Showing papers in "Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry in 1971"

The stereochemical basis of anticonvulsant drug action. I. The crystal and molecular structure of diphenylhydantoin, a noncentrosymmetric structure solved by centric symbolic addition

Abstract: To investigate relationships between the molecular shape and biological activity of anticonvulsant drugs we have determined the molecular structure of diphenylhydantoin. The compound crystallizes in the orthorhombic system with cell dimensions a=6.230, b=13.581, c=15.532A,, space group Pn2~a. A total of 1210 independent reflections to 20= 50 ° for Mo K~ radiation was measured on a fourcircle diffractometer. The structure was solved by centrosymmetric phasing techniques, utilizing Sayre's equation for direct sign determination in space group Pnma. This technique proved successful because the 7-atom hydantoin group lies in a plane only 2.40 ° from (010) with the two phenyl rings on each side of the plane. Thus, the structure approximates the situation that would exist for special position (e) of Pnma, and many reflections have phases close to 0 or 7r. The plane of the hydantoin ring forms angles of 113 and 114 ° with the planes through the two phenyl rings. The phenyl-phenyl angle is 90 °. Final R index is 0-052.

The crystal structure of copper metaborate, CuB2O4

Abstract: This work forms part of the Ph. D. Thesis of one of us (M.M.R.) who also acknowledges the research grant given by Ministerio de Educacion y Ciencia, Spain.

The crystal structure of quinolinium bis(7,7,8,8-tetracyanoquinodimethanide), Q+(TCNQ)2−

Abstract: Crystals of Q+(TCNQ)~are monoclinic, with space group C2/c and a = 28.468, b = 3.838, c = 25.704/~ and ,fl = 113.6 °. There are four formula units in the unit cell. The structure was deduced from Patterson syntheses and refined by the block-diagonal least-squares method to an R value of 0.120 for 1274 observed reflexions. The structure consists of columns of monadic units of TCNQ parallel to the b axis. The TCNQ molecules are stacked in a fashion characteristic of the structures of TCNQ salts. The average spacing between the TCNQ molecules in the column is 3.22/~. The shape and size of the TCNQ units seem to be intermediate between those of TCNQ ° and TCNQ-. Quinolinium cations are arranged in the channels formed by the TCNQ columns. The structure is disordered, with quinolinium cations adopting either of the alternative orientations with equal probability. They also form a stack parallel to the b axis with the much wider spacing of 3.50 A,. The estimation of molecular interaction energy for the system (TCNQ)~has revealed that the geometrical relationship of the two TCNQ units is determined primarily by the charge-transfer interaction and in part by interactions between the nonbonded atoms.