Synthesis and characterisation of a new vanadyl oxalatophosphate compound: (C10H10N2)[(VO)(HPO4)]2(C2O4)

A new vanadyl oxalatophosphate compound, (C₁₀H₁₀N₂)[(VO)(HPO₄)]₂(C₂O₄), was synthesized via the hydrothermal approach and characterised structurally using single-crystal X-ray diffraction, FT-IR and thermogravimetric analysis. The compound has two-dimensional anionic layers with occupying the interlayer spaces.     

Seven organic-inorganic hybrid compounds constructed from 2,4,6-tris-(pyridyl)-1,3,5-triazine and polyoxometalates

Seven new organic-inorganic hybrid compounds containing inorganic polyoxometalates and trigonal organic ligand 2,4,6-tris-(3/4-pyridyl)-1,3,5-triazine (3/4-tpt), namely [Mo₈O₂₆M(Htpt)₂(H₂O)₂]_n (M = Zn (1), Co (2), Ni (3)), [Mo₈O₂₆Cu(Htpt)₂(H₂O)₂]_n·2nH₂O (4), [Mo₈O₂₆(H₂tpt)₂]·6H₂O (5), [Mn(Mo₄O₁₃)(4-tpt)₂]_n (6) and [Fe₃(Mo₄O₁₅)(3-tpt)]_n·nH₂O (7), were synthesized hydrothermally and characterized by EA, IR, TG, and PXRD techniques. Single crystal X-ray structural analysis revealed that compounds 1-4 are 1-D coordination polymers constructed from [Mo₈O₂₆]⁴⁻ cluster and [M(Htpt)₂(H₂O)₂]⁴⁺ fragments. Compound 5 is an isolated cluster composed of [Mo₈O₂₆]⁴⁻ anion and monodentate H₂tpt²⁺ cation. 3-Tpt ligands in 1-5 are partially protonated and act as monodentate ligands. Octamolybdates adopt β- and γ-[Mo₈O₂₆]⁴⁻ structural mode in compounds 1-4 and 5, respectively. In compound 6, each [Mo₄O₁₃]²⁻ tetramer links four Mn(II) ions to form a 2-D wave-like polymeric layer. The 2-D [MnMo₄O₁₃] bimetallic layers are pillared by neutral 4-tpt bidentately to generate a 3-D metal-organic framework. Compound 7 is a 3-D coordination polymer constructed from 2-D [Fe₃(Mo₄O₁₅)] bimetallic polymeric layer and pillared by neutral tridentate 3-tpt. These compounds are thermal stable under 250 °C. The compounds 1 and 5 display luminescence with emission maximum at 481 and 442 nm, respectively.     

Syntheses and characterizations of four mixed-ligand hydrogen bonding supramolecular architectures with different structural motifs

The reactions of 4-aminobenzoic acid (4-abaH), 4,4′-bipyridine (4,4′-bipy) and transitional metal ions (Zn^II, Mn^II and Cu^II) gave rise to four supramolecular architectures, namely, [(4-abaH)₂(4,4′-bipy)] (1), {[Zn₂(4,4′-bipy)₂(4-aba)₄] (H₂O)₅}_n (2), {[Mn(4,4′-bipy)₂(H₂O)₄] (4-aba)Br(H₂O)₃} (3) and {[Cu₂(4,4′-bipy)₃(H₂O)₂(4-aba)₂](NO₃)₂(H₂O)₄}_n (4). Their crystal structures were determined by X-ray diffraction and show different structural motifs. 1 is a one-dimensional hydrogen bonding ladder constructed by 4-abaH and 4,4′-bipy. In 2, 4,4′-bipy bridges Zn(4-aba)₂ units forming a one-dimensional zigzag chain, which is extended into a three-dimensional framework by crystalline water molecules through hydrogen bonding interactions. Three-dimensional network of 3 is constructed by mononuclear [Mn(4,4′-bipy)₂(H₂O)₄]²⁺ cations, neutral crystalline water molecules, and 4-aba and Br⁻ anions through extensive hydrogen bonding and π-π interactions. However, one-dimensional ladder formed by 4,4′-bipy and Cu(4-aba) units in 4 is extended into a three-dimensional architecture through interpenetration of the lateral 4-aba arms into squares of the adjacent Cu-(4,4′-bipy) ladders and extensive hydrogen bonding interactions.     

