One- and two-dimensional copper benzenedicarboxylate coordination polymers incorporating the flexible tethering diimine N,N′-bis(3-pyridylmethyl)piperazine: Synthesis,structure, and thermal properties

A family of three copper benzenedicarboxylate coordination polymers has been constructed using the conformationally flexible and hydrogen-bonding capable tethering ligand N,N′-bis(3-pyridylmethyl)piperazine (3-bpmp). These three coordination polymers have been characterized via single crystal X-ray diffraction, infrared spectroscopy and elemental and thermogravimetric analysis. {[Cu(ph)(Hph)(H3-bpmp)(H₂O)] · 3H₂O} (1, ph = phthalate) manifests a 1-D chain motif held into a pseudo 3-D supramolecular structure through hydrogen bonding. While both {[Cu(ip)(3-bpmp)(H₂O)] · 2H₂O} (2, ip = isophthalate) and [Cu(tp)(3-bpmp)] (3, tp = terephthalate) exhibit 2-D (4,4) rhomboid grid-like layers, they possess different layer stacking patterns and supramolecular interactions due to coordination geometry variances.     

Syntheses and crystal structures of the metal complexes based on pyrazolecarboxylic acid ligands

This paper aims at introducing five new metal complexes, Co(HL₁)₂(H₂O)₂ (1), {[Cu(HL₁)₂] · (H₂O)}_n (2), {[Zn(HL₂)(H₂O)₃] · 2H₂O}_n (3), {[Co(HL₂)(H₂O)₃] · 2H₂O}_n (4) and [K(H₂L₂)]_n (5), (in which H₂L₁ is 3-methyl-5-pyrazolecarboxylic acid and H₃L₂ is 3,5-pyrazoledicarboxylic acid, respectively), which have been synthesized under hydrothermal conditions or by using diffusion methods. Their molecular structures have been characterized by elemental analyses, IR spectroscopy and single-crystal X-ray diffraction analyses. The X-ray analyses reveal that complex 1 has a mononuclear structure, which is further assembled to a three-dimensional (3-D) framework through intermolecular hydrogen bonds; complex 2 is a 1-D coordinated polymer, which is further assembled to a 2-D layer through intermolecular hydrogen bonds and π–π interactions; both complexes 3 and 4 possess similar 1-D chain structures, and the adjacent chains are further linked by hydrogen bonds to form 2-D supramolecular networks; complex 5 exhibits a 3-D structure, in which, the metal–metal weak interaction, K–K, plays an important role.     

Synthesis,structures and characterization of the dinuclear nickel(II) complexes containing N,N,N′,N′-tetrakis[(1-ethyl-2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane and an azide ion

Two dinuclear nickel(II) complexes, [Ni₂(L-Et)(N₃)(H₂O)₃](NO₃)₂ · 2H₂O (1) and [Ni₂(L-Et)(μ-1,3-N₃)(H₂O)₂](NO₃)₂ · 4H₂O (2) containing (HL-Et = N,N,N′,N′-tetrakis[(1-ethyl-2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane), have been synthesized and characterized by their IR and UV–Vis spectra and magnetic susceptibilities. The crystal structures of [Ni₂(L-Et)(N₃)(H₂O)₃](NO₃)₂ · CH₃OH (1′) and [Ni₂(L-Et)(μ-1,3-N₃)(H₂O)₂](NO₃)₂ · 2C₂H₅OH (2′) similar to 1 and 2 were determined by X-ray crystallography. In 1′, the two nickel(II) ions are bridged by only an alkoxo group of L-Et⁻, while an azido and an alkoxo connect two nickel(II) ions in 2′. Magnetic susceptibility measurements (2–300 K) showed a weak ferromagnetic exchange coupling between the two nickel(II) ions (2J = 10.1 cm⁻¹) for 1. On the other hand, antiferromagnetic interactions were observed for 2 (2J = −15.8 cm⁻¹).     

