Phys Chem Chem Phys
November 2017
Department of Chemistry, Syracuse University, 1-014 Center for Science and Technology, Syracuse, NY 13244-4100, USA.
Crystalline polymorphism is a phenomenon that occurs in many molecular solids, resulting in a diverse range of possible bulk structures. Temperature and pressure can often be used to thermodynamically control which crystal form is preferred, and the associated transitions between polymorphic phases are often discontinuous and complete. N-Methyl-4-carboxypyridinium chloride is a solid that undergoes an apparent continuous temperature-dependent phase transition from an orthorhombic to a monoclinic polymorph.
View Article and Find Full Text PDFSynlett
October 2017
Department of Chemistry, Syracuse University, 1-014 Center for Science and Technology, Syracuse, NY 13244.
Trichloroacetimidates function as effective electrophiles for the selective C3-alkylation of 2,3-disubstituted indoles to provide 3,3'-disubstituted indolenines. These indolenines are common synthetic intermediates that are often utilized in the synthesis of complex molecules. Effective reaction conditions utilizing Lewis acid catalysts have been determined, and the scope of the reaction with respect to indole and imidate reaction partner has been investigated.
View Article and Find Full Text PDFInorg Chem
October 2017
Department of Chemistry, 1-014 Center for Science and Technology, Syracuse University, Syracuse, New York 13244-4100, United States.
This paper reports advances in redox transmetalation/protolysis (RTP) utilizing the readily available PhBi for the synthesis of a series of barium metal-organic species. On the basis of easily available starting materials, an easy one-pot procedure, and workup, we have obtained BaL compounds (L = bis(trimethylsilyl)amide, phenyl(trimethylsilyl)amide, pentamethylcyclopentadienide, fluorenide, 2,6-di-isopropylphenolate, and 3,5-diphenylpyrazolate) quantitatively by sonication of an excess of barium metal with triphenylbismuth and HL in perdeuterotetrahydrofuran, as established by NMR measurements. Rates of conversion are affected by both pK and bulk of HL.
View Article and Find Full Text PDFJ Phys Chem A
October 2017
Department of Chemistry, Syracuse University , 1-014 Center for Science and Technology, 111 College Place, Syracuse, New York 13244, United States.
We measured photolysis kinetics of the PAH anthracene in aqueous solution, in bulk ice, and at ice surfaces in the presence and absence of chromophoric dissolved organic matter (CDOM). Self-association, which occurs readily at ice surfaces, may be responsible for the faster anthracene photolysis observed there. Photolysis rate constants in liquid water increased under conditions where anthracene self-association was observed.
View Article and Find Full Text PDFEnviron Sci Technol
September 2017
1-014 Center for Science and Technology, Syracuse University 111 College Place Syracuse, New York 13244, United States.
Photochemistry is a largely unconsidered potential source of reactive species such as hydroxyl and peroxy radicals (OH and HO, "HO") indoors. We present measured wavelength-resolved photon fluxes and distance dependences of indoor light sources including halogen, incandescent, and compact fluorescent lights (CFL) commonly used in residential buildings; fluorescent tubes common in industrial and commercial settings; and sunlight entering buildings through windows. We use these measurements to predict indoor HO production rates from the photolysis of nitrous acid (HONO), hydrogen peroxide (HO), ozone (O), formaldehyde (HCHO), and acetaldehyde (CHCHO).
View Article and Find Full Text PDFJ Phys Chem A
August 2017
Department of Chemistry, Syracuse University , 1-014 Center for Science and Technology, Syracuse, New York 13244-4100, United States.
The hygroscopicity of solid sorbitol is important for its utilization as a sweetener in the pharmaceutical and food industries. The molecular foundations of sorbitol hydration characteristics are explored here using two solvated cocrystals, sorbitol-water and sorbitol-pyridine. In this work, solid-state density functional theory and terahertz time-domain spectroscopy were used to evaluate the relative stabilities of these cocrystals as compared to anhydrous sorbitol in terms of conformational and cohesive energies.
