Different geometrical arrangements in carboxylate coordination polymers of flexible dicarboxylic acid

Dicarboxylate coordination polymers (1-5) of Mn(II), Ni(II), Cu(II), Zn(II) and Cd(II), respectively, derived from (7-carboxymethoxy-naphthalen-2-yloxy)-acetic acid (L₁H₂) are synthesized and characterized. Depending on the coordination sites around the metal centers and coordination mode of the ligand, dimensionality of these polymers varies. The dicarboxylates adopt three spatial orientations: in-plane linear coordination, out-of-plane cis coordination and out-of-plane trans coordination mode. Both the cis and trans out-of-plane coordination modes are found to exist only if the ancillary ligand pyridine is coordinated to the metal ion. When the aquoligand coordinates the in-plane linear coordination mode of L₁ predominates. The coordination polymers 4 and 5 show photoluminescence in solution. The dicarboxylate of (5-carboxymethoxy-naphthalen-1-yloxy)-acetic acid (L₂H₂) does not form coordination polymer under ambient conditions, but prefers to remain as uncoordinated anion providing hydrophobic confinement to hexa-aquometal(II) cation. Compound 3 crystallizes in P2₁ space group and it shows broadband ultra-violet fluorescence centered at 352.9 nm on focusing 632.8 nm He:Ne laser.     

One-dimensional silver(I) 5,5-diethylbarbiturato coordination polymers with N-piperidineethanol and 1,3-bis(4-piperidyl)propane: Syntheses,crystal structures,spectroscopic and thermal properties

Two new coordination polymers, [Ag₂(barb)(pipet)]_n (1) and {Na₃[Ag₂(barb)₂](pippr)·2H₂O}_n (2) (where H₂barb, pipet and Hpippr are 5,5-diethylbarbituric acid, N-piperidineethanol and 1,3-bis(4-piperidyl)propane, respectively) have been synthesized and characterized by elemental analysis, IR, thermal analysis and X-ray single-crystal diffraction techniques. Silver(I) ions in complexes 1 and 2 are bridged by barb dianions, leading to one-dimensional coordination polymers. In 1, the barb ligand acts as a tetradentate bridging ligand, while in 2 as a bidendate bridging ligand. The pipet ligand behaves as a bidentate chelating donor, whereas the pippr anion is not involved in coordination and remains as a counter-ion. The one-dimensional chains of 1 and 2 are further extended into supramolecular networks. Spectral and thermal analysis data for 1 and 2 are in agreement with the crystal structures.     

Crystal structures and properties of four coordination polymers constructed from flexible pamoic acid

Four novel coordination polymers constructed from flexible pamoic acid, namely [Co(pam)(4,4′-bipy)]_n·nH₂O (1), [Ni(pam)(4,4′-bipy)(H₂O)₂]_n·2nCH₃CN (2), [Cd(pam)(py)₂]_n·npy (3) and [Mn₂(pam)₂(py)₆(H₂O)₂]_n·2npy (4), (H₂pam = pamoic acid, 4,4′-bipy = 4,4′-bipyridine, py = pyridine), have been synthesized and characterized by elemental analysis, infrared spectra and X-ray crystallography. Complex 1 is a 2-D coordination polymer constructed from chelating bis-bidentate pam and 4,4′-bipyridine bridging ligands. Complex 2 is a 2-D coordination polymer assembled by bis-monodentate pam and 4,4′-bipyridine, where acetonitrile is filled in the rectangle channels. Both 2-D coordination polymers display undulated (4,4) grid layers as sql topology. Complex 3 displays a 1-D polymeric chain using chelating bis-bidentate pam as bridging ligand. Complex 4 exhibits an interesting bis-monodentate pam-Mn(II) 1-D polymeric chain, in which exist two-type six-coordinated manganese centers. Mn(1) is bound to four pyridine ligands, whereas Mn(2) is combined to two pyridine and two H₂O molecules. Their thermal stabilities have been investigated. Cadmium complex 3 displays strong green luminescence with emission maximum at 543 nm.     

