Malcolm L. H. Green

Bio: Malcolm L. H. Green is an academic researcher from University of Oxford. The author has contributed to research in topics: Carbon nanotube & Cyclopentadienyl complex. The author has an hindex of 82, co-authored 800 publications receiving 31121 citations. Previous affiliations of Malcolm L. H. Green include Gas Technology Institute & University of Illinois at Urbana–Champaign.

Synthesis and reactions of binuclear molybdenocene and tungstenocene derivatives

Abstract: The tetramer [{Mo(η-C5H5)2HLi}4] reacts with N2O giving the yellow dimers cis- and trans-[{Mo(η-C5H5)H}2-(µ-σ : η-C5H4)2]. These thermally rearrange to the green dimer [{Mo(η-C5H5)H}2(µ-η5-C5H4-η5-C5H4)]. Protonation of the latter gives [{Mo(η-C5H5)H}2(µ-H)(µ-η5-C5H4-η5-C5H4)][PF6]. Photolysis of [Mo-(η-C5H5)2H2] or the yellow dimers gives a red dimer [{Mo(η-C5H5)}2(µ-σ : η5-C5H4)2]. Prolonged treatment of the four neutral dimers with aqueous acid gives [{Mo(η-C5H5)}2(µ-H)(µ-OH)(µ-η5-C5H4-η5-C5H4)][PF6]2. The red and yellow dimers react with iodine giving [{Mo(η-C5H5)I}2(µ-σ : η5-C5H4)2] and the corresponding reaction with the green dimer yields [{Mo(η-C5H5)I}2(µ-η5-C5H4-η5-C5H4)]. The red dimer also adds to methyl bromide giving [{Mo(η-C5H5)Me}{Mo(η-C5H5)Br}(µ-σ : η5-C5H4)2], whereas the yellow dimer reacts with methyl iodide to give [{Mo(η-C5H5)}2(µ-σ : η5-C5H4)2]. Photolysis of [W(η-C5H5)2H2] in diethyl ether gives cis- and trans-[{W(η-C5H5)H}2(µ-σ : η5-C5H4)2] and the cation [W(η-C5H5)2(η-C2H4)H]+. Thermal decomposition of [W(η-C5H5)2MeH] in cyclohexane gives isomers of the compound [{W(η-C5H5)2Me}{W(η-C5H5)H}-(µ-σ : η5-C5H4)2].

High-resolution electron microscopy of tubule-containing graphitic carbon

Abstract: Carbon extracted from a cathodic graphite rod following arc-discharge in helium is examined using high-resolution electron microscopy. It is found that, in addition to the well known extended graphitic tubules (‘buckytubes’), carbon produced in this way contains many other novel graphitic structures. Of particular interest are small hollow particles which, although essentially tubular, appear to differ in significant ways from the extended tubules. Evidence for tetrahedral bonding in some of the graphitic particles is also presented.

Some organic chemistry of molybdenum and related topics

Abstract: General features of molybdenum chemistry are briefly surveyed and then three areas of molybdenum chemistry are presented in more detail. Evidence concerning the structure and bonding in bent bis it-cyclopentadienyl metal compounds is discussed. New reactions of bis It-cyclopentadienyl molybdenum (and tungsten) complexes are described: in particular the reactions of the dihydride (ic-C5H5)2MoH2 leading to molybdenum aryl derivatives. Arene molybdenum chemistry has been explored and the arene—metal bond has been found to survive in a wide variety of chemical environments. INTRODUCTION The organometallic chemistry of molybdenum started in the mid-1950s and most of the early compounds were carbonyl derivatives. This was largely due to the availability of molybdenum hexacarbonyl together with its ease of handling. These carbonyl derivatives were usually prepared by thermal substitution: nL + Mo(CO)6 -* LMo(CO)6 By this route molybdenum was bonded to arenes, azulenes, t-cyclopentadienyl and to many olefm ligands such as cycloheptatriene and bicycloheptadiene. Many of these compounds were important since they often provided the first examples of a particular organometal system at a time when it was by no means clear what were the limits of stability of organometal bonds. Two other early compounds of interest were the his t-cyclopentadienylmolybdenum dihydride and bis t-benzene molybdenum. Much of this early work was done in the laboratories of Fischer and Wilkinson1. The second phase of organomolybdenum chemistry largely concerned the development and study of arene molybdenum carbonyls, and, especially, of it-cyclopentadienyl molybdenum carbonyl chemistry. The ic-C5H5Mo(CO)3X system has been shown to provide a wide range of derivatives where for example, X = aIkyl2, acyl3, aryl4, perfluoroalkyl5, sulphinato6, silyl7, stannyl8, germyl9 and other metal ligands with aluminium10, magnesium1 1, palladium and platinum'2. Also, the substitution properties of itC5H5Mo(CO)3X by ligands such as nitrosyls'3, polypyrazolylborates'4, phosphines and phosphites have been studied1 5• Several molybdenum compounds containing 2 x le 'carbene' ligands have been described16, and ligands which contribute three electrons to the molybdenum have been found in the compounds it-C5H5Mo(CO)2D, D = 7r-allyl'7. benzyP8. 373

