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Mingfei Zhou - One of the best experts on this subject based on the ideXlab platform.
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infrared photodissociation spectroscopic and theoretical study of heteronuclear transition Metal Carbonyl cluster cations in the gas phase
Journal of Physical Chemistry A, 2016Co-Authors: Fanchen Kong, Guanjun Wang, Mingfei ZhouAbstract:Heteronuclear transition Metal Carbonyl cluster cations FeM(CO)8+ (M = Co, Ni and Cu) and MCu(CO)7+ (M = Co and Ni) are produced via a laser vaporization supersonic cluster ion source in the gas phase, which are each mass-selected and studied by infrared photodissociation spectroscopy in the Carbonyl stretching frequency region. Their geometric and electronic structures are established by comparison of the experimental spectra with those derived from density functional theoretical calculations. The FeM(CO)8+ (M = Co, Ni, Cu) complexes are determined to have eclipsed (CO)5Fe–M(CO)3+ structures, and the MCu(CO)7+ (M = Co, Ni) ions are characterized to have staggered (CO)4M–Cu(CO)3+ structures. Natural bonding orbital analysis indicates that the positive charge is mainly distributed on the M(CO)3 fragment. The Metal–Metal interaction involves an σ-type (OC)4,5M→M(CO)3+ dative bonding.
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Infrared Photodissociation Spectroscopic and Theoretical Study of Heteronuclear Transition Metal Carbonyl Cluster Cations in the Gas Phase
2016Co-Authors: Fanchen Kong, Guanjun Wang, Mingfei ZhouAbstract:Heteronuclear transition Metal Carbonyl cluster cations FeM(CO)8+ (M = Co, Ni and Cu) and MCu(CO)7+ (M = Co and Ni) are produced via a laser vaporization supersonic cluster ion source in the gas phase, which are each mass-selected and studied by infrared photodissociation spectroscopy in the Carbonyl stretching frequency region. Their geometric and electronic structures are established by comparison of the experimental spectra with those derived from density functional theoretical calculations. The FeM(CO)8+ (M = Co, Ni, Cu) complexes are determined to have eclipsed (CO)5Fe–M(CO)3+ structures, and the MCu(CO)7+ (M = Co, Ni) ions are characterized to have staggered (CO)4M–Cu(CO)3+ structures. Natural bonding orbital analysis indicates that the positive charge is mainly distributed on the M(CO)3 fragment. The Metal–Metal interaction involves an σ-type (OC)4,5M→M(CO)3+ dative bonding
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spectroscopic and theoretical investigations of vibrational frequencies in binary unsaturated transition Metal Carbonyl cations neutrals and anions
Chemical Reviews, 2001Co-Authors: Mingfei Zhou, Lester Andrews, Charles W BauschlicherAbstract:Figure 18 presents the C-O stretching vibrational frequencies of the first-row transition-Metal monoCarbonyl cations, neutrals, and anions in solid neon; similar diagrams have been reported for neutral MCO species in solid argon, but three of the early assignments have been changed by recent work and one new assignment added. The laser-ablation method produces mostly neutral atoms with a few percent cations and electrons for capture to make anions; in contrast, thermal evaporation gives only neutral species. Hence, the very recent neon matrix investigations in our laboratory provide Carbonyl cations and anions for comparison to neutrals on a level playing field. Several trends are very interesting. First, for all Metals, the C-O stretching frequencies follow the order cations > neutrals > anions with large diagnostic 100-200 cm-1 separations, which is consistent with the magnitude of the Metal d to CO pi * donation. Second, for a given charge, there is a general increase in C-O stretching vibrational frequencies with increasing Metal atomic number, which demonstrates the expected decrease in the Metal to CO pi * donation with increasing Metal ionization potential. Some of the structure in this plot arises from the extra stability of the filled and half-filled d shell and from the electron pairing that occurs at the middle of the TM row; the plot resembles the "double-humped" graph found for the variation in properties across a row of transition Metals. For the anions, the variation with Metal atom is the smallest since all of the Metals can easily donate charge to the CO ligand. Third, for the early transition-Metal Ti, V, and Cr families, the C-O stretching frequencies decrease when going down the family, but the reverse relationship is observed for the late transition-Metal Fe, Co, and Ni families. In most of the present discussion, we have referred to neon matrix frequencies; however, the argon matrix frequencies are complementary, and useful information can be obtained from comparison of the two matrix hosts. In most cases, the neon-to-argon red