Syntheses, characterization, and magnetic studies of copper(II) complexes with the ligand N,N,N',N'-tetrakis(2-pyridylmethyl)-1,3-benzenediamine (1,3-tpbd) and its phenol derivative 2,6-bis[bis(2-pyridylmethyl)amino]-p-cresol] (2,6-Htpcd)

The copper(II) complexes [Cu(4)(1,3-tpbd)(2)(H(2)O)(4)(NO(3))(4)](n)(NO(3))(4n)·13nH(2)O (1), [Cu(4)(1,3-tpbd)(2)(AsO(4))(ClO(4))(3)(H(2)O)](ClO(4))(2)·2H(2)O·0.5CH(3)OH (2), [Cu(4)(1,3-tpbd)(2)(PO(4))(ClO(4))(3)(H(2)O)](ClO(4))(2)·2H(2)O·0.5CH(3)OH (3), [Cu(2)(1,3-tpbd){(PhO)(2)PO(2)}(2)](2)(ClO(4))(4) (4), and [Cu(2)(1,3-tpbd){(PhO)PO(3)}(2)(H(2)O)(0.69)(CH(3)CN)(0.31)](2)(BPh(4))(4)·Et(2)O·CH(3)CN (5) [1,3-tpbd = N,N,N',N'-tetrakis(2-pyridylmethyl)-1,3-benzenediamine, BPh(4)(-) = tetraphenylborate] were prepared and structurally characterized. Analyses of the magnetic data of 2, 3, 4, and [Cu(2)(2,6-tpcd)(H(2)O)Cl](ClO(4))(2) (6) [2,6-tpcd = 2,6-bis[bis(2-pyridylmethyl)amino]-p-cresolate] show the occurrence of weak antiferromagnetic interactions between the copper(II) ions, the bis-terdentate 1,3-tpbd/2,6-tpcd, μ(4)-XO(4) (X = As and P) μ(1,2)-OPO and μ-O(phenolate) appearing as poor mediators of exchange interactions in this series of compounds. Simple orbital symmetry considerations based on the structural knowledge account for the small magnitude of the magnetic couplings found in these copper(II) compounds.     

Selenadiazolopyridine: a synthon for supramolecular assembly and complexes with metallophilic interactions

The synthesis and characterization of the complexes of Cu(I), Ag(I), Cu(II), and Co(II) ions with 1,2,5-selenadiazolopyridine (psd) is reported. The following complexes have been prepared: [Cu(2)(psd)(3)(CH(3)CN)(2)](2+)2(PF(6)(-)); [(CuCl)(2)(psd)(3)]; [Cu(2)(psd)(6)](2+)2(ClO(4))(-); [Ag(2)(psd)(2)](2+)2(NO(3))(-); [Ag(2)(psd)(2)](2+)2(CF(3)COO)(-); [Cu(psd)(2)(H(2)O)(3)](2+)2(ClO(4))(-)·(psd)(2); [Cu(psd)(4)(H(2)O)](2+)2(ClO(4))(-)·(CHCl(3)); [Cu(psd)(2)(H(2)O)(3)](2+)2(NO(3))(-)·(H(2)O)·(psd)(2), and [Co(psd)(2)(H(2)O)(4)](2+)2(ClO(4))(-)·(psd)(2). The electronic structure of ligand psd, in particular the bond order of Se-N bonds, has been probed by X-ray diffraction, (77)Se NMR, and computational studies. A detailed analysis of the crystal structures of the ligand and the complexes revealed interesting supramolecular assembly. The assembly was further facilitated by the presence of neutral ligands for some complexes (Cu(II) and Co(II)). The molecular structure of the ligand showed that it was present as a dimer in the solid state where the monomers were linked by strong secondary bonding Se···N interactions. The crystal structures of Cu(I) and Ag(I) complexes revealed the dinuclear nature with characteristic metallophilic interactions [M···M] (M = Cu, Ag), while the Cu(II) and Co(II) complexes were mononuclear. The presence of M···M interactions has been further probed by Atoms in Molecules (AIM) calculations. The paramagnetic Cu(II) and Co(II) complexes have been characterized by UV-vis, ESI spectroscopy, and room temperature magnetic measurements.     

Reactions of acetonitrile coordinated to a nitrosylruthenium complex with H2O or CH(3)OH under mild conditions: structural characterization of imido-type complexes

