Solvent-mediated Structural Transformation Research Articles

Inclusion of cyclodextrins in a metallosupramolecular framework via structural transformations

The inclusion of α-cyclodextrin and both α- and γ-cyclodextrins in a multilayer framework composed of d-penicillaminato AuI3CoIII2 complex anions and aqua sodium(i) cations via solvent-mediated structural transformations are reported.

Sequential structural transformations via pseudohalide-anion exchange reactions in Cu(II) supramolecular complexes

We report here the first example of sequential post-synthetic structural transformations via pseudohalide anion exchanges. Assembly of a rigid angular ligand 3-phenyl-5-(2-pyridyl)-4-(4-pyridyl)-4H-1,2,4-triazole (L240) with CuBr2 results in a 1D crystalline material {[Cu(L240)(Br)2](DMF)(H2O)}n (1). Immersing the green microcrystalline sample of 1 into an aqua solution of NaN(CN)2 (Na(dca)), the partly exchanged blue species {[Cu(L240)(dca)Br](H2O)}n (2) is obtained after ca. a week. Then, the fully exchanged green [Cu(L240)(dca)2]n (3) occurs after about ten days and 2 gradually disappears. Further immersing 1 or 3 into the solution of NaN3, a new deep green material defined as [Cu(L240)(N3)2]2 (4) can be obtained. These structural transformations can be ascribed to the solvent-mediated structural transformation, accompanied the change of crystallinity, shape, size, and color. Notably, 2–4 cannot be synthesized by direct assembly of L240 and Cu salts with those pseudohalide (dca– or N3–).

Solvent-mediated structural transformations of copper(II) coordination polymers induced by different short-chain alcohols.

A three-dimensional copper(II) coordination polymer (CP), {Cu(L-F)(N3)}n (1), was synthesized by reacting Cu(NO3)2 with 5-fluoronicotinic acid (HL-F) and NaN3 in a water medium. Complex (1) shows a 3D network, in which the 1D [Cu2(COO)N3]n chains are interconnected via L-F ligands. By immersing (1) into different short-chain alcohols (CH3OH, C2H5OH and HOC2H4OH), three different CPs were isolated, including {Cu3(L-F)4(N3)2(CH3OH)2}n (2), {Cu3(L-F)4(N3)2(C2H5OH)2}n (3) and {Cu2.5(L-F)3(N3)2(HOC2H4OH)0.5}n (4). CPs (2) and (3) display a similar structure, in which trinuclear subunit [Cu3(COO)2(N3)2(solvent)2] is generated. Furthermore, such entities are interconnected via L-F ligands to give rise to a 3D network. As for (4), there are trinuclear [Cu3(COO)2(N3)2] and binuclear [Cu2(COO)N3] units, which are interconnected by L-F ligands to generate a 3D network. Notably, in (2) and (3), the coordination modes of CH3OH and C2H5OH solvents are monodentate; whereas for (4), the HOC2H4OH solvent adopts a bridging mode to link two Cu atoms. Of further interest, these processes are solvent-mediated structural transformations, with obvious colour changes in the crystals. Structural changes and mechanisms of transformation are discussed in detail.

Mechanisms of Solvent-Mediated Structural Transformations for Dynamic Crystals of Supramolecular Coordination Systems.

Thus far, reports about the transformations for dynamic crystals of supramolecular coordination systems mainly include single-crystal-to-single-crystal reactions, and solvent-mediated processes. This Concept focuses on the mechanisms for solvent-mediated structural transformations of dynamic crystals, which can be classified into two categories, that is, core-on-shell and core-to-core. The core-on-shell mechanism means that the core of the new crystal is generated from the shell of original crystal, being concomitant with the dissolution of the mother crystal. In contrast, for the core-to-core case, the growth of new crystal core and the dissolution of original crystal core will proceed simultaneously, but they are physically separated. Herein, the two mechanisms are elucidated in detail, with some typical examples from recent advances.

Two distinct coordination polymers assembled by Ag(CF3SO3) and p-phenylenediacetonitrile and the anion-exchange properties

Complexes 1 and 2 with different unique architectures were derived from Ag(CF 3 SO 3 ) and p -phenylenediacetonitrile by diffusion method and slow evaporation, respectively. In 1 , CF 3 SO 3 − is involved in coordination whereas it behaves as balance charge filled in the voids of 2 . The CF 3 SO 3 − in 2 can be exchanged by other anions with different geometry and volume through a solvent-mediated structural transformation. • Two unique architectures were prepared by diffusion and slow evaporation. • In 1 CF 3 SO 3 − is involved in coordination whereas it behaves as balance charge in 2 . • The CF 3 SO 3 − in 2 can be exchanged by other anions with different geometry and volume.

