Co-crystal engineering is a promising method to create new classes of advanced materials. Co-crystal structure prediction is more challenging when one or more of the lattice constituents (tectons) are flexible molecules. This study reports four co-crystals that were prepared by mixing HAuCl 4 or HAuBr 4 with C 3 -symmetric tectons based on a 1,3,5-(methylacetamide)benzene scaffold. X-ray analysis of the co-crystals revealed the presence of three dominant supramolecular interactions; (a) hydrogen bonding between tecton amide NH residues and the AuX 4 − anion, (b) electrostatic stacking of the Au center against the tecton's π-electrons, (c) very short hydrogen bonds within a proton-bridged-carbonyls motif. Within all four co-crystals, the sterically-geared tecton was trapped in a high energy molecular conformation, which increased the number of favorable intermolecular interactions in the lattice. We infer from the results that the likelihood of high energy molecular conformations within a co-crystal increases if there are multiple dominant intermolecular interactions. Application of this generalizable rule should lead to improved crystal structure prediction.
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Supramolecular Paradigm for Capture and Co‐Precipitation of Gold(III) Coordination Complexes
A new supramolecular paradigm is presented for reliable capture and co‐precipitation of haloauric acids (HAuX4) from organic solvents or water. Two classes of acyclic organic compounds act as complementary receptors (tectons) by forming two sets of directional non‐covalent interactions, (a) hydrogen bonding between amide (or amidinium) NH residues and the electronegative X ligands on the AuX4−, and (b) electrostatic stacking of the electron deficient Au center against the face of an aromatic surface. X‐ray diffraction analysis of four co‐crystal structures reveals the additional common feature of proton bridged carbonyls as a new and predictable supramolecular design element that creates one‐dimensional polymers linked by very short hydrogen bonds (CO⋅⋅⋅OC distance <2.5 Å). Two other co‐crystal structures show that the amidinium‐π⋅⋅⋅XAu interaction will reliably engage AuX4−with high directionality. These acyclic compounds are very attractive as co‐precipitation agents within new “green” gold recovery processes. They also have high potential as tectons for controlled self‐assembly or co‐crystal engineering of haloaurate composites. More generally, the supramolecular paradigm will facilitate the design of next‐generation receptors or tectons with high affinity for precious metal square planar coordination complexes for use in advanced materials, nanotechnology, or medicine.
more » « less- Award ID(s):
- 1708240
- NSF-PAR ID:
- 10236610
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 27
- Issue:
- 2
- ISSN:
- 0947-6539
- Page Range / eLocation ID:
- p. 751-757
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Organofunctionalized tetranuclear clusters [(MIICl)2(VIVO)2{((HOCH2CH2)(H)N(CH2CH2O))(HN(CH2CH2O)2)}2] (
1 , M=Co,2 : M=Zn) containing an unprecedented oxometallacyclic {M2V2Cl2N4O8} (M=Co, Zn) framework have been prepared by solvothermal reactions. The new oxo‐alkoxide compounds were fully characterized by spectroscopic methods, magnetic susceptibility measurement, DFT and ab initio computational methods, and complete single‐crystal X‐ray diffraction structure analysis. The isostructural clusters are formed of edge‐sharing octahedral {VO5N} and trigonal bipyramidal {MO3NCl} units. Diethanolamine ligates the bimetallic lacunary double cubane core of1 and2 in an unusual two‐mode fashion, unobserved previously. In the crystalline state, the clusters of1 and2 are joined by hydrogen bonds to form a three‐dimensional network structure. Magnetic susceptibility data indicate weakly antiferromagnetic interactions between the vanadium centers [J iso(VIV−VIV)=−5.4(1 ); −3.9(2 ) cm−1], and inequivalent antiferromagnetic interactions between the cobalt and vanadium centers [J iso(VIV−CoII)=−12.6 and −7.5 cm−1] contained in1 . -
