Synthesis, characterization, and magnetic properties of self-assembled compounds based on discrete homotrinuclear complexes of Cu(II)

Three new supramolecular entities of Cu(II) were synthesized and characterized: [(Cu(H(2)O)(tmen))(2)(mu-Cu(H(2)O)(opba))](2)[(ClO(4))(2)](2).2H(2)O (1), [(Cu(H(2)O)(tmen))(2) (mu-Cu(H(2)O) (Me(2)pba))](2)[(ClO(4))(2)](2) (2), and [(Cu(H(2)O)(tmen))(Cu(tmen))(mu-Cu(OHpba))](n)() ((ClO(4))(2))(n)().nH(2)O (3), where opba = o-phenylenbis(oxamato), Me(2)pba = 2,2-dimethyl-1,3-propylenbis(oxamato), OHpba = 2-hydroxy-1,3-propylenbis(oxamato), and tmen = N,N,N'N'-tetramethylethylenediamine. The crystal structures of 1, 2, and 3 were solved. Complex 1 crystallizes in the monoclinic system, space group C2/c with a = 20.572(4) A, b = 17.279(6) A, c = 22.023(19) A, beta = 103.13(4) degrees, and Z = 8. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 16.7555(7) A, b = 13.5173(5) A, c = 17.1240(7) A, beta = 104.9840(10) degrees, and Z = 4. Complex 3 crystallizes in the orthorhombic system, space group Pca2(1) with a = 21.2859(4) A, b = 12.8286(10) A, c = 12.6456(2) A, and Z = 4. The three complexes are very similar in structure: a trinuclear Cu(II) complex with the two terminal Cu(II) ions blocked by N,N,N',N'-tetramethylethylenediamine, but with a different environment in the Cu(II) central ion. In the case of complex 1, two of these trinuclear entities are packed with a short distance between the central Cu(II) ions of two separate entities forming a hexanuclear-type compound. In the case of 2, two of these trinuclear entities are linked by a hydrogen bond between a water molecule of one terminal Cu(II) and one oxygen atom of the oxamato ligand of the neighboring entity, also forming a hexanuclear complex. In the case of complex 3, the intermolecular linkages give a one-dimensional system where the OH groups of the OHpba entities are linked to the terminal Cu(II) of the neighboring entities. The magnetic properties of the three complexes were studied by susceptibility measurements vs temperature. For complex 1, an intramolecular J value of -312.1 cm(-)(1) and a contact dipolar interaction of -0.44K were found. For complex 2 and 3 the fit was made by the irreducible tensor operator formalism (ITO). The values obtained were as follows: J(1) = -333.9 cm(-)(1) and J(2) = 0.67 cm(-)(1) for 2 and J(1) = -335.9 cm(-)(1) and J(2) = 3.5 cm(-)(1) for 3.     

Oxamato-bridged trinuclear NiIICuIINiII complexes: a new (NiIICuIINiII)2 hexanuclear complex and supramolecular structures. Characterization and magnetic properties

Eight oxamato-bridged heterotrinuclear Ni(II)Cu(II)Ni(II) complexes of formula ([Ni(H(2)O)(dpt)](2)(mu-Cu(H(2)O)(opba)))(ClO(4))2 (1), ([Ni(H(2)O)(dien)](2)(mu-Cu(pba)))(ClO(4))(2).6H(2)O (2), ([Ni(H(2)O)(Medpt)](2)(mu-Cu(OHpba)))(ClO(4))(2).4H(2)O (3), ([Ni(H(2)O)(dien)](2)(mu-Cu(Me(2)pba)))(ClO(4))(2).2.5H(2)O (4), ([Ni(H(2)O)(dpt)](2)(mu-Cu(Me(2)pba)))(ClO(4))(2).2H(2)O (5), ([Ni(H(2)O)(dien)](2)(mu-Cu(OHpba)))(ClO(4))(2).4H(2)O (6), ([Ni(2)(dpt)(2)(mu-Cu(H(2)O)(pba))](2)(mu-N(3))(2))Na(2)(ClO(4))(4).6H(2)O (7), and ([Cu(H(2)O)(2)(dpt)Ni(2)(H(2)O)(dpt)(2)](mu-H(2)Me(2)pba(2-)))(ClO(4))(4).3H(2)O (8) in which opba = o-phenylenbis(oxamato), pba = 1,3-propylenebis(oxamato), OHpba = 2-hydroxy-1,3-propylenebis(oxamato), Me(2)pba = 2,2-dimethyl-1,3-propylenbis(oxamato), dpt = 3,3'-diaminodipropylamine, dien = 2,2'-diaminodiethylamine, and Medpt = 3,3'-diamino-N-methyldipropylamine were synthesized and characterized. The crystal structures of 1, 7, and 8 were solved. For complex 1, the trinuclear entities are linked by hydrogen bonds forming a one-dimensional system, and for complex 8, the presence of van der Waals interactions gives a one-dimensional system, too. For complex 7, the trinuclear entities are self-assembled by azido ligands, given a hexanuclear system; each of these hexanuclear entities are self-assembled through two [Na(O)(3)(H(2)O)(3)] octahedral-sharing one-edge entities, given a one-dimensional system. The magnetic behavior of complexes 2-7 was investigated by variable-temperature magnetic susceptibility measurements. Complexes 2-6 exhibit the minimum characteristic of this kind of polymetallic species with an irregular spin state structure. The Jvalue through the oxamato bridge varied between -88 cm(-1) (for 6) and -111.2 cm(-1) (for 5). For complex 7, the values obtained were J(1) = -101.7 cm(-1) (through the oxamato ligand) and J(2) = -3.2 cm(-1) (through the azido ligand).     

