Solid State Structures of Lead Complexes with Relevance for Biological Systems.

Structural information on the interaction between lead ion and its targeting biological substances is important not only for enriching coordination chemistry of lead but for successfully treating lead poisoning that is a present-day problem. This chapter provides structural data, mainly metal binding sites/modes, observed in crystal structures of lead complexes with biorelevant molecules, obtained from the Cambridge Structural Database (the CSD version 5.36 updated to May 2015) and the Protein Data Bank (PDB updated to February 2016). Ligands include (i) amino acids and small peptides, (ii) proteins, (iii) nucleic acid constituents, (iv) nucleic acids, (v) simple saccharides, and (vi) other biorelevant molecules involving lead-detoxification agents. For representative complexes of these ligands, some details on the environment of the metal coordination and structural characteristics are described.

Solid State Structures of Alkali Metal Ion Complexes Formed by Low-Molecular-Weight Ligands of Biological Relevance.

This chapter provides structural data, mainly metal binding sites/modes, observed in crystal structures of alkali metal ion complexes containing low-molecular-weight ligands of biological relevance, mostly obtained from the Cambridge Structural Database (the CSD version 5.35 updated to February 2014). These ligands include (i) amino acids and small peptides, (ii) nucleic acid constituents (excluding quadruplexes and other oligonucleotides), (iii) simple carbohydrates, and (iv) naturally occurring antibiotic ionophores. For some representative complexes of these ligands, some details on the environment of the metal coordination and structural characteristics are described.

Two hydrate pseudopolymorphs of thiamine pyrophosphate: a dihydrate and a trihydrate.

Two hydrate pseudopolymorphs of 3-[(4-amino-2-methylpyrimidin-1-ium-5-yl)methyl]-4-methyl-1,3-thiazol-3-ium-5-yl hydrogen pyrophosphate (TPP), viz. a dihydrate, C12H18N4O7P2S·2H2O, (I), and a trihydrate, C12H18N4O7P2S·3H2O, (II), were obtained during a structural study of vitamin B1 coenzyme. In both compounds, TPP is a neutral zwitterion, with its pyrophosphate group doubly deprotonated and its pyrimidine ring protonated, and it assumes the usual `F' conformation in terms of the two torsion angles about the bonds by which the methylene group links the thiazolium and pyrimidinium rings [1.1 (3) and 79.7 (3)° for (I), and 2.0 (3) and 75.5 (3)° for (II)]. In (I), two TPP molecules are linked by a pair of O-H···O hydrogen bonds into a phosphate-pairing dimer. N-H···O hydrogen bonds connect the dimers into a sheet parallel to (101). In (II), the TPP molecules are self-assembled solely by N-H···O hydrogen bonds, generating a tape structure along [001]. A comparison of the four known hydrate pseudopolymorphs of TPP shows that the phosphate-pairing dimers are basic building units for the formation of two-dimensional networks.

Poly[[tris-(µ-4,4'-bipyridine-κ(2)N:N')bis-(µ-l-lysinato-κ(3)N(1),O(1):O(1'))dizinc(II)] tetra-nitrate 0.6-hydrate dimethyl-formamide disolvate].

In the title compound, {[Zn(2)(C(6)H(14)N(2)O(2))(2)(C(10)H(8)N(2))(3)](NO(3))(4)·0.6H(2)O·2C(3)H(7)NO}(n), the Zn(II) ion is six-coordinated with a distorted octa-hedral geometry by two carboxyl-ate O atoms and one amino N atom from two l-lysinate (l-lys) ligands, and three N atoms from three 4,4'-bipyridine (4,4'-bipy) ligands. The Zn(II) ions are connected by the carboxyl-ate groups of the l-lys ligands in the a-axis direction and the bridging 4,4'-bipy ligands in the b- and c-axis directions, forming a three-dimensional cationic framework with channels along [100]. The nitrate anions and solvent water and dimethyl-formamide (DMF) mol-ecules are located in the channels and linked to the cationic framework by N-H⋯O and O-H⋯O hydrogen bonds. The occupancy of the water mol-ecule was fixed at 0.6. One of the DMF mol-ecules is disordered over two sets of sites, with an occupancy ratio of 0.632:0.368 (11).

