Binary Dioxygen Complexes of Nickel, Palladium, and Platinum, M(O2) and (O2)M(O2), in Low Temperature Matrices

1973 ◽  
Vol 51 (16) ◽  
pp. 2722-2736 ◽  
Author(s):  
H. Huber ◽  
W. Klotzbücher ◽  
G. A. Ozin ◽  
A. Vander Voet
Keyword(s):  
Positive Charge ◽  
Isotopic Substitution ◽  
Normal Coordinate ◽  
Gaseous Oxygen ◽  
Warm Up ◽  
Partial Positive Charge ◽  
Diffusion Controlled ◽  
Bond Stretching ◽  
Bond Strengths ◽  
And Diffusion

The cocondensation reactions of nickel, palladium, and platinum atoms with gaseous oxygen or dilute oxygen–argon mixtures at 4.2–10 °K give rise to binary transition metal dioxygen complexes. Variable concentration and diffusion controlled warm up studies, 16O/18O isotopic substitution studies, normal coordinate and isotope intensity calculations establish the complexes to be of the types M(O2) and (O2)M(O2). Both the mono- and bisdioxygen complexes contain the dioxygen molecules coordinated to the metal atom in a side-on fashion, with a unique D2d "spiro"-type structure favored for the bis-complexes. Frequency and bond stretching force constant trends within the series of complexes are examined and suggest that the O—O and M—O values increase with increasing coordination number, and thus with an increase in partial positive charge on the metal. This trend in O—O stretching frequencies is not in accord with the evaluation of metal–dioxygen bond strengths as based on the degree of reversibility of dioxygen coordination.

Binary Mixed Dinitrogen–Carbonyl Complexes of Nickel(0), Ni(N2)m(CO)4−m (where m = 1–3)

1973 ◽  
Vol 51 (16) ◽  
pp. 2737-2746 ◽  
Author(s):  
E. P. Kündig ◽  
M. Moskovits ◽  
G. A. Ozin
Keyword(s):  
Dipole Moments ◽  
Force Constants ◽  
Carbonyl Complexes ◽  
Transition Dipole ◽  
Warm Up ◽  
Vibrational Assignments ◽  
Diffusion Controlled ◽  
Transition Dipole Moments ◽  
Bond Stretching ◽  
Bonding Properties

Nickel atoms have been cocondensed in various 12C16O/14N2, 12C16O/14N2/Ar, and 12C18O/14N2/15/N2/Ar matrices and the infrared and Raman spectra of the products recorded at 4.2–10 °K. In addition to the infrared absorptions associated with the known compounds Ni(N2)4 and Ni(CO)4, other NN and CO stretching modes are observed which can be ascribed to the mixed carbonyl–dinitrogen species Ni(N2)m (CO)4−m where m = 1–3. Confirmation of the molecular constitutions and vibrational assignments of the isolated species was obtained from (a) variable concentration experiments in which either N2 or CO was arranged to be in excess, (b) diffusion controlled warm-up experiments in the range 10–35 °K, and (c) isotope substitution experiments using 14N2/15N2/12C18O/Ar matrices in which the total nitrogen to carbon monoxide ratio was varied. Cotton–Kraihanzel kCO and kNN force constants are computed for the mixed compounds Ni(CO)3(N2), Ni(CO)2(N2)2, and Ni(CO)(N2)3 and trends within the series are discussed in terms of the σ-donor and π-acceptor bonding properties of the N2 and CO ligands. An analysis is presented in which the changes in the CO and N2 bond stretching force constants in passing from Ni(CO)m to Ni(CO)m(N2)4−m and from Ni(N2)4−m to Ni(CO)m(N2)4−m are related to the change in σ and π orbital populations. The results of that analysis indicate that CO is both a better σ donor and a better π acceptor than N2. Integrated absorbances of the bands associated with the species Ni(CO)m(N2)4−m are measured and are used to compute ratios of the transition dipole moments (μco′)m and [Formula: see text] for CO and N2 respectively. The observed trends for (μco′)m and [Formula: see text] as functions of m are found to be in keeping with the changes in the respective CO and N2 π orbital populations.

Binary Dioxygen Complexes of Nickel; Infrared Spectroscopic Evidence for Ni(O2) and (O2)Ni(O2) in Low Temperature Matrices

1972 ◽  
Vol 50 (22) ◽  
pp. 3746-3747 ◽  
Author(s):  
H. Huber ◽  
G. A. Ozin
Keyword(s):  
Low Temperature ◽  
Transition Metal ◽  
Nickel Atom ◽  
Isotope Substitution ◽  
Warm Up ◽  
Spectroscopic Evidence ◽  
Variable Concentration ◽  
Diffusion Controlled ◽  
Argon Matrices ◽  
And Diffusion

The cocondensation reaction of nickel atoms with oxygen or dilute oxygen–argon matrices at 4.2–10 °K gives rise to the first examples of binary transition metal dioxygen complexes. Variable concentration and diffusion controlled warm up studies and 16O2, 16O18O, 18O2 isotope substitution studies establish the stoichiometries of the dioxygen complexes of nickel to be Ni(O2) and (O2)Ni(O2). Both complexes have the dioxygen molecule(s) coordinated to the nickel atom in a "sideways" fashion.

