Molecular catenation via metal-directed self-assembly and pi-donor/pi-acceptor interactions: efficient one-pot synthesis, characterization, and crystal structures of [3]catenanes based on Pd or Pt dinuclear metallocycles

Dinuclear square metallocycles 3a,b assemble spontaneously when M(en)(OTf)2 (M = Pd, Pt) and a 4,4'-bipyridinium ligand are mixed in acetonitrile. Six new [3]catenanes were prepared in good yields by thermodynamically driven self-assembly reaction of molecular squares 3a,b and pi-complementary dioxoaryl cyclophanes. Single-crystal X-ray analyses of the [3]catenanes revealed the insertion of two aromatic units inside the metallocycle cavity. The structures are stabilized by means of a combination of pi-pi stacking, [C-H...pi] interactions, and [C-H...O] hydrogen bonds. [3]Catenane (DB24C8)2-(3a) showed in solid-state two external DB24C8 rings positioned over the Pd(en) corners, which are held in position by [N-H...O] hydrogen bonds. Furthermore, formation of catenane (DB24C8)2-(3a) can be switched off and on in a controllable manner by successive addition of KPF6 and 18-crown-6.     

Data fusion in the wavelet domain by means of fuzzy aggregation connectives

Dual-domain classification analysis is proposed to identify pigments used in works of art studied by Raman spectroscopy and X-ray fluorescence spectrometry. By means of this methodology, Raman and X-ray fluorescence data are jointly processed by a high-level fusion approach. The system proposed aims to avoid the pre-processing stage and directly process raw data obtained from the instrument. The system is tested with spectra contaminated with background components of different shapes and intensities and with those with the background removed by line segment correction. The benefits of the approach were well demonstrated in a study of an ochre pigment classification.The approach is based on the main advantage of wavelet transform, which is multiresolution. Each spectrum is split into blocks, according to a specific frequency, to form a wavelet prism. Partial least squares-discriminant analysis (PLS-DA) is then applied to those blocks which contain the deterministic part of the signal and are not influenced by noise and background signal components. At the end, to obtain the final classification assignment, high-level data fusion of the classifications results (decision levels) obtained from PLS-DA analysis is done by means of fuzzy aggregation connective operators. Our study showed that fuzzy aggregation may be suitable for performing high-level data fusion on dual-domain data. This method can be automated so that classification can be rapid. It can handle classifications with different levels of difficulty and requires no prior knowledge of sample composition.     

Pressurized liquid extraction-assisted mussel cytosol preparation for the determination of metals bound to metallothionein-like proteins

The possibilities of pressurized liquid extraction (PLE) have been novelty tested to assist the cytosol preparation from wet mussel soft tissue before the determination of metals bound to metallothionein-like proteins (MLPs). Results obtained after PLE were compared with those obtained after a classical blending procedure for mussel cytosolic preparation. Isoforms MLP-1 (retention time of 4.1 min) and MLP-2 (retention time of 7.4 min) were separated by anion exchange high-performance liquid chromatography (HPLC) and the concentrations of Ba, Cu, Mn, Sr and Zn bound to MLP isoforms were directly measured by inductively coupled plasma-atomic emission spectrometry (ICP-OES) as a multi-element detector. The optimized PLE-assisted mussel cytosol preparation has consisted of one extraction cycle at room temperature and 1500 psi for 2 min. Since separation between the solid mussel residue and the extract (cytosol) is performed by the PLE system, the cytosol preparation method is faster than conventional cytosol preparation methods by cutting/blending using Ultraturrax or Stomacher devices.     

Synthesis, characterization, and reactivity of ruthenium diene/diamine complexes including catalytic hydrogenation of ketones

