The aim of this critical review is to provide a broad but digestible overview of mechanochemical synthesis, i.e. reactions conducted by grinding solid reactants together with no or minimal solvent. Although mechanochemistry has historically been a sideline approach to synthesis it may soon move into the mainstream because it is increasingly apparent that it can be practical, and even advantageous, and because of the opportunities it provides for developing more sustainable methods. Concentrating on recent advances, this article covers industrial aspects, inorganic materials, organic synthesis, cocrystallisation, pharmaceutical aspects, metal complexes (including metal–organic frameworks), supramolecular aspects and characterization methods. The historical development, mechanistic aspects, limitations and opportunities are also discussed (314 references).

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Mechanochemistry: opportunities for new and cleaner synthesis

Deconstructing the Crystal Structures of Metal Organic Frameworks and Related Materials into Their Underlying Nets Michael O’Keeffe* and Omar M. Yaghi* Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, United States Center for Reticular Chemistry, Center for Global Mentoring, Department of Chemistry and Biochemistry, University of California Los Angeles, 607 Charles E. Young Dr. East, Los Angeles, California 90095, United States Graduate School of EEWS, Korea Advanced Institute of Science and Technology, Daejeon, Korea

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Deconstructing the crystal structures of metal-organic frameworks and related materials into their underlying nets.

A new metal-organic framework Zn2(H2O)(dobdc)·0.5(H2O) (UTSA-74, H4dobdc = 2,5-dioxido-1,4-benzenedicarboxylic acid), Zn-MOF-74/CPO-27-Zn isomer, has been synthesized and structurally characterized. It has a novel four coordinated fgl topology with one-dimensional channels of about 8.0 A. Unlike metal sites in the well-established MOF-74 with a rod-packing structure in which each of them is in a five coordinate square pyramidal coordination geometry, there are two different Zn(2+) sites within the binuclear secondary building units in UTSA-74 in which one of them (Zn1) is in a tetrahedral while another (Zn2) in an octahedral coordination geometry. After activation, the two axial water molecules on Zn2 sites can be removed, generating UTSA-74a with two accessible gas binding sites per Zn2 ion. Accordingly, UTSA-74a takes up a moderately high and comparable amount of acetylene (145 cm(3)/cm(3)) to Zn-MOF-74. Interestingly, the accessible Zn(2+) sites in UTSA-74a are bridged by carbon dioxide molecules instead of being terminally bound in Zn-MOF-74, so UTSA-74a adsorbs a much smaller amount of carbon dioxide (90 cm(3)/cm(3)) than Zn-MOF-74 (146 cm(3)/cm(3)) at room temperature and 1 bar, leading to a superior MOF material for highly selective C2H2/CO2 separation. X-ray crystal structures, gas sorption isotherms, molecular modeling, and simulated and experimental breakthroughs comprehensively support this result.

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UTSA-74: A MOF-74 Isomer with Two Accessible Binding Sites per Metal Center for Highly Selective Gas Separation

The ZrW2O8 family of materials has been shown to exhibit the unusual property of negative thermal expansion over a wide temperature range α-ZrW2O8 itself shows negative thermal expansion from 2 K to 1443 K with a coefficient of thermal expansion α1 of -91×10-6 K-1 between 2 and 300 K This behaviour can be related to the unusual structure of these materials, which possess a family of low energy phonon modes with negative Gruneisen parameters α-ZrW2O8 also shows a phase transition at 448 K to β-ZrW2O8 in which oxygen atoms are dynamically disordered These phenomena have been investigated by a number of techniques Results of powder neutron diffraction at 260 different temperatures are presented

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Negative thermal expansion materials

The use of s-block metal centers to construct coordination networks (CNs) is comparatively rare. The predominance of ionic forces and the absence of well-defined secondary building units make the rational construction of porous s-block CNs a challenging task. However, the nontoxic subset of these metals (Li, Na, K, Mg, Ca) based CNs, potentially useful for gas storage, separation, drug delivery, catalysis, and electrochemical applications, makes exploratory synthesis a worthwhile endeavor. In this review, we discuss the recent advances in the synthesis of s-block-CNs, produced using common carboxylic acid based linkers.

