A Dynamic Open Framework Exhibiting Guest- and/or Temperature-Induced Bicycle-Pedal Motion in Single-Crystal to Single-Crystal Transformation

Large Differences in Carbon Dioxide and Water Sorption Capabilities in a System of Closely Related Isoreticular Cd(II)-based Mixed-Ligand Metal-Organic Frameworks

We report the synthesis of two isoreticular, mixed-ligand metal-organic frameworks (MOFs), [Cd(μ₂-mia)(μ₂-bpe)]_n·n(DMF)_0.5·n(H₂O)_0.5 (1) and [Cd(μ₂-nia)(μ₂-bpee)]_n·nDMF (2), where mia = 5-methoxyisophthalate, nia = 5-nitroisophthalate, bpe = 1,2-bis(4-pyridyl)ethane, bpee = 1,2-bis(4-pyridyl)ethylene, and DMF = N,N'-dimethylformamide. Variable-temperature powder X-ray diffraction studies confirmed that both MOFs remain crystalline with activation at high temperatures. Variable-temperature single-crystal X-ray diffraction studies were performed on 1, 2, and a previously published, isoreticular structure, [Cd(μ₂-nia)(μ₂-bpe)_1.5]_n·nDMF_0.84 (3). These studies show that upon desolvation that monocrystallinity is retained to significantly higher temperatures for 2 and 3 when compared to 1 for which only a partially desolvated crystal structure could be obtained. Carbon dioxide sorption is negligible for 1 at 195 and 298 K, while it is higher for 2 than 3 at 298 K and reversed at 195 K. Water vapor sorption increases in the order 1, 2, and 3. On the contrary, water liquid sorption was significantly higher for 1 when compared to 2. The variable-temperature structures of the (partially) desolvated forms of 1, 2, and 3 give some insight into the reasons for the remarkably different gas, vapor, and liquid sorption properties.

Rotation of a helical coordination polymer by mechanical grinding

Anisotropic cell volume expansion by mechanical grinding of the solid facilitates the concerted rotation of the photo-inert helical coordination polymer, which causes the misaligned arms containing olefin functional groups in the neighbouring strands to align to undergo [2+2] cycloaddition reaction in 83% yield.

The effect of coordinated solvent molecules on metal coordination environments in single-crystal-to-single-crystal transformations

We summarized the effect of coordinated solvent molecules on the metal coordination environments in single-crystal to single-crystal transformations.

Cooling-rate dependent single-crystal-to-single-crystal phase transition in an organic co-crystal

A reversible single-crystal-to-single-crystal phase transition is achieved via slow cooling; flash cooling locks the crystal in a kinetically trapped phase.

Photoinduced Pedalo-Type Motion in an Azodicarboxamide-Based Molecular Switch

Well-defined structural changes of molecular units that can be triggered by light are crucial for the development of photoactive functional materials. Herein, we report on a novel switch that has azodicarboxamide as its photo-triggerable element. Time-resolved UV-pump/IR probe spectroscopy in combination with quantum-chemical calculations shows that the azodicarboxamide functionality, in contrast to other azo-based chromophores, does not undergo trans-cis photoisomerization. Instead, a photoinduced pedalo-type motion occurs, which because of its volume-conserving properties enables the design of functional molecular systems with controllable motion in a confined space.

Single crystal-to-single crystal transformations induced by ammonia–water equilibrium changes

Reversible single crystal-to-single crystal transformations were observed for the Ni(ii) complex with 5-methyl-5-phenylhydantoin.

Liquid-free single-crystal to single-crystal transformations in coordination polymers

Single-crystal to single-crystal (SCSC) transformations not only can create new materials, but also provide an opportunity to explore the process of forming a chemical bond. SCSC transformations discussed in this paper are confined to transformationsviaan absolutely liquid-free mode and involve the breakage and formation of new chemical bonds.