Metal azelate coordination polymers containing a kinked dipyridyl tether: CdSO4 topology and “ligand vacancy” primitive cubic three-dimensional networks

Hydrothermal self-assembly has generated three coordination polymers incorporating the kinked hydrogen-bonding capable tethering ligand 4,4′-dipyridylamine (dpa) and the long flexible aliphatic dicarboxylate azelate dianion (⁻O₂C(CH₂)₇CO₂⁻, aze), [M(aze)(dpa)(H₂O)]_n (M = Co, 1; M = Ni, 2) and {[Cd(aze)(dpa)] · 2H₂O}_n (3). Complexes 1 and 2 possess crystallographically disordered azelate ligands, forming related three-dimensional (3-D) 4-connected “ligand vacancy” primitive cubic coordination polymer networks via the random intersection of two different types of [M(aze)(dpa)]_n idealized two-dimensional (2-D) layers. Compound 3 manifests a 3-D 6⁵8 CdSO₄ topology coordination polymer network, formed from orthogonal sets of parallel [Cd(aze)]_n double chains linked through dpa ligands. Luminescent properties for 3 and thermal properties are also discussed.     

Hydrothermal synthesis, crystal structures and fluorescence properties of three novel frameworks constructed with mixed ligands of isophthalic acid (1,3-BDC) and 2,3-di-2-pyridylquinoxaline (Dpdq): [M(1,3-BDC)(Dpdq)(H2O)m] · nH2O (M = Co, Cd or Zn)

Three novel metal-organic frameworks [M(1,3-BDC)(Dpdq)(H₂O)_m] · nH₂O, (M = Co^II (1), Cd^II (2) or Zn^II (3); m = 0, 1; n = 0, 1, 2, respectively) have been obtained from hydrothermal reactions of three different metal(II) nitrates with the same mixed ligands [isophthalic acid (1,3-BDC) and 2,3-di-2-pyridylquinoxaline (Dpdq)], and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that each pair of metal ions are bridged by various coordination modes of 1,3-BDC ligands to form left- and right-handed helical chains in 1, linear chains in 2, and double chains in 3, respectively. N-containing flexible ligand Dpdq takes a chelating coordination mode acting as terminal ligand. In the compound 1, adjacent left- and right-handed helical chains are packed through hydrogen bonds to form a two-dimensional (2-D) structure. In the compounds 2 and 3, adjacent chains are further linked by hydrogen bonds and/or π-π stacking interactions to form a three-dimensional (3-D) distorted hexagon meshes supramolecular framework for 2 and a ZnS-related three-dimensional (3-D) topology for 3, respectively. The different structures of compounds 1-3 illustrate that the influence of the metal ions in the self-assembly of polymeric coordination architectures. In addition, compounds 2 and 3 exhibit blue emission in the solid state at room temperature.     

pH- and mol-ratio dependent formation of zinc(II) coordination polymers with iminodiacetic acid: Synthesis, spectroscopic, crystal structure and thermal studies

Three novel zinc coordination polymers (NH₄)_n[Zn(Hida)Cl₂]_n (1), [Zn(ida)(H₂O)₂]_n (2), [Zn(Hida)₂]_n·4nH₂O (3) (H₂ida=iminodiacetic acid) and a monomeric complex [Zn(ida)(phen)(H₂O)]·2H₂O (4) (phen=1,10-phenanthroline) have been synthesized and characterized by X-ray diffraction methods. 1 and 2 form one-dimensional (1-D) chain structures, whereas 3 exhibits a three-dimensional (3-D) diamondoid framework with an open channel. The mononuclear complex 4 is extended into a 3-D supramolecular architecture through hydrogen bonds and π-π stacking. Interestingly, cyclic nonplanar tetrameric water clusters are observed that encapsulated in the 3-D lattice of 4. Based on ¹H and ¹³C NMR observations, there is obvious coordination of complex 2 in solution, while 1 and 3 decompose into free iminodiacetate ligand. Monomer [Zn(ida)(H₂O)₃] (5) is considered as a possible discrete species from 2. These coordination polymers can serve as good molecular precursors for zinc oxide.     

