Trinuclear CuII Complexes Research Articles

Synthesis of trinuclear CuII-complex with tris(4-triphenylmethylphenoxy)-substituted hemihexaphyrazine and radioprotective properties of its water-soluble form

A condensation of 2,5-diamino-1,3,4-thiadiazole with the products of the in situ reaction of 1,2-dicyano-4-(4-triphenylmethylphenoxy)benzene with sodium alkoxides in a mixture of butanol—methanol furnished a trisubstituted ABABAB-type macroheterocycle (hemihexaphyrazine). A 3 : 1 trinuclear complex was synthesized by the reaction of the macrocycle with copper(II) acetate. The compounds obtained were characterized by IR spectroscopy, UV-vis spectroscopy, mass spectrometry, as well as by elemental analysis. Radioprotective properties of the water-soluble form of the complex were studied

μ3‐ vs. μ‐Hydroxido Bridges – Peripheral Function Controls the Nuclearity of Hydroxido‐Bridged Copper(II) Complexes

AbstractThe synthesis and characterization of three monohydroxido‐bridged dinuclear CuII complexes, [{Cu2(L1)2(μ‐OH)}(ClO4){Cu2(L1)2(μ‐OH)}](ClO4)·5.5H2O (1), Cu2(L2)2(OH)(ClO4)(H2O)2 (2), [{Cu2(L3)2(μ‐OH)(ClO4)}2]·5H2O (3) and three monohydroxido‐bridged trinuclear CuII complexes, [Cu3(L4)3(μ3‐OMe)(ClO4)2] (4), [Cu3(L5)3(μ3‐OH) (ClO4)2]·0.5{(CH3)2CO}·0.5(H2O) (5), [Cu3(L6)3(μ3‐OH)(ClO4)2] (6), is reported (HL1–HL6 = tridentate N2O ligands resulting from the Schiff base condensation of salicylaldehyde or 3‐methoxysalicylaldehyde with ethylenediamine, 1,2‐diaminopropane, 2‐methylpropane‐1,2‐diamine or 1,2‐diaminocyclohexane). The six new complexes are obtained through aggregation of the corresponding mononuclear precursor Cu(Li)(py)(ClO4) in the presence of HO– (MeO–) anions in methanol. The nuclearity of the resulting complex depends on the steric requirement of Li: in the presence of an OMe substituent α to the Ophenoxido atom (L1–L3), μ‐HO– single‐bridged dinuclear compounds are obtained (1–3); in the absence of an α‐substituent (L4–L6), the aggregation proceeds to the μ3‐OH– (μ3‐OMe–) bridged trinuclear compounds 4–6. The molecular structures of 1, 3 and 4–6 have been established through single‐crystal X‐ray studies. Antiferromagnetic interactions operate in 1 (J = –57 cm–1, –2JS1S2 formalism), 2 is paramagnetic, and 3 is the first example of a ferromagnetic monohydroxido‐bridged dinuclear CuII complex (J = 16 cm–1). The structural and magnetic parameters for the 22 μ‐HO– single‐bridged dinuclear CuII compounds reported to date are compared. Antiferromagnetic interactions operate in all three monohydroxido‐bridged trinuclear CuII complexes 4, 5, and 6 (J = –16.9, –6.3, and –6.7 cm–1, respectively). The structural and magnetic parameters for the seven μ3‐hydroxido (methoxido) bridged trinuclear CuII compounds presently known in the series based on tridentate Schiff bases that result from condensation of diamines with salicylaldehydes are compared.

