Two different anionic manganese(II) coordination polymers constructed through dicyanamide coordination bridges

In order to explore new metal coordination polymers and to search for new types of ferroelectrics among hybrid coordination polymers, two manganese dicyanamide complexes, poly[tetramethylammonium [di‐μ₃‐dicyanamido‐κ⁶N¹:N³:N⁵‐tri‐μ₂‐dicyanamido‐κ⁶N¹:N⁵‐dimanganese(II)]], {[(CH₃)₄N][Mn₂(NCNCN)₅]}_n, (I), and catena‐poly[bis(butyltriphenylphosphonium) [[(dicyanamido‐κN¹)manganese(II)]‐di‐μ₂‐dicyanamido‐κ⁴N¹:N⁵]], {[(C₄H₉)(C₆H₅)₃P]₂[Mn(NCNCN)₄]}_n, (II), were synthesized in aqueous solution. In (I), one Mn^II cation is octahedrally coordinated by six nitrile N atoms from six anionic dicyanamide (dca) ligands, while the second Mn^II cation is coordinated by four nitrile N atoms and two amide N atoms from six anionic dca ligands. Neighbouring Mn^II cations are linked together by μ‐1,5‐ and μ‐1,3,5‐bridging dca anions to form a three‐dimensional polymeric structure. The anionic framework exhibits a solvent‐accessible void of 289.8 ų, amounting to 28.0% of the total unit‐cell volume. Each of the cavities in the network is occupied by only one tetramethylammonium cation. In (II), each Mn^II cation is octahedrally coordinated by six nitrile N atoms from six dca ligands. Neighbouring Mn^II cations are linked together by double dca bridges to form a one‐dimensional polymeric chain, and C—H...N hydrogen‐bonding interactions are involved in the formation of the one‐dimensional layer structure.     

Unprecedented ferromagnetic interaction in an erbium(III)–copper(II) coordination polymer

Two 3D Ln(III)–Cu(II) coordination polymers [Er₂Cu₃(pydc)₆(H₂O)₆]_n (1) and [Tb₂Cu₃(pydc)₆(H₂O)₆]_n (2) were hydrothermally prepared from pyridine-2,4-dicarboxylic acid (H₂pydc) and characterized by single-crystal X-ray diffraction analysis. The magnetic studies show that an unexpected ferromagnetic interaction between metal centers exists in 1 while 2 behaves as an antiferromagnet.     

One‐pot concomitant preparation of two copper(II) coordination polymers with different configurations of bridging bithiophene ligands

By employing the conjugated bithiophene ligand 5,5′‐bis(1H‐imidazol‐1‐yl)‐2,2′‐bithiophene (bibp), which can exhibit trans and cis conformations, two different Cu^II coordination polymers, namely, poly[[μ‐5,5′‐bis(1H‐imidazol‐1‐yl)‐2,2′‐bithiophene‐κ²N:N′](μ₂‐4,4′‐oxydibenzoato‐κ²O:O′)copper(II)], [Cu(C₁₄H₈O₅)(C₁₄H₁₀N₄S₂)]_n or [Cu(bibp)(oba)]_n, (I), and catena‐poly[μ‐aqua‐bis[μ‐5,5′‐bis(1H‐imidazol‐1‐yl)‐2,2′‐bithiophene‐κ²N:N′]bis(μ₃‐4,4′‐oxydibenzoato)‐κ³O:O′:O′′;κ⁴O:O′,O′′:O′‐dicopper(II)], [Cu₂(C₁₄H₈O₅)₂(C₁₄H₁₀N₄S₂)(H₂O)]_n or [Cu₂(bibp)(oba)₂(H₂O)]_n, (II), have been prepared through one‐pot concomitant crystallization and characterized by single‐crystal X‐ray diffraction, IR spectroscopy, elemental analysis, powder X‐ray diffraction (PXRD) and thermogravimetric (TG) analysis. Single‐crystal X‐ray diffraction indicates that the most interesting aspect of the structure is the existence of sole trans and cis conformations of the bibp ligand in a single net of (I) and (II), respectively. Compound (I) displays a threefold interpenetrating three‐dimensional framework with a 4‐connected {6⁵.8} cds topology, whereas (II) features a one‐dimensional chain structure. In the crystal of (II), the polymeric chains are further extended through C—H…O hydrogen bonds and C—H…π interactions into a three‐dimensional supramolecular architecture. In addition, strong intramolecular O—H…O hydrogen bonds formed between the bridging water molecules and the carboxylate O atoms improve the stability of the framework of (II). Furthermore, solid‐state UV–Vis spectroscopy experiments show that compounds (I) and (II) exhibit optical band gaps which are characteristic for optical semiconductors, with values of 2.70 and 2.26 eV, respectively.     

