High thermodynamic stability and extraordinary kinetic inertness of copper(II) complexes with 1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid): example of a rare isomerism between kinetically inert penta- and hexacoordinated copper(II) complexes

In an aqueous solution at room temperature, 1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) (H(4)L(1)) and Cu(I) (I) form a pentacoordinated (pc) complex, pc-[Cu(L(1))](2-), exhibiting conformation I of the cyclam ring. At high temperature, the complex isomerises to a hexacoordinated isomer, trans-O,O-[Cu(L(1))](2-), with a trans-III conformation of the cyclam ring. In pc-[Cu(L(1))](2-), four ring nitrogen atoms and one phosphonate oxygen atom are arranged around Cu(I) (I) in a structure that is half-way between a trigonal bipyramid and a tetragonal pyramid, with one phosphonic acid group uncoordinated. In the trans-O,O-[Cu(L(1))](2-) isomer, the nitrogen atoms form a plane and the phosphonic acid groups are in a mutually trans configuration. A structurally very similar ligand, 4-methyl-1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) (H(4)L(2)), forms an analogous pentacoordinated complex, pc-[Cu(L(2))](2-), at room temperature. However, the complex does not isomerise to the octahedral complex analogous to trans-O,O-[Cu(L(1))](2-). Because of the high thermodynamic stability of pc-[Cu(L(1))](2-), (logbeta=25.40(4), 25 degrees C, I=0.1 mol dm(-3) KNO(3)) and the formation of protonated species, Cu(I) (I) is fully complexed in acidic solution (-log [H(+)] approximately 3). Acid-assisted decomplexation of both of the isomers of [Cu(H(2)L(1))] takes place only after protonation of both uncoordinated oxygen atoms of each phosphonate moiety and at least one nitrogen atom of the cycle. The exceptional kinetic inertness of both isomers is illustrated by their half-lives tau(1/2)=19.7 min for pc-[Cu(H(2)L(1))] and tau(1/2) about seven months for trans-O,O-[Cu(H(2)L(1))] for decomplexation in 5 M HClO(4) at 25 degrees C. The mechanism of formation of pc-[Cu(L(1))](2-) is similar to those observed for other macrocyclic complexes.     

Coordination properties of cyclam (1,4,8,11-tetraazacyclotetradecane) endowed with two methylphosphonic acid pendant arms in the 1,4-positions

The title ligand, 1,4,8,11-tetraazacyclotetradecane-1,4-diyl-bis(methylphosphonic acid) (H4te2p1,4, H4L), was prepared by an optimized synthetic approach and its complexing properties towards selected metal ions were studied by means of potentiometry. The ligand forms a very stable complex with copper(II) (log beta(CuL) = 27.21), with a high selectivity over binding of other metal ions (e.g. log beta(ZnL) = 20.16, log beta(NiL) = 21.92). The crystal structures of two intermediates in the ligand synthesis and two forms of the nickel(II) complex (obtained by crystallization at different pH) were determined. From acid solution, the crystals of trans-O,O-[Ni(H3L)]Cl.H2O were isolated. In such complex species, one phosphonate pendant arm is double- and the second arm is monoprotonated. The isolation of such species demonstrates a high kinetic inertness of the complex. The central metal ion is surrounded by four in-plane nitrogen atoms (in the ring configuration III) and two oxygen atoms of pendant moieties in the apical positions of octahedral coordination sphere. From neutral solution, the crystals of (trans-O,O-[Ni(H2L)])3.5H2O were isolated. The molecular structures of the complex units found in this structure are analogous to that found in trans-O,O-[Ni(H3L)]Cl.H2O.     

