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

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

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

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

Presynthesized and In-Situ Generated Tetrazolate Ligand in the Design of Chiral Cadmium Coordination Polymer

In contrast to the in-situ generated 5-(4-pyridyl)­tetrazolate (4-ptz) ligand, the use of presynthesized 4-ptz led to the formation of a chiral cadmium coordination polymer with a rare μ₅-bridging mode of the tetrazolate ligand. This type of tuning in the design of chiral coordination polymers is reported for the first time

Presynthesized and In-Situ Generated Tetrazolate Ligand in the Design of Chiral Cadmium Coordination Polymer

In contrast to the in-situ generated 5-(4-pyridyl)­tetrazolate (4-ptz) ligand, the use of presynthesized 4-ptz led to the formation of a chiral cadmium coordination polymer with a rare μ₅-bridging mode of the tetrazolate ligand. This type of tuning in the design of chiral coordination polymers is reported for the first time

Direct Guest Exchange Induced Single-Crystal to Single-Crystal Transformation Accompanying Irreversible Crystal Expansion in Soft Porous Coordination Polymers

Two flexible porous coordination materials, [Mn­(pybimc)₂]­·2H₂O·G (G = toluene, <b>1</b>_<b>tol</b>; THF, <b>1</b>_<b>thf</b>), where pybimc = 2-(2′-pyridyl)-benzimidazole-5-carboxylate, featuring identical one-dimensional chain structure have been characterized. Guest exchange studies have exhibited that <b>1</b>_<b>tol</b> cannot be converted to <b>1</b>_<b>thf</b> through direct replacement of guest toluene molecules by THF molecules, but, of particular interest, <b>1</b>_<b>thf</b> is actually converted to <b>1</b>_<b>tol</b> and <b>1</b>_{<b>aromatic</b>} (where aromatic = <i>o</i>-, <i>m</i>-, <i>p</i>-xylene) upon the exchange of THF to toluene and other aromatic molecules, respectively. This signifies a single-crystal to single-crystal transformation accompanied irreversible crystal expansion. In-depth analyses reveal that the nature of the weak yet sufficiently strong framework–guest C–H···π interactions, rather than the guest size, observed in this system plays a key role in guiding the adsorption of liquid-phase aromatics in the soft crystalline materials

Correlation of Mesh Size of Metal–Carboxylate Layer with Degree of Interpenetration in Pillared-Layer Frameworks

Two porous cobal–organic frameworks showing threefold interpenetration of pillared-layer structures, constructed from two-dimensional (2D) neutral metal–carboxylate layers and neutral bis-pyridyl-bis-amide pillars, were hydro­(solvo)­thermally synthesized and structurally characterized by single-crystal X-ray diffraction. Compound {[Co₂(thdc)₂(bpda)₂(DMF)]·2DMF}_<i>n</i> (<b>1</b>, thdc = 2,5-thiophenedicarboxylate; bpda = <i>N,N</i>′-bis­(4-pyridinyl)-1,4-benzenedicarboxamide) adopts a uninodal 6-connected three-dimensional (3D) framework with a {4¹²·6³}-<b>pcu</b> topology in which 2D rhomboid-like 4⁴-<b>sql</b> Co–thdc layers are pillared by bpda ligands. While compound {[Co₃(btc)₂(bpda)₃]·2DMF·9H₂O}_<i>n</i> (<b>2</b>, btc = 1,3,5-benzenetricarboxylate) is composed of a binodal (3,4)-connected 3D framework with a (6³)₂(6⁴·8·10)₃ topology that can be described in terms of two building subunitsa 2D porous honeycomb-like 6³-<b>hcb</b> Co–btc layer and a bpda pillar. An in-depth analysis showed that the mesh size of the metal–carboxylate layer, in addition to the pillar length, is highly correlated with the degree of interpenetration in the pillared-layer framework. The structural characteristics of frameworks <b>1</b> and <b>2</b> fully support this relationship

Infinite Copper(II) Coordination Architectures from a Resonative Aminotriazine-Derived Tripodal Ligand: Synthesis, Structures, and Magnetic Properties

