Band 228, Heft 5 -

The review surveys the crystal chemistry of inorganic compounds belonging to the structure type of clathrate-I. The compounds of this family exhibit an unexpected variety of both chemical composition and features of the crystal structure. The basic crystal structure of clathrate-I and different variants of its modification, such as siting, position splitting, and superstructure formation including transformation to semiclathrates, are considered in terms of the group-subgroup relationship.

⊙15 mm Single crystals of potassium lead chloride (KPb 2 Cl 5 ) have been grown by a novel modified Bridgman method under protect of N 2 and CCl 4 with a pressure control system. It could make vacuum or protect atmosphere according to the need of raw materials composition and crystals growth. So the process of preparation of crystal would be simplified. Measurements of the transmission of crystal in the mid-infrared were also made.

A crystal structure determination confirmed that the product from 7-chloroquinilin-4-ylhydrazine and 4-methoxycinnanamic acid had been isolated from MeOCH 2 CH 2 OH solution as [( E )- N′- 7-chloro-4-(4-methoxycinnamolyhydrazinyl)quinoline, 1 . In contrast, recrystallization of the 2-MeO derivative, 2 , from the same solvent, produced a 1 : 1 co-crystalline mixture of two tautomers, namely ( E )- N′- 7-chloro-4-(2-methoxycinnaämolyhydrazinyl)quinoline and 7-chloro-4(1 H)quinolinone 3-(2-methoxycinnamoyl)hydrazone, molecules A and B , respectively. Molecules 1 and 2A have “ L ”-shapes and, in general, have very similar conformations, which differ from that of 2B , mainly arising from the rotation about the (O)C—N(N) bond within the linker unit between the quinolone and methoxyphenyl rings. In both 1 and 2 , the 3-dimensional supramolecular arrangements involve strong N—H…N, N—H…O, C—H…O and C—H…π hydrogen bonds, while additionally in 2 , there are π…π, C—Cl…π and C—H…Cl intermolecular interactions.

Single crystal data on eight new hexafluorosilicate salts of amino acids are presented in this work. This includes crystal and molecular structures of the following salts: 2 β-Ala · H 2 SiF 6 (I), 2 Bet · H 2 SiF 6 (II), 2 L -Orn · H 2 SiF 6 (III), 2 L -Ser · H 2 SiF 6 (IV), 2 L -Leu · H 2 SiF 6 · 2 H 2 O (V), 2 L -Ile · H 2 SiF 6 · 2 H 2 O (VI), 2 L -Met · H 2 SiF 6 · H 2 O (VII), and 2 L -Asp · H 2 SiF 6 · 2 H 2 O (VIII). In all these crystals, the SiF 6 -anion is ordered, except for (III), where disorder of the fluorine atoms occurs. An analysis of previously published data on amino acid hexafluorosilicates showed that the amount of hydrogen bonding towards the SiF 6 -anion is an indication of disorder – we found that all structures with 0.6 or less hydrogen bonds per fluorine atom have disorder.

Various features of amino acids have been so far associated with crystallization propensity of proteins. The majority of features generally represents a certain aspect of individual amino acid, for example, molecular weight of an amino acid. Meanwhile, a small portion of features, which represents a certain aspect of a whole protein, is also associated with crystallization propensity of proteins, such as protein length. Clearly, the features of individual amino acids distinguish themselves from the features of a whole protein. Therefore it would be more rationale to use the features, which combine both features of individual amino acids and a whole protein, to associate crystallization propensity of proteins, because the features of individual amino acids are not subject to amino acids‘ positions in a protein, for instance. In this study, each of three combined features of individual amino acids and a whole protein are associated with crystallization propensity of proteins from Cytophaga Hutchinsonii through logistic regression and neural network, and each of 535 features of individual amino acids is also associated with crystallization propensity of the proteins to serve as benchmark. The results show that the combined features have a good relationship with crystallization propensity of proteins from Cytophaga Hutchinsonii . This study provides the information that the combined features can be used for predicting crystallization propensity of protein.

The crystal structure of 2-(4-methylphenyl)-2-oxo-1-(phenyliodonio)-1-(triphenylarsonio)ethanid tetrafluoroborate, C 33 H 27 AsIO+BF 4 – , was solved and refined from laboratory X-ray powder diffraction data in combination with a DFT calculation (Co K α1 , a =24.427(2) Å, b = 13.3412(18) Å, c =22.399(2) Å, β = 119.49(2)°, S.G. C2/c , R p / R wp = 0.030/0.039). The main features of the C 33 H 27 AsIO+BF 4 – structure are similar to those reported previously for arsenium and phosphorous organic compounds. The distinctive features are short I … O and I … F (2.743(19) and 2.916(17) Å, respectively) intermolecular contacts, also observed previously in the same type of compound, refined from single crystal data.