Photochemistry of Dihydrido(hydrotris(3,5-dimethylpyrazolyl)borato)(Z-cyclooctene)iridium. Synthetic Intermediates and Mechanism of the Photochemical Formation of Hydridophenyl(hydrotris(3,5-dimethylpyrazolyl)borato)(trimethyl phosphite)iridium

The photolysis of a benzene solution of [Tp(Me2)IrH(2)(COE)], 1 (Tp(Me2) = hydrotris(3,5-dimethylpyrazolyl)borate, COE = Z-cyclooctene), in the presence of P(OMe)(3), gives the stable novel complex [Tp(Me2)IrH(C(6)H(5))(P(OMe)(3))], 3a. The photochemical syntheses of [Tp(Me2)IrH(2)(P(OMe)(3))], from 1 and P(OMe)(3) in diethyl ether, and [Tp(Me2)IrH(2)(CH(2)=CHCOO(t)Bu)], from 1 in tert-butyl acrylate, are also reported. The above reactions and several experiments using C(6)D(6) and P(OCD(3))(3) show that, in all cases, the primary photoproduct is the 16-electron, five-coordinate iridium(III) intermediate {Tp(Me2)IrH(2)}, 6a, produced by loss of COE from 1. The above experiments also allow the postulation of a mechanistic pathway for the formation of 3a which involves the oxidative addition of an aromatic C-H bond by 6a. Furthemore, the photochemical reaction of 1 in the presence of P(OCD(3))(3) shows that, under the reaction conditions used, oxidative addition of C-H bonds of P(OMe)(3) and of coordinated Tp(Me2)-ligands, presumably, to the intermediates 6a and {Tp(Me2)IrH(C(6)H(5))}, also occurs. Thus, coordinatively unsaturated iridium(III) species readily activate C-H bonds.     

NON-ENZYMIC METHODS FOR THE PHOSPHORYLATION OF PROTEINS1

Abstract

Non-enzymic methods for the phosphorylation of proteins are reviewed with respect to type of reagent, protein source, reactive site (N[sbnd], O[sbnd] or S[sbnd]), extent of reaction, and effect on physical properties, functionality and biological properties. Experimental procedures are given to illustrate the most important methods. Some enzymic methods are included for comparison. The evidence for phosphorylation of specific amino acid residues, such as serine, threonine, histidine or lysine, is critically assessed. Conclusions are drawn regarding the status of phosphorylation as a synthetic method for modifying proteins.     

Branched polymers from a double-scaling limit of matrix models

Multicritical potentials and correlation functions are given for models of rectangular M × N matrices, in the limit that N goes to infinity. These models are soluble without using orthogonal polynomials, and describe filamentary random surfaces, or, equivalently, a phase of branched polymers. It is shown that the equations describing multicritical behaviour are obtained from the hierarchy of flows that preserve Burgers' equation. Instanton solutions are studied - they imply that only the k = 2 model is unitary, and that the coefficients (for arbitrary k) of g_st^l is the perturbative expansion of the specific heat grow as l!.     

Preliminary evaluation of selected acoustic and glottographic measures for clinical phonatory function analysis

Acoustic and glottographic measures may provide important information that could enhance clinical management and documentation of vocal dysfunction. Acoustic measures such as jitter and shimmer reflect “short-term” perturbations, or instabilities of the voice, and the coefficients of variation for frequency and for amplitude reflect “long-term” perturbations. Interpretations of these acoustic measures are based on the assumption that vocal perturbations may be related to laryngeal tissue abnormalities, asymmetries in vocal fold movement, or neuromuscular fluctuations in the respiratory, laryngeal, or vocal tract systems. The abduction quotient is a glottographic measure related to laryngeal adduction and is obtained from an analysis of the electroglottograph signal. The adduction measure appears to be independent of the acoustic perturbation measures. Interpretations of the acoustic and adductory measures may, therefore, complement each other for greater understanding of a patient's laryngeal behavior. Visual displays of the acoustic and glottographic signals also are discussed to demonstrate their value in voice signal interpretations. Case studies illustrate potential interpretations of the acoustic perturbation and abduction quotient measures.     

Photochemistry of tris(pyrazolyl)borate titanium(IV) complexes

The electronic features and photochemistry of TpTiCl₃ (1) (Tp = hydrotris(pyrazol-1-yl)borate) and Tp*TiCl₃ (2) (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) were studied in THF. Reactive decay of the excited states produced either (or ) and metal center Ti(III) radicals via homolytic cleavage of the Tp → Ti (Tp* → Ti) bond. Cleavage of the Tp → Ti and the Tp* → Ti bond as a primary photoprocess is shown to be consistent with LMCT Tp → Ti and Tp* → Ti excitation. TpTiCl₂(THF) (3) and Tp*TiCl₂(THF) (4) were also prepared by stoichiometric reduction of 1 and 2 with Li₃N. The THF ligand in 3 and 4 was replaced by the stable nitroxyl radical TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) to provide the new complexes TpTiCl₂(TEMPO) (5) and Tp*TiCl₂(TEMPO) (6) in which the TEMPO ligand is η¹ coordinated to Ti(IV). Photolysis of 5 and 6 generate Ti(III) and the TEMPO radical in the primary photochemical step.     

CONDENSATION OF TETRAKIS(HYDROXYMETHYL)PHOSPHONIUM SULFATES AND SULFONATES WITH 1,3-DIMETHYLUREA

Abstract

An unexpected displacement of one of the phosphorus groups occurred when the chloride 1a was replaced by the sulfate 1b in its reactions with 1,3-dimethylurea. The products, 2c and 5c, were bisulfates rather than sulfates. In contrast, no displacement occurred when 1a was replaced by the sulfonates 1e or 1f. A method was developed for preparing the sulfonates 1d-h, all new compounds, by metathesis of the sulfate 1b with the appropriate barium sulfonate. The sulfates 2b and 5b, prepared from the chlorides 2a and 5a by ion exchange, yielded the bisulfates 2c and 5c upon treatment with sulfuric acid. The significance of the findings is discussed.     

Intertwining operators for solving differential equations,with applications to symmetric spaces

The use of intertwining operators to solve both ordinary and partial differential equations is developed. Classes of intertwining operators are constructed which transform between Laplacians which are self-adjoint with respect to different non-trivial measures. In the two-dimensional case, the intertwining operator transforms a non-separable partial differential operator to a separable one. As an application, the heat kernels on the rank 1 and rank 2 symmetric spaces are constructed.     

Does the topology of space fluctuate?

Evidence is presented that the singularities induced in causal Lorentzian spacetimes by changes in 3-space topology give rise to infinite particle and energy production under reasonable laws of quantum field propagation. In the case of the gravitational field, if 3-space is compact the total energy must vanish. A topological transition therefore induces a violent collapse that effectively aborts the transition, since the collapse mode is the only mode carrying the negative energy needed to compensate the associated infinite energy production. The existence of the Hamiltonian constraint of general relativity suggests that topological stability is a local property of the quantum theory that is maintained even when 3-space is noncompact.Supported in part by National Science Foundation Grant No. PHY-8318635.