A novel three-dimensional hybrid framework based on fishbone-like copper halide inorganic units

A novel inorganic-organic hybrid cuprous chloride, , has been hydrothermally synthesized and structurally characterized by the elemental analyses, IR spectrum, TG analysis and the single crystal X-ray diffraction. The structure of 1 exhibits a three-dimensional network built up from unusual fishbone-like copper(I) chloride ribbons bridged by linear isonicotinato ligands. Its luminescent property was also investigated.     

Synthesis, structure, and characterization of two polyoxometalate-photosensitizer hybrid materials

Two hybrid materials based on the tris(bipyridine)ruthenium(II), [Ru(bpy)₃]²⁺ and Keggin-type polyoxometalates, [PW₁₁O₃₉]⁷⁻ and [PW₁₂O₄₀]³⁻, namely, [Ru(bpy)₃][K₅PW₁₁O₃₉] (1) and [Ru(bpy)₃][KPW₁₂O₄₀] (2) were synthesized. X-ray crystallographic study of the red-colored complex, 2, shows that it crystallizes in the orthorhombic space group P_bcn and the polyanions are associated with the [Ru(bpy)₃]²⁺ counterions by Coulombic forces and supramolecular interactions. The molecular complex is further connected and forms a three-dimensional framework through C-H?O_POM and other weak interactions. These complexes were further characterized by FT-IR, UV-Vis, ¹H and ³¹P NMR, luminescent spectra and computational studies. Significantly, these combined spectroscopic studies show that these polyoxometalate-dye hybrids have strong electronic interactions between the cationic dye and polyanion units.     

A series of inorganic-organic hybrid compounds constructed from bis(undecatungstophosphate) lanthanates and copper-organic units

A series of inorganic-organic hybrid compounds built from bis(undecatungstophosphate) lanthanates and copper-complexes, namely, H₈[Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][La(PW₁₁O₃₉)₂]}₂·18H₂O (1), H₆[Na₂(en)₂(H₂O)₅][Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][Ce(PW₁₁O₃₉)₂]}₂·16H₂O (2), H₆[Na₂(en)₂(H₂O)₅][Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][Pr(PW₁₁O₃₉)₂]}₂·18H₂O (3), H₆[Na₂(en)₂(H₂O)₄][Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][Nd(PW₁₁O₃₉)₂]}₂·14H₂O (4), H₆[Na₂(en)₂(H₂O)₅][Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][Sm(PW₁₁O₃₉)₂]}₂·20H₂O (5), and H₇[Cu(en)₂]₂[Sm(PW₁₁O₃₉)₂]·10H₂O (6) (where en = 1,2-ethylenediamine), have been prepared. In these compounds, two lacunary [PW₁₁O₃₉]⁷⁻ anions sandwich an eight-coordinated Ln(III) cation to yield [Ln(PW₁₁O₃₉)₂]¹¹⁻ anion in a twisted square anti-prismatic geometry, which is further bridged by [Cu(en)₂]²⁺ fragments to generate a 1D zigzag-like chain. In 1-6, the coordination bond interactions and weak interactions between adjacent 1D chains play an important role in the zigzagging distances and angles of different 1D chains. The magnetic studies indicate that antiferromagnetic interactions exist in compounds 1, 2 and 4.     

K2Fe(C2O4)(HPO4)(OH2) · H2O: A layered oxalatophosphate hybrid material

One novel layered oxalatophosphate structure K₂Fe(C₂O₄)(HPO₄)(OH₂) · H₂O (1) has been synthesized by hydrothermal method. X-ray crystallography reveals that the complex 1 possesses a 2D layered structure constructed from octahedral FeO₆, tetrahedral moieties and multidentate oxalate ligands with the K⁺ cations among the layers. It is noteworthy that the oxalate anion as a tetradentate ligand bonds to three iron atoms in bidentate-chelating mode on one side and in monodentate-bridging mode on the other, thus forming a neutral iron oxalate sheet. This new structural feature can be considered as the third role of the oxalate ions in metal oxalatophosphate chemistry.     