The reaction of cis-[Ru(NO)(CH(3)CN)(bpy)(2)](3+) (bpy = 2,2'-bipyridine) in H(2)O at room temperature proceeded to afford two new nitrosylruthenium complexes. These complexes have been identified as nitrosylruthenium complexes containing the N-bound methylcarboxyimidato ligand, cis-[Ru(NO)(NH=C(O)CH(3))(bpy)(2)](2+), and methylcarboxyimido acid ligand, cis-[Ru(NO)(NH=C(OH)CH(3))(bpy)(2)](3+), formed by an electrophilic reaction at the nitrile carbon of the acetonitrile coordinated to the ruthenium ion. The X-ray structure analysis on a single crystal obtained from CH(3)CN-H(2)O solution of cis-[Ru(NO)(NH=C(O)CH(3))(bpy)(2)](PF(6))(3) has been performed: C(22)H(20.5)N(6)O(2)P(2.5)F(15)Ru, orthorhombic, Pccn, a = 15.966(1) A, b = 31.839(1) A, c = 11.707(1) A, V = 5950.8(4) A(3), and Z = 8. The structural results revealed that the single crystal consisted of 1:1 mixture of cis-[Ru(NO)(NH=C(O)CH(3))(bpy)(2)](2+) and cis-[Ru(NO)(NH=C(OH)CH(3))(bpy)(2)](3+) and the structural formula of this single crystal was thus [Ru(NO)(NH=C(OH(0.5))CH(3))(bpy)(2)](PF(6))(2.5). The reaction of cis-[Ru(NO)(CH(3)CN)(bpy)(2)](3+) in dry CH(3)OH-CH(3)CN at room temperature afforded a nitrosylruthenium complex containing the methyl methylcarboxyimidate ligand, cis-[Ru(NO)(NH=C(OCH(3))CH(3))(bpy)(2)](3+). The structure has been determined by X-ray structure analysis: C(25)H(29)N(8)O(18)Cl(3)Ru, monoclinic, P2(1)/c, a = 13.129(1) A, b = 17.053(1) A, c = 15.711(1) A, beta = 90.876(5) degrees, V = 3517.3(4) A(3), and Z = 4.     

Versatility of 2,6-diacetylpyridine (dap) hydrazones in generating varied molecular architectures: synthesis and structural characterization of a binuclear double helical Zn(II) complex and a Mn(II) coordination polymer

A binuclear complex of Zn(ii) with formula [Zn(dap(A)(2))](2).2.25DMF (.2.25DMF) and a Mn(ii) coordination polymer with formula [Mn(3)(dap(In)(2))(3)(H(2)O)(2).2DMSO](n) (.2DMSO)(n) have been prepared and structurally characterized [dap(A)(2) = dideprotonated form of 2,6-diacetylpyridine bis(anthraniloyl hydrazone); dap(In)(2) = doubly deprotonated form of 2,6-diacetylpyridine bis(isonicotinoyl hydrazone)]. In the Zn(ii) complex the molecular units are double helical, with the Zn(ii) ions in a square pyramidal environment. The Mn(ii) complex on the other hand is a coordination polymer containing two different types of hepta-coordinated Mn(ii) ions, which differ in their axial ligands. The magnetic properties of the Mn(ii) complex, along with those of a double helical pyridine bridged binuclear Ni(ii) complex, earlier synthesized by us, are also reported. The ability of the 2,6-diacetylpyridine bis(aroyl hydrazone) ligands to form double helical complexes is analyzed in terms of the conformational flexibility of the ligands. The differences in the magnetic properties of the micro-N bridged binuclear complexes formed by 1,1 azido N-bridging ligands, and pyridine N-bridging ligands, is analyzed with the help of EHMO calculations.     

Di- and tetra-nuclear copper(II), nickel(II), and cobalt(II) complexes of four bis-tetradentate triazole-based ligands: synthesis, structure, and magnetic properties

Four bis-tetradentate N(4)-substituted-3,5-{bis[bis-N-(2-pyridinemethyl)]aminomethyl}-4H-1,2,4-triazole ligands, L(Tz1)-L(Tz4), differing only in the triazole N(4) substituent R (where R is amino, pyrrolyl, phenyl, or 4-tertbutylphenyl, respectively) have been synthesized, characterized, and reacted with M(II)(BF(4))(2)·6H(2)O (M(II) = Cu, Ni or Co) and Co(SCN)(2). Experiments using all 16 possible combinations of metal salt and L(TzR) were carried out: 14 pure complexes were obtained, 11 of which are dinuclear, while the other three are tetranuclear. The dinuclear complexes include two copper(II) complexes, [Cu(II)(2)(L(Tz2))(H(2)O)(4)](BF(4))(4) (2), [Cu(II)(2)(L(Tz4))(BF(4))(2)](BF(4))(2) (4); two nickel(II) complexes, [Ni(II)(2)(L(Tz1))(H(2)O)(3)(CH(3)CN)](BF(4))(4)·0.5(CH(3)CN) (5) and [Ni(II)(2)(L(Tz4))(H(2)O)(4)](BF(4))(4)·H(2)O (8); and seven cobalt(II) complexes, [Co(II)(2)(L(Tz1))(μ-BF(4))](BF(4))(3)·H(2)O (9), [Co(II)(2)(L(Tz2))(μ-BF(4))](BF(4))(3)·2H(2)O (10), [Co(II)(2)(L(Tz3))(H(2)O)(2)](BF(4))(4) (11), [Co(II)(2)(L(Tz4))(μ-BF(4))](BF(4))(3)·3H(2)O (12), [Co(II)(2)(L(Tz1))(SCN)(4)]·3H(2)O (13), [Co(II)(2)(L(Tz2))(SCN)(4)]·2H(2)O (14), and [Co(II)(2)(L(Tz3))(SCN)(4)]·H(2)O (15). The tetranuclear complexes are [Cu(II)(4)(L(Tz1))(2)(H(2)O)(2)(BF(4))(2)](BF(4))(6) (1), [Cu(II)(4)(L(Tz3))(2)(H(2)O)(2)(μ-F)(2)](BF(4))(6)·0.5H(2)O (3), and [Ni(II)(4)(L(Tz3))(2)(H(2)O)(4)(μ-F(2))](BF(4))(6)·6.5H(2)O (7). Single crystal X-ray structure determinations revealed different solvent content from that found by microanalysis of the bulk sample after drying under a vacuum and confirmed that 5', 8', 9', 11', 12', and 15' are dinuclear while 1' and 7' are tetranuclear. As expected, magnetic measurements showed that weak antiferromagnetic intracomplex interactions are present in 1, 2, 4, 7, and 8, stabilizing a singlet spin ground state. All seven of the dinuclear cobalt(II) complexes, 9-15, have similar magnetic behavior and remain in the [HS-HS] state between 300 and 1.8 K.     