CuII Complexes of Isomeric Ligands Derived from 2-Pyridine-carboxaldehyde and m- or p-Xylylenediamine: An Intermolecularly ?-Stacked Dinuclear Species and a Trinuclear Circular Helicate that Encapsulates a Chloride Ion

Di- and trinuclear CuII complexes [Cu2L1(2,2′-bipyridine)2Cl2]Cl2·11H2O and [Cu3(L2)3Cl3]Cl3·1.25MeOH·4H2O incorporating the isomeric Schiff base ligands 1,1′-(1,4-phenylene)bis(N-(pyridin-2-ylmethylene)methanamine) (L1) and 1,1′-(1,4-phenylene)bis(N-(pyridin-2-ylmethylene)methanamine) (L2), each incorporating two separated α-diimine coordination domains, have been synthesised and their X-ray crystal structures and variable temperature magnetic properties determined. The X-ray crystal structure of [Cu2L1(2,2′-bipyridine)2Cl2]Cl2·11H2O shows that each CuII centre is bound to two nitrogen atoms from L1, two from a bipyridine ligand, and a chloride anion. Intramolecular π-stacking interactions are present between the central phenyl ring of L1 and both rings of each bipyridine ligand. The structure of [Cu3(L2)3Cl3]Cl3·1.25MeOH·4H2O shows an unusual trinuclear circular helicate arrangement with approximate C3-symmetry. A chloride anion is encapsulated in the structure being bound by six non-classical hydrogen bond interactions. Variable temperature magnetic susceptibility measurements indicated the presence of weak antiferromagnetic behaviour for [Cu2L1(2,2′-bipyridine)2Cl2]Cl2·11H2O and weak ferromagnetic behaviour for [Cu3(L2)3Cl3]Cl3·1.25MeOH·4H2O.

Linear Trinuclear Copper(II) Complexes Derived from the Nucleophilic Addition Products of Dicyanonitrosomethanide [C(CN)2(NO)]–: Syntheses, Structures, and Magnetic Properties

Two novel trinuclear CuII complexes have been synthesised from the nucleophilic addition derivatives of the small cyano anion, dicyanonitrosomethanide (dcnm). The reaction of CuII with the water adduct ligand, carbamoylcyanonitrosomethanide (ccnm) and teaH3 (triethanolamine) in a basic MeOH/MeCN solution results in the formation of [Cu3(acnm)2(teaH2)2]·2MeOH (1) (acnm = amidocarbonyl(cyano)nitrosomethanide and teaH2– = singly deprotonated triethanolamine). The reaction of CuII with dicyanonitrosomethanide (dcnm) and m-xylenediamine in a basic MeOH/MeCN solution results in the formation of [Cu3(cimm)2(a3acnm)2]·6MeCN (2) (cimm = cyano(imido(methoxy)methyl)nitrosomethanide and a3acnm = {amino(3-aminomethylphenyl)methylimino}methyl(cyanonitrosomethanide)). Both complexes display linear trinuclear CuII metallic cores. Solid state DC magnetic susceptibility studies were performed on 1 and 2. Compound 1 revealed very strong antiferromagnetic interactions between central and terminal Cu atoms, while compound 2 displayed ferromagnetic interactions because of the orthogonal relationship of the terminal and the central ‘magnetic’ orbitals, which contrasts with these orbitals being coplanar in 1 thus providing strong superexchange pathways involving Cu-N-O-Cu moieties.

Di-μ-chlorido-1:2κ2Cl,2:3κ2Cl-tetrachlorido-1κCl,2κ2Cl,3κCl-bis[N,N′′-bis(2-furylmethylene)diethylenetriamine]-1κ3N,N′,N′′;3κ3N,N′,N′′-tricopper(II)

The complete title trinuclear CuII complex, [Cu3Cl6(C14H16N3O2)2], is generated by twofold symmetry with one Cu atom lying on the rotation axis. The central Cu atom adopts a distorted tetra­hedral CuCl4 geometry. The terminal Cu atom is five-coordinated in a distorted square-pyramidal coordination environment consisting of three N atoms of the ligand, one bridging Cl atom and one terminal Cl atom. Inter­molecular C—H⋯Cl hydrogen bonds help to establish the packing.

