Metal-organic frameworks incorporating Cu3(mu3-OH) clusters

Interaction of 4,4-bi(1,2,4-triazole) (btr) with copper(II) chloride (bromide) in aqueous or aqueous alcohol media led to a series of coordination polymers featuring the formation of mu 3-hydroxotricopper(II) clusters and their integration into 3D frameworks. These unprecedented structures originate in the propagation of trigonal hydroxotricopper(II) clusters bridged by tri- or tetradentate organic ligands. Complex [{Cu3(mu3-OH)}{Cu3(mu3-O)}(mu4-btr)3(H2O)4(OH)2Cl6]Cl.0.5H2O adopts a structure of SrSi2 topology, with eight-fold interpenetration of the coordination frameworks. The structure of [{Cu3(mu3-OH)}2(mu3-btr)6(mu4-btr)(mu-X)X4]X5.nH2O (X = Br, n = 6; X = Cl, n = 8) involves 2D coordination layers [{Cu3(mu3-OH)}(mu3-btr)3]n with an exceptional (3,6)-net topology, which are cross-linked by tetradentate btr ligands and bridging chloride (bromide) ions.     

Syntheses, structures, and magnetic properties of unusual nonlinear polynuclear copper(II) complexes containing derivatives of 1,2,4-triazole and pivalate ligands

Novel polynuclear Cu(II) complexes containing derivatives of 1,2,4-trizaole and pivalate ligands, [Cu(3)(mu(3)-OH)(mu-adetrz)(2)(piv)(5)(H(2)O)].6.5H(2)O (1) (adetrz = 4-amino-3,5-diethyl-1,2,4-triazole, piv = pivalate), [Cu(4)(mu(3)-OH)(2)(mu-atrz)(2)(mu-piv)(4)(piv)(2)].2MeOH.H(2)O (2) (atrz = 4-amino-1,2,4-triazole), [Cu(4)(mu(3)-OH)(2)(mu-tbtrz)(2)(mu-piv)(2)(piv)(4)].4H(2)O (3) (tbtrz = 4-tert-butyl-1,2,4-trizaole), and [Cu(4)(mu(3)-O)(2)(mu-admtrz)(4)(admtrz)(2)(mu-piv)(2)(piv)(2)].2[Cu(2)(mu-H(2)O)(mu-admtrz)(piv)(4)].13H(2)O [4 = 4a.2(4b).13H(2)O; admtrz = 4-amino-3,5-dimethyl-1,2,4-triazole], have been prepared and structurally characterized. 1 is an asymmetrical triangular complex containing a [Cu(3)(mu(3)-OH)] core with two Cu---Cu edges spanned by bridging adetrz ligands. 2, 3, and 4a are novel tetranuclear compounds containing a [Cu(4)(mu(3)-O)(2)] or [Cu(4)(mu(3)-OH)(2)] core with Cu---Cu edges spanned by bridging 1,2,4-triazole or pivalate ligands. 4b is a dinuclear compound with one admtrz and one water bridge, and it is the first dinuclear Cu(II) triazole complex with one bridging water molecule. 1 is one of few reported triangular Cu(II) complexes with derivatives of 1,2,4-triazole, while 2, 3, and 4a are the first group of the nonlinear tetranuclear Cu(II) compounds with derivatives of 1,2,4-triazole. Variable-temperature magnetic susceptibility studies on the powder samples of 1-3 reveal the overall antiferromagnetic coupling between Cu(II) ions with J values of -55.6 to -12.8 cm(-1) (1), -216.4 to 0 cm(-1) (2), and -259.8 to 4.8 cm(-1) (3).     

