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Jean'ne M. Shreeve - One of the best experts on this subject based on the ideXlab platform.
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Energetic Salts Based on 3,5-Bis(dinitromethyl)-1,2,4-triazole Monoanion and Dianion: Controllable Preparation, Characterization, and High Performance
Journal of the American Chemical Society, 2016Co-Authors: Jiaheng Zhang, Srinivas Dharavath, Damon A. Parrish, Lauren A. Mitchell, Jean'ne M. ShreeveAbstract:Molecular modification of known explosives is considered to be an efficient route to design new energetic materials. A new family of energetic salts based on the 3,5-bis(dinitromethyl)-1,2,4-triazole Monoanion and dianion were controllably synthesized by using 1-diamino-2,2-dinitroethene as a precursor. X-ray structure determination of monohydrazinium 3,5-bis(dinitromethyl)-1,2,4-triazolate (5) and monoammonium (6) and diammonium 3,5-bis(dinitromethyl)-1,2,4-triazolate hydrate (8·H2O) further confirmed the structures of these anions. In addition, as supported by X-ray data, in the Monoanion system, the roving proton on the ring nitrogen rather than on the gem-dinitro carbon results in extensive hydrogen-bonding interactions and higher packing coefficients. Interestingly, 5 and 6 possess the highest calculated crystal densities, 1.965 and 1.957 g cm–3 at 150 K, for hydrazinium and ammonium energetic salts, respectively. Energetic evaluation indicates that 5 (detonation velocity vD = 9086 m s–1; detonation ...
Jiaheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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Energetic Salts Based on 3,5-Bis(dinitromethyl)-1,2,4-triazole Monoanion and Dianion: Controllable Preparation, Characterization, and High Performance
Journal of the American Chemical Society, 2016Co-Authors: Jiaheng Zhang, Srinivas Dharavath, Damon A. Parrish, Lauren A. Mitchell, Jean'ne M. ShreeveAbstract:Molecular modification of known explosives is considered to be an efficient route to design new energetic materials. A new family of energetic salts based on the 3,5-bis(dinitromethyl)-1,2,4-triazole Monoanion and dianion were controllably synthesized by using 1-diamino-2,2-dinitroethene as a precursor. X-ray structure determination of monohydrazinium 3,5-bis(dinitromethyl)-1,2,4-triazolate (5) and monoammonium (6) and diammonium 3,5-bis(dinitromethyl)-1,2,4-triazolate hydrate (8·H2O) further confirmed the structures of these anions. In addition, as supported by X-ray data, in the Monoanion system, the roving proton on the ring nitrogen rather than on the gem-dinitro carbon results in extensive hydrogen-bonding interactions and higher packing coefficients. Interestingly, 5 and 6 possess the highest calculated crystal densities, 1.965 and 1.957 g cm–3 at 150 K, for hydrazinium and ammonium energetic salts, respectively. Energetic evaluation indicates that 5 (detonation velocity vD = 9086 m s–1; detonation ...
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Energetic Salts Based on 3,5-Bis(dinitromethyl)-1,2,4-triazole Monoanion and Dianion: Controllable Preparation, Characterization, and High Performance
2016Co-Authors: Jiaheng Zhang, Srinivas Dharavath, Lauren A. Mitchell, Damon A. Parrish, Jean’ne M. ShreeveAbstract:Molecular modification of known explosives is considered to be an efficient route to design new energetic materials. A new family of energetic salts based on the 3,5-bis(dinitromethyl)-1,2,4-triazole Monoanion and dianion were controllably synthesized by using 1-diamino-2,2-dinitroethene as a precursor. X-ray structure determination of monohydrazinium 3,5-bis(dinitromethyl)-1,2,4-triazolate (5) and monoammonium (6) and diammonium 3,5-bis(dinitromethyl)-1,2,4-triazolate hydrate (8·H2O) further confirmed the structures of these anions. In addition, as supported by X-ray data, in the Monoanion system, the roving proton on the ring nitrogen rather than on the gem-dinitro carbon results in extensive hydrogen-bonding interactions and higher packing coefficients. Interestingly, 5 and 6 possess the highest calculated crystal densities, 1.965 and 1.957 g cm–3 at 150 K, for hydrazinium and ammonium energetic salts, respectively. Energetic evaluation indicates that 5 (detonation velocity vD = 9086 m s–1; detonation pressure P = 38.7 GPa) and 6 (vD, 9271 m s–1; P = 41.0 GPa) exhibit great detonation properties, superior to those of current highly explosive benchmarks, such as 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)
Karl Wieghardt - One of the best experts on this subject based on the ideXlab platform.
