by variable temperature magnetic measurements and DFT calculations.

A Unique Example of Structural and Magnetic Diversity in Four Interconvertible Copper(II)−Azide Complexes with the Same Schiff Base Ligand: A Monomer, a Dimer, a Chain, and a Layer

Four new Cu(II)-azido complexes of formula [CuL(N(3))] (1), [CuL(N(3))](2) (2), [Cu(7)L(2)(N(3))(12)](n) (3), and [Cu(2)L(dmen)(N(3))(3)](n) (4) (dmen = N,N-dimethylethylenediamine) have been synthesized using the same tridentate Schiff base ligand HL (2-[1-(2-dimethylaminoethylimino)ethyl]phenol, the condensation product of dmen and 2-hydroxyacetophenone). The four compounds have been characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. Complex 1 is mononuclear, whereas 2 is a single mu-1,1 azido-bridged dinuclear compound. The polymeric compound 3 possesses a 2D structure in which the Cu(II) ions are linked by phenoxo oxygen atoms and two different azide bridges (mu-1,1 and mu-1,1,3). The structure of complex 4 is a double helix in which two mu-1,3-azido-bridged alternating one-dimensional helical chains of CuL(N(3)) and Cu(dmen)(N(3))(2) are joined together by weak mu-1,1 azido bridges and H-bonds. The complexes interconvert in solution and can be obtained in pure form by carefully controlling the conditions. The magnetic properties of compounds 1 and 2 show the presence of very weak antiferromagnetic exchange interactions mediated by a ligand pi overlap (J = -1.77) and by an asymmetric 1,1-N(3) bridge (J = -1.97 cm(-1)), respectively. Compound 3 presents, from the magnetic point of view, a decorated chain structure with both ferro- and antiferromagnetic interactions. Compound 4 is an alternating helicoidal chain with two weak antiferromagnetic exchange interactions (J = -1.35 and -2.64 cm(-1)).

Anion‐Dependent Facile Route to Magnetic Dinuclear and Dodecanuclear Cobalt Clusters

AbstractAn unprecedented dodecanuclear CoIII3CoII9 and a dinuclear CoII2 cluster were synthesized facilely from reactions of different coblt(II) salts with the ligand (1H‐benzimidazol‐2‐yl)methanol. The cobalt ions in the Co12 supercluster are linked into a disclike structures through μ3‐OL, μ‐OL, μ3‐O2–, μ1,1‐N3– and μ1,1,1‐N3– bridges. Magnetic studies reveal that strong ferromagnetic coupling through double end‐on (EO) azido bridges exists in 1, while both ferromagnetic coupling through the μ3‐OL and μ‐OL pathways and antiferromagnetc coupling through the μ1,1,1‐N3– pathway exist in 2, which results in a ferrimagnetic behaviour of 2.

Single end-on azido bridged 1D chain copper(II) complex: Synthesis, X-ray crystal structure and catalytic activity in homogeneous epoxidation of cyclooctene

A new azido derivative of a NNO donor tridentate Schiff-base copper(II) complex, [CuL(μ 1,1-N 3)] n ( 1) (HL = 1-(N- ortho-hydroxyacetophenimine)-2-(N-ethyl)aminoethane), containing a single end-on μ 1,1-azido bridged 1D infinite chain has been synthesized and characterized. X-ray single crystal structure analysis reveals that the complex [CuL(μ 1,1-N 3)] n ( 1) is a 1D chain in which neighboring Cu(II) chromophores are related by glide planes and linked by single azido bridges in the EO mode. No measurable magnetic interaction was evidenced in the complex [CuL(μ 1,1-N 3)] n ( 1) through variable temperature magnetic susceptibility measurements (10–300 K). The complex was used as an active catalyst for the epoxidation of cyclooctene using tert-butyl-hydroperoxide as an oxidant. The catalytic activity of the complex has been compared in a series of solvents. The results show that in acetonitrile medium, the epoxide was produced in high yield with high selectivity.

