Chain Coordination Polymer Research Articles

Synthesis, structure, and AP catalytic performance of two new 1D coordination polymers

Two 1D chain coordination polymers (CPs), [Co(DNDPA)(DMF)2] 1 and [Mn(DNDPA)(DMF)2] 2, were successfully synthesized (4,4′-dinitrodiphenic acid, DNDPA). Their structures were confirmed by single-crystal X-ray diffraction. Differential scanning calorimetry coupled with thermogravimetric analysis revealed that both CPs exhibit commendable thermal stability, with CP 1 and 2 decomposing at 368.9 °C and 375.5 °C, respectively. Non-isothermal kinetic studies confirmed that both CPs displayed significant catalytic activity for the decomposition of ammonium perchlorate (AP). In particular, CP 1 and 2 reduced the activation energy of AP from its intrinsic value to 100.5 kJ/mol and 127.45 kJ/mol, respectively, and its high-temperature decomposition peak to 354.3 °C and 327.7 °C, respectively. These findings underscore the potential of these CPs as effective catalysts for enhancing the combustion properties of AP.

C–H···I assisted 2D Cd(II)-coordination polymer: Remarkable photocatalytic degradation of rose bengal dye and efficient colorimetric recognition of La3+, and ClO4-

In this work, we report the effective synthesis, by use of solvothermal procedures, of a new coordination polymer, [CdI2(DPP)]n (1), where DPP stands for 1,3-Di(4-pyridyl)propane. The structural characteristics of [CdI2(DPP)]n (1) were analysed utilizing a variety of analytical techniques, including SCXRD, FT-IR, TGA, SEM-EDAX, elemental mapping analysis and powder X-ray diffraction. Our results showed the existence of a 2D supramolecular network created by hydrogen bonding interactions between C4–H4—-I2 and a 1D coordination polymeric chain. The [CdI2(DPP)]n (1) network has promising luminous sensing properties toward inorganic anions and metal cations with quenching efficiencies 96.89 % and 95.51 % for La3+ and ClO4− respectively. Moreover, [CdI2(DPP)]n (1) achieves an exceptional degradation efficiency of 97.3 % when used as a photocatalytic degradant of the potentially hazardous organic dye Rose Bengal, outperforming other dyes in this regard. Hence, this new coordination polymer holds significant promise for applications in sensing and environmental remediation.

New cosolvent-dependent electrochemical sensing behavior of a pair of isostructural ionic nickel(II) coordination polymers

A pair of isostructural ionic nickel(II) chain coordination polymers, {[Ni(bbbm)(H2O)4]·ATBIP·2DMF·2H2O}n (CP 1) and {[Ni(bbbm)(H2O)4]·ATBIP·2DMA·2H2O}n (CP 2) with the multi-functional ATBIP2- anion and flexible bbbm linker was synthesized under ambient condition [H2ATBIP = 5-amino-2,4,6-tribromoisophthalic acid, bbbm = 1,4-bis(benzimidazole-1-methyl)benzene]. Furthermore, the composite of CP 1 with carbon nanotubes (CP 1@CNTs) was constructed by adopting “one pot” synthesis strategy. With the help of the hydrogen-bonded chain, CPs 1–2 extend into a 3D supramolecular framework with 1D channels occupied by the cosolvent molecules (DMF/DMA). Remarkably, CPs 1–2/GCE demonstrate cosolvent-dependent electrochemical sensing behavior to H2O2 and Fe3+. CP 1/GCE shows more sensitive oxidation sensing to H2O2 than CP 2/GCE in 0.1 M NaOH. Meanwhile, CP 1/GCE demonstrates sensitive reduction sensing to Fe3+ in 0.1 M H2SO4, while CP 2/GCE doesn't. Both CPs 1–2/GCE have similar oxidation sensing capabilities to ascorbic acid (AA) in 0.1 M H2SO4. Moreover, CP 1@CNTs/GCE shows superior electrochemical sensing performance to CP 1/GCE. The LOD of CP 1@CNTs/GCE for sensing of H2O2, AA and Fe3+ reaches 0.1 μM, 1.7 μM and 3.4 μM, respectively. Moreover, CP 1@CNTs/GCE was used in the sensitive detection of H2O2, AA and Fe3+ in the real-world samples.