Ligand-directed copper(І) azide coordination polymers bridged by N-donor ligands with different lengths: azide exhibits a rare μ−1, 1, 3, 3 bridging mode

A Ligand-Directed strategy has been adopted to synthesize three novel Copper(І) coordination polymers, [Cu₂(bpe)(N₃)₂] _n (1), [Cu₂(bpy)(N₃)₂] _n (2), and [Cu₄(py)(N₃)₄] _n (3), by the reactions of NaN₃ with bpe, bpy and py (bpe = 1,2-trans-(4-pyridyl)ethene, bpy = 4,4′-bipyridine, py = pyrazine) in the presence of H₃PO₃ under hydrothermal conditions, which proved that the length of ligands had subtle effects on overall network and the coordination mode of azide.     

Dinuclear copper(II) complexes with different bridging connectors

One novel triply-bridged dicopper(II) complex formulated as [Cu₂(dpa)₂(μ-Cl)(μ-OH)(μ-HCOO)]·(ClO₄) 1 and two terephthalate anions bridged 2,2′-bipyridine (2,2′-bpy) dicopper(II) complexes with formulae of [Cu₂(2,2′-bpy)₄(μ-terephthalate)]·(NO₃)₂2 and [Cu₂(2,2′-bpy)₄(μ-terephthalate)]·(terephthalate) 3, respectively, have been synthesized and characterized by infrared and electrospray mass spectra as well as X-ray single-crystal determination. In addition, thermal properties of all compounds have been studied.     

Manganese(II) coordination polymers with mixed azide and pyridylbenzoate N-oxide ligands: structures and magnetism

Two novel Mn(II) coordination polymers with azide and 4-(4-pyridyl)benzoic acid N-oxide (4,4-Hopybz) were synthesized and structurally and magnetically characterized. They are formulated as {[Mn(2)(4,4-opybz)(2)(N(3))(2)(H(2)O)(2)]·H(2)O}(n) (1) and {[Mn(4)(4,4-opybz)(5)(N(3))(H(2)O)(8)](N(3))(2)·2H(2)O}(n) (2). Compound 1 contains 2D coordination layers in which the infinite Mn(II) chains with alternating (μ-EO-N(3))(2)(μ-COO) (EO = end-on) and (μ-COO)(μ-O) bridges are interlinked by the backbones of the organic ligands. Compound 2 is a 3D metal-organic framework in which the unique linear tetranuclear clusters with (μ-EO-N(3))(μ-COO) and (μ-COO)(μ-O) bridges are cross-linked by organic backbones, and it represents a new example of the rare 8-connected self-catenated 3D net with the point symbol 4(16)·6(12). Magnetic analyses on the compounds have been performed in the classical-spin approximation, revealing that all the above-mentioned mixed bridging motifs induce weak antiferromagnetic interactions between Mn(II) ions.     

Rare configuration of tautomeric benzimidazolecarboxylate ligands in cadmium(II) and copper(II) coordination polymers