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)).     

Electron paramagnetic resonance and density-functional theory studies of Cu(II)-bis(oxamato) complexes

In this work we present the investigation of the influence of electronic and structural variations induced by varying the N,N'-bridge on the magnetic properties of Cu(II)- bis(oxamato) complexes. For this study the complexes [Cu(opba)] (2-) ( 1, opba = o-phenylene- bis(oxamato)), [Cu(nabo)] (2-) ( 2, nabo = 2,3-naphthalene- bis(oxamato)), [Cu(acbo)] (2-) ( 3, acbo = 2,3-anthrachinone- bis(oxamato)), [Cu(pba)] (2-) ( 4, pba = propylene- bis(oxamato)), [Cu(obbo)] (2-) ( 5, obbo = o-benzyl- bis(oxamato)), and [Cu(npbo)] (2-) ( 6, npbo = 1,8-naphthalene- bis(oxamato)), and the respective structurally isomorphic Ni(II) complexes ( 8- 13) have been prepared as ( (n)Bu 4N) (+) salts. The new complex ( (n)Bu 4N) 2[Cu(R-bnbo)].2H 2O ( 7, R-bnbo = (R)-1,1'-binaphthalene-2,2'- bis(oxamato)) was synthesized and is the first chiral complex in the series of Cu(II)-bis(oxamato) complexes. The molecular structure of 7 has been determined by single crystal X-ray analysis. The Cu(II) ions of the complexes 1- 7 are eta (4)(kappa (2) N, kappa (2) O) coordinated with a more or less distorted square planar geometry for 1- 6 and a distorted tetrahedral geometry for 7. Using pulsed Electron Nuclear Double Resonance on complex 6, detailed information about the relative orientation of the hyperfine ( A) and nuclear quadrupole tensors ( Q) of the coordinating nitrogens with respect to the g tensor were obtained. Electron Paramagnetic Resonance studies in the X, Q, and W-band at variable temperatures were carried out to extract g and A values of N ligands and Cu ion for 1- 7. The hyperfine values were interpreted in terms of spin population on the corresponding atoms. The obtained trends of the spin population for the monomeric building blocks were shown to correlate to the trends obtained in the dependence of the exchange interaction of the corresponding trinuclear complexes on their geometry.     

New oxamidato-bridged Cu(II)-Ni(II) complexes: supramolecular structures with thiocyanate ligands and hydrogen bonds. Magnetostructural studies: DFT calculations

Four new supramolecular compounds of Cu(II)-Ni(II) have been synthesized and characterized: [Cu(Me(2)oxpn)Ni(mu-NCS)(H(2)O)(tmen)](2)(ClO(4))(2) (1), [Cu(Me(2)oxpn)Ni(mu-NCS)(H(2)O)(tmen)](2)(PF(6))(2) (2), [Cu(oxpn)Ni(mu-NCS)(NCS) (tmen)](n) (3), and [Cu(Me(2)oxpn)Ni(mu-NCS)(NCS)(tmen)](n) (4), where oxpn = N,N'-bis(3-aminopropyl)oxamidate, Me(2)oxpn = N,N'-bis(3-amino-2,2'-dimethylpropyl)oxamidate, and tmen = N,N,N',N'-tetramethylethylenediamine. Their crystal structures were solved. Complexes 1 and 2 have the same tetranuclear cationic part but a different counteranion. The cationic part consists of two [Cu(Me(2)oxpn)Ni] moieties linked by SCN(-) bridged ligands and intra-tetranuclear hydrogen bonds. In the case of complex 3, a two-dimensional system was built, the thiocyanate ligand linking the dinuclear units gives a chain, and the chains are linked together by hydrogen bonds; intrachain hydrogen bonds are also present. For complex 4, the thiocyanate ligands produce intermolecular linkages between the dinuclear entities, giving a one-dimensional system; intrachain hydrogen bonds are also present. The magnetic properties of the four complexes were studied by susceptibility measurements vs temperature. DFT calculations were made to study the contribution of the SCN(-) and hydrogen bond bridges in the magnetic coupling.     

