Single and double Suzuki-Miyaura couplings with symmetric dihalobenzenes

[reaction: see text] m- or p-Diiodobenzene undergoes selective double coupling reactions with arylboronic acids and esters. Selectivity for double coupling over single coupling is remarkably strong: even with a diiodobenzene:monoboronic acid ratio of 10:1, the products of double coupling are formed in good yields. Steric hindrance and electronic influences of the boronic acid or ester, and reaction conditions do not appear to impact significantly upon the outcome of the reaction. In contrast, m- and p-dibromobenzenes undergo single couplings with aryl boronic acids with high selectivity.     

Analytical applications of β-heteropoly acids : This influlsnce of complexing agents on selective formation

An explanation is given of the apparently paradoxical behaviour of heteropoly acids in the presence of organic complexing agents such as tartaric acid, and methods for selective formation of particular heteropoly acids are suggested. Sensitive and rapid methods for the determination of silicate and phosphate in the presence of each other are described.     

THE TRIPLET AND RADICAL SPECIES OF HAEMATOPORPHYRIN AND SOME OF ITS DERIVATIVES

Abstract— Nanosecond laser flash photolysis and pulse radiolysis have been used to generate and characterise the triplet state, and semioxidised and semireduced radicals of haematoporphyrin, and three 0 -acyl compounds derived from it (the monoacetate, the diacetate and the disuccinate).
After 347 nm irradiation in water containing 2% Triton X-100, haematoporphyrin forms the triplet state (φ_T= 0.92) and photoionises monophotonically (φ_I= 0.03). For the O -acyl derivatives, φ_T approaches unity and photoionisation is reduced. In acetone the triplet yield of all four compounds are close to unity. The difference and corrected spectra for the triplet species are presented and decay rates ( k ₁˜10⁴s^-1) and oxygen quenching constants ( k _Q˜1.5times10⁹ M ^-1s^-1) for the triplet state have been measured. The difference and corrected spectra for the semi-reduced species in methanol and semi-oxidised species in aqueous Triton X-100 are presented.
The photophysical characteristics in fluid solution of haematoporphyrin and its 0 -acyl derivatives are rather similar to those previously recorded for other photosensitising porphyrins.     

Radiochemical fire-assay for determination of the platinum group elements

The radioactive study of Ni–NiS bead fire-assay followed by neutron activation analysis showed nearly quantitative collection of the platinum group elements and gold in the bead. However, there was clearly some loss of gold and ruthenium at the dissolution and filtration stage. A preliminary study of the radiochemical fire-assay method indicates that the technique could overcome the problem of losses. Chemical carrier behaves in the same way as platinum metal concentrate during the analytical procedure and could be used to evaluate yields during each determination. When applied to rock samples, the radiochemical fire-assay gives good sensitivity and could be applied to the determination of nanogram concentrations of the platinum group elements without the problem of high blank values from reagents.     

Peripherally Substituted Phthalocyanines

Peripherally substituted phthalocyanine (Pc) systems render more accessible the desirable properties of the Pc system, i.e., high thermal and oxidative stability as well as significant complexity ability of transition metals. After brief examination of existing synthetic methods, two new routes to substitution of the peripheral protons of the Pc system are described: (1) directed metalation of the Pc system itself followed by derivatization, and (2) directed metalation of phthalonitrile followed by derivatization and Pc formation. Each of these methods is further distinguished by providing exclusively substitution at the a-positions of the Pc nucleus. Several of the compounds have been isolated and characterized using the techniques of HPLC; ¹H, ¹³C, and ²⁹Si NMR; and mass spectroscopy. These multisubstituted Pc systems are much more soluble in organic solvents than is the parent system. Such soluble macromolecules are of interest to the energy research community because of a variety of possible applications, notably the preparation of sensors, electrode coatings, catalysts, and soluble oxygen transports.     

Spatial mixing and nonlocal Markov chains

We consider spin systems with nearest‐neighbor interactions on an n‐vertex d‐dimensional cube of the integer lattice graph . We study the effects that the strong spatial mixing condition (SSM) has on the rate of convergence to equilibrium of nonlocal Markov chains. We prove that when SSM holds, the relaxation time (i.e., the inverse spectral gap) of general block dynamics is O(r), where r is the number of blocks. As a second application of our technology, it is established that SSM implies an O(1) bound for the relaxation time of the Swendsen‐Wang dynamics for the ferromagnetic Ising and Potts models. We also prove that for monotone spin systems SSM implies that the mixing time of systematic scan dynamics is . Our proofs use a variety of techniques for the analysis of Markov chains including coupling, functional analysis and linear algebra.