Gate-opening Induced by C8 Aromatics in a Double Diamondoid Coordination Network.

Coordination networks (CNs) that undergo guest-induced structural transformations are of topical interest thanks to their potential utility in separations and storage applications. Herein, we report a double diamondoid () topology CN, [Ni(bimpz)(bdc)(HO)] or (Hbdc = 1,4-benzenedicarboxylic acid, bimpz = 3,6-bis(imidazol-1-yl)pyridazine), that undergoes structural transformations induced by C8 isomers, i.e.

Effect of Polymorphism on the Sorption Properties of a Flexible Square-Lattice Topology Coordination Network.

The stimulus-responsive behavior of coordination networks (CNs), which switch between closed (nonporous) and open (porous) phases, is of interest because of its potential utility in gas storage and separation. Herein, we report two polymorphs of a new square-lattice () topology CN, , of formula [Cu(Imibz)] (HImibz = {[4-(1-imidazol-1-yl)phenylimino]methyl}benzoic acid), isolated from the as-synthesized CN , which subsequently transformed to a narrow pore solvate, , upon mild activation (drying in air or heating at 333 K under nitrogen). contains MeOH in cavities, which was removed through exposure to vacuum for 2 h, yielding the nonporous (closed) phase .

Metal cation substitution can tune CO, HO and CH switching pressure in transiently porous coordination networks.

Compared to rigid physisorbents, switching coordination networks that reversibly transform between closed (non-porous) and open (porous) phases offer promise for gas/vapour storage and separation owing to their improved working capacity and desirable thermal management properties. We recently introduced a coordination network, X-dmp-1-Co, which exhibits switching enabled by transient porosity. The resulting "open" phases are generated at threshold pressures even though they are conventionally non-porous.

Effect of Extra-Framework Anion Substitution on the Properties of a Chiral Crystalline Sponge.

Chiral metal-organic materials, CMOMs, are of interest as they can offer selective binding sites for chiral guests. Such binding sites can enable CMOMs to serve as chiral crystalline sponges (CCSs) to determine molecular structure and/or purify enantiomers. We recently reported on the chiral recognition properties of a homochiral cationic diamondoid, dia, network {[Ni(-IDEC)(bipy)(HO)][NO]} (-IDEC = -indoline-2-carboxylicate, bipy = 4,4'-bipyridine), .

Control over Phase Transformations in a Family of Flexible Double Diamondoid Coordination Networks through Linker Ligand Substitution.

In this work, we present the first metal-organic framework (MOF) platform with a self-penetrated double diamondoid () topology that exhibits switching between closed (nonporous) and open (porous) phases induced by exposure to gases. A crystal engineering strategy, linker ligand substitution, was used to control gas sorption properties for CO and C3 gases. Specifically, bimbz (1,4-bis(imidazol-1-yl)benzene) in the coordination network ([Ni(bimbz)(bdc)(HO)], Hbdc = 1,4-benzenedicarboxylic acid) was replaced by bimpz (3,6-bis(imidazol-1-yl)pyridazine) in ([Ni(bimpz)(bdc)(HO)]).

One Atom Can Make All the Difference: Gas-Induced Phase Transformations in Bisimidazole-Linked Diamondoid Coordination Networks.

Coordination networks (CNs) that undergo gas-induced transformation from closed (nonporous) to open (porous) structures are of potential utility in gas storage applications, but their development is hindered by limited control over their switching mechanisms and pressures. In this work, we report two CNs, [Co(bimpy)(bdc)] () and [Co(bimbz)(bdc)] () (Hbdc = 1,4-benzendicarboxylic acid; bimpy = 2,5-bis(1H-imidazole-1-yl)pyridine; bimbz = 1,4-bis(1H-imidazole-1-yl)benzene), that both undergo transformation from closed to isostructural open phases involving at least a 27% increase in cell volume. Although and only differ from one another by one atom in their -donor linkers (bimpy = pyridine, and bimbz = benzene), this results in different pore chemistry and switching mechanisms.

Crystal Engineering of Two Light and Pressure Responsive Physisorbents.