Synthesis and Characterization of a Novel Quinoxaline-Substituted vic-Dioxime and Its Complexes Containing Bis(12-Diazacrown-4) Derivatives

Abstract A new quinoxaline-substituted vicinal dioxime ligand containing bis(12-diazacrown-4) units (H2L) was synthesized by the reaction of cyanogen di-N-oxide with compound 4. Mononuclear NiII and CuII complexes with a metal:ligand ratio of 1:2 for H2L and a trinuclear CuII complex were also synthesized. The mononuclear CuII species coordinated to two CuII ions through the deprotonated oximate oxygens to yield a trinuclear structure cis-bridged by the oximate groups, with 1,10-phenanthroline as an end-cap ligand. The mononuclear CoIII complex of H2L was isolated with pyridine and chlorine as axial ligands. In addition, a CoIII complex containing the BF2+ bridge macrocycle was synthesized using a precursor hydrogen-bridged CoIII complex via a template effect. The extraction abilities of 1, 3, and 11 were also evaluated in 1,2-dichloroethane by using several alkali (Li+, Na+, K+, and Cs+) and transition-metal picrates, such as Ag+, Pb2+, Cd2+, Cu2+, and Zn2+. Structures of the ligands and metal complexes were solved by elemental analyses, 1H and 13C NMR, FT-IR, UV–vis, and mass spectra.

CuII and ZnII Coordination Chemistry of Pyrazole‐Containing Polyamine Receptors − Influence of the Hydrocarbon Side Chain Length on the Metal Coordination

AbstractThe synthesis of a new macrocyclic receptor (L4) containing two 3,5‐dimethylpyrazole units connected by dipropylenetriamine bridges is reported for the first time; pH‐metric titrations indicate that L4 shows six protonation steps in the pH range 2−11. In the absence of metal ions, the pyrazole moieties are not involved in acid‐base processes in this pH range. Addition of CuII and ZnII results in deprotonation of the pyrazole moieties which act as bis(monodentate) η1:η1 ligands. This induced deprotonation occurs at higher pH values than in the complexes of the analogous ligand containing diethylenetriamine bridges (L1). The crystal structures of [Cu2(H−2L4)](ClO4)2 and [Zn2(H−2L4)](ClO4)2 obtained by treatment of Na2[H−2L4] with either Cu(ClO4)2·6H2O or Zn(ClO4)2·6H2O in methanol followed by recrystallisation from water/methanol also show the deprotonation of the pyrazole moieties. The coordination geometry around each metal ion is square‐pyramidal and involves all nitrogen atoms of the macrocycle. The crystal structure of [Zn2(H−2L1)](ClO4)2 shows full involvement of all the nitrogen atoms of the macrocycle in the coordination to the metal ions. The coordination geometry can be defined as midway between a square pyramid and an irregular trigonal bipyramid. Treatment of neutral L4 in methanol with Cu(ClO4)2·6H2O yields a blue complex which, after heating in boiling water, crystallises as a red compound. Elemental microanalyses, ESI‐MS and FAB‐MS data of both forms of this complex are consistent with the formula [Cu2L4](ClO4)4·2H2O. Furthermore, these data along with the paramagnetic 1H NMR spectrum of the red form of the compound suggest a structure in which the pyrazole rings are deprotonated while the central nitrogen atoms of the bridging chains are protonated and consequently uncoordinated. The change from the blue (square‐pyramidal) to the red form (square‐planar) can be ascribed to dissociation of the water molecules which occupy the axial positions in the CuII coordination spheres of the blue form. The variation of the magnetic susceptibility of the red complex [Cu2L4](ClO4)4·2H2O and the complex [Cu2(H−2L4)](ClO4)2 with temperature has been studied in the 2−300 K temperature range. Fitting of the experimental data provides J values which are among the highest found for doubly pyrazolate‐bridged dicopper(II) complexes {J = −299 cm−1 for red‐[Cu2L4](ClO4)4·2H2O and J = −286 cm−1 for [Cu2(H−2L4)](ClO4)2}. A trinuclear CuII complex of formula [Cu3(H−2L4)](ClO4)4·2MeOH was also isolated after treatment of L4 with Cu(ClO4)2·6H2O solutions of higher concentration. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Heptapyridinebis(μ-dimethylglyoximato)tricopper(II) diperchlorate: a novel trinuclear copper complex bridged by glyoximate groups

The title compound, [Cu3(C4H6N2O2)2(C5H5N)7](ClO4)2, is a trinuclear CuII complex bridged by two glyoximate groups. The central Cu and the pyridine N atom bonded to it lie on a twofold axis. The geometry around each Cu atom is a distorted square pyramid.

