Synthesis and Structural Characterization of One‐Dimensional Cadmium(II) Coordination Polymers Containing Polydentate Nitrogen Ligands

The reactions of Cd(NO₃)₂·4H₂O with NH₄SCN and 2,4‐dpa (2,4‐dpa = 2,4‐dipyridineamine) in CH₃OH afforded the one‐dimensional coordination polymer [Cd(NCS)₂(2,4‐dpa)₂]_n, 1 , while reaction of Cd(NO₃)₂·4H₂O with NH₄SCN and PmPa (PmPa = 2‐(1‐piperazinyl)pyrimidine) in CH₃OH gave complex of the type [Cd(NCS)₂(PmPa)₂]_n, 2. Each of the 2,4‐dpa ligand in complex 1 is coordinated to the Cd²⁺ metal center through pyridyl nitrogen atoms to form the one‐dimensional chain structures. The distorted {CdN4S2} octahedral coordination geometry around Cd²⁺ center is completed by pairs of bidentate thiocyanato ligands. Complex 2 has the 1‐D arrangement constructed through one‐dimensional double μ(N,S) end‐to‐end bridging thiocyanato groups bridged Cd(II) chains interconnected through PmPa ligands.     

Syntheses and crystal structures of four new fpa-metal complexes through in situ ligand reaction

Four new fpa-metal complexes, [Co(fpa)₂(H₂O)₂] (1), [Cu(fpa)₂(H₂O)] (2), [Zn₂(fpa)₄(bpp)₂] _n (3), and {[Zn(bpy)(H₂O)₄]?·?2(fpa)} _n (4), have been synthesized and fully characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction, and thermogravimetric analysis (TGA), (Hfpa?=?2,2-difluoro-2-(pyridine-2-yl)acetate, bpp?=?1,3-bis(4-pyridyl)propane, bpy?=?4,4′-bipyridine). X-ray diffraction analyses reveal that 1 and 2 with 0-D structures are both extended into 3-D supramolecular networks through hydrogen bonds and π···π interactions. Complex 3 with chiral centers possesses a 1-D structure constructed by two kinds of bpp molecules and four kinds of fpa^? molecules with different conformations, with bbp and fpa^? bridging and capped ligands, respectively. In 4, bpy links [Zn(H₂O)₄]²⁺ into a 1-D polymeric cationic chain and uncoordinated fpa^? compensates the framework charge. The results of TGA reveal that fpa^? decomposes through two processes. Both 3 and 4 show strong fluorescence in the solid state at room temperature.     

Thermal,spectroscopic, X-ray powder diffraction,and structural studies on a new Cd(II) mixed-ligand coordination polymer

A new coordination polymer derived from Cd(II) with both rigid and flexible spacer ligands trans-1,2-bis(4-pyridyl)ethane (bpa) and 4,4′-bipyridine (4, 4′-bipy), {[Cd(μ-bpa)(4, 4′-bipy)₂(H₂O)₂] · (ClO₄)₂} _n has been synthesized and characterized by elemental analysis, IR-, ¹H NMR spectroscopy and studied by thermal analyses as well as X-ray crystallography. The single crystal X-ray analysis shows that the complex is a 1-D polymer as a result of bridging 1,3-di(4-pyridyl)propane (bpa). The 1-D chains are further self-assembled into a 3-D network via hydrogen bonding and π–π stacking. In this structure the perchlorates fill the voids. Thermal studies of this polymer show step to step separating of ligands and counter ion at different temperatures.     