shift for neutral Carbonyls is from 11 to 26 cm-1, but a few (CrCO) lie outside of this range. In the case of FeCO and Fe(CO)2, it appears that neon and argon trap different low-lying electronic states. In general, the Carbonyl neutrals and anions have similar shifts but Carbonyl cations have larger matrix shifts. For example, the FeCO+ fundamental is at 2123.0 cm-1 in neon and 2081.5 cm-1 in argon, a 42.5 cm-1 shift, which is larger than those found for FeCO- (11.7 cm-1) and FeCO (11.7 cm-1). It is unusual for different low-lying electronic states to be trapped in different matrices, but CUO provides another example. The linear singlet state (1047.3, 872.2 cm-1) is trapped in solid neon, and a calculated 1.2 kcal/mol higher triplet state is trapped in solid argon (852.5, 804.3 cm-1) and stabilized by a specific interaction with argon. The bonding trends are well described by theoretical calculations of vibrational frequencies. Table 5 compares the scale factors (observed neon matrix/calculated) for the C-O stretching modes of the monoCarbonyl cations, neutrals, and anions of the first-row transition Metals observed in a neon matrix using the B3LYP and BP86 density functionals. Most of the calculated Carbonyl harmonic stretching frequencies are within 1% of the experimental fundamentals at the BP86 level of theory, while calculations using the B3LYP functional give frequencies that are 3-4% higher as expected for these density functionals and calculations on saturated TM-Carbonyls. For second- and third-row Carbonyls using the BP86 density functional and the LANL effective core potential in conjunction with the DZ basis set, the agreement between theory and experiment is just as good. For example, the 16 M(CO)1-4 neutral and anion and 2 MCO+ cation (M = Ru, Os) Carbonyl frequencies are fit within 1.5%. The 16 species (M = Rh, Ir) are fit within 1%, but the Rh(CO)1-4+ calculations are 2-3% too low and Ir(CO)1-4+ computations are 1-2% too low. In addition to predicting the vibrational frequencies, DFT can be used to calculate different isotopic frequencies, and isotopic frequency ratios can be computed as a measure of the normal vibrational mode in the molecule for an additional diagnostic. For diatomic CO, the 12CO/13CO ratio 1.0225 and C16O/C18O ratio 1.0244 characterize a pure C-O stretching mode. In a series of molecules such as RhCO+, RhCO, and RhCO-, where the Metal-CO bonding varies, the Rh-C, C-O vibrational interaction is different and the unique isotopic ratios for the Carbonyl vibration are characteristic of that particular molecule. Table 6 summarizes the isotopic ratios observed and calculated for the RhCO+,0,- species. Note that RhCO+ exhibits slightly more carbon-13 and less oxygen-18 involvement in the C-O vibration than CO itself and that this trend increases to RhCO and to RhCO- as the Rh-C bond becomes shorter and stronger. Note also how closely the calculated and observed ratios both follow this trend. In a molecule with two C-O stretching modes, for example, bent Ni(CO)2 exhibits a strong b2 mode at 1978.9 cm-1 and a weak a1 mode at 2089.7 cm-1 in solid neon, and these two modes involve different C and O participations. The symmetric mode shows substantially more C (1.0242) and less O (1.0217) participation than does the antisymmetric mode with C (1.0228) and O (1.0238) involvement, based on the given isotopic frequency ratios, which are nicely matched by DFT calculations (a1 1.0244, 1.0224 and b2 1.0232, 1.0241, respectively). These investigations of vibrational frequencies in unsaturated transition-Metal Carbonyl cations, neutrals, and anions clearly demonstrate the value of a close working relationship between experiment and theory to identify and characterize new molecular species.
Christoph Janiak - One of the best experts on this subject based on the ideXlab platform.
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the use of microwave irradiation for the easy synthesis of graphene supported transition Metal nanoparticles in ionic liquids
Carbon, 2011Co-Authors: Dorothea Marquardt, Engelbert Redel, Ralf Thomann, Christian Vollmer, Peter Steurer, Rolf Mulhaupt, Christoph JaniakAbstract:Abstract Stable ruthenium or rhodium Metal nanoparticles were supported on chemically derived graphene (CDG) surfaces with small and uniform particle sizes (Ru 2.2 ± 0.4 nm and Rh 2.8 ± 0.5 nm) by decomposition of their Metal Carbonyl precursors by rapid microwave irradiation in a suspension of CDG in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate. The graphene-supported hybrid nanoparticles were shown to be active and could be re-used at least 10 times as catalysts for the hydrogenation of cyclohexene and benzene under organic-solvent-free conditions with constant activities up to 1570 mol cyclohexane × (mol Metal) −1 × h −1 at 4 bar and 75 °C.