Self-assembly and anion-exchange properties of a discrete cage and 3D coordination networks based on cage structures

By using tridentate ligand 4-(3-pyridinyl)-1,2,4-triazole (pytrz), cage-like complexes of {[Cu(mu2-pytrz)2](ClO4)(SO4)0.5C2H5OH.0.25 H2O}6 (1), {[Cu3(mu3-pytrz)4(mu2-Cl)2(H2O)2](ClO4)2Cl(2).2 H2O}n (2), and {[Cu3(mu3-pytrz)3(mu3-O)(H2O)3](ClO4)2.5(BF4)(1.5)5.25 H2O}n (3) have been synthesized with different copper(II) salts. Complex 1 represents the second example of a M6L12 metal-organic octahedron with an overall Th symmetry. Complex 2 is constructed from a 3(8) cage-building unit (CBU) and each CBU connects six neighboring cages to give the first 3D metal-organic framework (MOF) based on octahedral M6L12. Complex 3 is built from Cu24(pytrz)12 CBUs with the trinuclear copper clusters serving as second building units (SBUs) and decorating each corner of the M24L12 polyhedron. The Cu24(pytrz)12 building unit is linked by extra ligands to give an extended 3D framework that has the formula Cu24(pytrz)24 and possesses a CaB6 topology. The mixed anions ClO4- and BF4- in 3 are both included in the inner cavity of the cage and can be completely exchanged by ClO4- through the open windows of the cage, as evidenced by the crystal structure of the 3D MOF {[Cu3(mu3-pytrz)3(mu3-O)(H2O)3](ClO4)(4)4.5 H2O}n (4). Complex 4 can also be synthesized when employing 1 as a precursor in an extensive study of the anion-exchange reaction. This represents the first successful conversion of a discrete cage into a 3D coordination network based on a cage structure. Complex 2 remains invariable during anion-exchange reactions because uncoordinated Cl- ions are located in the comparatively small inner cavity.     

Synthesis, crystal structure, and characterization of new tetranuclear Ag(I) complexes with triazole bridges

The self-assembly of Ag(I) ions with 3,5-dimethyl-4-amino-1,2,4-triazole (L1) and 4-salicylideneamino-1,2,4-triazole (L2) gave two novel complexes, [Ag4(mu2-L1)6][Ag4(mu2-L1)6(CH3CN)2](ClO4)8.2H2O (1) and [Ag4(mu2-L2)6(CH3CN)2](AsF6)4.2H2O (2), both of which contain tetranuclearic clusters constructed via Ag(I) ions and six N1,N2-bridged triazoles with a Ag4N12 core. When 4-(6-amino-2-pyridyl)-1,2,4-triazole (L3) was employed, {[Ag4(mu2-L3)4(mu3-L3)2](CF3SO3)4.H2O}n (3), {[Ag4(mu2-L3)4(mu3-L3)2](ClO4)4}n (4), and {[Ag4(mu2-L3)2(mu3-L3)4](PF6)4.CH3CN.0.75H2O}n (5) were isolated. 3 and 4 are 1D polymers, while 5 is a 2D polymer. 1D and 2D coordination polymers are constructed via the self-assembly of Ag4N12 cores as secondary building units (SBUs). The connection of these SBUs can be represented as a ladderlike structure for 1D polymers and a 4.8(2) net for 2D polymers. Electrospray ionization mass spectrometry measurements and NMR (1H and 13C) studies demonstrate that the tetranuclear SBU retains its integrity and the coordination polymers decompose into the tetranuclear Ag4N12 core in solution. 2 exhibits blue emission in the solid state and green emission in solution at ambient temperature. Strong blue fluorescence for complexes 3-5 in the solid state can be assigned to the intraligand fluorescent emission.     

Hydrothermal synthesis and structure of a three-dimensional cobalt(II) triazolate magnet

The reaction of CoCl2.6H2O, 1,2,4-triazole, and H(2)O at 200 degrees C for 96 h yields purple rods of [Co2(trz)3Cl] (1; trz = 1,2,4-triazolate) in 90% yield. The structure of 1 consists of {Co(trz)3}n(n-) chains of Co(II) sites linked through tetrahedral sites of {CoN(3)Cl} geometry into a three-dimensional framework. The competing antiferromagnetic interactions of the octahedral and tetrahedral Co(II) centers result in weak ferromagnetic behavior below Tc = 9 K.     

The first nitro-substituted heteroscorpionate ligand

The new dihydridobis(3-nitro-1,2,4-triazolyl)borate ligand, [H2B(tzNO2)2]-, has been synthesized in dimethylacetamide solution, using 3-nitro-1,2,4-triazole and KBH4 through careful temperature control, and characterized as its potassium salt. The zinc(II) and cadmium(II) complexes, {M[H2B(tzNO2)2]Cl(H2O)2}, have been prepared by metathesis of [H2B(tzNO2)2]K with ZnCl2 and CdCl2, respectively. The complexes likely contain a metal core in which the ligand is coordinated to the metal ions in the K2-N,N' or K4-N,N',O,O' fashion. A single-crystal structural characterization is reported for the potassium dihydrobis(3-nitro-1,2,4-triazolyl)borate. The potassium salt is polymeric and shows several K...N and K...O interactions.     