Synthesis,characterization and magnetic properties of six new copper(II) complexes with aminoacids as bridging ligand,exhibiting ferromagnetic coupling

The synthesis, crystallographic analysis and magnetic studies of six new copper(II) complexes of formulae [Cu(μ-ala)(im)(H₂O)]_n(ClO₄)_n (1), [Cu(μ-ala)(pz)(μ-ClO₄)] (2), [Cu(μ-phe)(im)(H₂O)]_n(ClO₄)_n (3), [Cu(μ-gly)(H₂O)(ClO₄)]_n (4), [Cu(μ-gly)(pz)(ClO₄)]_n(5) and [Cu(μ-pro)(pz)(ClO₄)]_n (6) have been carried out (ala = alanine; phe = phenylalanine; gly = glycine; pro = proline; im = imidazole; pz = pyrazole). In all cases, the deprotonated aminoacid ligand acts as chelate through the N(amine) and one O(carboxylato), whereas the second O atom of the same carboxylato acts as a bridge to the neighbouring copper(II) ion. The coordination of copper(II) ions is square-pyramidal in all complexes but 2 (elongated O_h). All complexes (1–6) are uniform chains with syn–anti (equatorial–equatorial) coordination mode of the carboxylato bridging ligand, exhibiting intrachain ferromagnetic interactions.     

The 2-D double layer structures of indium–benzenemulticarboxylate coordination polymers with green fluorescence

Two coordination polymers, [In(btc)(2,2′-bpy)(H₂O)]_n · nH₂O (1) and [In₂(btec)(2,2′-bpy)₂Cl₂]_n (2) (H₃btc = 1,3,5-benzenetricarboxylic acid, H₄btec = 1,2,4,5-benzenetetracarboxylic acid, 2,2′-bpy = 2,2′-bipyridine), have been prepared under hydrothermal conditions. Single-crystal X-ray diffraction analyses reveal that compounds 1 and 2 consist of two-dimensional double layer structures with (3, 3) grids and (4, 2) grids, respectively. The grids along two different directions in 1 are of the opposite chirality, while the interactions of double-layer sheets in 2 create a three-dimensional supramolecular network with one-dimensional tunnels. The additional green luminescences for both 1 and 2 in the solid state at low temperature imply the red shift of emission energy in the compounds, which may derive from LMCT. Their X-ray powder diffractions and thermogravimetric analyses are also discussed.     

Syntheses,characterization, antimicrobial and cytotoxic activities of pyridine-2,5-dicarboxylate complexes with 1,10-phenanthroline

In this study, four mononuclear M(II)-pyridine-2,5-dicarboxylate (M = Co(II), Ni(II), Cu(II) and Zn(II) complexes with pyridine-2,5-dicarboxylic acid or isocinchomeronic acid, 1,10-phenanthroline (phen), [Co(Hpydc)₂(phen)]·H₂O (1), [Ni(pydc)(phen)₂]·6.5H₂O (2) [Cu(pydc)(phen)(H₂O)₂] (3) and [Zn(pydc)(phen)(H₂O)₂]·H₂O (4) have been synthesized. Elemental, thermal and mass analyses, molar conductance, magnetic susceptibilities, IR and UV/vis spectroscopic studies have been performed to characterize the complexes. Subsequently, these ligands and complexes were tested for antimicrobial activity by disc diffusion method on Gram positive, negative bacteria and yeast. In addition, cytotoxic activity tests were performed on rat glioma (C6) cells by MTT viability assay for 24 and 48 h. Antimicrobial activity results demonstrated that when compared to the standard antibiotics, phen displayed the most effective antimicrobial effect. The effect of synthesized complexes was close to phen or less. Cytotoxic activity results showed that IC₅₀ value of phen was determined as 31 μM for 48 h. (1) and (2) compared to the alone ligand had less toxic activity. IC₅₀ values of (3) for 24 and 48 h treatments were 2.5 and 0.6 μM, respectively. IC₅₀ value of (4) for 48 h was 15 μM. In conclusion, phen, (3) and (4) may be useful as antibacterial and antiproliferative agents in the future.     