Chiral 1-D coordination polymer chains featuring 1,1′-binaphthyl

Four 1-D chain coordination polymers containing bent 1,1′-binaphthyl ligands were synthesised with NiII, CuII and AgI. The use of (R)-4,4′-(2,2′-diethoxy-[1,1′-binaphthalene]-6,6′)dipyridine as a ligand yielded isostructural 1-D looping chains with NiII and CuII, whereas the use of AgI yielded both linear and helical 1-D chains. Changing the dipyridyl coordination groups to dicarboxylates in (S)-6,6′-dicarboxyl-2,2′-diethoxy-1,1′-binaphthalene yielded a 1-D looping chain with a CuII paddlewheel motif. The AgI 1-D chain features two crystallographically distinct 1-D chain morphologies with a triple helix and linear strips. The packing arrangement of the 1-D chains differs because of the intermolecular interactions present, with the steric bulk of the ethoxy substituent on the 1,1′-binaphthyl enabling the formation of large void spaces.

Solvent control of dimensionality in titanium aryloxide coordination polymers prepared from 4,4′-bis(hydroxyphenyl)sulfide

The crystal and molecular structures of three covalent metal–organic network (CMON) materials synthesized from titanium (IV) isopropoxide and the Bisphenol-A analog 4,4′-bis(hydroxyphenyl)sulfide in three different solvents have been determined. The structures of the one-dimensional chain coordination polymer [trans-Ti(μ-O:O’-OC6H4SC6H4O)2(C5H5N)2]n (1) obtained from pyridine and the two-dimensional sheet coordination polymer {[Ti2(μ-O:O’-OC6H4SC6H4O)2(μ2O:κO’-OC6H4SC6H4O)2(C4H8O)2]∙(C4H8O)y}n (2) from tetrahydrofuran both contain octahedral titanium (IV) coordination geometries, whereas the doubly interpenetrated three-dimensional coordination network [Ti2(μ-O:O’-OC6H4SC6H4O)2(μ2O:κO′-OC6H4SC6H4O)2]n (3) synthesized from benzene contains trigonal bipyramidal titanium (IV). Each material has been characterized by single crystal and powder X-ray diffraction, elemental analysis, and by 1H NMR quench when it contains more than one organic component.

Catena-Poly[[di-aqua-bis-(1,3-di-hydro-3-oxo-isobenzo-furan-1-acetato)-copper(II)]-μ-N,N'-(ethane-1,2-di-yl)dinicotinamide

The title compound, {[Cu(C10H7O4)2(C14H14N4O2)(H2O)2]n, contains octa-hed-rally coordinated CuII ions ligated by two bis-(1,3-di-hydro-3-oxo-1-isobenzo-furan-acetate (dibf) ligands and two trans water mol-ecules, linked by N,N'-(ethane-1,2-di-yl)dinicotinamide (edn) ligands into mono-periodic coordination polymer chains. The dibf ligands exhibit a pseudo-mirror positional disorder over two positions in a 89.2 (3)/10.8 (3) ratio; the central amide groups of the edn ligands are disordered pseudo-rotationally in the same ratio. These mono-periodic chain motifs are held into supra-molecular di-periodic supra-molecular layers by means of N-H⋯O hydrogen bonding between edn amide groups and unligated dibf carboxyl-ate O atoms. In turn, the supra-molecular layers are held by crystal packing forces into the full crystal structure of the title compound.

Multi-Stimuli-Responsive Chromic Behaviors of an All-in-One Viologen-Based Cd(II) Complex.

A one-dimensional Cd(II) chain coordination polymer constructed by an electron-deficient viologen-anchored carboxylate ligand was successfully synthesized. Owing to the favorable stimuli-chromic properties of viologen, the title compound shows reversible photochromism, thermochromism, electrochromism, and naked-eye-detectable differentiable vapochromic response to different volatile amines. The chromic behaviors of it are ascribed to the formation of viologen radicals triggered by external stimuli. And the differentiated response to volatile amines is attributed to the size effect of the amines as well as the steric hindrance effect of forming α/β Cv-H···Namines interactions of the viologen unit to further affect the occurrence of electron transfer. Such an all-in-one crystalline material might have more practical applications in photoelectric, erasable inkless printing, light printing, and volatile amine detection fields.