Oxygen activation by nonheme iron(II) complexes: alpha-keto carboxylate versus carboxylate

Mononuclear iron(II) alpha-keto carboxylate and carboxylate compounds of the sterically hindered tridentate face-capping ligand Tp(Ph2) (Tp(Ph2) = hydrotris(3,5-diphenylpyrazol-1-yl)borate) were prepared as models for the active sites of nonheme iron oxygenases. The structures of an aliphatic alpha-keto carboxylate complex, [Fe(II)(Tp(Ph2))(O(2)CC(O)CH(3))], and the carboxylate complexes [Fe(II)(Tp(Ph2))(OBz)] and [Fe(II)(Tp(Ph2))(OAc)(3,5-Ph(2)pzH)] were determined by single-crystal X-ray diffraction, all of which have five-coordinate iron centers. Both the alpha-keto carboxylate and the carboxylate compounds react with dioxygen resulting in the hydroxylation of a single ortho phenyl position of the Tp(Ph2) ligand. The oxygenation products were characterized spectroscopically, and the structure of the octahedral iron(III) phenolate product [Fe(III)(Tp(Ph2))(OAc)(3,5-Ph(2)pzH)] was established by X-ray diffraction. The reaction of the alpha-keto carboxylate model compounds with oxygen to produce the phenolate product occurs with concomitant oxidative decarboxylation of the alpha-keto acid. Isotope labeling studies show that (18)O(2) ends up in the Tp(Ph2) phenolate oxygen and the carboxylate derived from the alpha-keto acid. The isotope incorporation mirrors the dioxygenase nature of the enzymatic systems. Parallel studies on the carboxylate complexes demonstrate that the oxygen in the hydroxylated ligand is also derived from molecular oxygen. The oxygenation of the benzoylformate complex is demonstrated to be first order in metal complex and dioxygen, with activation parameters DeltaH++ = 25 +/- 2 kJ mol(-1) and DeltaS++ = -179 +/- 6 J mol(-1) K(-1). The rate of appearance of the iron(III) phenolate product is sensitive to the nature of the substituent on the benzoylformate ligand, exhibiting a Hammett rho value of +1.3 indicative of a nucleophilic mechanism. The proposed reaction mechanism involves dioxygen binding to produce an iron(III) superoxide species, nucleophilic attack of the superoxide at the alpha-keto functionality, and oxidative decarboxylation of the adduct to afford the oxidizing species that attacks the Tp(Ph2) phenyl ring. Interestingly, the alpha-keto carboxylate complexes react 2 orders of magnitude faster than the carboxylate complexes, thus emphasizing the key role that the alpha-keto functionality plays in oxygen activation by alpha-keto acid-dependent iron enzymes.     

Synthesis and Crystal structure of [（Praseodymium）2（3,5—Binitro benzoyloxy）6（Dimethyl Sulfoxide）4]Complex

1 INTRODUCTION The polynuclear lanthanide complexes are specially interested and widely applied in the researches on light, electricity and magnetism[1～4], and the studies of the synthesis of polynuclear lanthanide complexes and its applications tend to be growing rapidly nowadays. Herein a report on the synthesis process and crystal structure of the title complex is presented. The crystal structure showed it is a non-electrolyte complex with one- dimensional chain. OCCOOPrOOCPr…     

Selective tin-carbon bond cleavage reactions of trimethylstannylzirconocene dichloride with electrophiles

The reaction of 5,5-bis(trimethylstannyl)cyclopentadiene with CpZrCl3 (Cp = eta 5-C5H5) affords the monostannylated metallocene complex (eta 5-Me3SnC5H4)CpZrCl2 (1), accompanied by variable amounts of (eta 5-ClMe2SnC5H4)CpZrCl2 (2). The complex (1) reacts with BCl3 or with ICl to afford 2 (Sn-CH3 cleavage), but with HCl, Cp2ZrCl2 is obtained instead (Sn-Cp cleavage). Depending on the reaction conditions, treatment of either 1 or 2 with BBr3 affords (eta 5-BrMe2SnC5H4)CpZrBr2 (3) or (eta 5-Br2MeSnC5H4)CpZrBr2 (4). The reaction of 1 with excess I2 affords the iodostannylated complex (eta 5-IMe2SnC5H4)CpZrCl2 (5). Two of the complexes (2.2C6H5CH3 and 4.THF) are crystallographically characterized. The adduct 4.THF has a distorted trigonal bipyramidal geometry about tin with a long O-Sn distance of 2.655 A. We find overall that Me3Sn substituents undergo electrophilic halodemethylation much more readily than corresponding Me3Si substituents, whereas the reactivities of the halostannylated complexes toward nucleophiles such as airborne moisture are much lower than those of their halosilylated counterparts.     