[RuIII(medtra)(H2O)] (medtra = N-methylethylenediaminetriacetate) complex – A highly efficient NO inhibitor with low toxicity

Stopped-flow kinetic measurements were used to compare the reactivities of [Ru(medtra)(H₂O)] (medtra³⁻ = N-methylethylenediaminetriacetate) (1) and [Ru(hedtra)(H₂O)] (2) (hedtra³⁻ = N-hydroxyethylethylenediaminetriacetate) with NO in aqueous solution at 15 °C, pH 7.2 (phosphate buffer). The measured second-order rate constants (3 × 10³ and 6 × 10⁴ M⁻¹ s⁻¹ for 1 and 2, respectively) are three to four order of magnitudes lower than that for the reaction between [Ru^III(edta)(H₂O)]⁻ (3) with NO. However, NO scavenging studies of complexes 1–3, conducted by measuring the difference in nitrite production between treated and untreated murine macrophage cells, revealed that despite being less kinetically reactive toward NO, the [Ru(medtra)(H₂O)] complex exhibited the highest NO scavenging ability and lowest toxicity of compounds 1–3.     

Syntheses and crystal structures of trimethyltin(IV) coordination polymers based on mixed ligands of 5-nitroisophthalate and 2,2′(4,4′)-bipy or phen

The trimethyltin(IV) polymer [(Me₃Sn)₂(nip) · EtOH]_n (1) of 5-nitroisophthalic acid (H₂nip) and its three derivatives with mixed organic N-donor ligands 2,2′-bipy [(Me₃Sn)₂(nip) · 2H₂O] · [(Me₃Sn)₂(nip) · H₂O] · 2(2,2′-bipy) (2) 4,4′-bipy {[(Me₃Sn)₂(nip)]₂(4,4′-bipy)}_n (3) or phen [(Me₃Sn)₂(nip) · H₂O] · (phen) (4) have been synthesized by the reaction of trimethyltin(IV) chloride and H₂nip when sodium ethoxide was added in the presence of 2,2′-bipy 4,4′-bipy or phen. All complexes 1–4 were characterized by elemental, IR, ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopy and X-ray crystallography analyses. Crystal, data collection and structure refinement parameters for complexes 1, 2, 3 and 4 are shown in Table 1, Table 2, respectively. The X-ray data showed the geometries of all the tin atoms in complexes 1–4 are trigonal bipyramidal. The X-ray analysis of 1 showed that the structure was a polymeric infinite chain with neighboring triorganotin centers being linked by dicarboxylate ligands and hydrogen bonds were found between adjacent chains. For 2, two different monomers were found, in one monomer, Me₃Sn were coordinated to both carboxyl groups of the ligand and water molecules were coordinated to the two Sn(IV) centers. In the other monomer, water molecules were coordinated to only one Sn center. Co-crystallized2,2′-bipy was found in 2 and a 2D supermolecular structure was formed via O–H⋯O and O–H⋯N (N atoms derived from 2,2′-bipy) hydrogen bonds. In 3 however, a 2D polymeric block was formed due to the inversion center of the 4,4′-bipy. For 4, due to the O–H⋯O and O–H⋯N (N atoms derived from phen) hydrogen bonds and intermolecular Sn⋯O bonds, a 2D polymeric structure was formed.     

Synthesis,crystal structures and properties of three rare earth substituted germanotungstates: M/[α-GeW11O39] (M = Nd,Eu, and Tb)

Three new polyoxometalate compounds based on the lacunary Keggin anion [α-GeW₁₁O₃₉]^8? and the rare earth cations (Ln = Nd^III, Eu^III, Tb^III), [(CH₃)₄N]_2.5H_7.5[Eu(GeW₁₁O₃₉)(H₂O)₂]₂ · 4.5H₂O (1), [(CH₃)₄N]₂H₈[Tb(GeW₁₁O₃₉)(H₂O)₂]₂ · 2.5H₂O (2) and [Nd_0.5(H₂O)₂]H_0.5[Nd₂(GeW₁₁O₃₉)(DMSO)₂(H₂O)₈] · 5.5H₂O (3), have been synthesized and characterized by elemental analysis, inductively coupled plasmas (ICP) analysis, IR spectroscopy, single-crystal X-ray diffraction. The solid-state structures of compounds 1 and 2 consist of one-dimensional linear wires built of [α-GeW₁₁O₃₉]^8? anions connected by Eu³⁺/Tb³⁺ cations, while in compound 3, the introduction of the organic molecules DMSO (DMSO = dimethyl sulphoxide) leads to a double-parallel chainlike structure constructed by two linear wires {[Nd(1)(GeW₁₁O₃₉)(DMSO)(H₂O)₂]^5?}_n linked by Nd³⁺ coordination cation. Furthermore, the luminescent property of compound 1 and the thermal stability of compound 3 were also studied.     