New coordination polymers with extended arm cyclotriguaiacyclene ligands: 1D chains, and interpenetrating or polycatenating 2D (4(2).6(2))(4.6(2))2 networks

A series of new 1D chain and 2D coordination polymers with cyclotriguaiacylene-type ligands are reported. A zig-zag 1D coordination chain is found in complex [Cd(2)(4ph4py)(NO(3))(3)(H(2)O)(2)(DMA)(2)]·(NO(3))·(DMA)(4), where 4ph4py = tris[4-(4-pyridyl)benzoyl]-cyclotriguaiacylene and DMA = dimethylacetamide, while complex [Zn(4ph4py)(2)(CF(3)COO)(H(2)O)]·(CF(3)COO)(NMP)(7), where NMP = N-methylpyrrolidone, has a doubly bridged coordination chain structure. Complexes [M(3ph3py)(NO(3))(2)]·(NMP)(4) where M = Co or Zn, 3ph3py = tris[3-(3-pyridyl)benzoyl]cyclotriguaiacylene, are isostructural and feature 1D ladder coordination chains. Complexes [Cd(2)(4ph4py)(2)(NO(3))(4)(NMP)]·(NMP)(9)(H(2)O)(4) and [Co(4ph4py)(H(2)O)(2)]·(NO(3))(2)·(DMF)(2), where DMF = dimethylformamide, both have (3,4)-connected 2D coordination polymers with a rare (4(2).6(2))(4.6(2))(2) topology. A 2D coordination polymer with this topology is also found in complex [Co(2)(3ph4py)(2)(NO(3))(H(2)O)(5)]·(NO(3))(3)·(DMF)(9) where 3ph4py = tris[3-(4-pyridyl)benzoyl]cyclotriguaiacylene. All 2D coordination polymer complexes are interpenetrating or polycatenating. [Co(2)(3ph4py)(2)(NO(3))(H(2)O)(5)](3+)polymers form a 2D→3D polycatenation showing self-complementary "hand-shake" interactions between the host-type ligands.     

Coordination polymers assembled from angular dipyridyl ligands and CuII, CdII, CoII salts: crystal structures and properties

Six new metal-organic coordination networks based on linking unit 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (L(1)) or 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (L(3)) and inorganic Cu(II), Cd(II), and Co(II) salts have been prepared and structurally characterized by single-crystal X-ray analysis. Using L(1) to react with three different Cu(II) salts, Cu(OAc)(2).H(2)O, Cu(NO(3))(2).3H(2)O, and CuSO(4).5H(2)O, respectively, two different one-dimensional (1-D) coordination polymers, [[Cu(2)L(1)(mu-OAc)(4)](CHCl(3))(2)](n) (1) [triclinic, space group P1, a = 7.416(3) A, b = 8.207(3) A, c = 14.137(5) A, alpha = 100.333(7) degrees, beta = 105.013(6) degrees, gamma = 94.547(6) degrees, Z = 1] and [[CuL(1)(NO(3))(2)](CHCl(3))(0.5)](n) (2) [monoclinic, space group C2/c, a = 28.070(8) A, b = 9.289(3) A, c = 15.235(4) A, beta = 113.537(5) degrees, Z = 8], and a chiral 3-D open framework, [[CuL(1)(H(2)O)(SO(4))](H(2)O)(2)](n) (3) [orthorhombic, space group P2(1)2(1)2(1), a = 5.509(2) A, b = 10.545(4) A, c = 29.399(11) A, Z = 4], were obtained. Reaction of L(1) and Cd(ClO(4))(2).6H(2)O or Co(ClO(4))(2).6H(2)O, in the presence of NH(4)SCN, yielded another 3-D open framework, [[CdL(1)(NCS)(2)](CH(3)OH)(1.5)](n) (4) [monoclinic, space group C2/c, a = 28.408(10) A, b = 9.997(5) A, c = 7.358(4) A, beta = 99.013(8) degrees, Z = 4], or a 2-D network, [[Co(L(1)())(2)(NCS)(2)](H(2)O)(2.5)](n) (5) [orthorhombic, space group Pnna, a = 22.210(5) A, b = 12.899(3) A, c = 20.232(4) A, Z = 4]. When L(1) was replaced by L(3) to react with Co(ClO(4))(2).6H(2)O and NH(4)SCN, another 2-D coordination polymer, [Co(L(3))(2)(NCS)(2)](n) (6) [monoclinic, space group P2(1)/c, a = 8.120(3) A, b = 9.829(4) A, c = 17.453(6) A, beta = 103.307(6) degrees, Z = 2], was constructed. These results indicate that the nature of the ligands, metal centers, or counteranions plays the critical role in construction of these novel coordination polymers. The interesting porous natures of two 3-D open frameworks 3 and 4 were investigated by TGA and XPRD techniques, and the magnetic properties of the Cu(II) and Co(II) complexes were studied by variable-temperature magnetic susceptibility and magnetization measurements.     