Poly[di-µ(3)-hy-droxy[µ(4)-5-(4-carb-oxy-phen-yl)pyridine-2-carboxyl-ato-κ(5)N,O(2):O(2'):O(4):O(4')]dicadmium].

The asymmetric unit of the title polymeric complex, [Cd(2)(C(13)H(7)NO(4))(OH)(2)](n), consists of two independent Cd(II) atoms, one 5-(4-carb-oxy-phen-yl)pyridine-2-carboxyl-ate ligand and two hy-droxy groups. One Cd(II) atom is six-coordinated by two O atoms from two ligand mol-ecules and by four µ(3)-OH groups in a distorted trigonal-prismatic geometry. The other is five-coordinated by one N and two O atoms from two ligands and by two µ(3)-OH groups, forming a distorted square-pyramidal geometry. The two independent Cd(II) atoms are connected by the ligand mol-ecules and the OH groups into a three-dimensional framework. O-H⋯O hydrogen bonds between the OH groups and the carboxyl-ate O atoms are observed.

catena-Poly[[[aqua-bis-(4,4'-bipyridine-κN)zinc]-µ-l-tyrosinato-κN,O:O] nitrate dihydrate].

In the title compound, {[Zn(C(9)H(10)NO(3))(C(10)H(8)N(2))(2)(H(2)O)]NO(3)·2H(2)O}(n), the Zn(II) atom is six-coordinated in a distorted octa-hedral geometry by two carboxyl-ate O atoms and one amino N atom from two l-tyrosinate ligands, two N atoms from two 4,4'-bipyridine ligands, and one water mol-ecule. Adjacent Zn atoms are bridged by the bidentate carboxyl-ate groups into a cationic chain extending along [010]. N-H⋯N, O-H⋯N and O-H⋯O hydrogen bonds link the cationic chains, nitrate anions and uncoordinated water mol-ecules into a supra-molecular network. π-π inter-actions between the pyridine rings and between the pyridine and benzene rings [centroid-centroid distances = 3.615 (4) and 3.636 (4) Å] are present.

Interaction of thiamine with anions in the triclinic form of thiamine iodide: 3-[(4-amino-2-methylpyrimidin-5-yl)methyl]-5-(2-hydroxyethyl)-4-methyl-1,3-thiazol-3-ium iodide 1.25-hydrate.

The asymmetric unit of the title compound, C(12)H(17)N(4)OS(+)·I(-)·1.25H(2)O, contains two crystallographically independent molecules. Both formula units assume the usual F conformation and have the hydroxyethyl group disordered over two sites, each with half occupation. Two thiamine cations are linked by hydrogen bonds into a cyclic dimer. These dimers are further connected by base-pairing hydrogen bonds into a chain along [010]. The stacked dimers form channels, which are occupied by iodide anions. The cations and anions are associated by N-H...I hydrogen bonds, C-H...I interactions and I...thiazolium ring close contacts. The interactions between thiamine and the iodide anions are similar to those observed in monoclinic thiamine iodide 1.5-hydrate [Hu & Zhang (1993). J. Inclusion Phenom. Mol. Recognit. Chem. 16, 273-281].

Synthesis and characterization of the titanium complexes bearing two ß-enaminoketonato ligands with electron withdrawing groups/modified phenyls and their behaviors for ethylene (co-)polymerization.