Copper(II) and zinc(II) complexes with Schiff-base ligands derived from salicylaldehyde and 3-methoxysalicylaldehyde: Synthesis,crystal structures,magnetic and luminescence properties

The following Schiff bases were employed as ligands in synthesizing copper(II) and zinc(II) complexes: N-[(2-pyridyl)-methyl]-salicylimine (Hsalampy), N-[2-(N,N-dimethyl-amino)-ethyl]-salicylimine (Hsaldmen), and N-[(2-pyridyl)-methyl]-3-methoxy-salicylimine (Hvalampy). The first two ligands were obtained by reacting salicylaldehyde with 2-aminomethyl-pyridyne and N,N-dimethylethylene diamine, respectively, while the third one results from the condensation of 3-methoxysalicylaldehyde with 2-aminomethyl-pyridine. Four new coordination compounds were synthesized and structurally characterized: [Cu(salampy)(H₂O)(ClO₄)] 1, [Cu₂(salampy)₂(H₂trim)₂] 2 (H₂trim^? = the monoanion of the trimescic acid), [Cu₄(valampy)₄](ClO₄)₄ · 2CH₃CN 3, and [Zn₃(saldmen)₃(OH)](ClO₄)₂ · 0.25H₂O 4. The crystal structure of 1 consists of supramolecular dimers resulted from hydrogen bond interactions established between mononuclear [Cu(salampy)(H₂O)(ClO₄)] complexes. Compound 2 is a binuclear complex with the copper ions connected by two monoatomic carboxylato bridges arising from two molecules of monodeprotonated trimesic acid. The crystal structure of 3 consists of tetranuclear cations with a heterocubane {Cu₄O₄} core, and perchlorate ions. Compound 4 is a trinuclear complex with a defective heterocubane structure. The magnetic properties of complexes 1–3 have been investigated. Compound 4 exhibits solid-state photoluminescence at room temperature.     

Ketone H2-hydrogenation catalysts: Ruthenium complexes with the headphone-like ligand bis(phosphaadamantyl)propane

Treatment of 1,3-diphosphinopropane with acetylacetone in the presence of HCl gives the new chiral bis(phosphaadamantyl)propane ligand (bpap) (1) as a mixture of diastereoisomers. Recrystallization from ethanol gives a mixture enriched in rac diastereoisomer (90% rac/10% meso). The enriched mixture reacts with [RuHCl(PPh₃)₃] in refluxing THF to give [RuHCl(bpap)(PPh₃)] (2) in 73% yield. Compound 2 reacts readily with chiral diamines giving octahedral trans-[RuHCl(bpap)(diamine)] complexes 3 (diamine = (1R,2R)-1,2-diaminocyclohexane) and 4 (diamine = (1R,2R)-1,2-diphenylethylenediamine). Compounds 3 and 4 are very active catalysts for H₂-hydrogenation of neat acetophenone in the presence of KO^tBu as a strong base under mild conditions (room temperature, 3 atm of H₂). The low ee values for 1-phenethanol can be attributed to the similar shapes of two terminal adamantoid cages and the flexible backbone of the bpap ligand. The structures of complexes 2 and 3 have been determined by single-crystal X-ray diffraction.     

Linear homobimetallic 4-thioacetyl-substituted NCN pincer palladium(II) and platinum(II) complexes with N-bidentate connecting units (NCN = [C6H2(CH2NMe2)2-2,6-R-4]−)