132 The change of tumour size between diagnosis and surgical treatment in breast cancer patients

The new neutral binuclear lead(II) azido coordination compound, [Pb2(tmph)2(μ-N3)2(CH3COO)2] (1) [tmph = 3,4,7,8-tetramethyl-1,10-phenanthroline], has been synthesized by a sonochemical method. Single crystal X-ray structure shows that the overall structure of 1 is binuclear unit. Complex 1 has a bridging azido pathway, end-to-end bridging azides between a pair of lead(II) centers. This is further extended into a one-dimensional (1D) and three-dimensional (3D) supramolecular structure by Pb⋯C and π–π weak directional intermolecular interactions. The coordination number of lead(II) ions is seven, PbN4O3, with two N-donor atoms from tmph ligands and three O-donors from acetate anions and two N-donors from two azide anions. It has a “stereo-chemically active” electron lone pair, and the coordination sphere is hemidirected. The PbO nanoparticles were obtained by thermolysis of 1 at 180 °C with oleic acid as a surfactant. The morphology and size of the prepared PbO samples were further observed using scanning electron microscopy (SEM).

Two new azido bridging Mn(II) 1D systems: Synthesis and characterization of trans-[Mn(N 3) 2(2-aminopyridine) 2] n and trans-[Mn(N 3) 2(4-azidopyridine) 2] n

Two new manganese(II) azido complexes [Mn(L) 2(N 3) 2] n with L = 2-aminopyridine ( 1) and 4-azidopyridine ( 2) have been synthesized and structurally characterized by spectroscopic and crystallographic methods. Both complexes 1 and 2 crystallize in the triclinic system, space group P-1, and their structures are featuring six-coordinate manganese centres, chains of [Mn(N 3) 2] n , and two trans 2-aminopyridine or 4-azidopyridine ligands giving 1D systems. In the [Mn(N 3) 2] n -chains of 1 each manganese atom is connected by double di end-on (EO) azido bridges forming cyclic Mn 2N 2 units, whereas in 2, the metal centers are alternatively bridged by double di-end-to-end (EE) and double di end-on (EO) azido ligands. The intra-chain Mn…Mn distances are 3.5350(12) in 1, and 3.3701(18) and 5.032(3) Å, in 2, respectively. In 1 the polymeric chains of polyhedra are connected by hydrogen bonds of type N–H…N to generate a 2D supramolecular network. Magnetic susceptibility measurements were performed only for complex 1 which shows weak ferromagnetic interactions with a J value of 1.2 cm −1.

Synthesis, crystal structure and magnetic properties of three unprecedented tri-nuclear and one very rare tetra-nuclear copper(ii) Schiff-base complexes supported by mixed azido/phenoxo/nitrato or acetato bridges

Three novel mixed bridged trinuclear and one tetranuclear copper(II) complexes of tridentate NNO donor Schiff base ligands [Cu(3)(L(1))(2)(mu(1,1)-N(3))(2)(CH(3)OH)(2)(BF(4))(2)] (1), [Cu(3)(L(1))(2)(mu(1,1)-N(3))(2)(mu-NO(3)-1kappaO:2kappaO')(2)] (2), [Cu(3)(L(2))(2)(mu(1,1)-N(3))(2)(mu-NO(3)-1kappaO:2kappaO')(2)] (3) and [Cu(4)(L(3))(2)(mu(1,1)-N(3))(4)(mu-CH(3)COO-1kappaO:2kappaO')(2)] (4) have been synthesized by reaction of the respective tridentate ligands (L(1) = 2-[1-(2-dimethylamino-ethylimino)-ethyl]-phenol, L(2) = 2-[1-(2-diethylamino-ethylimino)-ethyl]-phenol, L(3) = 2-[1-(2-dimethylamino-ethylimino)-methyl]-phenol) with the corresponding copper(ii) salts in the presence of NaN(3). The complexes are characterized by single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. Complex 1 is composed of two terminal [Cu(L(1))(mu(1,1)-N(3))] units connected by a central [Cu(BF(4))(2)] unit through nitrogen atoms of end-on azido ligands and a phenoxo oxygen atom of the tridentate ligand. The structures of 2 and 3 are very similar; the only difference is that the central unit is [Cu(NO(3))(2)] and the nitrate group forms an additional mu-NO(3)-1kappaO:2kappaO' bridge between the terminal and central copper atoms. In complex 4, the central unit is a di-mu(1,1)-N(3) bridged dicopper entity, [Cu(2)(mu(1,1)-N(3))(2)(CH(3)COO)(2)] that connects two terminal [Cu(L(3))(mu(1,1)-N(3))] units through end-on azido, phenoxo oxygen and mu-CH(3)COO-1kappaO:2kappaO' triple bridges to result in a tetranuclear unit. Analyses of variable-temperature magnetic susceptibility data indicates that there is a global weak antiferromagnetic interaction between the copper(II) ions in complexes 1-3, with the exchange parameter J of -9.86, -11.6 and -19.98 cm(-1) for 1-3, respectively. In complex 4 theoretical calculations show the presence of an antiferromagnetic coupling in the triple bridging ligands (acetato, phenoxo and azido) while the interaction through the double end-on azido bridging ligand is strongly ferromagnetic.

