Study of the crystal structure of three synthetic insect pheromones using X-ray powder diffraction and DFT calculations

Abstract

Data of these crystal was collected by the use of. Stoe IPDS II diffractometer system. Crystal structure were solved by direct methods. Sır97 structure solution program was used. A refinement was carried out by full -matrix least -squares methods using Shelxl 97 refinement program. Fig 1:An ORTEP-III view of title compound [1] Ates¸, Ö ., Cesur, N., Güner, H., Uzun, M., Kiraz, M. & Kaya, D., Farmaco, 1995, 50, 361-364. [2] Günay, N. S., Çapan, G., Ulusoy, N., Ergenç, N., Öztürk, G. & Kaya, D., Farmaco, 1999, 54, 826-831 Complexes of para disubstituted and 4-monosubstituted biphenyl formed with 4,4'-dinitrobiphenyl (DNBP), demonstrate intense colours, from pale yellow to dark red, upon formation. These colours are dissimilar to the colour combination of the parent compounds. The focus of this study was to investigate the nature of these molecular donoracceptor interactions in the solid state, using spectroscopic techniques such as IR, Raman, UV-Vis, NMR and X-ray crystallography. Typical interactions observed in such molecular complexes include π-π interactions, hydrogen bonding, charge transfer and van der Waals interactions. There are no significant localized interactions between the guest molecule and the DNBP, except for the weak H-bond observed in the hydroxybiphenyl complex [1]. Complexes of DNBP, as acceptor, studied included a variety of mono-and disubstituted donors, such as dihalo, diamino, di-and monohydroxy groups. The crystal structures of these complexes showed retention of the non-planar conformation of DNBP with a dihedral angle of around 35 O . This conformation for DNBP has also been confirmed using density functional theory (Guassian) calculations that showed good agreement between the theoretically calculated and experimentally observed IR and Raman spectra in the solid state. In non-complexed DNBP, adjacent stacks of DNBP imolecules form a herring-bone pattern when viewed from above. On forming complexes with planar guest molecules, the stacks open out to form a checker-board pattern (as viewed from above) forming slots between the stacks which are occupied by the guest molecules. The packing is generally similar in all the complexes with planar guest molecules and is determined by the stacking of the DNBP molecules -with the substituted biphenyls, urea [2] or thiourea guest molecules slotting in between the stacks. It appears as if the packing of the complexes in the solid state is directed mainly by the similar packing of DNBP units in these complexes. Some of the molecular ratios for these complexes that vary, depending on the electronic properties of the donor molecules, were determined using NMR spectroscopy. The ratio of guest to DNBP depends on the size (length) of the guest molecule.[1]C.P.Brock, K.L.Haller Acta Crystallogr. Sect.C, C: Cryst. Struct Commun.,1984, 40, 1387 Pheromones are widely recognised as being extremely important among social insects as a means of communication [1]. They can be both volatile and non-volatile chemicals, which can act by simple detection in th...

Rectangular Chain Packing of Methyl-Branched Paraffins: Persistence of an Interchain Interaction and Forms of Disorder

“…This is the first systematic crystallographic study of chain packing in methyl-branched paraffins. Electron diffraction provides single crystal data in views down and onto the chain axes so that modeling of crystal structures can be placed on a firmer experimental basis than is possible with the use of overlapped powder diffraction information. − While structural models from two powder diffraction studies make geometrical sense, , a more recent suggestion of a “paper-clip” chain conformation in other branched paraffin crystal structures does not.…”

“…Samples of 17MeC37 and 19MeC37 were synthesized as described in a recent paper . (These compounds also serve a biological function as ant “recognition pheromones”. , ) DSC measurements of melting point are shown in Figures S-1 and S-2 (Supporting Information). These measurements were taken at a ramp rate of 10 °C/min using a TA Instruments 2920 calorimeter fitted with a liquid nitrogen cooling accessory.…”

“…For methyl-branching near the chain end in the 3-, 4-, and 5- positions, electron diffraction studies on rac -3-methyl tritriacontane (3MeC33), rac -3-methyl tetratriacontane (3MeC34), rac -4-methyl tetratriacontane (4MeC34), and rac -5-methyl tetratriacontane (5MeC34) indicated an intermediate form grown from the melt that does not appear to have a clearly defined lamellar interface. Recent powder X-ray studies of methyl paraffins with branches near the center (viz, 20-methyl nonatriacontane (20MeC39) and 18-methyl pentatriacontane (18MeC35)) , or nearer to the chain end (viz, enantiomorphically pure 9-methyl nonacosane (9MeC29) and 11-methyl heptacosane (11MeC27)) indicate the existence of at least two polymorphic forms. To our knowledge there is also no crystal structure reported for an isoparaffin, although iso -branched fatty acid crystal structures do exist. , Preliminary electron diffraction data from iso -hexacosane reveal a low temperature rectangular layer (i.e., untilted chain) form utilizing the orthorhombic perpendicular methylene subcell and a higher temperature rotator phase.…”