Formatted abstract

Using Xray diffraction techniques, the crystal and molecular structures of four analogues of DDT, one cyclodiene insecticide, and two metal complexes have been determined. The DDT analogue structures have been analysed, in conjunction with several reported by other workers, in order to assess the effect of various parameters of the molecule on activity. The results indicate acceptable ranges of various parameters consistent with insecticidal activity, and in addition a quadratic relationship has been found between log_{10}(LD_{50}) and the dihedral angle between the planes of the two phenyl rings.
1,1dichloro2,2bis(pchlorophenyl)ethane (DDD) DDD crystallizes in the monoclinic space group C2/c with a = 2011.4(3), b = 769.2(1), c = 1908.6(3) pm, β = 105.42(1)°, and Z = 8. The structure was determined from threedimensional diffractometer data using direct methods, and was refined by fullmatrix least squares to a conventional R of .068 for 877 observed reflections It is an active insecticide with a similar conformation to DDT.
bis(pchlorophenyl)acetic acid (DDA) DDA crystallizes in the monoclinic space group P2_{1}/c, with a = 1411.3(2), b = 612.3(1), c = 1600.5(2) pm, β = 111.51(1)°, and Z = 4. Direct methods were used to solve the structure from threedimensional diffractometer data, and fullmatrix least squares refinement reduced the conventional R value to .079 for 1600 observed reflections. Although it has similar conformational angles to DDT the compound is nonactive because of the apex group dimensions. In the crystal it forms a dimer with its centre at a centre of symmetry and a hydrogen bond of 200 pm.
1,1dichloro2,2bis(pchlorophenyl)ethylene (DDE) DDE crystallizes in the monoclinic space group P2_{1}/c with a = 921.9(1), b = 3549.6(5), c = 943.8(1) pm, β = 114.70(1)°, and Z = 8 (two independent molecules in the asymmetric unit). The structure was solved by direct methods from threedimensional diffractometer data and refined by fullmatrix least squares to a conventional R of .049 for the 1751 observed reflections. The low insecticidal activity of this compound may be caused by the low dihedral angle between the phenyl rings (97,3°) or by the unsuitable dimensions of the apex group.
4,4'dichlorobenzophenone (DBP) DBF crystallizes in the monoclinic space group C2/c, with a = 2516.1(11), b = 612.8(3), c = 758.6(3) pm, β = 102.05(3)°, and Z = 4. Using threedimensional diffractometer data the structure was solved by direct methods. Fullmatrix least squares refinement gave a final conventional R of .075 for the 726 observed reflections. The molecule has a crystallographically implied twofold axis. Its inactivity can be explained by the small apex group and the very low dihedral angle between the phenyls (50.7°).
1,4,5,6,7,8,8heptachloro3a,4,7,7atetrahydro4,7methanoindene (Heptachlor) Heptachlor crystallizes in the orthorhombic space group Pbca with a = 1580.0(1), b = 1421.5(1), c = 1226.6(1) pm and Z = 8. The structure was determined by direct methods using threedimensional diffractometer data, and refined by fullmatrix least squares to a final conventional R of .047 based on the 1239 observed reflections. This compound is an active insecticide of the cyclodiene series. The dimensions of the hexachloronorbornene part of the molecule are virtually identical to those reported in the structures of Endrin, Aldrin, and Dieldrin.
Dihydrogen Ethylenediaminetetraacetatostannate(II) H_{2}Sn(edta) crystallizes in the orthorhombic space group Pbca with a = 659.1(1), b = 1303.1(2), c = 3221.6(6) pm and Z = 8, The structure was determined from threedimensional diffractometer data using Patterson and Fourier techniques, and refined by fullmatrix least squares to a conventional R of .053 for the 2130 observed reflections. In terms of the normally accepted coordination distances edta acts as a quadridentate in this compound. However there are two additional weak but definite links. The tin atom is centered in the largest rectangular face of a distorted triangular prism.
Transdiacetatotetraamminecobalt(III) perchlorate [Co(NH_{3})_{4}(CH_{3}COO)_{2}]ClO_{4} crystallizes in the monoclinic space group P2_{1}/c with a = 1399.5(2), b = 652,6(1), c = 1559.3(2) pm, and Z = 4. Patterson and Fourier techniques were used to determine the structure from threedimensional diffractometer data, following which fullmatrix least squares refinement gave a final conventional R value of .089 based on the 856 observed reflections. Each of the two crystallographically independent transdiacetatotetraamminecobalt(III) cations has a space group implied centre of symmetry. The acetates are coordinated to the cobalt atoms as monodentate ligands and also enter into a complex network of hydrogen bonds extending throughout the crystal.
