Tetradihydrobenzoquinonate and Tetrachloranilate Zr(IV) Complexes: Single-Crystal-to-Single-Crystal Phase Transition and Open-Framework Behavior for K₄Zr(DBQ)₄

The molecular complexes K₄[Zr­(DBQ)₄] and K₄[Zr­(CA)₄], where DBQ^2– and CA^2– stand respectively for deprotonated dihydroxybenzoquinone and chloranilic acid, are reported. The anionic metal complexes consist of Zr­(IV) surrounded by four O,O-chelating ligands. Besides the preparation and crystal structures for the two complexes, we show that in the solid state the DBQ complex forms a 3-D open framework (with 22% accessible volume) that undergoes a crystal-to-crystal phase transition to a compact structure upon guest molecule release. This process is reversible. In the presence of H₂O, CO₂, and other small molecules, the framework opens and accommodates guest molecules. CO₂ adsorption isotherms show that the framework breathing occurs only when a slight gas pressure is applied. Crystal structures for both the hydrated and guest free phases of K₄[Zr­(DBQ)₄] have been investigated

Tetradihydrobenzoquinonate and Tetrachloranilate Zr(IV) Complexes: Single-Crystal-to-Single-Crystal Phase Transition and Open-Framework Behavior for K₄Zr(DBQ)₄

The molecular complexes K₄[Zr­(DBQ)₄] and K₄[Zr­(CA)₄], where DBQ^2– and CA^2– stand respectively for deprotonated dihydroxybenzoquinone and chloranilic acid, are reported. The anionic metal complexes consist of Zr­(IV) surrounded by four O,O-chelating ligands. Besides the preparation and crystal structures for the two complexes, we show that in the solid state the DBQ complex forms a 3-D open framework (with 22% accessible volume) that undergoes a crystal-to-crystal phase transition to a compact structure upon guest molecule release. This process is reversible. In the presence of H₂O, CO₂, and other small molecules, the framework opens and accommodates guest molecules. CO₂ adsorption isotherms show that the framework breathing occurs only when a slight gas pressure is applied. Crystal structures for both the hydrated and guest free phases of K₄[Zr­(DBQ)₄] have been investigated

Cadmium Metal–Organic Frameworks Based on Ditopic Triazamacrocyclic Linkers: Unusual Structural Features and Selective CO₂ Capture

Two three-dimensional cadmium metal–organic frameworks with general formula [Cd₂(<b>L</b>^<b>1</b>)­(H₂O)₃]­(NO₃)_0.7­(HCOO)_0.2Br_0.1 (<b>Cd</b>_<b>2</b><b>L</b>^<b>1</b>, <b>L</b>^<b>1</b> = 1,4,7-tris­(4-carboxybenzyl)-1,4,7-triazacyclononane) and Cd­(<b>HL</b>^<b>2</b>)­(H₂O)₂ (<b>CdL</b>^<b>2</b>, <b>L</b>^<b>2</b> = 1,4,7-tris­(3-(4-benzoate)­prop-2-yn-1-yl)-1,4,7-triazacyclononane) based on 1,4,7-triazacyclononane <i>N</i>-functionalized by different arylcarboxylic acids were prepared under solvothermal conditions and characterized by single crystal X-ray analysis and porosity measurements. The crystal structure of <b>Cd</b>_<b>2</b><b>L</b>^<b>1</b> reveals a cationic net with a <i>bcs</i> topology, and nodes are constituted by dinuclear cadmium complexes, in which each cadmium atom adopts a hexacoordinated environment involving both the carboxylate and the cyclic amine. In contrast, <b>CdL</b>^<b>2</b> displays a 2-fold interpenetrated structure with a <i>pcu</i> topology. In this net, the node is a mononuclear complex in which the Cd atom exhibits a seven-coordination geometry. Both materials show a high permanent porosity and good CO₂ adsorption properties with a high selectivity over N₂ and CH₄. The adsorption capacity and selectivity for CO₂ were calculated from a multisite Langmuir isotherm model and the ideal adsorbed solution theory, which gave insights into the nature of solid–gas interactions and showed the influence of interpenetration or polarity of the charged framework on their adsorption properties

Tetradihydrobenzoquinonate and Tetrachloranilate Zr(IV) Complexes: Single-Crystal-to-Single-Crystal Phase Transition and Open-Framework Behavior for K₄Zr(DBQ)₄

The molecular complexes K₄[Zr­(DBQ)₄] and K₄[Zr­(CA)₄], where DBQ^2– and CA^2– stand respectively for deprotonated dihydroxybenzoquinone and chloranilic acid, are reported. The anionic metal complexes consist of Zr­(IV) surrounded by four O,O-chelating ligands. Besides the preparation and crystal structures for the two complexes, we show that in the solid state the DBQ complex forms a 3-D open framework (with 22% accessible volume) that undergoes a crystal-to-crystal phase transition to a compact structure upon guest molecule release. This process is reversible. In the presence of H₂O, CO₂, and other small molecules, the framework opens and accommodates guest molecules. CO₂ adsorption isotherms show that the framework breathing occurs only when a slight gas pressure is applied. Crystal structures for both the hydrated and guest free phases of K₄[Zr­(DBQ)₄] have been investigated

