Influence of Counteranions on the Structural Modulation of Silver–Di(3-pyridylmethyl)amine Coordination Polymers

The coordination chemistry of a flexible N-donor ligand di­(3-pyridylmethyl)­amine (dpma) with silver salts has been investigated. Six new silver coordination polymers, namely, [Ag­(dpma)­(H2O)]­(NO3) (1), [Ag­(dpma)­(CF3CO2)]­·1/2H2O (2), [Ag­(dpma)]­(CF3SO3)­·1/2H2O (3), [Ag­(dpma)]­(BF4)­·3/2H2O (4), [Ag3(dpma)2(H2O)]­(ClO4)3 (5), and [Ag­(dpma)]­(PF6) (6), have been prepared by slow diffusion reactions. All the polymeric structures of compounds 1–6 are described as topologic binodal networks in terms of Ag and dpma building blocks. Compounds 1–4 show a one-dimensional ladder-like chain structure, with both Ag and dpma as three-connected T-nodes; compound 5 is an uncommon one-dimensional metallamacrocycle-based chain structure, with Ag as two-connected I-node and dpma as three-connected T-node; compound 6 is a two-dimensional honeycomb-like layer structure, with both Ag and dpma as three-connected Y-nodes. Within the structures, the dpma ligand adopts a variety of structure conformations including gauche–trans–anti (1 and 2), trans–trans–anti (3 and 4), trans–trans–syn (3), gauche–gauche–syn (5), and trans–gauche–syn (6) conformations. For these Ag–dpma coordination polymers, the structural diversity and complexity are most likely attributed to the different coordinating nature, hydrogen-bonding propensity, and templating effect of the counteranions and solvent molecules. Solution studies suggest that compounds 1–6 would disaggregate to break down the polymeric structures and then to give multiple rapidly exchanging solution species in DMSO or acetonitrile. The thermal stabilities of compounds 1–6 are examined. In addition, the photoluminescent properties of compounds 1–6 are investigated in the solid state at room temperature

Concomitant Crystallization of Genuine Supramolecular Isomeric Rhombus Grid and Ribbon

Two genuine Co­(II) supramolecular isomers, a two-dimensional (2-D) rhombus grid <b>1</b> and a one-dimensional (1-D) ribbon <b>2</b>, that have the same metal fragment and ligand conformations, were crystallized from the same reaction bath under hydro­(solvo)­thermal conditions. The formation of supramolecular isomers in this system is dominated by the bridging orientation of InMe-4-py ligands, which is mainly influenced by reaction temperature but also weakly swayed by pH value, reaction time, and counteranion. The major rhombus grid <b>1</b> is the thermodynamically favored product, and the minor ribbon <b>2</b> is the kinetically favored product under controlled conditions, as supported by their relative abundances in functions of temperature and time. Both polymeric networks of supramolecular isomers <b>1</b> and <b>2</b> display a high thermal stability over 350 °C. Magnetic studies of <b>1</b> and <b>2</b> indicate that the Co­(II) centers in the 2-D and 1-D networks are essentially magnetically insulated. The magnetic behavior demonstrates depopulation of higher energy Kramers doublets to the ground state, which results from a spin–orbit contribution, of the high-spin Co­(II) center in <i>O</i>_h configuration upon a decrease of temperature

Reversible Single-Crystal to Single-Crystal Transformations of a Zn(II)–Salicyaldimine Coordination Polymer Accompanying Changes in Coordination Sphere and Network Dimensionality upon Dehydration and Rehydration

