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Scott R. Wilson

Bio: Scott R. Wilson is an academic researcher from University of Illinois at Urbana–Champaign. The author has contributed to research in topics: Crystal structure & Reactivity (chemistry). The author has an hindex of 58, co-authored 341 publications receiving 13397 citations. Previous affiliations of Scott R. Wilson include Karlsruhe Institute of Technology & Urbana University.


Papers
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Journal ArticleDOI
TL;DR: The FTIR spectrum properties of compound IIIA,B are consistent with the presence of SO3groups attached to the aromatic rings of polysemiquinone polyaniline.
Abstract: need to be sulfonated in order to produce the stable polysemiquinone form of the polymer. Indeed, additional sulfonation and consequent protonation of amine nitrogen atoms would convert some of the -(NH)to -(NHzf)groups and hence destabilize the polymer by reducing the extent of its T conjugation. The absorption maxima at 1080, 700, and 620 cm-' in the FTIR spectrum of compound IIIA,B are consistent with the presence9 of SO3groups attached to the aromatic rings. The absorption maxima at 820 and 870 cm-I indicative of 1,2,4-trisubstitution of the rings are out-of-plane bending of aromatic hydrogens. These absorptions are not present in the 1,2-disubstituted emeraldine base ( I I ) , from which compound IIIA,B was synthesized. The solubilities of compounds IIIA,B and IV differ markedly from those of the corresponding protonated and nonprotonated forms, respectively, of parent polyaniline. Compound IIIA,B dissolves appreciably in aqueous 0.1 M N H 4 0 H or NaOH to give the corresponding salts whereas emeraldine hydrochloride when treated in this manner is converted to the insoluble emeraldine base form (11). The anionic (SO,-) groups are presumably largely responsible for its solubility in water. Compound IIIA,B partly dissolves in DMSO, giving the dark green color of the protonated polyaniline, but is apparently deprotonated when it dissolves in N-methyl-2-pyrrolidinone (NMP), in which it has a blue-violet color, characteristic of compound IV. The high concentration of protons in the vicinity of the polymer backbone due to the presence of the attached SO3groups is not only responsible for the retention of doping of the polymer at the higher pH values, where the parent emeraldine base polymer (TI) is essentially a (nondoped) insulator, but is also consistent with the observed faster electrochemical redox reactions of compound IIIA,B in aqueous media.

1,483 citations

Journal ArticleDOI
22 Mar 2007-Nature
TL;DR: It is shown that mechanically sensitive chemical groups make it possible to harness the mechanical forces generated when exposing polymer solutions to ultrasound, and that this allows us to accelerate rearrangement reactions and bias reaction pathways to yield products not obtainable from purely thermal or light-induced reactions.
Abstract: For most chemical reactions to proceed the reactants need to surmount an energy barrier. The energy required is usually provided as heat, light, pressure or electrical potential. Now mechanical force can be added to that list: to the surprise of many a chemist, a reaction can literally be given a shove. In specially designed polymers subjected to ultrasound, rearrangement reactions are accelerated and reaction pathways can be biased to yield products not obtainable from heat- or light-induced reactions. The polymers contain a mechanophore positioned at a site where forces from extensional flow are greatest. Besides offering new ways of controlling chemical reactions, this work may also lead to mechanically adaptable materials, polymers that might generate a signal to warn of impending damage, undergo structure modification to slow the rate of damage, or even self-repair. Carefully designed 'mechanophores' can tame the 'brute force' approach needed for breaking chemical bonds in reactions. If incorporated into polymers and activated by mechanical forces, the mechanophores undergo rearrangement reactions to selectively form new molecules. The effect might result in mechanically responsive polymers that warn of impending structural failures, can slow damage or even self-repair. During the course of chemical reactions, reactant molecules need to surmount an energy barrier to allow their transformation into products. The energy needed for this process is usually provided by heat, light, pressure or electrical potential, which act either by changing the distribution of the reactants on their ground-state potential energy surface or by moving them onto an excited-state potential energy surface and thereby facilitate movement over the energy barrier. A fundamentally different way of initiating or accelerating a reaction is the use of force to deform reacting molecules along a specific direction of the reaction coordinate. Mechanical force has indeed been shown to activate covalent bonds in polymers, but the usual result is chain scission1. Here we show that mechanically sensitive chemical groups make it possible to harness the mechanical forces generated when exposing polymer solutions to ultrasound2, and that this allows us to accelerate rearrangement reactions and bias reaction pathways to yield products not obtainable from purely thermal or light-induced reactions. We find that when placed within long polymer strands, the trans and cis isomers of a 1,2-disubstituted benzocyclobutene undergo an ultrasound-induced electrocyclic ring opening in a formally conrotatory and formally disrotatory process, respectively, that yield identical products. This contrasts with reaction initiation by light or heat alone3, in which case the isomers follow mutually exclusive pathways to different products. Mechanical forces associated with ultrasound can thus clearly alter the shape of potential energy surfaces4 so that otherwise forbidden or slow processes proceed under mild conditions, with the directionally specific nature of mechanical forces providing a reaction control that is fundamentally different from that achieved by adjusting chemical or physical parameters. Because rearrangement in our system occurs before chain scission, the effect we describe might allow the development of materials that are activated by mechanical stress fields.