A Copper（Ⅱ）-cadmium（Ⅱ） Heterometallic Hexanuclear Complex：[Cd_4Cu_2（pdc）_4（H_2O）_（14）]（H_3pdc=3,5-Pyrazoledicarboxylic Acid）

The title complex 1,[Cd 4 Cu 2 (pdc) 4 (H 2 O) 14 ] (H 3 pdc=3,5-pyrazoledicarboxylic acid),has been solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction.Complex 1 crystallizes in triclinic,space group P1 with a=0.67235(10),b=1.27935(18),c=1.28569(17) nm,α=112.633(2),β=102.971(3),γ=97.089(2)o,V=0.9673(2) nm 3,C 20 H 32 Cd 4 Cu 2 N 8 O 30,M r=1441.22,D c=2.474 g/cm 3,μ(MoKα)=3.356 mm 1,F(000)=698,S=1.003,Z=1,the final R=0.0471 and wR=0.0748 for I > 2σ(Ⅰ).In 1,two deprotonated 3,5-pyrazoledicarboxylic acids (pdc 3),one copper(Ⅱ) ion and one cadmium(Ⅱ) ion firstly form a pyrazole-bridged Cu II Cd II dinuclear unit,two of which related by an inversion center are connected by another two cadmium(Ⅱ) ions through chelating carboxylate groups to construct the copper(Ⅱ)-cadmium(Ⅱ) heterometallic hexanuclear complexes.Plenty of hydrogen bond interactions existing in the system further lead to a three-dimensional (3D) supramolecular framework.     

The first hexanuclear copper(I) carboxylate: X-ray crystal structure and reactivity in solution and gas-phase reactions

The carboxylate ligand-exchange reaction of copper(I) trifluoroacetate by 3,5-difluorobenzoate yielded a new product, [Cu(O2C(3,5-F)2C6H3)] (1). Single crystals of 1 suitable for X-ray structural characterization were obtained by sublimation-deposition procedures at 230 degrees C. An X-ray diffraction study revealed a remarkable planar hexanuclear copper(I) core supported by bridging carboxylates, the first such structural type among other known copper(I) carboxylates. The Cu...Cu distances within the core range from 2.7064(8) to 2.8259(8) A and fall into the category of cuprophillic interactions. The hexacopper unit remains intact upon gas-phase deposition with a planar polyarene, coronene (C24H12), to give [Cu6(O2C(3,5-F)2C6H3)6](C24H12) (2). Density functional theory calculations suggest the latter compound to be a cocrystallization product having electrostatic interactions between the hexacopper complex and coronene. However, cocrystallization affects the photophysical properties of 2. While copper(I) 3,5-difluorobenzoate (1) exhibits photoluminescence at ca. 554 nm (lambda(ex) = 350 nm) in the solid state, compound 2 is nonluminescent at room temperature in the visible region. Gas-phase and solution reactions of 1 with alkyne ligands, diphenylacetylene (C14H10) and 1,4-bis(p-tolylethynyl)benzene (C24H18), result in the rupture of the [Cu6] core to afford dinuclear organometallic copper(I) complexes. The latter have a dimetal core cis-bridged by two carboxylate groups with acetylene ligands eta(2)-coordinated to each copper(I) center.     