New oxamato-bridged trinuclear Cu(II)-Cu(II)-Cu(II) complexes with hydrogen-bond supramolecular structures: synthesis and magneto-structural studies.

Three oxamato-bridged copper(II) complexes of formula [(Cu(H(2)O)(tmen)Cu(tmen))(mu-Cu(H(2)O)(Me(2)pba))](n)((PF(6))(2))(n).2nH(2)O (1), [(Cu(H(2)O)(tmen)Cu(NCS)(tmen))(mu-Cu(H(2)O)(Me(2)pba))](2)(ClO(4))(2).4H(2)O (2), and [(Cu(H(2)O)(tmen)Cu(NCS)(tmen))(mu-Cu(H(2)O)(Me(2)pba))](2)(PF(6))(2).4H(2)O (3), where Me(2)pba = 2,2-dimethyl-1,3-propylenebis(oxamato) and tmen = N,N,N',N'-tetramethylethylenediamine, have been synthesized and characterized. Their crystal structures were solved. Complex 1 crystallizes in the monoclinic system, space group P2(1), with a = 15.8364(3) A, b =8.4592(2) A, c = 15.952 A, beta = 101.9070(10) degrees, and Z = 2. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 6.69530(10) A, b = 18.2441(3) A, c = 31.6127(5) A, beta = 90.1230(10) degrees, and Z = 4. Complex 3 crystallizes in the monoclinic system, space group P2(1)/c, with a = 6.68970(10) A, b = 18.150 A, c = 32.1949(4) A, beta = 90.0820(10) degrees, and Z = 4. The three complexes have a central core in common: a trinuclear Cu(II) complex with the two terminal Cu(II) ions blocked by N,N,N',N'-tetramethylethylenediamine. The structure of complex 1 consists of trinuclear cationic entities connected by hydrogen bonds to produce a supramolecular one-dimensional array. The structure of complexes 2 and 3 consist of trinuclear cationic entities linked by pairs by hydrogen bonds between the water molecule of the central Cu(II) and one oxygen atom of the oxamato ligand of the neighboring entity, forming a hexanuclear complex. The magnetic properties of the three complexes were studied by susceptibility vs temperature measurement. For complexes 1-3 the fit was made by the irreducible tensor operator (ITO). The values obtained were J(1) = -386.48 cm(-1) and J(2) = 1.94 cm(-1) for 1, J(1) = -125.77 cm(-1) and J(2) = 0.85 cm(-1) for 2, and J(1) = -135.50 cm(-1) and J(2) = 0.94 cm(-1) for 3. In complex 1, the coordination polyhedron of the terminal Cu(II) atoms can be considered as square pyramidal; the apical positions are filled by the oxygen atom from a water molecule in the former and a F atom of the hexafluorophosphate anion in the latter showing a quasi-planar [Cu(CuMe(2)pba)Cu] network. For complexes 2 and 3, the square pyramidal environment of the terminal Cu(II) ions was strongly modified. To our knowledge, this is the first time that the longest distance (apical) in complexes with oxamato derivatives and bidentate amines as blocking ligands has been reported in one of the oxamato arms. The great difference in J(1) values between 1 and the other two complexes is interpreted as an orbital reversal of the magnetic orbitals of the terminal Cu(II) ions in 2 and 3.