Thermal reactions between [RuCl2(diene)]n (diene = 2,5-norbornadiene, nbd; 1,5-cyclooctadiene, cod) with an excess of N,N,N',N'-tetramethylethylene diamine (tmeda) afforded derivatives [RuCl2(diene)(tmeda)] (diene = nbd, 1; cod, 2) as a mixture of cis and trans isomers. When thermolysis was performed under H2 mixtures of hydride species [RuCl(H)(diene)(tmeda)] (diene = nbd, 3; cod, 4) and the bis-tmeda adduct trans-[RuCl2(tmeda)2] (5) were obtained in different ratios depending upon the reaction conditions and reaction times. Heating polymeric Ru(II) precursors in toluene in the presence of a 5-fold excess of the bulkier N,N,N',N'-tetraethylethylene diamine (teeda) resulted in a rare diamine dealkylation process with formation of trans-[RuCl2(nbd)(Et2NCH2CH2NHEt)] (6) and trans-[RuCl2(cod)(EtHNCH2CH2NHEt)] (7) in high yields. The presence of N-H functionalities in the coordinated diamine ligands of 6 and 7 was unambiguously established by single-crystal X-ray diffraction studies. The dealkylation process of the teeda ligand seems to proceed intramolecularly as shown by solution NMR studies performed with the soluble Ru(II) precursors trans-[RuCl2(amine)2(diene)] (diene = nbd, amine = morpholine, 9; diene = cod, amine = Et2NH, 10). The above complexes [RuCl2(diene)(diamine)] have been tested as precatalysts in the hydrogenation of ketones both for transfer as well as direct hydrogenation, the latter route being the most effective.     

Revisiting the calculation of condensed Fukui functions using the quantum theory of atoms in molecules

The analysis of previously reported shortcomings of the condensed Fukui functions obtained making use of the quantum theory of atoms in molecules indicates these drawbacks are due to the inadequacy of the definition employed to compute them and not to the partitioning. A new procedure, which respects the mathematical definition and solves these problems, is presented for the calculation of condensed Fukui functions for atomic basins defined according to the quantum theory of atoms in molecules. It is tested in a set of 18 molecules, which includes the most controversial reported cases.     

Mathematical model for the prediction of the overall profile of in vitro solute release from polymer networks

The loading of solutes onto and their release from hydrogel-based devices can be better understood when they are treated as a partition phenomenon. Partition activity (alpha) is a parameter that determines the existence of partition phenomena. It expresses the physical chemical affinities of the solute between the solvent and hydrogel phases. When alpha=0, there is no release of the solute from the hydrogel; however, if alpha>0, there is partitioning of the solute between the solvent and the hydrogel phases, and release of the solute from the hydrogel can be observed. The mathematic model proposed here predicts the overall release profile of vitamin B(12), methylene blue (MB), and acid orange 7 (AO) from semi-interpenetrating network (semi-IPN) hydrogels composed of PNIPAAm and PAAm. Experimental release tests demonstrated that alterations on variables of the system change both the released fraction and the release rate of such solutes, confirmed by the changes on values of alpha (an equilibrium parameter) and k(R) (an kinetic parameter). The modeling of solute release describes the alpha effects on release of the solute from polymer networks. The solute release mechanism is viewed here as a diffusional transport process and as a partition phenomenon. The partitioning of the solutes occurs between the solvent phase and the hydrogel phase, and the possible physical chemical affinities of the solute between hydrogel and solvent are considered.     

Regioselective synthesis of 4- and 7-alkoxyindoles from 2,3-dihalophenols: application to the preparation of indole inhibitors of phospholipase A2

An efficient and regioselective synthesis of 4- and 7-alkoxyindoles has been developed from commercially available starting materials such as 3-halophenols and 3-chloroanisole. Directed ortho-metalation followed by two palladium-catalyzed processes, a Sonogashira coupling and a tandem amination/cyclization reaction, allows the synthesis of regiochemically pure 4- and 7-substituted indoles. This strategy has been successfully applied to the preparation of 2-[3-(2-amino-2-oxoacetyl)-1-benzyl-2-ethyl-1H-indol-4-yloxy]acetic acid (LY315920), a known inhibitor of phospholipase A2.     

The mechanism of Tröger's base formation probed by electrospray ionization mass spectrometry

Using direct infusion electrospray ionization mass and tandem mass spectrometric experiments [ESI-MS(/MS)], we have performed on-line monitoring of some reactions used to form Tr?ger's bases. Key intermediates, either as cationic species or as protonated forms of neutral species, have been intercepted and characterized. The role of urotropine as the methylene source in these reactions has also been accessed. Reaction pathways shown by ESI-MS(/MS) have been probed by gas-phase ion/molecule reactions, and an expanded mechanism for Tr?ger's base formation based on the mass spectrometric data has been elaborated.