Azide Bridges Research Articles

Magnetic coupling in EE and EO azido-bridged binuclear copper complexes: Synthesis, structure and magnetic studies

Four azide bridged dinuclear copper(II) complexes, [Cu 2(L X) 2(N 3) 2](ClO 4) 2, with L X = substituted N, N-bis[(3,5-dimethylpyrazole-1-yl)-methyl]benzylamine, [X = H ( 1), OMe ( 2), Me ( 3) and Cl ( 4)] have been synthesized, out of which complexes 1 and 2 have been characterized structurally. In Complex 1 the two bridging azide ligands have connected the two metal centers in an end-on ( EO) fashion with aSP (asymmetric Square Pyramidal) geometry and showed an weak antiferromagnetic interaction ( J = −3.34 cm −1). On the contrary, in complex 2, the two metal centers have been connected in end-to-end ( EE) fashion exhibiting moderately strong ferromagnetic interaction ( J = +19.7 cm −1). Cyclic voltammetric studies performed on all the four complexes show a reasonably good correlations when E 1/2 for Cu IICu II → Cu IICu III and Cu IICu III → Cu IIICu III oxidations are plotted against σ (substituent constants) with ρ = −0.182 ( R 2 = 0.92) and −0.684 ( R 2 = 0.99) respectively.

Structures and magnetism of azide- and carboxylate-bridged metal(ii) systems derived from 1,2-bis(N-carboxymethyl-4-pyridinio)ethane

Four coordination polymers of different transition metal ions with azide and the zwitterionic dicarboxylate ligand 1,2-bis(N-carboxymethyl-4-pyridinio)ethane (bcpe) were synthesized, and structurally and magnetically characterized. They are formulated as [M(2)(bcpe)(N(3))(4)].H(2)O (M = Mn, 1; Co, 2; and Ni, 3) and [Cu(3)(bcpe)(N(3))(6)].(H(2)O)(2) (4). In the isomorphous compounds , octahedral metal ions are linked by the mixed (micro(2)-syn,syn-COO)(mu(2)-EO-N(3))(2) triple bridges (EO = end-on) to give anionic uniform chains, which are cross-linked by the cationic bis(pyridinium) spacers to produce two-dimensional coordination layers. Magnetic studies demonstrated that the magnetic coupling through the mixed triple bridge is antiferromagnetic in the Mn(ii) compound (1) but ferromagnetic in the Co(ii) and Ni(ii) species (2 and 3). Compound 4 also consists of two-dimensional coordination layers in which Cu(ii) chains are interlinked by the organic spacers, but the chain has mixed mu(2)-EO-azide, mu(3)-EO-azide and mu(2)-O(carboxylate) bridges and features tetranuclear dicubane-based units sharing Cu ions or alternatively linear trinuclear units connected by long axial Cu-N/O bonds. Magnetic studies suggested that the Cu(ii) ions linked by the double azide bridges in the equatorial-equatorial fashion are strongly coupled to give a ferromagnetic S = 3/2 ground state for the trinuclear units, with very weak antiferromagnetic interactions through the equatorial-axial bridges between the units.

Mono- and di-nuclear azido η6-p-cymene ruthenium(II) complexes; synthesis, reactivity, and structures

The azide bridge complex [(η6-p-cymene)Ru(µ-N3)Cl]2 (2) was prepared from the reaction of sodium azide with [(η6-p-cymene)RuCl]2 in ethanol. The molecular structures and spectroscopic properties of the various azido ruthenium complexes so obtained from the reaction with monodentate and bidentate ligands are described.