Hydrothermal synthesis and structure characterization of the first organically templated metal iodates

The first organically templated molybdenum iodates (C₅H₆N)₂Mo₂O₅(IO₃)₄(H₂O)₂ (1), (C₁₀H₈N₂)[MoO₂(IO₃)₃] · H₃O (2), and uranium iodate (C₅H₅N)₂[(UO₂)(IO₃)₃](IO₃) (3), have been successfully synthesized under mild hydrothermal conditions. Compound 1 is simple zero-dimensional units consisting of [(Mo₂O₅(IO₃)₄)]²⁻ anions, which can be described as a tetranuclear unit hanged on either side by two [IO₃] groups. The [Mo₂O₅(IO₃)₄]²⁻ anions are in a close connection through the water molecules and protonated pyridine cations, via hydrogen bonds and intermolecular actions. Compound 2 is built up from [MoO₆] octahedra and [IO₃] pyramids to two-dimensional layers, in which 4,4′-bipy molecules and water cations are located, forming strong hydrogen bonds with the inorganic framework, leading to pseudo three-dimensional structure. Compound 3 is one-dimensional ribbons containing {[(UO₂)(IO₃)₃](IO₃)}²⁻ anions and charge neutrality is achieved by the protonated 4,4′-bipy cations, which reside between two ribbons, forming hydrogen bonds with the inorganic framework and resulting in pseudo two-dimensional structure. Crystal data are as follows: (C₅H₆N)₂Mo₂O₅(IO₃)₄(H₂O)₂ (1), orthorhombic, Pnma, a = 24.097(5) Å, b = 13.532(3) Å, c = 7.836(16) Å, Z = 4, V = 2555.2(9) Å³; (C₁₀H₈N₂)[MoO₂(IO₃)₃] · H₃O (2), monoclinic, C2/c, a = 24.176(5) Å, b = 10.751(2) Å, c = 7.5074(15) Å, β = 107.44(3)°, Z = 8, V = 1861.6(6) Å³; (C₅H₅N)₂[(UO₂)(IO₃)₃](IO₃) (3), monoclinic, P2₁/n, a = 14.430(3) Å, b = 7.3459(15) Å, c = 19.811(4) Å, β = 106.70(3)°, Z = 4, V = 2011.3(7) Å³.     

Enzyme stabilization by nano/microsized hybrid materials

Immobilization is a key technology for successful realization of enzyme‐based industrial processes, particularly for production of green and sustainable energy or chemicals from biomass‐derived catalytic conversion. Different methods to immobilize enzymes are critically reviewed. In principle, enzymes are immobilized via three major routes (i) binding to a support, (ii) encapsulation or entrapment, or (iii) cross‐linking (carrier free). As a result, immobilizing enzymes on certain supports can enhance storage and operational stability. In addition, recent breakthroughs in nano and hybrid technology have made various materials more affordable hosts for enzyme immobilization. This review discusses different approaches to improve enzyme stability in various materials such as nanoparticles, nanofibers, mesoporous materials, sol–gel silica, and alginate‐based microspheres. The advantages of stabilized enzyme systems are from its simple separation and ease recovery for reuse, while maintaining activity and selectivity. This review also considers the latest studies conducted on different enzymes immobilized on various support materials with immense potential for biosensor, antibiotic production, food industry, biodiesel production, and bioremediation, because stabilized enzyme systems are expected to be environmental friendly, inexpensive, and easy to use for enzyme‐based industrial applications.     

Synthesis and characterization of cellulose/silica hybrid materials with chemical crosslinking

The cellulose/silica hybrid biomaterials are prepared by sol–gel covalent crosslinking process. The tetraethoxysilane (TEOS) as precursor, γ-aminopropyltriethoxylsilane (APTES) as couple agent, and 2,4,6-tri[(2-epihydrin-3-bimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-EBAC) as crosslinking agent, are used in the sol–gel crosslinking process. The chemical and morphological structures of cellulose/silica covalent crosslinking hybrids are investigated with micro-FT-IR spectra, nitrogen element analysis, X-ray diffraction, SEM, AFM, and DSC. The results show that the cellulose/silica hybrids form new macromolecular structures. In sol–gel process, inorganic particles are dispersed at the nanometer scale in the cellulose host matrix, bounding to the cellulose through covalent bonds. The cellulose/silica covalent crosslinking hybrid can form good and smooth film on the cellulose. The thermal properties of organic/inorganic hybrids are improved.     

