A Method for Calibrating the Relative Gamma-Ray Light Yield of Plastic Scintillators

Currently, we are investigating the inclusion of organotin compounds in new polystyrene scintillator materials to improve full gamma-ray energy sensitivity. Accurate calibration of the relative light yield from the newly developed scintillators is crucial to assess merits of compounds and chemical processes used in the scintillators’ development. In this study, we present a spectral gain matching of measured and simulated spectra, using a spectrum rebinning technique, to determine the Compton edge in a measured Compton continuum for accurate relative light yield calibration. The Compton edges determined using this technique were found to be within 1.2% of their theoretical estimates.

  • Mengesha, W.; Feng, P. L.; Cordaro, J. G.; Anstey, M. R.; Myllenbeck, N. R.; Throckmorton, D. J. Review of Scientific Instruments 2017, 88 (3), 035108.

Control of Clustering Behavior in Anionic Cerium(III) Corrole Complexes: from Oligomers to Monomers

The first synthesis of anion-capped cerium corrole complexes is reported. Unusual clustering of the lanthanide corrole units has been found, and the degree of aggregation can be controlled by the choice of the capping ligand. A polymeric structure is formed using sodium cyclopentadienide (NaCp) and a dimeric structure is formed when potassium tris(pyrazolyl)borate (KTp) is used. Encapsulation of the counter-cation leads to the isolation of the monomeric structures.

  • Armstrong, K. C.; Hohloch, S.; Lohrey, T. D.; Zarkesh, R. A.; Arnold, J.;* Anstey, M. R.* Dalton Trans. 2016, 45 (46), 18653–18660.

Distance Dependent Quenching and Gamma-Ray Spectroscopy in Tin-Loaded Polystyrene Scintillators

In this work, we report the synthesis and inclusion of rationally designed organotin compounds in polystyrene matrices as a route towards plastic scintillators capable of gamma-ray spectroscopy. Tin loading ratios of up to 15% w/w have been incorporated, resulting in photopeak energy resolution values as low as 10.9% for 662 keV gamma-rays. We also report fast scintillation decay behavior that is comparable to the quenched scintillators 0.5% trans-stilbene doped bibenzyl and the commercial plastic scintillator BC-422Q-1%.

  • Feng, P. L.; Mengesha, W.; Anstey, M. R.; Cordaro, J. G. IEEE Trans. Nucl. Sci. 2016, 63 (1), 407–415.

Voltage Clustering in Redox-Active Ligand Complexes: Mitigating Electronic Communication Through Choice of Metal Ion

The redox-active bis(imino)acenapthene (BIAN) ligand was used to synthesize homoleptic aluminum, chromium, and gallium complexes of the general formula (BIAN)3M. The resulting compounds were characterized and modeled to compare the orbital contributions of main group elements and transition metals in ligand-based redox events. Complexes of this type have the potential to improve the energy density and electrolyte stability of grid-scale energy storage technologies, such as redox flow batteries, through thermodynamically-clustered redox events.

  • Zarkesh, R. A.; Ichimura, A. S.; Monson, T. C.; Tomson, N. C.; Anstey, M. R.* Dalton Trans. 2016, 45 (24), 9962–9969.
  • [Featured in a special issue entitled New Talent: Americas]

Redox Flow Batteries: An Engineering Perspective

Redox flow batteries are well suited to provide modular and scalable energy storage systems for a wide range of energy storage applications. In this paper, we review the development of redox-flow-battery technology including recent advances in new redox active materials, cell designs, and systems, all from the perspective of engineers interested in applying this technology. We discuss cost, performance, and reliability metrics that are critical for deployment of large flow-battery systems. The technology, while relatively young, has the potential for significant improvement through reduced materials costs, improved energy efficiency, and significant reduction in the overall system costs.

  • Chalamala, B. R.; Soundappan, T.; Fisher, G. R.; Anstey, M. R.; Viswanathan, V. V.; Perry, M. L. Proc. IEEE 2014, 102 (6), 976–999.

