Crystal Engineering最新文献

Reaction in aqueous medium of KReO₄ in methanolic solution of RaaiCH₂Ph (1-benzyl-2-(arylazo)imidazole) (1) in the presence of perchloric acid has isolated brown products of {[1-benzyl-2-(arylazo)imidazolium][ReO₄⁻]H₂O}_n, 2. The structural confirmation has been carried out by the single crystal X-ray diffraction study of {[1-benzyl-2-(phenylazo)imidazolium][ReO₄⁻]H₂O}, 2a. The molecules are polymerized via hydrogen bonding and form cross-linked network.

The X-ray structures of four co-crystals of 4,4′-bipyridyl (Bipy) with two dicarboxylic acids and two tricarboxylic acids are described. A coupling (I) involving O–H⋯N and C–H⋯O interactions, previously seen in co-crystals of carboxylic acids with other heterocyclic bases, is again shown to be involved in the formation of supramolecular structures. Bipy with isophthalic acid, 1,4-naphthalenedicarboxylic acid and 1,3,5-cyclohexane-tricarboxylic acid forms 1:1 complexes. Tapes of acid:base components are formed via coupling I; these tapes extend to form supramolecular sheets via O–H⋯O and/or C–H⋯O interactions. With tricarballylic acid, a co-crystal with stoichiometry 3:2 (acid:base) is generated, with a four-acid-four-base cyclic motif (involving coupling I) as the elementary supramolecular unit. Two previously reported co-crystals of Bipy with trimesic acid and 2,5-di-n-hexylterephthalic acid are also discussed, as well as a CSD search for coupling I in mono-and poly-carboxylic acid/Bipy complexes.

Remarkable differences have been observed between the host–guest interaction modes in two closely related crystalline inclusion compounds [1·MeOH (1:1) and 1·EtOH(1:1)] of the same carboxylic host (1). The minor modification of the guest structure crucially affected the hydrogen bonding recognition pattern between given complementary groups, which demonstrates the sensitive balance of intermolecular interaction modes that must be controlled for successful crystal engineering and design of supramolecular compounds.

The solid-state packing arrays of eight 4-sulfur substituted 2-aminopyrimidines have been examined and the occurrence of N–H—S hydrogen-bonding associations in those structures discussed. The eight compounds were 2,5-diamino-4-mercapto-6-methylpyrimidine 1, 2-amino-4,6-bis(phenylthio)pyrimidine 2, 2-amino-4,6-bis(4-chlorophenylthio)pyrimidine 3, 2-amino-4,6-bis(4-methylphenylthio)pyrimidine 4, 5 (two polymorphs), 2-amino-4-chloro-6-(4-fluorophenylthio)pyrimidine 6, 2-amino-4-(4-chlorophenylthio)-6-morpholinopyrimidine 7, 2-amino-4-(4-(2,3-dimethylphenyl)piperizino)-6-phenylthiopyrimidine 8, and 2-amino-4-(4-(2-ethoxyphenyl)piperizino)-6-(4-chlorophenylthio)pyrimidine 9. The single-crystal x-ray structures of 1 – 3 have been previously reported while the structures of 4 – 9 are presented in this paper. All packing motifs exhibit characteristic R₂²(8) hydrogen-bonded 2-aminopyrimidine dimers, to varying degrees of polymerisation, whereas compounds 1 – 5 and 7 include N–H—S associations, the majority of which are three-center associations with an included N–H—N interaction.

The crystallization process during annealing at 100°C of thin films of iso-propyl-calix-[6]-arene has been studied using topographic and lateral force imaging of contact mode scanning probe microscopy. The crystallization proceeds from sub-micron crystallites with mass migration to form large crystalline wall-like structures several microns in width and over 100 μm in length. During the annealing these wall-like structures compact with a concomitant decrease in width. Lateral force imaging shows the presence of moiré-pattern like zones of high and low friction forces.

We report here on the formation of co-crystals of 2-pyridone and several long chain dicarboxylic acids HO₂C(CH₂)_nCO₂H with n an odd number. Supramolecular tapes, illustrating several hydrogen bond motifs, were observed. Co-crystals with malonic acid (n=1) crystallise in the space group P2/n, with a=19.213, b=4.031, c=19.508, β=114.67°; glutaric acid (n=3) in P-1, with a=5.437, b=9.592, c=11.797, α=66.50°, β=81.64°, γ=83.00°; pimelic acid (n=5) in C2/c, with a=19.828, b=5.135, c=17.401, β=102.98°; and azelaic acid (n=7) in P2₁/c, with a=16.644, b=5.036, c=18.213, β=103.09°. Tape compositions of both 1:1 acid:base and 1:2 acid:base were obtained suggesting that tape stochiometry is independent of the number of constituent carbon atoms in the acid backbone. The results also suggest that the 2-pyridone dimer may in certain cases act as a supramolecular analogue of phenazine.

This paper discusses the growth and properties of Triglycine Sulphate Crystals (TGS) and with L-Asparagine. Doped single crystal was grown by slow-cooling solution growth technique. TGS crystals with 10 wt% of L-Asparagine exhibited prominent morphological changes in the (101) and (001) planes. Lattice parameter values were determined by powder X-ray diffraction analysis. Incorporation of L-Asparagine in TGS crystals has been qualitatively estimated and confirmed by Fourier Transform Infrared (FTIR) spectra. Micro hardness studies also performed for the pure and doped crystals. A morphology diagram is given.

Co-crystals of the 1:1 molecular complexes formed between both octafluoronaphthalene and hexafluorobenzene with acenaphthene have been prepared and analysed by X-ray diffraction, which showed them to be composed of infinite stacks of alternating molecules, as is the case for other arene-perfluoroarene complexes.