Band 225, Heft 1

Structural models are proposed for three composite compounds of chemical formula Ba 1 + x [(Na x Mn 1 – x )O 3 ] ( x approx. 2/7, 5/17 and 1/3) by single crystal X-ray diffraction; superspace formalism is used to obtain an unified description of the three phases. The modulation affecting Ba atoms can be easily designed but the competition “occupational/displacive” modulations relating to the Mn/Na metallic columns were particularly difficult to modelize. However, the large amplitude of the displacive modulation affecting the oxygen atoms (approx. ±0.7 Å) in comparison with that observed for related compounds (approx. ±0.3 Å) makes it a direct consequence of the Na + alkali insertion inside the trigonal prisms. Owing to this insertion, the Mn atoms exhibit, in the three phases, an “exotic” oxidation state of about +4.5. In addition, even if the sequence between face sharing MnO 6 octahedra and NaO 6 trigonal prisms can be analytically deduced from the x value, it is clear that the Na/Mn contrasts play in favour of its accurate determination through the XRD single crystal refinement.

The crystal structures of the neutral dmt compounds, 4,5-bis(methylthiolato)-1,2-dithiole-3-thione, ( 1 ), 4-benzoylthiolato-5-methylthiolato-1,2-dithiole-3-thione, ( 3 ) and 4-benzoylthiolato-5-benzylthiolato-1,2-dithiole-3-thione, ( 4 ), and the organic salt, 3,4,5-tris(methylthiolato)-1,2-dithiolium iodide ( 2 ) have been determined at 120 K. The packing of the molecules provides a variety of intermolecular, or interion, contacts. Notable features in 1 and 3 are the columns of overlapping dithiole rings. In both cases the columns are propagated in the direction of b and neighbouring rings are related to one another by the operation of crystallographic centres of symmetry. In 2 weak C–H · · · I (H · · · I = 3.0236 and 3.0166 Å) and C–H · · · S (H · · · S = 2.8660 Å) hydrogen-bonds, contacts with short I · · · S distances (3.433 and 3.370 Å) and a C–H · · · π contact, with the dithiole ring as acceptor (H · · · Cg = 2.946 Å), create zig-zag chains propagated in the direction of b which are further connected to form corrugated sheets parallel to (0 0 1) with methyl groups on their surfaces. Intermolecular O · · · S thiole contacts much shorter than the sum of the contact radii (3.32 Å) of oxygen and sulphur are present in 3 and 4 .The formation of 3 or 4 occurred regiospecifically from successive reactions of 4,5-bis(benzoylthiolato)-1,2-dithiole-3-thione with one equivalent of caesium hydroxide and RI (R = Me or PhCH 2 ).

The crystal structures of seven (pyrazinecarbonyl)hydrazone mono-substituted benzaldehyde derivatives, N 2 C 4 H 3 CONHN=CHC 6 H 4 X ( 1 : X = CN, OMe, OEt or NO 2 ) are reported. In all cases extensive intermolecular C–H · · · X (X = O, N or π-ring) hydrogen-bonding is present in which the nitrogen atom of p -CN and one oxygen atom of o -NO 2 substitutents act as hydrogen-bond acceptors and C–H bonds of the methyl groups of the p -OME and m -OEt substituents act as hydrogen-bond donors. While the m -OMe substituted compound exhibits only one-dimensional connectivity in the form of face to face ribbons of molecules two-dimensional layer connectivity is observed in all other cases. If, however, π · · · π interactions and, in the case of ( 1 : X = m -OEt) C–H · · · N and C–H · · · π-ring contacts, which arise between the layers as they are stacked, are taken into account three-dimensional connectivity is the norm for the layer structures except for that of ( 1 : X = o-Et).

Reaction of caesium 4-benzoyl-1,3-dithiole-2-thione-5-thiolate with iodine produced bis(4-benzoylthio-1,3-dithiole2-thione)-5,5′-disulfide, 6 . Compound, 6 has been obtained in two crystalline forms, on recrytsallisation from different organic solvent systems, designated 6X with space group P 2 1 / c and 6Y with space group P 2 1 . Two enantiomers of the molecule of 6 are observed but both polymorphs are racemates, 6X because of the centrosymmetric space group P 2 1 / c and 6Y because of the presence of both enantiomers in the bimolecular asymmetric unit. The polymorphs differ in molecular packing, the resulting intermolecular contacts and the disposition of the enantiomers. In 6X the enantiomers are found in separate stacks of face to face molecules which combine to create channels containing intermolecular C–H · · · O hydrogen-bonds along with π · · · π overlap of rings within and between the stacks. In 6Y the enantiomers are found in separate chains with intermolecular C–H · · · S hydrogen-bonds providing connnectivity within and between the chains and, overall, two-dimensional connectivity in well defined layers of molecules. Stacking of the layers creates stacks of face to face molecules similar to, but less regular than those observed in 6X , in which the enantiomers alternate along the length of the stack.

Hexaaqua copper(II) 3-(4-nitrophenyl)-2-phenylpropenoate (1) has been synthesized and characterized by single crystal X-ray diffraction analysis, spectral, elemental analysis and thermal study. The crystallographic analysis reveal that the crystal structure of the complex is corrugated three dimensional networks by hydrogen bonds and the π · · · π interactions, in which the coordination environment of the Cu(II) ion is distorted octahedral geometry, which is described by [4 + 2] coordination.

A novel terbium compound [Tb(pyrazinecarboxylic acid) 3 (H 2 O) 2 ] n · 6 n H 2 O ( 1 ) has been prepared via hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction. The crystal belongs to the orthorhombic, space group Pbca with a = 19.4112(7), b = 11.9345(4), c = 19.8507(7) Å, V = 4598.7(3) Å 3 , Z = 8, C 15 H 25 N 6 O 14 Tb, M r = 672.33, D c = 1.942 g/cm 3 , S = 1.052, μ (Mo K α ) = 3.159 mm –1 , F (000) = 2672, R = 0.0190 and wR = 0.0423. Compound 1 features an infinite 1-D chain-like structure with the terbium ions coordinating to six oxygen and three nitrogen atoms to give a distorted monocapped square antiprism. The [Tb(pyrazinecarboxylic acid) 3 (H 2 O) 2 ] n chains and the lattice water molecules link to each other through π–π interactions and hydrogen bonding interactions to construct a 3-D supramolecular network. Photoluminescent investigation reveals that the title compound displays strong emissions that are attributed to the characteristic emissions of 5 D 4 → 7 F J ( J = 3, 4, 5, 6) of Tb 3+ ions.