The synthesis and characterization of homobimetallic palladium and platinum complexes of type [(Me(O)CS-4-NCN–M ← N^∩N → M–NCN-4-SC(O)Me](OTf)₂ (Me(O)CS-4-NCN = [C₆H₂(CH₂NMe₂)₂-2,6-SC(O)Me-4]^?; N^∩N = 4,4′-bipyridine (bipy); M = Pd, 12; M = Pt, 13) is reported. The required bifunctional thio-acetyl NCN pincer starting compound NC(Br)N-4-SC(O)Me (2) has been synthesized by the consecutive reactions of NC(Br)N–I (I-1-C₆H₂(CH₂NMe₂)₂-3,5-Br-4) (1) with ^tBuLi, S₈ and Me(O)CCl, respectively. Chemoselective metallation at the C_aryl–Br bond was achieved by the reaction of 2 with the palladium(0) source [Pd₂(dba)₃] (3) (dba = dibenzylidene acetone). Treatment of thus formed [Pd(NCN-4-SC(O)Me)(Br)] (4) with [AgOTf] (8) (OTf = triflate, OSO₂CF₃) gave [Pd(NCN-4-SC(O)Me)(H₂O)][OTf] (9) which was further reacted with 0.5 equiv. of 4,4′-bipyridine (11a) to afford rigid-rod structured 12. When [Pt(tol)₂(SEt₂)]₂ (5) (tol = 4-tolyl) was used instead of 3, then 13 was produced via the in situ formation of [PtBr(NCN-4-SC(O)Me)] (7) and [Pt(NCN-4-SC(O)Me)(H₂O)][OTf] (10). Another possibility to synthesize 7 relied upon the subsequent reaction of 1 with 0.5 equiv. of 5 to give [PtBr(NCN-4-I)] (6) which further reacted with ^tBuLi, 1/8 S₈ and Me(O)CCl to afford 7. The cyclic voltammograms of 2, 7, and 13 are discussed.Complex 7 was structurally characterized by single crystal X-ray crystallography. Organometallic 7 crystallizes with three independent molecules in the asymmetric unit and displays a monomeric structure as commonly encountered in d⁸-metal pincer chemistry.     

Syntheses,structures and photoluminescent property of coordination complexes with 2-(1H-1,2,4-triazol-1-yl)acetic acid

Reactions of ligand 2-(1H-1,2,4-triazol-1-yl)acetic acid (HL) with varied metal salts of Cu(II), Co(II), Ni(II), Zn(II), Cd(II) and Ag(I) result in formation of six new coordination complexes, {[Cu(L)₂] · 3H₂O}_n (1), [Co(L)₂(H₂O)₂]_n (2), [Ni(L)₂(H₂O)₂]_n (3), [Zn(L)₂(H₂O)₂]_n, (4), [Cd(L)₂]_n (5) and [Ag(L)]_n (6), and their structures were determined by X-ray crystallography. Complexes 1, 2, 3 and 4 with square-planar or octahedral metal centers have similar two-dimensional (2D) network structure with (4, 4) topology, while complex 5 displays a 2D structure with (6, 3)-connected topology. Complex 6 has a three-dimensional (3D) structure, in which the Ag(I) has tetrahedral coordination geometry. Ligand L^? acts as a 2-connected rod (bridging ligand) in 1, 2, 3 and 4, and acts as 3-connected nodes in 5 and 6. The results indicate that the coordination modes of the ligand and metal centers have great influence on the structures of the complexes. In addition, the photoluminescent properties of ligand HL and complexes 4 and 5 were studied in the solid state at room temperature.     

Syntheses,structures, and magnetic properties of heterobimetallic complexes based on tetracyanometallic building blocks

Two tetracyanometalate building blocks, [Fe(5,5′-dmbipy)(CN)₄]^? (2) and [Fe(4,4′-dmbipy)(CN)₄]^? (3) (5,5′-dmbipy = 5,5′-dimethyl-2,2′-bipyridine; 4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine), and two cyano-bridged heterobimetallic complexes, [Cu₂(bpca)₂(H₂O)₂Fe₂(5,5′-dmbipy)₂(CN)₈] · 2[Cu(bpca)Fe(5,5′-dmbipy)(CN)₄] · 4H₂O (4) and [Cu(bpca)Fe(4,4′-dmbipy)(CN)₄]_n (5) (bpca = bis(2-pyridylcarbonyl)amidate), have been synthesized and structurally characterized. Complex 4 contains two dinuclear and one tetranuclear heterobimetallic clusters in an asymmetric unit whereas the structure of complex 5 features a one-dimensional heterobimetallic zigzag chain. The Cu(II) ion is penta-coordinated in the form of a distorted square-based pyramid. Magnetic studies show ferromagnetic coupling between Cu(II) and Fe(III) ions with g = 2.28, J₁ = 2.64 cm^?1, J₂ = 5.40 cm^?1 and TIP = ?2.36 × 10^?3 for complex 4, and g = 2.17, J = 4.82 cm^?1 and zJ′ = 0.029 cm^?1 for complex 5.     