A series of new titanium complexes with two asymmetric bidentate ß-enaminoketonato [N,O] ligands (2b-t), [PhN=C(CF(3))CHC(Ar)O](2)TiCl(2) (2b, Ar = -C(6)H(4)F(o); 2c, Ar = -C(6)H(4)F(m); 2d, Ar = -C(6)H(4)F(p); 2e, Ar = -C(6)H(4)Cl(p); 2f, Ar = -C(6)H(4)OMe(p); 2g, Ar = -C(6)H(4)CF(3)(p); 2h, Ar = -C(6)H(4)CF(3)(m); 2i, Ar = -C(6)H(4)CF(3)(o); 2j, Ar = -C(6)H(4)Cl(o); 2k, Ar = -C(6)H(4)Br(o); 2l, Ar = -C(6)H(4)I(o); 2m, Ar = -C(6)H(3)F(2)(2,4); 2n, Ar = -C(6)H(3)F(2)(2,6); 2o, Ar = -C(6)H(3)F(2)(3,4); 2p, Ar = -C(6)H(3)F(2)(3,5); 2q, Ar = -C(6)F(5); 2r, Ar = C(6)F(4)OMe; 2s, Ar = -C(6)H(3)Cl(2)(2,6); 2t, Ar = -C(6)H(3)Cl(2)(2,5)), have been synthesized based on substituted acetophenones. X-Ray analyses reveal that complexes 2h, 2k, 2m, and 2n adopt distorted octahedral geometry around the titanium center, in which the two chloride ligands are situated in the cis-orientation. 2s also adopts distorted octahedral geometry, but the two chloride ligands in it are situated in the trans-orientation due to the increase of the steric effect of the phenyl derived from the acetophenone. The influence of the substituent effects on catalyst performance, including catalytic activities and the molecular weight distribution of the polymers obtained, was investigated in detail. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 2b-r and 2t are active catalysts for ethylene polymerization at room temperature, and produce high molecular weight polymers. It is observed that the catalytic activities are significantly enhanced by introducing some electron-withdrawing groups, such as -F, -Cl and -CF(3), into the suitable positions of the phenyl ring close to the oxygen donor. It should be noted that complexes 2c-i, 2p, 2n and 2t are also capable of promoting the living copolymerization of ethylene with norbornene at room temperature, yielding high molecular weight copolymers with narrow molecular weight distributions (PDI = 1.05-1.30).

Novel vanadium(III) complexes with bidentate N,N-chelating iminopyrrolide ligands: synthesis, characterization and catalytic behaviour of ethylene polymerization and copolymerization with 10-undecen-1-ol.

A series of novel vanadium(III) complexes bearing iminopyrrolide chelating ligands [2-(RN=CH)C4H3N]V(THF)2Cl2 (2a: R = cyclohexyl; 2b: R = Ph; 2c: R = 2,6-iPr2C6H3; 2d: R = p-CF3C6H4; 2e: R = C6F5) have been synthesized and characterized. Single-crystal X-ray diffraction revealed that complexes 2a, 2c and 2e adopt an octahedral geometry around the vanadium center. In the presence of Et2AlCl as a co-catalyst, these complexes displayed high catalytic activities up to 48.6 kg PE mmol(V)(-1) h(-1) bar(-1) for ethylene polymerization, and produced high molecular weight polymers. 2a-e/Et2AlCl catalytic systems were tolerant to elevated temperature (70 degrees C) and yielded unimodal polyethylenes, indicating the single site behaviour of these catalysts. By pre-treating with equimolar amounts of alkylaluminums, functional alpha-olefin 10-undecen-1-ol can be efficiently incorporated into polyethylene chains. 10-Undecen-1-ol incorporation can easily reach 15.8 mol% under the mild conditions. When compared with VCl3(THF)3 or rac-Et[Ind]2ZrCl2, these vanadium(III) complexes exhibited higher activities towards the copolymerization, and can incorporate more 10-undecen-1-ol into polymer chains under the similar conditions.

Constructing mixed-metal coordination polymers from copper(II)-pyridinedicarboxylate metalloligands.