Vacancy-Mediated Diffusion and Diffusion-Controlled Processes in Ordered Binary Intermetallics by Kinetic Monte Carlo Simulations

2021 ◽  
Vol 29 ◽  
pp. 95-115
Author(s):  
Rafal Kozubski ◽  
Graeme E. Murch ◽  
Irina V. Belova
Keyword(s):  
Monte Carlo ◽  
Kinetic Monte Carlo ◽  
Simulation Studies ◽  
Self Diffusion ◽  
Monte Carlo Techniques ◽  
Diffusion Controlled ◽  
Kinetic Monte Carlo Simulations ◽  
Kinetic Effects ◽  
Kinetics Of ◽  
And Diffusion

We review the results of our Monte Carlo simulation studies carried out within the past two decades in the area of atomic-migration-controlled phenomena in intermetallic compounds. The review aims at showing the high potential of Monte Carlo methods in modelling both the equilibrium states of the systems and the kinetics of the running processes. We focus on three particular problems: (i) the atomistic origin of the complexity of the ‘order-order’ relaxations in γ’-Ni3Al; (ii) surface-induced ordering phenomena in γ-FePt and (iii) ‘order—order’ kinetics and self-diffusion in the ‘triple-defect’ β-NiAl. The latter investigation demonstrated how diverse Monte Carlo techniques may be used to model the phenomena where equilibrium thermodynamics interplays and competes with kinetic effects.

scholarly journals Electrochemical Behaviour of N′-(p-toluenesulphonyl)-3-methyl-4-(4′-substituted arylhydrazono) pyrazolin-5-ones

2012 ◽  
Vol 9 (4) ◽  
pp. 1864-1874
Author(s):  
V. Nagaraju ◽  
R. Sreenivasulu ◽  
P. Venkata Ramana
Keyword(s):  
Electrochemical Behaviour ◽  
Reduction Process ◽  
Effect Of Solvent ◽  
Buffer Solutions ◽  
Diffusion Controlled ◽  
Controlled Potential Electrolysis ◽  
Dc Polarography ◽  
Controlled Potential ◽  
Ph Range ◽  
And Diffusion

The electrochemical behaviour of N′-(p-toluenesulphonyl)-3-methyl-4-(4′-substituted arylhydrazono) pyrazolin-5-ones has been investigated at dme and gc electrodes in buffer solutions of pH 2.0, 4.0, 6.0, 8.0 and 10.0 using dc polarography and cyclic voltammetry and coulometry. The compounds exhibit one well defined wave in the entire pH range of study. The process is irreversible and diffusion controlled. Controlled potential electrolysis indicates the involvement of four electrons in the reduction process. The effect of solvent, cations and anions, temperature and substitutents on the mechanism of reduction has been studied. Based on the results obtained the mechanism of reduction has been suggested.

Refinement of Size Distributions for Primary Crystallizations

1997 ◽  
Vol 481 ◽  
Author(s):  
E. Pineda ◽  
T. Pradell ◽  
D. Crespo ◽  
N. Clavaguera ◽  
J. ZHU ◽  
...  
Keyword(s):  
Grain Size ◽  
Metastable Phase ◽  
Primary Crystallization ◽  
Controlled Growth ◽  
Diffusion Controlled ◽  
Average Grain Size ◽  
Soft Impingement ◽  
Single Grain ◽  
Kinetics Of ◽  
And Diffusion

ABSTRACTThe microstructure developed in primary crystallizations is studied under realistic conditions. The primary crystallization of an amorphous alloy is modeled by considering the thermodynamics of a metastable phase transition and the kinetics of nucleation and crystal growth under isothermal annealing. A realistic growth rate, including an interface controlled growth at the beginning of the growth of each single grain and diffusion controlled growth process with soft impingement afterwards is considered. The reduction in the nucleation rate due to the compositional change in the remaining amorphous matrix is also taken into account. The microstructures developed during the transformation are obtained by using the Populational KJMA method, from the above thermodynamic and kinetic factors. Experimental data of transformed fraction, grain density, average grain size, grain size distribution and other related parameters obtained from annealed metallic glasses are modeled.

scholarly journals Viscoadaptation controls intracellular reaction rates in response to heat and energy availability

2019 ◽  
Author(s):  
Laura Persson ◽  
Vardhaan S. Ambati ◽  
Onn Brandman
Keyword(s):  
Cellular Response ◽  
Reaction Rates ◽  
Acute Response ◽  
Cellular Environment ◽  
Diffusion Controlled ◽  
Intracellular Diffusion ◽  
Response To Temperature ◽  
And Diffusion ◽  
Tunable Property ◽  
Multiple Conditions

Summary/AbstractCells must precisely orchestrate thousands of reactions in both time and space. Yet reaction kinetics are highly dependent on uncontrollable environmental conditions such as temperature. Here, we report a novel mechanism by which budding yeast influence reaction rates through adjustment of intracellular viscosity. This “viscoadaptation” is achieved by production of two carbohydrates, trehalose and glycogen, which combine to create a more viscous cellular environment in which biomolecules retain solubility. We demonstrate that viscoadaptation functions as both an acute response to temperature increase as well as a homeostatic mechanism, allowing cells grown at temperatures spanning from 22°C to 40°C to maintain equivalent rates of intracellular diffusion and diffusion-controlled chemical reactions. Multiple conditions that lower ATP trigger viscoadaptation, suggesting that viscoadaptation may be a general cellular response to low energy. Viscoadaptation reveals viscosity to be a tunable property of cells through which they can regulate diffusion-controlled processes dynamically in response to a changing environment.

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