From Cu(I) and Cu(I)-Cu(II) mixed-valence clusters to 2D Cu(II) and Cu(I) coordination polymers supported by a flexible bis-tetrazole organosulfur ligand.

Three coordination compounds from the reaction of copper(II) bromide with the flexible bis-tetrazole organosulfur ligand, 1,2-bis(1-methyl-1H-tetrazole-5-ylthio)ethane (bmtte) have been isolated and characterised. The identification of polymeric 2∞Cu2Br4(bmtte) (1), trinuclear [Cu3Br4(bmtte)2] (2) and tetranuclear [Cu2Br2(bmtte)]2 (3) compounds shows that the reaction conditions have a significant influence on the structure of the complexes formed. Moreover, two polymorphs of the 2D Cu(II)-coordination polymer 1 have been isolated and these crystallise in the monoclinic C2/m (1m) and the triclinic P1̄ (1t) space groups. The thermal stabilities and behaviour in aqueous media of compounds 1-3 were investigated along with the reactivity of compound 2 with CuBr2 and KI. The solid-state reaction between mixed-valence compound 2 with KI or the direct reaction of CuI and bmtte under microwave irradiation allowed the preparation of the polymeric 2∞Cu4I4(bmtte)2 (4). The redox behaviour of complexes 2 and 3 was analysed by cyclic voltammetry.

Coordination Chemistry of Potentially S,N,Npy-Tridentate Thiosemicarbazones with the {Re(CO)3}+ Fragment and Formation of Hemiaminal Derivatives.

Nine potentially S,N,Npy-tridentate thiosemicarbazones (HL) derived from pyridine-2-carbaldehyde or 1-(2-pyridyl)ethanone have been prepared and fully characterized. The X-ray crystal structures of six of them and two hydrochlorides were determined and analyzed. The reaction of the [ReX(CH3CN)2(CO)3]/[ReX(CO)5] (X = Cl and Br) precursors with these ligands yielded different kinds of compounds: the adducts [ReX(HL)(CO)3], in which the ligands were S,N-bidentate; the trinuclear species [Re3Cl2(L23)(HL23)(CO)9]; and the thiosemicarbazonate compounds [Re(L)(CO)3], where the ligand is S,N,Npy-tridentate. Besides, the reaction in methanol or ethanol of the thiosemicarbazones derived from aldehydes yielded S,N,Npy-tridentate hemiaminal cationic [Re(HLOR)(CO)3]X and neutral [Re(LOMe)(CO)3] complexes after the coordinated ligand underwent addition of the alcohol group to the imine bond. The reactivity of the complex [ReX(HL)(CO)3] in MeOH and NEt3 led to the formation of dinuclear [Re2(L)2(CO)6], where the thiosemicarbazonate is again S,N-bidentate. The influence that the substituents on the thiosemicarbazone ligands have on the stability of the complexes and the effect of the reaction medium on the resulting compounds have been analyzed.

Synthesis of Novel Dinuclear N-Substituted 4-(Dimethylamino)benzaldehyde Thiosemicarbazonates of Rhenium(I): Formation of Four- and/or Five-Membered Chelate Rings, Conformational Analysis, and Reactivity.

The reaction of fac-[ReX(CH3CN)2(CO)3] (X = Cl, Br) with N-phenyl-[4-(dimethylamino)benzaldehyde] thiosemicarbazone (HLA) or N-4-methoxybenzyl-[4-(dimethylamino)benzaldehyde] thiosemicarbazone (HLB) under controlled synthetic conditions gave 4 mononuclear [ReX(HL)(CO)3] (X = Cl, Br) and 16 dinuclear [Re2L2(CO)6] compounds. These complexes were obtained as single crystals, and their structures were established by X-ray diffraction. The structural study of these dimers showed the formation of several solvates, the presence of linkage isomerism, and the stabilization of four- and/or five-membered chelate rings. The different ligand coordination modes (a new µ-κ2-S,N2:κ-N3 coordination mode for a thiosemicarbazone ligand was observed), the conformation of the thiosemicarbazone chain in each case, the formal symmetry of the dimers, and the role of the synthetic procedure in the stability of the different chelate rings were analyzed and are discussed. Theoretical calculations in the gas phase were performed for the dimers with the HLA ligand in order to identify the thermodynamically most stable species. The behavior and structural stability of dimers in dimethyl sulfoxide and acetone solutions was investigated by 1H NMR spectroscopy. The strength of the ReI-L bond in solution was evidenced by the formation of [Re2(LNO2)2(CO)6] and [Re(LA)(py)(CO)3] upon reaction of the corresponding dimer with concentrated nitric acid and pyridine, respectively.