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microwave irradiation for the facile synthesis of transition Metal nanoparticles nps in ionic liquids ils from Metal Carbonyl precursors and ru rh and ir np il dispersions as biphasic liquid liquid hydrogenation nanocatalysts for cyclohexene
Chemistry: A European Journal, 2010Co-Authors: Christian Vollmer, Engelbert Redel, Ralf Thomann, Khalid Abushandi, Haresh Manyar, Christopher Hardacre, Christoph JaniakAbstract:Stable chromium, molybde- num, tungsten, manganese, rhenium, ruthenium, osmium, cobalt, rhodium, and iridium Metal nanoparticles (M- NPs) have been reproducibly obtained by facile, rapid (3 min), and energy- saving 10 W microwave irradiation (MWI) under an argon atmosphere from their Metal-Carbonyl precursors (Mx(CO)y) in the ionic liquid (IL) 1- butyl-3-methylimidazolium tetrafluoro- borate ((BMIm)A4)). This MWI syn- thesis is compared to UV-photolytic (1000 W, 15 min) or conventional ther- mal decomposition (180-2508C, 6- 12 h) of (Mx(CO)y) in ILs. The MWI- obtained nanoparticles have a very small (< 5 nm) and uniform size and are prepared without any additional stabilizers or capping molecules as long-term stable M-NP/IL dispersions (characterization by transmission elec- tron microscopy (TEM), transmission electron diffraction (TED), and dy- namic light scattering (DLS)). The ruthenium, rhodium, or iridium nano- particle/IL dispersions are highly active and easily recyclable catalysts for the biphasic liquid-liquid hydrogenation of cyclohexene to cyclohexane with activi- ties of up to 522 (mol product)A Ru) 1 h 1 and 884 (mol product)A Rh) 1 h 1 and give almost quantitative conversion within 2 h at 10 bar H2 and 908C. Catalyst poisoning experiments with CS2 (0.05 equiv per Ru) suggest a heterogeneous surface catalysis of Ru- NPs.
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use of ionic liquids ils for the il anion size dependent formation of cr mo and w nanoparticles from Metal Carbonyl m co 6 precursors
Chemical Communications, 2008Co-Authors: Engelbert Redel, Ralf Thomann, Christoph JaniakAbstract:Stable chromium, molybdenum and tungsten nanoparticles are obtained reproducibly by thermal or photolytic decomposition under argon from mononuclear Metal Carbonyl precursors M(CO)6 (M = Cr, Mo, W) suspended in the ionic liquids BMim+BF4−, BMim+OTf− and BtMA+Tf2N− (BMim+ = n-butyl-methyl-imidazolium, BtMA+ = n-butyl-trimethyl-ammonium, Tf2N = N(O2SCF3)2, OTf = O3SCF3) with a very small and uniform size of 1 to 1.5 nm in BMim+BF4− which increases with the molecular volume of the ionic liquid anion to ∼100 nm in BtMA+Tf2N− [characterization by transmission electron microscopy (TEM), dynamic light scattering and transmission electron diffraction (TED) analysis].
Malini Olivo - One of the best experts on this subject based on the ideXlab platform.
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a transition Metal Carbonyl probe for use in a highly specific and sensitive sers based assay for glucose
Journal of the American Chemical Society, 2013Co-Authors: Kien Voon Kong, Zhiyong Lam, Weber Kam On Lau, Weng Kee Leong, Malini OlivoAbstract:A triosmium Carbonyl cluster–boronic acid conjugate is used as a secondary carbohydrate probe in a SERS-based assay. The assay does not require conjugation of the Metal Carbonyl probe to a SERS-active species, and it utilizes the CO stretching vibrations of the Metal Carbonyl, which lies in a silent region of the SERS spectrum (1800–2200 cm–1), for quantification. High selectivity for glucose over fructose and galactose is obtained, and a human urine sample doped with glucose is detected accurately.
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Metal Carbonyl gold nanoparticle conjugates for live cell sers imaging
Angewandte Chemie, 2012Co-Authors: Kien Voon Kong, Zhiyong Lam, Weng Kee Leong, Malini Olivo, Wenda Douglas GohAbstract:Conjugates of organoMetallic osmium Carbonyl clusters and gold nanoparticles show a strong Carbonyl signal in surface-enhanced Raman spectroscopy. The ease of bio-functionalization and the high stability and good dispersibility in aqueous solution make these conjugates excellent candidates for biomedical applications, as demonstrated by live-cell imaging with the Carbonyl signals of OM-NP(PEG)-L conjugates.
Pradip K Mascharak - One of the best experts on this subject based on the ideXlab platform.
