Study of the thermal decomposition on Pt(II) complexes with cycloalkanespiro-5′-hydantoins

The thermal decomposition of the Pt(II) complexes with cyclobutane-and cycloheptanespiro-5′-hydantoins were studied by TG and DTA techniques. The Pt(II) complex with cyclobutanespiro-5′hydantoin (PtCBH) was stable up to 115°C (388 K) and Pt(II) complex with cycloheptanespiro-5′-hydantoin (PtCHTH) was stable up to 150°C (423 K). After the thermal decomposition of PtCBH the solid residue was platinum, while the decomposition of PtCHTH gave a mixture of platinum carbides (PtC₂, Pt₂C₃).     

Neutrino oscillations in the sun and the205Tl solar neutrino experiment

Neutrino induced transition rates from²⁰⁵Tl to excited states in²⁰⁵Pb were calculated for neutrino fluxes from the different hydrogen burning reactions in the sun. Suppression factors for electron neutrinos due to flavor oscillations in the sun were obtained. The influence of neutrino oscillations on the neutrino capture rate of²⁰⁵Tl in dependence of the mixing angle and neutrino mass difference is discussed.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday     

Thermo-programmed reduction study of Pt/WO<Subscript>x</Subscript>–ZrO<Subscript>2</Subscript> materials by thermogravimetry

The thermo-programmed reduction study of Pt/WO_x–ZrO₂ materials prepared with different tungsten loading were performed by thermogravimetry. The samples were synthesized by impregnation method and calcined at 600, 700 and 800°C. The characterizations of both un-calcined and calcined materials were carried out using different techniques: thermal analysis (TG and DTA), X-ray diffraction (XRD) and thermo-programmed reduction (TPR). TG and DTA analysis of un-calcined were used to determination of calcination temperatures of the samples. XRD diffractograms were useful to help us in the determination of phase presents. TPR profiles showed between three and four events at different temperatures attributed to platinum reduction and the different stages of tungsten specie reduction.     

Facile Fabrication of Well‐Dispersed Pt Nanoparticles in Mesoporous Silica with Large Open Spaces and Their Catalytic Applications

In this paper, a facile strategy is reported for the preparation of well‐dispersed Pt nanoparticles in ordered mesoporous silica (Pt@OMS) by using a hybrid mesoporous phenolic resin‐silica nanocomposite as the parent material. The phenolic resin polymer is proposed herein to be the key in preventing the aggregation of Pt nanoparticles during their formation process and making contributions both to enhance the surface area and enlarge the pore size of the support. The Pt@OMS proves to be a highly active and stable catalyst for both gas‐phase oxidation of CO and liquid‐phase hydrogenation of 4‐nitrophenol. This work might open new avenues for the preparation of noble metal nanoparticles in mesoporous silica with unique structures for catalytic applications.     

A 31P NMR STUDY OF TERTIARY PHOSPHINE COMPLEXES OF PLATINUM(II) AND PALLADIUM(II)

Complexes of the type NBu ₄ MCl ₃ PR ₃ R=P.Tolyl,Ph,Bu) (M = Pt, Pd) are prepared by the reaction of MCl ₂ or K ₂ [MCl ₄ ] by phosphine ligands. Addition of NBu ₄ Br or NBu ₄ I to these compounds, in dichloromethane results in a redistribution of halogens and formation of all six isomers of the type MBr _{3 ?X}Cl_XPR ₃ X= 0, 1, 2, and 3 which have been identified by ³¹ P- ¹ H NMR spectroscopy. The intensities show that the products are proportional to the statistical distribution.     

Effects of intramolecular hydrogen bonds on phosphorescence emission: A theoretical perspective

Importing intramolecular hydrogen bond in phosphorescent transition metal complexes has been considered one of the excellent approaches to improve the electroluminescence performance of organic light-emitting diodes in real applications. However, the relationships between such H-bond structure and phosphorescent properties have not been theoretically revealed yet. In this study, two types of intramolecular hydrogen bonds are introduced into the two classes of traditional materials, that is, Pt(II) and Ir(III) complexes ( 1a and 2a ) to completely elucidate their influence on the structures and properties by comparing with the original phosphors ( 1b and 2b ) using density functional theory/time-dependent density functional theory for the first time. A comprehensive analysis of the geometric structures, molecular orbitals, and luminescence properties (including phosphorescence emission wavelengths and radiative and nonradiative decay processes) has been carried out. Our theoretical model highlights that complexes 1a and 2a embedded with H-bonds significantly promote the phosphorescence emission band blue-shifted and restrict molecular deformations compared with the corresponding 1b and 2b , which can provide helpful guidance to regulate and design several aspects of highly efficient blue phosphorescent emitters.     

Crystal structure of K[PtCl3(caffeine)] and its interactions with important nitrogen-donor ligands

The crystal structure of K[PtCl₃(caffeine)] was determined. The coordination geometry around platinum is square-planar formed by N9 of the caffeine ligand and three Cl^? ions. The bond lengths and angles of K[PtCl₃(caffeine)] were compared with those reported for [PtCl₃(caffeine)]^? and K[PtCl₃(theobromine)]. At the level of the statistical significance of the data we have compared, no differences in the bond distances and angles for any of these compounds were noticed. Weak interactions between K⁺ and Cl^? are responsible for the formation of 1-D polymeric chains in the crystal structure of the complex. The interactions of K[PtCl₃(caffeine)] with inosine (Ino) and guanosine-5′-monophosphate (5′-GMP) were studied by ¹H NMR spectroscopy at 295 K in D₂O in a molar ratio of 1 : 1. The results indicate formation of the reaction product [PtCl₃(Nu)] (Nu=Ino or 5′-GMP) with the release of caffeine from the coordination sphere of the starting complex. The higher stability of the bond between the Pt(II) ion and Ino or 5′-GMP compared to the stability of the platinum–caffeine bond is confirmed by density functional theory calculations (B3LYP/LANL2DZp) using as models 9-methylhypoxanthine and 9-methylguanine.