Tridentate (NNO) Schiff-base copper(II) complex: synthesis, crystal structure, and magnetic study

A new azido adduct of a tridentate Schiff-base copper(II) complex has been synthesized and characterized structurally and magnetically. X-ray single crystal structure analysis reveals that the asymmetric unit of [Cu2(L)2(µ1,1-N3)2][Cu(L)(N3)] (1) [HL = 1-(N-ortho-hydroxyacetophenimine)-2,2-diethyl-aminoethane] has two independent moieties. One of these forms a dimer, containing end-on azido bridges, with its center of inversion related equivalents. The complex crystallizes in monoclinic space group P21/c with a = 10.112(2), b = 31.938(4), c = 9.718(2) Å and β = 95.00(2)°. Variable temperature magnetic susceptibility data show antiferromagnetic interactions between copper(II) centers.

Synthesis, crystal structures and xanthine oxidase inhibitory activities of two copper(II) complexes with Schiff bases

Two azido-coordinated Schiff base Cu(II) complexes with the formulae [Cu(L1)(N3)]·MeOH and [Cu(L2)(μ1,1-N3)] n , where L1 is the deprotonated form of 2-chloro-2-[(2-ethylaminoethylimino)methyl]phenol, and L2 is the deprotonated form of 2,4-dibromo-6-[(2-dimethylaminoethylimino)methyl]phenol, have been synthesized and characterized by physico-chemical and spectroscopic methods. The X-ray crystal structures of both complexes have been determined. The Cu atom in [Cu(L1)(N3)]·MeOH is four-coordinate in a square planar geometry, while [Cu(L2)(μ1,1-N3)] n is five-coordinate with a square pyramidal geometry. The molecules in [Cu(L1)(N3)]·MeOH are linked by intermolecular O–H···O and N–H···O hydrogen bonds, forming dimers. The molecules in [Cu(L2)(μ1,1-N3)] n are linked through end-on azido bridges, forming one-dimensional chains. The xanthine oxidase inhibitory activities of both complexes were evaluated.

Synthesis, crystal structure, luminescent property and DFT investigation on a novel metal–organic framework constructed from rigid tetrapodal ligand 1,2,3,4-tetra(4-pyridyl)thiophene

Employing the tetrapodal compound 1,2,3,4-tetra(4-pyridyl)thiophene (TPT) as a bridging ligand, a new metal–organic framework was obtained and characterized by single crystal X-ray diffraction, [Cd(TPT)(N 3 ) 2 ·(H 2 O)] ( 1 ). It exhibits a 2D layer network constructed from the three-connector TPT and EE azido bridges. It also displays good thermal stability and strong photoluminescence in the blue regionband thus may serve as a candidate of thermally stable blue-light-emitting electroluminescence material. Employing the tetrapodal compound 1,2,3,4-tetra(4-pyridyl)thiophene (TPT) as a bridging ligand, a new metal–organic framework was obtained and characterized by single crystal X-ray diffraction, [Cd(TPT)(N 3 ) 2 ·(H 2 O)] ( 1 ). This polymer exhibits a 2D layer network and an unprecedented 3,4-connected topology, which is constructed from the three-connector TPT and EE azido bridges. It also displays good thermal stability and strong photoluminescence in the blue regionband thus may serve as a candidate of thermally stable blue-light-emitting electroluminescence material. The nature of electronic transitions in the photoluminescent process has also been investigated by means of time-dependent density functional theory (TDDFT) calculations and molecular orbital analyses, which shows that the luminescent property is ligand-based.