Chemical and biological studies of Re(I)/Tc(I) thiosemicarbazonate complexes relevant for the design of radiopharmaceuticals.

Five thiosemicarbazones (H2Ln) derived from 4,6-diacetylresorcinol (n = 1-4) and salicylaldehyde (n = 5) have been synthesized and spectroscopically characterized. Single crystal X-ray diffraction studies on some of them show that the molecular structure is dominated by intramolecular hydrogen bonds involving the O(1)-H group of the resorcinol/salicylaldehyde group and the azomethinic nitrogen atom and sulfur atom of the thiosemicarbazone arm. All of the ligands react with fac-[ReBr(CO)3(CH3CN)2] in the presence of NEt3 to form the stable anionic complexes [NHEt3][fac-[Re(Ln)(CO)3] (1-5). The thiosemicarbazonate ligand, as suggested by spectroscopic data and confirmed by X-ray diffraction, acts as a tridentate S,N,O system. The complexes are stable in solution for weeks, although other dimeric species were also detected by X-ray diffraction analysis. The reaction of fac-[99mTc(CO)3(H2O)3]+ with the appropriate ligand at 100 °C for 30 min yielded the complexes [fac-[99mTc(Ln)(CO)3]- (Tc1-Tc5). The radiochemical yield and purity were determined by HPLC and their chemical identity was ascertained by comparing their radiochromatogram with the chromatogram of the rhenium congeners (1-5). The results of biodistribution studies in mice on the five technetium compounds showed rapid blood clearance and fast liver uptake that slowly cleared into the intestines, a finding that indicates the hepatobiliary tract as the major excretory pathway. HPLC analysis of urine and blood serum samples from mice injected with the 99mTc complexes confirmed their in vivo stability since the predominant radiochemical species had the same retention time as the corresponding injected compound.

Thiosemicarbazonate complexes with affinity for amyloid-ß fibers: synthesis, characterization and biological studies.

Aim: Obtain radioimages of amyloid-ß fibers using 99mTc-complexes. Methodology: Tridentate thiosemicarbazone and thiocarbonohydrazone ligands containing fragments (stilbene, azobenzene, benzothiazole or benzoxazole) with affinity for amyloid-ß fibers and its Re(I) complexes have been prepared. The molecular structures of several ligands and complexes were determined by x-ray diffraction. Binding affinity studies toward Aß1-42 fibers were performed for the ligands and Re(I) complexes. The ability of formation of some 99mTc(I) complexes, their biodistribution and in vivo stability have been established. Results & conclusion: Complexes of stilbene and benzothiazole thiosemicarbazonates show similar affinity for amyloid-ß fibers to the free ligand. These 99mTc complexes present a reasonable in vivo stability and a low capability to cross the blood-brain barrier although not sufficient to brain amyloid imaging.

A monoclinic polymorph of 1,2-bis-[(1-methyl-1H-tetra-zol-5-yl)sulfan-yl]ethane (BMTTE).

The synthesis and crystal structure of a monoclinic (P21/c) polymorph of the title compound, C6H10S2N8, are reported. The mol-ecule has pseudo-twofold rotational symmetry, with the tetra-zole rings being inclined to one another by 5.50 (6)°. In the crystal, mol-ecules are linked by C-H⋯N hydrogen bonds, forming chains propagating along [101] and enclosing R22(20) ring motifs. The chains are linked by offset π-π inter-actions involving the tetra-zole rings [inter-centroid distances vary from 3.3567 (7) to 3.4227 (7) Å], forming layers parallel to the ac plane. The crystal structure of the triclinic polymorph (P [Formula: see text]) has been described previously [Li et al. (2011 ▸). Acta Cryst. E67, o1669].

Crystal structure of fac-tri-carbonyl-chlorido-bis-(4-hy-droxy-pyridine)-rhenium(I)-pyridin-4(1H)-one (1/1).

The asymmetric unit of the title compound, [ReCl(C5H5NO)2(CO)3]·C5H5NO, contains one mol-ecule of the complex fac-[ReCl(4-pyOH)2(CO)3] (where 4-pyOH represents 4-hy-droxy-pyridine) and one mol-ecule of pyridin-4(1H)-one (4-HpyO). In the mol-ecule of the complex, the Re atom is coordinated to two N atoms of the two 4-pyOH ligands, three carbonyl C atoms, in a facial configuration, and the Cl atom. The resulting geometry is slightly distorted octa-hedral. In the crystal structure, both fragments are associated by hydrogen bonds; two 4-HpyO mol-ecules bridge between two mol-ecules of the complex using the O=C group as acceptor for two different HO- groups of coordinated 4-pyOH from two neighbouring metal complexes. The resulting square arrangements are extented into infinite chains by hydrogen bonds involving the N-H groups of the 4-HpyO mol-ecule and the chloride ligands. The chains are further stabilized by π-stacking inter-actions.