An emerging strategy in the design of efficient gas storage technologies is the development of stimuli-responsive physisorbents which undergo transformations in response to a particular stimulus, such as pressure, heat or light. Herein, we report two isostructural light modulated adsorbents (LMAs) containing bis-3-thienylcyclopentene (BTCP), LMA-1 [Cd(BTCP)(DPT) ] (DPT=2,5-diphenylbenzene-1,4-dicarboxylate) and LMA-2 [Cd(BTCP)(FDPT) ] (FDPT=5-fluoro-2,diphenylbenzene-1,4-dicarboxylate). Both LMAs undergo pressure induced switching transformations from non-porous to porous via adsorption of N , CO and C H .

Reversible transformations between the non-porous phases of a flexible coordination network enabled by transient porosity.

Flexible metal-organic materials that exhibit stimulus-responsive switching between closed (non-porous) and open (porous) structures induced by gas molecules are of potential utility in gas storage and separation. Such behaviour is currently limited to a few dozen physisorbents that typically switch through a breathing mechanism requiring structural contortions. Here we show a clathrate (non-porous) coordination network that undergoes gas-induced switching between multiple non-porous phases through transient porosity, which involves the diffusion of guests between discrete voids through intra-network distortions.

Structural Phase Transformations Induced by Guest Molecules in a Nickel-Based 2D Square Lattice Coordination Network.

Herein, we report the crystal structure and guest binding properties of a new two-dimensional (2D) square lattice () topology coordination network, , which is comprised of two linker ligands with diazene (azo) moieties, ()-1,2-di(pyridin-4-yl)diazene(azpy) and ()-5-(phenyldiazenyl)isophthallate(pdia). underwent guest-induced switching between a closed (nonporous) phase and several open (porous) phases, but unlike the clay-like layer expansion to distinct phases previously reported in switching networks, a continuum of phases was formed. In effect, exhibited elastic-like properties induced by adaptive guest binding.

Solvent-controlled elongation and mechanochemical strain in a metal-organic framework.

Under high pressure, crystals of [Zn()()]·2DMF·HO, referred to as DMOF are particularly sensitive to the type of pressure-transmitting media (PTM) employed: large PTM molecules seal the pores and DMOF is compressed as a closed system, whereas small PTM molecules are pushed into the pores, thereby altering the stoichiometry of DMOF. Compression in glycerol and Daphne 7474 leads to negative linear compressibility (NLC), while a mixture of methanol : ethanol : water 'hyperfills' the pores of the chiral framework, adjusting its 3-dimensional strain and resulting in pressure-induced amorphization around 1.2 GPa.

Large negative linear compressibility of a porous molecular co-crystal.

Flexible and transformable molecules, particularly those responding to external stimuli, are needed for designing sensors and porous compounds capable of storing or separating gases and liquids. Under normal conditions the photochromic compound, 1,2-bis[2-methyl-5-(pyridyl)-3thienyl]cyclopentene (BTCP) forms a porous co-crystal with 1,4-diiodotetrafluorobenzene (dItFB). It traps acetone (Ac) molecules in the pores.

Record-Setting Selectivity for -Xylene by an Intrinsically Porous Zero-Dimensional Metallocycle.

In its crystalline state, a dinuclear Cu-based metallocycle discriminates between the three isomers of xylene with liquid-phase selectivity in the order -xylene ≫ -xylene ≫ -xylene. This selectivity holds over a wide concentration range, with -xylene concentrations as low as 5%. Single-crystal X-ray diffraction and gas chromatography further indicate that the metallocyclic host extracts trace amounts of -xylene from commercially pure -xylene (≥99%); using NMR spectroscopy, we show that the metallocycle exhibits exclusive selectivity for -xylene.

Solvent-Mediated Synthesis of Cyclobutane Isomers in a Photoactive Cadmium(II) Porous Coordination Polymer.

Photochemical [2+2] cycloaddition of 1,4-bis[2-(4-pyridyl)ethenyl]benzene, carried out in a Cd porous coordination polymer (PCP), produces different isomeric products depending on the guest solvent present in the PCP during irradiation. The nature of the included guest influences the conformation of the ligand, and thus the outcome of the cycloaddition reaction. We demonstrate controlled production of the two isomers from the same PCP by simple exchange of solvent.