A fluorescent Zn­(II)–salicyaldimine coordination polymer, [Zn­(L^salpyca)­(H₂O)]_<i>n</i> (<b>1</b>; H₂L^salpyca = 4-hydroxy-3-(((pyridin-2-yl)­methylimino)­methyl)­benzoic acid), showing a one-dimensional (1D) zigzag chain structure has been hydro­(solvo)­thermally synthesized. Removal of coordination water molecules in <b>1</b> by thermal dehydration gives rise to the dehydration product [Zn­(L^salpyca)]_<i>n</i> (<b>1</b>′), which has a dizinc-based two-dimensional (2D) gridlike (4,4)-layer structure. X-ray powder diffraction (XRPD) patterns, thermogravimetric (TG) analyses, and infrared (IR) spectra all clearly indicate that the structure of <b>1</b> is quite flexible as a result of a reversible 1D–2D single-crystal to single-crystal (SCSC) transformation upon removal and rebinding of coordination water molecules, which accompanies changes in coordination sphere and network dimensionality. Additionally, Zn­(II)–salicyaldimine polymers <b>1</b> and <b>1</b>′ exhibit different solid-state photoluminescences at 458 and 480 nm, respectively. This is reasonably attributed to the close-packing effect and/or the influences of the differences on the conformation and the coordination mode of the L^salpyca ligand and the coordination geometry around the Zn­(II) center

A Thermally Stable Undulated Coordination Layer Showing a Sequentially Interweaving 2D → 3D Net as a Turn-On Sensor for Luminescence Detection of Al³⁺ in Water

A Zn coordination polymer, [Zn­(H2dhbdc)­(Cz-3,6-bpy)]n (1, H4dhbdc = 2,5-dihydroxyterephthalic acid, Cz-3,6-bpy = 3,6-bis­(pyridin-4-yl)-9H-carbazole), showing high thermal stability up to 407 °C, has been prepared under hydro­(solvo)­thermal conditions. Compound 1 has a two-dimensional (2D) undulated layer structure regarded as the topological sql grid, where the tetrahedral Zn­(II) centers act as 4-connected nodes connecting by H2dhbdc2– and Cz-3,6-bpy ligands as linkers. Interestingly, the 2D undulated layers expanding in the bc plane are sequentially interwoven with each other in an offset manner along the a-axis, resulting in a condensed polyinterweaving 2D → 3D net. Compound 1 emits weak fluorescence at 522 nm in water suspensions; the intensity can be significantly enhanced by adding Al3+ ions, with low limit of detection (LOD) of 0.62 μM and high anti-interference ability over numerous competitive metal ions except Fe3+ ions. Moreover, the detection performance of 1 toward Al3+ retains high luminescence stability and reusability, being as an excellent candidate for Al3+ detection over a long period. Spectroscopic evidence from XRPD, EDS, IR, and XPS suggest the occurrence of weak framework–analyte interactions between the H2dhbdc2– ligand units in 1 and the Al3+ ions, resulting in luminescence turn-on sensing

From 1D Helix to 0D Loop: Nitrite Anion Induced Structural Transformation Associated with Unexpected <i>N</i>‑Nitrosation of Amine Ligand

An infinite Ag­(I) coordination 4₁-helical chain, [Ag­(Hdpma)]­(NO₃)₂·H₂O (<b>1</b>), was synthesized by the self-assembly of AgNO₃ and di­(3-pyridylmethyl)­amine (dpma). Helix <b>1</b> is 5-fold interweaved and has a topological diamondoid-like net that is extended by ligand-unsupported helix-to-helix argentophilic interactions. Two identical diamondoid-like nets with opposite chiralities interpenetrate to form the whole 3D framework as a meso compound. Typical anion-exchange reactions cause a remarkable single-crystal-to-single-crystal (SCSC) structural transformation from the 1D helix <b>1</b> to the 0D molecular loop [Ag­(dpma-NO)­(NO₂)]₂ (<b>2</b>) (induced by the nitrite anion, NO₂^–) and a 1D molecular ladder [Ag­(dpma)­(H₂O)]­(NO₃) (induced by the fluoride anion, F^–). Molecular loop <b>2</b> is an <i>N</i>-nitroso compound. This work is the first to present observations of nitrite-dominated in situ <i>N</i>-nitrosation of an amine ligand which accompanies SCSC structural transformation via an anion-exchange reaction

