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Two new mononuclear complexes, [Cu2Cl1.23(NO3)0.77(Ampy)4(H2O)4](NO3)2·4H2O (I) and [CdI2(Ampy)2] (II) (Ampy = 4-amino-6-methoxypyrimidine) have been synthesized and characterized by single crystal X-ray diffraction studies (CCDC nos. 2023331 (I), 2023331 (II)) at 295 K for (I) and 100 K for (II). The structure of the Cu(II) complex shows that the Cu(II) central atom is five-coordinated with a distorted square pyramidal geometry. In compound (II) the Cd(II) cations are tetracoordinated with a distorted tetrahedral fashion. Intermolecular interactions were investigated by Hirshfeld surfaces. Electronic properties such as HOMO and LUMO energies were derived. [ABSTRACT FROM AUTHOR]

(C6H18N3)4[CuCl5]2[CuCl4]3·1.42H2O is prepared and characterized by various physicochemical techniques. The single crystal X-ray diffraction structural analysis reveals that the title compound belongs to the orthorhombic system with the space group Cmca. Its unit cell dimensions are: a = 24.286(2) Å, b = 14.3082(14) Å, c = 16.6160(16) Å, Z = 4, V = 5773.8(10) Å3. Its crystal structure is determined and refined down to R = 0.024 and wR(F2) = 0.059. The structure contains three crystallographically independent Cu2+ ions coordinated to chlorine anions in various fashions. Cu1 is five-coordinated in a distorted square pyramidal fashion, while Cu2 and Cu3 are four-coordinated in square planar and distorted tetrahedral fashions, respectively. The entities are interconnected by means of the hydrogen bonding [O(W)-H...Cl, N-H...Cl, C-H...Cl and C-H...O(W)], forming a three-dimensional network. Intermolecular interactions are investigated by Hirshfeld surfaces and the contacts of the eight different chloride atoms are notably compared. The vibrational absorption bands are identified by infrared spectroscopy. The optical study is performed by UV-vis absorption. [ABSTRACT FROM AUTHOR]

The experimental charge density methodology is extended to macromolecular structure and biocrystallography. Ultrahigh‐resolution diffraction data now can be collected at third‐generation synchrotron sources for well‐ordered protein crystals; the data can be refined with a more sophisticated model than the independent atom model (IAM), such as the multipolar atom. A new crystallographic program MoPro combining small molecules and macromolecular refinement method has been developed; first applications are described. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [ABSTRACT FROM AUTHOR]

The constant advances in synchrotron radiation sources and crystallogenesis methods and the impulse of structural genomics projects have brought biocrystallography to a context favorable to subatomic resolution protein and nucleic acid structures. Thus, as soon as such precision can be frequently obtained, the amount of information available in the precise electron density should also be easily and naturally exploited, similarly to the field of small molecule charge density studies. Indeed, the use of a nonspherical model for the atomic electron density in the refinement of subatomic resolution protein structures allows the experimental description of their electrostatic properties. Some methods we have developed and implemented in our multipolar refinement program MoPro for this purpose are presented. Examples of successful applications to several subatomic resolution protein structures, including the 0.66Å resolution human aldose reductase, are described. [ABSTRACT FROM AUTHOR]

Analyzes the crystal structure, thermal vibrations and electron density of the peptide N-acetyl-L-tyrosine ethyl ester monohydrate, using single-crystal X-ray diffraction data. Comparison of deformation densities with those obtained from conventional diffractometers equipped with scintillation detectors.