Single-Crystal to Single-Crystal Uptake of Volatile Solids and Associated Chromatic Response in a Porous Metallocycle.

Guest molecules have been absorbed into crystals of a metallocyclic host by sublimation of volatile solids at room temperature. The guest exchanges are accompanied by color changes. Since the crystals remain intact, evidence of guest inclusion could be obtained using single-crystal X-ray diffraction.

Guest-Induced Structural Transformations in a Porous Halogen-Bonded Framework.

Structural evidence obtained from in situ X-ray diffraction shows that halogen bonding is responsible for the formation of a dynamic porous molecular solid. This material is surprisingly robust and undergoes reversible switching of its pore volume by activation or by exposure to a series of gases of different sizes and shapes. Volumetric gas sorption and pressure-gradient differential scanning calorimetry (P-DSC) data provide further mechanistic insight into the breathing behavior.

Supramolecular solvatochromism: mechanistic insight from crystallography, spectroscopy and theory.

A solvatochromic dinuclear copper(ii) metallocycle effectively traps tetrahydrofuran, diethyl ether and pentane significantly above their boiling points. X-ray crystallography, EPR and UV-visible spectroscopy were used to delineate an empirical relationship between the guest-induced structural perturbation of the metallocycle, the ligand field splitting parameter Δ (νmax), and the EPR g-values of the inclusion compounds, thereby elucidating the solvatochromic mechanism.

Inclusion of a dithiadiazolyl radical in a seemingly non-porous solid.

Inclusion of the dithiadiazolyl radical PhCNSSN˙ into the dynamically porous metallocycle [Cu(L1)Cl], where L1 is the bidentate ligand 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene, has been achieved by gas phase diffusion. Single crystal X-ray diffraction, powder X-ray diffraction, UV-visible spectroscopy, EPR and SQUID magnetometry studies confirm inclusion of the radical into this seemingly non-porous material, and illustrate the antiferromagnetic coupling between the paramagnetic host and guest species. The radical guest is readily released by heating or by the addition of solvent (CHCl).

Threading the needle: guest transport in a versatile 0D porous molecular crystal.

Porous host crystals of the metallocycle [Cu(1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene)Cl]·2CHOH are permeable to a series of small organic guests despite their lack of permanent channels. It is inferred from single crystal X-ray diffraction that transport of the guest molecules is facilitated by "flapping" of the imidazolyl rings.

Reversible structural switching of a metal-organic framework by photoirradiation.

A photoresponsive metal organic framework material undergoes switching of its pore volume and sorption capacity. UV irradiation of the crystals causes cyclisation within the bis-thienylcyclopentene bridging ligands, thereby altering the node positions relative to one another along the Zn-L-Zn linkages. Incorporation of conformational flexibility into the dicarboxylic acid co-ligands facilitates the change in the framework geometry enforced by photocyclisation.

1,2-Bis[(2,2':6',2''-terpyridin-4'-yl)-oxy]ethane.

The title compound, C(32)H(24)N(6)O(2), has an inversion centre located at the mid-point of the central C-C bond of the diether bridging unit. The terminal pyridine rings are canted relative to the central pyridine ring, with dihedral angles of 12.98 (6) and 26.

1,6-Bis[(2,2':6',2''-terpyridin-4'-yl)-oxy]hexa-ne.

The mol-ecule of the title compound, C(36)H(32)N(6)O(2), lies about an inversion center, located at the mid-point of the central C-C bond of the diether bridge. The terminal pyridine rings form dihedral angles of 4.67 (7) and 26.

1,4-Bis[(2,2':6',2''-terpyridin-4'-yl)-oxy]butane.

The title compound, C(34)H(28)N(6)O(2), has an inversion centre located at the mid-point of the central C-C bond of the diether bridging unit. The central pyridine rings of the terpyridyl units and the diether chain are co-planar: the maximum deviation from the 18-atom mean plane defined by the bridging unit and the central pyridyl ring is for the pyridyl N atom which sits 0.055 (1) Å above the plane.