Influence of Counteranions on the Structural Modulation of Silver–Di(3-pyridylmethyl)amine Coordination Polymers

The coordination chemistry of a flexible N-donor ligand di­(3-pyridylmethyl)­amine (dpma) with silver salts has been investigated. Six new silver coordination polymers, namely, [Ag­(dpma)­(H₂O)]­(NO₃) (<b>1</b>), [Ag­(dpma)­(CF₃CO₂)]­·1/2H₂O (<b>2</b>), [Ag­(dpma)]­(CF₃SO₃)­·1/2H₂O (<b>3</b>), [Ag­(dpma)]­(BF₄)­·3/2H₂O (<b>4</b>), [Ag₃(dpma)₂(H₂O)]­(ClO₄)₃ (<b>5</b>), and [Ag­(dpma)]­(PF₆) (<b>6</b>), have been prepared by slow diffusion reactions. All the polymeric structures of compounds <b>1</b>–<b>6</b> are described as topologic binodal networks in terms of Ag and dpma building blocks. Compounds <b>1</b>–<b>4</b> show a one-dimensional ladder-like chain structure, with both Ag and dpma as three-connected T-nodes; compound <b>5</b> is an uncommon one-dimensional metallamacrocycle-based chain structure, with Ag as two-connected I-node and dpma as three-connected T-node; compound <b>6</b> is a two-dimensional honeycomb-like layer structure, with both Ag and dpma as three-connected Y-nodes. Within the structures, the dpma ligand adopts a variety of structure conformations including gauche–trans–anti (<b>1</b> and <b>2</b>), trans–trans–anti (<b>3</b> and <b>4</b>), trans–trans–syn (<b>3</b>), gauche–gauche–syn (<b>5</b>), and trans–gauche–syn (<b>6</b>) conformations. For these Ag–dpma coordination polymers, the structural diversity and complexity are most likely attributed to the different coordinating nature, hydrogen-bonding propensity, and templating effect of the counteranions and solvent molecules. Solution studies suggest that compounds <b>1</b>–<b>6</b> would disaggregate to break down the polymeric structures and then to give multiple rapidly exchanging solution species in DMSO or acetonitrile. The thermal stabilities of compounds <b>1</b>–<b>6</b> are examined. In addition, the photoluminescent properties of compounds <b>1</b>–<b>6</b> are investigated in the solid state at room temperature

Reversible Single-Crystal to Single-Crystal Transformations of a Zn(II)–Salicyaldimine Coordination Polymer Accompanying Changes in Coordination Sphere and Network Dimensionality upon Dehydration and Rehydration

A fluorescent Zn­(II)–salicyaldimine coordination polymer, [Zn­(L^salpyca)­(H₂O)]_<i>n</i> (<b>1</b>; H₂L^salpyca = 4-hydroxy-3-(((pyridin-2-yl)­methylimino)­methyl)­benzoic acid), showing a one-dimensional (1D) zigzag chain structure has been hydro­(solvo)­thermally synthesized. Removal of coordination water molecules in <b>1</b> by thermal dehydration gives rise to the dehydration product [Zn­(L^salpyca)]_<i>n</i> (<b>1</b>′), which has a dizinc-based two-dimensional (2D) gridlike (4,4)-layer structure. X-ray powder diffraction (XRPD) patterns, thermogravimetric (TG) analyses, and infrared (IR) spectra all clearly indicate that the structure of <b>1</b> is quite flexible as a result of a reversible 1D–2D single-crystal to single-crystal (SCSC) transformation upon removal and rebinding of coordination water molecules, which accompanies changes in coordination sphere and network dimensionality. Additionally, Zn­(II)–salicyaldimine polymers <b>1</b> and <b>1</b>′ exhibit different solid-state photoluminescences at 458 and 480 nm, respectively. This is reasonably attributed to the close-packing effect and/or the influences of the differences on the conformation and the coordination mode of the L^salpyca ligand and the coordination geometry around the Zn­(II) center