695 citations

Journal ArticleDOI
TL;DR: Using various polyfunctionalized porphyrins, this work has created porous solids that are thermally robust and that retain their internal porosity upon loss of solvates.
Abstract: Metalloporphyrins are exceedingly useful building blocks for the design and synthesis of molecularly based solids. The use of hydrogen bonding or metal ion coordination provides a wide range of framework solids. Using various polyfunctionalized porphyrins, we have created porous solids that are thermally robust and that retain their internal porosity upon loss of solvates. Their pore dimensions are comparable to zeolites, and they show shape and size selectivity in sorption of guest molecules and in epoxidation of alkenes.

455 citations

Journal ArticleDOI
TL;DR: This work has demonstrated repeatable sorption–desorption with high selectivity on the basis of size, shape and functional group of the sorbate by a microporous metalloporphyrin solid in analogy to zeolites.
Abstract: The assembly of molecular building blocks with metal ions genera-ting microporous network solids has been the focus of intense activity1,2,3,4,5,6,7,8,9,10,11,12. Because of their potential applications associated with channels and cavities, such materials have been examined for size- and shape-selective catalysis, separations, sensors, molecular recognition and nanoscale reactors. Within this context, assemblies of robust and chemically versatile porphyrin and metalloporphyrin building blocks remain rare. Supramolecular architectures of porphyrin solids based on weak van der Waals interactions13,14, hydrogen bonding15,16 and metal-ligand coordination networks17,18,19,20,21,22,23 have been reported. Although there are frequent allusions to zeolite-like microporosity from crystallography and loss of initial guest solvent molecules, evidence of functional microporous behaviour is scarce. We have demonstrated repeatable sorption–desorption with high selectivity on the basis of size, shape and functional group of the sorbate by a microporous metalloporphyrin solid in analogy to zeolites.

410 citations

Journal ArticleDOI
TL;DR: A series of models for the active site (H-cluster) of the iron-only hydrogenase enzymes (Fe-only H2-ases) were prepared and diequatorial and axial-equatorial isomers were observed by NMR analysis.
Abstract: A series of models for the active site (H-cluster) of the iron-only hydrogenase enzymes (Fe-only H2-ases) were prepared. Treatment of MeCN solutions of Fe2(SR)2(CO)6 with 2 equiv of Et4NCN gave [Fe2(SR)2(CN)2(CO)4](2-) compounds. IR spectra of the dicyanides feature four nu(CO) bands between 1965 and 1870 cm(-1) and two nu(CN) bands at 2077 and 2033 cm(-1). For alkyl derivatives, both diequatorial and axial-equatorial isomers were observed by NMR analysis. Also prepared were a series of dithiolate derivatives (Et4N)2[Fe2(SR)2(CN)2(CO)4], where (SR)2 = S(CH2)2S, S(CH2)3S. Reaction of Et4NCN with Fe2(S-t-Bu)2(CO)6 gave initially [Fe2(S-t-Bu)2(CN)2(CO)4](2-), which comproportionated to give [Fe2(S-t-Bu)2(CN)(CO)5](-). The mechanism of the CN(-)-for-CO substitution was probed as follows: (i) excess CN(-) with a 1:1 mixture of Fe2(SMe)2(CO)6 and Fe2(SC6H4Me)2(CO)6 gave no mixed thiolates, (ii) treatment of Fe2(S2C3H6)(CO)6 with Me3NO followed by Et4NCN gave (Et4N)[Fe2(S2C3H6)(CN)(CO)5], which is a well-behaved salt, (iii) treatment of Fe2(S2C3H6)(CO)6 with Et4NCN in the presence of excess PMe3 gave (Et4N)[Fe2(S2C3H6)(CN)(CO)4(PMe3)] much more rapidly than the reaction of PMe3 with (Et4N)[Fe2(S2C3H6)(CN)(CO)5], and (iv) a competition experiment showed that Et4NCN reacts with Fe2(S2C3H6)(CO)6 more rapidly than with (Et4N)[Fe2(S2C3H6)(CN)(CO)5]. Salts of [Fe2(SR)2(CN)2(CO)4](2-) (for (SR)2 = (SMe)2 and S2C2H4) and the monocyanides [Fe2(S2C3H6)(CN)(CO)5](-) and [Fe2(S-t-Bu)2(CN)(CO)5](-) were characterized crystallographically; in each case, the Fe-CO distances were approximately 10% shorter than the Fe-CN distances. The oxidation potentials for Fe2(S2C3H6)(CO)4L2 become milder for L = CO, followed by MeNC, PMe3, and CN(-); the range is approximately 1.3 V. In water,oxidation of [Fe2(S2C3H6)(CN)2(CO)4](2-) occurs irreversibly at -0.12 V (Ag/AgCl) and is coupled to a second oxidation.

