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The crystal structure of diaqua(meso-tetraphenylporphinato)cobalt(III) perchlorate, [CoIII(tpp)(H2O)2]ClO4, has been determined by the X-ray method. The compound crystallizes in the monoclinic space group P21/c with four molecules in a unit cell of dimensions, a=13.93(4) Å, b=23.46(2) Å, c=17.35(6) Å, and ß=129.4(2)°. The Co(III) ion lies on the mean plane of the porphinato core, and is coordinated by the four porphinato nitrogen atoms and the two water oxygen atoms. The average Co–N distance is 1.964(4) Å, and the average Co–O(water) distance is 1.936(5) Å. The porphyrin plane is significantly ruffled and has an approximate S4-\bar4 symmetry. The perchlorate anion is not bound directly to the cobalt(III) ion, and links the two adjacent [CoIII(tpp)(H2O)2]+cations by the hydrogen bonds with the aqua ligand oxygen atoms.

A conformational analysis of tetragastrin in an aqueous solution was carried out by a Monte-Carlo simulation, assuming a molecular model in a continuous media. The hydration energy of the peptide was evaluated from a calculations of the peptide–water accessible surface area. The tetrapeptide conformers in the low-energy state take an extended form, in which the two aromatic rings on both termini of the peptide are apart. The extended conformation in which the hydrophilic portions are exposed to solvent water is quite different from that in DMSO.

A crystal of 1,3-dimethyl-5-fluorouracil can be used to solve large amounts of 1,3-dimethyluracil as a solid–solution crystal. The crystal structure has been determined by an X-ray method. The planar molecules are arranged in a parallel sheet, and the molecules within the same sheet interact with each other through short CH···O and CH···F contacts. The short intermolecular C···F distance is 2.999(6) Å. The stability of a mixed crystal could be explained in terms of intermolecular interactions around the fluorine atom.

The crystal structure of calcium Dl-glycerate dihydrate has been determined by the heavy atom method. The crystal is monoclinic, space group P21/c, with unit cell dimensions: a=14.40, b=7.63, c=10.40 Å, and β=98.8°. Two independent glycerate anions have different conformations. β-Hydroxy oxygen in one conformer is trans-gauche to α-carboxy carbon and α-hydroxy oxygen, while that in the other conformer is gauche-gauche. Ca–O interactions and hydrogen bonds stabilize the crystal structure. The calcium ion is bound to three glycerate anions and two water molecules, the two glycerate anions chelating the calcium ion with the α-carboxy oxygen and α-hydroxy oxygen, and third glycerate anion bonding to the calcium ion with β-hydroxy oxygen. Seven oxygens surround a calcium ion in a distorted pentagonal biprism arrangement with Ca–O distances ranging from 2.32 to 2.47 Å.

Solvent effects were introduced into a Monte-Carlo simulation of peptide conformations by the use of a new potential function for evaluating the nonbonding interactions between solute and solvent molecules. The Monte-Carlo program, which included the electrostatic and nonbonding interactions of the solvent, was tested for a conformation analysis of the zwitterionic tetragastrin in DMSO. The theoretical coupling constants were in good agreement with the NMR data. The conformation of the zwitterion was a folded compact form at the lowest energy, which was different from those obtained from a simulation in vacuo and that without nonbonding solvent effects.

The crystal structure of the calcium salt of d-glycero-d-gulo-heptonic acid has been determined by the X-ray method. The crystal is monoclinic of space group P21with unit-cell dimensions of a=10.064(1), b=10.540(2), c=11.340(2) Å, and ß=108.92(1)°. The intensity data for 1754 unique reflections were measured with an automatic diffractometer. A trial structure, obtained by the direct method, was refined by the full-matrix least-squares method to R=0.030. The two independent heptonate anions have different conformations, and they chelate a calcium ion in different ways. The calcium ion is surrounded by eight oxygen atoms in a deformed dodecahedral form, the Ca···O distances ranging from 2.40 Å to 2.48 Å. The distortion of the moleular strcuture of the heptonate anions due to the calcium chelation was discussed in relation to the calcium-binding sites on a linear carbohydrate chain.

