117 research outputs found
TRIOSMIUM CLUSTER DERIVATIVES OF [60]FULLERENE
No full textTriosmium carbonyl cluster derivatives of [60]fullerene, Os-3(CO)(11)(eta(2)-C-60), OS3(CO)(10)(NCMe)(eta(2)-C-60), Os-3(CO)(10)(PPh(3))(eta(2)-C-60) and Os-3(CO)(9)(PPh(3))(2)(eta(2)-C-60) are described
Efficient and robust automated feature engineering
No full textThesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 59-61).Feature engineering is the key to building highly successful machine learning models. We present AutoFE, a system designed to automate feature engineering. AutoFE generates a large set of new interpretable features by combining information in the original features. Given an augmented dataset, it discovers a set of features that significantly improves the performance of any traditional classification using an evolutionary algorithm. We demonstrate the effectiveness and robustness of our approach by conducting an extensive evaluation on 8 datasets and 5 different classification algorithms. We show that AutoFE can achieve an average improvement in predictive performance of 25.24% for all classification algorithms over their baseline performance obtained with the original features..by Hyunjoon Song.M. Eng
Strong interfullerene electronic communication in a bisfullerene-hexarhodium sandwich complex
No full textReaction of Rh-6(CO)(12)(dPPM)(2) (dppm = 1,2-bis(diphenylphosphino) methane) with 1.4 equiv. of C-60 in chlorobenzene at 120 degreesC affords a face-capping C-60 derivative Rh-6(CO)(9)(dPPM)(2)(mu(3)-eta(2),eta(2),eta(2)-C-60) (1) in 73% yield. Treatment of 1 with excess CNR (10 equiv., R = CH2C6H5) at 80 degreesC provides a bisbenzylisocyanicle-substituted compound Rh-6(CO)(7)(dppm)(2)(CNR)(2)(mu(3)-eta(2),eta(2),eta(2)-C-60) (2) in 59% yield. Reaction of 1 with excess C-60 (4 equiv.) in refluxing chlorobenzene followed by treatment with 1 equiv. of CNR at room temperature gives a bisfullerene sandwich complex Rh-6(CO)(5)(dppm)(2)(CNR)(mu(3)-eta(2),eta(2),eta(2)-C-60)(2) (3) in 31% yield. Compounds 1, 2, and 3 have been characterized by spectroscopic and microanalytical methods as well as by X-ray crystallographic studies. Electrochemical properties of 1, 2, and 3 have been examined by cyclic voltammetry. The cyclic voltammograms (CVs) of 1 and 2 show two reversible one-electron redox waves, a reversible one-step two-electron redox wave, and a reversible one-electron redox wave, respectively, within the solvent cutoff window. This observation suggests that compounds 1 and 2 undergo similar C-60-localized electrochemical pathways up to 1(5-) and 2(5-). Each redox wave of 2 appears at more negative potentials compared to that of 1 because of the donor effect of the benzylisocyanide ligand. The CV of compound 3 reveals six reversible well-separated redox waves due to strong interfullerene electronic communication via the Rh-6 metal cluster bridge. The electrochemical properties of 1, 2, and 3 have been rationalized by molecular orbital calculations using the density functional theory (DFT) method. In particular, the molecular orbital (MO) calculation reveals significant contribution of the metal cluster center to the unoccupied molecular orbitals in 3, which is consistent with the experimental result of strong interfullerene electronic communication via the Rh-6 metal cluster spacer.K.L. thanks a Korea University Grant and
Center for Electro- and Photo-Responsive Molecules for financial support of this research. Y.S.L. thanks the support by Center
for Nanotubes and Nanostructured Composite and Center for Nanomechatronics and Manufacturing. J.T.P. thanks the National
Research Laboratory (NRL) Program of Korean Ministry of Science & Technology (MOST) and the Korea Science Engineering Foundation (Project No. 1999-1-122-001-5)