THE CRYSTAL STRUCTURES OF AMMONIUM AND SODIUM 2-AMINO-3,5-DICHLOROBENZOATES

Abstract

The crystal structures of ammonium and sodium 2-amino-3,5-dichlorobenzoates were determined by the X-ray diffraction method. The ammonium salt crystallizes in the monoclinic system (space group P2₁/c) with a = 13.941(3), b = 9.128(3), c = 7.349(2) Å, β = 90.80(3)° and Z = 4. The structure consists of an ammonium cation hydrogen bonded to a carboxylate oxygen of the 2-amino-3,5-dichlorobenzoate anion. The sodium salt of 2-amino-3,5-dichlorobenzoic acid crystallizes in the triclinic system (space group P 1) with a = 8.033(2), 6 = 8.944(2), c = 17.350(3) Å, α = 76.72(3)°, β = 79.69(3)°, γ = 72.54(3)° and Z = 4. The compound is a polymer in which the sodium ions are coordinated by carboxylate oxygen atoms of the organic ligand and water molecules in an octahedral arrangement. IR spectra of the salts are discussed.     

Antiferromagnetic three-dimensional order induced by carboxylate bridges in a two-dimensional network of [Cu3(dcp)2(H2O)4] trimers

A new Cu(II) complex, [Cu(3)(dcp)(2)(H(2)O)(4)](n), with the ligand 3,5-pyrazoledicarboxylic acid monohydrate (H(3)dcp) has been prepared by hydrothermal synthesis, and it crystallizes in the monoclinic space group P2(1)/c with a = 11.633(2) A, b = 9.6005(14) A, c = 6.9230(17) A, beta = 106.01(2) degrees, and Z = 2. In the solid state structure of [Cu(3)(dcp)(2)(H(2)O)(4)](n), trinuclear [Cu(3)(dcp)(2)(H(2)O)(4)] repeating units in which two dcp(3-) ligands chelate the three Cu(II) ions with the central Cu(II) ion, Cu(1) (on an inversion center), link to form infinite 2D sheets via syn-anti equatorial-equatorial carboxylate bridges between Cu(2) atoms in adjacent trimers. These layers are further linked by syn-anti axial-equatorial carboxylate bridging between Cu(1) atoms in adjacent sheets resulting in the formation of a crystallographic 3D network. A detailed analysis of the magnetic properties of [Cu(3)(dcp)(2)(H(2)O)(4)](n) reveals that the dcp(3-) ligand acts to link Cu(II) centers in three different ways with coupling constants orders of magnitude apart in value. In the high temperature region above 50 K, the dominant interaction is strongly antiferromagnetic (J/k(B) = -32 K) within the trimer units mediated by the pyrazolate bridges. Below 20 K, the trimer motif can be modeled as an S = 1/2 unit. These units are coupled to their neighbors by a ferromagnetic interaction mediated by the syn-anti equatorial-equatorial carboxylate bridge. This interaction has been estimated at J(2D)/k(B) = +2.8 K on the basis of a 2D square lattice Heisenberg model. Finally, below 3.2 K a weak antiferromagnetic coupling (J(3D)/k(B) = -0.1 K) which is mediated by the syn-anti axial-equatorial carboxylate bridges between the 2D layers becomes relevant to describe the magnetic (T, H) phase diagram of this material.     

Solvent deuterium kinetic isotope effects for the methanolyses of neutral C=O, P=O and P=S esters catalyzed by a triazacyclododecane : Zn(2+)-methoxide complex

The methanolyses of several organophosphate/phosphonate/phosphorothioate esters (O,O-diethyl O-(4-nitrophenyl) phosphate, paraoxon, ; O,O-diethyl S-(3,5-dichlorophenyl) phosphorothioate, ; O-ethyl O-(2-nitro-4-chlorophenyl) methylphosphonate, ; O,O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate, fenitrothion, ; O-ethyl S-(3,5-dichlorophenyl) methylphosphonothioate ) and a carboxylate ester (p-nitrophenyl acetate, ) catalyzed by methoxide and the Zn(2+)((-)OCH(3)) complex of 1,5,9-triazacyclododecane ( : Zn(2+)((-)OCH(3))) were studied in methanol and d(1)-methanol at 25 degrees C. In the case of the methoxide reactions inverse skie's were observed for the series with values ranging from 2 to 1.1, except for where the k(D)/k(H) = 0.90 +/- 0.02. The inverse k(D)/k(H) values are consistent with a direct nucleophilic methoxide attack involving desolvation of the nucleophile with varying extents of resolvation of the TS. With the : Zn(2+)((-)OCH(3)) complex all the skie values are k(D)/k(H) = 1.0 +/- 0.1 except for where the value is 0.79 +/- 0.06. Arguments are presented that the fractionation factors associated with complex : Zn(2+)((-)OCH(3)) are indistinguishable from unity. The skie's for all the complex-catalyzed methanolyses are interpreted as being consistent with an intramolecular nucleophilic attack of the Zn(2+)-coordinated methoxide within a pre-equilibrium metal : substrate complex.     