In the mixed-metal complex catena-poly[bis[diaquasilver(I)] [bis[aquacopper(II)]-mu(3)-pyridine-2,5-dicarboxylato-2':1:1'kappa(5)N,O(2):O(5):O(5),O(5')-mu-pyridine-2,5-dicarboxylato-2:1kappa(4)N,O(2):O(5),O(5')-disilver(I)-mu(3)-pyridine-2,5-dicarboxylato-1:1':2''kappa(5)O(5),O(5'):O(5):N,O(2)-mu-pyridine-2,5-dicarboxylato-1':2'''kappa(4)O(5),O(5'):N,O(2)] hexahydrate], {[Ag(H(2)O)(2)][AgCu(C(7)H(3)NO(4))(2)(H(2)O)].3H(2)O}(n), a square-pyramidal Cu(II) center is coordinated by two N atoms and two O atoms from two pyridine-2,5-dicarboxylate (2,5-pydc) ligands and a water molecule, forming a [Cu(2,5-pydc)(2)(H(2)O)](2-) metalloligand. One Ag(I) center is coordinated by five O atoms from three 2,5-pydc ligands and, as a result, the [Cu(2,5-pydc)(2)(H(2)O)](2-) metalloligands act as linkers in a unique mu(3)-mode connecting Ag(I) centers into a one-dimensional anionic double chain along the [101] direction. The other Ag(I) center is coordinated by two water molecules, forming an [Ag(H(2)O)(2)](+) cation. Four adjacent Ag(I) centers are associated by Ag...Ag interactions [3.126 (1) and 3.118 (1) A], producing a Z-shaped Ag(4) unit along the [010] direction and connecting the anionic chains into a two-dimensional layer structure. This study offers information for engineering mixed-metal complexes based on copper(II)-pyridinedicarboxylate metalloligands.

Poly[[diaqua-mu-4,4'-bipyridine-dinitratodi-mu-L-tyrosinato-dicopper(II)]: a chiral two-dimensional coordination polymer.

The title compound, [Cu(2)(C(9)H(10)NO(3))(2)(NO(3))(2)(C(10)H(8)N(2))(H(2)O)(2)](n), contains Cu(II) atoms and L-tyrosinate (L-tyr) and 4,4'-bipyridine (4,4'-bipy) ligands in a 2:2:1 ratio. Each Cu atom is coordinated by one amino N atom and two carboxylate O atoms from two L-tyr ligands, one N atom from a 4,4'-bipy ligand, a monodentate nitrate ion and a water molecule in an elongated octahedral geometry. Adjacent Cu atoms are bridged by the bidentate carboxylate groups into a chain. These chains are further linked by the bridging 4,4'-bipy ligands, forming an undulated chiral two-dimensional sheet. O-H...O and N-H...O hydrogen bonds connect the sheets in the [100] direction. This study offers useful information for the engineering of chiral coordination polymers with amino acids and 4,4'-bipy ligands by considering the ratios of the metal ion and organic components.

A polymorph of diaqua-bis(pyrazine-2-carboxyl-ato-κN,O)copper(II).

The title compound, [Cu(C(5)H(3)N(2)O(2))(2)(H(2)O)(2)], is a new polymorph of the previously reported compound [Klein et al. (1982 ▶). Inorg. Chem.21, 1891-1897]. The Cu(II) atom, lying on an inversion center, is coordinated by two N atoms and two O atoms from two pyrazine-2-carboxyl-ate ligands and by two water mol-ecules in a distorted octa-hedral geometry with the water mol-ecules occupying the axial sites. Inter-molecular O-H⋯O, O-H⋯N and C-H⋯O hydrogen bonds connect the complex mol-ecules into a two-dimensional layer parallel to (10), whereas the previously reported polymorph exhibits a three-dimensional hydrogen-bonded network.

catena-Poly[diammonium [diaqua-bis(pyridine-2,4-dicarboxyl-ato-κN,O)cuprate(II)] [[diaqua-copper(II)]-µ-pyridine-2,4-dicarboxyl-ato-κN,O:O-[tetra-aqua-cadmium(II)]-µ-pyridine-2,4-dicarboxyl-ato-κO:N,O] hexa-hydrate].

