Band 227, Heft 12 -

The two complexes of Bis(4-aminosalicylato-O) bis( N,N -dimethylethylenediamine)Ni(II) with different colors, were synthesized by the reaction between sodium salt of 4-aminosalicylic acid (PAS-Na), Ni(NO 3 ) 2 · 6 H 2 O and N,N -dimethylethylenediamine in the ethanol water mixture. In the complexes, each Ni(II) atom was in a distorted octahedral environment, was coordinated apically by two 4-aminosalicylato-O atoms and equatorially by two the N,N -dimethylethylenediamine N atoms. The crystal structures (monoclinic, P 21/ n space group) of the complexes, comprise mononuclear {Ni(NH 2 OHC 6 H 3 COO) 2 · [NH 2 CH 2 CH 2 N(CH 3 ) 2 ] 2 } species and the Ni(II) atoms were located on a crystallographic inversion centre. The bond lengths and bond angles were nearly same with showing small difference as approximately 1% in coordination bonds lengths which caused the different colors for complexes. The N—H···O, C—H···O and C—H···π intermolecular interactions, extended the molecules through the three axes to form three dimensional network.

The stacking disorder in the hexagonal polymorph of tris(bicyclo[2.1.1]hexeno)benzene, C 18 H 18 , is explained by lattice-energy minimisations. The compound crystallises in layers with P (-6)2 m layer-group symmetry. Each layer can be placed in one of three possible positions. Possible stacking sequences were derived from order-disorder (OD) theory and by a combinatorial approach. The resulting periodic model structures were optimised by lattice-energy minimisations. The calculations show that eclipsed arrangements of layers (sequence e.g . ABA) are energetically less favourable than non-eclipsed ones (sequence e.g . ABC). The reason was found in the deviation from P (-6)2 m symmetry. Molecules in eclipsed layers are almost parallel to the layer plane, whereas molecules in non-eclipsed layers are inclined to it by about 3° leading to a more efficient packing. The influence of the next-nearest layers was found to be not a direct one, but mediated by the distortion of the layers between them. Using Boltzmann statistics, the stacking probabilities for all four-layer sequences were calculated. The results match well with the probabilities derived from the diffuse scattering by Bürgi et al. (2005) (Z. Kristallogr. 220, 1066–1075). The lattice-energy minimisations allowed to determine the actual local structures in all individual layers including packing effects like rotation of molecules, lateral shifts, and to calculate the stacking layer thickness, depending on the actual layer sequences. The diffraction pattern, calculated from a lattice-energy optimised structure with 54 layers, is similar to the experimental one, and even approximates the diffuse scattering.

Crystals of sarcosine sarcosinium nitrate (2 Sar · HNO 3 ) have been grown and characterized at 296 and 150 K by single crystal XRD and vibrational spectroscopy. The species was found to be triclinic (space group P -1, a = 5.320(1) Å, b = 6.578(1) Å, c = 15.957(2) Å, α = 95.448(6)°, β = 95.944(6)°, γ = 93.410(6)°, V = 551.6(1) Å 3 , and Z = 2 at 296 K), with a dimeric sarcosine ... sarcosinium cation and a nitrate anion in the asymmetric unit. A very strong hydrogen bond connects the molecules within the dimer. In addition, the tensor of thermal expansion was determined for the temperature range of 200 to 290 K. A strong anisotropy was detected, with thermal expansion along the c -axis approximately 14 times as strong as along the a -axis.

Co-crystals formed between anthranilic acid and each of N , N ′-bis(pyridin-2-ylmethyl)oxalamide ( 1 ) and N , N ′-bis(pyridin-3-ylmethyl)oxalamide ( 2 ) have been formed from solutions containing 2:1 stoichiometric quantities of the reagents. In isomeric 1 and 2 , the oxaläamide groups have both amide and pyridyl groups capable for forming hydrogen bonding interactions with the äcomponents of anthranilic acid. However, it is the {C(=O)OH···N(py)} heterosynthon that persists in both crystal structures pointing to the robustness of this synthon when both carboxylic acids and pyridyl groups are found in co-crystals. In 1 , amine-H···O (oxalamide) and amide-H···N(amine) hydrogen bonds lead to layers that stack along the c -axis via C—H···O (carbonyl) interactions. In 2 , the amine-H···O(oxalamide) hydrogen bonds lead to layers which are connected into a three-dimensional architecture by amide-N—H···O2 (carbonyl) interactions.