Two Cd(HBimc)-based isomers, [Cd(HBimc^N)(HBimc^T)(H₂O)]·3.5H₂O·EtOH (1a·3.5H₂O·EtOH, H₂Bimc=1H-benzimidazole-5-carboxylic acid) and [Cd(HBimc^N)(HBimc^T)(H₂O)] (1b), and two Cu(HMBimc)-based coordination polymers, [Cu(HMBimc^N)₂(H₂O)]·1/2H₂O (2·1/2H₂O, H₂MBimc=2-methyl-1H-benzimidazole-5-carboxylic acid) and [Cu(HMBimc^T)₂]·2THF·H₂O (3·2THF·H₂O), were self-assembled from Cd(ClO₄)₂·6H₂O/H₂Bimc and Cu(ClO₄)₂·6H₂O/H₂MBimc systems, respectively. Compound 1a adopts a ladder-like chain structure, comprised of a hydrogen-bond-stabilized Cd₂(HBimc^N)₂-metallocyclic stair and a 1D straight -(Cd-HBimc^T)_n- edge, whereas compound 1b exhibits a 2D (4,4)-rhombus layered structure, intercrossed by 1D -(Cd-HBimc^N)_n- chains and -(Cd-HBimc^T)_n- chains. Compound 2 shows a 1D double-stranded wave-like chain from two single-stranded wave-like -(Cu-HMBimc^N)_n- chains and compound 3 adopts a 2D (4,4)-topological layer structure, intercrossed by subunits of 1D -(Cu-HMBimc^T)_n- chains. Interestingly, a pair of tautomeric HBimc building blocks—normal (N or HBimc^N) and tautomer (T or HBimc^T)—is simultaneously included in the structures of 1a and 1b, whilst the N- and T-configured HMBimc building blocks are present as separate entities in Cu species, 2 and 3, respectively. The existence of only a tautomer (T) mode of the benzimidazolecarboxylate-based ligand in a Cu(II) network is observed for the first time.     

Syntheses and coordination chemistry of methylpyridylphosphine oxide ligands with copper(II)

The coordination properties of three heterofunctional phosphine oxide ligands, 2-methylpyridyldiphenylphosphine oxide (L1), phenylphosphino-bis-2-methylpyridine oxide (L2) and phenylphosphino-bis-2-methylpyridine N,N′,P-trioxide (L3) with Cu(II) is described. The X-ray crystal structures of the compounds display a distorted octahedral geometry, which exhibit Jahn–Teller distortions. In compounds 1 and 2, the L1 and L2 ligands react with Cu(BF₄)₂ in a 2:1 ligand to metal ratio, respectively, with the BF₄ anions interacting with the metal center. L3 reacts with Cu(BF₄)₂ in 1:1 and 2:1 ligand/metal ratios to form compounds 3 and 4, respectively. Addition of either 2,2′-bipyridine or 4,4′-bipyridine to reaction solutions containing Cu(BF₄)₂ and L3 produces a discrete molecule (5) and a polymeric structure (7), respectively. The reaction of both bipyridines in the presence of Cu(BF₄)₂ and L3 gives rise to a discrete molecule (6) characterized by two octahedral coppers interconnected by the 4,4′-bipyridine. The electrochemical and photophysical properties of all compounds were investigated by cyclic voltammetry (CV) and UV–Vis, as they exhibited no emission or excitation in fluorimetric experiments.     

Systematic investigations on magneto-structural correlations of copper(II) coordination polymers based on organic ligands with mixed carboxylic and nitrogen-based moieties

Reaction of copper(II) tetrazolate-5-carboxylate with different neutral N-donor spacer ligands under hydrothermal conditions leads to the formation of five new coordination polymers, [Cu(tzc)(pyz)(0.5)(H(2)O)(2)](n)·H(2)O (1), [Cu(tzc)(pyz)](n) (2), [Cu(tzc)(pym)(H(2)O)](n) (3), [Cu(tzc)(dpe)(0.5)(H(2)O)](n) (4) and [Cu(tzc)(azpy)(0.5)(H(2)O)](n) (5) (tzc = tetrazolate-5-carboxylate, pyz = pyrazine, pym = pyrimidine, dpe = 1,2-di(4-pyridyl)ethylene and azpy = 4,4'-azopyridine). All five structures were characterized by X-ray single-crystal measurements and bulk material can be prepared phase pure in high yields. The crystal structures of the hydrates 1, 3, 4 and 5 show dimeric [Cu(2)(N(tzc)-N(tzc))(2)] building units formed by μ(2)-N1,O1:N2 bridging tzc ligands as the characteristic structural motif. These six-membered entities in 1, 4 and 5 are connected by μ(2)-N,N' bridging N-donor ligands into 1D chains and in 3 into 2D layers. In the crystal structure of compound 2 adjacent Cu(II) cations are connected by μ(2)-N1,O1:N4,O2 bridging tzc ligands into chains, which are further connected by μ(2)-N,N' bridging pyz ligands forming 2D layers. Extensive hydrogen bonds in all compounds play an important role in the construction of their supramolecular networks. Investigations of their thermal properties reveal water release upon heating according to the formation of anhydrates before starting decomposing above 220 °C. Furthermore, the magnetic properties have been studied leading to consistent global antiferromagnetic exchange interactions with coupling constants of J = 3 ± 1 cm(-1) and long-range antiferromagnetic ordering states at lower temperatures.     