Application of Redox Non-Innocent Ligands to Non-Aqueous Flow Battery Electrolytes

High energy-density, redox flow batteries (RFB) can provide cost-effective, grid-scale energy storage, facilitating the use of intermittent sources such as solar and wind power. A new electrolyte based on vanadium and redox-active ligands that stores equivalents of charge separately from the metal center is presented. Electrolytes composed of non-innocent ligands greatly enhance both the energy density and stability of non-aqueous RFBs.

  • Cappillino, P. J.; Pratt, H. D., III; Hudak, N. S.; Tomson, N. C.; Anderson, T. M.; Anstey, M. R.* Adv. Energy Mater. 2014, No. 4, 1300566.

Lanthanide Corroles: A New Class of Macrocyclic Lanthanide Complexes

The first examples of lanthanide corroles are prepared by two synthetic routes. (Mes2(p-OMePh)corrole)La·4.5DME (1·4.5DME) and (Mes2(p-OMePh)corrole)Tb·4DME (2·4DME) are prepared from the free base corrole and Ln((NSiMe3)2)3, while (Mes2(p-OMePh)corrole)GdTACNMe3(3·TACNMe3) is prepared by metathesis of the recently reported Li3corrole and GdCl3.

  • Buckley, H. L.; Anstey, M. R.; Gryko, D. T.; Arnold, J. Chem. Commun. 2013, 49 (30), 3104–3106.

Surface Immobilization of an Organo-Iridium Complex Through a Carbon-Metal Bond

A new approach to the immobilization of organometallic complexes to monolayer surfaces is demonstrated using aldehyde-terminated self-assembled monolayers and a Cp*Ir complex. The iridium complex is anchored to the surface by direct attachment of the metal to the carbon chain of the monolayer film.

  • Razgon, A.; Anstey, M. R.; Yakelis, N. A.; Bergman, R. G.; Sukenik, C. N. Inorganica Chimica Acta 2011, 375 (1), 305–307.

Ordered Metal Nanostructure Self-Assembly Using Metal-Organic Frameworks as Templates

We demonstrate that nanoporous metal–organic frameworks (MOFs) loaded with silver can serve as templates for ordered nanostructures comprising either silver nanoparticles or nanowires. Exposure to an electron beam breaks down the template, leading to rapid silver coalescence. The geometric and chemical structure of the MOF, as well as the extent of metal loading, determine whether nanoparticles or nanowires are formed and define their size and orientation. Nanowires with diameters as small as 4 nm and aspect ratios >125 can be formed, overcoming the limitations of existing templating methods. This method is relatively simple, compatible with many materials, and proceeds by a distinct template-directed growth mechanism. Since MOFs offer an unprecedented level of synthetic flexibility, combined with highly uniform porosity as a result of their crystalline structure, this approach opens a promising new route for synthesis of self-assembled, ordered nanostructures.

  • Jacobs, B. W.; Houk, R. J. T.; Anstey, M. R.; House, S. D.; Robertson, I. M.; Talin, A. A.; Allendorf, M. D. Chem. Sci. 2011, 2 (3), 411-416.

Improved Synthesis of Bis(borano)hypophosphite Salts

A synthesis of the bis(borano)hypophosphite anion with various counterions has been developed to make use of more benign and commercially available reagents. This method avoids the use of potentially dangerous reagents used by previous methods and gives the final products in good yield. Details of the crystal structure determination of the sodium salt in space group Ama2 are given using a novel computational technique combined with Rietveld refinement.

  • Anstey, M. R.; Corbett, M. T.; Majzoub, E. H.; Cordaro, J. G. Inorg. Chem. 2010, 49 (18), 8197–8199.