Tetradihydrobenzoquinonate and Tetrachloranilate Zr(IV) Complexes: Single-Crystal-to-Single-Crystal Phase Transition and Open-Framework Behavior for K₄Zr(DBQ)₄

The molecular complexes K₄[Zr­(DBQ)₄] and K₄[Zr­(CA)₄], where DBQ^2– and CA^2– stand respectively for deprotonated dihydroxybenzoquinone and chloranilic acid, are reported. The anionic metal complexes consist of Zr­(IV) surrounded by four O,O-chelating ligands. Besides the preparation and crystal structures for the two complexes, we show that in the solid state the DBQ complex forms a 3-D open framework (with 22% accessible volume) that undergoes a crystal-to-crystal phase transition to a compact structure upon guest molecule release. This process is reversible. In the presence of H₂O, CO₂, and other small molecules, the framework opens and accommodates guest molecules. CO₂ adsorption isotherms show that the framework breathing occurs only when a slight gas pressure is applied. Crystal structures for both the hydrated and guest free phases of K₄[Zr­(DBQ)₄] have been investigated

From ZIF-8@Al₂O₃ Composites to Self-Supported ZIF‑8 One-Dimensional Superstructures

Efficient preparation of composite materials consisting of ZIF-8 nanocrystals embedded inside the channels of macroporous anodic aluminum oxide membranes is reported. 1-D self-supported ZIF-8 superstructures are recovered through matrix dissolution

Self-Assembly of Zr(C₂O₄)₄^4– Metallotectons and Bisimidazolium Cations: Influence of the Dication on H-Bonded Framework Dimensionality and Material Potential Porosity

Assemblies involving [Zr(C₂O₄)₄]^4– metallotectons (C₂O₄^2– = oxalate) and linear, flexible, or V-shaped organic cations (H₂-Lx)²⁺ derived from the 1,4-bisimidazol-1-ylbenzene molecule have been envisioned to elaborate porous frameworks based on ionic H-bonds. Five architectures of formula [{(H₂-L1)₂Zr(C₂O₄)₄}·2H₂O] (<b>1</b>), [{(H₂-L2)₂Zr(C₂O₄)₄}·6H₂O] (<b>2</b>), [{(H₂-L3)₂Zr(C₂O₄)₄}·6H₂O] (<b>3</b>), [{(H₂-L4)₂Zr(C₂O₄)₄}·H₂O] (<b>4</b>), and [{(H₂-L5)₂Zr(C₂O₄)₄}·6H₂O] (<b>5</b>) (with L1 = <i>p</i>-bis(imidazol-1-yl)benzene, L2 = <i>p</i>-bis(2-methylimidazol-1-yl)benzene, L3 = <i>p</i>-bis(imidazol-1-yl)-2,5-dimethylbenzene, L4 = <i>p</i>-bis(imidazol-1-ylmethyl)benzene, L5 = <i>m</i>-bis(imidazol-1-yl)benzene) have been obtained; <b>1</b>–<b>3</b>, and <b>5</b> show an open-framework. For all, the bisimidazolium cations (H₂-Lx)²⁺ act as bridges between anionic complexes. Depending on the chemical features of the cation, various assembling patterns have been observed, yielding one-dimensional (1D) (<b>2</b>, <b>5</b>) two-dimensional (2D) (<b>1</b>), or three-dimensional (3D) (<b>3</b>, <b>4</b>) H-bonded networks. While interconnection of anionic metallotectons and organic cations generally affords grids with large apertures, 2D and 3D H-bonded frameworks show the lowest potential porosities (and even compact architectures) because of interpenetration. Highest potential solvent accessible voids (up to 20%) are found for the 1D H-bonded assemblages because interpenetration does not occur for these materials. Crystal structures for all five architectures as well as their thermal stabilities are reported. Actual porosity has been evidenced for one of them by solving the structure of the guest free architecture

A Comparative IRMPD and DFT Study of Fe³⁺ and UO₂²⁺ Complexation with <i>N</i>‑Methylacetohydroxamic Acid

Iron­(III) and uranyl complexes of <i>N</i>-methylacetohydroxamic acid (NMAH) have been investigated by mass spectrometry, infrared multiphoton dissociation (IRMPD) spectroscopy, and density functional theory (DFT) calculations. A comparison between IRMPD and theoretical IR spectra enabled one to probe the structures for some selected complexes detected in the gas phase. The results show that coordination of Fe³⁺ and UO₂²⁺ by hydroxamic acid is of a very similar nature. Natural bond orbital analysis suggests that bonding in uranyl complexes possesses a slightly stronger ionic character than that in iron complexes. Collision-induced dissociation (CID), IRMPD, and ¹⁸O-labeling experiments unambiguously revealed a rare example of the UO bond activation concomitant with the elimination of a water molecule from the gaseous [UO₂(NMA)­(NMAH)₂]⁺ complex. The UO bond activation is observed only for complexes with one monodentate NMAH molecule forming a hydrogen bond toward one “yl” oxygen atom, as was found by DFT calculations. This reactivity might explain oxygen exchange observed for uranyl complexes