Synthesis and crystal structure of a novel Zn(II) 2-D coordination polymer containing 1,3-bis(4-pyridyl)propane ligand and Croconate Violet dianion

From the reaction between Zn(NO₃)₂ · 6H₂O and tetrabutylammonium croconate violet ((NBu₄)₂CV) in the presence of the flexible ligand 1,3-bis(4-pyridyl)propane (BPP) a novel neutral 2-D coordination polymer {[Zn(μ-BPP)(BPP)(CV)(H₂O)] · H₂O}_n (1) was obtained. Compound 1 was characterized by means of elemental analysis, thermogravimetric analysis and vibrational spectroscopy. The crystal structure of 1 reveals that each Zn(II) is coordinated by three nitrogen atoms from two different BPP ligands, two oxygen atoms from one Croconate Violet dianion and one aqua ligand, within a distorted octahedral geometry in a facial arrangement (ZnN₃O₃). One of the BPP ligands adopts a TG (trans–gauche) conformation bridging two zinc centers giving rise to a 1-D polymeric chain along the crystallographic a axis, and the other is coordinated to metal site in a monodentate fashion adopting a TT (trans–trans) conformation. Adjacent 1-D chains are extended into a 2-D coordination network of (4, 4) topology through cooperative hydrogen bonding involving N31, OW2 and OW1 atoms, in direction of the c axis. Two complementary 2-D sheets fit each other exhibiting an interdigitation phenomenon, giving rise to a bilayer supramolecular structure.     

Synthesis and characterization of two new coordination supramolecular structures from a versatile unsymmetric 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) ligand

Two new inorganic–organic coordination networks based on a versatile and unsymmetric building block 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) and inorganic Co^II and Cd^II salts have been synthesized in mixed solvent media and structurally characterized by single-crystal X-ray diffraction analysis. Crystal Hpot (1) was obtained from methanol solution. Reaction of Co(NO₃)₂ · 6H₂O with Hpot afforded a neutral two-dimensional (2-D) porous coordination polymer {[Co(pot)₂] · 6H₂O}_n (2) with a (4,4) network, which shows a 3-D supramolecular network through O–H?O weak interactions. While substituting the transition metal ions used in 2 with Cd(NO₃)₂ · 6H₂O, a neutral 2-D coordination polymer [Cd₂(pot)₄]_n (3) with a (6,3) network which further extended to a 3-D supramolecular structure through versatile hydrogen bonds C–H?X (X = O, N and S) was obtained. It is remarkable that the building block “pot” anion exhibits versatile coordination modes in complexes 2 and 3. These results indicate that the versatile nature of this rigid unsymmetric ligand, together with the coordination preferences of the metal centers, plays a critical role in construction of novel coordination polymers. The properties of gas absorption, magnetism and luminescence of 2 and 3 have been investigated and discussed in detail.     

Increasing the antibacterial activity of gallium(III) against Pseudomonas aeruginosa upon coordination to pyridine-derived thiosemicarbazones

Reaction of N(4)-phenyl-2-formylpyridine thiosemicarbazone (H2Fo4Ph), N(4)-phenyl-2-acetylpyridine thiosemicarbazone (H2Ac4Ph) and N(4)-phenyl-2-benzoylpyridine thiosemicarbazone (H2Bz4Ph) with gallium nitrate gave [Ga(H2Fo4Ph)₂](NO₃)₃ (1), [Ga(2Ac4Ph)₂]NO₃ (2) and [Ga(2Bz4Ph)₂]NO₃ (3). In all complexes coordination of the thiosemicarbazone via the N_py–N–S chelating system occurs. In 1 the thiosemicarbazone acts as a neutral ligand while in 2 and 3 the ligand is anionic. Upon slow diffusion of 2 in DMSO [Ga(2Ac4Ph)₂]NO₃·DMSO (2a) was formed. The crystal structure of 2a was determined. Upon coordination the antibacterial activity of both gallium and thiosemicarbazones against Pseudomonas aeruginosa significantly increases.     