Synthesis and Characterization of Copper(II), Zinc(II), and Potassium Complexes of a Highly Fluorinated Bis(pyrazolyl)borate Ligand

Highly fluorinated, dihydridobis(3,5-bis(trifluoromethyl)pyrazolyl)borate ligand, [H(2)B(3,5-(CF(3))(2)Pz)(2)](-) has been synthesized and characterized as its potassium salt. The copper(II) and zinc(II) complexes, [H(2)B(3,5-(CF(3))(2)Pz)(2)](2)Cu and [H(2)B(3,5-(CF(3))(2)Pz)(2)](2)Zn, have been prepared by metathesis of [H(2)B(3,5-(CF(3))(2)Pz)(2)]K with Cu(OTf)(2) and Zn(OTf)(2), respectively. All the new metal adducts have been characterized by X-ray diffraction. The potassium salt is polymeric and shows several K.F interactions. The Cu center of [H(2)B(3,5-(CF(3))(2)Pz)(2)](2)Cu adopts a square planar geometry, whereas the Zn atom in [H(2)B(3,5-(CF(3))(2)Pz)(2)](2)Zn displays a tetrahedral coordination. Bis(pyrazolyl)borate ligands in the Zn adduct show a significantly distorted boat conformation. The nature and extent of this distortion is similar to that observed for the methylated analog, [H(2)B(3,5-(CH(3))(2)Pz)(2)](2)Zn. This ligand allows a comparison of electronic effects of bis(pyrazolyl)borate ligands with similar steric properties. Crystallographic data for [H(2)B(3,5-(CF(3))(2)Pz)(2)]K: triclinic, space group P&onemacr;, with a = 8.385(1) ?, b = 10.097(2) ?, c = 10.317(1) ?, alpha = 104.193(9) degrees, beta = 104.366(6) degrees, gamma = 91.733(9) degrees, V = 816.5(3) ?(3), and Z = 2. [H(2)B(3,5-(CF(3))(2)Pz)(2)](2)Cu is monoclinic, space group C2/c with a = 25.632(3) ?, b = 9.197(1) ?, c = 17.342(2) ?, beta = 129.292(5) degrees, V = 3164.0(6) ?(3), and Z = 4. [H(2)B(3,5-(CF(3))(2)Pz)(2)](2)Zn is triclinic, space group P&onemacr;, with a = 9.104(1) ?, b = 9.278(1) ?, c = 18.700(2) ?, alpha = 83.560(6) degrees, beta = 88.200(10) degrees, gamma = 78.637(9) degrees, V = 1538.8(3) ?(3), and Z = 2. [H(2)B(3,5-(CH(3))(2)Pz)(2)](2)Zn is monoclinic, space group C2/c with a = 8.445(1) ?, b = 14.514(2) ?, c = 19.983(3) ?, beta = 90.831(8) degrees, V = 2449.1(6) ?(3), and Z = 4.     

pH-Induced formation of metalloligand: increasing structure dimensionality by tuning number of ligand functional sites

Two complexes, 2D [Cu(2)(CN)(2)(4-Hpcih)](n) and 3D [[Cu(2)(CN)(1.5)(4-pcih)].1.25H(2)O](n) (4-Hpcih = 4-pyridinecarbaldehyde isonicotinoyl hydrazone), were obtained using a synthetic approach of pH-induced formation of metalloligands, successfully demonstrating a strategy to increase structure dimensionality by tuning the number of ligand functional sites.     

Anion binding by metallo-receptors of 5,5'-dicarbamate-2,2'-bipyridine ligands

Three 5,5'-dicarbamate-2,2'-bipyridine ligands (L = L(1)-L(3)) bearing ethyl, isopropyl or tert-butyl terminals, respectively, on the carbamate substituents were synthesized. Reaction of the ligands L with the transition metal ions M = Fe(2+), Cu(2+), Zn(2+) or Ru(2+) gave the complexes ML(n)X(2)·xG (1-12, n = 1-3; X = Cl, NO(3), ClO(4), BF(4), PF(6), ?SO(4); G = Et(2)O, DMSO, CH(3)OH, H(2)O), of which [Fe(L(2))(3)???SO(4)]·8.5H(2)O (2), [Fe(L(1))(3)???(BF(4))(2)]·2CH(3)OH (7), [Fe(L(2))(3)???(Et(2)O)(2)](BF(4))(2)·2CH(3)OH (8), [ZnCl(2)(L(1))][ZnCl(2)(L(1))(DMSO)]·2DMSO (9), [Zn(L(1))(3)???(NO(3))(2)]·2H(2)O (10), [Zn(L(2))(3)???(ClO(4))(Et(2)O)]ClO(4)·Et(2)O·2CH(3)OH·1.5H(2)O (11), and [Cu(L(1))(2)(DMSO)](ClO(4))(2)·2DMSO (12) were elucidated by single-crystal X-ray crystallography. In the complexes ML(n)X(2)·xG the metal ion is coordinated by n = 1, 2 or 3 chelating bipyridine moieties (with other anionic or solvent ligands for n = 1 and 2) depending on the transition metal and reaction conditions. Interestingly, the carbamate functionalities are involved in hydrogen bonding with various guests (anions or solvents), especially in the tris(chelate) complexes which feature the well-organized C(3)-clefts for effective guest inclusion. Moreover, the anion binding behavior of the pre-organized tris(chelate) complexes was investigated in solution by fluorescence titration using the emissive [RuL(3)](2+) moiety as a probe. The results show that fluorescent recognition of anion in solution can be achieved by the Ru(II) complexes which exhibit good selectivities for SO(4)(2-).     