A Family of Metal–Organic Frameworks with a New Chair-Conformation Resorcin[4]arene-Based Ligand: Selective Luminescent Sensing of Amine and Aldehyde Vapors, and Solvent-Mediated Structural Transformations

By utilizing a new chair-conformation resorcin[4]arene-based octacarboxylate ligand, four functional metal–organic frameworks (MOFs), namely, [(CH3)2NH2]4[Cd2(L)]·4H2O (1), [(CH3)2NH2]4[Zn2(L)]·2DMF·6H2O (2), [(CH3)2NH2]4[Co2(L)]·2DMF·4H2O (3), and [(CH3)2NH2]2[Co3(L)(H2O)12] (4) (H8L = 2,8,14,20-tetra-methylphenyl-4,6,10,12,16,18,22,24-octa-carboxymethoxy-resorcin[4]arene and DMF = N,N-dimethylformamide), were solvothermally synthesized and structurally characterized. In 1, each L8– anion bridges eight Cd(II) atoms to give a three-dimensional (3D) (4,8)-connected (46)(412.610.86) framework. In isostructural 2 and 3, each L8– anion links eight adjacent Zn(II) or Co(II) atoms to yield a 3D (4,8)-connected (46)(411.612.85) net. In 4, each L8– anion only bridges four Co(II) atoms by using its four carboxylates each in a monodentate coordination mode to generate an infinite one-dimensional (1D) chain. Remarkably, the highly selective luminescent sensing of amine and aldehyde vapors was studied for 1 and 2 as ...

Assembly of Cd(ii) coordination polymers: structural variation, supramolecular isomers, and temperature/anion-induced solvent-mediated structural transformations

The reactions of Cd(II) salts and 5-(3-(1H-imidazol-1-yl)phenyl)-1H-tetrazolate (3-HIPT) resulted in eight new coordination polymers (CPs), namely, {[Cd(3-IPT)2(H2O)2]·H2O}n (1 and 2), {[Cd(3-IPT)2(H2O)2]·2H2O}n (3), [Cd(3-IPT)(H2O)Cl]n (4), [Cd(3-IPT)Cl]n (5), [Cd(3-HIPT)I2]n (6), [Cd(3-IPT)I]n (7), and [Cd(3-HIPT)2]n (8). Single-crystal X-ray analysis revealed that compound 1 is a 1D beaded chain, whereas compounds 2 and 3 are made of 2D networks. Compounds 1–3 are supramolecular isomers; their synthesis can be controlled under different temperatures and concentrations. The results showed that compounds 1 and 3 are the most thermodynamically and kinetically favored products, respectively. The thermodynamic stability of compound 1 may be attributed to the formation of the smallest M2L2 ring in the compound. Compounds 4–7 were obtained at higher Cl−/I− concentrations. Compound 4 is a 2D net composed of 1D [Cd(3-IPT)]n chains and μ2-Cl and μ2-H2O connectors. Compound 5 is a (3,6)-connected 3D framework with rtl topology. Compound 6 possesses a 1D chain with 3-HIPT ligands on both sides. Compound 7 is a 2D (4·82) net. Compound 8, a 3D pcu framework based on trinuclear linear SBUs, was formed when Cd(CF3CO2)2 was introduced at 170 °C. Based on a temperature-changing cycle, compounds 1 and 3 display crystal-to-amorphous-to-crystal phase transitions accompanying the dehydration–rehydration process, whereas compound 2 only displays crystal-to-amorphous phase transition when the temperature is increased and cannot go back to the crystal phase again. Interestingly, solvent-mediated structural transformations were accomplished among the selected compounds. When compounds 2, 3, 6, 7, or 8 were left in a water and NaCl solution at 170 °C, they were partly/fully transformed into compounds 1 and 5, respectively. When compound 5 was recrystallized in water at 120 and 170 °C, it was partly and fully transformed into compounds 2 and 1, respectively. Such transformations were induced by the temperature or an anion. In addition, the thermal stabilities and luminescence properties of selected compounds have also been studied in detail. The complexes exhibit intense solid-state fluorescence emission at room temperature.

