Inorg Chem
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA.
Published: November 2012
The calcium metallacrown Ca(II)[15-MC(Cu(II)N(Trpha))-5](2+) was obtained by self-assembly of Ca(II), Cu(II), and tryptophanhydroxamic acid. Its X-ray structure shows that the core calcium ion is well-encapsulated in the five oxygen cavity of the metallacrown scaffold. The kinetics of Ca-Ln core metal substitution was studied by visible spectrophotometry by addition of Ln(III) nitrate to solutions of Ca(II)[15-MC(Cu(II)N(Trpha))-5](2+) in methanol solution at pH 6.2 (Ln(III) = La(III), Nd(III), Gd(III), Dy(III), Er(III)) to obtain the corresponding Ln(III)[15-MC(Cu(II)N(Trpha))-5](3+) complexes on the hours time scale. The reaction is first order in the two reactants (second order overall) with different rate constants across the lanthanide series. In particular, the rate for the Ca-Ln substitution decreases from La(III) to Gd(III) and then increases slightly from Gd(III) to Er(III). This substitution reaction occurs with second order rate constants ranging from 0.1543(3) M(-1) min(-1) for La(III) to 0.0720(6) M(-1) min(-1) for Gd(III). By means of the thermodynamic log K constants for the same reaction previously reported, the rate constants for the inverse Ln-Ca substitution were also determined. In this study, we demonstrated that the substitution reaction proceeds through a direct metal substitution and does not involve the disassembly of the MC scaffold. These observations in concert allow the proposition of a hypothesis that the dimension of the core metals play the major role in determining the rate constants of the substitution reaction. In particular, the largest lanthanides, which do not require complete encapsulation in the MC cavity, displace the Ca(II) ion faster, whereas in the back reaction Ca(II) displaces the smaller lanthanides faster as they interact relatively weakly with the metallacrown oxygen cavity.
Download full-text PDF |
Source |
---|---|
http://dx.doi.org/10.1021/ic3013798 | DOI Listing |
Surg Pract Sci
March 2023
UT Health San Antonio, Long School of Medicine, San Antonio, TX, United States.
Objective: To apply a normalized competitive index over a 20-year period to analyse applicant trends in orthopaedic surgery residency programs.
Design: A retrospective analysis of orthopaedic surgery residency program data from the National Resident Matching Program (NRMP) Main Residency Match data from 2003 to 2022 and NRMP Charting Outcomes data from 2007 to 2021 was performed. A competitive index (CI) was utilized by dividing the number of programs ranked per applicant, multiplied by available positions, and by the match rate for each year.
Heliyon
January 2025
Department of Mechanical Engineering, Faculty of Engineering, Arak University, Arak 38156-88349, Iran.
This research presents a numerical study over the unsteady natural convection of an electrically conducting fluid in an open-ended vertical parallel plate microchannel under uniform and asymmetric heat flux subjected to a uniform lateral magnetic field. Slip velocity, as well as temperature jump at channel walls, are modeled using a first-order model. The effects of Knudsen number)(, heat flux ratio)rq(, Grashof number)(, and Hartmann number)M(on mass flow rate, the maximum temperature of the wall, and average Nusselt () as a function of time are discussed.
View Article and Find Full Text PDFACS Appl Mater Interfaces
January 2025
Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
Advanced carbon-metal hybrid materials with controllable electronic and optical properties, as well as chemical reactivities, have attracted significant attention for emerging applications, including energy conversion and storage, catalysis and environmental protection. However, the commercialization of these materials is hampered by several vital problems, including energy-intensive synthesis and expensive chemicals, and inefficient control of their structures and properties. Herein, we report the simple and controllable engineering of nanocarbon-metal self-assembled silver nanocatalysts (SSNs) derived from polycarbonate (PC)-based optical discs using microplasmas under ambient conditions.
View Article and Find Full Text PDFInt J Biol Macromol
January 2025
College of Food and Bioengineering, Zhengzhou University of Light Industry, Zhengzhou 450001, PR China; Key Laboratory of Cold Chain Food Processing and Safety Control (Zhengzhou University of Light Industry), Ministry of Education, Zhengzhou 450001, PR China. Electronic address:
Oral fast dissolving films represent a novel dosage form for probiotics. To reduce the dependence of film preparation on synthetic materials, a polysaccharide-based oral fast dissolving nanofilm for probiotics was fabricated through pullulan (PUL) electrospinning. An electrospinnability map of PUL with varying physical properties was developed, identifying a molecular weight of 200 kDa and a concentration of 20 % as suitable conditions for achieving favorable fiber morphology.
View Article and Find Full Text PDFJ Colloid Interface Sci
January 2025
School of Environmental and Chemical Engineering, Jiangsu Ocean University, Lianyungang 222000, PR China. Electronic address:
Metal-organic frameworks (MOFs) have shown significant potential in the photocatalytic activation of peroxydisulfate (PDS). Although many MOFs have been investigated for their ability to activate PDS, the impact of structural interpenetration on this process remains underexplored. In this study, MIL-88D(FeNi) and MIL-126(FeNi) were selected to systematically study this effect.
View Article and Find Full Text PDFEnter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!
© LitMetric 2025. All rights reserved.