scholarly journals The influence of the cationic carbenes on the initiation kinetics of ruthenium-based metathesis catalysts; a DFT study

2018 ◽  
Vol 14 ◽  
pp. 2872-2880 ◽  
Author(s):  
Magdalena Jawiczuk ◽  
Angelika Janaszkiewicz ◽  
Bartosz Trzaskowski
Keyword(s):  
Positive Charge ◽  
Water Soluble ◽  
Free Energies ◽  
Environment Friendly ◽  
Ancillary Ligands ◽  
Grubbs Catalysts ◽  
Bond Strengths ◽  
Metathesis Catalysts ◽  
Kinetics Of ◽  
Rare Group

Cationic carbenes are a relatively new and rare group of ancillary ligands, which have shown their superior activity in a number of challenging catalytic reactions. In ruthenium-based metathesis catalysis they are often used as ammonium tags, to provide water-soluble, environment-friendly catalysts. In this work we performed computational studies on three cationic carbenes with the formal positive charge located at different distances from the carbene carbon. We show that the predicted initiation rates of Grubbs, indenylidene, and Hoveyda–Grubbs-like complexes incorporating these carbenes show little variance and are similar to initiation rates of standard Grubbs, indenylidene, and Hoveyda–Grubbs catalysts. In all investigated cases the partial charge of the carbene carbon atom is similar, resulting in comparable Ccarbene–Ru bond strengths and Ru–P/O dissociation Gibbs free energies.

Structural analogues of Hoveyda–Grubbs catalysts bearing the 1-benzofuran moiety or isopropoxy-1-benzofuran derivatives as olefin metathesis catalysts

RSC Advances ◽  
2016 ◽  
Vol 6 (26) ◽  
pp. 21423-21429 ◽  
Author(s):  
B. Trzaskowski ◽  
K. Ostrowska
Keyword(s):  
Olefin Metathesis ◽  
Computational Method ◽  
Free Energies ◽  
Grubbs Catalysts ◽  
Structural Analogues ◽  
Metathesis Catalysts ◽  
Derivatives Of

We have used the DFT/M06-D3 computational method to study structures and activation free energies for a series of Hoveyda–Grubbs-like catalysts with the isopropoxybenzene part replaced by 1-benzofuran and ten derivatives of isopropoxy-1-benzofuran.

Kinetics-Based Modeling of Bond-Metal Dissolution and IMC During Soldering

2006 ◽  
Author(s):  
Mohammad Faizan ◽  
Guo-X. Wang
Keyword(s):  
Intermetallic Phase ◽  
Molten Solder ◽  
Lead Free ◽  
Joint Interface ◽  
Environment Friendly ◽  
Soldering Process ◽  
Substrate Dissolution ◽  
Soldering Reaction ◽  
Lead Free Solders ◽  
Kinetics Of

Soldering has become an indispensable joining process in the electronic packaging industry. The industry is aiming for the use of environment friendly lead-free solders. All the lead-free solders are high tin-containing alloys. During the soldering process, an intense interaction of metallization on PCB and tin from the solder occurs at the metallization/solder interface. Intermetallic compound (IMC) is formed at the interface and subsequently PCB bond-metal (substrate) is dissolved into the molten solder. In the present study the terms bond-metal and substrate will be used interchangeably and the term 'substrate' refers to the top layer of the PCB which comes in contact with the molten solder during soldering reaction. Thickness of the intermetallic phase formed at the joint interface and amount of substrate lost is critical in achieving reliable solder joints. During the wet phase of soldering process, the IMC does not grow as layered structure; rather it takes the shape of scallops. The growth of scalloped IMC during the solder/substrate interaction entails complicated physics. Understanding of the actual kinetics involved in the formation of IMC phase is important in controlling the process to achieve desired results. This paper presents theoretical analysis of the kinetics involved in the formation of the scalloped intermetallic phase. The intermetallic phase growth is experimentally investigated to support the underlying kinetics of the process. Numerical model has been suggested to translate the physics of the process. The model is based on the basic mass diffusion equations and can predict the substrate dissolution and IMC thickness as a function of soldering time.

Model for Epitaxial growth of Cobalt on CU(100)

1989 ◽  
Vol 160 ◽  
Author(s):  
Dimitri D. Vvedensky ◽  
Shaun Clarke
Keyword(s):  
Epitaxial Growth ◽  
Growth Kinetics ◽  
Solid Model ◽  
Free Energies ◽  
Diffusion Parameters ◽  
The Difference ◽  
Kinetics Of

AbstractThe epitaxial growth kinetics of Co on Cu(100) are investigated with a kinetic solid-on-solid model. Two effects are found to dominate the growth of this system reflecting the difference in surface free energies betweenthe two materials: the difference of diffusion parameters, and the inability of Co to wet Cu(100) at lower temperatures.

scholarly journals Mixing state and compositional effects on CCN activity and droplet growth kinetics of size-resolved CCN in an urban environment