A copper-based coordination polymer formed through synergistic bridging of 1,2,4-triazole and acetate anions: synthesis,crystal structure and magnetic properties

Transition Metal Chemistry - A Cu(II) coordination polymer, [Cu2(pztrz)2(μ-CH3COO)(CH3COO)]·3H2O (1), derived from mono-substituted 1,2,4-triazole derivative 3-(pyrazinyl)-1,2,4-triazole...     

Synthesis and Crystal Structure of Copper(Ⅱ) Compound with Didentate Schiff-base Ligand

1INTRODUCTIONTransitionmetalcomplexesofSchiff-baseligandswhichbindtwoormoremetalcentersincloseproximityareimportantaspotentialcatalysts[1]andasmodelsforanumberofmetalloproteins[2]duetotheopportunitytheyprovidefortheinvesti-gationofmagneticinteractions.The…     

噻吩和吡啶取代三芳基三唑的两个铜配合物的合成与晶体结构

分别以3-(2-吡啶基)-4-苯基-5-(2-噻吩基)-1,2,4-三氮唑(L1)和3-(2-吡啶基)-4-(4-氯苯基)-5-(2-噻吩基)-1,2,4-三氮唑(L2)作为配体,合成了2个新的单核铜配合物:trans-[Cu(L1)2(MeOH)2](ClO4)2(1)和trans-[Cu(L2)2(ClO4)2]·...     

X-ray crystal structures, electron paramagnetic resonance, and magnetic studies on strongly antiferromagnetically coupled mixed mu-hydroxide-mu-N(1),N(2)-triazole-bridged one dimensional linear chain copper(II) complexes

Four new metal-organic polymeric complexes, {[Cu(mu-OH)(mu-ClPhtrz)][(H 2O)(BF 4)]} n ( 1), {[Cu(mu-OH)(mu-BrPhtrz)][(H 2O)(BF 4)]} n ( 2), {[Cu(mu-OH)(mu-ClPhtrz)(H 2O)](NO 3)} n ( 3), and {[Cu(mu-OH)(mu-BrPhtrz)(H 2O)](NO 3)} n ( 4) (ClPhtrz = N-[( E)-(4-chlorophenyl)methylidene]-4 H-1,2,4-triazol-4-amine; BrPhtrz = N-[( E)-(4-bromophenyl)methylidene]-4 H-1,2,4-triazol-4-amine), were synthesized in a reaction of substituted 1,2,4-triazole and various copper(II) salts in water/acetonitrile solutions. The structures of 1- 4 were characterized by single-crystal X-ray diffraction analysis. The Cu(II) ions are linked both by single N (1), N (2)-1,2,4-triazole and hydroxide bridges yielding one dimensional (1D) linear chain polymers. The tetragonally distorted octahedral geometry of copper atoms is completed alternately by two water and two BF 4 (-) anion molecules in 1 and 2 but solely by two water molecules in 3 and 4. Magnetic properties of all complexes were studied by variable temperature magnetic susceptibility measurements. The Cu(II) ions are strongly antiferromagnetically coupled with J = -419(1) cm (-1) ( 1), -412(2) cm (-1) ( 2), -391(3) cm (-1) ( 3), and -608(2) cm (-1) ( 4) (based on the Hamiltonian H = - J[ summation operator S i . S i+ 1]). The nature and the magnitude of the antiferromagnetic exchange were discussed on the basis of complementarity/countercomplementarity of the two competing bridges.     