Hydrothermal Syntheses and Crystal Structures of Two Complexes with 3,5- Dinitrosalicylate and 2,2′-Bipyridine Ligands

The two title complexes,[Cd{3,5-(NO2)2sal}(2,2′-bipy)]n 1 and [Mn{3,5-(NO2)2sal}(2,2′-bipy)]n 2 (3,5-(NO2)2sal=3,5-dinitrosalicylate,2,2′-bipy=2,2′-bipyridine),were synthesized by the hydrothermal reaction and structurally characterized. Complex 1 crystallizes in triclinic,space group P1,a=5.581(4),b=12.071(8),c=12.88(1),α=92.10(3),β=96.73(3),γ =102.02(2)°,C17H10N4O7Cd,Mr=494.69,V=841(1)3,Z=2,Dc=1.954 g/cm3,F(000)=488,μ =1.353 mm-1,R=0.0248 and wR=0.0761. Complex 2 crystallizes in monoclinic with space group P21/c,a=8.604(3),b=23.88(1),c=8.894(3),β=102.45(1)°,C17H10N4O7Mn,Mr=437.23,V= 1785(1) 3,Z=4,Dc=1.627 g/cm3,F(000)=884,μ=0.791 mm-1,R=0.0471 and wR=0.1250. Complex 1 possesses an infinite 1D polymeric chain structure consisting of the repeated basic four-membered ring units (Cd2O2) and eight-membered ring units (CdOCO)2. Compound 2 displays a linear 1D chain through Mn(Ⅱ) atoms and bridging carboxylate groups of 3,5-dinitrosalicylic acid ligands with the Mn…Mn separation of 4.472(2). The fluorescence properties and cyclic voltammetric behaviors of the complexes are also reported.     

Multinuclear Fe(III) complexes with polydentate ligands of the family of dicarboxyimidazoles: nuclearity- and topology-controlled syntheses and Magneto-structural correlations

Two polydentate ligands of the family of dicarboxyimidazoles, H(2)MeDCBI (= 4,5-dicarboxy-1-methyl-1H-imidazole) and H(3)DCBI (= 4,5-dicarboxyimidazole), have been used in reactions with the [Fe(3,5-(t)()Bu(2)salpn)](+) species {3,5-(t)Bu(2)salpn = the dianion of 1,3-bis-[(3,5-di-tert-butylsalicylidene)amino]propane} to synthesize selectively complexes of different nuclearities. Four complexes have been synthesized: the mononuclear complex [Fe(3,5-(t)Bu(2)salpn)(HMeDCBI)] (1), the two binuclear but topologically different complexes [Fe(3,5-(t)Bu(2)salpn)(MeDCBI)Fe(3,5-(t)Bu(2)salpn)] (2) and {[Fe(3,5-(t)Bu(2)salpn)](2)(HDCBI)} (3), and the trinuclear complex {[Fe(3,5-(t)Bu(2)salpn)](2)(DCBI)Fe(3,5-(t)Bu(2)salpn)} (4). The structures of these complexes have been determined by X-ray crystallography. Variable-temperature direct-current magnetic susceptibility measurements were conducted for all compounds to obtain information about their electronic structure and to investigate the extent of magnetic communication among the Fe(III) centers. The results of these measurements allowed us to correlate the different structural motifs with the possible magnetic interactions that arise in multinuclear complexes of dicarboxyimidazoles. For 1, the room-temperature chi(M)T value reveals an S = (5)/(2) ground state. The data for the binuclear but topologically different complexes 2 and 3, and the trinuclear complex 4 suggest that weak intramolecular antiferromagnetic interactions are present, with interaction parameters ranging from -3.6 to -5.1 cm(-1). Differences in the extent of the magnetic communication between the metal centers through the two different interaction pathways of the ligands MeDCBI and DCBI (either through the imidazole ring or through the carboxylate groups) have been observed in complexes 2-4 that can be explained by the structural differences observed in the crystal structures of these compounds (the separation of the metal centers and the coplanarity of the metal ion orbitals with the pi system of the ligands). Cyclic voltammetry measurements for the mononuclear compound 1 show an irreversible reduction wave that is attributed to Fe(3+) + e(-) --> Fe(2+). The electrochemical behavior of the multinuclear complexes 2-4 is more complicated; however, it indicates that there is a degree of electronic communication between the Fe(III) centers.     