Carbazole diester strapped calix[4]pyrrole: Synthesis, anion binding and self-assembly based on ion pair recognition

A new carbazole strapped calix[4]pyrrole 1 has been synthesized and ion binding properties was investigated using 1H NMR, isothermal titration calorimetry and single crystal X-ray diffraction analyses. Compared to the parent octamethyl calix[4]pyrrole 2, receptor 1 showed enhanced binding towards halide anions. Solid state structural analysis revealed that receptor 1 is capable of binding various halide salts showing different binding modes depending on the bound ion pairs. Interestingly, complexes of tetrabutyammonium (TBA+), tetraethylammonium (TEA+) and tetramethylammonium (TMA+) salts of chloride anion displayed three distinctly different binding geometries in the solid state. As a result, the linear supramolecular polymers seen in the crystal lattices are also dramatically different for these three chloride complexes of 1. Combination of 1H NMR and solid state studies revealed that binding of anion in one condition do not translates to another completely. Receptor 1 also found to form 1/1 complexes with CsCl, CsBr and CsI salts and 1D coordination polymer chains are stabilized in the solid state. Overall, construction of four different 1D linear chains are described for chloride anion based on ion pair recognition. In addition, the solid state structure of ion pair complex with CsI salt is unprecedented in the calix[4]pyrrole chemistry. Moreover, under solid-to-liquid extraction condition, receptor 1 is able to solubilise CsF and CsCl ion pairs in chloroform in which these salts are otherwise insoluble.

Two one-dimensional silver(I) coordination polymer modified electrodes for hydrogen evolution reaction and H2O2 recognition

Two new Ag(I) coordination polymers (CPs), namely: [Ag4(m-MOPhHIDC)2(BBM)2]n (1) {[Ag(BBM)](NO3)}n (2) (m-MOPhHIDC = m-methoxyanisaldehyde imidazole dicarboxylate, BBM = 2,2-(1,4-butanediyl)bis-1,3-benzimidazole), have been synthesized by solvothermal method and characterized. Structural analyses show that both complexes are one-dimensional chain coordination polymers, but the one-dimensional chains have different shapes, in which CP-1 is "V" shaped, and CP-2 is "wave-shaped". The electrochemical properties of composite electrodes CE-1 and CE-2 formed by mixing two coordination polymers with carbon paste electrodes were investigated respectively. Electrocatalytic hydrogen evolution characteristics of two composite electrodes were investigated by linear scanning voltammetry (LSV) in 0.5 M H2SO4 electrolyte, at 298 K the results show that when the current density reaches 10 mA cm−2, their overpotential positively shifted by 284 and 289 mV compared to CE (905 mV). And the Tafel slope of the CE-1 and CE-2 was 162 and 164 mV dec−1, respectively. The CE-1 exhibited superior electrocatalytic ability than CE-2, which may be attributed to the different coordination modes of central silver ions in the two CPs. In addition, the composite electrodes CE-1 and CE-2 also have a good identification effect on H2O2, and the detection limits of 36.7 and 6.2 μM in the linear range of 0.5-4000 μM were determined by chronoamperometry. Results show that the Ag(I) CPs can be used as effective dualfunctional electrocatalysts.

Structural studies of Schiff base ligand and its copper complexes: Solvents effect in 1-D polymeric and monomeric copper (II) complexes, computational and sensing studies