Synthesis of a series of 4-pyridyl-1,2,4-triazole-containing cadmium(II) luminescent complexes

Using two 4-substitued triazole ligands, 4-(pyrid-2-yl)-1,2,4-triazole (L(1)) and 4-(pyrid-3-yl)-1,2,4-triazole (L(2)), a series of novel triazole-cadmium(II) complexes varying from zero- to three-dimensional have been prepared and their crystal structures determined via single-crystal X-ray diffraction. [Cd(2)(micro(2)-L(1))(3)(L(1))(2)(NO(3))(mu(2)-NO(3))(H(2)O)(2)](NO(3))(2).1.75H(2)O (1) is a binuclear complex containing bidendate, monodedate and free nitrate anions. When the bridging anions SCN(-) and dca (dca = N(CN)(2)(-)) were added to the reaction system of 1, one-dimensional (1D) [Cd(L(1))(2)(NCS)(2)](n) (2) and two-dimensional (2D) [Cd(L(1))(2)(dca)(2)](n) (3) were isolated, respectively. When L(2) instead of L(1) was used, [Cd(L(2))(2)(NCS)(2)(H(2)O)(2)] (4) and 1D [Cd(L(2))(2)(dca)(2)](n) (5) were obtained. When the ratio of Cd to L(2) was changed from 1:2 to 1:1 in the reaction system of 5, three-dimensional (3D) {[Cd(3)(micro(2)-L(2))(3)(dca)(6)].0.75H(2)O}(n) (6) with 1D microporous channels along the a direction was isolated. Further investigations on other Cd(ii) salts and the L(2) ligand in a Cd to L(2) ratio of 1:1, an unexpected complex [Cd(mu(2)-L(2))(mu(3)-SO(4))(H(2)O)](n) (7) with a 3D open framework was obtained. All of the complexes exhibit strong blue fluorescence emission bands in the solid state at ambient temperature, of which the excitation and emission maxima are red-shifted to longer wavelength as compared to those in water. Powder X-ray diffraction and thermal studies were used to investigate the bulk nature of the 3D coordination polymers 6 and 7.     

SYNTHESIS,CRYSTAL STRUCTURE AND ELECTROCHEMISTRY PROPERTIES OF Cu-COMPOUND BY RIGID LIGAND

Journal of Structural Chemistry - A new novel Cu(II) compound formulated as Cu(C4N6H4)2Cl2 (1) (C4N6H4 = 1H-3,4′-bi-1,2,4-triazole) is successfully synthesized by a...     

High and low spin mononuclear and dinuclear iron(II) complexes of 4-amino and 4-pyrrolyl-3,5-di(2-pyridyl)-4H-1,2,4-triazoles

The first dinuclear iron(II) complexes of any 4-substituted 3,5-di(2-pyridyl)-4H-1,2,4-triazole ligands, [Fe(II)2(adpt)2(H2O)1.5(CH3CN)2.5](BF4)4 and [Fe(II)2(pldpt)2(H2O)2(CH3CN)2](BF4)4, are presented [where adpt is 4-amino-3,5-di(2-pyridyl)-4H-1,2,4-triazole and pldpt is 4-pyrrolyl-3,5-di(2-pyridyl)-4H-1,2,4-triazole]. Both dinuclear complexes feature doubly triazole bridged iron(II) centers that are found to be [high spin-high spin] at all temperatures, 4-300 K, and to exhibit weak antiferromagnetic coupling. In the analogous monometallic complexes, [Fe(II)(Rdpt)2(X)2](n+), the spin state of the iron(II) center was controlled by appropriate selection of the axial ligands X. Specifically, both of the chloride complexes, [Fe(II)(adpt)2(Cl)2] x 2 MeOH and [Fe(II)(pldpt)2(Cl)2] x 2 MeOH x H2O, were found to be high spin whereas the pyridine adduct [Fe(II)(adpt)2(py)2](BF4)2 was low spin. Attempts to prepare [Fe(II)(pldpt)2(py)2](BF4)2 and the dinuclear analogues [Fe(II)2(Rdpt)2(py)4](BF4)4 failed, illustrating the significant challenges faced in attempts to develop control over the nature of the product obtained from reactions of iron(II) and these bis-bidentate ligands.     