Synthesis, characterization, and magnetic properties of new complexes based on self-assembled homotrinuclear units CuII–CuII–CuII

Three new supramolecular entities of CuII have been synthesized and characterized: [Cu2(H2O)2(tmen)2(μ-Cu(H2O)(pba))](PF6)2 (1), [{Cu2(H2O)(tmen)2(μ-Cu(pba))}(μ-SeCN)]n(ClO4)n·2nH2O (2) and [{Cu2(H2O)(tmen)2(μ-Cu(pba))}(μ-SeCN)]n(PF6)n·2nH2O (3), where pba = 1,3-propanediylbis(oxamato) and tmen = N,N,N′N′-tetramethylethylenediamine. The crystal structures of 1 and 2 were solved. Complex 1 is the precursor of 3; complex 2 is derived from the ClO4− analogue of 1. The two complexes have a central core in common: a trinuclear CuII complex with the two terminal CuII ions blocked by N,N,N′N′-tetramethylethylenediamine and with the same environment in the CuII central atom. In the case of complex 1, the structure is a double chain of trinuclear entities linked by hydrogen bonds owing to coordinated water molecules. In the case of complex 2, the selenocyanate ligands produce intermolecular linkages giving a one-dimensional system. The counter anions PF6− and ClO4− do not participate directly in the formation of the supramolecular entities. For complex 3 we propose a one-dimensional structure such as found for complex 2. The magnetic properties of the three complexes were studied by susceptibility measurements vs. temperature; a fit was made by the irreducible tensor formalism (ITO). The values obtained were: J1 = −342.1 cm−1, J2 = 0.61 cm−1 for 1, J1 = −282.2 cm−1, J2 = 2.6 cm−1 for 2 and J1 = −245.4 cm−1, J2 = 1.3 cm−1 for 3.

Mono and trinuclear complexes of alpha-oximinoacetoacetylpyridine-4-phenylthiosemicarbazone.

Complexes of several transition metal ions with alpha-oximinoacetoacetyl pyridine-4-phenylthiosemicarbazone (H3OAPT) have been prepared. Attempts were made to elucidate their geometries by elemental analysis, molar conductance, magnetic measurements and by some spectroscopic (IR, ESR and electronic) techniques. All the investigated metal ions form mononuclear complexes except for CuII, which forms mononuclear and trinuclear complexes with its chloride and acetate salts, respectively. The IR spectra show that the ligand behaves as a mono or binegative tridentate. Moreover, it acts as a trinegative hexadentate in the trinuclear CuII complex. The protonation constants (logK1H = 9.9 and log K2H = 6.0), as well as the stability constants of the metal complexes, are determined by the pH-titration of H3OAPT and its metal(II) complexes against 0.01 M NaOH. CuII complexes possess square-planar stereochemistry while CoII and NiII have an octahedral one. The crystal field parameters of CoII and NiII complexes are evaluated.

A Unique Copper-Controlled Template Synthesis of Tetradentate N4-Donor Ligands and Their Propeller-Type Linear Trinuclear CuII Complexes

In situ reaction of CuII triflate with aminopyridine or aminopyrimidine and triethylorthoformate in ethanol results in unique linear trinuclear CuII complexes with the general formula [Cu3(L−)4](CF3SO3)2(EtOH)x (L = dehydronated ligand N,N′-bis(pyridine-2-yl)formamidine or the new ligand N,N′-bis(pyrimidine-2-yl)formamidine). The structure [Cu−Cu−Cu angle 175.19(2)°] consists of four nearly flat molecules of the ligand which contribute to the propeller-type structure around the Cu−Cu−Cu axis. A strong antiferromagnetic interaction between the CuII ions is observed, resulting in an S = 1/2 ground state below 100 K.

A Unique Copper-Controlled Template Synthesis of Tetradentate N4-Donor Ligands and Their Propeller-Type Linear Trinuclear CuII Complexes

In situ reaction of CuII triflate with aminopyridine or aminopyrimidine and triethylorthoformate in ethanol results in unique linear trinuclear CuII complexes with the general formula [Cu3(L−)4](CF3SO3)2(EtOH)x (L = dehydronated ligand N,N′-bis(pyridine-2-yl)formamidine or the new ligand N,N′-bis(pyrimidine-2-yl)formamidine). The structure [Cu−Cu−Cu angle 175.19(2)°] consists of four nearly flat molecules of the ligand which contribute to the propeller-type structure around the Cu−Cu−Cu axis. A strong antiferromagnetic interaction between the CuII ions is observed, resulting in an S = 1/2 ground state below 100 K.