Synthesis,crystal structures and fluorescence of cadmium(II) coordination polymers with derivatives of pyrazine-1,4-dioxide and thiocyanate as mixed-bridging ligands

Two Cd(II) coordination polymers have been synthesized with derivatives of pyrazine-1,4-dioxide and thiocyanate anion as bridging ligands and structurally determined by X-ray crystallography. Complex 1, [Cd(μ_1,3-SCN^?)₂(μ_1,6-L1)] _n (L1?=?2,5-dimethylpyrazine-1,4-dioxide), belongs to the triclinic, space group P 1 with a?=?5.7627(18)?Å, b?=?7.182(2)?Å, c?=?7.509(2)?Å, α?=?74.042(3)°, β?=?84.766(4)°, γ?=?88.162(4)°; complex 2, [Cd₂(μ_1,3-SCN^?)₄(μ₄-L2)] _n (L2?=?2,3,5,6-tetramethylpyrazine-1,4-dioxide), crystallizes in a monoclinic system with space group C2/m with a?=?10.194(4)?Å, b?=?13.491(6)?Å, c?=?8.140(3)?Å, β?=?120.372(4)°. Complex 1 shows a two-dimensional sheet structure, and in a direction the Cd(II) ions were coordinated by μ_1,3-SCN^? forming the one-dimensional chain and the L1 bridging ligand made the chains connect in the c direction leading to formation of a two-dimensional sheet on the ac plane. For 2 the one-dimensional chains in the a axis were constructed by coordination of μ_1,3-SCN^? bridging ligands with the Cd(II) ions, and in b and c directions the chains were joined by L2 bridging ligands leading to a three-dimensional structure. In 2 L2 displays a μ₄-bridging coordination mode. Both complexes exhibit strong fluorescence emission.     

Investigations on the Structure Diversity and Thermal Degradation Behavior of CdII and ZnII Thiocyanato Coordination Compounds based on 3‐Acetylpyridine as Neutral Co‐Ligand

Reaction of Cd^II and Zn^II thiocyanate with 3‐acetylpyridine leads to the formation of the new Cd^II and Zn^II coordination compounds [Cd(NCS)₂(3‐acetylpyridine)₄] ( 1A ), [Cd(NCS)₂(3‐acetylpyridine)₂]_n ( 1B ), [Cd(NCS)₂(3‐acetylpyridine)]_n ( 1C ) and [Zn(NCS)₂(3‐acetylpyridine)₂] ( 2A ). Compound 1A consists of discrete complexes, in which the metal centers are octahedrally coordinated by four terminal bonded N‐donor co‐ligands and two terminal N‐bonded thiocyanato anions. In compound 2A the metal centers are only tetrahedrally coordinated by two terminal bonded N‐donor co‐ligands and two terminal N‐bonded thiocyanato anions. In compound 1B the Cd^II cations are octahedrally coordinated by two terminal bonded N‐donor co‐ligands and four thiocyanato anions. The metal centers are linked by μ‐1, 3 bridging thiocyanato anions into chains. In compound 1C the metal cations are octahedrally coordinated by two μ‐1, 5 bridging 3‐acetyl‐pyridine ligands and four μ‐1, 3 bridging thiocyanato anions building up a three‐dimensional coordination network. Investigations on the thermal degradation behavior of all compounds using simultaneous differential thermoanalysis and thermogravimetry as well as X‐ray powder diffraction and IR spectroscopy prove that on heating compound 2A decompose without the formation of 3‐acetylpyridine‐deficient intermediates. In contrast, for compound 1A a stepwise decomposition is observed, leading to the formation of the 3‐acetylpyridine‐deficient compound [Cd(NCS)₂(3‐acetylpyridine)₂]_n ( 1B ) which decomposes on further heating     

Crystal engineering of Cd(II) metal–organic frameworks bridged by dicarboxylates and N-donor coligands

Two new metal–organic coordination polymers, {[Cd₄(bpea)₄(IP)₈]?·?6H₂O} _n (1) and {[Cd_1.5(suc)_1.5(IP)_1.5]?·?4H₂O} _n (2) (bpea?=?biphenylethene-4,4′-dicarboxylate, H₂suc?=?succinic acid and IP?=?1H-imidazo[4,5-f][1,10]-phenanthroline), have been obtained through two types of dicarboxylate linkers. Complex 1 contains a neutral 2-D puckered sheet that is interdigitated by neutral 1-D zigzag chains. Compound 2 shows a 2-D (4,4) net, which is extended into a 3-D supramolecular framework by weak aromatic interactions. The different structures demonstrate the effect of the dicarboxylate ligands on the formation of such coordination architectures. The fluorescence property of the two complexes was also investigated.     

