Volume 232, Issue 4

The autocorrelation method, proposed at first by [E. K. K. H. Salje, M. I. A. Carpenter, T. H. Malcherek, T. Boffa Ballaran, Eur. J. Min. 2000 , 12 , 503.] for the evaluation of FTIR data, is an efficient method the evaluation of data depending on external parameters like temperature, pressure, chemical composition etc. In this study a new single parameter value λ ′( ω ′) is proposed which is computational more efficient with a higher reproducibility than the Δcorr parameter proposed earlier. The method is additionally transferred from Fourier transform infrared (FTIR) spectroscopy to X-ray diffraction data. It is shown that the autocorrelation method has some beneficial properties compared to the often used Pearson’s r -value.

Moganite, which is monoclinic at ambient temperature, undergoes a displacive transition to an orthorhombic phase at ≈570 K. Whereas the monoclinic phase may be considered as α-quartz that is Brazil twinned along {1 0 1̅ 1} at the unit-cell scale (cell-twinning), the orthorhombic phase cannot be interpreted as a Brazil cell-twin of β-quartz, in contrast to statements made in the literature. The shape of the oxygen tetrahedra in monoclinic moganite has been determined more reliably by density functional theory (DFT) calculations than by experiment: the differences between the various experimental results for the shape of the oxygen tetrahedra at ambient temperature are typically ten times larger than the differences between the DFT results. The DFT calculations suggest that the oxygen tetrahedra in moganite are very close in shape to the oxygen tetrahedra in α-quartz. Among the three DFT calculations considered, the most convincing results for the bond angles in moganite are obtained for the DMol 3 code with functional PBE.

The crystal and molecular structures of {Zn[S 2 CN(CH 2 CH 2 OH) 2 ] 2 } 2 (pyrazine), ( 1 ), and its di-dioxane solvate, ( 2 ), are described. In each of these, the centrosymmetric, binuclear molecule features a five-coordinated, highly distorted square-pyramidal geometry based on a NS 4 donor set. The three-dimensional architectures in 1 and 2 are sustained by extensive networks of distinctive hydroxyl-O–H···O(hydroxyl) hydrogen bonding. The topology of the lattices are very different with that of 2 having a more regular appearance. The dioxane molecules reside in channels defined by the host molecules in 2 but, do not make many significant interactions with the host. The fact that 1 exhibits a significantly greater packing efficiency and a higher density suggests 1 is more stable than 2 . The retention of dioxane in crystals of 2 probably reflects its intimate involvement in nucleation and high boiling point, meaning it is retained during crystallisation. Hirshfeld surface analyses were conducted and confirm the importance of the hydroxyl-O–H···O(hydroxyl) hydrogen bonding but, also reveal the presence of other interactions, most notably C–H···π(chelate) interactions.

Weak intermolecular non-covalent H···Cl − interactions in the solid chelated palladium(II)-diaminocarbene complex cis -[PdCl(CNXyl){ C (NHXyl)=NHC 6 H 2 Me 2 N H 2 }]Cl ( 3 ; Xyl=2,6-Me 2 C 6 H 3 ) were studied by XRD followed by appropriate DFT calculations. The N–H···Cl contacts for both NH groups in the carbene moiety are different (N1–H···Cl2 3.5258(19), N2–H···Cl2 3.0797(17) Å). The DFT calculations and topological analysis of the electron density distribution within the formalism of Bader’s theory (QTAIM method) were performed for a model cluster of the carbene complex 3 . The theoretical data confirmed that the strength of intermolecular HB H···Cl − is different for two NH-protons of the carbene fragment. The influence of crystal packing effects on the formation of hydrogen bonds in the cluster of 3 is noticeable.

The traditional crystal packing study based on the analysis of geometrical characteristics of intermolecular interactions is found to be not informative enough. The application of quantum-chemical calculations for the evaluation of pairwise interaction energies between molecules allows to get much more information about supramolecular architecture. The staking interactions between π-systems of neighboring molecules form the building unit of the crystal packing in the absence of any strong interactions as well as in the presence of the N–H…O classical hydrogen bond. Unexpectedly the hydrogen bonds play the secondary role in the crystal packing formation as compared to stacking. Analysis of the total interaction energy of the basic molecule with all the molecules of its first coordination sphere and the pairwise interaction energies allows to evaluate the extent of crystal isotropy from point of view of interaction energies.

Crystal structures are reported of ( E )-2-(4-hydroxybenzylidene)-2,3-dihydro-1H-inden-1-one, 1 , ( E )-2-(4-dimethylaminobenzylidene)-2,3- dihydro-1H-inden-1-one, 2 , ( E )-2-(4-cyanobenzylidene)-2,3-dihydro-1H-inden-1-one, 3 , and monoclinic -( E )- 2-(3-nitrobenzylidene)-2,3-dihydro-1H-inden-1-one, monoclinic- 4 , all from data collected at 100 K and ( E )-2-(4-hydroxy-3,5-dimethylbenzylidene)-2,3-dihydro-1H-indan-1-one, 6 , from data collected at 299 K. An earlier triclinic form of 4 has been reported. Also reported herein are the Hirshfeld suface calculations for these five compounds, as well as that of 2-(4-methoxybenzylidene)-2,3-dihydro-1H-inden-1-one, 5 ,whose crystal structure has been previously reported. The three rings in each of the compounds, 1–4 and 6 , are essentially planar, including the five-membered ring containing a formally hydridized sp 3 atom. The molecules exhibit slight deviations from overall planarity as shown by the dihedral angles, >8.15(6)° between the 2,3-dihydro-1H-inden-1-one fragments and the phenyl fragments. The main intermolecular interactions in compounds 1 and are classical O–H···O1(carbonyl) hydrogen bonds. The carbonyl oxygen atom in compounds 1–4 are involved in non-classical C–H···O intermolecular hydrogen bonds. Intermolecular C–H---π interactions are present in 2 , 3 and 6 , while π···π are present in 2–4 and 6 . As noted in the structure determinations of these compounds, different π···π motifs are possible. The Hirshfeld surface calculations, while generally concurring with the intermolecular interactions indicated by PLATON analyses, also reveal significant interactions, which fall below the PLATON radar.