The crystal structure of the title complex has been determined by the X-ray method. The complex crystallizes in the monoclinic space group P2/c with a=24.171(9), b=14.037(3), c=24.401(9) Å, ß=119.68(9)°, and Z=4. The structure was solved by the heavy-atom method and refined to R=0.094 for 3838 reflections. Two independent dimers exist with a crystallographically imposed two-fold axis in the unit cell. The two dimers are in an approximately orthogonal arrangement, and they take very similar conformations. The noticeable structural parameters are the average distances of 2.033(28) Å for OsIV–N, 1.808(3) Å for OsIV–O2-, and 1.997(29) Å for OsIV–OCH3. The two porphinato cores bridged by a µ-oxo oxygen atom rotate around the approximately linear Os–O–Os bond (the average valence angle=178°) by 23(1)° from the eclipsed form. The porphine ring is planar within 0.10 Å, and deviation of the Os atom from the porphinato plane of the four nitrogen atoms is 0.06 Å. These results were compared, in the relation of the specific physicochemical properties in solution, with those of the corresponding RuIVcomplexes reported previously.

The crystal structure of calcium d-glucarate tetrahydrate has been determined from three dimensional X-ray data, and refined by the least squares method including an anisotropic temperature factor. The crystals are orthorhombic, space group P212121with a=16.09, b=11.36 and c=6.68Å. The calcium ion is bound to two glucarate molecules and three water molecules. The eight oxygen atoms form the calcium coordination shell of a distorted square-antiprism geometry. The carboxyl group including C(1) of d-glucarate has an eclipsed conformation relative to C(2) and O(2), and is coordinated with one calcium ion through the carboxyl oxygen O(1) and the a-hydroxyl oxygen O(2), and with the other calcium ion through the carboxyl oxygen O'(1) and the hydroxyl oxygens O(3) and O(4). The other carboxyl group including C(6) has an unusual staggered conformation relative to C(5) and O(5), and is not coordinated with calcium ions. However the oxygen atoms of the latter carboxyl group are attached by hydrogen bonds to a number of hydroxyl groups and water molecules, all of which are coordinated with calcium ions.

The conformational free energies of 2-amino-2-deoxy (hydrochloride) and 2-acetamido-d-deoxy derivatives of d-glucose, d-galactose, and d-mannose were calculated by using the empirical potential functions. The most stable conformations of these amino sugars were obtained for a- and ß-anomers in the Cl and 1C chair forms through the procedure of searching for the energy minimum. The results of the energy calculations indicate that the increased anomeric effect in the protonated and N-acetylated amino derivatives in an aqueous solution is mainly due to the electrostatic interaction between the positive-charged amino group on C(2) and the hydroxyl group on the anomeric carbon atom, C(1).

X-Ray crystallographic analysis of two steroid derivatives, 5a,6a-epoxyphysalin B and 2,3-dihydrophysalin B, have been undertaken, revealing their closely similar crystal structures to each other. Their 1H NMR spectra, as well as that of the parent compound physalin B, a 13,14-seco-16,24-cyclosteroid from Physalis alkekengi, have been analyzed based on the crystal structures of these derivatives.

Mixed crystals of formates, with the general formula of (Cu,MII)(HCOO)2·2H2O, were found to show non-uniform changes in lattice constants with the change in the chemical constitution. The reason for this unusual change was sought in relation to a possible non-uniform distribution of the cations over the two non-equivalent sites for metal ions. A simple model based merely on the difference in the radii of metallic ions did not agree with the results of IR measurements nor with those of an ESR study by Wagner et al.Another model, incorporating the change in the direction of the longest axis of the octahedron coordinating to the Cu2+ion at the Ml-site, as suggested from the results of a related work (Part II), was found not only to explain the changes in lattice constants, but also to conform with other evidences; it seems to be an essentially correct interpretation.