X-ray Crystallographic Study of the Ruthenium Blue Complexes [Ru(2)Cl(3)(tacn)(2)](PF(6))(2).4H(2)O, [Ru(2)Br(3)(tacn)(2)](PF(6))(2).2H(2)O, and [Ru(2)I(3)(tacn)(2)](PF(6))(2): Steric Interactions and the Ru-Ru "Bond Length"

X-ray crystal structures are reported for the following complexes: [Ru(2)Cl(3)(tacn)(2)](PF(6))(2).4H(2)O (tacn = 1,4,7-triazacyclononane), monoclinic P2(1)/n, Z = 4, a = 14.418(8) ?, b = 11.577(3) ?, c = 18.471(1) ?, beta = 91.08(5) degrees, V = 3082 ?(3), R(R(w)) = 0.039 (0.043) using 4067 unique data with I > 2.5sigma(I) at 293 K; [Ru(2)Br(3)(tacn)(2)](PF(6))(2).2H(2)O, monoclinic P2(1)/a, Z = 4, a = 13.638(4) ?, b = 12.283(4) ?, c = 18.679(6) ?, beta = 109.19(2) degrees, V = 3069.5 ?(3), R(R(w)) = 0.052 (0.054) using 3668 unique data with I > 2.5sigma(I) at 293 K; [Ru(2)I(3)(tacn)(2)](PF(6))(2), cubic P2(1)/3, Z = 3, a = 14.03(4) ?, beta = 90.0 degrees, V = 2763.1(1) ?(3), R (R(w)) = 0.022 (0.025) using 896 unique data with I > 2.5sigma(I) at 293 K. All of the cations have cofacial bioctahedral geometries, although [Ru(2)Cl(3)(tacn)(2)](PF(6))(2).4H(2)O, [Ru(2)Br(3)(tacn)(2)](PF(6))(2).2H(2)O, and [Ru(2)I(3)(tacn)(2)](PF(6))(2) are not isomorphous. Average bond lengths and angles for the cofacial bioctahedral cores, [N(3)Ru(&mgr;-X)(3)RuN(3)](2+), are compared to those for the analogous ammine complexes [Ru(2)Cl(3)(NH(3))(6)](BPh(4))(2) and [Ru(2)Br(3)(NH(3))(6)](ZnBr(4)). The Ru-Ru distances in the tacn complexes are longer than those in the equivalent ammine complexes, probably as a result of steric interactions.     

Synthesis, characterization and antioxidant activity of naringenin Schiff base and its Cu(II), Ni(II), Zn(II) complexes

A new ligand, naringenin-2-hydroxy benzoyl hydrazone (H(5)L), was prepared by condensation of naringenin with 2-hydroxy benzoyl hydrazine. Its Cu(II), Ni(II), Zn(II) complexes have also been synthesized and characterized on the basis of (1)H-NMR, IR, UV-Vis spectra, elemental analyses, molar conductivity and thermal analyses. The general formula of these complexes was M(H(3)L) [M=Cu(II), Ni(II) and Zn(II)]. In addition, the antioxidant activities (superoxide and hydroxyl radical) of the free ligand and its complexes were determined in vitro. These compounds were found to possess potent antioxidant activity and be better than standard antioxidants like vitamin C and mannitol. In particular, the Cu(II) complex displayed excellent activity on the superoxide radical.     

Pt(II)-promoted [2 + 3] cycloaddition of azide to cyanopyridines: convenient tool toward heterometallic structures

The [2 + 3] cycloaddition reactions (which are greatly accelerated by microwave irradiation) of the di(azido)platinum(II) compounds cis-[Pt(N(3))(2)(PPh(3))(2)] (1) with cyanopyridines NCR (2) (R = 4-, 3-, and 2-NC(5)H(4)) give the corresponding bis(pyridyltetrazolato) complexes trans-[Pt(N(4)CR)(2)(PPh(3))(2)] (3) [R = 4-NC(5)H(4) (3a), 3-NC(5)H(4) (3b), and 2-NC(5)H(4) (3c)]. Compound 3c has been characterized as the N(1)N(2)-bonded isomer in the solid state by X-ray crystallography and represents the first bis(tetrazolato) complex of this kind. Complexes 3a and 3b have been used as metallaligands to generate heteronuclear coordination polymers in the presence of copper nitrate. A one-dimensional supramolecular architecture was obtained as the exclusive product, {trans-[Pt(2)(N(4)CR)(4)(PPh(3))(4)Cu](n)(NO(3))(2n).nH(2)O (4.nH(2)O) (R = 4-NC(5)H(4)), when 3a was employed, whereas with 3b the heteronuclear square complex trans-[Pt(N(4)CR)(2)(PPh(3))(2)Cu(NO(3))(2)(H(2)O)](2) (5) (R = 3-NC(5)H(4)), composed of Pt/Cu ions, was obtained. All the isolated complexes were characterized by IR, elemental, and (for 3b, 3c, 4, and 5) X-ray structural analyses. Complexes 3 were additionally characterized by (1)H, (13)C, and (31)P {(1)H} NMR spectroscopies.     