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design strategies to improve the sensitivity of photoactive Metal Carbonyl complexes photocorms to visible light and their potential as co donors to biological targets
Accounts of Chemical Research, 2014Co-Authors: Indranil Chakraborty, Samantha J Carrington, Pradip K MascharakAbstract:ConspectusThe recent surprising discovery of the beneficial effects of carbon monoxide (CO) in mammalian physiology has drawn attention toward site-specific delivery of CO to biological targets. To avoid difficulties in handling of this noxious gas in hospital settings, researchers have focused their attention on Metal Carbonyl complexes as CO-releasing molecules (CORMs). Because further control of such CO delivery through light-triggering can be achieved with photoactive Metal Carbonyl complexes (photoCORMs), we and other groups have attempted to isolate such complexes in the past few years.Typical Metal Carbonyl complexes release CO when exposed to UV light, a fact that often deters their use in biological systems. From the very beginning, our effort therefore was directed toward identifying design principles that could lead to photoCORMs that release CO upon illumination with low-power (5–15 mW/cm2) visible and near-IR light. In our work, we have utilized Mn(I), Re(I), and Ru(II) centers (all d6 ground...
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photoactive Metal Carbonyl complexes as potential agents for targeted co delivery
Journal of Inorganic Biochemistry, 2014Co-Authors: Margarita A Gonzales, Pradip K MascharakAbstract:Abstract The surprising discovery of carbon monoxide (CO) as a signaling molecule in mammalian physiology has recently raised interest in this toxic gas among researchers in biochemical and pharmaceutical community. CO is endogenously produced mainly from catabolism of heme by the enzyme heme oxygenase (HO) and participates in a myriad of anti-inflammatory, anti-proliferative, and vasoregulatory pathways. In animal models, low doses of CO have exhibited beneficial effects in suppression of organ graft rejection and safeguarding the heart during reperfusion after cardiopulmonary bypass surgery. The salutary effects of CO have naturally drawn attention of the pharmaceutical industry for its use as a cytoprotective agent. Safety-related concerns of the use of this noxious gas have prompted research in the area of syntheses of CO-releasing molecules (CORMs) and to date, several Metal Carbonyls (Metal complexes of CO) have been employed as CORMs in promoting prolonged (and safe) delivery of low doses of CO to cellular targets. Because many Carbonyl complexes release CO upon illumination, investigators have recently began to explore the possibility of “controlled CO delivery” through the use of light. During the past few years, a number of photoactive CORMs or “photoCORMs” have been synthesized that release CO upon illumination with UV or visible light. The utility of these photoCORMs in CO delivery has also been confirmed. Novel design principles for isolation of photoCORMs have started to appear in recent reports. Scrutiny of the literature reveals the emergence of a new exciting area of drug development in such efforts. The potential of photoCORMs as CO-donating pharmaceuticals along with a brief overview of the physiological roles of CO is presented in this review.
Stefano Zacchini - One of the best experts on this subject based on the ideXlab platform.
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using Metal Carbonyl clusters to develop a molecular approach towards Metal nanoparticles
European Journal of Inorganic Chemistry, 2011Co-Authors: Stefano ZacchiniAbstract:This microreview aims at presenting a personal perspective on the possible contributions of molecular Metal Carbonyl clusters (MCCs) to a better understanding and development of Metal nanoparticles. High-nuclearity molecular MCCs are perfectly (atomically) monodisperse, ligand-stabilised Metal nanoparticles with nanometric dimensions. Thus, when the nuclearity of molecular clusters is increased and the dimensions of Metal nanoparticles are reduced, these two worlds begin to overlap. Herein, the synthesis of larger MCCs is briefly outlined, together with the description of their structural features and physical properties. The use of molecular MCCs as nanometric or subnanometric building blocks for self-assembly of functional nanomaterials is also reported. Finally, the employment of MCCs as precursors for Metal nanoparticles after decomposition of the molecular precursor is described. The purpose of this microreview is to discuss some representative examples of all these topics, showing that one of the most promising and fascinating aspects of molecular MCCs is their borderline nature between molecular chemistry and nanochemistry.
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the possible role of Metal Carbonyl clusters in nanoscience and nanotechnologies
Coordination Chemistry Reviews, 2006Co-Authors: Cristina Femoni, Carmela M Iapalucci, Francesco Kaswalder, Giuliano Longoni, Stefano ZacchiniAbstract:Although a few nanosized Metal Carbonyl clusters were already obtained in the seventies, these structurally and compositionally well-defined molecules attracted the interest of nanoscientists only as possible precursors of finely dispersed Metal particles for heterogeneous catalysis. This review article has the aim to give a brief account of most recent results in the field of high-nuclearity Metal Carbonyl clusters and their emerging properties. In doing that, a look to related behaviour of ligand-stabilised and ligand-free clusters, including almost mono-dispersed ligand-stabilised Metal nanoparticles, is given. At the end, we will deliberately venture in some speculations on the possible contribution of Metal Carbonyl clusters to some aspects of nanoscience and nanotechnologies.