273 citations


Cited by
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Journal ArticleDOI
30 Aug 2013-Science
TL;DR: Metal-organic frameworks are porous materials that have potential for applications such as gas storage and separation, as well as catalysis, and methods are being developed for making nanocrystals and supercrystals of MOFs for their incorporation into devices.
Abstract: Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

10,934 citations

Journal ArticleDOI
12 Jun 2003-Nature
TL;DR: This work has shown that highly porous frameworks held together by strong metal–oxygen–carbon bonds and with exceptionally large surface area and capacity for gas storage have been prepared and their pore metrics systematically varied and functionalized.
Abstract: The long-standing challenge of designing and constructing new crystalline solid-state materials from molecular building blocks is just beginning to be addressed with success. A conceptual approach that requires the use of secondary building units to direct the assembly of ordered frameworks epitomizes this process: we call this approach reticular synthesis. This chemistry has yielded materials designed to have predetermined structures, compositions and properties. In particular, highly porous frameworks held together by strong metal-oxygen-carbon bonds and with exceptionally large surface area and capacity for gas storage have been prepared and their pore metrics systematically varied and functionalized.

8,013 citations

Journal ArticleDOI
TL;DR: Solar energy is by far the largest exploitable resource, providing more energy in 1 hour to the earth than all of the energy consumed by humans in an entire year, and if solar energy is to be a major primary energy source, it must be stored and dispatched on demand to the end user.
Abstract: Global energy consumption is projected to increase, even in the face of substantial declines in energy intensity, at least 2-fold by midcentury relative to the present because of population and economic growth. This demand could be met, in principle, from fossil energy resources, particularly coal. However, the cumulative nature of CO2 emissions in the atmosphere demands that holding atmospheric CO2 levels to even twice their preanthropogenic values by midcentury will require invention, development, and deployment of schemes for carbon-neutral energy production on a scale commensurate with, or larger than, the entire present-day energy supply from all sources combined. Among renewable energy resources, solar energy is by far the largest exploitable resource, providing more energy in 1 hour to the earth than all of the energy consumed by humans in an entire year. In view of the intermittency of insolation, if solar energy is to be a major primary energy source, it must be stored and dispatched on demand to the end user. An especially attractive approach is to store solar-converted energy in the form of chemical bonds, i.e., in a photosynthetic process at a year-round average efficiency significantly higher than current plants or algae, to reduce land-area requirements. Scientific challenges involved with this process include schemes to capture and convert solar energy and then store the energy in the form of chemical bonds, producing oxygen from water and a reduced fuel such as hydrogen, methane, methanol, or other hydrocarbon species.

7,076 citations

Journal ArticleDOI
TL;DR: A critical review of the emerging field of MOF-based catalysis is presented and examples of catalysis by homogeneous catalysts incorporated as framework struts or cavity modifiers are presented.
Abstract: A critical review of the emerging field of MOF-based catalysis is presented. Discussed are examples of: (a) opportunistic catalysis with metal nodes, (b) designed catalysis with framework nodes, (c) catalysis by homogeneous catalysts incorporated as framework struts, (d) catalysis by MOF-encapsulated molecular species, (e) catalysis by metal-free organic struts or cavity modifiers, and (f) catalysis by MOF-encapsulated clusters (66 references).

7,010 citations