Pyrophosphate-mediated magnetic interactions in Cu(II) coordination complexes

The reaction in water of Cu(NO(3))(2)·2.5H(2)O with 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), or 1,10-phenanthroline-5-amine (phenam), and sodium pyrophosphate (Na(4)P(2)O(7)), at various pHs, afforded three new copper(II)-pyrophosphate complexes, namely, {[Cu(bipy)(cis-H(2)P(2)O(7))](2)}·3H(2)O (1a), {[Cu(phen)(H(2)O)](4)(HP(2)O(7))(2)}(ClO(4))(2)·4H(2)O (2), and {[Cu(2)(phenam)(2)(P(2)O(7))](2)·25H(2)O}(n) (3). A solvent free crystalline phase of 1a was also isolated with formula {[Cu(bipy)(trans-H(2)P(2)O(7))](2)} (1b), which can be regarded as a pseudo-polymorph of 1a. Single crystal X-ray analyses revealed these compounds to have uncommon molecular architectures, with 3 being an unprecedented pyrophosphate-containing two-dimensional (2D) polymer. Compounds 1a/1b and 2 are discrete di- and tetra-nuclear complexes, respectively. The cationic {[Cu(phen)(H(2)O)](4)(HP(2)O(7))(2)}(2+) unit in 2 presents a unique quasi-flat structure, held together by solely in-plane pyrophosphate bridging modes (short O(eq)-P-O(eq) and long O(eq)-P-O-P-O(eq) pathways), a coordination arrangement also not previously reported. A different tetranuclear copper(II)-pyrophosphate arrangement is found in 3, with two classically bridged dimers (O(eq)-P-O(eq) pathway) joined together by auxiliary equatorial-axial μ-O pyrophosphate bridges. Here, the bidimensionality is reached through bridging phenam ligands, which provide further inter-"tetramer" metal-metal connections [(N,N')(eq)-(N')(ax) pathway], leading to the formation of an expanded covalent network based on the [Cu(2)(phenam)(2)(P(2)O(7))](2) moiety. Variable-temperature magnetic susceptibility measurements on polycrystalline samples of 2 and 3 revealed net antiferromagnetic coupling between metal centers with J(2a) = -7.9(2) cm(-1), J(2b) = -46.9(3) cm(-1), J(2c) = 0 cm(-1) in 2 (H = -J(2a)[S(Cu(1))·S(Cu(2)) + S(Cu(1a))·S(Cu(2a))] - J(2b)[S(Cu(1))·S(Cu(2a)) + S(Cu(1a))·S(Cu(2))] - J(2c)S(Cu(2))·S(Cu(2a))), and J(3a) = -87.9(2) cm(-1), J(3b) = -5(1) cm(-1) and J(3c) = +5(3) cm(-1) in 3 (H = -J(3a)[S(Cu(1))·S(Cu(2)) + S(Cu(1a))·S(Cu(2a))] - J(3b)[S(Cu(1))·S(Cu(2a)) + S(Cu(1a))·S(Cu(2))] - J(3c)S(Cu(2))·S(Cu(2a))). For 1a, a net ferromagnetic coupling is observed with J(1a) = +0.86(1) cm(-1) (H = -J S(A)·S(B) + S(A)·D· S(B) + βH (g(A)S(A) + g(B)S(B)). This is the first example of ferromagnetic coupling in pyrophosphate-complexes reported to date. A structure-function correlation study focusing on magnetic exchange across the observed diverse pyrophosphate-bridges is described with density functional theory (DFT) calculations included to support the stated observations.     

Macrocyclic copper(II) and zinc(II) complexes incorporating phosphate esters

Slow evaporation of solutions prepared by adding either Cu(ClO(4))(2).6H(2)O or Zn(ClO(4))(2).6H(2)O to solutions containing appropriate proportions of Me(3)tacn (1,4,7-trimethyl-1,4,7-triazacyclononane) and sodium phenyl phosphate (Na(2)PhOPO(3)) gave dark blue crystals of [Cu(3)(Me(3)tacn)(3)(PhOPO(3))(2)](ClO(4))(2).(1)/(2)H(2)O (1) and colorless crystals of [Zn(2)(Me(3)tacn)(2)(H(2)O)(4)(PhOPO(3))](ClO(4))(2).H(2)O (2), respectively. Blue crystals of [Cu(tacn)(2)](BNPP)(2) (3) formed in an aqueous solution of [Cu(tacn)Cl(2)], bis(p-nitrophenyl phosphate) (BNPP), and HEPES buffer (pH 7.4). Compound 1 crystallizes in the triclinic space group P1 (No. 2) with a = 9.8053(2) A, b = 12.9068(2) A, c = 22.1132(2) A, alpha = 98.636(1) degrees, beta = 99.546(1) degrees, gamma = 101.1733(8) degrees, and Z = 2 and exhibits trinuclear Cu(II) clusters in which square pyramidal metal centers are capped by two phosphate esters located above and below the plane of the metal centers. The trinuclear cluster is asymmetric having Cu...Cu distances of 4.14, 4.55, and 5.04 A. Compound 2 crystallizes in the monoclinic space group P2(1)/c (No. 14) with a = 13.6248(2) A, b = 11.6002(2) A, c = 25.9681(4) A, beta = 102.0072(9) degrees, and Z = 4 and contains a dinuclear Zn(II) complex formed by linking two units of [Zn(Me(3)tacn)(OH(2))(2)](2+) by a single phosphate ester. Compound 3 crystallizes in the monoclinic space group C2/c (No. 15) with a = 24.7105(5) A, b = 12.8627(3) A, c = 14.0079(3) A, beta = 106.600(1) degrees, and Z = 4 and consists of mononuclear [Cu(tacn)(2)](2+) cations whose charge is balanced by the BNPP(-) anions.     

