Design of catalytic processes based on studies of elementary processes

In the first part of the review, the personal reminiscences of the development period of organometallic chemistry are described referring to the unexpected discoveries of late transition metal alkyls through the effort of finding an active species involved in catalysis. The isolation and examination of the behavior of these transition metal complexes led to findings of elementary processes important in catalysis. In the second part of the account, applications of the newly found elementary processes to organic syntheses are described, with emphasis on the recent development of environmentally benign catalytic processes utilizing the concept of the C-O bond cleavage in carboxylic acid derivatives combined with other elementary processes. The recently developed catalytic processes include conversion of carboxylic anhydrides and acids into aldehydes, ketones, perfluoroketones, benzylation of olefins, and conversion of allylic formates into unsaturated carboxylic acids.     

Intra-spur positronic processes

Considering that Ps formation in condensed media has to take place in the teminal positron spur which, comprising many positive ions, provides a strong oxidizing environment for Ps, it is suggested that Ps formation via the epithemal process has to be mixed up with that of the spur process. Eventually in condensed media the observable aspect is those involving slowed down electrons and positron. When the size of the terminal positron spur is large, on the other hand, Ps via the epithermal process can survive. It appears to be possible to overcome the apparent inconsistency between the two models in this way. With this assumption admitted, we propose to investigate the intra-spur positronic processes in more detail. The spur process is an evolution of the energy level and the number of excess electrons, and Ps can be formed from various electron states in the course of the evolution: free excess electrons molecular anions, and excited molecular states. Ideas of Ps formation via resonant energy absorption and that involving vacancies are also presented. The importance of the non-exponential decay of o-Ps in the study of the positronic spur processes is also demonstrated with some recent results of scavenger effects.     

Electric-field-induced two-photon processes

In this paper we outline the novel features associated with two-photon processes in the presence of intense static electric fields. Both electrical polarisation effects and non-linear electro-optical effects are discussed, and their likely orders of magnitude estimated. It is illustrated how the interaction of the electric field with a molecular centre can lead to a relaxation of conventional two-photon selection rules, allowing spectroscopic access to otherwise forbidden excited states. Selection rules for the electro-optical channel are tabulated for some of the more common point groups.     

Nitroxide-mediated radical processes

In the present short review article recent achievements in nitroxide-mediated radical polymerizations are presented. The basic concept behind these reactions, which is the Persistent Radical Effect (PRE), will be briefly explained. The effect of the nitroxide structure on the polymerization process will be discussed. Moreover, results of nitroxide-mediated radical polymerizations in aqueous dispersions will be summarized. Finally, applications of the PRE to environmentally benign radical chemistry such as nitroxide-mediated alkoxyamine isomerization and carboaminoxylation reactions are presented. Moreover, the potential use of microwave-induced heating to conduct these thermal radical reactions will be discussed.     

Photochemical control of biological processes

Photochemical regulation of biological processes offers a high level of control to study intracellular mechanisms with unprecedented spatial and temporal resolution. This report summarizes the advances made in recent years, focusing predominantly on the in vivo regulation of gene function using irradiation with UV light. The majority of the described applications entail the utilization of photocaging groups installed either on a small molecule modulator of biomolecular function or directly on a biological macromolecule itself.     

Photophysical processes of 1,3-dicarbazolypropane

The photophysical processes of 1,3-dicarbazolypropane (DCZP), which possesses two fluorogen, carbazoly, and one carbonic chain composed of three carbon atoms, were studied. The formation of intermolecular excimer, intramolecular excimer and triple exciplexes have been investigated in the system of DCZP and 1,4-dinitrilebenzene (DNB) with steady state fluorescence spectroscopy. The experimental results show that with the addition of DNB into the lower concentration solution of DCZP in benzene, the fluorescence of intramolecular excimer of DCZP, (D-D)*, is quenched while the ((D-D)A)* type triple exciplex (one molecule of DCZP with one molecule of DNB) is formed and with the addition of DNB into higher concentration solution of DCZP, the formation of (DDA)* type triple exciplex (two molecules of DCZP with one molecule of DNB) is also confirmed.     

Eyring parameters of dehydration processes

Thermogravimetry was used in the study of the kinetics of dehydration of MnSO₄·5H₂O, CuSO₄·5H₂O and 3CdSO₄·8H₂O under static air atmosphere. The values of the kinetic and thermodynamic parameters for each stage of thermal dehydration were calculated from α(T) data by using the integral method, applying the Coats-Redfern approximation. The best model for all stages of dehydration is random nucleation model F1. The dependencies of enthalpy on entropy of activated complexes for different kinetic models were described. The linear relation was calculated between the Gibbs energy of activated complexes and the maximum dehydration rate temperature for analysed dehydration processes.     