The title mixed-metal complex, {(NH(4))(2)[Cu(C(7)H(3)NO(4))(2)(H(2)O)(2)][CdCu(C(7)H(3)NO(4))(2)(H(2)O)(6)]·6H(2)O}(n), contains one octa-hedrally coordinated Cd(II) center and two octa-hedrally coordinated Cu(II) centers, each lying on an inversion center. The two Cu(II) atoms are each coordinated by two O atoms and two N atoms from two 2,4-pydc (2,4-H(2)pydc = pyridine-2,4-dicarboxylic acid) ligands in the equatorial plane and two water mol-ecules at the axial sites, thus producing two crystallographically independent [Cu(2,4-pydc)(2)(H(2)O)(2)](2-) metalloligands. One metalloligand exists as a discrete anion and the other connects the Cd(H(2)O)(4) units, forming a neutral chain. O-H⋯O and N-H⋯O hydrogen bonds connects the polymeric chains, complex anions, ammonium cations and uncoordinated water mol-ecules into a three-dimensional supra-molecular network.

Assembly of the highest connectivity Wells-Dawson polyoxometalate coordination polymer: the use of organic ligand flexibility.

Through tuning the length of flexible bis(triazole) ligands and different metal ion coordination geometries, four Wells-Dawson polyoxoanion-based hybrid compounds, [Cu 6(btp) 3(P 2W 18O 62)].3H 2O ( 1) (btp = 1,3-bis(1,2,4-triazol-1-y1)propane), [Cu 6(btb) 3((P 2W 18O 62)].2H 2O ( 2), [Cu 3(btb) 6(P 2W 18O 62)].6H 2O (btb = 1,4-bis(1,2,4-triazol-1-y1)butane) ( 3), and [Cu 3(btx) 5.5((P 2W 18O 62)].4H 2O (btx = 1,6-bis(1,2,4-triazol-1-y1)hexane) ( 4), were synthesized and structurally characterized. In compound 1, the metal-organic motif exhibits a ladder-like chain, which is further fused by the ennead-dentate [P 2W 18O 62] (6-) anions to construct a 3D structure. In compound 2, the metal-organic motif exhibits an interesting Cu-btb grid layer, and the ennead-dentate polyoxoanions are sandwiched by two Cu-btb layers to construct a 3D structure. Compound 3 exhibits a (4 (2).6 (2).8 (2)) 3D Cu-btb framework with square and hexagonal channels arranged alternately. The hexa-dentate polyoxoanions incorporate only into the hexagonal channels. In compound 4, there exist two sets of (6 (1).10 (2)) 2(6 (1).8 (2).10 (3)) 3D Cu-btx frameworks to generate a 2-fold interpenetrated structure into which the penta-dentate polyoxoanions are inserted to construct a 3D structure. The structural analyses reveal that the length of flexible bis(triazole) ligands and metal ion coordination geometries have a synergic influence on the structures of this series. To our knowledge, they have the highest connectivity for the Wells-Dawson polyoxometalate coordination polymers to date.

High-dimensional assembly depending on polyoxoanion templates, metal ion coordination geometries, and a flexible bis(imidazole) ligand.

By introducing the flexible 1,1'-(1,4-butanediyl)bis(imidazole) (bbi) ligand into the polyoxovanadate system, five novel polyoxoanion-templated architectures based on [As(8)V(14)O(42)](4-) and [V(16)O(38)Cl](6-) building blocks were obtained: [M(bbi)(2)](2)[As(8)V(14)O(42)(H(2)O)] [M = Co (1), Ni (2), and Zn (3)], [Cu(bbi)](4)[As(8)V(14)O(42)(H(2)O)] (4), and [Cu(bbi)](6)[V(16)O(38)Cl] (5). Compounds 1-3 are isostructural, and they exhibit a binodal (4,6)-connected 2D structure with Schläfli symbol (3(4) x 4(2))(3(4) x 4(4) x 5(4) x 6(3))(2), in which the polyoxoanion induces a closed four-membered circuit of M(4)(bbi)(4). Compound 4 exhibits an interesting 3D framework constructed from tetradentate [As(8)V(14)O(42)](4-) cluster anions and cationic ladderlike double chains. There exists a bigger M(8)(bbi)(6)O(2) circuit in 4. The 3D extended structure of 5 is composed of heptadentate [V(16)O(38)Cl](6-) anions and flexural cationic chains; the latter consists of six Cu(bbi) segments arranged alternately. It presents the largest 24-membered circuit of M(24)(bbi)(24) so far observed made of bbi molecules and transition-metal cations. Investigation of their structural relations shows the important template role of the polyoxoanions and the synergetic interactions among the polyoxoanions, transition-metal ions, and flexible ligand in the assembly process. The magnetic properties of compounds 1-3 were also studied.