Recent Advances in s-Block Metal Carboxylate Networks

CaADC (1) and Mg(ADC)(H2O)2 (2) were synthesized by grinding Ca(CH3COO)2 and Mg(CH3COO)2·4H2O with acetylenedicarboxylic acid (H2ADC) in an agate mortar. After careful heating for two hours in an argon atmosphere at moderate temperatures, 50 °C and 70 °C, respectively, polycrystalline materials of good crystallinity were obtained. The crystal structures of 1 and 2 were solved and refined from X-ray powder diffraction data. In the course of the structural refinement it turned out that 1 and 2 are isotypic to SrADC(I41/amd, Z = 4) and Mn(ADC)(H2O)2 (I2/a, Z = 4). In both compounds metal cations are connected by bridging ADC2– ligands to form a 3D coordination network. Thermoanalytical investigations show that CaADC decomposes above 50 °C, whereas for Mg(ADC)(H2O)2 a mass loss of approx. 33 % is observed above 150 °C. The loss of one water molecule as well as a decarboxylation is very likely. The remaining residue is amorphous to X-rays.

https://hal.archives-ouvertes.fr/hal-00530823/document

Mechanochemical Synthesis of New Coordination Polymers with Acetylenedicarboxylate as Bridging Ligand

Single crystals of PbADC (1) and PbADC·H2O (2) formed at the phase boundary of an aqueous silica gel containing acetylenedicarboxylic acid (HOOC–C≡C–COOH, H2ADC) and an aqueous solution containing Pb(NO3)2. By choosing different concentrations of Pb(NO3)2, compounds 1 and 2 were obtained as phase pure products. Additionally, 1 was obtained by grinding Pb(CH3COO)2·3H2O with H2ADC resulting in a polycrystalline sample. The crystal structures of 1 (I41/amd, Z = 4; SrADC type structure) and 2 (P21/c, Z = 4, new structure type) were solved and refined from X-ray single crystal data. Compound 1 exhibits a three-dimensional framework structure: lead cations with a diamond-like arrangement are interconnected by bridging ADC2– ligands. In 2 double-layers are formed by lead cations, bridging ADC2– anions, and water molecules. These layers are held together by hydrogen bonds through water molecules and oxygen atoms of the ADC2– ligands. Suspending 1 for 24 h in water at ambient conditions leads to the formation of 2, which can be converted to 1 again by careful dehydration at approx. 400 K in vacuo. This reversible reaction can be structurally interpreted as a topochemical reaction, which transforms a 3D coordination network into a 2D network structure and vice versa, as both crystal structures show noticeable structural similarities.

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PbADC and PbADC·H2O: Two Coordination Polymers with Acetylenedicarboxylate (ADC2–) as Bridging Ligand

By slow diffusion of 4,4′-bipyridine (4,4′-bipy) into a solution of a respective metal salt and acetylenedicarboxylic acid (H2ADC), single crystals of four new coordination polymers ∞1[MII(4,4′-bipy)(H2O)4](ADC)·4H2O (MII = Mn, Fe, Co; P, Z = 1) (1–3) and ∞1[Cu(4,4′-bipy)(H2O)4](ADC)·4H2O (C2/c, Z = 4) (4) were obtained. In all compounds octahedral MII(H2O)4N2 units are connected by 4,4′-bipyridine ligands to form chain-like polymers. In 4 these octahedra are elongated due to Jahn–Teller distortion. The acetylenedicarboxylate dianions are bound by hydrogen bonds to the ∞1[MII(4,4′-bipy)2/2(H2O)4] chains to form a 3 D network. Surprisingly, the acetylenedicarboxylate dianions are not part of the first coordination sphere of the transition metal ions.

$^{1}_{\infty}\rm [M^{II}(4,4^{\prime}-bipy)(H_{2}O)_{4}](ADC)\cdot 4H_{2}O$ with MII = Mn, Fe, Co, Cu: Four New Coordination Polymers based on 4,4′‐Bipyridine (4,4′‐bipy) and Acetylenedicarboxylate (ADC2–)

From a solution of [Zn(H2O)6](NO3)2 and acetyl­enedicarb­oxylic acid in deionized water, single crystals of zinc acetyl­ene­dicarboxyl­ate dihydrate, {[Zn(C4O4)(H2O)2]}n, were obtained by slow evaporation of the solvent. The asymmetric unit consits of one zinc cation which is located on a centre of symmetry, half of an acetyl­enedicarboxyl­ate anion, the anion lying on a twofold axis, and one water mol­ecule in a general position. Thus, zinc is octa­hedrally coordinated by four O atoms of acetyl­enedicarboxyl­ate anions and two water mol­ecules in trans positions. These octa­hedra are connected by dicarboxyl­ate ligands into a three-dimensional network.