The crystal structure of µ-oxo-bis[(octaethylporphinato)ruthenium(IV) chloride] benzene solvate, [Ru(IV)(oep)Cl]2O–C6H6, was determined by the X-ray method. The complex crystallizes in the tetragonal space group P4/nnc, a=13.912(2) Å, c=17.821(4) Å, and Z=2. The structure was solved by the heavy-atom method and refined to R=0.084 for 958 reflections. The [Ru(IV) (oep)Cl]2O complex has the crystallographic D4-422 symmetry and contains the binuclear (Cl)N4Ru–O–RuN4(Cl) coordination group with the Ru–O(µ) distance of 1.793(2) Å, the Ru–Cl distance of 2.320(6) Å, and the Ru–N distance of 2.038(9) Å. The Ru–O–Ru bond is explicitly linear, and the two porphinato cores rotate around the Ru–O–Ru bond by 21.0° from the eclipsed form. The porphinato core is planar within 0.04 Å, and the Ru atom is displaced only by 0.07 Å out of the plane defined by the four porphinato nitrogen atoms toward the bridging O atom. These results are compared with those of the previously reported [Ru(IV)(oep)(OH)2]O–CH3OH crystal.

The crystal structure of (octaethylporphinato)bis(tetrahydrofuran)iron(III) perchlorate was determined by the X-ray method. The complex crystallizes in the monoclinic space group C2/m, a=13.916(3) Å, b=16.509(3) Å, c=10.659(5) Å, ß=118.18(1)°, and Z=2. The structure was solved by the direct method and refined by the full-matrix least-squares method. The final Rvalue was 0.079 for 597 reflections. The complex has a crystallo-graphically imposed twofold axis and a mirror of symmetry. The porphinato core is planar within 0.06 Å. The iron(III) ion lies at the center of the octahedron formed by the four porphinato nitrogen atoms and the two tetrahydrofuran oxygen atoms. The axial Fe–O distance, 2.187(11) Å, is considerably longer than the reported distances for high-spin porphinatoiron(III) complexes, while the equatorial Fe–N distance, 1.978(12) Å, is comparable to those for low-spin and intermediate-spin porphinatoiron(III) complexes. The Fe–O and Fe–N bond distances are well explained in terms of an intermediate-spin state of the iron(III) ion.

Lanthanoid-induced 1H NMR shifts of glyceric acid, gluconic acid, and lactobionic acid were observed in D2O. Stoichiometric analysis using the shift data at various pH values indicated that the concentration of a 1 : 1 complex between substrates and lanthanoid ions was higher than that of a 2 : 1 complex at a low pH. The structure of an axially symmetric 1 : 1 complex was obtained on the assumption of a predominant pseudo-contact interaction between a europium ion and the ligand nuclei. All the title glycosidic acids were found to chelate the cation with a-carboxy, a-hydroxy, and ß-hydroxy oxygens. The relative position of ß-hydroxy oxygen is particularly important for the complex formation between ß-hydroxy carboxylic acids and metal ions.

The crystal structure of potassium d-glucarate was determined by X-ray analysis. The conformation of the glucaric anion in the potassium salt differs from that of the dianion in the crystal of the calcium salt. The proton magnetic resonance spectra of the solutions of the potassium salt and the calcium salt show that the glucarate solution is an equilibrium mixture of the two conformers observed in the crystals. Studies on the induced shifts by adding europium nitrate to the acidic solution indicate that the europium ions are selectively bound to the potassium type conformer. Calcium sequestant by the glucaric acid in alkaline solutions should occur when calcium ions bind the calcium type conformers in a dianionic state.

The crystal structure of bis(o-ethoxyphenyl)butadiyne has been determined by the statistical method of X-ray analysis. The space group is P21⁄awith two molecules in the unit cell of dimensions a=14.64, b=11.27, c=5.19 Å, and β=105.6°. The crystal structure is built up from columns of the molecules packed along the c-axis. The molecule has a center of symmetry and is almost planar. The diacetylene group is slightly twisted and the three conjugated bond distances of the diacetylene group are 1.434, 1.201, and 1.371 Å.

The crystal of the title complex is monoclinic, P21/a with these unit cell dimensions: a=16.16, b=19.18, c=15.46 Å, and β=98°. The crystal structure has layers of hydrogen-bond networks formed by the guanidinium and bromide ions. Two different conformers of the tetrapropylammonium ions are packed between the networks.