Silver nitrate molecular species and coordination polymers with divergent supramolecular morphology constructed from hydrogen-bonding capable dipyridyl ligands

Solution phase reaction of silver nitrate with various hydrogen-bonding capable dipyridyl ligands has resulted in three 1-D coordination polymers and one discrete cationic species with diverse silver coordination spheres. [Ag(NO₃)(4,4′-dpk)]_n (1, 4,4′-dpk = 4,4′-dipyridylketone), {[Ag(4-bpmp)](NO₃) · 6H₂O} (2, 4-bpmp = bis(4-pyridylmethyl)piperazine) and {[Ag₂(NO₃)(3-bpmp)(H₂O)₂]NO₃}_n (3, 3-bpmp = bis(3-pyridylmethyl)piperazine) all display 1-D coordination polymer chain or ribbon motifs. Long-range Ag?O interactions and/or hydrogen-bonding promote the formation of different supramolecular aggregations such as a 2-D double layer slab in 1, a threefold interpenetrated 3-D diamondoid network in 2, and a 2-D single layer in 3. Compound 2 manifests “infinite” 1-D T(5)2 water molecule tapes within its incipient voids. {[Ag(2,4′-pmpp)₂](NO₃) · H₂O} (4, 2,4′-pmpp = 2-pyridyl(4′-methylpyridyl)piperazine) contains discrete cationic species connected by nitrate-mediated Ag?O interactions into a supramolecular 1-D zig-zag chain. Complexes 1 and 4 undergo weak blue–violet luminescence upon irradiation with ultraviolet light.     

Three main group metal coordination polymers bearing imidazole-based dicarboxylates: Hydro(solvo)thermal syntheses, crystal structures and properties

Three coordination polymers [Pb(HMIDC)]_n (1), [Ba(H₂MIDC)₂]_n (2) and {[Mg(HMIDC)(H₂O)₂]·H₂O}_n (3) (H₃MIDC = 2-methyl-1H-imidazole-4,5-dicarboxylic acid) have been yielded under different hydro(solvo)thermal conditions. X-ray diffraction analysis reveals that compound 1 exhibits a 3-D framework constructed by 2-D networks joined by μ₄-HMIDC²⁻ bridges. Compound 2 also presents a 3-D structure, which is generated from 2-D layers pillared by 1-D chains along the c-axis. Compound 3 is a 1-D infinite chain and forms supramolecular layers through hydrogen bonds. The thermal and solid-state photoluminescence properties of polymers 1-3 have been determined as well. The theoretical predication of the methyl substituent effect of the ligand H₃MIDC has been investigated.     

Synthesis and spectral characterization of mercury(II) complexes with the bidentate Schiff base ligand N,N′-bis(2,3-dimethoxybenzylidene)-1,2-diaminoethane: The crystal structures of [Hg((23-MeO-ba)2en)I2] and [Hg((23-MeO-ba)2en)Br2]

Three mercury(II) complexes, [Hg((23-MeO-ba)₂en)X₂] (X = I (1), Br (2) and Cl(3)), and the ligand (23-MeO-ba)₂en ((23-MeO-ba)₂en = N,N′-bis(2,3-dimethoxybenzylidene)-1,2-diaminoethane) have been synthesized and characterized by elemental analyses, FT-IR and ¹H NMR spectroscopy. The crystal and molecular structures of 1 and 2 were determined by X-ray crystallography from single-crystal data. The metal-to-ligand ratio was found to be 1:1. The mercury(II) center in 1 and 2 has a distorted tetrahedral geometry with HgN₂I₂ and HgN₂Br₂ chromophores, respectively. The Schiff base ligand (23-MeO-ba)₂en acts as a chelating ligand, coordinating via the two nitrogen atoms to the mercury(II) center, and it adopts an E,E conformation. The coordination sphere of the mercury(II) center in 1 and 2 is completed by the two I and Br atoms, respectively. In complex 1 an inter-molecular non-classical hydrogen bond of the type C-H?O was found, while in complex 2 inter- and intra-molecular non-classical hydrogen bonds of the type C-H?X (X = O and Br) were found. The ¹H NMR spectra of the complexes exhibit downfield as well as upfield shifts of the free ligand resonances, reflecting changes in the ligand’s geometry during its coordination.     