Synthesis, crystal structure, and magnetism of a binuclear Cu(II) complex with a single end-to-end bridged azido ligand

A binuclear copper(II) complex, [Cu2(μ 1,3-N3)(N3)(pmp)2(ClO4)]ClO4 (pmp = 2-((pyridin-2-yl) methoxy)-1,10-phenanthroline), was synthesized with a single azide as end-to-end bridge ligand, and pmp and perchlorate as ligands. In the crystal, Cu(II) is in a distorted square pyramidal geometry, and a single azide bridges equatorial-axial linking two Cu(II) ions with separation of 5.851 Å. There are π−π stacking interactions involving 1,10-phenanthroline rings. The variable-temperature (2–300 K) magnetic susceptibilities were analyzed using a binuclear Cu(II) magnetic formula and it indicates that there is a very weak ferromagnetic coupling with 2J = 2.82 cm−1.

Two EE-Azido-Bridged Nickel(II) Layered Compounds: Vigorous Twisted Torsion Angle Ni−N3−Ni Results in Ferromagnetic Behavior

Two coordination polymers, Ni(endi)(N(3))(2) (endi = 1,2-bis(tetrazol-1-yl)ethane) (1) and Ni(4-acpy)(2)(N(3))(2) (4-acpy = 4-acetylpyridine) (2), are obtained by employing a couple of cobalt complex as references. Both compounds have similar 2D (4,4) EE azide-nickel layer structures, but different interlayer separations. Their EE azide bridges are vigorously twisted, with the torsion angle tau value 88.3 degrees and 107.6 degrees for 1 and 89.2 degrees for 2. Different from most EE azide compounds, ferromagnetism is distinctly present, ordering below T(c) = 25 K for 1 and T(c) = 23 K for 2. Fitting of magnetic susceptibility data using the spin Hamiltonian H = -2J SigmaS(1)S(2) gives the ferromagnetic intralayer coupling J = 14.70(6) cm(-1) for 1 and 14.32(0) cm(-1) for 2, respectively. The magnetostructural correlations of 1 have been calculated using the density function theory based method. The computational results are consistent with the trend of the experimental data. One possible mechanism was proposed to explain the emergence of ferromagnetism based on the theoretical studies, and the ferromagnet construction approach was also proposed accordingly.

Poly[(μ2-azido-κ2N1:N1)[μ2-5-(8-quinolyloxymethyl)tetrazolato-κ4N1,O,N5:N4]zinc(II)

In the title compound, [Zn(C11H8N5O)(N3)]n, the Zn atom is hexa­coordinated by five N atoms and one O atom in a distorted octa­hedral geometry. The chelating 5-(8-quinolyloxymeth­yl)tetra­zolate ligands are approximately planar, with a dihedral angle of 3.6 (2)° between the quinoline and tetra­zole planes. Adjacent Zn atoms are linked by two bridging azide ligands across a centre of inversion, and further coordination by one N atom of an adjacent tetra­zole unit forms two-dimensional frameworks in (100). C—H⋯N inter­actions exist between ligands in neighbouring layers.

Synthesis and Crystal Structures of a Pair of Azido-Bridged Polynuclear Schiff Base Zinc(II) Complexes

A pair of novel azido-bridged polynuclear zinc(II) complexes, [Zn2(L1)2(μ1,1-N3)2]n (1) and [Zn2(L2)2(μ1,1-N3)(μ1,3-N3)] n (2) (HL1 = 2,4-dichloro-6-[(2-ethylaminoethylimino)methyl]phenol, HL2 = 2-bromo-4-chloro-6-[(2-ethylaminoethylimino)methyl]phenol), have been synthesized and structurally characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Each zinc(II) atom in the complexes is in a trigonal-bipyramidal coordination, with one imine N atom of a Schiff base ligand and two N atoms from two bridging azide ligands defining the basal plane, and one phenolate O and one amine N atoms of the Schiff base ligand occupying the two axial positions.

Influence of the steric effects of the Schiff bases and the hydrogen bonds on the bridging modes of the azide groups: Syntheses and crystal structures of three azide-bridged Schiff base zinc(II) complexes

Abstract Three polymeric zinc(II) complexes, derived from the end-on azide (μ1,1-N3) and end-to-end azide (μ1,3-N3) bridges and similar tridentate Schiff base ligands, have been synthesized and structurally characterized. The zinc(II) atom in each complex is in a midway between trigonal–bipyramidal and square–pyramidal coordination. The slight difference of the steric effects of the Schiff bases and the hydrogen bonds can influence the bridging modes of the azide groups.