The Schiff base ligand (E)-2,4-dibromo-6-(((2-(methylthio)phenyl)imino)methyl)phenol (SL5) and their copper complexes were synthesized. The complex-1 ([Cu (SL5) (CH3COO)]n) and complex-2 ([Cu (SL5) (CH3COO) (CH3OH)]) were obtained by inducing acetic and methanol solvent by post-synthetic modification. Both ligand and metal complexes were characterized by FTIR, SEM, and EDAX analysis. In addition, the photoluminescence behaviour has also been studied. The crystal structures of both ligand and metal complexes were determined by single-crystal X-ray diffraction studies. The structure was solved by direct methods using the SHELXS program and refined by the SHELXL program. The structural changes of ligand in the formation of the metal complexes and the solvent-induced effect of acetic acid and methanol on copper complexes have been studied using crystal structure analysis. The SL5 ligand and complex-2 crystallize in the Monoclinic, P21/n space group and complex-1 crystallize in the Tetragonal, I41/a space group. Complex-1 exhibits six coordinated distorted octahedral geometry. The addition of methanol solvent to complex-1 forms complex-2 and has five coordinated square pyramidal geometry. Complex-1 forms a 1-D coordination polymer chain via Cu1–O3 and it is replaced by the O2–H2‧‧‧O4 interaction with the aid of coordinated methanol solvent in complex-2. The effect of solvents on the coordination sphere directly influences the chelating rings. Complexes-1 exhibits interesting type-II halogen‧‧‧halogen (Br‧‧‧Br) interaction, leading to the formation of tetramer synthons (X4). Halogen-halogen interactions are broken down by adding a methanol solvent, resulting in halogen-hydrogen interactions in complex-2. Crystal structure and quantum computational studies have analyzed the synergetic effect of ligand and solvents on the molecular packing of metal complexes. The Cu(OAc)2SL5 receptor selectively detects sulfide anion in aqueous acetonitrile HEPES buffer solution in the presence of other anions. Further, antibacterial activity has been carried out for MRSA bacteria, and docking studies were carried out for penicillin-binding protein to explore the effect of coordination and solvents.

From isostructural to hetero-structural one-dimensional coordination polymers adjusted by changing the ligand substituent group from pyrazine to furan

A new ligand, 4-(4-carboxyphenyl)-6-(pyrazin-2-yl)picolinic acid (H2L1), was used to construct four isostructural one-dimensional (1 D) zig-zag chain coordination polymers ([M(L1)(H2O)2]·3H2O, M = Mn (1), Co (2), Cd (3) and Zn (4)). Moreover, when changing the ligand substituent group from pyrazine ring to furan ring, another new ligand, 4-(4-carboxyphenyl)-6-(furan-2-yl)picolinic acid (H2L2), was synthesized. Based on H2L2, different structural 1 D coordination polymers, ([Mn(L2)(H2O)2] (5) and [Ni(L2)(H2O)2]·H2O (6)), have been obtained under the same solvothermal conditions as for the syntheses of isostructural 1–4. Interestingly, only through changing the ligand substituent group, the 1 D isostructural zig-zag chain (1–4) was adjusted to a 1 D molecular box chain (5) and 1 D linear chain (6), which should be ascribed to ligand substituent group effects. The various 1 D chain structures originate from the types of ligand substituent group: the substituent group with a pyrazine ring only yields isostructural coordination polymers 1–4, whereas the substituent group with a furan ring can construct different structural coordination polymers, such as a 1 D molecular box chain (5) or a 1 D linear chain (6). The photoluminescent properties of all coordination polymers were also examined.

Proton-Conductive and Electrochemical-Sensitive Sensing Behavior of a New Mn(II) Chain Coordination Polymer

In this work, a novel Mn(II) chain coordination polymer (Mn-CP), {[Mn(iip)(2bbpum)0.5(H2O)3]·2H2O}n [H2iip = 5-iodoisophthalic acid, 2bbpum = N,N′-bis(2-pyridinemethyl)oxamide] was synthesized under ambient conditions. Mn-CP further assembles into a 3D supramolecular architecture through hydrogen bonds, halogen bonds, and ππ stacking interactions. The composite Mn-CP/nafion membrane has low activation energy for proton transfer, which results in its temperature-insensitive proton conductivity. The cyclic voltammetry demonstrates that the Mn-CP electrode (Mn-CP/GCE) shows quite different redox properties in 0.1 M H2SO4 and 0.1 M PBS aqueous solutions. The Mn-CP/GCE exhibits a couple of irreversible redox peaks with an oxidation peak potential suitable for the nitrite oxidation in 0.1 M H2SO4. Quite differently, in the PBS aqueous buffer solution, the Mn-CP electrode has a couple of irreversible redox peaks. The reduction peak potential is appropriate for the H2O2 reduction. So, the Mn-CP/GCE can be used not only in the electrocatalytic oxidation of NO2– but also in the electrocatalytic reduction of H2O2. The amperometric response reveals that the Mn-CP/GCE exhibits high-selective and extremely sensitive oxidation sensing of NO2– and reduction sensing of H2O2. The exponential detection range is 0.01–20 mM for NO2– and 0.01–10.5 mM for H2O2. The linear detection range for both H2O2 and NO2– is 0.01–0.10 mM. The detection limit is 1.865 μM for NO2– and 8.57 μM for H2O2. The Mn-CP/GCE exhibits high electrochemical stability and fine reproducibility. Moreover, the strategy can be translated to a portable screen-printed electrode (SPE). The Mn-CP/SPE shows more sensitive sensing to NO2– and H2O2 than Mn-CP/GCE. Moreover, it can detect NO2– and H2O2 efficiently in the real-world samples. So, Mn-CP may be a potential dual nonenzymatic electrochemical sensory material for NO2–via oxidation sensing and H2O2via reduction sensing.