Synthesis, structures, electrochemistry and electrocatalysis of two novel copper(II) complexes constructed with aromatic polycarboxylates and dipyrido[3,2-d:2′,3′-f]quinoxaline

Two novel coordination polymers [Cu₃(1,3-BDC)₄(Dpq)₂] (1) and [Cu₂(BTC)(OH)(Dpq)₂] · H₂O (2), have been hydrothermally synthesized by self-assembly of aromatic polycarboxylate ligands 1,3-H₂BDC (1,3-H₂BDC = 1,3-benzenedicarboxylate) or H₃BTC (H₃BTC = 1,3,5-benzenetricarboxylate), chelating ligand Dpq (Dpq = dipyrido[3,2-d:2′,3′-f]quinoxaline), and copper chloride. X-ray diffraction analysis reveals that each trinuclear Cu^II cluster is bridged by two coordination modes of 1,3-BDC ligands to form one-dimensional (1-D) chain structure in complex 1. Complex 2 possesses a two-dimensional (2-D) layer network composed of dinuclear [Cu₂(OH)(Dpq)₂] unit and bridging ligand BTC. The adjacent chains for 1 or the adjacent layers for 2 are further linked by π-π stacking interactions to form the three-dimensional (3-D) supramolecular frameworks. Moreover, the electrochemical properties of the two copper(II) complexes bulk-modified carbon paste electrodes (Cu-CPEs: 1-CPE and 2-CPE) have been studied, and the results indicate that both Cu-CPEs give one-electron quasi-reversible redox waves in potential range of 600 to −400 mV due to the metal copper ion Cu(II)/Cu(I). The Cu-CPEs have good electrocatalytic activities toward the reduction of nitrite and bromate in 0.1 M pH 2 phosphates buffer solution, and have remarkable long term stability and especially good surface renewability by simple mechanical polishing in the event of surface fouling, which is important for practical application.     

Mercury(II) iodide coordination polymers generated from polyimine ligands

A series of new HgI₂ organic polymeric complexes, [Hg₂(L1)I₄]_n (1), [Hg(L2)I₂]_n (2), [Hg(L3)I₂]_n (3), [Hg₂(L4)I₄]_n (4), [Hg(L5)I₂]_n (5), [Hg(L6)I₃](HL6) (6) {L1 = 1,4-bis(2-pyridyl)-2,3-diaza-1,3-butadiene, L2 = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene, L3 = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, L4 = 2,5-bis(2-pyridyl)-3,4-diaza-2,4-hexadiene, L5 = 2,5-bis(3-pyridyl)-3,4-diaza-2,4-hexadiene and L6 = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene} was prepared from reactions of mercury(II) iodide with six organic nitrogen donor-based ligands under thermal gradient conditions using the branched tube method. All these compounds were structurally characterized by single-crystal X-ray diffraction. The HgI₂ coordination polymers obtained with the ligands L2, L3 and L5 show one-dimensional zig-zag motifs and in these compounds the HgI₂ units are connected to each other by the ligands L2, L3 and L5 through the pyridyl nitrogen atoms. The L1 and L4 ligands in the compounds 1 and 4 act as both a chelating and bridging group. In the compound 6 the ligand L6 acts as a monodentate ligand, resulting form a discrete compound. The thermal stabilities of compounds 1–6 were studied by thermal gravimetric (TG) and differential thermal analyses (DTA).     