Reversible interconversion between mu,eta(2):eta(2)- and mu(3),eta(2):eta(2):eta(2)-C-60 on a carbido pentaosmium cluster framework
No full textDecarbonylation of Os-5(CO)(14)(PPh3) by 2 equiv of Me3NO/CH3CN at room temperature followed by reaction with C-60 in refluxing chlorobenzene produces Os5C(CO)(11)(PPh3)(mu (3),eta (2): eta (2):eta (2)-C-60) (1) in 44% yield. Thermal treatment of 1 at 80 degreesC under 1 atm of carbon monoxide affords Os5C(CO)(12)(PPh3)(mu,eta (2):eta (2)-C-60) (2) in good yield (72%). Upon thermolysis of 2 at 132 degreesC, 2 is cleanly reconverted to 1 (73%) by loss of a carbonyl ligand. Reaction of I with benzyl isocyanide at room temperature gives the addition product Os5C(CO)(11)(CNCH2C6H5)(PPh3)(mu (3),eta (2) :eta (2):eta (2):eta (2)-C-60) (3) in 85% yield. Thermolysis of 3 at 100 degreesC forms the isomeric Os5C(CO)(11)(CNCH2C6H5)(PPh3)(mu eta (2):eta (2)-C-60) (4) in 64% yield. Treatment of 4 with 1 equiv of Me3NO/ CH3CN at room temperature followed by heating at 132 degreesC in chlorobenzene gives Os5C(CO)(10)(CNCH2C6H5)(PPh3)(mu (3),eta (2):eta (2):eta (2)-C-60) (5) in 71% yield. Compound 5 can be alternatively prepared from the reaction of 1 with excess Ph3P=NCH2Ph at room temperature in 59% yield. Heating a chlorobenzene solution of 5 at 55 degreesC under 3 atm of carbon monoxide produces 4 as the only major product (16%). Treatment of Ru5C(CO)(11)(PPh3)(mu (3),eta (2):eta (2):eta (2)-C-60) (1') with benzyl isocyanide at room temperature forms Ru5C(CO)(11)(CNCH2C6H5)(PPh3)(mu (3),eta (2): eta (2):eta (2)-C-60) (3') in 90% yield. Reaction of 1' with benzyl isocyanide at a slightly elevated temperature of 40 degreesC affords Ru5C(CO)(10)(CNCH2C6H5)(PPh3)(mu (3),eta (2):eta (2):eta (2)-C-60) (5') in an almost quantitative yield of 96%. Compounds 1-5, 3', and 5', isolated as crystalline solids, have been characterized by microanalytical and spectroscopic methods. Molecular structures of 1-4 and 5' have been elucidated by X-ray crystallographic studies.We are grateful to the National Research Laboratory (NRL) Program of the Korean Ministry of Science & Technology (MOST) and theKorea Science and Engineering Foundation (Project No.1999-1-122-001-5) for financial support of this research
Electrochemical studies of C-60-triosmium complexes: First evidence for a C-60-mediated electron transfer to the metal center
No full textThe C-60-triosmium carbonyl complexes Os-3(CO)(11-n)(PPh3)(n)(eta(2)-C-60) [n = 0 (1), n = 1 (2), n = 2 (3)] have been studied by both cyclic voltammetric and IR spectroelectrochemical methods in a dichloromethane-toluene (4:1) solution. Both results suggest that a C-60-mediated electron transfer to the triosmium metal center takes place in these complexes. This is further confirmed by the synthesis and characterization of [NiCp2'](+)1(-) (Cp' = eta(5)-C5Me5). The three sequential one-electron reduction potentials of 1-3 are in the order of 1 > 2 > 3, respectively, due to the donor effect of the PPh3 ligand. Reduction is accompanied by loss of the C-60 moiety.We are grateful to both the Korea Science
and Engineering Foundation and the Korea Advanced Instituteof Science and Technology for financial support of this research
The first observation of four-electron reduction in [60]fullerene-metal cluster self-assembled monolayers (SAMs)
No full textSelf-assembled monolayers (SAMs) of mu(3)-eta(2):eta(2):eta(2)-C-60 triosmium cluster complex Os-3(CO)(8)(CN(CH2)(3)-Si(OEt)(3))(mu(3)-eta(2):eta(2):q2-C-60) (2) on ITO or An surface exhibit ideal, well-defined electrochemical responses and remarkable electrochemical stability being reducible up to tetraanionic species in their cyclic voltammograms.This work was supported by the National Research Laboratory (NRL) Program of the Korean Ministry of Science & Technology (MOST) and the Korea Science & Engineering