Antisymmetric exchange in triangular tricopper(II) complexes: correlation among structural, magnetic, and electron paramagnetic resonance parameters

Two new trinuclear copper(II) complexes, [Cu(3)(μ(3)-OH)(daat)(Hdat)(2)(ClO(4))(2)(H(2)O)(3)](ClO(4))(2)·2H(2)O (1) and [Cu(3)(μ(3)-OH)(aaat)(3)(H(2)O)(3)](ClO(4))(2)·3H(2)O (2) (daat = 3,5-diacetylamino-1,2,4-triazolate, Hdat = 3,5-diamino-1,2,4-triazole, and aaat = 3-acetylamino-5-amino-1,2,4-triazolate), have been prepared from 1,2,4-triazole derivatives and structurally characterized by X-ray crystallography. The structures of 1 and 2 consist of cationic trinuclear copper(II) complexes with a Cu(3)OH core held by three N,N-triazole bridges between each pair of copper(II) atoms. The copper atoms are five-coordinate with distorted square-pyramidal geometries. The magnetic properties of 1 and 2 and those of five other related 1,2,4-triazolato tricopper(II) complexes with the same triangular structure (3-7) (whose crystal structures were already reported) have been investigated in the temperature range of 1.9-300 K. The formulas of 3-7 are [Cu(3)(μ(3)-OH)(aaat)(3)(H(2)O)(3)](NO(3))(2)·H(2)O (3), {[Cu(3)(μ(3)-OH)(aat)(3)(μ(3)-SO(4))]·6H(2)O}(n) (4), and [Cu(3)(μ(3)-OH)(aat)(3)A(H(2)O)(2)]A·xH(2)O [A = NO(3)(-) (5), CF(3)SO(3)(-) (6), or ClO(4)(-) (7); x = 0 or 2] (aat =3-acetylamino-1,2,4-triazolate). The magnetic and electron paramagnetic resonance (EPR) data have been analyzed by using the following isotropic and antisymmetric exchange Hamiltonian: H = -J[S(1)S(2) + S(2)S(3)] - j[S(1)S(3)] + G[S(1) × S(2) + S(2) × S(3) + S(1) × S(3)]. 1-7 exhibit strong antiferromagnetic coupling (values for both -J and -j in the range of 210-142 cm(-1)) and antisymmetric exchange (G varying from to 27 to 36 cm(-1)). At low temperatures, their EPR spectra display high-field (g < 2.0) signals indicating that the triangles present symmetry lower than equilateral and that the antisymmetric exchange is operative. A magneto-structural study showing a lineal correlation between the Cu-O-Cu angle of the Cu(3)OH core and the isotropic exchange parameters (J and j) has been conducted. Moreover, a model based on Moriya's theory that allows the prediction of the occurrence of antisymmetric exchange in the tricopper(II) triangles, via analysis of the overlap between the ground and excited states of the local Cu(II) ions, has been proposed. In addition, analytical expressions for evaluating both the isotropic and antisymmetric exchange parameters from the experimental magnetic susceptibility data of triangular complexes with local spins (S) of (1)/(2), (3)/(2), or (5)/(2) have been purposely derived. Finally, the magnetic and EPR results of this work are discussed and compared with those of other tricopper(II) triangles reported in the literature.     

In situ solvothermal generation of 1,2,4-triazolates and related compounds from organonitrile and hydrazine hydrate: a mechanism study

The facile and effective one-pot solvothermal syntheses of 3,5-disubstituted 1,2,4-triazole and its derivatives (substituted group = alkyl, aryl, and pyridyl) through cyclocondensations of organonitriles and hydrazine hydrate in the absence/presence of metal salts have been established. By control of the solvothermal conditions and/or the addition of counteranions, different intermediates and final products were derived from various organonitriles, in which an intermediate N,N'-bis(picolinamide)azine (H4bpa) has been successfully trapped in its neutral manganese(II) complexes. A systematical study shows that, after the initial formation of 2-pyridylamidrazone from 2-cyanopyridine and hydrazine, two reaction paths are involved in the formation of 1,2,4-triazoles: via the formation of 3,6-bis(2-pyridyl)-1,2-dihydro-1,2,4,5-tetrazine and H4bpa as intermediates. The tetrazine and H4bpa paths are preferred in the absence and presence of metal ions, respectively. In the presence of metal ions, metal ion binding can stabilize the tautomers, enhance the nucleophilic reactivity of the imino C atom, and inhibit the tautomerization of H4bpa, hence leading to the formation of 1,2,4-triazolates or H4bpa in complexed forms. The in situ cyclocondensation reactions of 2-pyridylamidrazone and carboxylate into asymmetric 3,5-disubstituted 1,2,4-triazolates under solvothermal conditions have also been observed for the first time. Crystal structures of the crystalline metal complexes have been obtained, including dinuclear [Mn2(bpt)2Cl2(H2O)2] (1) and [Mn2(bpt)2(SCN)2(H2O)2] (3; Hbpt = 3,5-bis(2-pyridyl)-4H-1,2,4-triazole), tetranuclear [Mn4(H3bpa)2(mpt)4(N3)2].2H2O (5; Hmpt = 3-methyl-5-(2-pyridyl)-1H-1,2,4-triazole), [Mn4(H3bpa)2(pt)4(N3)2].2C2H5OH (6; Hpt = 5-(2-pyridyl)-1H-1,2,4-triazole), and [Mn4(H3bpa)4(SCN)4].2C2H5OH (7), as well as helical [Cu(bpt)] (2). Among them, 7 is the first example of a neutral tetranuclear [2 x 2] grid manganese(II) complex. Both 5 and 7 exhibit antiferromagnetic interactions.     