A unique tetra-nuclear Ag-disulfoxide complex, {[Ag2(O,O-L)(μ-O-μ-(SO)-L)2(ClO4)]ClO4}2 (L=meso−1,2-bis(ethylsulfinyl)ethane) with unprecedented ligand coordination mode

The self-assembly of a flexible disulfoxide ligand, meso-1,2-bis(ethylsulfinyl)ethane (L) with AgClO₄ led to the formation of a novel tetra-nuclear complex, {[Ag₂(O,O-L)(μ-O-μ-(SO)-L)₂(ClO₄)]ClO₄}₂, in which the Ag^I ions exhibit two kinds of coordination modes: trigonal-bipyramidal and octahedral, and the ligands take bidentate (O,O) chelating and tridentate μ-O-μ-(SO) bridging-chelating coordination modes. Such a ligand coordination mode is unprecedented in the metal-complexes of disulfoxides.     

Influence of the anion on the coordination mode of an unsymmetrical N-heterocyclic ligand in Cd(II) complexes: From discrete molecule to one- and two-dimensional structures

Five new 0D–2D Cd(II) complexes, [Cd₂(Hbimt)₂I₄] (1), [Cd(bimt)(Hbimt)Br]_n (2), [Cd(Hbimt)Cl₂(H₂O)]_n (3), {[Cd(Hbimt)(SO₄)(H₂O)₂]·1.5H₂O}_n (4) and [Cd(Hbimt)(SCN)₂]_n (5) (Hbimt = 2-((benzoimidazol-yl)methyl)-1H-tetrazole) have been synthesized by the reactions of Hbimt with suitable cadmium salts. Employment of different anions can influence the coordination modes of the Hbimt ligand, and accordingly result in different structures ranging from 0D to infinite 1D and 2D networks. Complex 1 displays a dimeric structure in which two Cd(II) ions are bridged through two iodine atoms. Complex 2 was caused by deprotonation of the Hbimt ligand, resulting in a 1D helical chain. While in complexes 3 and 4, Hbimt acts as a bidentate bridging ligand which joins two Cd(II) ions, leading to 1D stair-like chains. Complex 5 exhibits a 2D network structure with infinite 1D [Cd₂(SCN)₂]_n chains. The distinct structures of 1, 2, 3, 4 and 5 reveal that the anions and the versatile coordination modes of the ligand play an important role in the structures of the complexes. In addition, the luminescent properties of complexes 1–5 have been investigated in the solid state at room temperature.     

Synthesis, structure and magnetic properties of cobalt(II) and copper(II) coordination polymers assembled by phthalate and 4-methylimidazole

New coordination polymers [M(Pht)(4-MeIm)₂(H₂O)]_n (M=Co (1), Cu (2); Pht²⁻=dianion of o-phthalic acid; 4-MeIm=4-methylimidazole) have been synthesized and characterized by IR spectroscopy, X-ray crystallography, thermogravimetric analysis and magnetic measurements. The crystal structures of 1 and 2 are isostructural and consist of [M(4-MeIm)₂(H₂O)] building units linked in infinite 1D helical chains by 1,6-bridging phthalate ions which also act as chelating ligands through two O atoms from one carboxylate group in the case of 1. In complex 1, each Co(II) atom adopts a distorted octahedral N₂O₄ geometry being coordinated by two N atoms from two 4-MeIm, three O atoms of two phthalate residues and one O atom of a water molecule, whereas the square-pyramidal N₂O₃ coordination of the Cu(II) atom in 2 includes two N atoms of N-containing ligands, two O atoms of two carboxylate groups from different Pht, and a water molecule. An additional strong O-H?O hydrogen bond between a carboxylate group of the phthalate ligand and a coordinated water molecule join the 1D helical chains to form a 2D network in both compounds. The thermal dependences of the magnetic susceptibilities of the polymeric helical Co(II) chain compound 1 were simulated within the temperature range 20-300 K as a single ion case, whereas for the Cu(II) compound 2, the simulations between 25 and 300 K, were made for a linear chain using the Bonner-Fisher approximation. Modelling the experimental data of compound 1 with MAGPACK resulted in: g=2.6, |D|=62 cm⁻¹. Calculations using the Bonner-Fisher approximation gave the following result for compound 2: g=2.18, J=-0.4 cm⁻¹.     