Syntheses, crystal structures, and magneto-structural correlations of novel Cu(II) complexes containing a planar [Cu(mu-L1)]2 (HL1 = 3-(2-pyridyl)pyrazole) unit: from dinuclear to tetranuclear and then to one-dimensional compounds

Seven new Cu(II) complexes based on a binuclear planar unit [Cu(mu-L(1))](2), [[Cu(mu-L(1))(NO(3))(H(2)O)](2) (1), [Cu(mu-L(1))(HL(1))(ClO(4))](2) (2), [Cu(4)(mu-L(1))(6)(NO(3))(2)] (3), [Cu(4)(mu-L(1))(6)(L(1))(2)] (4), [Cu(4)(mu-L(1))(6)(mu-L(2))](n) (5), [Cu(4)(mu-L(1))(6)(mu-L(3))](n) (6), [[Cu(4)(mu-L(1))(4)(mu-L(4))(2)](H(2)O)(3)](n) (7) (HL(1) = 3-(2-pyridyl)pyrazole, L(2) = 1,8-naphthalenedicarboxylate, L(3) = terephthalate, L(4) = 2,6-pyridinedicarboxylate)}, have been synthesized and characterized by elemental analysis, IR, and X-ray diffraction. In 1 and 2, the Cu(II) centers are linked by deprotonated pyrazolyl groups to form dinuclear structures. 3 and 4 have similar gridlike tetranuclear structures in which two additional deprotonated L(1) ligands bridge two [Cu(mu-L(1))](2) units perpendicularly. 5 and 6 consist of similar one-dimensional (1-D) chains in which gridlike tetranuclear copper(II) units similar to that of 3 are further linked by L(2) or L(3) ligands, respectively. And, in 7, L(4) ligands link [Cu(mu-L(1))](2) binuclear units to form a tetranuclear gridlike structure in chelating/bridging mode and simultaneously bridge the tetranuclear units to form a 1-D chain. The magnetic properties of all complexes were studied by variable-temperature magnetic susceptibility and magnetization measurements. The obtained parameters of J range from -33.1 to -211 cm(-1), indicating very strong antiferromagnetic coupling between Cu(II) ions. The main factor that affects the |J| parameter is the geometry of the Cu(N(2))(2)Cu entity. From the magnetic point of view, 1 and 2 feature "pure" dinuclear, 3 and 5 tetranuclear, and 4, 6, and 7 pseudodinuclear moieties.     

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.     

Synthesis, characterization, and structures of copper(II)-thiosulfate complexes incorporating tripodal tetraamine ligands

The reaction of [Cu(L)(H(2)O)](2+) with an excess of thiosulfate in aqueous solution produces a blue to green color change indicative of thiosulfate coordination to Cu(II) [L = tren, Bz(3)tren, Me(6)tren, and Me(3)tren; tren = tris(2-aminoethyl)amine, Bz(3)tren = tris(2-benzylaminoethyl)amine, Me(6)tren = tris(2,2-dimethylaminoethyl)amine, and Me(3)tren = tris(2-methylaminoethyl)amine]. In excess thiosulfate, only [Cu(Me(6)tren)(H(2)O)](2+) promotes the oxidation of thiosulfate to polythionates. Products suitable for single-crystal X-ray diffraction analyses were obtained for three thiosulfate complexes, namely, [Cu(tren)(S(2)O(3))].H(2)O, [Cu(Bz(3)tren)(S(2)O(3))].MeOH, and (H(3)Me(3)tren)[Cu(Me(3)tren)(S(2)O(3))](2)(ClO(4))(3). Isolation of [Cu(Me(6)tren)(S(2)O(3))] was prevented by its reactivity. In each complex, the copper(II) center is found in a trigonal bipyramidal (TBP) geometry consisting of four amine nitrogen atoms, with the bridgehead nitrogen in an axial position and an S-bound thiosulfate in the other axial site. Each structure exhibits H bonding (involving the amine ligand, thiosulfate, and solvent molecule, if present), forming either 2D sheets or 1D chains. The structure of [Cu(Me(3)tren)(MeCN)](ClO(4))(2) was also determined for comparison since no structures of mononuclear Cu(II)-Me(3)tren complexes have been reported. The thiosulfate binding constant was determined spectrophotometrically for each Cu(II)-amine complex. Three complexes yielded the highest values reported to date [K(f) = (1.82 +/- 0.09) x 10(3) M(-1) for tren, (4.30 +/- 0.21) x 10(4) M(-1) for Bz(3)tren, and (2.13 +/- 0.05) x 10(3) M(-1) for Me(3)tren], while for Me(6)tren, the binding constant was much smaller (40 +/- 10 M(-1)).     

