Biomedical subjects
Publications and source records attributed to C S Frampton.
Utilization of double aromatic pi-stacking interactions on a 2,3-diaminobutane framework provides a new motif for structurally rigid C2-symmetrical propeller-shaped chiral 1,2-diamines.
A monoclinic centrosymmetric form of zopiclone dihydrate undergoes a sequential, two-step transformation in the solid-state upon heating which results in separation of the enantiomers into a racemic conglomerate or racemic twins.
Three newly elucidated crystal structures of group IV phthalocyaninato complexes are reported, along with data for two further SiPc carboxylate complexes. In one of these crystal structures, bis(undecylcarboxylate)Sn(IV) phthalocyanine, the tin ion is seven coordinate, which is a unique finding for this atom in phthalocyanine ring coordination. Comparison of these structures with other group IV phthalocyaninato and related structures reveals differences, illustrating features significant in the chemistries of Si(IV) and Sn(IV) ions. These differences are thought to originate from their differing sizes and polarizabilities. The structures show that the Sn(IV) ion can only occupy an in-plane location in the phthalocyaninato ring where it elongates toward the two axial ligands. When the axial ligands do not facilitate this elongation cis coordination is preferred and the Sn(IV) ion sits above the phthalocyaninato ring plane. In contrast, the Si(IV) structures, with smaller, harder (i.e., less polarizable) Si(IV) ions, are six coordinate with the Si(IV) ion in the phthalocyaninato ring plane in a distorted octahedral symmetry. The electronic spectra and cyclic voltammetry of some of the Si compounds indicate that on the electrode the oxidized/reduced species behave as though they are in a solid film, rather than a soluble freely diffusing species.
The structures of the highly substituted title heterocycles, C(20)H(22)N(2)S and C(20)H(22)N(2)O(2)S, have been determined at 123 (1) K. Both molecules possess exact C(2) symmetry and the seven-membered rings have very similar twist-boat conformations. The magnitudes of the C-S-C bond angles, 107.13 (6) and 108.27 (7) degrees, respectively, are influenced significantly by the four substituent methyl groups on the seven-membered rings.
The crystal structure of the title compound is presented and shown to be one of a class of low-spin iron porphyrin complexes having a ground-state electronic configuration of (dxy)2(dxz)2(dyz)1. If their Fe-N bond lengths (average N-porphyrin plotted against average N-axial) are considered, this class of low-spin iron(III) porphyrins of general formula [Fe(III)Por(L)2]+X- and of 2B ground state is shown to be distinctly different crystallographically from a similar class of compounds with the same general formula but with a 2E or a (dxy)2(dxz,dyz)3 ground state. A third group of compounds with the same general formula have a (dxz,dyz)4(d)1 ground state and again are in a different region of the plot. Compounds showing intermediate properties can be forecast from the simple relationship presented in this work. The electron paramagenetic resonance data are shown to be dependent on the ground state, and those of configuration (dxy)2(dxz,dyz)3 and the 2B ground state obey a correlation previously suggested in the literature.
The structure of bis(4,4"-decyloxy-p-terphenyl-2'-ylmethyl) carbonate, C(79)H(110)O(7), (I), has been determined at 123 K. It is a new type of twin mesogen. No two adjacent aromatic rings are coplanar and the four decyloxy side chains are maximally extended. Molecules of the compound are packed along the crystallographic a axis. The molecular arrangement is a precursor of a smectic A phase.
This paper describes a method for the laboratory-scale crystallization of the orthorhombic polymorph (form II) of paracetamol (acetaminophen) from solution. Its structure has been determined by single-crystal X-ray crystallography at 298 K (to confirm the results of data published in 1974) and at 123 K (to improve the overall accuracy of the structure determination). Despite considerable effort by many investigators, the crystallization of form II from solution, using the method given in the 1974 structure report, has been elusive. The incentive for this effort is that form II, unlike commercial paracetamol (form I), undergoes plastic deformation and is suitable for direct compression. Consequently, the ability to produce form II in quantity has attracted much interest because of the potential commercial benefits to be gained by not using binders during the manufacture of tablets. However, until now, the only method that has been reported for the bulk preparation of form II has been to grow it as polycrystalline material from fused form I. This study also compares the solid-state properties of form II with those of form I, with particular emphasis on the crystallography (both X-ray and optical), crystal morphology, thermal behavior, and compaction properties.