CuII-Azide Polymers of Cu3 and Cu6 Building Units: Synthesis, Structures, and Magnetic Exchange Mechanism

Two new neutral copper-azido polymers [Cu(3)(N(3))(6)(tmen)(2)](n) (1) and [Cu(6)(N(3))(12)(deen)(2)](n) (2) [tmen = N,N,N',N'-tetramethylethylenediamine and deen = N,N'-diethylethylenediamine] have been synthesized by using lower molar equivalents of the chelating diamine ligands with Cu(NO(3))(2).3H(2)O and an excess of NaN(3). The single crystal X-ray structure shows that in the basic unit of the 1D complex 1, the three Cu(II) ions are linked by double end-on azido bridges with Cu-N(EO)-Cu angles on both sides of the magnetic exchange critical angle of 108 degrees. Complex 2 is a 3D framework of a basic Cu(6) cluster. Cryomagnetic susceptibility measurements over a wide range of temperature exhibit dominant ferromagnetic behavior in both the complexes. Density functional theory calculations (B3LYP functional) have been performed on the trinuclear unit to provide a qualitative theoretical interpretation of the overall ferromagnetic behavior shown by the complex 1.

Single End‐to‐End Azidocopper(II) Chain Based on an Electroactive Ligand: A Structural, Electrochemical, Magnetic and Ab Initio Study

AbstractBy combining azide and the (Z)‐1,1,1‐trifluoro‐4‐(quinolin‐8‐ylamino)but‐3‐en‐2‐one enaminone ligand, HL, an azido‐bridged copper(II) one dimensional polymer was synthesized in a one‐pot reaction. The solved and refined crystal structure evidenced the unusual single and asymmetric end‐to‐end coordination mode of the azide ion. The redox properties of this complex were studied by cyclic voltammetry, andoxidation of the azido bridge was evidenced. Magneticmeasurements, combined with magnetostructural‐driven analysis revealed a weak ferromagnetic interaction between the copper(II) ions within the N3–‐bridged chains, complemented by an antiferromagnetic interaction between the chains mediated by π–π interactions. A survey of the scarce literature of single end‐to‐end azido bridges, associated with quantum chemical ab initio calculations, was carried out to tentatively identify the relevant parameters driving the weak intrachain exchange interaction.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Ladder-like azido-bridged copper(II) complexes: Synthesis, X-ray structure and magnetic study

Two mixed-ligand copper(II) complexes [{Cu(L 1)(μ 1,3-N 3)}{Cu(L)(μ 1,3-N 3)(μ 1,1-N 3)}] n ( 1) [HL 1 = 1-( N-ortho-hydroxyacetophenimino)-2,2-dimethyl-aminoethane; L = 2-(dimethylamino)-ethylamine] and [{Cu(L 2)(μ 1,3-N 3)}{Cu(L)(μ 1,3-N 3)(μ 1,1-N 3)}] n ( 2) [HL 2 = 1-( N-5-methoxy-ortho-hydroxyacetophenimino)-2,2-dimethyl-aminoethane] have been formed upon addition of aqueous solution of sodium azide to a methanolic solution of copper nitrate trihydrate and corresponding Schiff-base ligands. The ligands, HL 1 and HL 2 undergo partial hydrolysis of their imine bond during the course of reaction. Both the complexes contain single end-to-end (μ 1,3) azido bridged 1D infinite chains (rail) which propagate parallel to the crystallographic b-axis; neighboring chains are interconnected by pairs through double asymmetric end-on (μ 1,1) azido bridges (rung) to yield a ladder-like structure. In both complexes, rungs (end-on azido bridges) do not connect copper centers of the chains like in a regular ladder; instead they connect only the alternating copper sites of the 1D chain. In a chain the coordination environment around copper(II) ions are not the same: while the {Cu(L 1)(μ 1,3-N 3)} and {Cu(L 2)(μ 1,3-N 3)} moieties have a penta-coordinated copper(II) center, the copper(II) ion of the neighboring {Cu(L 1)(μ 1,3-N 3)(μ 1,1-N 3)} or {Cu(L 2)(μ 1,3-N 3)(μ 1,1-N 3)} moiety has an octahedral coordination environment. The variable temperature (2–300 K) magnetic susceptibility measurements showed that the magnetic interaction between the metal centers in complexes 1 and 2 is dominantly antiferromagnetic. The results of magnetic model are in good agreement with the experimental data.