View Article and Find Full Text PDFJ Phys Chem A
May 2017
Department of Chemistry, Syracuse University , 1-014 Center for Science and Technology, Syracuse, New York 13244-4100, United States of America.
Through a combined experimental and theoretical investigation we determine that the fundamental modes of three quinacridones fall in the terahertz spectral range (1-10 THz, ∼30-300 cm). In each spectrum the terahertz resonances correspond to wagging, rocking, or twisting of the quinacridone rings, with the most intense absorption being an in-plane rocking vibration of the carbonyl oxygens. In spite of these spectral similarities, we demonstrate that terahertz measurements readily differentiate β-quinacridone, γ-quinacridone, and 2,9-dimethylquinacridone.
View Article and Find Full Text PDFJ Org Chem
April 2017
Department of Chemistry, 1-014 Center for Science and Technology, Syracuse University, Syracuse, New York 13244, United States.
The rearrangement of allylic trichloroacetimidates is a well-known transformation, but the corresponding rearrangement of benzylic trichloroacetimidates has not been explored as a method for the synthesis of benzylic amines. Conditions that provide the trichloroacetamide product from a benzylic trichloroacetimidate in high yield have been developed. Methods were also investigated to transform the trichloroacetamide product directly into the corresponding amine, carbamate, and urea.
View Article and Find Full Text PDFForensic Sci Int Genet
March 2017
Forensic & National Security Sciences Institute, College of Arts and Sciences, Syracuse University, 107 College Place 1-014 Center for Science and Technology, Syracuse, NY, 13244, USA.
The deconvolution of DNA mixtures remains one of the most critical challenges in the field of forensic DNA analysis. In addition, of all the data features required to perform such deconvolution, the number of contributors in the sample is widely considered the most important, and, if incorrectly chosen, the most likely to negatively influence the mixture interpretation of a DNA profile. Unfortunately, most current approaches to mixture deconvolution require the assumption that the number of contributors is known by the analyst, an assumption that can prove to be especially faulty when faced with increasingly complex mixtures of 3 or more contributors.
View Article and Find Full Text PDFJ Phys Chem A
September 2016
Department of Chemistry, Syracuse University , 1-014 Center for Science and Technology, Syracuse, New York 13244-4100, United States.
The ability of l-glutamic acid to crystallize in two different forms has long been the subject of study due to its commercial importance. While a solvent-mediated phase transformation between the α and β polymorphs is the prevailing theory, recent reports indicate a thermal solid-solid transformation between the two may be possible. However, determining accurate thermodynamic stabilities of these crystals has been challenging.
View Article and Find Full Text PDFJ Phys Chem A
September 2016
Department of Chemistry, Syracuse University , 1-014 Center for Science and Technology, Syracuse, New York 13244, United States.
Benzene, toluene, ethylbenzene, and xylenes (BTEX) are important organic pollutants. These compounds do not undergo direct photolysis in natural waters because their absorbance spectra do not overlap with solar radiation at the Earth's surface. Recent research has suggested that benzene is able to undergo direct photolysis when present at ice surfaces.
View Article and Find Full Text PDFJ Org Chem
September 2016
Department of Chemistry, 1-014 Center for Science and Technology, Syracuse University, Syracuse, New York 13244, United States.
An intermolecular alkylation of sulfonamides with trichloroacetimidates is reported. This transformation does not require an exogenous acid, base, or transition metal catalyst; instead the addition occurs in refluxing toluene without additives. The sulfonamide alkylation partner appears to be only limited by sterics, with unsubstituted sulfonamides providing better yields than more encumbered N-alkyl sulfonamides.
View Article and Find Full Text PDFOrg Lett
August 2016
Department of Chemistry, Syracuse University , 1-014 Center for Science and Technology, Syracuse, New York 13244, United States.
The pyrroloindoline core is found in many natural products. These structures often differ at the C3a position, which may be substituted with an oxygen, nitrogen, or sp(3)- or sp(2)-hybridized carbon. Utilizing a trichloroacetimidate leaving group, a diversity-oriented approach to these structures has been developed.