Tuning magnetic properties using targeted structural distortion: New additions to a family of Mn6 single-molecule magnets

We report the synthesis and magnetic properties of three hexametallic Mn clusters: [Mn₆O₂(Et-sao)₆(O₂C-Naphth)₂(EtOH)₄(H₂O)₂] (1) (HO₂C-Naphth = 1-naphthoic acid, Et-saoH₂ = 2-hydroxyphenylpropanone oxime), [Mn₆O₂(Et-sao)₆(O₂C-Anthra)₂(EtOH)₄(H₂O)₂] · 0.66EtOH · 0.33H₂O (HO₂C-Anthra = anthracene-9-carboxylic acid) (2 · 0.66EtOH · 0.33H₂O) and [Mn₆O₂(Et-sao)₆(O₂CPhCCH)₂(EtOH)₄(H₂O)₂] · 1.7EtOH · 0.3H₂O (HO₂CPhC  CH = 4-ethynylbenzoic acid) (3 · 1.7EtOH · 0.3H₂O). Clusters 1–3 exhibit ferromagnetic exchange between all six Mn^III centres resulting in S = 12 ground spin states. Ac magnetic susceptibility and single crystal micro-SQUID measurements on 1–3 confirm SMM behaviour with barriers to magnetisation reversal of 60.12 (1), 60.10 (2) and 66.79 (3) K.     

Structure and magnetic properties of a trinuclear nickel(II) complex with benzenetricarboxylate bridge

Novel trinuclear Ni(II) complex [Ni₃(pmdien)₃(btc)(H₂O)₃](ClO₄)₃ · 4H₂O, 1 where pmdien = N,N,N′,N′,N″-pentamethyldiethylenetriamine, H₃btc = 1,3,5-benzenetricarboxylic (trimesic) acid, has been prepared and structurally characterized. Three nickel atoms are bridged by btc trianion and their coordination sphere is completed by three N atoms of pmdien and O atom of the water molecule. The three nickel(II) magnetic centers are equivalent and their coordination spheres are completed to deformed octahedrons. Magnetic susceptibility was measured over the temperature range 1.8–300 K and zJ′ = ?0.19 cm^?1, D = 3.79 cm^?1, g = 2.18 parameters were calculated.     

Two novel erbium (III) coordination polymers with 5-nitroisophthalic acid: Syntheses and crystal structures and thermal stabilities

Two new coordination polymers, {[Er(5-nip)_1.5(2,2′-bipy)](H₂O)₂}_n (1) and {[Er(5-nip)₂] (4,4′-H₂bipy)_0.5}_n (2) (5-nip = 5-nitroisophthalic acid, 2,2′-bipy = 2,2′-bipyridyl, 4,4′-bipy = 4,4′-bipyridyl), have been synthesized by the hydrothermal reactions of erbium nitrate, 5-nitroisophthalic acid (5-H₂nip) and 2,2′-bipyridyl (for 1), and erbium nitrate, 5-nitroisophthalic acid and 4,4′-bipyridyl (for 2). X-ray diffraction analysis indicates that complex 1 exhibits a two-dimensional layer structure, while complex 2 displays a 3D architecture sustained by the strong hydrogen-bond interactions between the protonated 4,4′-bipyridyl and the carboxyl oxygen atom from [Er₂(5-nip)₄]²⁻ with 2D layer structure, and 4,4′-bipyridyl as the guest molecules exist in bilayer channel. They are characterized by the elemental analysis and IR spectroscopy. The studies for the thermal stabilities of the two complexes show that complex 2 is more stable than complex 1.     

Synthesis,structures and reactivity of N-donor-functionalised Cu(I) aryloxides

The preparation and characterisation of the Cu(I) aryloxides [Cu₁₆(3-pyO)₁₆(dppm)₈] (1), [{Cu₂(2-pyO)₂(dppm)}₂] (2) and [{Cu₃(μ₃-6-OQ)₂(dppm)₃}{(6-HOQ)₂(μ-6-OQ)}] (3) (dppm = 1,2-bis-diphenylphosphinomethane, 6-HOQ = 6-hydroxyquinoline, py = pyridine) are described. A first attempt to employ organic anhydrides in insertion reactions with Cu(I) aryloxides was made producing the one-dimensional coordination polymer 1/_∞[Cu₃(3-pyO)(CO₂C₂H₄Boc)(dppm⁻)(dppm)]_∞ (4) (Boc = tert-butoxycarbonyl).     