Anion directed template synthesis of Cu(II) complexes of a N,N,O donor mono-condensed Schiff base ligand: A molecular scaffold forming highly ordered H-bonded rectangular grids

Anion directed, template syntheses of two dinuclear copper(II) complexes of mono-condensed Schiff base ligand Hdipn (4-[(3-aminopentylimino)-methyl]-benzene-1,3-diol) involving 2,4-dihydroxybenzaldehyde and 1,3-diaminopentane were realized in the presence of bridging azide and acetate anions. Both complexes, [Cu 2(dipn) 2(N 3) 2] ( 1) and [Cu 2(dipn) 2(OAc) 2] ( 2) have been characterized by X-ray crystallography. The two mononuclear units are joined together by basal–apical, double end-on azido bridges in complex 1 and by basal–apical, double mono-atomic acetate oxygen-bridges in 2. Both complexes form rectangular grid-like supramolecular structures via H-bonds connecting the azide or acetate anion and the p-hydroxy group of 2,4-dihydroxybenzaldehyde. Variable-temperature (300–2 K) magnetic susceptibility measurements reveal that complex 1 has antiferromagnetic coupling ( J = −2.10 cm −1) through the azide bridge while 2 has intra-dimer ferromagnetic coupling through the acetate bridge and inter-dimer antiferromagnetic coupling through H-bonds ( J = 2.85 cm −1, J′ = −1.08 cm −1).

Tuning the Structure and Magnetism of Azido-Mediated CuIISystems by Coligand Modifications

Through the use of a series of structurally related benzoates bearing different substituents as coligands, three new azido-copper compounds, [Cu(benzoate)(N(3))](n) (1), [Cu(2-methyl-benzoate)(N(3))](n) (2), and [Cu(1-naphthoate)(N(3))](n) (3), have been successfully obtained and structurally and magnetically characterized. Single-crystal structure analyses indicated that the uncoordinating substituents in the benzoates greatly affect the structure of the complexes. Complex 1 displays isolated ferromagnetic chains with the largest Cu-N-Cu angle in known carboxylate/end-on-azido mixed-bridged copper systems, while complexes 2 and 3 were 2D coordination polymers, containing mu-(1,1,3,3) and mu-(1,1,3) bridging azides and exhibiting new azido-copper networks with (4(4)) and (4.8(2)) topologies, respectively. Furthermore, 2 was a chiral complex obtained through spontaneous resolution. In the low-temperature range, both 2 and 3 showed spontaneous magnetization with characteristics of soft ferromagnetic magnetism with phase transition temperatures of 13 and 10 K, respectively.

M2(N3)4(hmt)(H2O) (M = Co2+ and Ni2+, hmt = hexamethylenetetramine): mixed azide-hmt bridged 3D metal frameworks with long-range magnetic ordering

Two mixed azide-hmt bridged compounds were obtained with neutral 3D networks, Co2(N3)4(hmt)(H2O) (1) and Ni2(N3)4(hmt)(H2O) (2), hmt = hexamethylenetetramine. In 1, the azide ions present three kinds of coordination modes in the connection of two unique Co2+ ions. Each Co1 is connected by trans-EE-azide ions and hmt into extended (4,4) layers, and each Co2 is connected by EO-azide ions into dimers which are located between the neighboring (4,4) layers. The cis-EE-azide ions connect the dimers to the neighboring layers to form rare 3D networks. The Co12+ and Co22+ ions have four and three connections through azide bridges to the neighboring Co2+ ions, respectively. Twisted torsion angles of cis/trans-EE azide bridges are observed in 1, with a value of 83.39 and 117.43°, respectively. The Ni analogue 2 is isostructural with 1 revealed by IR, elemental analysis and Powder X-ray diffraction. Magnetic investigation shows that 1 is a weak ferromagnet below Tc = 15.0 K, with a large coercivity of 1 T at 2 K, while 2 is a soft ferromagnet below Tc = 10.0 K.