Synthesis, structures, and magnetic properties of the copper(II), cobalt(II), and manganese(II) complexes with 9-acridinecarboxylate and 4-quinolinecarboxylate ligands

To explore the relationships between the structures of ligands and their complexes, we have synthesized and characterized a series of metal complexes with two structurally related ligands, 9-acridinecarboxylic acid (HL(1)) and 4-quinolinecarboxylate acid (HL(2)), [Cu(2)(mu(2)-OMe)(2)(L(1))(2)(H(2)O)(0.69)](n) 1, [Cu(2)(L(1))(4)(CH(3)OH)(2)] 2, [Cu(3)(L(1))(6)(CH(3)OH)(6)].3H(2)O 3, [Mn(3)(L(1))(6)(CH(3)OH)(6)].3H(2)O 4, [Co(3)(L(1))(6)(CH(3)OH)(6)].3H(2)O 5, [Cu(L(2))(2)](n) 6, [Mn(L(2))(2)(H(2)O)](n) 7, and [Co(L(2))(2)(H(2)O)](n) 8. 1 is a three-dimensional (3D) polymer with an interpenetrating NbO type network showing one-dimensional (1D) channels, whereas 2 and 3 take bi- and trinuclear structures, respectively, because of the differences in basicity of the reaction systems in preparing the three complexes. 4 and 5 have trinuclear structures similar to that of 3. In 1-5, ligand L(1) performs different coordination modes with N,O-bridging in 1 and O,O'-bridging in 2-5, and the metal ions also show different coordination geometries: square planar in 1, square pyramidal in 2, and octahedral in 3-5. 6 has a two-dimensional structure containing (4,4) grids in which L(2) adopts the N,O-bridging mode and the Cu(II) center takes square planar geometry. 7 and 8 are isostructural complexes showing 1D chain structures, with L(2) adopting the O,O-bridging mode. In addition, the intermolecular O-H...N hydrogen bonds and pi-pi stacking interactions further extend the complexes (except 1 and 6), forming 3D structures. The magnetic properties of 2-7 have been investigated and discussed in detail.     

Pyridazine- versus pyridine-based tridentate ligands in first-row transition metal complexes

A series of first-row transition metal complexes with the unsymmetrically disubstituted pyridazine ligand picolinaldehyde (6-chloro-3-pyridazinyl)hydrazone (PIPYH), featuring an easily abstractable proton in the backbone, was prepared. Ligand design was inspired by literature-known picolinaldehyde 2-pyridylhydrazone (PAPYH). Reaction of PIPYH with divalent nickel, copper, and zinc nitrates in ethanol led to complexes of the type [Cu(II)(PIPYH)(NO(3))(2)] (1) or [M(PIPYH)(2)](NO(3))(2) [M = Ni(II) (2) or Zn(II) (3)]. Complex synthesis in the presence of triethylamine yielded fully- or semideprotonated complexes [Cu(II)(PIPY)(NO(3))] (4), [Ni(II)(PIPYH)(PIPY)](NO(3)) (5), and [Zn(II)(PIPY)(2)] (6), respectively. Cobalt(II) nitrate is quantitatively oxidized under the reaction conditions to [Co(III)(PIPY)(2)](NO(3)) (7) in both neutral and basic media. X-ray diffraction analyses reveal a penta- (1) or hexa-coordinated (2, 3, and 7) metal center surrounded by one or two tridentate ligands and, eventually, κ-O,O' nitrate ions. The solid-state stoichiometry was confirmed by electron impact (EI) and electrospray ionization (ESI) mass spectrometry. The diamagnetic complexes 5 and 6 were subjected to (1)H NMR spectroscopy, suggesting that the ligand to metal ratio remains constant in solution. Electronic properties were analyzed by means of cyclic voltammetry and, in case of copper complexes 1 and 4, also by electron paramagnetic resonance (EPR) spectroscopy, showing increased symmetry upon deprotonation for the latter, which is in accordance with the proposed stoichiometry [Cu(II)(PIPY)(NO(3))]. Protic behavior of the nickel complexes 2 and 5 was investigated by UV/vis spectroscopy, revealing high π-backbonding ability of the PIPYH ligand resulting in an unexpected low acidity of the hydrazone proton in nickel complex 2.     

Two novel heterometallic Cu(II)-Sr(II) coordination polymers based on 3,5-pyrazoledicarboxylic acid: synthesis, crystal structures and magnetic properties

The syntheses, crystal structures and magnetic properties are described for two novel 2D heterometallic Cu(II)-Sr(II) coordination polymers {Sr(H(2)O)(6)[(Im)(4)Cu(4)(pdc)(4)Sr(H(2)O)(4)]·6H(2)O}(n) (1) and [Cu(2)(H(2)O)(2)(pdc)(2)Sr(H(2)O)(3)](n) (2) (H(3)pdc = 3,5-pyrazoledicarboxylic acid; Im = imidazole). The 1 : 1 : 1 : 5 reaction of SrCl(2)·6H(2)O, Cu(NO(3))(2)·3H(2)O, H(3)pdc and imidazole in H(2)O-EtOH at 120 °C under autogenous pressure gave 1. Complex 2 was obtained from the 1 : 1 : 1 H(3)pdc/Sr(OH)(2)·8H(2)O/Cu(NO(3))(2)·3H(2)O reaction mixture in H(2)O-EtOH under solvothermal conditions. Complex 1 can be described as a 2D grid-shaped network with the four Cu(II) ions in a saddle-like conformation. In complex 2, Sr(II) ions link metalloligands [Cu(2)(pdc)(2)(H(2)O)(2)](2-) to generate a 2D layer framework. Variable-temperature solid-state dc magnetic susceptibility studies have been performed in the temperature range 2.0-300 K for complexes 1 and 2. Antiferromagnetic Cu(II)···Cu(II) exchange interactions were found for both 1 and 2.     