Ligand-Driven Coordination Sphere-Induced Engineering of Hybride Materials Constructed from PbCl2 and Bis-Pyridyl Organic Linkers for Single-Component Light-Emitting Phosphors.

We report design and structural characterization of six new coordination polymers fabricated from PbCl2 and a series of closely related bis-pyridyl ligands LI and HLII-HLVI, namely, [Pb2(LI)Cl4]n, [Pb(HLII)Cl2]n·nMeOH, [Pb(HLIII)Cl2]n·0.5 nMeOH, [Pb2(LIV)Cl3]n, [Pb(HLV)Cl2]n, and [Pb3(LVI)2Cl4]n·nMeOH. The topology of the obtained networks is dictated by the geometry of the organic ligand. The structure of [Pb2(LI)Cl4]n is constructed from the [PbCl2]n two-dimensional (2D) sheets, linked through organic linkers into a three-dimensional framework, which exhibits a unique binodal 4,7-connected three-periodic topology named by us as sda1. Topological analysis of the 2D metal-organic sheet in [Pb(HLII)Cl2]n·nMeOH discloses a binodal 3,4-connected layer topology, regardless of the presence of tetrel bonds. A one-dimensional (1D) coordination polymer [Pb(HLIII)Cl2]n·0.5 nMeOH is considered as a uninodal 2-connected chain. The overall structure of [Pb2(LIV)Cl3]n is constructed from dimeric tetranuclear [Pb4(µ3-LIV-κ6N:N':N″:µ3-O)2(µ4-Cl)(µ2-Cl)2]3+ cationic blocks linked in a zigzag manner through bridging µ2-Cl- ligands, yielding a 1D polymeric chain. Topological analysis of this chain reveals a unique pentanodal 3,4,4,5,6-connected chain topology named by us as sda2. The structure of [Pb(HLV)Cl2]n exhibits a 1D zigzaglike polymeric chain. Two chains are further linked into a 1D gridlike ribbon through the dimeric [Pb2(µ2-Cl)2Cl2] blocks as bridging nodes. With the bulkiest ligand HLVI, a 2D layered coordination polymer [Pb3(LVI)2Cl4]n·nMeOH is formed, which network, considering all tetrel bonds, reveals a unique heptanodal 3,3,3,3,4,5,5-connected layer topology named by us as sda3. Compounds [Pb2(LI)Cl4]n, [Pb2(LIV)Cl3]n, and [Pb(HLV)Cl2]n were found to be emissive in the solid state at ambient temperature. While blue emission of [Pb2(LI)Cl4]n is due to the ligand-centered transitions, bluish-green and white luminescence of [Pb2(LIV)Cl3]n and [Pb(HLV)Cl2]n, respectively, was assigned to ligand-to-metal charge transfer mixed with metal-centered excited states. Molecular as well as periodic calculations were additionally applied to characterize the obtained polymers.

A new metal-organic polymeric system capable of stimuli-responsive controlled release of the drug ibuprofen.

A series of new zinc compounds has been prepared easily under mild synthetic conditions with the drug ibuprofen incorporated as a ligand to form different coordination polymers. The host materials have a high drug content and exhibit high stability, low cytotoxicity, good biodegradability and high biocompatibility. The ion exchange mechanism involved in the ibuprofen release process and the pH-controlled drug release have been studied.

A Hexameric Cationic Copper(II) Metallacrown as a Pertechnetate and Perrhenate Scavenger.

Materials based on the cationic copper(II) hexanuclear 18-membered metallacrown [18-MCCuII-N(2ph)-6](6+) (2phH=2-piconyl hydrazide) and tetrafluoroborate, perchlorate, nitrate, sulfate, and perrhenate anions were prepared by an easy method in aqueous medium. Single-crystal X-ray characterization of six members of this new family of complexes showed that the anions are attached to the metallacrown by direct coordination to a copper cation or by hydrogen-bonding interaction with the center of the hexamer. The stable cationic nature of the complexes and their ability to bind different anions allows them to adsorb and immobilize environmentally relevant anions such as MO4(-) (M=Tc, Re). The MO4(-) trapping capacities suggest that these materials would be useful in the treatment of oxoanionic contaminants in water.