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Electronic Structures and Spectroscopy of the Electron Transfer Series [Fe(NO)L2]z (z = 1+, 0, 1–, 2–,3–; L = Dithiolene)
2016Co-Authors: Panida Surawatanawong, Frank Neese, Stephen Sproules, Karl WieghardtAbstract:The electronic structures and spectroscopic parameters for the electron transfer series of [Fe(NO)(L)2]z (z = 1+, 0, 1–, 2–, 3–; L = S2C2R2; R = p-tolyl (1) and CN (2)) were calculated and compared to experiment. Some compounds in the series were isolated and characterized by spectroscopy. The calculations support the notion that all the monocation (St = 0), neutral (St = 1/2), and Monoanion (St = 0) complexes contain NO+ (SNO = 0), in which the redox active fragment is either the bis-dithiolene (2 L) or the central iron. The calculated electronic structures give insight into how p-tolyl and CN substituents and the redox states of the 2 L ligand impact the spin density on the iron in the monocation and neutral species. The electronic structure of [1]0 has some [FeI(NO+)(L22–)]0 character in resonance with [FeII(NO+)(L22–)]0 whereas [2]0 has a smaller amount of a [FeI(NO+)(L22–)]0 description in its ground state wavefunction. Similarly, the electronic structure of [1]1+ also has some [FeI(NO+)(L21–)]1+ character in resonance with [FeII(NO+)(L22–)]1+ whereas [2]1+ is best described as [FeII(NO+)(L•)2]1+. For the Monoanion, the bis-dithiolene fragment is fully reduced and both [1]− and [2]− are best formulated as [FeII(NO+)(L24–)]−. The reduction of the Monoanion to give dianions [1]2– and [2]2– results in {FeNO}7 species. The calculated 57Fe isomer shift and hyperfine couplings are in line with the experiment and support a description of the form [FeIII(NO–)(L24–)]2–, in which Fe(III) SFe = 3/2 is antiferromagnetically coupled to NO– (SNO = 1). Finally, the calculated redox potential and ν(NO) frequency for the {FeNO}8 trianionic species [2]3– is in agreement with experiment and consistent with a triplet ground state [FeII(NO–)(L24–)]3–, in which Fe(II) (SFe = 2) is involved in antiferromagnetic coupling with NO– (SNO = 1)
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bis α diimine iron complexes electronic structure determination by spectroscopy and broken symmetry density functional theoretical calculations
Inorganic Chemistry, 2008Co-Authors: Nicoleta M Muresan, Eckhard Bill, Meenakshi Ghosh, Jonas C Peters, Megumi Abe, Lawrence M Henling, Thomas Weyhermoller, Karl WieghardtAbstract:The electronic structure of a family comprising tetrahedral (α-diimine)iron dichloride, and tetrahedral bis(α-diimine)iron compounds has been investigated by Mossbauer spectroscopy, magnetic susceptibility measurements, and X-ray crystallography. In addition, broken-symmetry density functional theoretical (B3LYP) calculations have been performed. A detailed understanding of the electronic structure of these complexes has been obtained. A paramagnetic (S_t = 2), tetrahedral complex [Fe^(II)(^4L)_2], where (^4L)^(1−) represents the diamagnetic Monoanion N-tert-butylquinolinylamide, has been synthesized and characterized to serve as a benchmark for a Werner-type complex containing a tetrahedral Fe^(II)N_4 geometry and a single high-spin ferrous ion. In contrast to the most commonly used description of the electronic structure of bis(α-diimine)iron(0) complexes as low-valent iron(0) species with two neutral α-diimine ligands, it is established here that they are, in fact, complexes containing two (α-diiminato)^(1−•) π radical Monoanions and a high-spin ferrous ion (in tetrahedral N_4 geometry) (S_(Fe) = 2). Intramolecular antiferromagnetic coupling between the π radical ligands (S_(rad) = 1/2) and the ferrous ion (S_(Fe) = 2) yields the observed S_t = 1 ground state. The study confirms that α-diimines are redox noninnocent ligands with an energetically low-lying antibonding π^* lowest unoccupied molecular orbital which can accept one or two electrons from a transition metal ion. The (α-diimine)FeCl_2 complexes (St = 2) are shown to contain a neutral α-diimine ligand, a high spin ferrous ion, and two chloride ligands.