New rhenium complexes with ciprofloxacin as useful models for understanding the properties of [99mTc]-ciprofloxacin radiopharmaceutical

Rhenium complexes with the antibiotic ciprofloxacin have been prepared to be studied as models of technetium radiopharmaceuticals. With this aim, the new rhenium complexes 1 {[ReO(Cpf)₂]Cl}, 2 {[ReO(CpfH)₂]Cl₃} and 3 {fac-[Re(CO)₃(H₂O)(Cpf)]} with ciprofloxacin (CpfH = ciprofloxacin; Cpf = conjugated base of ciprofloxacin) have been synthesised and characterised by elemental analyses, IR, NMR (¹H, ¹⁹F and ¹³C CP-MAS) spectroscopy, as well as MS measurements. All spectroscopic data are consistent with the coordination of ciprofloxacin in all these complexes through the carbonyl and the carboxylate oxygen atoms with the formation of a six member chelate ring.The study of a Tc-ciprofloxacin solution by ESI–MS reveals the presence of [TcO(Cpf)₂]⁺ cations, which agrees with the hypothesis that complexes 1 and 2 can be seen as model rhenium complexes of this radiopharmaceutical.Antimicrobial and DNA gyrase inhibition studies performed with complexes 2 and 3 have shown a very similar behaviour between complex 2 and the free antibiotic, whereas complex 3 exhibit a lower antimicrobial activity.Based on a joint analysis of the data reported in the literature and the chemical and biological results obtained in this study, a tentative proposal to explain some aspects of the behaviour of Tc-ciprofloxacin radiopharmaceutical has been made.     

Magnetostructural correlations and catecholase-like activities of μ-alkoxo-μ-carboxylato double bridged dinuclear and tetranuclear copper(II) complexes

Two μ-alkoxo-μ-carboxylato bridged dinuclear copper(II) complexes, [Cu₂(L¹)(μ-HCO₂)] (1) ((H₃L¹ = 1,3-bis(5-bromosalicylideneamino)-2-propanol)), [Cu₂(L²)(μ-HCO₂)] · dmf (2) (H₃L² = 1,3-bis(3,5-chlorosalicylideneamino-2-propanol)), and two μ-alkoxo-μ-dicarboxylato doubly bridged tetranuclear copper(II) complexes, [{Cu₂(L³)}₂(μ-O₂C–C(CH₃)₂–CO₂)] · 5H₂O · 3CH₃OH (3) ((H₃L³ = 1,3-bis(salicylid-deneamino)-2-propanol)) and [{Cu₂(L³)}₂(μ- O₂CCH₂–C₆H₄–CH₂CO₂)] · 2H₂O (4) have been prepared and characterized. The single crystal X-ray analysis shows that the structures of complexes 1 and 2 are dimeric with two adjacent copper(II) atoms bridged by μ-alkoxo-μ-carboxylato ligands with the Cu⋯Cu distances and Cu–O(alkoxo)–Cu angles are 3.511 Å and 132.85° for 1, 3.517 Å and 131.7° for 2, respectively. Complexes 3 and 4 consist of μ-alkoxo-μ-dicarboxylato doubly bridged tetranuclear Cu(II) complexes with mean Cu–Cu distances and Cu–O–Cu angles of 3.158 Å and 108.05° for 3 and 3.081 Å and 104.76° for 4, respectively. Magnetic measurements reveal that 1 and 2 are strong antiferromagnetically coupled with 2J = −156 and −152 cm⁻¹, respectively, while 3 and 4 exhibit ferromagnetic coupling with 2J = 86 and 155.2 cm⁻¹, respectively. The 2J values of 1–4 are linearly correlated to the Cu–O–Cu angles. Dependence of the pH at 25 °C on the reaction rate of oxidation of 3,4-di-tert-butylcatechol (3,5-dtbc) to the corresponding quinone catalyzed by 1–4 was studied. Complexes 1–4 exhibit high catecholase-like activity at pH 9.0 and 25 °C for oxidation of 3,5-di-tert-butylcatechol.