Homo- and heteronuclear compounds with a symmetrical bis-hydrazone ligand: synthesis, structural studies, and luminescent properties.

Nine new coordination compounds have been synthesized by the reaction of salts of bivalent metal ions (a=Zn(II) , b=Cu(II) , c=Ni(II) , d=Co(II) ) with the bis(benzoylhydrazone) derivative of 4,6-diacetylresorcinol (H4 L). Three kinds of complexes have been obtained: homodinuclear compounds [M2 (H2 L)2 ]⋅nH2 O (1 a, 1 b, 1 c, and 1 d), homotetranuclear compounds [M4 (L)2 ]⋅n(solv) (2 a and 2 c), and heterotetranuclear compounds [Zn2 M2 (L)2 ]⋅n(solv) (2 ab, 2 ac, and 2 ad). The structures of the free ligand H4 L⋅2 DMSO and its complexes [Zn2 (H2 L)2 (DMSO)2 ] (1 a*), [Zn4 (L)2 (DMSO)6 ] (2 a*), and [Zn0.45 Cu3.55 (L)2 (DMSO)6 ]⋅2 DMSO (2 ab*) were elucidated by single-crystal X-ray diffraction. The ligand shows luminescence properties and its fluorimetric behavior towards M(II) metals (M=Zn, Cu, Ni and Co) has been studied. Furthermore, the solid-state luminescence properties of the ligand and compounds have been determined at room temperature. (1) H NMR spectroscopic monitoring of the reaction of H4 L with Zn(II) showed the deprotonation sequence of the OH/NH groups upon metal coordination. Heteronuclear reactions have also been monitored by using ESI-MS and spectrofluorimetric techniques.

Crystal structure of 1-(4-formyl-benzyl-idene)-4-methyl-thio-semicarbazone.

The structure of the title compound, C10H11N3OS, comprises an approximately planar mol-ecule, with the r.m.s. deviation for the 15 non-H atoms being 0.089 Å. The conformation about the imine bond is E and an intra-molecular N-H⋯N hydrogen bond is evident. Mol-ecules are linked into a supra-molecular chain along the b axis by N-H⋯S hydrogen bonds.

Crystal structure of 1-(4-formyl-benzyl-idene)thio-semicarbazone.

The asymmetric unit of the title compound, C9H9N3OS, contains two approximately planar mol-ecules (r.m.s. deviations for 14 non-H atoms = 0.094 and 0.045 Å), with different conformations. In one of them, the C=O group is syn to the S atom and in the other it is anti. Each mol-ecule features an intra-molecular N-H⋯N hydrogen bond, which generates an S(5) ring. In the crystal, mol-ecules are linked by N-H⋯O and N-H⋯S hydrogen bonds, generating discrete networks; the syn mol-ecules form [010] chains and the anti mol-ecules form (100) sheets.

Synthesis, characterization and binding affinities of rhenium(I) thiosemicarbazone complexes for the estrogen receptor (α/ß).

The binding affinities towards estrogen receptors (ERs) α and ß of a set of thiosemicarbazone ligands (HL(n)) and their rhenium(I) carbonyl complexes [ReX(HL(n))(CO)3] (X=Cl, Br) were determined by a competitive standard radiometric assay with [(3)H]-estradiol. The ability of the coordinated thiosemicarbazone ligands to undergo deprotonation and the lability of the ReX bond were used as a synthetic strategy to obtain [Re(hpy)(L(n))(CO)3] (hpy=3- or 4-hydroxypyridine). The inclusion of the additional hpy ligand endows the new thiosemicarbazonate complexes with an improved affinity towards the estrogen receptors and, consequently, the values of the inhibition constant (Ki) could be determined for some of them. In general, the values of Ki for both ER subtypes suggest an appreciable selectivity towards ERα.

Solid state structures of cadmium complexes with relevance for biological systems.

This chapter provides a review of the literature on structural information from crystal structures determined by X-ray diffractometry of cadmium(II) complexes containing ligands of potential biological interest. These ligands fall into three broad classes, (i) those containing N-donors such as purine or pyrimidine bases and derivatives of adenine, guanine or cytosine, (ii) those containing carboxylate groups such as α-amino acids, in particular the twenty essential ones, the water soluble vitamins (B-complex) or the polycarboxylates of EDTA type ligands, and (iii) S-donors such as thiols/thiolates or dithiocarbamates. A crystal and molecular structural analysis has been carried out for some representative complexes of these ligands, specifically addressing the coordination mode of ligands, the coordination environment of cadmium and, in some significant cases, the intermolecular interactions.