Binuclear copper(II) complexes of xylyl-bridged bis(1,4,7-triazacyclononane) ligands

Copper(II) complexes of three bis(tacn) ligands, [Cu(2)(T(2)-o-X)Cl(4)] (1), [Cu(2)(T(2)-m-X)(H(2)O)(4)](ClO(4))(4).H(2)O.NaClO(4) (2), and [Cu(2)(T(2)-p-X)Cl(4)] (3), were prepared by reacting a Cu(II) salt and L.6HCl (2:1 ratio) in neutral aqueous solution [T(2)-o-X = 1,2-bis(1,4,7-triazacyclonon-1-ylmethyl)benzene; T(2)-m-X = 1,3-bis(1,4,7-triazacyclonon-1-ylmethyl)benzene; T(2)-p-X = 1,4-bis(1,4,7-triazacyclonon-1-ylmethyl)benzene]. Crystals of [Cu(2)(T(2)-m-X)(NPP)(mu-OH)](ClO(4)).H(2)O (4) formed at pH = 7.4 in a solution containing 2 and disodium 4-nitrophenyl phosphate (Na(2)NPP). The binuclear complexes [Cu(2)(T(2)-o-XAc(2))(H(2)O)(2)](ClO(4))(2).4H(2)O (5) and [Cu(2)(T(2)-m-XAc(2))(H(2)O)(2)](ClO(4))(2).4H(2)O (6) were obtained on addition of Cu(ClO(4))(2).6H(2)O to aqueous solutions of the bis(tetradentate) ligands T(2)-o-XAc(2) (1,2-bis((4-(carboxymethyl)-1,4,7-triazacyclonon-1-yl)methyl)benzene and T(2)-m-XAc(2) (1,3-bis((4-(carboxymethyl)-1,4,7-triazacyclonon-1-yl)methyl)benzene), respectively. In the binuclear complex, 3, three N donors from one macrocycle and two chlorides occupy the distorted square pyramidal Cu(II) coordination sphere. The complex features a long Cu...Cu separation (11.81 A) and intermolecular interactions that give rise to weak intermolecular antiferromagnetic coupling between Cu(II) centers. Complex 4 contains binuclear cations with a single hydroxo and p-nitrophenyl phosphate bridging two Cu(II) centers (Cu...Cu = 3.565(2) A). Magnetic susceptibility studies indicated the presence of strong antiferromagnetic interactions between the metal centers (J = -275 cm(-1)). Measurements of the rate of BNPP (bis(p-nitrophenyl) phosphate) hydrolysis by a number of these metal complexes revealed the greatest rate of cleavage for [Cu(2)(T(2)-o-X)(OH(2))(4)](4+) (k = 5 x 10(-6) s(-1) at pH = 7.4 and T = 50 degrees C). Notably, the mononuclear [Cu(Me(3)tacn)(OH(2))(2)](2+) complex induces a much faster rate of cleavage (k = 6 x 10(-5) s(-1) under the same conditions).     

Catecholase activity of a series of dicopper(II) complexes with variable Cu-OH(phenol) moieties

The catecholase activity of a series of dicopper(II) complexes containing different numbers of phenol groups coordinated to the metal centers was studied to identify functional as well as structural models for the type III copper enzymes tyrosinase and catechol oxidase. The syntheses and characterization of complexes [Cu(2)(H(2)bbppnol)(mu-OAc)(H(2)O)(2)]Cl(2).2H(2)O (1) and [Cu(2)(Hbtppnol)(mu-OAc)](ClO(4))(2) (2) were previously reported by us (Inorg. Chim. Acta 1998, 281, 111-115; Inorg. Chem. Commun. 1999, 2, 334-337), and complex [Cu(2)(P1-O(-))(OAc(-))](ClO(4))(2) (3) was previously reported by Karlin et al. (J. Am. Chem. Soc. 1997, 119, 2156-2162). The catalytic activity of the complexes 1-3 on the oxidation of 3,5-di-tert-butylcatechol was determined spectrophotometrically by monitoring the increase of the 3,5-di-tert-butyl-o-benzoquinone characteristic absorption band at about 400 nm over time in methanol saturated with O(2)/aqueous buffer pH 8 solutions at 25 degrees C. The complexes were able to oxidize 3,5-di-tert-butylcatechol to the corresponding o-quinone with distinct catalytic activity. A kinetic treatment of the data based on the Michaelis-Mentèn approach was applied. The [Cu(2)(H(2)bbppnol)(mu-OAc)(H(2)O)(2)]Cl(2) small middle dot2H(2)O complex showed the highest catalytic activity of the three complexes as a result of a high turnover rate (k(cat) = 28 h(-1)) combined with a moderate substrate-catalyst binding constant (K(ass) = 1.3 x 10(3) M(-1)). A mechanism for the oxidation reaction is proposed, and reactivity differences, k(cat)/K(M) of the complexes, were found to be dependent on (DeltaE)(1,2), the difference in the driving force for the reduction reactions Cu(II)(2)/Cu(II)Cu(I) and Cu(II)Cu(I)/Cu(I)(2).     