Structure and properties of a series of mononuclear manganese(II) complexes with phenyl 2-pyridyl ketoxime (ppkoH) as ligand are presented. [Mn(ClC 6 H 4 COO) 2 (ppkoH) 2 ] · 0.5 CH 3 OH and [Mn(ClC 6 H 4 COO) 2 (ppkoH) 2 ] ( 1 and 2 ) are isolated from the same reaction system and differ by disordered solvent content and conformation of the complex molecules. [MnCl 2 (ppkoH) 2 ] · 0.02 C 2 H 5 OH ( 3 ) was obtained in order to modify the central Mn 2+ ion coordination sphere with respect to 1 / 2 . Strong intramolecular hydrogen bonds of the O–H···O and O–H···Cl type are present in 1 / 2 and 3 , respectively. Moreover, weak C–H···O ( 1 – 3 ), C–H···Cl ( 3 ), π···π ( 1 – 2 ) and Cl···π ( 2 ) contacts can be found. The complexes display well-resolved Q-band EPR spectra and may serve as model compounds for further studies.

The crystal chemistry of many AB 2 O 6 compounds is summarized in family trees comparing the crystal symmetry of several structures in group-subgroup relations. In this second part of a series the largest family derived from a hexagonally close packed arrangement of anions is described. On reducing the symmetry, different choices of octahedral sites for A and B cations and voids lead to four branches – the Rosiaite-, the ZnTa 2 O 6 -, the columbite- and the rutile-branch. We trace the reasons for the specific distribution patterns of the cations in the individual compounds by comparing long range contributions, i.e. the Madelung Part of Lattice Energy (MAPLE), and local effects represented by bond valence calculations according to I. D. Brown. Long range effects largely determine the choice of sites in the respective space groups, however, small local adjustments play a decisive role for the stability of a specific structural modification. Such mechanisms ultimately impose how the structure of an individual compound deviates from an ideally packed arrangement. We discuss the difference between the ideal structures and the real examples given in the family tree by defining a sort of deformation tensor and a measure of similarity, and we describe and depict the anisotropic deformation by a strain tensor.

Crystals of the 2.5- and 6-hydrates of K 2 HAsO 4 were grown from H 3 AsO 4 solutions which were neutralized with two equivalents of aqueous KOH. The crystal structures were determined by X-ray diffraction at 100 K. K 2 HAsO 4 · 2.5H 2 O [ P 2 1 , Z = 8, a = 7.1607(3) Å, b = 18.1352(8) Å, c = 13.8156(5) Å, β = 125.153(3)°, R [ F 2 > 3 σ ( F 2 )] = 0.040, 10500 F data, 226 parameters] is a polytypic structure. The major polytype is of a maximum degree of order (MDO) and makes up ≈87% of the investigated crystals. Reflections pertaining to the second MDO polytype and disordered domains resulting in diffuse scattering were also observed. Two equivalent descriptions according to order/disorder (OD) theory are given in terms of layers of two kinds and of layers of one kind. Whereas the former emphasizes a local symmetry increase compared to the symmetry of the polytypes, the latter is useful for the straightforward determination of the MDO polytypes. The layer choice is ambiguous because parts of the structure belong to more than two maximum equivalence regions (MERs). The 2.5-hydrate as well as the higher hydrated K 2 HAsO 4 · 6 H 2 O [ Cc , Z = 4, a = 9.1788(2) Å, b = 9.4179(3) Å, c = 12.5935(5) Å, β = 93.7840(10)°, R [ F 2 > 3 σ ( F 2 )] = 0.013, 4812 F data, 169 parameters] are composed of K + cations with highly irregular coordination environments defined by O atoms from [AsO 3 (OH)] 2– anions and water molecules. A complex hydrogen-bonded network between the constituents is observed for both structures.

Structure of the Nd 5 Mo 3 O 16 single crystal grown in the Nd 2 O 3 –MoO 3 system was studied using the X-rays diffraction technique at 293 K and 110 K temperatures. The unit-cell values were always cubic relating to that of CaF 2 fluorite as a ≈ 2 a f ( a f = 5.5 Å). The structure was solved within the Pn -3 n symmetry group. It was found that the Nd 5 Mo 3 O 16 compound has a fluorite-like structure with all atoms disordered. An indirect confirmation for the violation of translational periodicity in the distribution of Mo and Nd atoms was obtained. The possible oxygen diffusion paths were analyzed using the one-particle potentials of the oxygen atoms. The ionic conductivity of Nd 5 Mo 3 O 16 compound is associated with the disordering of the oxygen atoms in several positions, and their deficiency in comparison with the initial fluorite.