Synthesis and ferromagnetic interaction in oxamido-bridged heterodinuclear copper(II)-chromium (III) complexes

Four μ- oxamido heterodinuclear complexes, [Cu (oxae) Cr (L)₂ ] (NO₃) ₃, where oxae denotes the N, N'bis (2-aminoethyl) oxamido dianion and L represents 1,10-phenanthroline (phen); 5-nitro-1,10-phenanthroline (NO_2-phen); 5-methyl-1, 10-phenanthroline (Me-phen) and 2, 2′-bipyridine (bpy), have been synthesized and characterized by elemental analyses, magnetic moments (at room temperature) and molar conductivity measurements and spectroscopy. It is proposed that these complexes have extended oxamido-bridged structures consisting of a copper (II) ion and a chromium (III) ion, which have a square planar environment and octahedral environment, respectively. The cryomagnetic properties of the [Cu(oxae)Cr(bpy)₂(NO₃)₃(1) and [Cu(oxae)Cr(phen)₂](NO₃)₃(2) complexes have been measured over the range of 4.2–300 K. The leastsquares fit of the experimental data based on the spin Hamiltonian, ? = - 2J?₁·?₂, the exchange integrals (J) were evaluated as +36.9 cm^?1 for 1 and +35.8 cm^?1 for 2. The reds have connived that the spin coupling between the adjacent copper (II) and chromium (III) ions through oxamido-bridge in both 1 and 2 is ferromagnetic.     

Two new cadmium(II) coordination polymers with bis(benzimidazole) ligands

Two new cadmium(II) coordination polymers, {[Cd(L1)(tbta)]·H₂O} _n (1) and [Cd(L2)(tbta)] _n (2) (L1 = 1,4-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, H₂tbta = tetrabromoterephthalic acid and L2 = 1,4-bis(2-methylbenzimidazol-1-ylmethyl)benzene) are obtained under hydrothermal conditions and structurally characterized by single crystal X-ray diffraction methods, IR spectroscopy, TGA and elemental analysis. The L1 and L2 ligands differ by subtle variation of substituents at semi-rigid bis(benzimidazole) bakcbones. Complex 1 features a 3D threefold interpenetrating dia array with a 4-connected 6⁶ topology. Complex 2 displays a 2D {4⁴.6²} sql/Shubnikov tetragonal plane network. Complexes 1 and 2 possess high thermal stabilities and promising fluorescence behavior in the solid state.     

A mixed anionic lead(II) N-Oxide coordination polymer containing nitrato and benzoate ligands

The structures of two forms of a mixed anionic one-dimensional coordination polymers of lead(II) nitrate derived from benzoate and 2,2’-bipyridyl N-oxide are reported. The X-ray crystal structures show subtle differences in the two binding modes of nitrate in the coordination polymers obtained from two independent solvents. The solid state UV–Vis spectra show differences in the absorption pattern of the crystalline solids obtained from different solvents. The solid state UV–Vis spectra as well as the solution spectra are compared.     

