Crystal Engineering最新文献

A survey of crystal structures of organic molecules shows that there is strong evidence of stacking of aromatic rings and aliphatic rings and this packing motif may provide a fundamental stabilising interaction in crystal structure formation. Here this is probed by mainly focussing on interaction of six-membered aromatic groups with six-membered heterocyclic molecules, especially sugars.

Crystallisation of 1,6-bis(4-pyridyl)hexane (Py₂C₆H₁₂) with copper nitrate gives two different phases. Phase 1 of composition [Cu(Py₂C₆H₁₂)₃(NO₃)₂]·2[Cu(Py₂C₆H₁₂)₂(H₂O)(NO₃)]·2(NO₃)·EtOH consists of two different infinite chains in a 1:2 ratio that are interlocked. Hydrogen bonds link chains I to II and chains II to II. In contrast phase 2 of composition [Cu₂(Py₂C₆H₁₂)₄(H₂O)₂]·(NO₃)₄·(Py₂C₆H₁₂)·(EtOH)·2(H₂O) is based upon an infinite 3D framework. It consists of four interpenetrating 3D networks that are crystallographically equivalent.

The synthesis and crystal structures of {[M(4,4′-bipyridine)₂(NO₃)₂]⋅2p-nitroaniline}_n, M=Co, 1, Ni, 2, Zn, 3, are described. 1, 2 and 3 crystallize in the form of compounds that can be described as interpenetrating covalent and noncovalent networks. Analysis of the crystal packing in these compounds reveals that the p-nitroaniline molecules form a noncovalent network that is complementary from a topological perspective with [M(4,4′-bipyridine)₂(NO₃)₂] networks, which exist as square grids. These structures are interpreted in the broader perspective of crystal engineering strategies and development of new hybrid materials.

The influence of the solvent on the crystallization of N²-((S)-1-ethoxycarbonyl-3-phenylpropyl) -N⁶-trifluoroacetyl-L-lysyl-L-proline (Lisinopril ester) was investigated. It was found that Lisinopril ester could be crystallized from about 20 kinds of solvent, all of which had some similarities in molecular structure. The amount of the solvent inside the obtained crystals was approximately 1 to 100 mol% per Lisinopril ester and it was influenced by the molecular form or the bulkiness of the solvent molecule and the kind of substituents present therein. It was recognized that the presence of a suitable substituent in the solvent molecule is essential for crystallization and that there was a possibility that the substituent in the solvent molecule interacts with, at a minimum, the trifluoroacetylamino group in a Lisinopril ester molecule. It is suggested that the above crystallization of Lisinopril ester is a kind of adductive crystallization wherein the host is Lisinopril ester and the guest is the crystallizing solvent itself.

Crystallisation of flexible dipyridyl ligands with Cd(NO₃)₂·4H₂O, Cd(ClO₄)₂·xH₂O or Cd(NO₃)₂·4H₂O and KSCN gives co-ordination networks of composition [Cd(ClO₄)₂(Py₂C₃H₆)₂(H₂O)₂]·Py₂C₃H₆ 1 (Py₂C₃H₆ =1,3-bis(4-pyridyl)propane); [Cd(ClO₄)₂(Py₂C₂H₄)₃] 2 (Py₂C₂H₄ =1,2-bis(4-pyridyl)ethane); [Cd(NCS)₂(Py₂C₃H₆)] 3; [Cd₂(NO₃)₄(o-C₆H₄(CH₂CH₂4-Py)₂)₄] 4 (o-C₆H₄(CH₂CH₂Py)₂ =1,2-bis[2-(4-pyridyl)ethyl] benzene and [Cd(NO₃)₂(PyCH₂CH₂CH=CHCH₂CH₂Py)₃] 5 (PyCH₂CH₂CH=CHCH₂CH₂Py =1,6-bis(4-pyridyl)hex-3-ene). The compounds were characterised by X-ray single crystal diffraction studies which revealed the presence of different polymeric motifs. Structures 1 and 5 consist of 1-D polymeric chains, structure 4 consists of a 2-D polymeric network and structure 3 is a 3-D polymeric network. None of these exhibit lattice interpenetration. However structure 2 consists of three identical but independent interpenetrating 3-D lattice networks.

Influence of alkalinity (OH^-/SiO₂) on particle size distribution and crystalline structure in synthesis of zeolite beta at a short crystallization period (60 h) has been studied. The results indicate that the highest crystallinity of synthetic zeolite beta at alkalinity of 0.24, 0.35 occurs when Al₂O₃·H₂O and NaAlO₂ are respectively used as aluminium sources. At an alkalinity higher than 0.39, zeolite beta can not be obtained when Al₂O₃·H₂O is used as aluminium source. The difference of particle sizes between zeolite beta synthesized from gels of different alkalinity is 0.7–0.8 μm. The widest particle size distribution of zeolite beta synthesized occurs when the alkalinity is 0.23–0.24. Along with the increase of the alkalinity, zeolite beta synthesized changes as follows: vibration peak of 1071 cm⁻¹ by IR moves to a higher position, the framework Si/Al ratio determined by ²⁹Si MAS NMR first increases gradually and then decreases, but the change of OhAl/TdAl ratio determined by ²⁷Al MAS NMR is contrary to that of the framework of the Si/Al ratio. In addition, the Si(O⁻) site existing in the TEA-β is confirmed by NMR, and the mechanism of alkalinity influencing crystallization is discussed.

The crystal structures of four p-phenyl-substituted cis-9,10-diphenyl-9,10-dihydroanthracene-9,10-diols, carrying chloro- (1), bromo- (2), iodo- (3) and methyl substituents (4), respectively (with 2 being a previously described compound), have been studied in order to compare the effects of these substituents on the crystalline architecture. Ordinary O–H···O hydrogen bonds govern the packing of the methyl-substituted molecules in 4, whereas interhalogen interactions in competition with conventional hydrogen bonds direct the crystalline arrangement of the halogenated homologues 1–3, yielding somewhat lower symmetry and lower packing coefficient for the latter crystals. All short (Cl···Cl<3.49, Br···Br<3.46, I···I<3.86 Å) interhalogen interactions are symmetrical type-I connections with more or less “head-on” directions, where increasing size of the connected halogens seems to increase a tendency towards deviation from the ideal head-on geometry. Substitution of methyl in 4 for chlorine in 1 changed the crystal packing significantly, whereas the chloro-substituted derivative (1) was found to form a crystal isostructural with its bromo-substituted analogue (2). Two of the short interchloro distances in 1 were found to be slightly longer than the corresponding ones in the bromo analogue. This is rather unusual, although extensive inspection of the literature and the Cambridge Structural Database yielded five more examples of pairs of organic chloro and bromo analogues, forming isostructural crystals with direct Cl···Cl contact distances equal to or slightly longer than the corresponding Br···Br distances.

The nature of a new zeolite overgrowth has been characterized. Two overgrown samples were studied. Each sample was made up of the phases faujasite and EMT. By Rietveld refinement of the powder patterns the structure of both phases including the distribution of cations in the overgrowth was determined as well as the weight fractions of the phases in both samples. The growth of FAU crystals on the surface of EMT crystals is epitactic, as shown by HRSEM images. The epitaxial relation is [111]_FAU//[001]_EMT, (-110)_FAU//(110)_EMT. The true atomic interfacial model of the interface between faujasite and EMT is still subject of further studies.