The utilization of a stable 2D bilayer MOF for simultaneous study of luminescent and photocatalytic properties: experimental studies and theoretical analysis

A new Pb(ii)-based 2D MOF comprising π-conjugated ligand 4′-(1H-tetrazol-5-yl)-[1,1′-biphenyl]-3,5-dicarboxylic acid (TZBPDC) and having the formula {[PbNa(TZBPDC)](H₂O)(DMF)₂}_n (1) has been synthesized. Structural characterization of 1 indicates that the MOF has a 4-connected (4,4) motif. The photoluminescent investigation indicates that 1 can behave as potential luminescent sensor for the detection of nitroaromatic compounds (NACs), especially 2,4-dinitrophenol (2,4-DNP) and ferric ions, through the decrease in its luminescence intensity. Additionally, 1 also displays excellent capacity for the photodegradation of methylene orange (MO), which is a constituent of wastewater discharge. The most plausible mechanisms for the decrease in the luminescent intensity of 1 in the presence of different NACs have been explored though theoretical calculations, and the photocatalysis of 1 for organic dyes has been addressed using density of states (DOS) and partial DOS calculations.

A new 2D stable Pb(ii)-based MOF has been synthesized and used as dual channel sensor for the detection of ferric ions and nitroaromatics as well as the photocatalyst for the degradation of dyes.

Two new molybdates based on ∞[MonO3n+1]2− units (n = 11, 4) with proton conduction under ionothermal

Two new members of the _∞[Mo_nO_3n+1]²⁻ family with high proton conduction synthesized under ionothermal condition.

Light-triggered Supramolecular Isomerism in a Self-catenated Zn(II)-organic Framework: Dynamic Photo-switching CO2 Uptake and Detection of Nitroaromatics

A self-catenated Zn(II)-organic framework formulated as [Zn₂(3,3′-bpeab)(oba)₂]·DMF (1) exhibiting a six-connected 4⁴·6¹⁰·8 topology has been successfully synthesized through the mixed-ligand of kinked 3,3′-bis[2-(4-pyridyl)ethenyl]azobenzene (3,3′-bpeab) and 4,4′-oxybis-benzoic acid (H₂oba) under solvothermal condition. UV light triggers isomerization of complex 1 in a single-crystal-to-single-crystal (SCSC) manner, giving rise to a conformational supramolecular isomer 1_UV through the pedal motion of photoresponsive double bonds. Dynamic photo-switching in the obtained light-responsive supramolecular isomers leads to instantly reversible CO₂ uptake. Furthermore, the ligand originated fluorescence emission of water-resistant complex 1 is selectively sensitive to 4-nitrotoluene (4-NT) owing to a higher quenching efficiency of the perilous explosive over other structurally similar nitroaromatics, prefiguring the potentials of 1 as a fluorescence sensor towards 4-NT in aquatic media.

Thermodynamic parameters of the pedal motion in the crystal structures of two bromomethylated azobenzenes

Differences in the thermodynamic parameters of the central N-atoms' pedal motion in two bromomethylated azobenzenes were determined by multi-temperature X-ray diffraction, and rationalized by packing studies.

In situ variable-temperature single crystal X-ray diffraction studies of the single-crystal-to-single-crystal dehydration and rehydration of a mixed-ligand 2D zinc metal–organic framework using trimesate and 4,4′-bipyridine-N,N′-dioxide as ligands

A mixed-ligand 2D MOF based on ZnSO₄, trimesate and 4,4′-bipyridine-N,N′-dioxide shows reversible loss of uncoordinated and coordinated water molecules.

Solvent induced single-crystal to single-crystal structural transformation and concomitant transmetalation in a 3D cationic Zn(ii)-framework

Guest solvent triggered reversible structural transformation and concomitant Zn(ii) to Cu(ii) transmetalation has been realized through single-crystal to single-crystal fashion in an imidazolium functionalized 3D cationic Zn(ii)-framework.

Reversible single-crystal-to-single-crystal transformation from a mononuclear complex to a fourfold interpenetrated MOF with selective adsorption of CO2

Reversible crystal transformation was observed between a mononuclear complex to a fourfold interpenetrated MOF with selective adsorption of CO₂ up to 12.5 wt% at room temperature and low pressure.

Photoreactivity of polymorphs of a ladder polymer with criss-cross and parallel orientations of C=C bonds

Two polymorphic forms of a ladder coordination polymer [Zn2(μ-O2C-p-Tol)2(O2C-p-Tol)2(bpe)2] have parallel and criss-cross alignments of the C=C bond pairs. Both polymorphs undergo 100% [2+2] cycloaddition reaction but the one with a parallel orientation of C=C bonds (thermodynamic product) retains its single crystallinity after the reaction.

