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The crystal structures of the ligand AAZTA (6-amino-6-methylperhydro-1,4-diazepine tetraacetic acid) and of its Gd complex Na[Gd(H 2 O)AAZTA] · 3H 2 O have been determined by single crystal X-ray diffraction. The AAZTA ligand crystallizes in a zwitterion form with two deprotonated carboxylic groups and two protonated tertiary nitrogen atoms. Two independent molecules of about a similar conformation and three water molecules as asymmetric units, are present in the crystal. In the solid state the gadolinium complex is a centrosymmetric dimer with a bicapped square antiprismatic coordination geometry around each metal ion. Two symmetric bridging carboxylate groups determine the dimer formation with Gd–O(2) and Gd–O(2)′ bond distances rather comparable of 2.526(4) and 2.548(4) A, respectively, while the Gd–O(1) (inner sphere water) bond distance is 2.443(5) A. A network of hydrogen bonds between the water of inner and outer spheres and the AAZTA carboxylic groups is present in the crystal structure.

The crystal structures of the salts of (S)- and (R)-1,4-benzodioxane-2-carboxylic acid with (S)-1-phenylethylamine and its p-methyl and p-nitro substituted analogues were determined in order to correlate the differences in solubility between diastereomeric salts with their solid state structures. A common characteristic of the six structures is the presence of hydrogen bond interactions, which always involve the ammonium group NH3+ and the carboxylic oxygens of three adjacent acid molecules with the formation of molecular chains in the direction of the binary screw crystallographic axis (unique axis in the monoclinic system and, in the orthorhombic space group, coincident with the direction of the shortest cell axis). A determinant factor for the high inter diastereomer solubility difference of the two pairs of p-methyl and p-nitro substituted amine salts seems, in the case of the p-methyl derivatives, to be the different mutual disposition of the acid and amine aromatic rings at the boundaries of the molecular chains and, for the p-nitro derivatives, the prevalence, in the same region, of the nitro groups or of the acid aromatic moieties. A morphologic study at SEM revealed some correlation between the crystal habit and solubility. Theoretical calculations, based on the LSER model, account for the observed solubilities in methanol.

The reactions of iodoflavone with 3-methyl-3-hydroxybut-1-yne and 3-methylbut-3-en-2-yne are described and the antimicrobial and cytotoxic activities of the obtained compounds have been tested. The molecular structures of 6-(3-hydroxy-3-methylbut-1-ynyl)-flavone (1a) and 6-(3-methylbut-3-en-1-ynyl) flavone (1b) have been determined by X-ray crystallography. The planar configuration of the two compounds has been attributed to intramolecular hydrogen bond interactions. In 1a, the presence of the hydroxyl group determines a dimeric arrangement of the molecules. In both compounds in the crystal state, molecular stacking has been observed.

The mutant S64C of the short-chain flavodoxin from Desulfovibrio vulgaris has been designed to introduce an accessible and reactive group on the protein surface. Crystals have been obtained of both the monomeric and homodimeric forms of the protein, with the cofactor FMN in either the oxidized or the one electron-reduced (semiquinone) state, and the structures have been determined to high resolution. The redox properties of the different species have been investigated and the variations observed with respect to wild type have been related to the structural changes induced by the mutation and S–S bridge formation.

Two gadonilium DOTAM complexes [Gd(DOTAM)H2O](CF3SO3)3 · 3H2O (1) and [Gd(DOTAM)H2O](CF3SO3)3 · 0.5H2O · CH3CN (2) have the structure of the M isomer, with coordination geometry around the Gd ion capped square antiprismatic (SA). They differ for the Gd–Owater bond lengths of 2.396(6) and 2.474(7) A in (2) where two independent molecules are present in the crystal cell. The factors influencing the Gd–Owater bond distance, important for the water exchange rate in MRI experiments, have been correlated to the different network of hydrogen bonds involving the Gd coordinated water molecule. The X-ray structure of the parent compound [Pr(DOTAM)H2O](CF3SO3)3 · H2O · CH3CN (3) reveals an unexpected twisted square antiprismatic (TSA) coordination geometry characteristic of the m isomer.

The X-Ray crystal and molecular structures of the 4-pyrazol derivatives 3-methyl-4-diazo-5-benzamido-1H-pyrazole (4) and 3-benzamido-5-methyl-1H-pyrazole (3) have been determined. A dimeric structure has been found for the first and polymeric for the second. A comparison of 4 with 1,3-dimethyl-4-diazo-5-benzamido-lH-pyrazole (2) shows differences in the geometrical parameters of the pyrazole ring due to electron delocalization in 2 consequent to the nitrogen negative charge in the latter. Theoretical investigation at the density functional theory (DFT) level shows difference in the molecular electronic distribution of 2 and 4, in agreement with the structural parameters and the IR stretching frequencies of the respective carbonyl moieties.