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electronic structure of square planar bis benzene 1 2 dithiolato metal complexes m l 2 z z 2 1 0 m ni pd pt cu au an experimental density functional and correlated ab initio study
Inorganic Chemistry, 2005Co-Authors: Kallol Ray, Thomas Weyhermuller, Frank Neese, Karl WieghardtAbstract:The three diamagnetic square planar complexes of nickel(II), palladium(II), and platinum(II) containing two S,S-coordinated 3,5-di-tert-butylbenzene-1,2-dithiolate ligands, (LBu)2-, namely [MII(LBu)2]2-, have been synthesized. The corresponding paramagnetic Monoanions [MII(LBu)(LBu•)]- (S = 1/2) and the neutral diamagnetic species [MII(LBu•)2] (M = Ni, Pd, Pt) have also been generated in solution or in the solid state as [N(n-Bu)4][MII(LBu)(LBu•)] salts. The corresponding complex [CuIII(LBu)2]- has also been investigated. The complexes have been studied by UV−vis, IR, and EPR spectroscopy and by X-ray crystallography; their electro- and magnetochemistry is reported. The electron-transfer series [M(LBu)2]2-,-,0 is shown to be ligand based involving formally one (LBu•)- π radical in the Monoanion or two in the neutral species [MII(LBu•)2] (M = Ni, Pd, Pt). Geometry optimizations using all-electron density functional theory with scalar relativistic corrections at the second-order Douglas−Kroll−Hess (DKH2) an...
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Square Planar vs Tetrahedral Coordination in Diamagnetic Complexes of Nickel(II) Containing Two Bidentate π-Radical Monoanions
Inorganic chemistry, 2005Co-Authors: Sebastien Blanchard, Thomas Weyhermuller, Frank Neese, Eberhard Bothe, Eckhard Bill, Karl WieghardtAbstract:The reaction of three different 1-phenyl and 1,4-diphenyl substituted S-methylisothiosemicarbazides, H(2)[L(1-6)], with Ni(OAc)(2).4H(2)O in ethanol in the presence of air yields six four-coordinate species [Ni(L(1-6)(*))(2)] (1-6) where (L(1-6)(*))(1-) represent the Monoanionic pi-radical forms. The crystal structures of the nickel complexes with 1-phenyl derivatives as in 1 reveal a square planar structure trans-[Ni(L(1)(-3)(*))(2)], whereas the corresponding 1,4-diphenyl derivatives are distorted tetrahedral as is demonstrated by X-ray crystallography of [Ni(L(5)(*))(2)] (5) and [Ni(L(6)(*))(2)] (6). Both series of mononuclear complexes possess a diamagnetic ground state. The electronic structures of both series have been elucidated experimentally (electronic spectra magnetization data). The square planar complexes 1-3 consist of a diamagnetic central Ni(II) ion and two strongly antiferromagnetically coupled ligand pi-radicals as has been deduced from correlated ab initio calculations; they are singlet diradicals. The tetrahedral complexes 4-6 consist of a paramagnetic high-spin Ni(II) ion (S(Ni) = 1), which is strongly antiferromagnetically coupled to two ligand pi-radicals. This is clearly revealed by DFT and correlated ab initio calculations. Electrochemically, complexes 1-6 can be reduced to form stable, paramagnetic Monoanions [1-6](-) (S = (1)/(2)). The anions [1-3](-) are square planar Ni(II) (d,(8) S(Ni) = 0) species where the excess electron is delocalized over both ligands (class III, ligand mixed valency). In contrast, one-electron reduction of 4, 5, and 6 yields paramagnetic tetrahedral Monoanions (S = (1)/(2)). X-band EPR spectroscopy shows that there are two different isomers A and B of each Monoanion present in solution. In these anions, the excess electron is localized on one ligand [Ni(II)(L(4-6)(*))(L(4-6))](-) where (L(4-6))(2-) is the closed shell dianion of the ligands H(2)[L(4-6)] as was deduced from their electronic spectra and broken symmetry DFT calculations. Oxidation of 1 and 5 with excess iodine yields octahedral complexes [Ni(II)(L(1,ox))(2)I(2)] (7), [Ni(II)(L(1,ox))(3)](I(3))(2) (8), and trans-[Ni(II)(L(5,ox))(2)(I(3))(2)] (9), which have been characterized by X-ray crystallography; (L(1-)(6,ox)) represent the neutral, two-electron oxidized forms of the corresponding dianions (L(1-6))(2-). The room-temperature structures of complexes 1, 5, and 7 have been described previously in refs 1-5.