Rational assembly of soluble copper(II) phosphonates: synthesis, structure and magnetism of molecular tetranuclear copper(II) phosphonates

The reactions of the dinuclear copper complexes [Cu(2)(L)(OAc)] [H(3)L = N,N'-(2-hydroxypropane-1,3-diyl)bis(salicylaldimine) or [Cu(2)(L')(OAc)] (H(3)L' = N,N'-(2-hydroxypropane-1,3-diyl)bis(4,5-dimethylsalicylaldimine)] with various phosphonic acids, RPO(3)H(2) (R = t-Bu, Ph, c-C(5)H(9), c-C(6)H(11) or 2,4,6-i-Pr(3)-C(6)H(2)), leads to the replacement of the acetate bridge affording tetranuclear copper(II) phosphonates, [Cu(4)(L)(2)(t-BuPO(3))](CH(3)OH)(2)(C(6)H(6)) (1), [Cu(4)(L)(2)(PhPO(3))(H(2)O)(2)(NMe(2)CHO)](H(2)O)(2) (2), [Cu(4)(L')(2)(C(5)H(9)PO(3))](CH(3)OH)(2) (3), [Cu(4)(L')(2)(C(6)H(11)PO(3)](MeOH)(4)(H(2)O)(2) (4) and [Cu(4)(L')(2)(C(30)H(46)P(2)O(5))](PhCH(3)) (5). The molecular structures of 1-4 reveal that a [RPO(3)](2-) ligand is involved in holding the four copper atoms together by a 4.211 coordination mode. In 5, an in situ formed [(RPO(2))(2)O](4-) ligand bridges two pairs of the dinuclear subunits. Magnetic studies on these complexes reveal that the phosphonate ligand is an effective conduit for magnetic interaction among the four copper centers present; a predominantly antiferromagnetic interaction is observed at low temperatures.     

Coordination-position isomeric M(II)Cu(II) and Cu(II)M(II) (M = Co, Ni, Zn) complexes derived from macrocyclic compartmental ligands

The dinucleating macrocyclic ligands (L(2;2))(2-) and (L(2;3))(2-), comprised of two 2-[(N-methylamino)methyl]-6-(iminomethyl)-4-bromophenolate entities combined by the -(CH(2))(2)- chain between the two aminic nitrogen atoms and by the -(CH(2))(2)- or -(CH(2))(3)- chain between the two iminic nitrogen atoms, have afforded the following M(II)Cu(II) complexes: [CoCu(L(2;2))](ClO(4))(2).MeCN (1A), [NiCu(L(2;2))](ClO(4))(2) (2A), [ZnCu(L(2;2))](ClO(4))(2).0.5MeCN.EtOH (3A), [CoCu(L(2;3))(MeCN)(2-PrOH)](ClO(4))(2) (4A), [NiCu(L(2;3))](ClO(4))(2) (5A), and [ZnCu(L(2;3))](ClO(4))(2).1.5DMF (6A). [CoCu(L(2;2))(MeCN)(3)](ClO(4))(2) (1A') crystallizes in the monoclinic space group P2(1)/n, a = 11.691(2) A, b = 18.572(3) A, c = 17.058(3) A, beta= 91.18(2) degrees, V = 3703(1) A(3), and Z = 4. [NiCu(L(2;2))(DMF)(2)](ClO(4))(2) (2A') crystallizes in the triclinic space group P(-)1, a = 11.260(2) A, b = 16.359(6) A, c = 10.853(4) A, alpha= 96.98(3) degrees, beta= 91.18(2) degrees, gamma= 75.20(2) degrees, V = 1917(1) A(3), and Z = 2. 4A crystallizes in the monoclinic space group P2(1)/c, a = 15.064(8) A, b = 11.434(5) A, c = 21.352(5) A, beta= 95.83(2)degrees, V = 3659(2) A(3), and Z = 4. The X-ray crystallographic results demonstrate the M(II) to reside in the N(amine)(2)O(2) site and the Cu(II) in the N(imine)(2)O(2) site. The complexes 1-6 are regarded to be isomeric with [CuCo(L(2;2)))](ClO(4))(2).DMF (1B), [CuNi(L(2;2)))](ClO(4))(2).DMF.MeOH (2B), [CuZn(L(2;2)))](ClO(4))(2).H(2)O (3B)), [CuCo(L(2;3)))](ClO(4))(2).2H(2)O (4B), [CuNi(L(2;3)))](ClO(4))(2) (5B), and [CuZn(L(2;3)))](ClO(4))(2).H(2)O (6B) reported previously, when we ignore exogenous donating and solvating molecules. The isomeric M(II)Cu(II) and Cu(II)M(II) complexes are differentiated by X-ray structural, magnetic, visible spectroscopic, and electrochemical studies. The two isomeric forms are significantly stabilized by the "macrocyclic effect" of the ligands, but 1A is converted into 1B on an electrode, and 2A is converted into 2B at elevated temperature.     