Copper(II)-phenylmalonate complexes with the bifunctional ligands nicotinamide and isonicotinamide

The use as coligands of the nicotinamide (nia) and isonicotinamide (inia) molecules in the complex formation between copper(II) and phenylmalonate [Phmal = dianion of phenylmalonic acid] yielded the compounds of formula [Cu(inia)(Phmal)(H₂O)] (1) and [Cu(inia)(Phmal)(H₂O)]_n (2). Although single crystals of 1 of appropriate size were grown, their unresolved twinning and space group ambiguity prevented a satisfactory X-ray structure determination. The crystal structure 2 consists of corrugated layers of copper(II) ions with intralayer carboxylate-phenylmalonate bridges in the anti-syn (equatorial-apical) coordination mode. A water molecule and the isonicotinamide group are coordinated to the copper atom in trans position being located above and below each layer. The Phmal ligand adopts the bidentate/monodentate coordination mode with the bidentate coordination involving one equatorial and one apical bonds, a feature which is unprecedented for the copper(II) complexes with alkyl(aryl)substituted-malonate derivatives. Intra- and interlayer H-bonds together with intralayer π-π type interactions between the phenyl and inia aromatic groups contribute to the stabilization of the three-dimensional supramolecular structure. Magnetic susceptibility measurements of complexes 1 and 2 in the temperature range 1.9-300 K are quasi identical and they correspond to a very weak ferromagnetic interaction between the copper(II) ions [J = +0.091(2) cm⁻¹ (1) and +0.097(2) cm⁻¹ (2) through the spin Hamiltonian for an isotropic square grid of interacting spin doublets which is defined as H = −JΣ_iS_i · S_i+1]. The strong similarity in the magnetic properties of 1 and 2 allow us to conclude that although they are not isostructural species, their structures have to be very close.     

Influence of the bridging coordination of DMSO on the exchange interaction character in the binuclear copper(II) complex with the nonsymmetrical exchange fragment

The binuclear copper(II) complex [Cu₂L(CH₃COO)] (I), where L^3? is the azomethine trianion based on 3-methyl-4-formyl-1-phenylpyrazol-5-one and 1,3-diaminopropan-2-ol, and its DMSO adduct (II) in which the DMSO molecule acts as an additional bridging ligand are synthesized. The structure of complex II is determined by X-ray diffraction analysis, and the structure parameters of the coordination unit of complex I are determined by EXAFS spectroscopy. The μ²-coordination of the DMSO molecule in compound II results in a change in the sign of the exchange interaction parameter. In complex I, the antiferromagnetic exchange interaction (2J = ?169 cm^?1) occurs between the copper(II) ions. The exchange interaction of the ferromagnetic type (2J = 174 cm^?1) is observed in complex II. The quantum-chemical calculations of the magnetic exchange parameters by the density functional theory method show that the role of the DMSO molecule as a switch of the exchange interaction character is exclusively the stabilization of the “broken” conformation of the metallocycles.     

A calcium(II) coordination polymer showing two different bridging 2-carbamoyl-4-nitrobenzoate coordination modes

Aqueous reaction of CaCO₃ with 2-carbamoyl-4-nitrobenzoic acid (2-ca-4nbaH) results in the formation of a 1-D coordination polymer [Ca(H₂O)₂(2-ca-4nba)₂] (1), which crystallizes in the centrosymmetric triclinic space group P 1. The structure consists of a central Ca(II), two coordinated waters, a symmetrical bridging (µ₂-η ¹ : η ¹) 2-ca-4nba, and a tridentate bridging (µ₂-η ² : η ¹) 2-ca-4nba. The calcium in 1 is coordinated by two water molecules and five oxygens of four symmetry-related 2-ca-4nba, resulting in a distorted pentagonal bipyramidal {CaO₇} polyhedron. Pairs of {Ca(H₂O)₂} units are linked into a 1-D coordination polymer extending along the a-axis with the aid of pairs of bridging 2-ca-4nba ligands. In the infinite chain, alternating pairs of Ca(II) ions exhibit Ca ··· Ca separations of 4.124 and 4.855 Å.     