Novel triazole-bridged cadmium coordination polymers varying from zero- to three-dimensionality

Cadmium salts with different triazole ligands have led to a series of novel triazole-cadmium compounds varying from zero- to three-dimensionality. [Cd(2)(deatrz)(2)(H(2)O)Br(4)] (1) (deatrz = 3,5-diethyl-4-amino-1,2,4-triazole) is a zero-dimensional complex which uses a triazole ligand together with micro-OH(2) as bridges to form a 1D chain via hydrogen-bonding contacts. [[Cd(3)(deatrz)(2)Cl(6)(H(2)O)(2)].2H(2)O](n) (2), [[Cd(dmtrz)Cl(2)].1.5H(2)O](n)(3) (dmtrz = 3,5-dimethyl-1,2,4-triazole), and [[Cd(3)(deatrz)(4)Cl(2)(SCN)(4)].2H(2)O](n)(4) are polymeric 1D chains. 2 and 4 were constructed via trinuclear cadmium units bridged by triazole ligands and chloride atoms, while 3 consists of micro(2)-Cl, micro(3)-Cl, and triazole bridges, cross-linked by hydrogen bonding to give a 3D framework. [[Cd(3)(dmatrz)(4)(SCN)(6)]](n)(5) (dmatrz = 3,5-dimethyl-4-amino-1,2,4-triazole) shows a two-dimensional structure whose fundamental units are trinuclear metal cations bridged via triazole ligands. The complex [[Cd(dmtrz)(SCN)(2)]](n)(6) is the first three-dimensional example in N1,N2-didentate-bridged triazole-metal compounds. Six complexes exhibit six types of bridging modes of N1,N2-triazole in combination with single-atom bridges. 2, 4, and 5 are the unprecedented examples of polymeric chains and planes constructed via trinuclear metal ion clusters, whereas 3 is the first example of the micro(3)-Cl bridging mode in triazole-metal complexes. We have briefly discussed the variety of dimensionalities based on the tuning of different organic ligands and anions.     

Synthesis and Crystal Structure of Copper(Ⅱ) Compound with Didentate Schiff-base Ligand

The title complex [Cu(L)2] (HL=4-salicylideneamino-3,5-dimethanol-1,2,4-triazole) was synthesized by the reaction of Cu(CH3COO)2·2H2O with 4-salicylideneamino-3,5-dimethanol- 1,2,4-triazole in the methanol. The single-crystal X-ray study reveals that the compound crystallizes in monoclinic, space group P21/n with a = 11.746(5), b = 8.145(3), c = 12.786(5)A,β = 106.64(1)°, V = 1172(1)A3, Z = 2, Dc = 1.581 g/cm3, μ= 0.989 mm-1, F(000) = 574, C22H22Cu- N8O6, Mr = 558.02, T = 293(2) K, R = 0.0394 and Rw = 0.0835 for 2376 observed reflections with I > 2σ(I). The complex comprises a four-coordinated copper(Ⅱ) center, with an N2O2 planar coordi- nation environment. The molecules are connected by hydrogen bonds to form one-dimensional chains which are further linked to form a two-dimensional plane.     