Synthesis and crystal structures of four pH-dependent Pb(II) and Cd(II) phosphonates based on a novel ligand, 3-phosphono-benzoic acid

Four metal phosphonate hybrid compounds, [Pb(Hpbc)] (1), [Pb₃(pbc)₂(H₂O)₂] (2), [Cd(H₂pbc)₂(H₂O)₂] (3) and [Cd_1.5(pbc)(H₂O)_1.5] · 0.5H₂O (4) (H₃pbc = 3-phosphono-benzoic acid) were successfully synthesized by the hydrothermal/solvothermal reaction of metal acetate and 3-phosphono-benzoic acid. Compounds 1-4 were pH-dependent products and characterized by elemental analysis, Fourier transform infrared (FT-IR) spectra and single-crystal X-ray diffraction studies. Compound 1 is a two-dimensional (2D) structure constructed by inorganic layer and organic pendant. With the increase of pH value, structure 2 shows 3D inorganic framework with distributing organic moieties in the channels. In 3, the Cd₂O₁₀ dimers are linked by alternating terminal and bridging ligands, resulting in 1D chain structure. Compound 4 is a 2D structure where the 1D inorganic chains are connected by the organic moieties of the ligands.     

A five-coordinate copper complex with superoxide dismutase mimetic activity fromStreptomyces antibioticus

Summary A Cu(II) complex of desferrithiocin fromStreptomyces antibioticus was prepared and characterized. The first shell atoms, including one nitrogen and four oxygens, were arranged around the copper in a square-planar pyramide. Due to the axially Jahn-Teller-distorted Cu-O distance at 224.7 pm, a distinct Cu₂Zn₂superoxide dismutase mimetic activity was measured. The Cu-complex survived 600 M bovine serum albumin and the thermodynamic stability (pK=17.4) was not very different from that of Cu-EDTA. The electronic absorption properties, circular dichroism and electron paramagnetism were in accordance with those of the type-II copper species.     

A new porous 2D coordination polymer built by copper(II) and trimesic acid

A 2D porous material, Cu₃(tmen)₃(tma)₂(H₂O)₂ · 6.5H₂O [tmen = N,N,N′,N′-tetramethylethane-1,2-diamine; tmaH₃ = 1,3,5-benzenetricarboxylic acid/trimesic acid], has been synthesized and characterized by X-ray single crystal analysis, variable temperature magnetic measurements, IR spectra and XRPD pattern. The complex consists of 2D layers built by three crystallographically independent Cu(tmen) moieties bridged by tma anions. Of the three copper ions, Cu(1) and Cu(2) present distorted square pyramidal coordination geometry, while the third exhibits a severely distorted octahedral environment. The Cu(1)(tmen) and Cu(2)(tmen) building blocks bridged by tma anions give rise to chains with a zig-zag motif, which are cross-connected by Cu(3)(tmen)-tma polymers sharing metal ions Cu(2) through pendant tma carboxylates. The resulting 2D architecture extends in the crystallographic ab-plane. The adjacent sheets are embedded through the Cu(3)(tmen)-tma chains, leaving H₂O-filled channels. There are 6.5 lattice water molecules per formula unit, some of which are disordered. Upon heating, the lattice water molecules get eliminated without destroying the crystal morphology and the compound rehydrated reversibly on exposure to humid atmosphere. Magnetic data of the complex have been fitted considering isolated irregular Cu₃ triangles (three different J parameters) by applying the clumag program. The best fit indicates three close comparable J parameters and very weak antiferromagnetic interactions are operative between the metal centers.     

One-dimensional channels constructed from hydrogen bonding networks among 4,4′-bipyridine units and water molecules available for accommodation of polyoxomolybdate clusters

A hybrid coordination complex, [(H₅O₂)(H₂bpy)(bpy)₄][NaMo₈O₂₆] · 2H₂O (bpy = 4,4-bipyridine), was synthesized via hydrothermal reactions at 150 °C. The structure consists of two moieties; one is an infinite chain of β-[Mo₈O₂₆] clusters, each of which is inter-linked up by a sodium ion, and the other a two-dimensional network constructed from doubly protonated bpy ions and its neutral molecules, which are linked with water molecules by hydrogen bonds. The stacking of the networks provides one-dimensional tunnels suitable for Na-β-[Mo₈O₂₆] chains.     