2012 ◽  
Vol 12 (21) ◽  
pp. 10239-10255 ◽  
Author(s):  
L. T. Padró ◽  
R. H. Moore ◽  
X. Zhang ◽  
N. Rastogi ◽  
R. J. Weber ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Water Soluble ◽  
Anthropogenic Sources ◽  
Droplet Growth ◽  
Mixing State ◽  
Aerosol Composition ◽  
Activation Kinetics ◽  
Aerosol Mixing State ◽  
Kinetics Of ◽  
Ccn Activity

Abstract. Aerosol composition and mixing state near anthropogenic sources can be highly variable and can challenge predictions of cloud condensation nuclei (CCN). The impacts of chemical composition on CCN activation kinetics is also an important, but largely unknown, aspect of cloud droplet formation. Towards this, we present in-situ size-resolved CCN measurements carried out during the 2008 summertime August Mini Intensive Gas and Aerosol Study (AMIGAS) campaign in Atlanta, GA. Aerosol chemical composition was measured by two particle-into-liquid samplers measuring water-soluble inorganic ions and total water-soluble organic carbon. Size-resolved CCN data were collected using the Scanning Mobility CCN Analysis (SMCA) method and were used to obtain characteristic aerosol hygroscopicity distributions, whose breadth reflects the aerosol compositional variability and mixing state. Knowledge of aerosol mixing state is important for accurate predictions of CCN concentrations and that the influence of an externally-mixed, CCN-active aerosol fraction varies with size from 31% for particle diameters less than 40 nm to 93% for accumulation mode aerosol during the day. Assuming size-dependent aerosol mixing state and size-invariant chemical composition decreases the average CCN concentration overprediction (for all but one mixing state and chemical composition scenario considered) from over 190–240% to less than 20%. CCN activity is parameterized using a single hygroscopicity parameter, κ, which averages to 0.16 ± 0.07 for 80 nm particles and exhibits considerable variability (from 0.03 to 0.48) throughout the study period. Particles in the 60–100 nm range exhibited similar hygroscopicity, with a κ range for 60 nm between 0.06–0.076 (mean of 0.18 ± 0.09). Smaller particles (40 nm) had on average greater κ, with a range of 0.20–0.92 (mean of 0.3 ± 0.12). Analysis of the droplet activation kinetics of the aerosol sampled suggests that most of the CCN activate as rapidly as calibration aerosol, suggesting that aerosol composition exhibits a minor (if any) impact on CCN activation kinetics.

scholarly journals Positive charge of “sticky” peptides and proteins impedes release from negatively charged PLGA matrices

2015 ◽  
Vol 3 (23) ◽  
pp. 4723-4734 ◽  
Author(s):  
Stephen C. Balmert ◽  
Andrew C. Zmolek ◽  
Andrew J. Glowacki ◽  
Timothy D. Knab ◽  
Sam N. Rothstein ◽  
...  
Keyword(s):  
Positive Charge ◽  
Release Kinetics ◽  
P Release ◽  
Kinetics Of

Release kinetics of biomolecules (agents) encapsulated in negatively charged PLGA matrices are slowed by positive charge on the agents.

In Situ Electrochemical Study of Copper Nanoparticles Stabilized with Food Grade Gelatin

2016 ◽  
Vol 705 ◽  
pp. 163-167 ◽  
Author(s):  
Ellaine M. Datu ◽  
Mary Donnabelle L. Balela
Keyword(s):  
Electroless Deposition ◽  
Reduction Rate ◽  
In Situ Monitoring ◽  
Mixed Potential ◽  
Cu Nanoparticles ◽  
Environment Friendly ◽  
Food Grade ◽  
Alternative Material ◽  
Kinetics Of

Commercially available conductive inks are typically made up of precious metal nanoparticles, such as gold (Au) and silver (Ag). Thus, cheaper metals like copper (Cu) are currently being explored as alternative material. Though Cu has a comparable conductivity to that of Ag, they tend to oxidize easily when exposed to air and water, which could limit their application. In this work, oxidation-stable Cu nanoparticles with mean diameter as small as 57 nm were prepared by simple electroless deposition in water. Food-grade gelatin was used as stabilizer, which makes the process more economical and environment-friendly. In situ monitoring of mixed potential was carried out during synthesis to understand the kinetics of the reaction. The mixed potential of the solution shifted negatively as the amount of gelatin was increased. This suggests faster reduction rate.

Solution Kinetics of a Water-Soluble Hydrocortisone Prodrug: Hydrocortisone-21-lysinate

1985 ◽  
Vol 74 (1) ◽  
pp. 87-89 ◽  
Author(s):  
Kevin Johnson ◽  
Gordon L. Amidon ◽  
Stefano Pogany
Keyword(s):  
Water Soluble ◽  
Kinetics Of ◽  
Solution Kinetics
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