Design and syntheses of two threefold interpenetrating 2-D networks

Two new interpenetrating networks, [Ni(2,2′-bpy)(5-npa)(bpe)_0.5(H₂O)] _n (1) and [Ni(2,2′-bpy)(5-npa)(bpa)_0.5(H₂O)] _n (2) (2,2′-bpy?=?2,2′-bipyridine, 5-npa?=?5-nitroisophthalato, bpe?=?1,2-bis(4-pyridyl)ethylene, bpa?=?1,2-bis(4-pyridyl)ethane), have been synthesized and characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses, X-ray powder diffraction, and single-crystal X-ray diffraction. Complexes 1 and 2 have similar structures and show a threefold interpenetrating topology constructed by three 2-D wave-like networks. Secondary building unit (SBU), [Ni(2,2′-bpy)(5-npa)(H₂O)] _n , was used as starting material of the multistep reaction. Replacing one coordination bond of chelating carboxyl group of SBUs by bpe and bpa afford the two threefold interpenetrating complexes.     

Hydrothermal synthesis and structural characterization of two unprecedented photoluminescent coordination polymers constructed from Cd salt and mixed ligand

Two new Cd-containing coordination polymers {Cd₂(succ)₂(1,10′-phen)₂} _n (1) and {Cd(glut)(1,10′-phen)(H₂O)} _n (2) are described. Complex 1 exhibits an interesting 2-D structure in which the binuclear Cd centers are linked by succinate anions. Complex 2 possesses an interesting 1-D chain-like structure. The IR and TG properties of the two compounds are studied. Furthermore, these two complexes exhibit photoluminescence.     

Synthesis and characterization of polymeric Ni(II) complexes of 4-(4-aminobenzyl)benzenamine (abba) and 4-(4-aminophenylthio)benzenamine (aptba) with thiocyanate

Two one-dimensional complexes, [Ni(SCN)₂(abba)₂] _n (abba?=?4-(4-aminobenzyl)benzenamine) (1) and [Ni(SCN)₂(aptba)₂] _n (aptba?=?4-(4-aminophenylthio)benzenamine) (2), were synthesized and characterized by EA, IR, X-ray crystallography and thermal analysis. The single crystal X-ray structural analyses of 1 and 2 show the complexes to be 1D chain polymers as a result of dibenzenamine (dba) bridging. Each Ni is six-coordinate and adopts a slightly distorted octahedral geometry with four N atoms from four dba ligands and two N atoms from two NCS-groups. Adjacent Ni atoms and two dba ligands form a 24-membered macrocycle. Thermogravimetric analysis and differential thermogravimetric analysis of 2 show that the thermal decomposition of 2 includes four transitions.     

Fine tuning of the Cd(II)–bis(benzimidazole) networks by changing carboxylate anions

Three new polymeric frameworks, [Cd(bbbi)(ita)(H₂O)]?·?H₂O (1), [Cd(bbbi)(fma)] (2), and [Cd(bbbi)(fma)(H₂O)]?·?2H₂O (3) (bbbi?=?1,1-(1,4-butanediyl)bis-1?H-benzimidazole, H₂ita?=?itaconic acid, and H₂fma?=?fumaric acid), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complex 1 is a 2-D (4,4) network containing infinite 1-D zigzag Cd(II)-bbbi chains linked by auxiliary ita ligands. In the structure of 2, infinite 1-D linear Cd(II)-bbbi chains are linked by fma ligands to generate an undulated 2-D (4,4) network. In 3, an in situ ligand transformation occurred with malate converted to H₂fma by dehydration. Thus, a 2-D (4,4) grid network constructed from bbbi and fma was obtained. The carboxylates with different substituents play an important role in the formation of the final frameworks and coordination modes of Cd(II). Thermal stability and luminescent properties of 1–3 were investigated.     