Foundation (Project No. 1999-1-122-001-5)
Synthesis and characterization of eta(2)-C-60 and mu(3)-eta(2),eta(2),eta(2)-C-60 triosmium cluster complexes
No full textVarious eta(2)-C-60 and mu(3)-eta(2),eta(2),eta(2)-C-60 triosmium carbonyl cluster complexes Os-3(CO)(11)(eta(2)-C-60) (1), Os-3(CO)(10)(NCMe)(eta(2)-C-60) (2), Os-3(CO)(10)(PPh3)(eta(2)-C-60) (3), Os-3(CO)(9)(PR3)(2)(eta(2)-C-60) (4, R = Ph; 5, R = Me), Os-3(CO)(9)(mu(3)-eta(2),eta(2),eta(2)-C-60) (6), and Os-3(CO)(8)(PMe3)(mu(3)-eta(2),eta(2),eta(2)-C-60) (7) have been isolated as crystalline solids and characterized by spectroscopic (IR, MS, and H-1, P-31, and C-13 NMR) and analytical data. The molecular structure of complex 1 has been determined by a single-crystal X-ray diffraction study. The structure of 1 is derived from that of Os-3(CO)(12) by replacing an equatorial carbonyl ligand with an eta(2)-C-60 ligand coordinated through a 6-6 ring fusion. The structural assignment of 2-7 is made on the basis of spectroscopic results. Compound 2 exists as two isomers in solution in a ratio of 2:1 (2a: 2b). VT C-13 NMR spectra of 2a and 5 indicate that both complexes undergo similar fluxional processes of restricted equilibration of in-plane equatorial C-60 and carbonyl ligands via a triply bridged intermediate with identical values of Delta G(c)(not equal) = 12.7 +/- 0.1 kcal/mol. Thermolysis of 2 in refluxing chlorobenzene affords Os-3(CO)(9)(mu(3)-eta(2),eta(2),eta(2)-C-60) (6) in 23% yield, which can be alternatively prepared in 32% yield from the reaction of Os-3(CO)(10)(NCMe)(2) (2 equiv) and C-60 (1 equiv). Decarbonylation of 6 with Me3NO/MeCN reagent in the presence of excess PMe3 gives Os-3(CO)(8)(PMe3)(mu(3)-eta(2),eta(2),eta(2)-C-60) (7) in a quantitative yield. VT C-13 NMR spectra of both 6 and 7 reveal a localized-3-fold rotation of carbonyl and phosphine ligands on each osmium center.We are grateful to the Korea Advanced Institute of Science and Technology for financial support of this research
Artificial Control of Cell Signaling Using a Photocleavable Cobalt(III)-Nitrosyl Complex
No full textCells use gaseous molecules such as nitric oxide (NO) to transmit both intracellular and intercellular signals. In principle, the endogenous small molecules regulate physiological changes, but it is unclear how randomly diffusive molecules trigger and discriminate signaling programs. Herein, it is shown that gasotransmitters use time-dependent dynamics to discriminate the endogenous and exogenous inputs. For a real-time stimulation of cell signaling, we synthesized a photo-cleavable metal-nitrosyl complex, [Co-III(MDAP)(NO)(CH3CN)](2+) (MDAP=N,N '-dimethyl-2,11-diaza[3,3](2,6)pyridinophane), which can stably deliver and selectively release NO with fine temporal resolution in the cytosol, and used this to study the extracellular signal-regulated kinases (ERKs), revealing how cells use both exogenous and endogenous NO to disentangle cellular responses. This technique can be to understand how diverse cellular signaling networks are dynamically interconnected and also to control drug delivery systems
Rh(0)/Rh(III) core-shell nanoparticles as heterogeneous catalysts for cyclic carbonate synthesis
No full textRh(0)/Rh(III) core-shell nanoparticles were prepared by surface oxidation of Rh nanoparticles with N-bromosuccinimide. They were employed as heterogeneous catalysts for cyclic carbonate synthesis from propylene oxide and CO2, and exhibited high activity and excellent recyclability due to Lewis acidic Rh(III) species on the shells
© The Royal Society of Chemistry 20171331sciescopu
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