Hydrothermal reaction of Cu(II)/pyrazine-2,3,5-tricarboxylic acid and characterization of the copper(II) complexes

Four copper(II) complexes [Cu3(PZHD)2(2,2'-bpy)2(H2O)2].3H2O (1), [Cu3(DHPZA)2(2,2'-bpy)2] (2), [Cu(C2O4)phen(H2O)].H2O (3), and [Cu3(PZTC)2(2,2'-bpy)2].2H2O (4) were synthesized by hydrothermal reactions, in which the complexes 1-3 were obtained by the in situ Cu(II)/H3PZTC reactions (PZHD3- = 2-hydroxypyrazine-3,5-dicarboxylate, 2,2'-bpy = 2,2'-bipyridine, DHPZA3- = 2,3-dihydroxypyrazine-5-carboxylate, C2O42- = oxalate, phen = 1,10-phenanthroline, and H3PZTC = pyrazine-2,3,5-tricarboxylic acid). The Cu(II)/H3PZTC hydrothermal reaction with 2,2'-bpy, without addition of NaOH, results in the formation of complex 4. The complexes 1-4 and transformations from H3PZTC to PZHD3-, DHPZA3-, and C2O4(2-) were characterized by single-crystal X-ray diffraction and theoretical calculations. In the complexes 1, 2, and 4, the ligands PZHD3-, DPHZA3-, and PZTC3- all show pentadentate coordination to Cu(II) ion forming three different trinuclear units. The trinuclear units in 1 are assembled by hydrogen-bonding and pi-pi stacking to form a 3D supramolecular network. The trinuclear units in 2 acting as building blocks are connected by the carboxylate oxygen atoms forming a 2D metal-organic framework (MOF) with (4,4) topology. While the trinuclear units in 4 are linked together by the carboxylate oxygen atoms to form a novel 2D MOF containing right- and left-handed helical chains. The theoretical characterization testifies that electron transfer between OH- and Cu2+ and redox of Cu 2+ and Cu+ are the most important processes involved in the in situ copper Cu(II)/H3PZTC reactions, forming complexes of 1-3.     

Study of intramolecular competition between carboxylate and phosphonate for Pt(II) with the aid of a novel tridentate carboxylato-thioether-phosphonato ligand

The tridentate dianionic ligand 2-[2'-(hydroxyisopropoxyphosphoryl)phenylsulfanyl]benzoate (L(2-)) reacts with cis-[Pt(NH(3))(2)(H(2)O)(2)](2+) to form an S,O-chelate in which the O-coordinated group is either carboxylate or phosphonate, depending on the degree of protonation of the complex. Carboxylate appears to be the stronger ligand, and the stoichiometric reaction between cis-[Pt(NH(3))(2)(H(2)O)(2)](2+) and L(2-) yields the neutral species [Pt(L)(NH(3))(2)], with L bound by sulfanyl and carboxylate groups, both in solution and in the solid state. Upon protonation of [Pt(L)(NH(3))(2)], the stronger basicity of the carboxylate causes the Pt coordination to switch from carboxylate to phosphonate, and the uncoordinated carboxylate group becomes protonated. In methanolic solution, the first-order kinetics of this rearrangement could be observed by (31)P NMR spectroscopy. Both complexes-the carboxylate-bound neutral complex [Pt(L)(NH(3))(2)].H(2)O (triclinic, P1 (no. 2), a=9.529(6), b=9.766(6), c=12.299(7) angstroms, alpha=106.91(2), beta=101.71(2), gamma=102.05(2) degrees, Z=2) and the perchlorate salt of the phosphonate-bound complex [Pt(LH)(NH(3))(2)]ClO(4).H(2)O (monoclinic, P2(1)/c (no. 14), a=12.095(2), b=14.046(2), c=14.448(2) angstroms, beta=95.55(2) degrees, Z=4)-were characterized by X-ray crystallography.     

