Leveraging Non-Covalent Interactions between Small Organic Molecules and Inorganic Scaffolds in the Design of Advanced Materials

Powder diffraction is a powerful tool for studying crystal structures, especially as it relates to interactions of small organic molecules with inorganic compounds. The first part of this dissertation involves small organic ligands interacting with metal-organic framework, MOF-74. The first and simplest iteration involves the crystal structure solution of a neat, liquid loading of n-propylmercaptan to the open metal sites within the MOF-74 pores. Later studies investigate the leveraging of a similarly sized bitopic ligand in the solution loading of 1,2-ethanedithiol, which results in the amorphization of MOF-74. Having no crystallinity, amorphous or severely defected materials can be a challenge to study. Herein, our studies reveal that the defects occur via protonation of the native framework and dislocation of the metal cations. The result is a material with fluorescent properties and quenching specific to the exposure to aqueous silver(I). Additionally, defected MOF-74 remains porous upon loadings of up to 10%. In the second portion of this dissertation, the family of cobalt(II) hydroxide materials was explored utilizing an interesting ligand candidate, sorbate. The neat packing observed in other sorbate compounds lends itself to the organizing of densely packed hybrid layers in cobalt(II) hydroxide sorbate [Co(OH)(sorb)]. Due to the cluster-forming habit of Co(OH)(sorb), the structure is solved by powder diffraction techniques. Additionally, a transformation of the material after exposure to high pressures is explored. The material is determined to be antiferromagnetic below 41.7 K with a large hysteric effect indicative of canted antiferromagnetic ordering. The final section of this dissertation will be pure structure solution of two important chemicals of the last century, zineb and potassium sorbate. Zineb is a fungicide which has found use since 1943, where it was marketed under the tradename Dithane Z-78. Despite such a long tenure of use, the crystal structure remained unsolved for decades. Using powder techniques, we can solve the crystal structure, which serves as a proxy to the other fungicides in this family. Additionally, the food preservative, potassium sorbate, crystallizes in a polycrystalline fashion, explaining the lack of crystal structures present in major crystallography databases. Potassium sorbate’s crystal structure is solved as a complement to the cobalt(II) hydroxide hybrid material research, but also to understand why potassium sorbate doesn’t undergo topochemical reactions. The crystal structure reveals misaligned π-orbitals, precluding any reactivity toward polymeric or [2+2] dimer products

Leveraging Non-Covalent Interactions between Small Organic Molecules and Inorganic Scaffolds in the Design of Advanced Materials

Powder diffraction is a powerful tool for studying crystal structures, especially as it relates to interactions of small organic molecules with inorganic compounds. The first part of this dissertation involves small organic ligands interacting with metal-organic framework, MOF-74. The first and simplest iteration involves the crystal structure solution of a neat, liquid loading of n-propylmercaptan to the open metal sites within the MOF-74 pores. Later studies investigate the leveraging of a similarly sized bitopic ligand in the solution loading of 1,2-ethanedithiol, which results in the amorphization of MOF-74. Having no crystallinity, amorphous or severely defected materials can be a challenge to study. Herein, our studies reveal that the defects occur via protonation of the native framework and dislocation of the metal cations. The result is a material with fluorescent properties and quenching specific to the exposure to aqueous silver(I). Additionally, defected MOF-74 remains porous upon loadings of up to 10%. In the second portion of this dissertation, the family of cobalt(II) hydroxide materials was explored utilizing an interesting ligand candidate, sorbate. The neat packing observed in other sorbate compounds lends itself to the organizing of densely packed hybrid layers in cobalt(II) hydroxide sorbate [Co(OH)(sorb)]. Due to the cluster-forming habit of Co(OH)(sorb), the structure is solved by powder diffraction techniques. Additionally, a transformation of the material after exposure to high pressures is explored. The material is determined to be antiferromagnetic below 41.7 K with a large hysteric effect indicative of canted antiferromagnetic ordering. The final section of this dissertation will be pure structure solution of two important chemicals of the last century, zineb and potassium sorbate. Zineb is a fungicide which has found use since 1943, where it was marketed under the tradename Dithane Z-78. Despite such a long tenure of use, the crystal structure remained unsolved for decades. Using powder techniques, we can solve the crystal structure, which serves as a proxy to the other fungicides in this family. Additionally, the food preservative, potassium sorbate, crystallizes in a polycrystalline fashion, explaining the lack of crystal structures present in major crystallography databases. Potassium sorbate’s crystal structure is solved as a complement to the cobalt(II) hydroxide hybrid material research, but also to understand why potassium sorbate doesn’t undergo topochemical reactions. The crystal structure reveals misaligned π-orbitals, precluding any reactivity toward polymeric or [2+2] dimer products

The Crystal Structure of Zineb, 75 years later

Ethylene bis(dithiocarbamates) (EBDTCs) have been used as staple fungicides for over 75 years. The first industrially manufactured EBDTC was zineb, zinc ethylene bis(dithiocarbamate), marketed under the tradename Dithane. Even though zineb has been used as a fungicide since the 1940s, its crystal structure remained unknown. Herein, we describe the crystal structure of zineb (triclinic crystal system, space group P–1, a = 7.5094(9) Å, b = 9.4356(9) Å, c = 7.4120(7) Å, α = 107.945(8) °, β = 100.989(7) °, γ = 105.365(8) °, V = 460.07(10) Å3). The inorganic fragment of the structure consists of two Zn2+ cations, coordinated by the thiocarbamate group. There are four Zn–S bonds with lengths in the range of 2.325 – 2.426 Å, and one rather long Zn–S contact of 2.925(8) Å. Inorganic fragments are linked by organic EBDTC ligands to form extended, polymeric layers. The layers are packed in a ABAB manner, related by the inversion symmetry and held together by hydrogen bonding network. In this article, in addition to describing the crystal structure, we correlate the structural features with the vibrational spectroscopic and thermal characteristics of zineb, and we provide a short summary of the major developments of fungicides in the 20th century<br /