Structure and magnetic properties of polynuclear copper(II) compounds with syn-anti carboxylato- and bromo-bridges

Synthesis, spectroscopic and magnetic properties, and X-ray crystal structures of two copper(II) polymers Cu(2-qic)Br (2-qic = quinoline-2-carboxylate) (1) and Cu(2-pic)Br (2-pic = pyridine-2-carboxylate) (2) are described. These compounds are isostructural with Cu(2-qic)Cl and Cu(2-pic)Cl, respectively, the X-ray crystal structures of which were reported recently. Both complexes are polynuclear copper(II) compounds (1D and 2D, respectively) based on syn-anti carboxylate bridges and additionally on linear monobromo- (in 1) and dibromo-bridging (in 2) motifs. The magnetic properties were investigated in the temperature range 1.8-300 K. They reveal the occurrence of strong antiferromagnetic coupling (J₁ = −102.5 cm⁻¹) through the single bromo-bridge in 1, which is much stronger than that transmitted by the single chloro-bridge (J = −57.0 cm⁻¹). Very weak ferromagnetic interaction through the syn-anti carboxylate bridge J₂ is expected as it was observed in isomorphous Cu(2-qic)Cl (J = 0.37 cm⁻¹). For 2 a weak ferromagnetic couplings through the syn-anti carboxylate (zJ′ = 1.35 cm⁻¹) and dibromo-bridges (J = 8.31 cm⁻¹) were found. The experimental results indicate that the observed ferromagnetic exchange through dibromo-bridge is weaker than that in the chloride analog (J = 15.0 cm⁻¹). The magnitude of magnetic interactions is discussed on the basis of structural data of compounds 1 and 2 and their halide analogues.     

Crystal structures of E. coli laccase CueO at different copper concentrations

CueO protein is a hypothetical bacterial laccase and a good laccase candidate for large scale industrial application. Four CueO crystal structures were determined at different copper concentrations. Low copper occupancy in apo-CueO and slow copper reconstitution process in CueO with exogenous copper were demonstrated. These observations well explain the copper dependence of CueO oxidase activity. Structural comparison between CueO and other three fungal laccase proteins indicates that Glu106 in CueO constitutes the primary counter-work for reconstitution of the trinuclear copper site. Mutation of Glu106 to a Phe enhanced CueO oxidation activity and supported this hypothesis. In addition, an extra alpha-helix from Leu351 to Gly378 covers substrate biding pocket of CueO and might compromises the electron transfer from substrate to type I copper.     

A new mixed-ligand copper pentaborate with square-like, rectangle-like and ellipse-like channels formed via hydrogen bonds

A new mixed-ligand copper pentaborate, [Cu(en)₂(C₅H₉NO)][B₅O₆(OH)₄]₂·C₅H₉NO (en is ethylenediamine) (1), with novel framework has been synthesized under mild solvothermal condition and characterized by FT-IR, elemental analyses, powder X-ray diffraction and TG-DTA. The structure consists of isolated polyborate anion [B₅O₆(OH)₄]⁻, copper complex cation [Cu(en)₂(C₅H₉NO)]⁺ and one C₅H₉NO molecule. The [B₅O₆(OH)₄]⁻ units are connected to one another through hydrogen bonds to form an interesting three-dimensional (3D) supramolecular framework with alternate square-like channels and rectangle-like channels along the c-axis as well as ellipse-like channels with 16-membered boron rings along the a-axis which are the largest channels in the pentaborate reported so far. The copper complex cation contains two kinds of ligands, en and C₅H₉NO, forming a square pyramid with an O atom as the vertex.     

A bimetallic oxide hybrid material constructed from a coordination complex polymer and molybdenum oxide subunits, [Ni(3,4′-bipyridine)2MoO4]·3H2O

The hydrothermal reaction of NiCl₂·6H₂O, MoO₃, 3,4′-bipyridine (3,4′-bpy) and H₂O in the mole ratio 1.0:1.0:2.1:1500 yields [Ni(3,4′-bpy)₂MoO₄]·3H₂O (1·3H₂O) in 80% yield. The structure of 1·3H₂O consists of a three-dimensional coordination polymer {Ni(3,4′-bpy)₂}_n²ⁿ⁺ with entrained {MoO₄}²⁻ tetrahedra and with water molecules of crystallization occupying channels within the bimetallic oxide-ligand framework. Crystal data: C₂₀H₁₆N₄O₄NiMo·3H₂O (1·3H₂O), tetragonal P4₁2₁2, a=13.1866(5) Å, c=29.458(2) Å, V=5122.3(4) ų, Z=8, D_calc=1.532 g cm⁻³.     

