O2 and CO binding to tetraaza-tripodal-capped iron(II) porphyrins

A series of tris(2-aminoethylamine) (tren) capped iron(II) porphyrins has been synthesized and characterized and their affinities for dioxygen and carbon monoxide measured. The X-ray structure of the basic scaffold with nickel inserted in the porphyrin is also reported. All the ligands differ by the nature of the group(s) attached to the secondary amine functions of the cap. These various substitutions were introduced to probe if a hydrogen bond with these secondary amine groups acting as the donor could rationalize the high affinity of these myoglobin models. This work clearly indicates that the cage structure of the tren predominates over all the other appended groups with the exception of p-nitrophenol.     

Animal urine as painting materials in African rock art revealed by cluster ToF‐SIMS mass spectrometry imaging

The rock art site at the village of Songo in Mali is a very important Dogon ritual place where, since the end of the nineteenth century until today, takes place the ceremony of circumcision. During these ceremonies, paintings are performed on the walls of the shelter with mainly three colors: red, black and white. Ethnological literature mentions the use of animal urine of different species such as birds, lizards or snakes as a white pigment. Urine of these animals is mainly composed of uric acid or urate salts. In this article, time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) is used to compare uric acid, snake urine and a sample of a white pigment of a Dogon painting coming from the rock art site of Songo. ToF‐SIMS measurements in both positive and negative ion modes on reference compounds and snake urine proved useful for the study of uric acid and urate salts. This method enables to identify unambiguously these compounds owing to the detection in negative ion mode of the ion corresponding to the deprotonated molecule ([M ? H]^? at m/z 167.01) and its fragment ions. Moreover, the mass spectra obtained in positive ion mode permit to differentiate uric acid and urate salts on the basis of specific ions. Applying this method to the Dogon white pigments sample, we show that the sample is entirely composed of uric acid. This proves for the first time, that animal urine was used as a pigment by the Dogon. The presence of uric acid instead of urate salts as normally expected in animal urine could be explained by the preparation of the pigment for its application on the stone. Copyright © 2010 John Wiley & Sons, Ltd.     

Vibrational dynamics of the hydrogen bond in H(2)S-HF: Fourier-transform-infrared spectra and ab initio theory

The rotationally resolved infrared spectrum of the hydrogen bonded complex H(2)S-HF and of its isotopomer D(2)S-DF in the HF/DF stretching range have been observed in a supersonic jet Fourier-transform infrared (FTIR) experiment and indicate a predissociation lifetime of 130 ps for H(2)S-HF. Complementary spectra taken at a temperature of 190 K in a cell without resolved rotational structure indicate the presence of strong anharmonic couplings between low frequency intermolecular modes and the HF donor stretch mode previously observed in other complexes with heavier acceptor molecules without rotational fine structure. The anharmonic analysis of the hot band progressions and of the rotational data confirm the coupling mechanism. The coupling constants and the absolute frequency of the hydrogen bonded stretch mode are in excellent agreement with theoretical predictions based on adiabatic variational calculations on potential surfaces computed at MP2 and CCSD(T) level. Complementary calculations with a perturbational approach further confirm the coupling model.     

New Components Including Cyclopeptides from Barks of Christiana africana DC. (Tiliaceae)

Phytochemical investigation of barks of Christiana africana led to the identification of cyclopeptide alkaloids, flavonoids, coumarinolignans, iridoids, sesquiterpenoids, and triterpenes. This plant was classified so far in the Tiliaceae family. This study was started while the genomic study of numerous specimens was described in order to establish new criteria for Malvales botanical classification. In the present work, twenty components were identified, belonging to the three major classes of secondary metabolites: alkaloids, phenols, and terpenes. In the first class, cyclopeptides are well‐known compounds in Rhamnaceae and Sterculiaceae. Their presence in Malvaceae (in APG2 sensus) suggests a possible chemical link between the ex‐Tiliaceae and the Malvaceae.     

Cyclodextrin as a Template for Molecular Assembly: Formation of Heterodimers Between a Polyamino- and a Polysulfonato-β-Cyclodextrin

A poly(hydroxyethylamino)- and a poly(sulfonatophenyloxy)--cyclodextrin derivative, bearing opposite ionic charges, have been shown by potentiometric titration to form stable pH-dependent heterodimers with each other in water. The formation constants of these dimers show that a very stable assembly is formed between the fully deprotonated sulfonato derivative and the fully protonated amino derivative (log K_a = 8.5), which constitutes the assembly of multiple extended atomic groupings on cyclodextrin as template.     