Photoinduced N2 Loss as a Route to Long-Lived Organometallic Alkane Complexes: A Time-Resolved IR and NMR Study

Photolysis of CpRe(CO)2(N2) and CpRe(CO)2(N2) in alkane solutions with a UV lamp via a quartz fibre inserted into the NMR probe allows generation of a CpRe(CO)2(alkane) agostic complex. The major isomer of CpRe(CO)2(2,2-dimethylbutane-h2-C1,H1), exhibits a 1H NMR resonance for the co-ordinated hydrogen at δ = -2.19 with ¹J = 118 Hz. The photochemistry of CpRe(CO)2(N2) (Cp = h5-1,2-C5H3(tBu)2) in alkane solution is also reported. The reaction with cyclopentane has also been studied by NMR spectroscopy at 190 K with in situ laser irradiation at 355 nm. CpRe(CO)2(C5H10) is shown to exhibit the characteristic features of an alkane complex in the NMR spectrum, viz. a large isotopic shift of the 1H resonance at  δ = -2.44 upon partial deuteration of the alkane (Δδ = 1.77 ppm), a large ¹J (114 Hz) and a large negative 13C chemical shift (δ = -33.8).

  • Calladine, J. A.; Torres, O.; Anstey, M.; Ball, G. E.; Bergman, R. G.; Curley, J.; Duckett, S. B.; George, M. W.; Gilson, A. I.; Lawes, D. J.; Perutz, R. N.; Sun, X.-Z.; Vollhardt, K. P. C. Chem. Sci. 2010, 1 (5), 622–630.

Unexpected C-C Bond Cleavage and C-C Bond Formation Observed in the reaction of a Cationic Iridium Complex with Heteroatom-Substituted Cyclopropanes

Iridium complex Cp*(PMe3)Ir(CH3)OTf (1) and alkylaminocyclopropanes react via a well-understood initial C−H bond activation with a subsequent C−C bond-breaking step to yield a variety of π-allyl complexes [Cp*(PMe3)Ir(η3-C3H4NR1R2)][OTf] (R1 = R2 = Bn; R1 = Bn, R2 = Ph) and methane. However, diphenylamino, alkoxy, or siloxycyclopropanes, when treated with complex 1, yield a new π-allyl complex [Cp*(PMe3)Ir(η3-C3H4CH3)][OTf] (8) and the corresponding amine or alcohol. The methyl group initially bound to iridium is no longer extruded as methane, but instead is incorporated into the allyl moiety to give a new carbon−carbon bond. A detailed mechanistic study provides evidence in support of an initial C−C bond activation mechanism as opposed to the initial C−H bond activation observed with other known substrates.

  • Anstey, M. R.; Yung, C. M.; Du, J.; Bergman, R. G. J. Am. Chem. Soc. 2007, 129 (4), 776–777.

Diastereo-and Enantioselective Dearomatization of Rhenium-bound Naphthalenes

Dihapto-coordinated naphthalene complexes of the form TpRe(CO)(L)(η²-naphthalene) (L = PMe3, pyridine, or 1-methylimidazole) undergo electrophilic addition with dimethoxymethane and with various Michael acceptors to generate 1H-naphthalenium species. These naphthalenium complexes undergo intra- or intermolecular nucleophilic addition reactions with stabilized enolates, silyl ketene acetals, or enols to form the corresponding dihydronaphthalene complexes. Oxidative decomplexation generates the free dihydronaphthalene. When a resolved form of the rhenium dearomatization agent is used, these reactions can be performed enantioselectively. DFT calculations provide a useful guide in explaining the observed stereochemistry. Depending on reaction conditions, a Michael-Michael ring-closure sequence (MIMIRC) or a net [2 + 4] cycloaddition with the bound naphthalene is also observed, and the corresponding tricyclic molecules can be removed from the metal in high yield.

  • Ding, F.; Valahovic, M. T.; Keane, J. M.; Anstey, M. R.; Sabat, M.; Trindle, C. O.; Harman, W. D. J. Org. Chem. 2004, 69 (7), 2257–2267.