Zinc(II)-Based Ring-and-Rod Coordination Layer as an Excitation-Wavelength-dependent Dual-Emissive Chemosensor for Discriminating Fe³⁺, Cr³⁺, and Al³⁺ in Water

The reactions of Zn(NO3)2, 3,6-bis(pyridin-3-yl)-9H-carbazole (bpycz), and 2,5-dihydroxyterephthalic acid (H4dhbdc) or 2-bromoterephthalic acid (Br-1,4-H2bdc) under hydro(solvo)thermal conditions yielded corresponding coordination polymers (CPs) {[Zn(H2dhbdc)(bpycz)]•0.5H2O}n (1) and [Zn(Br-1,4-bdc)(bpycz)]•2DMAc•H2O (2), respectively, with high thermal stability approaching 350 °C. CP 1 adopts a ring-and-rod layer structure, which is topologically described as a 4-connected net with the point symbol of 2•65. Two layers are interpenetrated in parallel interlocking mode to form a double 2D → 2D polyrotaxane entanglement with extra-framework void space of 19.6%. CP 2 has a non-interpenetrating ring-and-rod layer structure of 4-connected 2•65 net topology, with extra-framework void space of 16.6%. Thermally activated 1 and 2 revealed CO2 uptakes of 101.1 and 98.6 cm3 g–1, respectively, at P/P0 = 1 and 195 K. X-ray powder diffraction (XRPD) patterns confirmed that 1 and 2 both possessed high chemical stability in H2O, CH3OH, acetone, and DMF, and framework stability during gas adsorption–desorption. The H2O suspension of 1 displayed excitation-dependent dual-emissive properties, appearing at 432 nm upon excitation at 300 nm and at 528 nm upon excitation at 365 nm. Of note, 1 was capable of detection of Fe3+, Cr3+, and Al3+ ions in H2O, showing good anti-interference ability, excellent selectivity, and high sensitivity. More interesting, the dual-emissive properties make 1 to be an excellent luminescence chemosensor to screen Fe3+, Cr3+, and Al3+ from a pool of metal ions in H2O upon excitation at 300 nm via luminescence quenching effect and then discriminate Fe3+, Cr3+, and Al3+ upon excitation at 365 nm via luminescence quenching, unaltered, and enhancement responses, respectively. On the other hand, the H2O suspension of 2 demonstrated an excitation-independent emission appearing at around 430 nm, which could be utilized to sensitively detect Fe3+ and Cr3+ ions with good anti-interference ability and excellent selectivity via luminescence quenching effect. Further, 1 and 2 were recyclability and possessed cycling stability. The plausible sensing mechanisms for 1 and 2 toward Fe3+, Cr3+, and Al3+ were also explored in detail

Dissolution/Reorganization toward the Destruction/Construction of Porous Cobalt(II)− and Nickel(II)−Carboxylate Coordination Polymers