Rebecca A Jockusch - One of the best experts on this subject based on the ideXlab platform.
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fluorescence and electronic action spectroscopy of mass selected gas phase fluorescein 2 7 dichlorofluorescein and 2 7 difluorofluorescein ions
Journal of Physical Chemistry A, 2013Co-Authors: Rebecca A JockuschAbstract:2′,7′-Dichloro- and 2′,7′-difluorofluoresceins are superior alternatives to underivatized fluorescein. Although several studies characterizing their condensed-phase photophysical properties have been reported, little is known about their intrinsic characteristics. Here, the gas-phase properties of three charge states of each fluorescein are characterized using a quadrupole ion trap mass spectrometer which has been modified for spectroscopy. Electronic action spectra, constructed by monitoring the extent of photodissociation as a function of excitation wavelength, indicate that the gaseous dianions and cations resemble their solution-phase counterparts. In contrast, a large shift in the electronic action spectra of the Monoanions indicates the presence of a different tautomer in the gas phase than that present in solution. The gaseous Monoanion is deprotonated on the xanthene ring, rather than being deprotonated on the pendant group as found in soluion. The dianions and cations do not emit detectable fluor...
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infrared multiple photon dissociation action spectroscopy and computational studies of mass selected gas phase fluorescein and 2 7 dichlorofluorescein ions
Journal of Physical Chemistry A, 2011Co-Authors: Huihui Yao, Jeffrey D Steill, Jos Oomens, Rebecca A JockuschAbstract:Fluorescein (FL) and its derivative 2',7'-dichlorofluoroescein (DCF) are well-known fluorescent dyes used in many biological and biochemical applications. Although extensive studies have been carried out to investigate their chemical and photophysical properties in different solvent media, little is known about their intrinsic behaviors in the gas phase. Here, infrared multiple photon dissociation (IRMPD) action spectra are reported for the three charged prototropic forms of FL and DCF and compared with computed IR spectra from electronic structure calculations. In each case, the measured spectra show good agreement with the calculated spectra of the lowest energy computed conformer. Moreover, the major bands of the Monoanion IRMPD spectra show striking similarities to those of the dianions and are quite different from those of the cations. These experimental results clearly indicate that the gaseous Monoanions are predominantly deprotonated on the xanthene chromophore, rather than the benzoate deprotonation site favored in solution. Investigations such as this, which provide a better understanding of intrinsic properties of ionic dyes, forms a baseline from which to elucidate solvent effects and will aid the rational design of dyes possessing desirable fluorescence properties.
Jos Oomens - One of the best experts on this subject based on the ideXlab platform.