Self-assembled dinuclear,trinuclear, tetranuclear,pentanuclear, and octanuclear Ni(II) complexes of a series of polytopic diazine based ligands: structural and magnetic properties

The nickel coordination chemistry of a series of polytopic diazine (N-N) based ligands has been examined. Self-assembly reactions lead to examples of dinuclear, trinuclear, tetranuclear, pentanuclear, and octanuclear complexes, all of which exhibit magnetic exchange coupling, with antiferromagnetic and ferromagnetic examples. Structural details are presented for [(L1)(2)Ni(2)(H(2)O)(2)](NO(3))(4).3H(2)O (1), [(L2)(2)Ni(3)(H(2)O)(2)](NO(3))(6).8H(2)O (2), [(L3)(4)Ni(4)(H(2)O)(8)] (NO(3))(4).8H(2)O (3), [(L4)(2)Ni(5)(H(2)O)(10)(NO(3))](NO(3))(7).8H(2)O (4), and [(L5)(4)Ni(8)(H(2)O)(8)](BF(4))(8).16H(2)O (5). Compound 1 crystallizes in the monoclinic system, space group P2(1)/c, with a = 14.937(1) A, b = 18.612(2) A, c = 20.583(2) A, beta = 108.862(2) degrees, Z = 4. Compound 2 crystallizes in the orthorhombic system, space group P2(1)2(1)2, with a = 21.771(4) A, b = 13.700(2) A, c = 20.017(3) A, Z = 4. Compound 3 crystallizes in the tetragonal system, space group P4(3), with a = 12.9483(7) A, c = 33.416(3) A, Z = 4. Compound 4 crystallizes in the triclinic system, space group P(-)1, with a = 12.6677(8) A, b = 18.110(1) A, c = 19.998(1) A, alpha = 100.395(1) degrees, beta = 109.514(1) degrees, gamma = 109.686(1) degrees, Z = 2. Compound 5 crystallizes in the monoclinic system, space group P2(1)/n, with a = 21.153(5) A, b = 35.778(9) A, c = 21.823(5) A, beta = 97.757(6) degrees, Z = 4. The linear trinuclear Ni(II) complex (2) has a cis-N-N single bond bridge, and a water bridge linking the central Ni(II) to each external Ni(II) center in each of two similar trinuclear subunits, and exhibits intramolecular ferromagnetic exchange (J = 5.0 cm(-1)). A novel octanuclear metallacyclic ring structure exists in 5, with trans-N-N single bond bridges linking adjacent Ni(II) centers, leading to quite strong intramolecular antiferromagnetic exchange (J = -30.4 cm(-1)).     

Binuclear copper(II) oxidation products from copper(I) complexes with tridentate ligands. Magnetostructural characterization

The bis-pyridine tridentate ligands (6-R-2-pyridylmethyl)-(2-pyridylmethyl) benzylamine (RDPMA, where R = CH(3), CF(3)), (6-R-2-pyridylmethyl)-(2-pyridylethyl) benzylamine (RPMPEA, where R = CH(3), CF(3)), and the bidentate ligand di-benzyl-(6-methyl-2-pyridylmethyl)amine (BiBzMePMA) have been synthesized and their copper(I) complexes oxidized in a methanol solution to afford self-assembled bis-micro-methoxo-binuclear copper(II) complexes (1, 2, 4, 6) or hydroxo- binuclear copper(II) complexes (3). Oxidation of the nonsubstituted DPMA (R = H) in dichloromethane gives a chloride-bridged complex (5). The crystal structures for [Cu(MeDPMA)(MeO)](2)(ClO(4))(2) (1), [Cu(RPMPEA)(MeO)](2)(ClO(4))(2) (for 2, R= Me, and for 4, R = CF(3)), [Cu(BiBzMePMA)(MeO)](2)(ClO(4))(2) (6), [Cu(FDPMA)(OH)](2)(ClO(4))(2) (3), and [Cu(DPMA)(Cl)](2)(ClO(4))(2) (5) have been determined, and their variable-temperature magnetic susceptibility has been measured in the temperature range of 10-300 K. The copper coordination geometries are best described as square pyramidal, except for 6, which is square planar, because of the lack of one pyridine ring in the bidentate ligand. In 1-4 and 6, the basal plane is formed by two pyridine N atoms and two O atoms from the bridging methoxo or hydroxo groups, whereas in 5, the bridging Cl atoms occupy axial-equatorial sites. Magnetic susceptibility measurements show that the Cu atoms are strongly coupled antiferromagnetically in the bis-methoxo complexes 1, 2, 4, and 6, with -2J > 600 cm(-)(1), whereas for the hydroxo complex 3, -2J = 195 cm(-)(1) and the chloride-bridged complex 5 shows a weak ferromagnetic coupling, with 2J = 21 cm(-)(1) (2J is an indicator of the magnetic interaction between the Cu centers).     