Is metal metathesis a framework-templating strategy to synthesize coordination polymers (CPs)? Transmetallation studies involving flexible ligands

Framework-templating strategy, where Cd-CP acted as template to preorganise the linkers, resulted in a Cu-CP, which was not obtained by direct reaction of Cu(ii) and the ligand.

Hetero-nuclear coordinated compounds for use in high-performance supercapacitor electrode material design

Ni–Co complexes are prepared using cobalt coordination complex as precursors by nickel exchange method. Single-crystal to single-crystal transformation had been achieved. Using Ni–Co complex as the precursors, we have synthesized a series of 3D hierarchical Ni_xCo_3−xS₄ microflowers electrode materials for supercapacitors.

A 3D MOF showing unprecedented solvent-induced single-crystal-to-single-crystal transformation and excellent CO2 adsorption selectivity at room temperature

A multifunctional MOF material showing rare solvent-induced structural transformation with substitution of bridging-water and guest-exchange at 298 K is reported.

Crankshafts: using simple, flat C2h-symmetric molecules to direct the assembly of chiral 2D nanopatterns

Linear D2h-symmetric bisisophthalic acids 1 and 2 and related substances have well-defined flattened structures, high affinities for graphite, and strong abilities to engage in specific intermolecular interactions. Their adsorption produces characteristic nanopatterns that reveal how 2D molecular organization can be controlled by reliable interadsorbate interactions such as hydrogen bonds when properly oriented by molecular geometry. In addition, the behavior of these compounds shows how large-scale organization can be obstructed by programming molecules to associate strongly according to competing motifs that have similar stability and can coexist smoothly without creating significant defects. Analogous new bisisophthalic acids 3a and 4a have similar associative properties, and their unique C2h-symmetric crankshaft geometry gives them the added ability to probe the poorly understood effect of chirality on molecular organization. Their adsorption shows how nanopatterns composed predictably of a single enantiomer can be obtained by depositing molecules that can respect established rules of association only by accepting neighbors of the same configuration. In addition, an analysis of the adsorption of crankshaft compounds 3a and 4a and their derivatives by STM reveals directly on the molecular level how kinetics and thermodynamics compete to control the crystallization of chiral compounds. In such ways, detailed studies of the adsorption of properly designed compounds on surfaces are proving to be a powerful way to discover and test rules that broadly govern molecular organization in both 2D and 3D.

Structural Diversity and Magnetic Properties of Five Cu(II) Complexes with Mixed Naphthalene-Based Dicarboxyl Tecton and Different N-Donor Co-Ligands

Five new Cu(ii) complexes have been prepared by employing 2,3-naphthalenedicarboxylic acid (H2ndc) and different N-donor co-ligands, namely, [Cu(ndc)(H2O)]n (1), [Cu(ndc)(H2O)2]n (2), {[Cu1.5(ndc)(OH)(H2O)2]·2.5H2O}n (3), {[Cu(ndc)(phen)(H2O)]·CH3OH}n (4) (phen = 1,10-phenanthroline), and {[Cu2(H0.5ndc)2(4bpy)3](ClO4)·2H2O}n (5) (4bpy = 4,4′-bipyridine). Complex 1 displays a two-dimensional (2D) (4,6)-connected (32.44)2(34.42.64.75)(34.43.64.74) coordination network. Complex 2 shows a 2D 3-connected hcb network which is further interlinked via the interlayered C–H⋯π interactions to result in a three-dimensional (3D) supramolecular network. Complex 3 is a one-dimensional (1D) coordination chain which is further interlinked by the C–H⋯π and π⋯π interactions to lead to the formation of the final 3D supramolecular network. When the N-donor co-ligands phen and 4,4′-bipyridine (4bpy) were introduced, the 1D complex 4 and the 4-connected sql layered complex 5 were constructed, respectively. The final supramolecular frameworks of 4 (2D) and 5 (3D) are extended by hydrogen-bonding and C–H⋯π interactions. The structural diversity of the complexes was triggered by different reaction conditions and N-donor co-ligands. Moreover, the magnetic properties of the complexes have also been investigated and discussed.