Synthesis, coordination properties, and analytical applications of mixed donor macrocycles containing the 1,10-phenanthroline sub-unit

The coordination properties towards different metal ions of a new class of mixed N/S-, and N/S/O-donor macrocycles containing the 1,10-phenanthroline sub-unit in the cyclic framework are reviewed. The conformational constraints imposed by the heteroaromatic fragment onto the aliphatic portion of the ring determine the coordination mode of these ligands which can stabilise low-valent Ni⁺, Pd⁺, Pt⁺, and Rh⁺ metal complexes. Structural and thermodynamic aspects of the coordination chemistry of these ligands are considered together with possible applications as building blocks in the synthesis of multi-centred systems, and as template in the construction of extended polyiodide networks. However, solution studies demonstrate the inability of these ligands to work as selective and specific fluorescent chemosensors for heavy transition and post-transition metal ions and the formation constants evaluated for the formation of 1:1 complexes with Pb²⁺, Cd²⁺, Hg²⁺, Cu²⁺, and Ag⁺ in acetonitrile are of the same order of magnitude. Nevertheless, some of these macrocyles are extremely effective to recognise Cu²⁺ or Ag⁺ over the other metal ions in transport processes, and have been successfully used as neutral ionophore in the construction of PVC-based ionselective electrodes and supported liquid membranes for analytical detection and separation, respectively, of these metal ions.     

Can Serendipity Still Hold Any Surprises in the Coordination Chemistry of Mixed-Donor Macrocyclic ligands? The Case Study of Pyridine-Containing 12-Membered Macrocycles and Platinum Group Metal ions PdII,PtII, and RhIII

This study investigates the coordination chemistry of the tetradentate pyridine-containing 12-membered macrocycles L¹-L³ towards Platinum Group metal ions Pd^II, Pt^II, and Rh^III. The reactions between the chloride salts of these metal ions and the three ligands in MeCN/H₂O or MeOH/H₂O (1:1 v/v) are shown, and the isolated solid compounds are characterized, where possible, by mass spectroscopy and ¹H- and ¹³C-NMR spectroscopic measurements. Structural characterization of the 1:1 metal-to-ligand complexes [Pd(L¹)Cl]₂[Pd₂Cl₆], [Pt(L¹)Cl](BF₄), [Rh(L¹)Cl₂](PF₆), and [Rh(L³)Cl₂](BF₄)·MeCN shows the coordinated macrocyclic ligands adopting a folded conformation, and occupying four coordination sites of a distorted square-based pyramidal and octahedral coordination environment for the Pd^II/Pt^II, and Rh^III complexes, respectively. The remaining coordination site(s) are occupied by chlorido ligands. The reaction of L₃ with PtCl₂ in MeCN/H₂O gave by serendipity the complex [Pt(L³)(μ-1,3-MeCONH)PtCl(MeCN)](BF₄)₂·H₂O, in which two metal centers are bridged by an amidate ligand at a Pt1-Pt2 distance of 2.5798(3) Å and feature one square-planar and one octahedral coordination environment. Density Functional Theory (DFT) calculations, which utilize the broken symmetry approach (DFT-BS), indicate a singlet d⁸-d⁸ Pt^II-Pt^II ground-state nature for this compound, rather than the alleged d⁹-d⁷ Pt^I-Pt^III mixed-valence character reported for related dinuclear Pt-complexes.     

Interaction of cisplatin with human superoxide dismutase

cis-Diamminedichloroplatinum(II) (cisplatin) is able to interact with human superoxide dismutase (hSOD1) in the disulfide oxidized apo form with a dissociation constant of 37 ± 3 μM through binding cysteine 111 (Cys111) located at the edge of the subunit interface. It also binds to Cu(2)-Zn(2) and Zn(2)-Zn(2) forms of hSOD1. Cisplatin inhibits aggregation of demetalated oxidized hSOD1, and it is further able to dissolve and monomerize oxidized hSOD1 oligomers in vitro and in cell, thus indicating its potential as a leading compound for amyotrophic lateral sclerosis.     

Projective spaces and inversive planes

In this paper, a common characterization of the finite projective space of dimension four and order \(n\) and of a finite inversive plane of order \(n+1\) in terms of regular \((k,n)\) finite planar spaces is given.

     

An approach to geometric interpolation by Pythagorean-hodograph curves

The problem of geometric interpolation by Pythagorean-hodograph (PH) curves of general degree n is studied independently of the dimension d????2. In contrast to classical approaches, where special structures that depend on the dimension are considered (complex numbers, quaternions, etc.), the basic algebraic definition of a PH property together with geometric interpolation conditions is used. The analysis of the resulting system of nonlinear equations exploits techniques such as the cylindrical algebraic decomposition and relies heavily on a computer algebra system. The nonlinear equations are written entirely in terms of geometric data parameters and are independent of the dimension. The analysis of the boundary regions, construction of solutions for particular data and homotopy theory are used to establish the existence and (in some cases) the number of admissible solutions. The general approach is applied to the cubic Hermite and Lagrange type of interpolation. Some known results are extended and numerical examples provided.     

Calcium copper-titanate thin film growth: tailoring of the operational conditions through nanocharacterization and substrate nature effects

A novel approach based on a molten multicomponent precursor source has been applied for the MOCVD fabrication of high-quality CaCu(3)Ti(4)O(12) (CCTO) thin films on various substrates. The adopted in situ strategy involves a molten mixture consisting of Ca(hfa)(2).tetraglyme, Ti(tmhd)(2)(O-iPr)(2), and Cu(tmhd)(2) [Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; tetraglyme = 2,5,8,11,14-pentaoxapentadecane; Htmhd = 2,2,6,6-tetramethyl-3,5-heptandione; O-iPr = isopropoxide] precursors. Film structural and morphological characterizations have been carried out by several techniques [X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM)], and in particular the energy filtered TEM mapping and X-ray energy dispersive (EDX) analysis in TEM mode provided a suitable correlation between nanostructural properties of CCTO films and deposition conditions and/or the substrate nature. Correlation between the nanostructure and optical/dielectric properties has been investigated exploiting spectroscopic ellipsometry.     

The determination of copper in silicon by anodic stripping and differential pulse voltammetry

A critical comparison of the application of differential pulse voltammetry and anodic stripping voltammetry to the determination of micro amounts of copper in silicon is described. The anodic stripping technique offers advantages when a dropping mercury capillary with a long drop time is used. The method recommended allows the determination of copper in silicon with a precision of ± 5 %; the limit of determination is about 1μg g^-1. Calibration graphs are linear in the range 0–0.2 μg Cu ml^-1. Methods for the dissolution of silicon are also compared.     

A facile synthesis of N-C linked 1,2,3-triazole-oligomers

The synthesis of the title oligomers was performed by means of an iterative sequence of 1,3-dipolar cycloaddition reactions of appropriate azides, starting from commercial 4-bromo-1-butyne as a key intermediate.     

Causal Non-Stationary Thermodynamics of Non-Viscous Heat Conducting Fluids with Internal Variables

Relativistic non-viscous heat conducting fluids with a vectorial internal variable are modeled according to the dissipation and causality principles. A set of constitutive equations, ensuring the causal nature of the model, is postulated. The second law of thermodynamics is exploited by analyzing a suitable covariant form of the Clausius–Duhem inequality. A modification of the classical theory of heat conduction, allowing a finite speed of propagation of thermal disturbances, is considered.