Metal coordination and in situ S-C bond cleavage of the bis(2-pyridylthio)methane ligand.

The compound [2bpytmH](2)[I(3)](2)[I(2)], which contains protonated 2bpytm, and four neutral monomeric complexes [CoCl(2)(2bpytm)]·H(2)O (1), [CoBr(2)(2bpytm)] (2), [CoI(2)(2bpytm)]·1/2H(2)O (3) and [NiBr(2)(2bpytm)]·H(2)O (4) have been obtained during a study into the reactivity of the bis(2-pyridylthio)methane (2bpytm) ligand towards cobalt(II) and nickel(II) halides. Furthermore, a cyclic dimer [CuBr(2)(2bpytm)](2) (5) and a 1D polymer [CuBr(2)(2bpytm)](n)·CH(3)CN (6) have been obtained from copper(II)/(I) bromide salts. An unprecedented S-CH(2)-S activation and cleavage in 2bpytm has been observed on using copper(II) salts with organic and voluminous inorganic anions. The cleavage of 2bpytm enabled the isolation of copper(II) complexes containing the in situ generated ligands 2-pyridinethiolate, 2-pyridinesulfenate or 2-pyridinesulfonate.

Molecular metallocycles, acyclic metallodimers and 2D coordination polymers containing the twisted ligand bis(pyrimidin-2-ylthio)methane.

The versatile coordination chemistry of bis(pyrimidin-2-ylthio)methane (bptm) allows the synthesis of a series of different metal complexes with diverse structures. We describe here the synthesis and structural characterization of three kinds of compounds: four cyclic dimers, [Co(2)Cl(4)(bptm)(2)] (1), [Zn(2)I(4)(bptm)(2)] (2), [Cd(2)I(4)(bptm)(2)] (3), [Cu(2)(NO(3))(4)(bptm)(2)] (4); two acyclic dimers, [Cu(2)Br(4)(bptm)(3)] (5), [Cu(2)(AcO)(4)(bptm)(2)] (6); and two 2D coordination polymers, [CuBr(bptm)] (7) and [CuI(bptm)] (8). Different structural models are obtained on making small changes in the building units under different synthetic conditions. The effects of the weak interactions in the crystal packing were also analyzed.

Synthesis and characterization of new trimeric rhenium(I) complexes. The influence of steric factors on the size of pyrazolonaterhenium(I) metallomacrocycles.

The reaction of [ReX(CO)5] with thiosemicarbazones H2L(R) derived from beta-keto esters (X = Cl, Br; R = Me, Ph) allowed the isolation of cyclic trimeric complexes [Re3(pyz(R))3(CO)9], where pyz(R) is the pyrazolonate corresponding to the thiosemicarbazone. Electron spray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) monitoring of the reactions of H2L(Ph) in toluene confirmed that the trimer was formed in the reaction mixture and no higher oligomer was detected. These studies, together with the X-ray structures of the trimeric complexes, afford new insight into the factors influencing the self-assembly of pyrazolonaterhenium(I) complexes.

Rhenium(I)-induced cyclization of thiosemicarbazones derived from beta-keto esters.

The reactions of methylacetoacetate and ethyl 2-methylacetoacetate thiosemicarbazones (H(2)L(A) and H(2)L(B), respectively) with [ReX(CO)(5)] and [ReX(CO)(3)(CH(3)CN)(2)] (X = Cl, Br) were explored under various experimental conditions. Besides the adducts fac-[ReX(CO)(3)(H(2)L)], in which the rhenium is coordinated to three carbonyl groups, the X anion, and the N,S-bidentate thiosemicarbazone ligand, the following complexes were also isolated: fac-[ReBr(CO)(3)(Hpyz(B))], the tetrameric complexes fac-[Re(pyz(A))(CO)(3)](4) and fac-[Re(pyz(B))(CO)(3)](4), and fac-[Re(pyz(B))(CO)(3)(H(2)O)] (where Hpyz(A) and Hpyz(B) are pyrazolones derived by cyclization of H(2)L(A) and H(2)L(B), respectively). The cyclization reactions were monitored by (1)H NMR spectroscopy and the complexes isolated were identified by elemental analysis, mass spectrometry, IR and (1)H NMR spectroscopy, and in some cases by X-ray diffractometry. The isolation and the full structural identification of the rather unusual fac-[ReBr(CO)(3)(Hpyz(B))], which contains the enol form of the pyrazolone ligand, affords new insight into the cyclization of thiosemicarbazones derived from beta-keto esters.