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Infrared Multiple Photon Dissociation Spectroscopy of a Gas-Phase Oxo-Molybdenum Complex with 1,2-Dithiolene Ligands
2016Co-Authors: Michael J. Van Stipdonk, Partha Basu, Sara A. Dille, John K. Gibson, Giel Berden, Jos OomensAbstract:*S Supporting Information ABSTRACT: Electrospray ionization (ESI) in the negative ion mode was used to create anionic, gas-phase oxo-molybdenum complexes with dithiolene ligands. By varying ESI and ion transfer conditions, both doubly and singly charged forms of the complex, with identical formulas, could be observed. Collision-induced dissociation (CID) of the dianion generated exclusively the Monoanion, while fragmentation of the Monoanion involved decomposition of the dithiolene ligands. The intrinsic structure of the Monoanion and the dianion were determined by using wavelength-selective infrared multiple-photon dissociation (IRMPD) spectroscopy and density functional theory calculations. The IRMPD spectrum for the dianion exhibits absorptions that can be assigned to (ligand) CC, C−S, CCN, and MoO stretches. Comparison of the IRMPD spectrum to spectra predicted for various possible conformations allows assignment of a pseudo square pyramidal structure with C2v symmetry, equatorial coordination of MoO2+ by the S atoms of the dithiolene ligands, and a singlet spin state. A single absorption was observed for the oxidized complex. When the same scaling factor employed for the dianion is used for the oxidized version, theoretical spectra suggest that the absorption is the MoO stretch for a distorted square pyramidal structure and doublet spin state. A predicted change in conformation upon oxidation of the dianion is consistent with a proposed bonding scheme for the bent-metallocene dithiolene compounds [Lauher, J. W.; Hoffmann, R. J. Am. Chem. Soc. 1976, 98, 1729−1742], where a large folding of the dithiolene moiety along the S···S vector is dependent on the occupancy of the in-plane metal d-orbital
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Infrared Multiple Photon Dissociation Spectroscopy of a Gas-Phase Oxo-Molybdenum Complex with 1,2-Dithiolene Ligands
2015Co-Authors: Michael J. Van Stipdonk, Partha Basu, Sara A. Dille, John K. Gibson, Giel Berden, Jos OomensAbstract:Electrospray ionization (ESI) in the negative ion mode was used to create anionic, gas-phase oxo-molybdenum complexes with dithiolene ligands. By varying ESI and ion transfer conditions, both doubly and singly charged forms of the complex, with identical formulas, could be observed. Collision-induced dissociation (CID) of the dianion generated exclusively the Monoanion, while fragmentation of the Monoanion involved decomposition of the dithiolene ligands. The intrinsic structure of the Monoanion and the dianion were determined by using wavelength-selective infrared multiple-photon dissociation (IRMPD) spectroscopy and density functional theory calculations. The IRMPD spectrum for the dianion exhibits absorptions that can be assigned to (ligand) CC, C–S, CCN, and MoO stretches. Comparison of the IRMPD spectrum to spectra predicted for various possible conformations allows assignment of a pseudo square pyramidal structure with C2v symmetry, equatorial coordination of MoO2+ by the S atoms of the dithiolene ligands, and a singlet spin state. A single absorption was observed for the oxidized complex. When the same scaling factor employed for the dianion is used for the oxidized version, theoretical spectra suggest that the absorption is the MoO stretch for a distorted square pyramidal structure and doublet spin state. A predicted change in conformation upon oxidation of the dianion is consistent with a proposed bonding scheme for the bent-metallocene dithiolene compounds [Lauher, J. W.; Hoffmann, R. J. Am. Chem. Soc. 1976, 98, 1729−1742], where a large folding of the dithiolene moiety along the S···S vector is dependent on the occupancy of the in-plane metal d-orbital
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infrared multiple photon dissociation action spectroscopy and computational studies of mass selected gas phase fluorescein and 2 7 dichlorofluorescein ions
Journal of Physical Chemistry A, 2011Co-Authors: Huihui Yao, Jeffrey D Steill, Jos Oomens, Rebecca A JockuschAbstract:Fluorescein (FL) and its derivative 2',7'-dichlorofluoroescein (DCF) are well-known fluorescent dyes used in many biological and biochemical applications. Although extensive studies have been carried out to investigate their chemical and photophysical properties in different solvent media, little is known about their intrinsic behaviors in the gas phase. Here, infrared multiple photon dissociation (IRMPD) action spectra are reported for the three charged prototropic forms of FL and DCF and compared with computed IR spectra from electronic structure calculations. In each case, the measured spectra show good agreement with the calculated spectra of the lowest energy computed conformer. Moreover, the major bands of the Monoanion IRMPD spectra show striking similarities to those of the dianions and are quite different from those of the cations. These experimental results clearly indicate that the gaseous Monoanions are predominantly deprotonated on the xanthene chromophore, rather than the benzoate deprotonation site favored in solution. Investigations such as this, which provide a better understanding of intrinsic properties of ionic dyes, forms a baseline from which to elucidate solvent effects and will aid the rational design of dyes possessing desirable fluorescence properties.