Synthesis, structures, and magnetism of copper(II) and manganese(II) coordination polymers with azide and pyridylbenzoates

Three transition-metal coordination polymers with azide and/or carboxylate bridges have been synthesized from 4-(3-pyridyl)benzoic acid (4,3-Hpybz) and 4-(4-pyridyl)benzoic acid (4,4-Hpybz) and characterized by X-ray crystallography and magnetic measurements. Compound 1, [Cu(4,3-pybz)(N(3))](n), consists of 2D coordination networks in which the uniform chains with (μ-EO-N(3))(μ-COO) double bridges are cross-linked by the 4,3-pybz ligands. Compound 2, [Cu(2)(4,4-pybz)(3)(N(3))](n)·3nH(2)O, consists of 2-fold interpenetrated 3D coordination networks with the α-Po topology, in which the six-connected dinuclear motifs with mixed (μ-EO-N(3))(μ-COO)(2) (EO = end-on) triple bridges are linked by the 4,4-pybz spacers. Compound 3, [Mn(4,4-pybz)(N(3))(H(2)O)(2)](n), contains 2D manganese(II) coordination networks in which the chains with single μ-EE-N(3) bridges (EE = end-to-end) are interlinked by the 4,4-pybz ligands, and the structure also features a 2D hydrogen-bonded network in which Mn(II) ions are linked by double triatomic bridges, (μ-EE-N(3))(O-H···N) and (O-H···O)(2). Magnetic studies indicated that the mixed azide and carboxylate bridges in 1 and 2 induce ferromagnetic coupling between Cu(II) ions and that 3 features antiferromagnetic coupling through the EE-azide bridge. In addition, compound 1 exhibits antiferromagnetic ordering below 6.2 K and behaves as a field-induced metamagnet. A magnetostructural survey indicates a general trend that the ferromagnetic coupling through the mixed bridges decreases as the Cu-N-Cu angle increases.     

Chloride-bridged Ni(II) complexes with ferromagnetic exchange interaction from thiazoline hydrazone derivative ligands

A novel ligand 2-acetyl-2-thiazoline acetylhydrazone (ATHAc) and two new chloride-bridged dimeric nickel(II) complexes containing thiazoline hydrazone derivative ligands, [{Ni(ATsc)(MeOH)}₂(μ-Cl)₂]Cl₂ (1) (ATsc = 2-acetyl-2-thiazoline semicarbazone) and [{Ni(ATHAc)(H₂O)}₂(μ-Cl)₂]Cl₂ (2), were prepared and structurally characterized by elemental analysis, single crystal X-ray diffraction, IR and UV–Vis spectroscopy. In addition, NMR spectroscopy for ATHAc and magnetic susceptibility measurements for nickel complexes were performed. The structure of nickel(II) complexes consists of dimeric molecules in which nickel ions are bridged by two chloride ligands. The coordination geometry around each nickel ion can be described as a distorted octahedron with each nickel atom coordinated to one thiazoline nitrogen atom, one imine nitrogen atom, one carbonyl oxygen atom, one oxygen atom (from a methanol molecule in 1 and from a water molecule in 2) and two bridge chloride ligands. The variable temperature magnetic susceptibility measurements of the complexes show the ferromagnetic behaviour in the solid state (J = 5.7(2) cm⁻¹ in 1; 6.6(3) cm⁻¹ in 2).     

Synthesis and characterization of zinc(II), copper(II) and cadmium(II) coordination polymers with tetrachloroterephthalate-based ligands

Three complexes, namely Zn(BDC-Cl₄)(py)₃ (1), Cu(BDC-Cl₄)(py)₃ (2) and Cd(BDC-Cl₄)(py)₃ (3) (BDC-Cl₄ = 2,3,5,6-tetrachloro-1,4-benzenedicarboxylate, py = pyridine) have been synthesized. Complexes (1) and (2) have been obtained using solvothermal methods. Both have a five-coordinate geometry with two bridging monodentate tetrachloroterephthalate ligands and three pyridine ligands coordinated to the Zn(II) or Cu(II) atom. The tetrachloroterephthalate ligands bridge the adjacent Zn(II) or Cu(II) centers, giving zigzag chains. Complex (3) has also been crystallized, each Cd(II) atom is six-coordinated to three carboxylate oxygen atoms and three pyridyl nitrogen atoms. Two types of tetrachloroterephthalate ligand, featuring monodentate and bidentate carboxylates, connect the Cd(II) centers to form zigzag chains. All three complexes have been subjected to thermogravimetric analysis.