Poly[diaqua-μ4-acetyl­enedicarboxyl­ato-zinc(II)]

with MII = Fe, Co, Ni (n = 2) and MII = Cu (n = 1): Four New Coordination Polymers with Acetylenedicarboxylate (ADC2−) as Bridging Ligand



By slow diffusion of pyridine (Py) into an aqueous solution of a respective metal salt and acetylenedicarboxylic acid (H2ADC) single crystals of new coordination polymers of composition (M = Fe, Co, Ni; C2/c, Z = 4) (1 – 3) and (P212121, Z = 4) (4) were obtained. In compounds 1 – 3 octahedral MIIO4N2 units are connected via acetylenedicarboxylate anions to form chain-like polymers. In compound 4 square pyramidal CuIIO3N2 units are found, which are also connected to chains by acetylenedicarboxylates. Thermoanalytical investigations on 3 show an abrupt mass loss of approx. 40 % above 130 °C, which points to a release of both pyridine ligands (calc.: 43 %). Thereafter, the sample decomposes continuously, which is confirmed by XRPD measurements, as an amorphous residue is found. Magnetic susceptibility measurements of 1 – 3 display paramagnetic behaviour in the temperature range 2-300 K. While μeff of 3 (d8 configuration) with orbital singlet ground state is nearly temperature-independent, 1 (d6) and 2 (d7) exhibit complicated μeff−T behaviour on account of a ligand-field ground state derived from the cubic states 5T2 and 4T1, respectively. On the basis of a tetragonal ligand-field model excellent adaptations are obtained with reasonable ligand-field parameters. Exchange interactions between the magnetic ions are detected in no case.

$^{1}_{\infty}\rm [M^{II}(Py)_{2}(H_{2}O)_{n}(ADC)_{2/2}]$ mit MII = Fe, Co, Ni (n = 2) und MII = Cu (n = 1): Vier neue Koordinationspolymere mit dem Acetylendicarboxylat‐Dianion (ADC2−) als verbrückendem Liganden

Irena Stein

Papers

Mechanochemical Synthesis of New Coordination Polymers with Acetylenedicarboxylate as Bridging Ligand

PbADC and PbADC·H2O: Two Coordination Polymers with Acetylenedicarboxylate (ADC2–) as Bridging Ligand

$^{1}_{\infty}\rm [M^{II}(4,4^{\prime}-bipy)(H_{2}O)_{4}](ADC)\cdot 4H_{2}O$ with MII = Mn, Fe, Co, Cu: Four New Coordination Polymers based on 4,4′‐Bipyridine (4,4′‐bipy) and Acetylenedicarboxylate (ADC2–)

Poly[diaqua-μ4-acetylenedicarboxylato-zinc(II)]

$^{1}_{\infty}\rm [M^{II}(Py)_{2}(H_{2}O)_{n}(ADC)_{2/2}]$ mit MII = Fe, Co, Ni (n = 2) und MII = Cu (n = 1): Vier neue Koordinationspolymere mit dem Acetylendicarboxylat‐Dianion (ADC2−) als verbrückendem Liganden

Irena Stein

Papers

Mechanochemical Synthesis of New Coordination Polymers with Acetylenedicarboxylate as Bridging Ligand

PbADC and PbADC·H2O: Two Coordination Polymers with Acetylenedicarboxylate (ADC2–) as Bridging Ligand

$^{1}_{\infty}\rm [M^{II}(4,4^{\prime}-bipy)(H_{2}O)_{4}](ADC)\cdot 4H_{2}O$ with MII = Mn, Fe, Co, Cu: Four New Coordination Polymers based on 4,4′‐Bipyridine (4,4′‐bipy) and Acetylenedicarboxylate (ADC2–)

Poly[diaqua-μ4-acetyl­enedicarboxyl­ato-zinc(II)]

$^{1}_{\infty}\rm [M^{II}(Py)_{2}(H_{2}O)_{n}(ADC)_{2/2}]$ mit MII = Fe, Co, Ni (n = 2) und MII = Cu (n = 1): Vier neue Koordinationspolymere mit dem Acetylendicarboxylat‐Dianion (ADC2−) als verbrückendem Liganden

Poly[diaqua-μ4-acetylenedicarboxylato-zinc(II)]