Characterization and dioxygen reactivity of a new series of coordinatively unsaturated thiolate-ligated manganese(II) complexes

The synthesis, structural, and spectroscopic characterization of four new coordinatively unsaturated mononuclear thiolate-ligated manganese(II) complexes ([Mn(II)(S(Me2)N(4)(6-Me-DPEN))](BF(4)) (1), [Mn(II)(S(Me2)N(4)(6-Me-DPPN))](BPh(4))·MeCN (3), [Mn(II)(S(Me2)N(4)(2-QuinoPN))](PF(6))·MeCN·Et(2)O (4), and [Mn(II)(S(Me2)N(4)(6-H-DPEN)(MeOH)](BPh(4)) (5)) is described, along with their magnetic, redox, and reactivity properties. These complexes are structurally related to recently reported [Mn(II)(S(Me2)N(4)(2-QuinoEN))](PF(6)) (2) (Coggins, M. K.; Kovacs, J. A. J. Am. Chem. Soc.2011, 133, 12470). Dioxygen addition to complexes 1-5 is shown to result in the formation of five new rare examples of Mn(III) dimers containing a single, unsupported oxo bridge: [Mn(III)(S(Me2)N(4)(6-Me-DPEN)](2)-(μ-O)(BF(4))(2)·2MeOH (6), [Mn(III)(S(Me2)N(4)(QuinoEN)](2)-(μ-O)(PF(6))(2)·Et(2)O (7), [Mn(III)(S(Me2)N(4)(6-Me-DPPN)](2)-(μ-O)(BPh(4))(2) (8), [Mn(III)(S(Me2)N(4)(QuinoPN)](2)-(μ-O)(BPh(4))(2) (9), and [Mn(III)(S(Me2)N(4)(6-H-DPEN)](2)-(μ-O)(PF(6))(2)·2MeCN (10). Labeling studies show that the oxo atom is derived from (18)O(2). Ligand modifications, involving either the insertion of a methylene into the backbone or the placement of an ortho substituent on the N-heterocyclic amine, are shown to noticeably modulate the magnetic and reactivity properties. Fits to solid-state magnetic susceptibility data show that the Mn(III) ions of μ-oxo dimers 6-10 are moderately antiferromagnetically coupled, with coupling constants (2J) that fall within the expected range. Metastable intermediates, which ultimately convert to μ-oxo bridged 6 and 7, are observed in low-temperature reactions between 1 and 2 and dioxygen. Complexes 3-5, on the other hand, do not form observable intermediates, thus illustrating the effect that relatively minor ligand modifications have upon the stability of metastable dioxygen-derived species.     

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.     

Synthesis, characterization, and photoresponsive properties of a series of Mo(IV)-Cu(II) complexes

Six Mo(IV)-Cu(II) complexes, [Cu(tpa)](2)[Mo(CN)(8)]·15H(2)O (1, tpa = tris(2-pyridylmethyl)amine), [Cu(tren)](2)[Mo(CN)(8)]·5.25H(2)O (2, tren = tris(2-aminoethyl)amine), [Cu(en)(2)][Cu(0.5)(en)][Cu(0.5)(en)(H(2)O)][Mo(CN)(8)]·4H(2)O (3, en = ethylenediamine), [Cu(bapa)](3)[Mo(CN)(8)](1.5)·12.5H(2)O (4, bapa = bis(3-aminopropyl)amine), [Cu(bapen)](2)[Mo(CN)(8)]·4H(2)O (5, bapen = N,N'-bis(3-aminopropyl)ethylenediamine), and [Cu(pn)(2)][Cu(pn)][Mo(CN)(8)]·3.5H(2)O (6, pn = 1,3-diaminopropane), were synthesized and characterized. Single-crystal X-ray diffraction analyses show that 1-6 have different structures varying from trinuclear clusters (1-2), a one-dimensional belt (3), two-dimensional grids (4-5), to a three-dimensional structure (6). Magnetic and ESR measurements suggest that 1-6 exhibit thermally reversible photoresponsive properties on UV light irradiation through a Mo(IV)-to-Cu(II) charge transfer mechanism. A trinuclear compound [Cu(II)(tpa)](2)[Mo(V)(CN)(8)](ClO(4)) (7) was synthesized as a model of the photoinduced intermediate.     

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).