An investigation of the positional isomeric effect of terpyridine derivatives: Self-assembly of novel cadmium coordination architectures driven by N-donor covalence and π⋯π non-covalent interactions

Four cadmium compounds based on two pyridyl substituted terpyridine isomers, namely {[Cd₃(L1)₂(SCN)₆](THF)₂}_n (1), [Cd₂(L1)(CH₃OH)Cl₄]_n (2), [Cd₂(L2)₂(N₃)₄] (3) and [Cd₂(L2)₂(SCN)₄] (4) (L1 = 4′-(3-pyridyl)-2,2′:6′,2″-terpyridine, L2 = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine) have been synthesized and characterized by IR, elemental analyses, and luminescent spectroscopy with the purpose of investigating the influence of isomeric effect on network assembly. In compounds 1 and 2, L1 as a mono-tridentate bridging ligand links Cd^II atoms into 1D grid-like and 2D wave-like polymers. In contrast, in compounds 3 and 4, L2 as a chelating ligand forms Cd^II dimeric structures. The different coordination behaviors and the positional isomer effect were discussed under the same reaction conditions. In addition, three kind of π?π interactions in the four compounds were summarized, two of which could not be observed on tpy-based complexes.     

Weak ferromagnetism in 1D coordination polymers: Syntheses,crystal structures,spectroscopic and magnetic properties of [Cu(L)(Memal)]n (Memal = the dianion of methylmalonic acid,L = 1,10-phenanthroline, 2,2′-bipyridine)

Investigation of the CuCl₂/H₂Memal/L (H₂Memal = methylmalonic acid, L = 1,10-phenanthroline or 2,2′-bipyridine) reaction system in MeOH and various molar ratios has lead to the isolation of two one-dimensional coordination polymers presenting the [Cu(L)(Memal)] repeating unit (1, L = 1,10-phen; 2, L = 2,2′-bpy). The Memal²⁻ ligand adopts the bidentate [chelating] + unidentate coordination mode between the Cu^II ions. Magnetic susceptibility measurements on 1 and 2 indicated the existence of weak ferromagnetic intrachain interactions and X-band EPR spectra from powdered samples of 1 and 2 are consistent with the stereochemistry of the Cu^II ions and with the presence of weak exchange interactions.     

Assembly of novel phenanthroline-based cobalt(II) coordination polymers by selecting dicarboxylate ligands with different spacer length: From 1-D chain to 3-D interpenetrated framework

Three novel Co^II coordination polymers [Co(Dpq)₂(1,4-NDC)_0.5] · (1,4-HNDC) (1), [Co(Dpq)(2,6-NDC)] (2), and [Co₂(Dpq)₂(BPEA)₄(H₂O)] · H₂O (3) have been obtained from hydrothermal reaction of cobalt nitrate with the mixed ligands dipyrido[3,2-d:2′,3′-f]quinoxaline (Dpq) and three dicarboxylate ligands with different spacer length [1,4-naphthalene-dicarboxylic acid (1,4-H₂NDC), 2,6-naphthalene-dicarboxylic acid (2,6-H₂NDC) and biphenylethene-4,4′-dicarboxylic acid (BPEA)]. All these complexes are fully structurally characterized by elemental analysis, IR, and single-crystal X-ray diffraction analysis. Single-crystal X-ray analysis reveal that complex 1 is infinite one-dimensional (1-D) chains bridged by 1,4-NDC ligands, which are extended into a two-dimensional (2-D) supramolecular network by π-π interactions between the Dpq molecules. Complex 2 is a distorted three-dimensional (3-D) PtS network constructed from infinite Co-O-C rod units. Complex 3 has a 5-fold interpenetrated 3-D structure with diamondoid topology based on dinuclear [Co₂(CO₂)₂(μ₂-OH₂)N₄O₂] units and BPEA molecules. The different structures of complexes 1-3 illustrate the influence of the length of dicarboxylate ligands on the self-assembly of polymeric coordination architectures. In addition, the thermal properties of complexes 1-3 and fluorescent properties of complexes 2 and 3 have been investigated in the solid state.