Synthesis, structure and ferromagnetic properties of a copper(II) coordination polymer with azide and 4-pyridylacrylate

A Cu(II) complex with azide and 4-pyridylacrylic acid (4-Hpya), [Cu 2(4-pya) 2(N 3) 2(DMF) 2] ( 1) has been synthesized and characterized crystallographically and spectroscopically. This compound consists of binuclear units in which Cu(II) ions are connected through two equatorial–equatorial end-on azido bridges. The Cu(II) dimers are interlinked by 4-pya to generate two-dimensional coordination polymers. Magnetic investigations revealed a relatively strong ferromagnetic interaction through the azide bridges with J = 145 cm −1, and a weak ferromagnetic interdimer interaction through the long but π-conjugated 4-pya ligands. The magneto-structural correlations have been discussed in comparison with other Cu(II) dimers with the same bridging motif.

Unprecedented Self-Catenated Eight-Connected Network Based on Novel Azide-Bridged Tetramanganese(II) Clusters

The combination of the azide bridge and a neutral inner-salt-type dicarboxylate ligand leads to a three-dimensional coordination framework that contains unprecedented azide-bridged tetramanganese(II) clusters and defines a novel self-catenated, eight-connected net of 4(16) x 6(12) topology.

Facile Synthesis of Monoazidotitanium Isopropoxides

The monoazidotitanium trisisopropoxide {(N(3))Ti(OiPr)(3)}(4) (2) was obtained by the reaction of (N(3))(2)Ti(OiPr)(2) (1) with Ti(OiPr)(4). Colorless 2 possesses an interesting tetrameric structure featuring bridging azide and isoproxide ligands and five- and six-coordinate titanium centers. It can be sublimed in vacuo at ca. 130 degrees C but decomposes rapidly above 180 degrees C. Controlled hydrolysis afforded the related yellow oxo cluster (iPrO)(8)Ti(4)(mu-OiPr)(2)(mu(4)-O)(mu-N(3))(4) (3).

Synthesis, Crystal Structure, and Cytochrome P450-Like Hydroxylation Property of a Novel Azido-Bridged Manganese(III) Complex Derived from 2-[(2-Phenylaminoethylimino)Methyl]Phenol

A novel end-to-end azido-bridged polynuclear manganese(III) complex, [MnL 2 ( μ 1,3 -N 3 )] · 2MeCN (HL = 2-[(2-phenylaminoethylimino)methyl]phenol), has been synthesized and characterized by elemental analysis, IR, and single crystal X-ray diffraction. Each Mn III atom in the complex has an octahedral coordination, being coordinated by two phenolic O and two imine N atoms from two Schiff base ligands, and by two terminal N atoms from two bridging azide groups. The determination studied by GC/MS analysis indicated that the complex has catalytic property for the dioxygen oxidization of cyclohexane.

Anion Influence on the Structure and Magnetic Properties of a Series of Multidimensional Pyrimidine-2-carboxylato-Bridged Copper(II) Complexes