Selective binding and transport of highly hydrophilic anions is ubiquitous in nature, as anion binding proteins can differentiate between similar anions with over a million-fold efficiency. While comparable selectivity has occasionally been achieved for certain anions using small, artificial receptors, the selective binding of certain anions, such as sulfate in the presence of carbonate, remains a very challenging task. Nanojars of the formula [anion⊂{Cu(OH)(pz)} n ] 2− (pz = pyrazolate; n = 27–33) are totally selective for either CO 3 2− or SO 4 2− over anions such as NO 3 − , ClO 4 − , BF 4 − , Cl − , Br − and I − , but cannot differentiate between the two. We hypothesized that rigidification of the nanojar outer shell by tethering pairs of pyrazole moieties together will restrict the possible orientations of the OH hydrogen-bond donor groups in the anion-binding cavity of nanojars, similarly to anion-binding proteins, and will lead to selectivity. Indeed, by using either homoleptic or heteroleptic nanojars of the general formula [anion⊂Cu n (OH) n (L2–L6) y (pz) n −2 y ] 2− ( n = 26–31) based on a series of homologous ligands HpzCH 2 (CH 2 ) x CH 2 pzH ( x = 0–4; H 2 L2–H 2 L6), selectivity for carbonate (with L2 and with L4–L6/pz mixtures) or for sulfate (with L3) has been achieved. The synthesis of new ligands H 2 L3, H 2 L4 and H 2 L5, X-ray crystal structures of H 2 L4 and the tetrahydropyranyl-protected derivatives (THP) 2 L4 and (THP) 2 L5, synthesis and characterization by electrospray-ionization mass spectrometry (ESI-MS) of carbonate- and sulfate-nanojars derived from ligands H 2 L2–H 2 L6, as well as detailed selectivity studies for CO 3 2− vs. SO 4 2− using these novel nanojars are presented.more » « less
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Abstract Extended tetratopic benzoic acid ligands with “orthogonal‐twisted‐arms” conformations were designed and synthesized for the construction of new MOF structures (OTA‐MOF). Upon coordination with Cd2+and Cu2+cations, two well‐defined new MOFs were prepared. X‐ray single crystal structures were successfully obtained, demonstrating the formation of a new topology (4,4,4‐c). The OTA2‐MOF‐Cu gave moderate stability in organic solvents and good gas sorption ability toward CO2. This new MOF showed superior catalytic reactivity toward the epoxide‐CO2cycloaddition, giving >50 folds yield enhancement over the controlled reaction without MOF. It is expected that this new ligand design, porous structure, and excellent CO2catalytic reactivity will make OTA‐MOF promising new materials for applications in catalysis and separation.
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Abstract There has been a great deal of recent interest in extended compounds containing Ru3+and Ru4+in light of their range of unusual physical properties. Many of these properties are displayed in compounds with the perovskite and related structures. Here we report an array of structurally diverse hybrid ruthenium halide perovskites and related compounds: MA2Ru
X 6(X =Cl or Br), MA2M RuX6(M =Na, K or Ag;X =Cl or Br) and MA3Ru2X 9(X =Br) based upon the use of methylammonium (MA=CH3NH3+) on the perovskite A site. The compounds MA2RuX 6with Ru4+crystallize in the trigonal space groupand can be described as vacancy‐ordered double‐perovskites. The ordered compounds MA2 M RuX 6with M+and Ru3+crystallize in a structure related to BaNiO3with alternatingMX 6and RuX 6face‐shared octahedra forming linear chains in the trigonalspace group. The compound MA3Ru2Br9crystallizes in the orthorhombic Cmcm space group and displays pairs of face‐sharing octahedra forming isolated Ru2Br9moieties with very short Ru–Ru contacts of 2.789 Å. The structural details, including the role of hydrogen bonding and dimensionality, as well as the optical and magnetic properties of these compounds are described. The magnetic behavior of all three classes of compounds is influenced by spin–orbit coupling and their temperature‐dependent behavior has been compared with the predictions of the appropriate Kotani models.