The ligand 2,4,6-tris­(2-picolylamino)-1,3,5-triazine (<i>o</i>-H₃tpat) with essentially resonative structure and two copper­(II)-based one-dimensional coordination chain structures, [Cu₃Cl₅(<i>o</i>-H₂tpat)­(H₂O)]·MeOH·CH₂Cl₂ (<b>1</b>) and [Cu₂(<i>o</i>-H₂tpat)­(H₂O)­(MeOH)­(NO₃)₂]­(NO₃)·3MeOH (<b>2</b>), with different structural patterns have been synthesized and characterized using single crystal X-ray diffraction analysis. For <i>o</i>-H₃tpat, two crystalline forms showing different solid-state structural features are obtained from MeOH/Et₂O (form <b>I</b>) and CH₂Cl₂/Et₂O (form <b>II</b>), respectively. The <i>o</i>-H₃tpat form <b>I</b> adopts an asymmetric-configured all-amino resonative tautomer with three <i>cis–trans–trans-</i>arranged pyridyl groups, whereas the <i>o</i>-H₃tpat form <b>II</b> adopts also an identical resonative structure but where two of the three pyridyl groups are in a <i>cis</i>-manner and the third one is nearly coplanar with the central aminotriazine core. On the other hand, the designed tripodal ligand in both Cu­(II)-complexes serves as a monoanion, <i>o</i>-H₂tpat^–, which suits a propeller-configured all-imino resonative structure in <b>1</b> and a <i>syn</i>–<i>anti</i>-configured amino–imino–imino resonative structure in <b>2</b>. These observations significantly indicate that the <i>o</i>-H₃tpat ligand can self-adjust and interconvert its conformation via a possible structure transformation associated with proton-shift to adapt a change in the crystallization and self-assembly reaction systems. In the magnetic point of view, <b>1</b> is treated as repeated chains composed of infinite {Cu₆Cl₁₀} units wherein the hexanuclear unit is further decomposed to one {Cu­(II)₄Cl₆} and two magnetically isolated {Cu­(II)­Cl₂} subunits. Antiferromagnetic interactions are found for the Cu₄ subunits (<i>g</i> = 2.33, 2<i>J</i>₁ = −5.6 cm^–1, 2<i>J</i>₂ = −8.6 cm^–1, 2<i>J</i>₃ = −4.1 cm^–1, and <i>J</i>₄ held to zero). For <b>2</b>, it is considered as an infinite chain that composes of Cu₂ units antiferromagnetically coupled (<i>g</i> = 2.03, 2<i>J</i>₁ = −0.2 cm^–1). The small antiferromagnetic exchange constants in both <b>1</b> and <b>2</b> suggest that the unpaired spins do not effectively interact through the tripodal <i>o</i>-H₂tpat^– ligands

Infinite Copper(II) Coordination Architectures from a Resonative Aminotriazine-Derived Tripodal Ligand: Synthesis, Structures, and Magnetic Properties

The ligand 2,4,6-tris­(2-picolylamino)-1,3,5-triazine (<i>o</i>-H₃tpat) with essentially resonative structure and two copper­(II)-based one-dimensional coordination chain structures, [Cu₃Cl₅(<i>o</i>-H₂tpat)­(H₂O)]·MeOH·CH₂Cl₂ (<b>1</b>) and [Cu₂(<i>o</i>-H₂tpat)­(H₂O)­(MeOH)­(NO₃)₂]­(NO₃)·3MeOH (<b>2</b>), with different structural patterns have been synthesized and characterized using single crystal X-ray diffraction analysis. For <i>o</i>-H₃tpat, two crystalline forms showing different solid-state structural features are obtained from MeOH/Et₂O (form <b>I</b>) and CH₂Cl₂/Et₂O (form <b>II</b>), respectively. The <i>o</i>-H₃tpat form <b>I</b> adopts an asymmetric-configured all-amino resonative tautomer with three <i>cis–trans–trans-</i>arranged pyridyl groups, whereas the <i>o</i>-H₃tpat form <b>II</b> adopts also an identical resonative structure but where two of the three pyridyl groups are in a <i>cis</i>-manner and the third one is nearly coplanar with the central aminotriazine core. On the other hand, the designed tripodal ligand in both Cu­(II)-complexes serves as a monoanion, <i>o</i>-H₂tpat^–, which suits a propeller-configured all-imino resonative structure in <b>1</b> and a <i>syn</i>–<i>anti</i>-configured amino–imino–imino resonative structure in <b>2</b>. These observations significantly indicate that the <i>o</i>-H₃tpat ligand can self-adjust and interconvert its conformation via a possible structure transformation associated with proton-shift to adapt a change in the crystallization and self-assembly reaction systems. In the magnetic point of view, <b>1</b> is treated as repeated chains composed of infinite {Cu₆Cl₁₀} units wherein the hexanuclear unit is further decomposed to one {Cu­(II)₄Cl₆} and two magnetically isolated {Cu­(II)­Cl₂} subunits. Antiferromagnetic interactions are found for the Cu₄ subunits (<i>g</i> = 2.33, 2<i>J</i>₁ = −5.6 cm^–1, 2<i>J</i>₂ = −8.6 cm^–1, 2<i>J</i>₃ = −4.1 cm^–1, and <i>J</i>₄ held to zero). For <b>2</b>, it is considered as an infinite chain that composes of Cu₂ units antiferromagnetically coupled (<i>g</i> = 2.03, 2<i>J</i>₁ = −0.2 cm^–1). The small antiferromagnetic exchange constants in both <b>1</b> and <b>2</b> suggest that the unpaired spins do not effectively interact through the tripodal <i>o</i>-H₂tpat^– ligands