Heterometallic Sr(II) -M(II) (M=Co, Ni, Zn and Cu) coordination polymers: synthesis, temperature-dependent structural transformation, and luminescent and magnetic properties.

The use of pyridine-2,4-dicarboxylic acid (H2 pydc) in the construction of Sr(II) and Sr(II) -M(II) (M=Co, Ni, Zn and Cu) coordination polymers is reported. Eight complexes, that is, [Sr(pydc)H2 O]n (1), [MSr(pydc)2 (H2 O)2 ]n (M=Co (2), Ni (3), Zn (4)), [ZnSr(pydc)2 (H2 O)7 ]n ⋅4 nH2 O (5), [SrCu(pydc)2 ]n (6), [SrCu(pydc)2 (H2 O)3 ]n ⋅2 nH2 O (7), and [Cu3 Sr2 (pydc)4 (Hpydc)2 (H2 O)2 ]n (8), have been synthesized via dexterously choosing the appropriate strontium sources and transition metal salts, and rationally controlling the temperature of the reaction systems. Complexes 1, 2 (3, 4), 6, and 8 display four types of 3-D framework structures. Complexes 5 and 7 exhibit a 2-D network and a 1-D chain structure, respectively. The 2-D complex 7 can be reversibly transformed into 3-D compound 6 through temperature-induced solvent-mediated structural transformation. The luminescent property studies indicated that complex 1 shows a strong purple luminescent emission and 4 exhibits a strong violet luminescence emission. The magnetic properties of 2, 3, and 8 were also studied. Antiferromagnetic M(II) ⋅⋅⋅M(II) interactions were determined for these complexes.

Anion-dependent assembly and solvent-mediated structural transformations of three Cd(ii) coordination polymers based on 1H-imidazole-4-carboxylic acid

Three new Cd(II) coordination polymers with 1H-imidazole-4-carboxylic acid (Himc), [Cd(Himc)2(H2O)]n (1), [Cd(Himc)2]n (2) and [Cd2(Himc)2(SO4)(H2O)2]n (3) were perpared by solvothermal reactions and structurally characterized, which all comprised metal–negative ligand systems. Compound 1 exhibit a 1D zigzag chain; compound 2 features a 3D diamondoid work; while compound 3 possesses a 2D layer structure consisting of rhomboid grids. When 1 or 2 was left in a water/ethanolic solution of Na2SO4, their 1D or 3D framework was transformed into a 2D framework of 3. All compounds also displayed structure-related photoluminescent properties in the solid state.

Self-assembly and solvent-mediated structural transformation of one-dimensional cluster-based coordination polymer

Reactions between [Nb6Cl12(CN)6]4− and [Mn(salen)]+ in MeOH–H2O solvent mixture led to the formation of a new compound: {[(Mn2(salen)2)][[Mn(salen)(H2O)]0.67[Mn(salen)(MeOH)]1.33(Nb6Cl12(CN)6)]}·1.7H2O·2MeOH (1). Single crystal X-ray analysis has shown that 1 possesses 1D framework built of heterotrimeric supramolecular anions, {[Mn(salen)(s)]2[Nb6Cl12(CN)6]}2− and [Mn2(salen)2]2+ phenoxo bridged dimers linked to each other through two cyanide ligands located in axial positions. When 1 was left in a methanolic solution of (Me4N)+, its 1D framework was transformed into a 2D framework of the previously reported compound [Me4N]2[(Mn(salen))2(Nb6Cl12(CN)6))] (2) which has a 2D anionic 4,4-network built of [Nb6Cl12(CN)6]4− and [Mn(salen)]+ nodes linked by CN ligands (Zhou, Day and Lachgar, Chem. Mater., 2004, 16, 4870).1Magnetic susceptibility measurements indicate that 1 exhibits weak antiferromagnetic interactions due to the phenolate-bridged out-of-plane Mn(III) dimers with J = −1.50(5) cm−1. Thermal stability of 1 was studied.

Metal–Ligand Directed Assembly of Layered Cluster-Based Coordination Polymer and Its Solvent-Mediated Structural Transformations

A two-dimensional (2D) cluster-based coordination polymer with 4,4-net framework was assembled from solution using the metal–ligand directed assembly methodology. The 2D framework undergoes solvent-mediated structural transformations leading to formation of either a three-dimensional hydrogen-bonded framework when using MeOH solution of (Et4N)+ or one-dimensional coordination polymer in the presence of MeOH solution of 4,4′-dipyridyl N,N′-dioxide (dpyo).