Coordination-Driven Self-Assembly of Complexes Constructed from Two Helical Ligands: Synthesis, Structures, and Selective Gas Adsorption Properties.

Two helical ligands (L1 and L2) were designed and synthesized by a Schiff base condensation reaction. Eight complexes, {[Zn(L1)I2]·H2O}n (1), [Cd2(L1)2I4(CH3OH)2] (2), [Hg2(L1)2I4] (3), [Ag(L1)NO3]n (4), [Ag2(L1)2(NO3)2DMSO]·H2O (5), {[Zn2(L2)2Cl4]·2CHCl3}n (6), {[Ag(L2)]·NO3}n (7), and {[Ag(L2)NO3]·CH3OH}n (8), were synthesized and characterized based on these two ligands. The crystal structures show that both Schiff base compounds exist as racemic ligands with equal amounts of P- and M-helicity, and the assembly of these racemic ligands with metal ions can lead to homochiral or heterochiral complexes via a chiral self-recognition or self-discrimination process. Complexes 2, 3, and 5 exist as heterochiral metallomacrocycles with a figure-eight conformation. Complexes 1, 6, and 8 exist as one-dimensional (1D) homochiral helical chain coordination polymers, while complexes 4 and 7 exist as 1D heterochiral helical chain coordination polymers. Furthermore, gas and vapor adsorption measurements show that all of the synthesized complexes exhibit good selective adsorption capacities toward methanol and ethanol vapor over N2, H2, and O2.

Syntheses and structural characterizations of the first coordination polymers assembled from the Ni(cyclam)2+ cation and the benzene-1,3,5-tri-carboxyl-ate linker.

The asymmetric unit of catena-poly[[[(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N 1,N 4,N 8,N 11)nickel(II)]-μ2-5-carb-oxy-benzene-1,3-di-carboxyl-ato-κ2 O 1:O 3] octa-hydrate], {[Ni(C9H4O6)(C10H24N4)]·8H2O} n (I), consists of a macrocyclic Ni2+ cation, a carboxyl-ate dianion and eight highly disordered water mol-ecules of crystallization. The components of the compound catena-poly[[[(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N 1,N 4,N 8,N 11)nickel(II)]-μ2-5-carb-oxy-benzene-1,3-di-carboxyl-ato-κ2 O 1:O 3] monohydrate], {[Ni(C9H4O6)(C10H24N4)]·H2O} n (II), are two crystallographically unique centrosymmetric macrocyclic dications, a carboxyl-ate dianion and one water mol-ecule of crystallization. In each compound, the metal ion is coordinated in the equatorial plane by the four secondary N atoms of the macrocyclic ligand, which adopts the most energetically stable trans-III conformation, and two mutually trans O atoms of the carboxyl-ate anions in a slightly tetra-gonally distorted trans-NiN4O2 octa-hedral geometry. The crystals of both compounds are composed of parallel coordination polymeric chains running along the [010] direction in I and the [110] and [10] directions in II. The bridging carboxyl-ate anions display different modes of coordination connected with the relative orientation of coordinated O atoms, i.e., remote in I and inter-mediate in II, thus resulting in essentially different distances between the Ni atoms in the chains [11.0657 (4) and 8.9089 (2) Å in I and II, respectively]. As a result of hydrogen-bonding inter-actions, the chains are joined together in sheets oriented parallel to the (10) and (001) planes in I and II, respectively.