Tetraaqua(1,10-phenanthroline-kappa(2)N,N')cobalt(II) dinitrate: a hydrogen-bonded supramolecular network.

The structure of the title compound, [Co(C(12)H(8)N(2))(H(2)O)(4)](NO(3))(2), consists of tetraaqua(1,10-phenanthroline)cobalt(II) cations and nitrate anions. The Co atom is located on a twofold rotation axis and is coordinated by the two N atoms of a 1,10-phenanthroline ligand and four O atoms of water molecules. The cations and anions are linked by hydrogen-bond interactions into a three-dimensional supramolecular network.

Poly[di-mu3-chloro-mu2-trans-1,2-di-4-pyridylethylene-dicopper(I)]: a two-dimensional organic-inorganic hybrid constructed from linear CuCl clusters and bridging ligands.

The structure of the title compound, [Cu2Cl2(C12H10N2)](n), contains infinite CuCl staircase-like chains, which lie about inversion centres. The trans-1,2-di-4-pyridylethylene molecules also lie about inversion centres and connect the CuCl chains through Cu-N coordination bonds into a two-dimensional organic-inorganic hybrid network. The planar sheets are stacked along the c axis and associated through weak C-H...Cl interactions. The results show a reliable structural motif with controllable separation of the CuCl chains by variation of the length of the ligand.

Interactions of thiamine with polymeric halogenocadmate anions in the organic-inorganic hybrid compound (thiaminium)[Cd3Br4.4Cl3.6].

The structure of poly[3-[(4-amino-2-methylpyrimidin-1-ium-5-yl)methyl]-5-(2-hydroxyethyl)-4-methylthiazolium octa-mu-bromo/chloro(4.4/3.6)-tricadmate(II)], [(C12H18N4OS)[Cd3 Br4.41Cl3.59]]n consists of hydrogen-bonded thiamine molecules and polymeric cadmium bromide/chloride anions in an organic-inorganic hybrid fashion. The one-dimensional anion ribbons are formed by edge-sharing octahedra and vertex-sharing tetrahedra. Thiamine molecules adopting the S conformation are linked to anions via three types of interactions, namely an N(amino)-H...anion...thiazolium bridging interaction, an N(pyrimidine)-H...anion hydrogen bond and an O(hydroxy)-H...anion hydrogen bond.

The new polynuclear titanium(IV) complex [(Cp*TiCl)(mu-O)2(Cp*Ti)2(mu-O)(mu-O)2]2Ti (Cp* is eta5-C5Me5).

A new polynuclear titanium(IV) complex, dichlorodeca-mu2-oxo-hexakis(pentamethylcyclopentadienyl)hexatitanium(IV), [Ti6(C10H15)6Cl2O10], has been synthesized by hydrolysis of a titanium complex bearing an N-(2-hydroxy-3,5-dimethylbenzyl)diethanolamine Mannich ligand. The molecule has two O-bridged Ti3O3 rings linked to two similar rings through a tetrahedrally O-coordinated Ti atom. All Ti atoms except the central one are coordinated to pentamethylcyclopentadienyl (Cp*) ligands. The Cp* ligands are arranged with approximate symmetry with respect to the Ti/O/Cl core.

Thiamine tetraphenylborate monohydrate: a two-dimensional hydrogen-bonded network with (4,4)-topology.

The title compound, 3-[(4-amino-2-methylpyrimidin-5-yl)methyl]-5-(2-hydroxyethyl)-4-methylthiazolium tetraphenylborate monohydrate, C12H17N4OS+.C24H20B-.H2O, is a salt in which the thiamine cations are linked by hydrogen bonds into a two-dimensional network having (4,4)-topology. The stacked sheets form channels, which are occupied by the anions; the cations and anions are linked by C-H...pi(arene) hydrogen bonds.