View Article and Find Full Text PDFJ Phys Chem A
August 2016
Department of Chemistry, Syracuse University , 1-014 Center for Science and Technology, Syracuse, New York 13244-4100, United States.
d-Mannitol, a common bulking agent used in the pharmaceutical and food industries, is known to crystallize in three anhydrous polymorphs (α, β, and δ) and a hemihydrate form. In this work, solid-state density functional theory simulations and experimental terahertz spectroscopy were used to evaluate the stabilities, thermodynamic relationships, and spectral signatures of these various solids. The thermodynamic analyses of the anhydrous polymorphs identified enantiotropic transitions for β-δ at approximately room temperature and α-δ near the α melting point, but showed α and β to be monotropically related.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
June 2016
Department of Chemistry, Syracuse University, 1-014 Center for Science and Technology, Syracuse, NY, 13244-4100, USA.
The rigidity of poly-l-proline is an important contributor to the stability of many protein secondary structures, where it has been shown to strongly influence bulk flexibility. The experimental Young's moduli of two known poly-l-proline helical forms, right-handed all-cis (Form I) and left-handed all-trans (Form II), were determined in the crystalline state by using an approach that combines terahertz time-domain spectroscopy, X-ray diffraction, and solid-state density functional theory. Contrary to expectations, the helices were found to be considerably less rigid than many other natural and synthetic polymers, as well as differing greatly from each other, with Young's moduli of 4.
View Article and Find Full Text PDFPhys Chem Chem Phys
February 2016
Department of Chemistry, Syracuse University, 1-014 Center for Science and Technology, Syracuse, NY 13244-4100, USA.
Low-barrier hydrogen bonds (LBHBs) are key components in a range of chemical processes, often appearing in metal-mediated catalytic applications. The formation of LBHBs has generally been attributed to the particular geometric arrangement of the surrounding atoms and molecules, yet few specific atomic-level details have emerged. In this study, several metal maleate tetrahydrates have been studied using a combination of solid-state density functional theory, terahertz spectroscopy, and X-ray diffraction to evaluate the significance of both water molecules and metal cations in guiding LBHB formation and function.
View Article and Find Full Text PDFJ Phys Chem A
February 2016
Department of Chemistry, Syracuse University , 1-014 Center for Science and Technology, Syracuse, New York 13244-4100, United States.
The problem of nonlocal interactions in density functional theory calculations has in part been mitigated by the introduction of range-corrected functional methods. While promising solutions, the continued evaluation of range corrections in the structural simulations of complex molecular crystals is required to judge their efficacy in challenging chemical environments. Here, three pyridinium-based crystals, exhibiting a wide range of intramolecular and intermolecular interactions, are used as benchmark systems for gauging the accuracy of several range-corrected density functional techniques.
View Article and Find Full Text PDFJ Phys Chem A
January 2016
Department of Chemistry, Syracuse University , 1-014 Center for Science and Technology, Syracuse, New York 13244-4100, United States.
Terahertz vibrational spectroscopy has evolved into a powerful tool for the detection and characterization of transition metal sulfate compounds, specifically for its ability to differentiate between various hydrated forms with high specificity. Copper(II) sulfate is one such system where multiple crystalline hydrates have had their terahertz spectra fully assigned, and the unique spectral fingerprints of the forms allows for characterization of multicomponent systems with relative ease. Yet the most commonly occurring form, copper(II) sulfate pentahydrate (CuSO4·5H2O), has proven elusive due to the presence of a broad absorption across much of the terahertz region, making the unambiguous identification of its spectral signature difficult.
View Article and Find Full Text PDFOrg Biomol Chem
February 2016
Department of Chemistry, 1-014 Center for Science and Technology, Syracuse University, Syracuse, New York 13244, USA.