Syntheses,crystal structures,and fluorescent properties of two Cd(II) complexes based on 2,2′-(ethane-1,2-diyl)bis(1H-imidazole-4,5-dicarboxylic acid)

Two new complexes, [Cd₂(H₄ebidc)₂(CH₃OH)₄]?·?2CH₃OH (1) and {[Cd(Cl)(I)(H₆ebidc)_1/2]?·?1/2bbe?·?H₂O} _n (2) (H₆ebidc?=?2,2′-(ethane-1,2-diyl)bis(1H-imidazole-4,5-dicarboxylic acid), bbe?=?1,2-bis(2-benzimidazolyl)ethane), are obtained through self-assembly of H₆ebidc with Cd(II). Single-crystal X-ray diffraction shows that 1 has a binuclear structure and each tridentate chelating ligand coordinates to two Cd(II) ions with µ₂-O. Complex 2 displays a 1-D chain structure and each tetradentate ligand bridges two Cd(II) ions in chelating fashion. Fluorescent properties have also been determined.     

Supramolecular structures of metal complexes containing barbiturate and 1,2-bis(4-pyridyl)-ethane

This work describes the synthesis, thermal, spectroscopic properties (Raman and infrared), and crystal structures of five new supramolecular compounds [Mn(bpa)(H₂O)₄]B₂?·?4H₂O (1), [Fe(bpa)(H₂O)₄]B₂?·?4H₂O (2), [Co(bpa)(H₂O)₄]B₂?·?4H₂O (3), [Zn(bpa)(H₂O)₄]B₂?·?4H₂O (4), and Co₂mal₂bpa?·?2H₂O (5), where B is the anion of barbituric acid, bpa is 1,2-bis(4-pyridyl)-ethane, and mal is malonate ion. Compounds 1–4 are isostructural, showing covalent linear 1-D [M(bpa)(H₂O)₄]²⁺ chains, which interact by hydrogen-bonding and π-stacking interactions with barbiturate and crystallization water molecules resulting in a 3-D arrangement, belonging to Pbcn space group. Compound 5 has been obtained from the opening of the barbituric acid ring, with the formation of malonate, coordinated simultaneously to three cobalts in a 1-D chain along the c-axis, whereas bpa ligand gives rise to another 1-D chain along the a- and b-axes, resulting in a 3-D coordination polymer containing cavities. The vibrational spectra of 1–4 are also very similar; Raman spectra display two intense bands related to bpa at 1616 and 1020?cm^?1, assigned to the (ν _CC/ν _CN) and ring stretching modes, respectively. The barbiturate is also confirmed by a band at 684?cm^?1; the interesting point to be emphasized is this vibrational mode is not observed for 5, corroborating the absence of this building block in the structure.     

Solvothermal synthesis,structure, and luminescence of a 3-D Cd(II) complex assembled with biphenyl-2,5,2′,5′-tetracarboxylic acid involving in situ ligand reaction

A 3-D metal-organic framework [Cd₃(L)₂(DMF)₂]?·?2H₂O?·?2DMF (1) (H₃L?=?2-(dimethylcarbamoyl)biphenyl-5,2′,5′-tricarboxylic acid, DMF?=?N,N-dimethylformamide) with trinuclear Cd(II) units has been prepared. Complex 1 is a (3,?6)-connected (4²?·?6)₂(4⁴?·?6²?·?8⁸?·?10) coordination net, which results from the solvothermal in situ formation of a new asymmetric ligand, 2-(dimethylcarbamoyl)biphenyl-5,2′,5′-tricarboxylic acid (H₃L), through amidation of biphenyl-2,5,2′,5′-tetracarboxylic acid (H₄bptc). Additionally, the luminescence of 1 has been investigated.     