Six Fluorene-Based N-Heterocyclic Carbene Silver(I) Complexes: Structural Study and Recognition for Cu2+

A series of fluorene-bridged bisazolium salts L1H2·X2-L6H2·X2 (X = Br– or PF6–) and six related N-heterocyclic carbene silver(I) complexes [(L1Ag)2](NO3)2 (1), {[L2Ag2(CH3CN)2]2}(PF6)4 (2), [(L3Ag)2(Ag2Br4)]n (3), [(L4Ag) (NO3)]n (4), [L5Ag2Br2]n (5), and [L6(AgCl)2] (6) have been synthesized and characterized. Each cationic moiety of 1 or 2 contained one 28-membered macrometallocycle formed via two silver(I) ions and two biscarbene ligands (L1 for 1 and L2 for 2). 1D coordination polymeric chains of 3–5 were formed by different monomers. The open structure of 6 was formed through one biscarbene ligand L6 and two [AgCl] units, in which two [AgCl] units pointed to opposite directions. Additionally, the recognition performance of 2 to Cu2+ was researched through fluorescence spectra, UV/vis spectra, 1H NMR titrations, HRMS, IR spectra, and the quantum chemical computations. The results showed that 2 can effectually differentiate Cu2+ from other cations.

Synthesis and magnetic properties of two cobalt-coordination polymers containing 1,10-phenanthroline and alkyl dicarboxylates ligands

The structural and magnetic properties of two novel one-dimensional coordination compounds were investigated in the solid crystalline state to support studies of their potential as multifunctional materials. The new compounds are based on Co(II) and are named {[Co4(glu)4(phen)4(H2O)2]·H2O}n(1) and {[Co2(azl)2(phen)2(H2O)2]}n(2) (glu = glutarate, azl = azelate, and phen = 1,10-phenanthroline). Compound (2) is the first crystal structure of a cobalt-based coordination polymer with the mixed ligands azl and phen. The crystal structures of the compounds were determined by single crystal X-ray diffraction; where the influence of the alkyl dicarboxylates on the formation of a 1D looped or a single chain coordination polymer was observed. The FT-IR analysis confirms the coordination modes adopted by the mixed ligands azl and phen and the thermal analysis suggests some thermal stability up to 150-200 °C. Supramolecular analysis suggests an important role of the non-conventional C(sp2)-H···O hydrogen bond patterns in the crystals. Finally, weak antiferromagnetic interactions were observed in both complexes.

Structural Diversity of Silver Fluorinated β-Diketonates: Effect of the Terminal Substituent and Solvent.

In order to demonstrate the role of the fluorination and some solvents in the structural organization of the Ag(I) coordination polymers with β-diketonate ligands (R1C(O)CαHC(O)R2)− we synthesized a series of the compounds containing tfac- (R1 = CH3, R2 = CF3) and pfpac- (R1 = CH3, R2 = C2F5) anions. Solvent-free [Ag(L)]∞ (L = tfac 1, pfpac 2) compounds and the corresponding acetonitrile and toluene adducts have been characterized by elemental analysis and/or NMR, IR and single-crystal XRD. This series includes five new coordination polymers. Compound 1 is a 3D coordination framework based on Ag–Ochelate/bridge, Ag–Cα bonds, and argentophilic interactions. An increase in the fluorinated group leads to a chain coordination polymer 2 of an unusual structural organization. These chains can be represented as a “DNA-type”, where two intertwined helices based on Ag–Ochelate and Ag–Cα bonds are connected through Ag–Obridge ones. Two structural types of chain coordination polymers, [Ag(tfac)(CH3CN)] and [Ag2(L)2(solvent)], have been revealed for the adducts. The latter structural type differs significantly from the previously studied toluene and acetonitrile adducts of fluorinated Ag(I) β-diketonates of the same stoichiometry. Thermal analysis in helium showed that both 1 and 2 decompose to metallic silver with the compound of pfpac-ligand being slightly more stable.

Positional effects of a pyridyl group in Zn(II) coordination polymers on the selective dye adsorption properties