Preparation of a family of hexanuclear rhenium cluster complexes containing 5-(phenyl)tetrazol-2-yl ligands and alkylation of 5-substituted tetrazolate ligands

The preparation of two new families of hexanuclear rhenium cluster complexes containing benzonitrile and phenyl-substituted tetrazolate ligands is described. Specifically, we report the preparation of a series of cluster complexes with the formula [Re(6)Se(8)(PEt(3))(5)L](2+) where L = benzonitrile, p-aminobenzonitrile, p-methoxybenzonitrile, p-acetylbenzonitrile, or p-nitrobenzonitrile. All of these complexes undergo a [2 + 3] cycloaddition with N(3)(-) to generate the corresponding [Re(6)Se(8)(PEt(3))(5)(5-(p-X-phenyl)tetrazol-2-yl)](+) (or [Re(6)Se(8)(PEt(3))(5)(2,5-p-X-phenyltetrazolate)](+)) cluster complexes, where X = NH(2), OMe, H, COCH(3), or NO(2). Crystal structure data are reported for three compounds: [Re(6)Se(8)(PEt(3))(5)(p-acetylbenzonitrile)](BF(4))(2)?MeCN, [Re(6)Se(8)(PEt(3))(5)(2,5-phenyltetrazolate)](BF(4))?CH(2)Cl(2), and [Re(6)Se(8)(PEt(3))(5)(2,5-p-aminophenyltetrazolate)](BF(4)). Treatment of [Re(6)Se(8)(PEt(3))(5)(2,5-phenyltetrazolate)](BF(4)) with HBF(4) in CD(3)CN at 100 °C leads to protonation of the tetrazolate ring and formation of [Re(6)Se(8)(PEt(3))(5)(CD(3)CN)](2+). Surprisingly, alkylation of the phenyl and methyl tetrazolate complexes ([Re(6)Se(8)(PEt(3))(5)(2,5-N(4)CPh)](BF(4)) and [Re(6)Se(8)(PEt(3))(5)(1,5-N(4)CMe)](BF(4))) with methyl iodide and benzyl bromide, leads to the formation of mixtures of 1,5- and 2,5-disubstituted tetrazoles.     

Nitrosyl induces phosphorous-acid dissociation in ruthenium(II)

The trans-[Ru(NO)(NH(3))(4)(P(OH)(3))]Cl(3) complex was synthesized by reacting [Ru(H(2)O)(NH(3))(5)](2+) with H(3)PO(3) and characterized by spectroscopic ((31)P-NMR, δ = 68 ppm) and spectrophotometric techniques (λ = 525 nm, ε = 20 L mol(-1) cm(-1); λ = 319 nm, ε = 773 L mol(-1) cm(-1); λ = 241 nm, ε = 1385 L mol(-1) cm(-1); ν(NO(+)) = 1879 cm(-1)). A pK(a) of 0.74 was determined from infrared measurements as a function of pH for the reaction: trans-[Ru(NO)(NH(3))(4)(P(OH)(3))](3+) + H(2)O ? trans-[Ru(NO)(NH(3))(4)(P(O(-))(OH)(2))](2+) + H(3)O(+). According to (31)P-NMR, IR, UV-vis, cyclic voltammetry and ab initio calculation data, upon deprotonation, trans-[Ru(NO)(NH(3))(4)(P(OH)(3))](3+) yields the O-bonded linkage isomer trans- [Ru(NO)(NH(3))(4)(OP(OH)(2))](2+), then the trans-[Ru(NO)(NH(3))(4)(OP(H)(OH)(2))](3+) decays to give the final products H(3)PO(3) and trans-[Ru(NO)(NH(3))(4)(H(2)O)](3+). The dissociation of phosphorous acid from the [Ru(NO)(NH(3))(4)](3+) moiety is pH dependent (k(obs) = 2.1 × 10(-4) s(-1) at pH 3.0, 25 °C).     