Three-pillared layer metal–organic frameworks assembled by imidazole-4,5-dicarboxylate and rigid bisimidazole ligands: synthesis,crystal structure,and sensing nitroaromatics

Three-pillared layer metal–organic frameworks based on 1H-imidazole-4,5-dicarboxylate and linear bis(imidazole) ligands generally formulated as {[Co₃(idc)₂(bib)₃]·8H₂O}_n (1), {[Cd(Hidc)(bib)_0.5]}_n (2) and {[Cd(Hidc)(bibp)]}_n (3), where H₃idc = 1H-imidazole-4,5-dicarboxylate, bib = 1,4-bis(1-imidazolyl)benzene and bibp = 4,4′-bis(1-imidazolyl)biphenyl, have been solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Compound 1 features a 3-D-pillared layer structure with 1-D channels, generated by honeycomb-like 2-D layer linked by bib ligands. Compound 2 consists of 2-D lumpy layers of [Cd₄(Hidc)₄], which are further connected by bridging ligands of bib to generate a pillared layer 3-D framework with 1-D channels. In 3, the 2-D corrugated honeycomb networks, structurally analogous to CFx, are pillared by bibp ligands to form a 3-D architecture with 1-D channels. Through selecting different metal ions and the length of pillared ligands, the pore sizes are adjusted in the three complexes. The potential of 2 and 3 for nitro explosive sensing is investigated through luminescence quenching experiments, which show that 3 can be applied as a fluorescent sensor for nitro compounds.     

Syntheses and structural characterizations of three transition metal coordination complexes based on flexible 2,4-dichlorophenoxyacetate (2,4-DCP)

Three transition metal coordination complexes, {[Co(2,4-DCP)₂(μ ₂-H₂O)(H₂O)₂]?·?(H₂O)₂} _n (1), [Zn(2,4-DCP)(IN)] _n (2), and [Mn₂(2,4-DCP)₃(DMPY)₂(μ ₂-H₂O)(H₂O)]?·?(2,4-DCP)?·?0.2(H₂O) (3) (2,4-DCP?=?2,4-dichlorophenoxyacetate, IN?=?isonicotinate, DMPY?=?5,5′-dimethyl-2,2′-bipyridine), have been prepared under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Complex 1 displays a 1-D chain through cobalt and bridging water molecules with Co?···?Co distance of 4.028(2)?Å. Complex 2 shows a 2-D (4,4) net, which is extended into a 3-D supramolecular framework by weak hydrogen-bonding interactions. Complex 3 consists of discrete dinuclear cations, 2,4-DCP counter ions and free water molecules, which are assembled into a packing structure through π?···?π stacking of inversion-related DMPY ligands and hydrogen bonds. Magnetic susceptibility measurements show weak antiferromagnetic interactions in 1. The photoluminescence and lifetime of 2 in the solid state have also been studied.     

A (3,9)-connected cadmium 1,2,4-triazolate framework based on a trinuclear inorganic cluster

Hydrothermal reaction of 1,2,4-triazole with CdCl₂?·?2.5H₂O generated a 3-D metal-organic framework, {[Cd₃Cl₂(Trz)₄]?·?H₂O} _n (1) (Trz?=?1,2,4-triazole), which was characterized by elemental analysis, FT-IR, X-ray powder diffraction, X-ray single-crystal diffraction, TG/DTA, and photoluminescence measurements. Compound 1 crystallizes in the orthorhombic system, space group Pnma, a?=?16.906(3)?Å, b?=?8.3151(17)?Å, c?=?13.080(3)?Å, V?=?1838.6(6)?ų, Z?=?4. Cd(1) is coordinated by four nitrogen atoms and one chloride to form a distorted trigonal-bipyramidal geometry. Cd(2) is an octahedron defined by four triazole nitrogen atoms and two chlorides. Two Cd(2) and one Cd(1) are linked by μ ₃-Cl(1) to give a [Cd₃Cl] cluster, which is connected by μ ₂-Cl(2) to generate a 1-D inorganic chain. The 1-D inorganic chains are extended by μ ₃-Trz to form a 2-D hybrid layer in the b, c-plane, which is ultimately linked by residual triazole ligands to give a 3-D framework. The [Cd₃Cl] clusters and the Trz ligands can be regarded as 9- and 3-connected nodes, which lead to an unusual (3,9)-connected net with Schläfli symbol of (4²³?·?6¹³)(4³). The solid 1 exhibits high thermal stability and shows strong blue fluorescence emission at 410?nm in the solid state at ambient temperature.     