Alcohols are effectively converted to their corresponding diphenylmethyl (DPM) ethers by reaction with O-diphenylmethyl trichloroacetimidate in refluxing toluene without the requirement of a catalyst or other additives. A number of acid and base sensitive substrates were protected in excellent yield using this new method without disturbing the pre-existing functionality present in these molecules. This reaction is the first example of the formation of an ether from stoichiometric amounts of a trichloroacetimidate and an alcohol without the addition of a Brønsted or Lewis acid catalyst.
View Article and Find Full Text PDFPhys Chem Chem Phys
December 2015
Department of Chemistry, Syracuse University, 1-014 Center for Science and Technology, Syracuse, NY 13244-4100, USA.
Metal-aqua ion ([M(H2O)n](X+)) formation is a fundamental step in mechanisms that are central to enzymatic and industrial catalysis. Past investigations of such ions have yielded a wealth of information regarding their properties, however questions still exist involving the exact structures of these complexes. A prominent example of this is hexaaqua copper(II) ([Cu(H2O)6](2+)), with the solution versus gas-phase configurations under debate.
View Article and Find Full Text PDFJ Chem Phys
October 2015
Dipartimento di Chimica, Università di Torino and NIS, Nanostructured Interfaces and Surfaces, Centre of Excellence, Via Giuria 5, 10125 Torino, Italy.
An automated computational strategy is devised for the ab initio determination of the full fourth-rank piezo-optic tensor of crystals belonging to any space group of symmetry. Elastic stiffness and compliance constants are obtained as numerical first derivatives of analytical energy gradients with respect to the strain and photo-elastic constants as numerical derivatives of analytical dielectric tensor components, which are in turn computed through a Coupled-Perturbed-Hartree-Fock/Kohn-Sham approach, with respect to the strain. Both point and translation symmetries are exploited at all steps of the calculation, within the framework of periodic boundary conditions.
View Article and Find Full Text PDFBioorg Med Chem Lett
November 2015
Department of Chemistry, Syracuse University, 1-014 Center for Science and Technology, Syracuse, NY 13244-4100, USA.
Recently, inhibition of the SH2-containing inositol 5'-phosphatase 1 (SHIP1) has become an attractive strategy for facilitating engraftment of MHC-I mismatched bone marrow grafts, increasing the number of adult stem cells in vivo, and inducing mobilization of hematopoietic stem cells. Utilizing high-throughput screening, two quinoline small molecules (NSC13480 and NSC305787) that inhibit SHIP1 enzymatic activity were discovered. New syntheses of these inhibitors have been developed which verified the relative stereochemistry of these structures.
View Article and Find Full Text PDFJ Org Chem
August 2015
Department of Chemistry, 1-014 Center for Science and Technology, Syracuse University, Syracuse, New York 13244, United States.
An efficient synthetic strategy for the regiospecific silylvinylation of internal alkynes is described. This transformation is catalyzed by RuHCl(CO)(SIMes)PPh3 and provides a net 5-exo-dig trans-silylvinylation of internal alkynes. Ethylene was used to decrease reaction times and displayed altered selectivity at increased pressure.
View Article and Find Full Text PDFOrg Lett
June 2015
Department of Chemistry, 1-014 Center for Science and Technology, Syracuse University, Syracuse, New York 13244, United States.
The intramolecular trans-silylruthenation of internal alkynes and subsequent insertion of vinyl boronates is described. This approach provides complete regiocontrol through a stereoselective trans-5-exo-dig cyclization which affords a tetrasubstituted olefin as a vinylsilane and a highly functionalized Z,E diene motif.
View Article and Find Full Text PDFJ Phys Chem B
July 2015
†Department of Chemistry, University at Albany, State University of New York, 1400 Washington Avenue, Albany, New York 12222, United States.
Amyloid fibril polymorphism is not well understood despite its potential importance for biological activity and associated toxicity. Controlling the polymorphism of mature fibrils including their morphology and supramolecular chirality by postfibrillation changes in the local environment is the subject of this study. Specifically, the effect of pH on the stability and dynamics of HET-s (218-289) prion fibrils has been determined through the use of vibrational circular dichroism (VCD), deep UV resonance Raman, and fluorescence spectroscopies.
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