Two Cu(II) coordination polymers based on benzene-1,3,5-tricarboxylate and 1,2,4-triazolide ligands: their crystal structures and application of nanoparticles in anti-esophageal cancer activity evaluation

Structural Chemistry - By reaction of 1,2,4-triazole (Htrz) and 1,3,5-benzenetricarboxylic acid (H3btc) with copper salts under hydrothermal conditions, two new mixed-ligand Cu(II)-coordination...     

Synthesis and characterization of a 3D coordination polymer based on trinuclear triangular CuII as secondary building units

The hydrothermal reaction of Cu(II) salts with 1,2,4-triazole (Htrz) in aqueous ammonia yielded a novel metal-organic framework {[Cu3(mu3-O)(mu3-trz)3(OH)(H2O)6]}n (1), which was characterized by single-crystal X-ray diffraction, X-ray powder diffraction, thermogravimetric analysis, IR, and variable-temperature magnetic susceptibility. It crystallizes in cubic, space group Fd3c with a = 24.644(3) A, V = 14967(3) A(3), and Z = 96. Its framework is the first 3D structure using coordinative interactions constructed via trinuclear triangular Cu(II) secondary building units, in which both Cu(II) ions and trz ligands act as three-connected nodes to form a 6.8(2) net. An overall antiferromagnetic behavior was found in the compound.     

Copper(II) mediated anion dependent formation of Schiff base complexes

A tetranuclear mixed ligand copper(II) complex of a pyrazole containing Schiff base and a hydroxyhexahydropyrimidylpyrazole and copper(II) and nickel(II) complexes of the Schiff base having N-donor atoms have been investigated. A 2 equiv amount of 5-methyl-3-formylpyrazole (MPA) and 2 equiv of 1,3-diamino-2-propanol (1,3-DAP) on reaction with 1 equiv of copper(II) nitrate produce an unusual tetranuclear mixed ligand complex [Cu4(L1)2(L2)2(NO3)2] (1), where H2L1 = 1,3-bis(5-methyl-3-formylpyrazolylmethinimino)propane-2-ol and HL2 = 5-methyl-3-(5-hydroxyhexahydro-2-pyrimidyl)pyrazole. In contrast, a similar reaction with nickel(II) nitrate leads to the formation of a hygroscopic intractable material. On the other hand, the reaction involving 2 equiv of MPA and 1 equiv each of 1,3-DAP and various copper(II) salts gives rise to two types of products, viz. [Cu(T3-porphyrinogen)(H2O)]X2 (X = ClO4, NO3, BF4 (2)) (T3-porphyrinogen = 1,6,11,16-tetraza-5,10,15,20-tetrahydroxy-2,7,12,17-tetramethylporphyrinogen) and [Cu(H2L1)X]X x H2O (X = Cl (3), Br (4)). The same reaction carried out with nickel(II) salts also produces two types of compounds [Ni(H2L1)(H2O)2]X2 [X = ClO4 (5), NO3 (6), BF4 (7)] and [Ni(H2L1)X2] x H2O [X = Cl (8), Br (9)]. Among the above species 1, 3, and 5 are crystallographically characterized. In 1, all four copper atoms are in distorted square pyramidal geometry with N4O chromophore around two terminal copper atoms and N5 chromophore around two inner copper atoms. In 3, the copper atom is also in distorted square pyramidal geometry with N4Cl chromophore. The nickel atom in 5 is in a distorted octahedral geometry with N4O2 chromophore, where the metal atom is slightly pulled toward one of the axial coordinated water molecules. Variable-temperature (300 to 2 K) magnetic susceptibility measurements have been carried out for complex 1. The separations between the metal centers, viz., Cu(1)...Cu(2), Cu(2)...Cu(2)A, and Cu(2)A...Cu(1)A are 3.858, 3.89, and 3.858 A, respectively. The overall magnetic behavior is consistent with strong antiferromagnetic interactions between the spin centers. The exchange coupling constants between Cu(1)...Cu(2) and Cu(2)...Cu(2A) centers have turned out to be -305.3 and -400.7 cm(-1), respectively, resulting in a S = 1/2 ground state. The complexes are further characterized by UV-vis, IR, electron paramagnetic resonance, and electrochemical studies.