Four novel Co(II) and Mn(II) coordination polymers with triazolyl derivate: Syntheses, crystal structures and magnetic properties

Four novel coordination polymers, one-dimensional chains [M(PTE) 2(N 3) 2] n (M = Mn for 1 and Co for 2), and two-dimensional layers [M(PTE) 2(dca) 2] n (M = Mn for 3 and Co for 4) (PTE = 1-(2,4-difluorophenyl-2-(1H-1,2,4-triazol-1-yl)ethanone, dca = dicyanamide anion, N(CN) 2 −), have been synthesized under mild ambient conditions and structurally characterized by single crystal X-ray diffraction. In all four crystal structures, the metal atoms adopt octahedral coordination geometry with six nitrogen atoms from two monodentate PTE ligands and four azido (or dca) bridging ligands. The crystal structures of 1 and 2 are isostructural 1-D polymeric chains, alternatively linked by double end-on and double end-to-end azido bridges. However, the bent dca ligands as bidentate μ 2-1,5 bridging ligands interlink the octahedral metal units to lead to 2-D (4,4) grid networks in 3 and 4. Temperature-dependent magnetic measurements in 2–300 K have been performed for these four polymers, and suggest alternative ferro- and antiferromagnetic couplings for end-on and end-to-end azido bridges in 1, and the dominant ferromagnetic coupling in 2, respectively. Both polymers 3 and 4 show weak antiferromagnetic exchanges through the μ 2-1,5-dca bridges. The effects of auxiliary coligands on the structure and the nature of these magnetic exchanges are discussed in the light of the crystal structures in detail.

Structural and magnetic behavior of mono- and dinuclear nickel (II) complexes of N, N′-bis-(3,5-dipiperidin-1-yl-[2,4,6]triazin-1-yl)-pyridin-2-ylmethyl-ethane-1,2-diamine

Reaction of nickel (II) perchlorate with the ligand N, N′-bis-(3,5-dipiperidin-1-yl-[2,4,6]triazin-1-yl)-pyridin-2-ylmethyl-ethane-1,2-diamine yields an octahedral Ni(II) high-spin complex 1 ([C 40H 56N 14Ni(H 2O)(CH 3OH)](ClO 4) 2(CH 3OH) 2) with moderate zero-field splitting (ZFS) axial distortion parameter D/ k B = 5.37 K. The ligand contributes a N4 donor set; the remaining two coordinating positions are occupied by coordinating solvents molecules. Exchange of the coordinating solvents molecules in complex 1 to thiocyanate moieties leads to formation of complex 2 ([C 40H 56N 14Ni(NCS) 2](CHCl) 3) with an extended parameter D/ k B = 8.80 K. The analysis of the structural and magnetic properties of complexes 1 and 2 led to the design of dinuclear complex 3 ([C 40H 56N 14NiN 3] 2(ClO 4) 2(CH 3OH) 2), where two azido groups were utilized as bridging ligands. The double azido bridges in complex 3 cross each other to form a rarely observed non-coplanar (N 3) 2 structure. The magnetic behavior of complex 3 reveals ferromagnetic coupling interactions characterized by J/ k B = 23.25 K, D 1/ k B = 7.90 K, D 2/ k B = 0.54 K.