Theory of non-Markovian rate processes

Starting from a multidimensional reaction kinetic equation with a general time evolution operator and a reaction sink function K, we derive formally exact expressions for the survival probability, reaction time distribution, and mean reaction time by using the projection operator technique. These rate expressions are given in the rational function form, with the irreducible memory function Omegairr as the key ingredient. This approach has an advantage over the direct perturbation approaches that use the reaction term as the small parameter, in that Omegairr has a structure that can be perturbatively treated with (K - K) as the small parameter. The well-known Wilemski-Fixman-type rate expressions are reproduced as the zeroth-order approximation from the present theory. Practical methods for evaluating the formal rate expressions are presented, and the results calculated for a model of electron transfer in non-Debye solvents are compared with computer simulations. It is found that the present approach is very promising for the study of non-Markovian dispersive kinetics.     

Path-integral computations of tunneling processes

The application of the path-integral methodology of Chandler and Wolynes [D. Chandler and P. G. Wolynes, J. Chem. Phys. 74, 4078 (1981)] to the calculation of one-electron-tunneling probabilities is revisited. We show that the evaluation of the kink free energy that is related to the tunneling splitting is associated with "polymer bead" distributions over a continuous distribution of scaled barriers, which makes both the calculation and its physical interpretation relatively difficult. In particular, we find that relative to other available techniques the method converges slowly and suffers from inaccuracies associated with the finite-temperature aspect of the calculation, and that past tentative identification of the bead distribution over the barrier with a physical picture of a "tunneling path" should be reassessed.     

Decomposition processes of nickel hydroxide

The dehydration processes of nickel hydroxide were studied by means of thermogravimetry in a temperature range from 300 to 900 K. The kinetics of the low-temperature dehydroxylation (≈300–600 K) was studied under non-isothermal conditions. A model-free method was used to calculate the activation energy and to analyze the stepwise checking; the non-linear regression method was applied to calculate the kinetic parameters of multi-stage decomposition reactions. The features of the dehydroxylation kinetics for the multi-stage process are explained by the formation and decomposition of hydrogel and xerogel phases.     

Theory of laser-simulated surface processes

Theoretical techniques for describing laser-stimulated surface processes in a vacuum and at a gas-surface interface are presented. For adspecies-surface systems, the laser excitation of vibrational degrees of freedom is considered, and quantum-mechanical and classical models and also an “almost first-principles” treatment of the competition between multiphoton absorption and multiphonon relaxation are discussed. The laser excitation of electronic degrees of freedom is considered with respect to surface states of semiconductors and metals, for the predissociation of diatomic adspecies on metal substrates, for ionization, and for resonance fluorescence of a gaseous atom near a metal. In connection with gas-surface interactions, the influence of laser radiation on diffraction patterns and energy transfer in atom-surface scattering is explored. Collisional ionization and ion neutralization in the presence of laser radiation are discussed. The roles of partial pressure and surface coverage in laser-stimulated surface processes are analyzed. Finally, some ideas on surface waves and annealing are presented.     

Kinetic theory of bridge processes

The detailed consideration of the kinetic aspect of the bridge process has allowed us to correctly write a kinetic equation beginning with knowledge of system microparameters. The solution of the equations makes it possible to elucidate the character of the relaxation process and to determine its typical constants as functions of those microparameters. Particular attention was given to kinetics in the presence of polaron effects. In this case the standard perturbation theory applied to derive the kinetic equations is not valid. The solutions obtained for this case are different both in the form of correlation functions and in the character of the interaction taken into account.     

EPR monitoring of sol-gel processes

Electron Paramagnetic Resonance (EPR) spectra of paramagnetic probes (free radical, 4-oxo-Tempo for non-doped glasses and vanadyl sulfate for doped silica glass) provide a non-intrusive means of monitoring of the dynamics of the sol-gel process. The free radical spectra parameters (rotation correlation time, isotropic hyperfine interaction parameter and line width) reflect changes in viscosity and polarity in the vicinity of the spin label. The EPR spectra of vanadyl can be used for monitoring the sol-gel process in that different types of mixed vanadyl complexes are formed during glass molding.     

Thermostable sulphocationites-catalysts of petrochemical processes

The results of tests on new thermostable sulphopolymer-based and aluminosilicate carrier-supported sulphocationites with conjugated bond systems, prepared in The Crude Oil and Gas Institute in Moscow, are presented. Their operating temperature is 280–350°C and they exhibit high catalytic activity in various petrochemical processes.

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Zusammenfassung Es wird über die Untersuchungsergebnisse von neuen hitzebeständigen Sulphokationiten mit konjugierten Bindungssystemen auf Sulphopolymerbasis und auf Aluminiumsilikat-Trägermaterial berichtet, die im Moskauer Institut für Rohöl und Erdgas hergestellt wurden. Wie festgestellt, weisen sie in verschiedenen petrochemischen Prozessen eine hochkatalytische Wirkung auf, ihre Funktionstemperatur liegt bei 280–350C.