Oxamato-bridged trinuclear Ni(II)Cu(II)Ni(II) complexes with irregular spin state structures and a binuclear Ni(II)Cu(II) complex with an unusual supramolecular structure: crystal structure and magnetic properties

Four oxamato-bridged heterotrinuclear Ni(II)Cu(II)Ni(II) complexes of formula ([Ni(bispictn)](2)Cu(pba))(ClO(4))(2).2.5H(2)O (1), ([Ni(bispictn)](2)Cu(pbaOH))(ClO(4))(2).H(2)O (2), ([Ni(cth)](2)Cu(pba))(ClO(4))(2) (3), and ([Ni(cth)](2)Cu(opba))(ClO(4))(2).H(2)O (4) and a binuclear Ni(II)Cu(II) complex of formula [Cu(opba)Ni(cth)].CH(3)OH (5) have been synthesized and characterized by means of elemental analysis, IR, ESR, and electronic spectra, where pba = 1,3-propylenebis(oxamato), pbaOH = 2-hydroxyl-1,3-propylenebis(oxamato), opba = o-phenylenebis(oxamato), bispictn = N,N'-bis(2-pyridylmethyl)-1,3-propanediamine, and cth = rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane. The crystal structures of 1, 3, and 5 have been determined. The structures of complexes 1 and 3 consist of trinuclear cations and perchlorate anions, and that of 5 consists of neutral binuclear molecules which are connected by hydrogen bonds and pi-pi interactions to produce a unique supramolecular "double" sheet. In the three complexes, the copper atom in a square-planar or axially elongated octahedral environment and the nickel atom in a distorted octahedral environment are bridged by the oxamato groups, with Cu.Ni separations between 5.29 and 5.33 A. The magnetic properties of all five complexes have been investigated. The chi(M)T versus T plots for 1-4 exhibit the minimum characteristic of antiferromagnetically coupled NiCuNi species with an irregular spin state structure and a spin-quartet ground state. The chi(M)T versus T plot for 5 is typical of an antiferromagnetically coupled NiCu pair with a spin-doublet ground state. The Ni(II)-Cu(II) isotropic interaction parameters for the five complexes were evaluated and are between 102 and 108 cm(-)(1) (H = -JS(Cu).S(Ni)).     

Characterization of imidazolate-bridged dinuclear and mononuclear hydroperoxo complexes

Dinucleating ligands having two metal-binding sites bridged by an imidazolate moiety, Hbdpi, HMe(2)bdpi, and HMe(4)bdpi (Hbdpi = 4,5-bis(di(2-pyridylmethyl)aminomethyl)imidazole, HMe(2)bdpi = 4,5-bis((6-methyl-2-pyridylmethyl)(2-pyridylmethyl)aminomethyl)imidazole, HMe(4)bdpi = 4,5-bis(di(6-methyl-2-pyridylmethyl)aminomethyl)imidazole), have been designed and synthesized as model ligands for copper-zinc superoxide dismutase (Cu,Zn-SOD). The corresponding mononucleating ligands, MeIm(Py)(2), MeIm(Me)(1), and MeIm(Me)(2) (MeIm(Py)(2) = (1-methyl-4-imidazolylmethyl)bis(2-pyridylmethyl)amine, MeIm(Me)(1) = (1-methyl-4-imidazolylmethyl)(6-methyl-2-pyridylmethyl)(2-pyridylmethyl)amine, MeIm(Me)(2) = (1-methyl-4-imidazolyl-methyl)bis(6-methyl-2-pyridylmethyl)amine), have also been synthesized for comparison. The imidazolate-bridged Cu(II)-Cu(II) homodinuclear complexes represented as [Cu(2)(bdpi)(CH(3)CN)(2)](ClO(4))(3).CH(3)CN.3H(2)O (1), [Cu(2)(Me(2)bdpi)(CH(3)CN)(2)](ClO(4))(3) (2), [Cu(2)(Me(4)bdpi)(H(2)O)(2)](ClO(4))(3).4H(2)O (3), a Cu(II)-Zn(II) heterodinuclear complex of the type of [CuZn(bdpi)(CH(3)CN)(2)](ClO(4))(3).2CH(3)CN (4), Cu(II) mononuclear complexes of [Cu(MeIm(Py)(2))(CH(3)CN)](ClO(4))(2).CH(3)CN (5), [Cu(MeIm(Me)(1))(CH(3)CN)](ClO(4))(2)( )()(6), and [Cu(MeIm(Me)(2))(CH(3)CN)](ClO(4))(2)( )()(7) have been synthesized and the structures of complexes 5-7 determined by X-ray crystallography. The complexes 1-7 have a pentacoordinate structure at each metal ion with the imidazolate or 1-methylimidazole nitrogen, two pyridine nitrogens, the tertiary amine nitrogen, and a solvent (CH(3)CN or H(2)O) which can be readily replaced by a substrate. The reactions between complexes 1-7 and hydrogen peroxide (H(2)O(2)) in the presence of a base at -80 degrees C yield green solutions which exhibit intense bands at 360-380 nm, consistent with the generation of hydroperoxo Cu(II) species in all cases. The resonance Raman spectra of all hydroperoxo intermediates at -80 degrees C exhibit a strong resonance-enhanced Raman band at 834-851 cm(-1), which shifts to 788-803 cm(-1) (Deltanu = 46 cm(-1)) when (18)O-labeled H(2)O(2) was used, which are assigned to the O-O stretching frequency of a hydroperoxo ion. The resonance Raman spectra of hydroperoxo adducts of complexes 2 and 6 show two Raman bands at 848 (802) and 834 (788), 851 (805), and 835 (789) cm(-1) (in the case of H(2)(18)O(2), Deltanu = 46 cm(-1)), respectively. The ESR spectra of all hydroperoxo complexes are quite close to those of the parent Cu(II) complexes except 6. The spectrum of 6 exhibits a mixture signal of trigonal-bipyramid and square-pyramid which is consistent with the results of resonance Raman spectrum.