Competing Large and Small Angles in a Double End‐On Azido Copper(II) Binuclear Complex: A Combined Experimental and Theoretical Study of Magnetic Interactions

AbstractThe structure and magnetic properties of double azido‐bridged CuII binuclear complex 1 with the chelating chiral ligand (S,S)‐2,2′‐isopropylidenebis(4‐phenyl‐2‐oxazoline) were analyzed by combining experimental and theoretical techniques. The CuII ions adopt a square pyramidal geometry with different degrees of distortion, whereas the two end‐on azido bridges disposed at the equatorial positions exhibit significantly different Cu–N–Cu angles, 110.6 and 97.3°, which are respectively smaller and larger than the critical 108° value distinguishing the ferromagnetic and antiferromagnetic regimes. The asymmetry in 1 arises from the use of the bulky asymmetric ligand, giving rise to two different magnetic pathways between the CuII ions. The magnetic pathway along the large Cu–N–Cu angle value dominates over the small one, resulting in a net antiferromagnetic behavior with J = –78.6 cm–1. On the basis of wavefunction calculations, we investigate the exchange interactions in synthetic compound 1 and fictitious analogs 2 and 3 holding either two large (i.e., 110.6°) or two small (i.e., 97.3°) Cu–N–Cu angles. The calculated exchange interaction in 1(–104 cm–1) is in relatively good agreement with the experimental value and corresponds precisely to the average between the antiferromagnetic value in 2 (–218 cm–1) and the ferromagnetic one in 3 (21 cm–1). The significant enhancement in the antiferromagnetic contribution accompanying the expansion of one of the Cu–N–Cu bridging angles is undoubtedly the driving force for the observed antiferromagnetic behavior in 1. The control of the local metal environments allowed us to monitor the exchange coupling interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Halo and azido copper(II) coordination polymers featuring the gem-diolate forms of di-2-pyridyl ketone

The reactions of di-2-pyridyl ketone, (py) 2CO, with [Cu 2(O 2CMe) 4(H 2O) 2] in the presence of NaN 3, HCl and HBr have led to the isolation of complexes {[Cu 8{(py) 2CO 2} 4(N 3) 6(O 2CMe) 2]·2MeCN·H 2O} ∞ ( 1·2MeCN·H 2O), [Cu 2{(py) 2C(OH)O}Cl 3] ∞ ( 2) and [Cu 2{(py) 2C(OH)O}Br 3] ∞ ( 3), respectively, where (py) 2 CO 2 2 - and (py) 2C(OH)O − are the dianion and the monoanion of the gem-diol form of (py) 2CO. Complex 1·2MeCN·H 2O is an 1D coordination polymer consisting of centrosymmetric [Cu 8{(py) 2CO 2} 4(N 3) 6(O 2CMe) 2] cluster units linked through weakly coordinated azido bridges. The (py) 2 CO 2 2 - groups adopt the η 1: η 2: η 2: η 1: μ 4 coordination mode, while the N 3 - ions behave as η 2: μ and η 1: η 2: μ 3 ligands. The isostructural compounds 2 and 3 are also 1D coordination polymers consisting of {Cu 2{(py) 2C(OH)O}X 3} 2 units (X=Cl, Br) linked through double halo bridges. The (py) 2C(OH)O - ligand adopts the tridentate, bis-chelating η 1: η 2: η 1: μ mode. A common feature in the three complexes is the presence of interchain H-bonding interactions which result in the formation of 2D networks. The magnetic properties of 1– 3 have been studied by variable-temperature dc magnetic susceptibility and variable-field magnetization techniques. The analyses of the magnetic data were performed taking into account only the dominant exchange interactions within dinuclear subunits. The intradinuclear exchange interactions have been found to vary from strongly and moderately antiferromagnetic in 1 to ferromagnetic in 2 and 3. This work demonstrates the flexibility, versatility and synthetic potential of combining (py) 2CO with carboxylate and azido or halo ligands.