Comparative studies of quasi-relativistic density functional methods for the description of lanthanide and actinide complexes

We present a comparative Density Functional Theory (DFT) study based on two different implementations of relativistic effects within the Kohn-Sham (KS) approach, to describe the metal-ligand interaction in I(3)M-L complexes (L = NH(3), NCCH(3), CO and M = La, Nd, U). In the first model, the scalar corrections were included by a quasi-relativistic approach (QR) via the so-called ZORA or Pauli Hamiltonians, while in the second, these effects are taken into account in a quasi-Relativistic Effective Core Potential (RECP). These relativistic approaches were used in conjunction with various gradient corrected (GGA) or hybrid (SCH) functionals. The structural parameters obtained from geometry optimizations have been compared to experimental structural trends, and rationalized by a KS orbital analysis. Both approaches provide similar results for mainly ionic metal-ligand bonds (e.g., for the sigma-donor ligand L = NH(3)). For the pi-acceptor ligands (NCCH(3), CO), the QR approach is in agreement with experimental trends and consistent with the presence of a backbonding interaction between U(III) and the neutral ligand, which does not exist in the lanthanide homologues. The GGA/RECP methods also reproduce this phenomenon, while the SCH/RECP scheme fails to describe this interaction. The role of the RECP, of its size, and of additional polarization functions has also been examined. Finally, the failure of the SCH/RECP approach was interpreted as a consequence of a bad estimation of frontier orbital energy levels in the uranium and ligand species.     

Single crystalline commensurate metallic assemblages of pi-slabs and CdI2-type layers: synthesis and properties of beta-(EDT-TTF-I2)2[Pb5/6 square 1/6I2](3) and beta-(EDT-TTF-I2)2[Pb2/3+xAg1/3-2x square xI2]3, x = 0.05

The ability of I...I van der Waals interactions to direct the self-assembly of slabs of the radical cation of ethylenedithio-1,2-diiodo-tetrathiafulvalene, EDT-TTF-I(2), and polymeric lead iodide covalent anionic layers is demonstrated by the synthesis of single crystals of beta-(EDT-TTF-I(2))(2)(.+)[(Pb(5/6) square (1/6)I(2))(1/3-)](3), triclinic, P-1, a = 7.7818(8), b = 7.9760(8), c = 19.9668(2) A, alpha = 82.409(12), beta = 85.964(12), gamma = 61.621(11) degrees, V = 1080.76(19) A(3), R1, wR2 = 0.0459, 0.0947; and beta-(EDT-TTF-I(2))(2)(.+)[(Pb(2/3+x)Ag(1/3-2x)square(x)I(2))(1/3-)](3), x approximately 0.05, triclinic, P-1, a = 7.7744(8), b = 7.9193(8), c = 19.834(2) A, alpha = 87.189(12), beta = 83.534(12), gamma = 61.602(11) degrees, V = 1067.4(2) A(3), R1, wR2 = 0.0508, 0.0997. The state-of-the-art, combined microprobe and structural analysis of the metal site vacancies and occupancies patterns reveal a commensurate organic-inorganic interface and point out the importance of halogen.halogen van der Waals interactions to future studies aiming at directing interface topologies. The electronic structure, room-temperature metallic character and metal-insulator transition at ca. 70 K of the two-dimensional organic slabs are retained upon alloying of the inorganic sublattice with monocations. The room-temperature conductivity of the metallic lead-silver alloy is 2 orders of magnitude larger than that of beta-(EDT-TTF-I(2))(2)(.+)[(Pb(5/6) square (1/6)I(2))(1/3-)](3). This calls for the study of materials with diverse alloying patterns with metal cations of different nature and charge.     

Simultaneous measurement of drug metabolic stability and identification of metabolites using ion-trap mass spectrometry

The use of in vitro drug metabolism data in the understanding of in vivo pharmacokinetic, safety and toxicity data has become a large area of scientific interest. This has stemmed from a trend in the pharmaceutical industry to use in vitro data generated from human tissue as a criterion to select compounds for further investigation. As well as measuring metabolic stability in vitro using human liver microsomal preparations, the identification of possible metabolite(s) formed may play a vital role in Hit-to-Lead and Lead optimisation processes. The data-dependent scan function mode with the ion-trap instrumentation provides the ability to measure the metabolic stability and identification of possible metabolites of a compound. A gradient liquid chromatographic method with a run time of 6 min/injection was developed for this purpose. The approach of simultaneous metabolic stability measurements and rapid identification of metabolites of drugs with high (verapamil), medium (propranolol and cisapride) and low (flunarazine) metabolic stabilities using ion-trap mass spectrometry is described. The metabolites identified after 15 min incubation for verapamil, propranolol and cisapride are in good agreement with those reported as the major metabolites in human in vivo studies.