Highly hydrophilic and stable polypeptide/single-wall carbon nanotube conjugates

Abstract: A polymeric dispersing agent for single-wall carbon nanotubes (SWCNTs) in water was synthesized by 4-(pyren-1-yl)butanoylation of the amine groups of poly-L-lysine. The pyrene content of 4-(pyren-1-yl)butanoylated polylysine (PBPL) was optimized so that a maximal dispersion effect of the SWCNTs was obtained. High molecular weight PBPL (>300000 g mol−1) exceeds the widely used surfactant sodium dodecylsulfate (SDS) as a dispersing agent yielding a 27% higher SWCNT concentration in dispersion. The high stability of the PBPL/SWCNT conjugates is demonstrated by removing the conjugates from dispersion through filtration, washing, and redispersion in only water. The resulting redispersions do not contain free PBPL and the importance of having SWCNT dispersions in the absence of free dispersing agent is discussed. For SDS dispersions, poor redispersion properties have been observed. The binding of PBPL onto the SWCNTs was studied by atomic force microscopy, optical absorbance spectroscopy, and fluorescence spectroscopy.

Structure and Dynamics of a Dihydrogen/Hydride Ansa Molybdenocene Complex

Abstract: In contrast to [Cp(2)MoH(3)](+), which is a thermally stable trihydride complex, the ansa-bridged analogue [(eta-C(5)H(4))(2)CMe(2)MoH(H(2))](+) (1) is a thermally labile dihydrogen/hydride complex. Partial deuteration of the hydride ligands allows observation of J(H)(-)(D) = 11.9 Hz in 1-d(1) and 9.9 Hz in 1-d(2) (245 K), indicative of a dihydrogen/hydride structure. There is a slight preference for deuterium to concentrate in the dihydrogen ligand. A rapid dynamic process interchanges the hydride and dihydrogen moieties in complex 1. Low temperature (1)H NMR spectra of 1 give a single hydride resonance, which broadens at very low temperature due to rapid dipole-dipole relaxation (T(1) = 23 ms (750 MHz, 175 K) for the hydride resonance in 1). Low temperature (1)H NMR spectra of 1-d(2) allow the observation of decoalescence at 180 K into two resonances. The bound dihydrogen ligand exhibits hindered rotation with DeltaG(150) = 7.4 kcal/mol, but H atom exchange is still rapid at all accessible temperatures (down to 130 K). Density functional calculations confirm the dihydrogen/hydride structure as the ground state for the molecule and give estimates for the energy of two hydrogen exchange processes in good agreement with experiment. The presence of the C ansa bridge is shown to decrease the ability of the metallocene fragment to donate to the hydrogens, thus stabilizing the (eta(2)-H(2)) unit and modulating the barrier to H(2) rotation.

Single-shell carbon nanotubes of 1-nm diameter

Abstract: CARBON nanotubes1 are expected to have a wide variety of interesting properties. Capillarity in open tubes has already been demonstrated2–5, while predictions regarding their electronic structure6–8 and mechanical strength9 remain to be tested. To examine the properties of these structures, one needs tubes with well defined morphologies, length, thickness and a number of concentric shells; but the normal carbon-arc synthesis10,11 yields a range of tube types. In particular, most calculations have been concerned with single-shell tubes, whereas the carbon-arc synthesis produces almost entirely multi-shell tubes. Here we report the synthesis of abundant single-shell tubes with diameters of about one nanometre. Whereas the multi-shell nanotubes are formed on the carbon cathode, these single-shell tubes grow in the gas phase. Electron diffraction from a single tube allows us to confirm the helical arrangement of carbon hexagons deduced previously for multi-shell tubes1.

Chemistry and properties of nanocrystals of different shapes.

Abstract: The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Carbon Nanotubes: Present and Future Commercial Applications

Abstract: Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.

Nanoparticle therapeutics: an emerging treatment modality for cancer

Abstract: Nanoparticles — particles in the size range 1–100 nm — are emerging as a class of therapeutics for cancer. Early clinical results suggest that nanoparticle therapeutics can show enhanced efficacy, while simultaneously reducing side effects, owing to properties such as more targeted localization in tumours and active cellular uptake. Here, we highlight the features of nanoparticle therapeutics that distinguish them from previous anticancer therapies, and describe how these features provide the potential for therapeutic effects that are not achievable with other modalities. While large numbers of preclinical studies have been published, the emphasis here is placed on preclinical and clinical studies that are likely to affect clinical investigations and their implications for advancing the treatment of patients with cancer.

Chemistry of Carbon Nanotubes

Abstract: Department of Materials Science, University of Patras, 26504 Rio Patras, Greece, Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, 116 35 Athens, Greece, Institut de Biologie Moleculaire et Cellulaire, UPR9021 CNRS, Immunologie et Chimie Therapeutiques, 67084 Strasbourg, France, and Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa 1, 34127 Trieste, Italy