Mononuclear manganese carboxylate complexes: Synthesis and structural studies

Several manganese carboxylates complexes having Pz^iPr2H (3,5-diisopropylpyrazole), Tp^Ph,Me (hydrotris(3-phenyl,5-methyl-pyrazol-1-yl)borate), Tp^ipr2 (hydrotris(3,5-diisopropyl-pyrazol-1-yl)borate) as supporting ligands have been synthesised and structurally characterized. Single-crystal X-ray diffraction studies suggest that the manganese center in complexes (Pz^iPr2H)₄Mn(NO₂–OBz)₂ (5) and (Pz^iPr2H)₄Mn(F–OBz)₂ (6) have same coordination environment and geometry whereas the complex [Tp^Ph,MeMn(OAc)Pz^Ph,MeH] (7) has a five coordinate manganese center. In all these complexes, the carboxylate groups are coordinated as monodentate and the uncoordinated oxygen atom of the carboxylate groups form intramolecular hydrogen bonds with the NH group of the corresponding coordinated pyrazole (Pz^iPr2H/Pz^Ph,MeH). The complexes 5–8 and 10 were tested for their superoxide dismutase activity and it was found that only complex 7 has SOD activity as its structure is very similar to the active site structure of the native Mn–SOD enzyme. The SOD activity studies on these carboxylate complexes suggest that any model compound with analogous active site structure and intramolecular hydrogen bonding may be a suitable mimic for the Mn–SOD enzyme.     

Preparation, Structure and Electrochemical Property of a Pyrazole-substituted Diiron Dithiolate Complex

A pyrazole-substituted diiron dithiolate complex [Fe2(μ-pdt)(CO)5(3,5-Me2Pz)](1,3,5-Me 2Pz=3,5-dimethylpyrazole) was prepared as a biomimetic model for the active site of [FeFe]-hydrogenase by CO-substitution of all-carbonyl complex [Fe2(μ-pdt)(CO)6] with 3,5-Me2Pz. The molecular structure was confirmed by MS, IR, 1H NMR, elemental analysis and single-crystal X-ray analysis. Complex 1 crystallizes in the triclinic system, space group P1 with a=9.108(7), b=9.743(8), c=11.192(9), α=109.235(5), β=101.914(9), γ=96.605(6)o. In CH3CN solution, reversible transformation between 1 and the acetonitrile-substituted species [Fe2(μ-pdt)-(CO)5(NCCH3)] was detected by both IR and cyclic voltammetry (CV). The electrochemical proton reduction catalyzed by 1 in the presence of acetic acid was also studied in CH2Cl2.     

Synthesis,Magnetic Property and Crystal Structure of a Ytterbium-Copper Mixed Metal Complex:Yb_2Cu_3L_6·6H_2O (L=O(CH_2COO)_2)

1INTRODUCTIONThesynthesisofpolynuc1earmixedcopper-lanthanoidcomplexesisofinterestforseveralreasons[l-4i.Thesecomplexesareimportanttotheunderstandingofthenature0fthemagneticexchangeinteractionsbetweenrareearthandtransiti0n-metalions,andtheycanpossib1ybeusedasmagneticmaterialst2'33andhightemperaturesuperconductors"'.Itwasbelievedthatthemultidentatepoly-carboxylateacidsisgoodligandsforthepreparationoftheLn-Cumixedmetalcomplexesasthemetalionscanbebridgedbythebidentatecarboxylategroups.Thedig…     