Seven new polynuclear copper(II) complexes of formula [Cu(mu-pymca)2] (1) (pymca(-) = pyrimidine-2-carboxylato), [Cu(mu-pymca)Br] (2), [Cu(mu-pymca)Cl] (3), [Cu(mu-pymca)(SCN)(H2O)] x 4 H2O (4), [Cu(mu-pymca)N3] (5), [Cu2(mu1,5-dca)2(pymca)2] (6) (dca = dicyanamide), and K{[mu-Au(CN)2]2[(Cu(NH3)2)2(mu-pymca)]}[Au(CN)2]2 (7) have been synthesized by reactions of K-pymca with copper(II) ions in the presence of different counteranions. Compound 1 is a linear neutral chain with a carboxylato bridging ligand in a syn-anti coordination mode, whereas complexes 2 and 3 consist of cationic linear chains with cis and trans bis(chelating) pymca bridging ligands. Complex 4 adopts a helical pymca-bridged chain structure. In complex 5, zigzag pymca-bridged chains are connected by double end-on azide bridging ligands to afford a unique honeycomb layer structure. Complex 6 is a centrosymmetric dinuclear system with double mu 1,5-dicyanamide bridging ligands and pymca end-cap ligands. Complex 7 is made of pymca-bridged dinuclear [Cu(NH3)2(mu-pymca)Cu(NH3)2](3+) units connected by [Au(CN)2](-) anions to four other dinuclear units, giving rise to cationic (4,4) rectangular nets, which are linked by aurophilic interactions to afford a singular 3D network. Variable-temperature magnetic susceptibility measurements show that complex 1 exhibits a very weak antiferromagnetic coupling through the syn-anti (equatorial-axial) carboxylate bridge (J = -0.57 cm(-1)), whereas complexes 2-4 and 7 exhibit weak to strong antiferromagnetic couplings through the bis(chelating) pymca bridging ligand J = -17.5-276.1 cm(-1)). Quantum Monte Carlo methods have been used to analyze the experimental magnetic data for 5, leading to an antiferromagnetic coupling (J = -34 cm(-1)) through the pymca ligand and to a ferromagnetic coupling (J = 71 cm(-1)) through the azide bridging ligands. Complex 6 exhibits a very weak antiferromagnetic coupling through the dicyanamide bridging ligands (J = -5.1 cm(-1)). The magnitudes of the magnetic couplings in complexes 2-5 have been explained on the basis of the overlapping between magnetic orbitals and DFT theoretical calculations.

Anion‐Directed Template Synthesis and Hydrolysis of Mono‐Condensed Schiff Base of 1,3‐Pentanediamine and o‐Hydroxyacetophenone in NiII and CuII Complexes

AbstractBis(o‐hydroxyacetophenone)nickel(II) dihydrate, on reaction with 1,3‐pentanediamine, yields a bis‐chelate complex [NiL2]·2H2O (1) of mono‐condensed tridentate Schiff baseligand HL {2‐[1‐(3‐aminopentylimino)ethyl]phenol}. The Schiff base has been freed from the complex by precipitating the NiII as a dimethylglyoximato complex. HL reacts smoothly with Ni(SCN)2·4H2O furnishing the complex [NiL(NCS)] (2) and with CuCl2·2H2O in the presence of NaN3 or NH4SCN producing [CuL(N3)]2 (3) or [CuL(NCS)] (4). On the other hand, upon reaction with Cu(ClO4)2·6H2O and Cu(NO3)2·3H2O, the Schiff base undergoes hydrolysis to yield ternary complexes [Cu(hap)(pn)(H2O)]ClO4 (5) and [Cu(hap)(pn)(H2O)]NO3 (6), respectively (Hhap = o‐hydroxyacetophenone and pn = 1,3‐pentanediamine). The ligand HL undergoes hydrolysis also on reaction with Ni(ClO4)2·6H2O or Ni(NO3)2·6H2O to yield [Ni(hap)2] (7). The structures of the complexes 2, 3, 5, 6, and 7 have been confirmed by single‐crystal X‐ray analysis. In complex 2, NiII possesses square‐planar geometry, being coordinated by the tridentate mono‐negative Schiff base, L and the isothiocyanate group. The coordination environment around CuII in complex 3 is very similar to that in complex 2 but here two units are joined together by end‐on, axial‐equatorial azide bridges to result in a dimer in which the geometry around CuII is square pyramidal. In both 5 and 6, the CuII atoms display the square‐pyramidal environment; the equatorial sites being coordinated by the two amine groups of 1,3‐pentanediamine and two oxygen atoms of o‐hydroxyacetophenone. The axial site is coordinated by a water molecule. Complex 7 is a square‐planar complex with the Ni atom bonded to four oxygen atoms from two hap moieties. The mononuclear units of 2 and dinuclear units of 3 are linked by strong hydrogen bonds to form a one‐dimensional network. The mononuclear units of 5 and 6 are joined together to form a dimer by very strong hydrogen bonds through the coordinated water molecule. These dimers are further involved in hydrogen bonding with the respective counteranions to form 2‐D net‐like open frameworks. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Poly[diaquabis(μ2-azido-κ2N1:N1)bis(μ3-1-oxoisonicotinato-κ3O:O′:O′′)dicadmium(II)