Coordination polymers of lanthanides incorporating N,N′-ethylenebis(2-hydroxy-1-naphthylideneiminato): syntheses and crystal structures

Reaction of Ln(NO₃)₃?·?6H₂O with H₂napn (H₂napn?=?N,N′-ethylenebis(2-hydroxy-1-naphthylideneiminato)) and KSCN produces seven new coordination polymers, [La(H₂napn)(SCN)(C₂H₅OH)₂(NO₃)₂] _n (1), [La(H₂napn)₂(SCN)(NO₃)₂] _n (2), and [Ln(H₂napn)_1.5(NO₃)₃] _n [Ln?=?La(3), Sm(4), Eu(5), Dy(6), Er(7)]. Crystal structure analysis reveals that H₂napn functions as a bridging ligand, forming a 1-D chain polymer (1) and 2-D open-frameworks (2–7) with lanthanides. Each metal center of 1–7 is nine-coordinate. Lanthanide contraction is observed in 3–7.     

Synthesis,structure, and thermal properties of 3-D coordination polymers constructed from asymmetrical carboxylates

Three new coordination polymers constructed from asymmetric ligands were synthesized under hydrothermal conditions and characterized with single crystal X-ray analysis, infrared, and thermal gravimetric methods. Complex 1 exhibits a 3-D network constructed from rod-shaped secondary building units. Pyrimidine-4-carboxylic acid (bpa) was used as the starting material, but under hydrothermal conditions bpa formed 2,2′-pyrimidine-4,4′-dicarboxylic acid (bpda) in situ, which further connected with Pb. 3-D two-fold interpenetration of complex 2 was obtained by the similar method as described for 1, except that Cd(NO₃)₂ · 6H₂O was used instead of Pb(NO₃)₂ · 6H₂O to react with bpa. Complex 3 shows a three-connected 3-D network. Furthermore, the photoluminescence properties of 1 and 2 were studied.     

1-D chain Cd(II) compound based on flexible phenylenediacetic ligand: synthesis,crystal structure,and fluorescent properties

A coordination polymer of Cd^II with a flexible ligand in [Cd(Hpda)₂(4,4′-bipyridyl)₂]?·?(H₂O)₂ (1) (H₂pda?=?1,2-phenylenediacetic acid) has been synthesized by hydrothermal reactions and characterized by IR, TG, fluorescent spectrum, X-ray powder diffraction, and single-crystal X-ray diffraction techniques. The results show that 1 is monoclinic, with space group P2(1)/c, a?=?1.1704(7), b?=?1.7206(1), and c?=?2.2073(1) nm, β?=?120.881(2)°. In 1, the Cd(II) ions are linked by 4,4′-bipyridyl ligands to form 1-D chain with the arms of 1,2-pda ligands. These chains are imbedded into each other to form 2-D supramolecular sheets through hydrogen bonds. Adjacent 2-D sheets are assembled to 3-D network architecture through the crystallization of water molecules. Photoluminescence properties of 1 were investigated in the solid state at room temperature. The spectrum shows intense photoluminescence at 300?nm (λ_ex?=?275?nm).     

Metallacycle-based complexes based on a flexible pyridyl–benzimidazole derivative

Three new coordination complexes, {Cd(pbmb)(NO₃)₂} _n (1), {Ag(pbmb)(NO₃)(C₃H₆O)} _n (2), and {Hg₂(pbmb)₂Cl₄} _n (3), have been synthesized under solvothermal or solution reactions based on a flexible N-heterocyclic ligand 1-((2-(pyridin-4-yl)-1H-benzoimidazol-1-yl)methyl)-1H-benzotriazole (pbmb) and structurally characterized by single-crystal X-ray diffraction, IR spectrum, and elemental analyses. Both 1 and 2 display a 1-D chain structure with metallacycle unit while 3 shows a binuclear cycle motif. The aromatic rings are directing groups for π?···?π stacking interactions. The π?···?π interactions and hydrogen bonds extend the simple chain structure and binuclear structure to 3-D supramolecular architectures. Complexes 1 and 3 exhibit strong luminescence in the solid state at room temperature whereas 2 shows fluorescence quenching.