Computing and Video Games

Lew Lefton, from the Georgia Tech School of Mathematics joins us to talk about scientific and vector computing. Ironically, many of the fastest parallel computations use the very same graphics boards that make your avatar look cool in your favorite video game. Lew teaches parallel and vector computing at Georgia Tech and is the co-author of An Introduction to Parallel and Vector Scientific Computation

Soluble Thiabendazolium Salts with Anthelminthic Properties

Thiabendazole is an anthelmintic drug used to treat strongyloidiasis (threadworm), cutaneous and visceral larva migrans, trichinosis, and other parasites. The active pharmaceutical ingredient is typically administered orally as tablets that should be chewed before swallowing. Current formulations combine the active ingredient with excipients, including sodium saccharinate as a sweetener. Thiabendazole’s low aqueous solubility hinders fast dissolution and absorption through the mucous membranes. We sought to reformulate this medicine to improve both solubility and palatability. We utilized the possibility of protonation of the azole nitrogen atom and selected four different hydrogen donors: saccharin, fumaric, maleic, and oxalic acids. Solvothermal syn-thesis resulted in salts with each co-former, whereas neat and liquid-assisted grinding enabled the synthesis of additional formulations. Product formation was observed by powder X-ray diffraction. To better understand the structural basis of the proton transfer, we solved the crystal structures of the salts with saccharin, maleic acid, and oxalic acid using single-crystal X-ray diffraction. The structure of the salt with fumaric acid was solved by powder X-ray diffraction. We further characterized the salts with vibrational spectroscopic and thermoanalytical methods. We report a broad tunability of the aqueous solubility of thiabendazole by salt formation. Reformulation with maleic acid provided a 60-fold increase in solubility, while saccharin and oxalic acid gave a modest improvement. Fumaric acid resulted in a solid with only slightly higher solubility. Fur-thermore, saccharin is a sweetener, while the acids taste sour. Therefore, the salts formed also result in an in-trinsic improvement of palatability. These results can inform new strategies for oral and chewable tablet for-mulations for treating helminthic infections

Mechanosynthesis of a Coamorphous Formulation of Creatine with Citric Acid and Humidity–Mediated Transformation into a Cocrystal

We report a simple, efficient, and scalable mechanochemical method of preparation of new creatine fitness supplement with increased solubility (compared to the creatine monohydrate) and decreased acidity (compared to creatine hydrochloride)

Defects Formation and Amorphization of Zn-MOF-74 Crystals by Post-Synthetic Interactions with Bidentate Adsorbates

The controlled introduction of defects into MOFs is a powerful strategy to induce new physiochemical properties and improve their performance for target applications. Herein, we present a new strategy for defect formation and amorphization.<br /

Deep eutectic solvents comprising creatine and citric acid and their hydrated mixtures

We report the phase diagram for the binary creatine–citric acid mixture which features a stable and broad eutectic region. Combinations containing 10–60 mol% creatine yield a deep eutectic solvent with a glass transition temperature at 270 K. Addition of up to 70 mol% water to the binary mixture affords retention of the eutectic nature and a handle to vary solvent viscosity and polarity

Peritectic Phase Transition of Benzene and Acetonitrile and Formation of a Cocrystal Relevant to Titan, Saturn’s Icy Moon

Benzene and acetonitrile are two of the most commonly used solvents found in almost every chemical laboratory. Titan, Saturn’s icy moon, is one other place in the Solar system that has even larger amounts of these compounds, together with many other hydrocarbons. On Titan, organic molecules are produced in the atmosphere and carried by methane rainfall to the surface, where they either dissolve in the lakes, deposit as sandy dunes, or solidify as minerals with complex composition and structure. In order to untangle these structural complexities a reliable model of the phase behavior of these compounds at temperatures relevant to Titan is crucial. We therefore report the composition–temperature binary phase diagram of acetonitrile and benzene, and provide a detailed account of the structure and composition of the phases. This work is based on differential scanning calorimetry and in situ powder diffraction analyses with synchrotron X-ray radiation and supported by theoretical modeling. Benzene and acetonitrile were found to undergo a peritectic reaction into a cocrystal with a 1:3 acetonitrile:benzene stoichiometry. The crystal structure was solved and refined in the polar space group, R3, and the solution was confirmed and optimized by energy minimization calculations. To mimic the environment on Titan more accurately, we tested the stability of the structure under liquid ethane. The diffraction data indicate that the cocrystal undergoes further change upon contact with ethane. These results provide new insights into the structure and stability of a potential mineral on Titan, and contribute to the fundamental knowledge of some of the smallest organic molecule

Model AI Assignments 2021

The Model AI Assignments session seeks to gather and disseminate the best assignment designs of the Artificial Intelligence (AI) Education community. Recognizing that assignments form the core of student learning experience, we here present abstracts of six AI assignments from the 2021 session that are easily adoptable, playfully engaging, and flexible for a variety of instructor needs. Assignment specifications and supporting resources may be found at http://modelai.gettysburg.edu