In the title compound, [Cd2(C6H4NO3)2(N3)2(H2O)2]n, one CdII atom is located on an inversion center and is coordinated by four O atoms from four bridging 1-oxoisonicotinate ligands and two N atoms of two bridging azide ligands in a slightly distorted octa­hedral geometry. The other CdII atom, also lying on an inversion center, is coordinated by four O atoms from two bridging 1-oxoisonicotinate ligands and two water mol­ecules and two N atoms of two bridging azide ligands in a slightly distorted octa­hedral geometry. The Cd atoms are connected via the 1-oxoisonicotinate and azide ligands into a two-dimensional coordination network. The crystal structure involves O—H⋯N and O—H⋯O hydrogen bonds.

Three New Cu−Azido Polymers and Their Systematic Interconversion: Role of the Amount of the Blocking Amine on the Structural Diversity and Magnetic Behavior

Three new coordination polymers [Cu5(N3)10(en)2]n (1), [Cu6(N3)12(en)4]n (2), and [Cu4(N3)8(en)4]n (3) have been synthesized in a controlled manner by treatment of a 1:2 mixture of Cu(NO3)2 and NaN3 with varying amount of ethylenediamine (en). Single-crystal structure analyses clearly indicated that the puckered Cu4 biscubane unit in 1 gradually opens to a slightly more open Cu4 macrocyclic unit in 2 when more en approaches to the Cu4 core. Upon addition of further en, an open Cu4 linear secondary building unit was obtained in complex 3. Complex 1 contains four different kinds of bridging modes of the azide anion and is a complicated 3D polymer. Similarly, complexes 2 and 3 are 3D and 2D polymers, respectively, containing three different kinds of bridging azides. Complex 3 contains two very rare cis end-to-end (EE) and single-end-on (EO) azido modes. Structural transformation from 1 to 3 was monitored and explained qualitatively. Variable-temperature magnetic studies in the temperature range of 300-2 K reveal the existence of dominant ferromagnetic behavior in all the three cases with a metamagnetic-type behavior in complex 1 with the critical field of transition at 0.8 T. The purity of all the complexes were established by elemental analyses, as well as by the powder XRD patterns that matched well with the expected patterns from the single-crystal structure analysis.

Synthesis, crystal structures, and antimicrobial activity of a pair of isostructural dinuclear copper(II) complexes derived from 4-nitro-2-[(2-diethylaminoethylimino)methyl]phenol

A pair of isostructural azido- or thiocyanato-bridged centrosymmetric dinuclear copper(II) complexes, [Cu2L2(μ1,3-N3)2] (1) and [Cu2L2(μ1,3-NCS)2] (2), derived from the Schiff base ligand 4-nitro-2-[(2-diethylaminoethylimino)methyl]phenol (HL), have been synthesized and characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Each Cu atom in the complexes is five-coordinate in a square pyramidal geometry by one O and two N atoms of one Schiff base ligand, and by two terminal donor atoms from two bridging azide or thiocyanate ligands. Both the azide and thiocyanate ligands adopt end-to-end bridging mode in the complexes. The distance between the two copper atoms is 5.205(2) A for (1) and 5.515(2) A for (2). The antimicrobial activity of the complexes has been tested.