The alkali-metal-cation-induced structural transformation of porous coordination polymers (CPs), {A2[M3(btec)2(H2O)4]}n (1, A = K, M = Co; 2, A = K, M = Ni; 3, A = Cs, M = Co; and 4, A = Cs, M = Ni; btec = benzene-1,2,4,5-tetracarboxylate), occurred via a unique dissolution/reorganization process in the presence of an alkali chloride (LiCl, NaCl) in water. Treatment of 1 or 2 in an aqueous solution of LiCl resulted in the formation of new metal−carboxylate species [Co2(btec)(H2O)10]·H2O (5·H2O) and {Li2[Ni3(btec)2(H2O)10]·3.5H2O}n (6·3.5H2O), respectively. When NaCl was used in place of LiCl under similar reaction conditions, similar dissolution/reorganization processes were observed. The cobalt species 1 and 3 were converted into the metal−carboxylate product [Na2Co(btec)(H2O)8]n (7), whereas the nickel−carboxylate frameworks 2 and 4 were transformed into {[Na4Ni2(btec)2(H2O)18]·3H2O}n (8·3H2O). Single-crystal X-ray diffraction analysis revealed that 5·H2O is a discrete molecule, which extends to a hydrogen-bonded 3D porous supramolecular network including tetrameric water aggregates. Compound 6·3.5H2O adopts a 3D polymeric structure with a novel (2,4,4)-connected net on the basis of a 4-connecting organic node of a btec ligand, a square-planar 4-connecting metallic trans-Ni(O2C)4(H2O)2 node, and a 2-connecting octahedral metallic trans-Ni(O2C)2(H2O)4 hinge. Compound 7 possesses a 3D polymeric structure comprised of two types of intercrossed (4,4)-layers, a [CoII(btec)]-based layer and a [NaI(btec)]-based layer, in a nearly perpendicular orientation (ca. 87°). Compound 8·3H2O adopted a 2D sheet network by utilizing heterometallic trinuclear clusters of Na2Ni(O2C)5(H2O)9 as secondary building units. Each sheet is hydrogen-bonded to neighboring units, giving a 3D supramolecular network. It is noteworthy that the dissolution/reorganization process demonstrates the cleavage and reformation of metal−carboxylate bonds, leading to a destruction/construction structural transformation of CPs

Dissolution/Reorganization toward the Destruction/Construction of Porous Cobalt(II)− and Nickel(II)−Carboxylate Coordination Polymers

The alkali-metal-cation-induced structural transformation of porous coordination polymers (CPs), {A2[M3(btec)2(H2O)4]}n (1, A = K, M = Co; 2, A = K, M = Ni; 3, A = Cs, M = Co; and 4, A = Cs, M = Ni; btec = benzene-1,2,4,5-tetracarboxylate), occurred via a unique dissolution/reorganization process in the presence of an alkali chloride (LiCl, NaCl) in water. Treatment of 1 or 2 in an aqueous solution of LiCl resulted in the formation of new metal−carboxylate species [Co2(btec)(H2O)10]·H2O (5·H2O) and {Li2[Ni3(btec)2(H2O)10]·3.5H2O}n (6·3.5H2O), respectively. When NaCl was used in place of LiCl under similar reaction conditions, similar dissolution/reorganization processes were observed. The cobalt species 1 and 3 were converted into the metal−carboxylate product [Na2Co(btec)(H2O)8]n (7), whereas the nickel−carboxylate frameworks 2 and 4 were transformed into {[Na4Ni2(btec)2(H2O)18]·3H2O}n (8·3H2O). Single-crystal X-ray diffraction analysis revealed that 5·H2O is a discrete molecule, which extends to a hydrogen-bonded 3D porous supramolecular network including tetrameric water aggregates. Compound 6·3.5H2O adopts a 3D polymeric structure with a novel (2,4,4)-connected net on the basis of a 4-connecting organic node of a btec ligand, a square-planar 4-connecting metallic trans-Ni(O2C)4(H2O)2 node, and a 2-connecting octahedral metallic trans-Ni(O2C)2(H2O)4 hinge. Compound 7 possesses a 3D polymeric structure comprised of two types of intercrossed (4,4)-layers, a [CoII(btec)]-based layer and a [NaI(btec)]-based layer, in a nearly perpendicular orientation (ca. 87°). Compound 8·3H2O adopted a 2D sheet network by utilizing heterometallic trinuclear clusters of Na2Ni(O2C)5(H2O)9 as secondary building units. Each sheet is hydrogen-bonded to neighboring units, giving a 3D supramolecular network. It is noteworthy that the dissolution/reorganization process demonstrates the cleavage and reformation of metal−carboxylate bonds, leading to a destruction/construction structural transformation of CPs