Two- and three-dimensional silver(I)-organic networks generated from mono- and dicarboxylphenylethynes

Three phenylethynes bearing methyl carboxylate (HL1), monocarboxylate (H(2)L2), and dicarboxylate (H(2)L3) groups were utilized as ligands to synthesize a new class of organometallic silver(I)-ethynide complexes as bifunctional building units to assemble silver(I)-organic networks. X-ray crystallographic studies revealed that in [Ag(2)(L1)(2)·AgNO(3)](∞) (1) (L1= 4-C(2)C(6)H(4)CO(2)CH(3)), one ethynide group interacts with three silver ions to form a complex unit. These units aggregate by sharing silver ions with the other three units to afford a silver column, which are further linked through argentophilic interaction to generate a two-demensional (2D) silver(I) network. In [Ag(2)(L2)·3AgNO(3)·H(2)O](∞) (2) (L2 = 4-CO(2)C(6)H(4)C(2)), the ethynide group coordinates to four silver ions to form a building unit (Ag(4)C(2)C(6)H(4)CO(2)), which interacts through silver(I)-carboxylate coordination bonds to generate a wave-like 2D network and is subsequently connected by nitrate anions as bridging ligands to afford a three-demensional (3D) network. In [Ag(3)(L3)·AgNO(3)](∞) (3) (L3 = 3,5-(CO(2))(2)C(6)H(3)C(2)), the building unit (Ag(4)C(2)C(6)H(3)(CO(2))(2)) aggregates to form a dimer [Ag(8)(L3)(2)] through argentophilic interaction. The dimeric units interact through silver(I)-carboxylate coordination bonds to directly generate a 3D network. The obtained results showed that as a building unit, silver(I)-ethynide complexes bearing carboxylate groups exhibit diverse binding modes, and an increase in the number of carboxylate groups in the silver(I)-ethynide complex unit leads to higher level architectures. In the solid state, all of the complexes (1, 2, and 3) are photoluminescent at room temperature.     

水杨醛缩4-氨基安替吡啉双核铜(Ⅱ)配合物的合成和晶体结构

标题化合物{[Cu(C18H17N3O2)]2(COO)}(ClO4).3H2O(1)由Cu(ClO4)2.6H2O\甲酸、水杨醋缩4-氨基安替吡啉经溶剂热反应得到,用单晶衍射法测定了配合物的结构,具体测定结果如下:单斜晶,空间群P2/c,a=15.1500(2),b=23.8857(11),c=12.9709(4),β=107.265(3)°,V=4482.3(3)3,Dc=1.349g/cm3,Z=4,Mr=910.28,μ=1.066mm-1和F(000)=1872,最终偏差因子分别为R1=0.0924,wR2=0.2514。在此晶体结构中,2个铜离子被COO-和苯酚氧桥联形成二聚单元,每个Cu(Ⅱ)是五配位的变形四方锥构型。     

新型双大环二正丁基锡羧酸酯的合成、晶体结构及生物活性

在乙醇钠催化下, 将3-(1,2亚丙二硫基)亚甲基-2,4-二羰基戊烷与2-羰基苯氧乙酸进行缩合反应, 获得了柔性二元酸配体1[4-(1,2-亚丙二硫基)亚甲基-3,5-二羰基-1,6-庚二烯-1,7-二(2-羰基苯)氧乙酸(LH2)]. 再将配体1与二正丁基氧化锡进行脱水反应, 获得新型二正丁基锡羧酸酯配合物2. 采用元素分析、1H NMR、 IR及晶体结构测定等手段对配体1和配合物2进行了结构表征, 配合物2是以菱形环Sn2O2为中心对称的二聚体结构, 中心菱形环通过氧原子与2个环外锡原子相连. 每个羧基分别与环内锡和环外锡原子配位, 形成2个对称的六元环, 3个环呈梯形排列, 将整个分子分割成2个对称的二十二元大环. 初步研究了其杀菌活性和抗癌活性.