Three 1D zig-zag chain coordination polymers {[Zn(L1)](I)2}n (CP1), {[Zn(L2)](I)2}n (CP2) and {[Zn(L3)](I)2}n (CP3) were synthesized under the self-assembly conditions, where L1 = 1,2-bis(pyridin-3-ylmethylene)hydrazine; L2 = 1,2-bis(1-(pyridin-3-yl)ethylidene)hydrazine; L3 = 1,2-bis(1-(pyridin-4-yl)ethylidene)hydrazine. The molecular structures of CP1, CP2 and CP3, were determined by single crystal X-ray diffraction studies. Ligands L1 and L2 differ from L3 in terms of position of nitrogen atom on the pyridyl group, while L1 and L2 differs from each other with respect to the presence of hydrogen or methyl group on the imine carbon. These minor structural differences in the ligands has affected the electronic environment and the chemical nature of the chains formed in these Zn(II) coordination polymers. Hirshfeld surface (HS) analysis has been performed on CP1, CP2 and CP3 in order to determine the intermolecular interactions present in the crystal lattice and it is in well agreement with the single crystal XRD analysis of the hydrogen bonding interactions. Selective dye adsorption behavior was observed for CP3, which showed considerable adsorption of Methyl Orange (MO) and sodium salt of Methyl Red (MR) whereas CP1 and CP2 do not show any adsorption properties at all. Further it was observed that adsorption by CP3 was selective only for an anionic dye - Methyl Orange (MO) and sodium salt of Methyl Red (MR) whereas cationic dyes such as Methylene Blue (MB), Malachite Green (MG), Rhodamine-B (RB) were not adsorbed by CP3. These studies showed the importance of chemical nature of the ligands in coordination polymers on the adsorption properties. Although being 1D chain without any pores, CP3 was capable of holding the dyes in between the neighboring chains due to the electronic effects resulted from the coordination of the ligand L3 with the Zn(II) center.

Assembly of Polyiodide Networks with Cu(II) Complexes of Pyridinol-Based Tetraaza Macrocycles.

Polyiodide networks are currently of great practical interest for the preparation of new electronic materials. The participation of metals in the formation of these networks is believed to improve their mechanical performance and thermal stability. Here we report the results on the construction of polyiodide networks obtained using Cu(II) complexes of a series of pyridinol-based tetraazacyclophanes as countercations. The assembly of these crystalline polyiodides takes place from aqueous solutions on the basis of similar structural elements, the [CuL]2+ and [Cu(H–1L)]+ (L = L2, L2-Me, L2-Me3) complex cations, so that the peculiarities induced by the increase of N-methylation of ligands, the structural variable of ligands, can be highlighted. First, solution equilibria involving ligands and complexes were analyzed (potentiometry, NMR, UV–vis, ITC). Then, the appropriate conditions could be selected to prepare polyiodides based on the above complex cations. Single-crystal XRD analysis showed that the coordination of pyridinol units to two metal ions is a prime feature of these ligands, leading to polymeric coordination chains of general formula {[Cu(H–1L)]}nn+ (L = L2-Me, L2-Me3). In the presence of the I–/I2 couple, the polymerization tendency stops with the formation of [(CuL)(CuH–1L)]3+ (L = L2-Me, L2-Me3) dimers which are surrounded by polyiodide networks. Moreover, coordination of the pyridinol group to two metal ions transforms the surface charge of the ring from negative to markedly positive, generating a suitable environment for the assembly of polyiodide anions, while N-methylation shifts the directional control of the assembly from H-bonds to I···I interactions. In fact, an extended concatenation of iodine atoms occurs around the complex dimeric cations, the supramolecular I···I interactions become shorter and shorter, fading into stronger forces dominated by the orbital overlap, which is promising for effective electronic materials.

Manganese(II), cobalt(II) and nickel(II) complexes constructed from a pyridyloxy-functionalized hexapodal cyclophosphazene ligand: Structural and magnetic studies

Herein, the coordination behaviour of a hexapodal building block, 2,2,4,4,6,6-hexakis((6-methylpyridin-3-yl)oxy) cyclotriphosphazene (MeHPCP), towards divalent metal ions (Mn, Co and Ni) is described. Three new coordination compounds, namely the molecular complex [Mn(MeHPCP)(Cl)2(H2O)2] (1) and the one-dimensional (1D) zig-zag chain coordination polymers {Co2(MeHPCP)(Cl)4(H2O)2](MeCN)(H2O)3}n (2) and {[Ni(MeHPCP)(Cl)2(H2O)]}n (3), were structurally characterized by FT-IR spectroscopy and single crystal X-ray diffraction analysis. Thermogravimetric analyses show that all the compounds have high thermal stability (>350 °C). The magnetic properties of 2 and 3 were analyzed by electron spin resonance (ESR) and the physical properties measurement system (PPMS) technique and these complexes exhibited paramagnetic behavior.