In contrast to the regular morphologies displayed by synthetic single crystals, biogenic single crystals frequently exhibit unusual forms and curved surfaces. Such controlled mineralization in biology occurs within restricted volumes constructed for this purpose and there is significant evidence that some crystals with complex morphologies may form via an amorphous precursor phase. We here investigate morphological control of single crystals, using these biological mechanisms as inspiration. Calcite was precipitated within the cylindrical pores of track‐etch membranes via an amorphous calcium carbonate (ACC) precursor phase. Perfect replication of the pore channel to yield rod‐shaped single crystals of calcite was only achieved when the ACC precursor particles entirely filled the pore channels prior to crystallization, a process dependent on the pore diameter. Misshapen particles were formed in all pore diameters in the absence of an ACC phase. This system provides an ideal opportunity to carry out a systematic study into the effect of pore diameter, and the presence of an ACC precursor phase on crystal growth.

A breathing 2-fold interpenetrated microporous metal-organic framework was synthesized with a flexible tetrahedral organic linker and Zn(2) clusters that sorb CO(2) preferably over N(2) and H(2).

The structure of N,NA,NB-tris(2-methoxyethyl)benzene-1,3,5-tricarboxamide consists of aryl rings self-assembled using a novel conjunction of organizational motifs into a pstack surrounded by a triple helical network of hydrogen bonds, in a manner suggestive of a new mode of organization for some columnar liquid crystals.

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Hydrolysis of the DMF or DEF solvent influences the nature of the product observed in the reaction between zinc(II) nitrate and 1,4-benzenedicarboxylic acid, with dialkylammonium cations able to template the formation of anionic networks.Coordination networks, or metal-organic frameworks (MOFs) are currently attracting a tremendous amount of interest. 1,2 This is largely a result of their potential for porosity, and the implications of this in applications such as gas storage. 3,4 Some of the most spectacular results in this area have arisen from the Yaghi group. 5-8 They have reported a number of interesting structures, and impressive adsorption properties for compounds such as [Zn 4 (m 4 -O)(m-bdc) 3 ] (bdc 22 5 1,4-benzenedicarboxylate, terephthalate), which they refer to as MOF-5. Although the effectiveness of this material in hydrogen absorption has recently been queried, 9 MOF-5 and related compounds are currently receiving considerable attention within the porous material field. [10][11][12] From a chemical perspective, the zinc-bdc 22 system is far from straightforward. [Zn 4 (m 4 -O)(m-bdc) 3 ] can be prepared from Zn(NO 3 ) 2 ?6H 2 O and H 2 bdc under solvothermal conditions 13 or at room temperature. 14 In addition to [Zn 4 (m 4 -O)(m-bdc) 3 ], a number of other compounds have been prepared from Zn(NO 3 ) 2 ?6H 2 O and H 2 bdc. [15][16][17] In this paper we report how the presence of water in the solvent is crucial in influencing the product from the reaction between Zn(NO 3 ) 2 ?6H 2 O and 1,4-benzenedicarboxylic acid in either DMF or DEF.When Zn(NO 3 ) 2 ?6H 2 O and H 2 bdc were heated in fresh DEF at 95 uC for 3 h, small colourless crystals precipitated from the solution. These were shown to be [Zn 4 (m 4 -O)(m-bdc) 3 ]?3DEF 1 (i.e. solvated MOF-5) by a combination of X-ray single-crystal and powder diffraction experiments, the latter of which produce identical results to those simulated from the previously reported crystal structure. 5 When Zn(NO 3 ) 2 ?6H 2 O and H 2 bdc were heated under the same conditions, in DEF that had been in the laboratory for several weeks, small colourless crystals were again isolated. However, in this case, the product was shown by a combination of X-ray single-crystal and powder diffraction experiments to be exclusively the previously unreported compound [NH 2 Et 2 ] 2 [Zn 3 (mbdc) 4 ]?2.5DEF 2.The structure of 2 is based on bdc 22 anions bridging between linear Zn 3 (m-O 2 CR) 6 secondary building units (SBUs). The central Zn(1) atom has a distorted octahedral geometry, and is k 1 -coordinated to six carboxylates. The two symmetry-related peripheral Zn(2) atoms exhibit distorted tetrahedral geometry, and are each k 1 -coordinated to four carboxylates. Three of these groups bridge to Zn(1), though one adopts the m-k 1 O,k 1 Ocoordination mode rather than the more common m-k 1 O,k 1 O9-mode employed by the other two. The six bridging carboxylates radiate from the Zn 3 (m-O 2 CR) 6 SBU at approximately 60u angles, leading to the construction of a layer structure with tri...

Explosives under pressurethe crystal structure of γ-RDX as determined by high-pressure X-ray and neutron di raction COMMUNICATION Swift et al. Structure of a lead urate complex and its e ect on the nucleation of monosodium urate monohydrate CrystEngComm www.rsc.org/crystengcomm

The structural response of the nootropic drug piracetam (2-oxo-pyrrolidineacetamide) to both direct compression and high-pressure recrystallization from aqueous solution is reported. Crystals obtained by these methods have been characterized in situ by single-crystal X-ray diffraction. Compression of form II between pressures of 0.45-0.70 GPa caused a reversible, singlecrystal to single-crystal transition to give a new polymorph, form V. Crystallization from a dilute aqueous solution of piracetam at a pressure of 0.6 GPa via crystallization of high-pressure ice-VI resulted in the formation of a previously unreported dihydrate. The molecular packing arrangements of these new structures are compared with the known polymorphs and hydrates of piracetam. This study highlights how the systematic variation of pressure is a powerful method for the exploration of polymorphism and solvate formation and has the potential to add a further dimension to polymorph screening of pharmaceuticals.

Crystal engineering of nanoporous structures has not yet exploited the heme motif so widely found in proteins. Here, we report that a derivative of iron phthalocyanine, a close analog of heme, forms millimeter-scale molecular crystals that contain large interconnected voids (8 cubic nanometers), defined by a cubic assembly of six phthalocyanines. Rapid ligand exchange is achieved within these phthalocyanine nanoporous crystals by single-crystal-to-single-crystal (SCSC) transformations. Differentiation of the binding sites, similar to that which occurs in hemoproteins, is achieved so that monodentate ligands add preferentially to the axial binding site within the cubic assembly, whereas bidentate ligands selectively bind to the opposite axial site to link the cubic assemblies. These bidentate ligands act as molecular wall ties to prevent the collapse of the molecular crystal during the removal of solvent. The resulting crystals possess high surface areas (850 to 1000 square meters per gram) and bind N2 at the equivalent of the heme distal site through a SCSC process characterized by x-ray crystallography.