A copper(II) coordination polymer with alternating double EO-azido bridges and mixed EO-azido/alkoxo double bridges

A new one-dimensional (1D) copper(II) complex, [Cu₂(dpk · CH₂O)(N₃)₃]_n (dpk · CH₂OH = unimethylated diol of di-2-pyridyl ketone) (1), has been synthesized and characterized. X-ray crystal structure study reveals that 1 is composed of 1D copper(II) chain with alternating double EO-azido bridges and mixed EO-azido/alkoxo double bridges. The magnetic determination indicates that ferromagnetic interaction dominates in this new 1D S = 1/2 system.     

Crystal structures and spectroscopic behavior of monomeric, dimeric and polymeric copper(II) chloroacetate adducts with isonicotinamide, N-methylnicotinamide and N,N-diethylnicotinamide

Substituted pyridines provide structural rigidity and thus permit the metal coordination geometry to guide the direction of propagation of the hydrogen-bonded links between building blocks. In this paper we present the crystal structures and spectroscopic properties of monomeric, dimeric and polymeric copper(II) chloroacetates with isonicotinamide (INA), N-methylnicotinamide (MNA) and N,N-diethylnicotinamide (DENA). The molecular structure of [Cu(ClCH₂CO₂)₂(INA)₂]₂ (1) consists of a rather interesting dinuclear molecule with copper atoms bridged by anti, anti-O,O′ bridging oxygens of two chloroacetate anions. Each copper atom is octahedrally coordinated thus forming a CuN₂O₄ core with two nitrogens, originating from two different isonicotinamide molecules, in trans positions. This complex is one of a very few examples of this rare type of structure in which both carboxylate oxygen anions are coordinated to two copper metal ions. The crystal structure of 1 revealed an infinite 1-D linear hydrogen-bonded chain formed by discrete molecules [Cu(ClCH₂CO₂)₂(INA)₂]₂ connected by strong hydrogen bonds between two amide groups. This structure is the first example, where two pairs of amide groups are involved in hydrogen bonding connecting two molecules. The X-ray structure of the complex [Cu(CCl₃CO₂)₂(INA)₂]_n (3) revealed a tetragonal bipyramidal environment about the copper(II) atom. This structure represents the first example of copper(II) complex, where isonicotinamide acts as a bridging ligand. Strong intramolecular hydrogen bonds, N-H?O, create two eight-membered metallocycle rings which stabilizes the molecular structure. The crystal structure of 3 consists of 2-D sheets of a metal-organic framework. The coordination environment of the copper(II) atom in [Cu(CCl₃CO₂)₂(MNA)₂(H₂O)₂] · 2H₂O (6 · 2H₂O) is an elongated tetragonal bipyramid. Strong intramolecular hydrogen bond interactions involving an axial coordinated water molecule and a carboxylic oxygen atom stabilize the molecular structure. The crystal structure of [Cu₂(ClCH₂CO₂)₄(DENA)]_n (7) shows that the complex is an extended zigzag coordination chain of alternating binuclear paddle-wheel units of the bridging tetracarboxylate type Cu₂(ClCH₂CO₂)₄ and N,N-diethylnicotinamide molecules. This complex represents the first example of copper(II) carboxylates where N,N-diethylnicotinamide molecule acts as a bidentate bridging ligand connecting binuclear paddle-wheel units. The variation in DENA coordination in the polymeric chain can be described by the following formula: -[Cu₂(ClCH₂CO₂)₄]-(DENA-N,O)- [Cu₂(ClCH₂CO₂)₄]-(DENA-O,N)-. All complexes were characterized by electron paramagnetic resonance (EPR) spectroscopy and IR spectroscopy. The present study shows that the pyridine-carboxyamides are very suitable molecules that can be employed as ligands in the construction of extended arrays of transition metal-containing molecules linked via hydrogen bonds.