Papers by Arbin Rajbanshi
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Supramolecular synthesis relies upon the creative and rational use of the common intermolecular f... more Supramolecular synthesis relies upon the creative and rational use of the common intermolecular forces and a proper understanding of these forces is critical for design and assembly of molecular building blocks into extended networks. The strength of seven substituted pyridines as hydrogen-bond acceptors was probed using a series of fifteen mono/dicarboxylic acids to demonstrate the interrelationship between the charge on the substrate and its ability to form co-crystals/salts. The higher charge in the acceptor led to proton transfer (100% yield) from the hydrogen bond donor to give a salt, whereas the lower charge led to co-crystals. This specificity observed for small molecules was extended to an investigation of selectivity in ditopic molecules. A series of nineteen hydrogen-bond donors, including fifteen carboxylic acids and four cyanoximes, were tested for binding preferences against ten ditopic ligands with variable charges. The overall supramolecular yield of 82% (9/11) prove...
Co-crystallization of two urea-functionalized ligands with tetrabutylammonium (TBA) dihydrogen ph... more Co-crystallization of two urea-functionalized ligands with tetrabutylammonium (TBA) dihydrogen phosphate resulted in the isolation of discrete (H<sub>2</sub>PO<sub>4</sub><sup>–</sup>)<sub>4</sub> and (H<sub>2</sub>PO<sub>4</sub><sup>–</sup>)<sub>6</sub> clusters stabilized in the crystalline state by multiple urea hydrogen bonds. Structural analysis by single-crystal X-ray diffraction, combined with a Cambridge Structural Database survey of (H<sub>2</sub>PO<sub>4</sub><sup>–</sup>)<sub><i>n</i></sub> aggregates, established that these clusters display unique topologies and hydrogen-bonding connectivities
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
4.1. Synthetic procedure for 1,3-Dicyclohexyl-2-(isotridecyl)guanidine hydrochloride. ...... 4.2.... more 4.1. Synthetic procedure for 1,3-Dicyclohexyl-2-(isotridecyl)guanidine hydrochloride. ...... 4.2. GC chromatogram of crude DCiTG with retention time and compound assignments .... 4.3. The free base has a decomposition onset at ºC while the hydroxide is at 275 ºC and hydrochloride is at 282 ºC.
Separation Science and Technology
The purity, concentration, and source of the N,N’-dicyclohexyl-N”-isotridecylguanidine (DCiTG) su... more The purity, concentration, and source of the N,N’-dicyclohexyl-N”-isotridecylguanidine (DCiTG) suppressor (guanidine) used in the NG-CSSX processwere found to influence solvent performance.Asthe starting isotridecanol used in the preparation of DCiTG is comprised of a mixture of branched-chain aliphatic alcohols, varying in composition with manufacturer, the resulting DCiTG itself is a mixture. Thus, it is necessary to address how the solvent performance will be affected by the different preparations of the DCiTG solvent component. In this study, four preparations of DCiTG from three sources were analyzed and evaluated for purity and performance, both in the absence and presence of a deliberately added anionic surfactant impurity.
Crystal Growth & Design, 2014
The thermodynamics and kinetics of crystallization of sodium sulfate with a tripodal tris-urea re... more The thermodynamics and kinetics of crystallization of sodium sulfate with a tripodal tris-urea receptor (L1) from aqueous alkaline solutions have been measured in the 15−55°C temperature range for a fundamental understanding of the elementary steps involved in this sulfate separation method. The use of radiolabeled Na 2 35 SO 4 provided a practical way to monitor the sulfate concentration in solution by β liquid scintillation counting. Our results are consistent with a two-step crystallization mechanism, involving relatively quick dissolution of crystalline L1 followed by the rate-limiting crystallization of the Na 2 SO 4 (L1) 2 (H 2 O) 4 capsules. We found that temperature exerted relatively little influence over the equilibrium sulfate concentration, which ranged between 0.004 and 0.011 M. This corresponds to 77−91% removal of sulfate from a solution containing 0.0475 M initial sulfate concentration, as found in a typical Hanford waste tank. The apparent pseudo-first-order rate constant for sulfate removal increased 20-fold from 15 to 55°C, corresponding to an activation energy of 14.1 kcal/mol. At the highest measured temperature of 55°C, 63% and 75% of sulfate was removed from solution within 8 and 24 h, respectively. These results indicate the capsule crystallization method is a viable approach to sulfate separation from nuclear wastes.
Supramolecular Chemistry, 2011
A tripodal trisurea receptor (L1) persistently self-assembles with various divalent oxoanion salt... more A tripodal trisurea receptor (L1) persistently self-assembles with various divalent oxoanion salts MnX (M = Na, K, Mg, Ca, Cd; X = SO4 , SO3 , SeO4 , CrO4 ) into isomorphous series of crystalline frameworks in three different compositions: MX(L1)2(H2O)6 (M = Mg, Ca, Cd) (1), Na2X(L1)2(H2O)4 (2) and K2X(L1)2(H2O)2 (3). Single-crystal X-ray structural analysis revealed that all three series of structures adopt a NaCl-type
CrystEngComm, 2010
Abstract In order to examine the balance between co-crystallization and proton transfer in a set ... more Abstract In order to examine the balance between co-crystallization and proton transfer in a set of acidbase reactions, molecular electrostatic potential (MEP) surface calculations for substituted pyridines were correlated with their ability to communicate with a series of ...
CrystEngComm, 2012
A halogen-bonded capsule is obtained via directed assembly of a rigid tetra(3-pyridyl) cavitand a... more A halogen-bonded capsule is obtained via directed assembly of a rigid tetra(3-pyridyl) cavitand and a flexible tetra(4iodotetrafluorophenyl)calix[4]arene. The pyridyl nitrogen atoms from one cavitand molecule interact with the iodine atoms of a 40 of capsules is highly desirable.
CrystEngComm, 2012
ABSTRACT A correlation between the electrostatic charge on the hydrogen-bond acceptor sites of 2-... more ABSTRACT A correlation between the electrostatic charge on the hydrogen-bond acceptor sites of 2-aminopyrazine derivatives and the ability of the compound to form intermolecular hydrogen bonds with carboxylic acids in the solid state has been established. The charge on the hydrogen-bond acceptor can be modulated which leads to a predictable lowering of the supramolecular yield of the reaction. The outcome of all reactions was screened using IR spectroscopy, and twelve new crystal structures are reported to verify the spectroscopic assignments, and to examine the exact nature of the primary intermolecular interactions. The binding preference of carboxylic acids towards the two possible binding sites of 2-aminopyrazines has also been examined, and the main driving force for the assembly of the heteromer between bases and carboxylic acids is the two-point O–HN/OH–N synthon. However, seven out of twelve times carboxylic acids also bind via a single-point O–HN synthons. This ‘synthon crossover’ is unavoidable due to highly competitive binding sites present in the N-heterocyclic bases chosen.
Crystal Growth & Design, 2013
All reagents and solvents were purchased from commercial sources and used as received without fur... more All reagents and solvents were purchased from commercial sources and used as received without further purification. The ethyl and n-butyl isocyanates were purchased from Aldrich, whereas 2-nitrophenyl isocyanate was purchased from Acros Organics. 1 H NMR and 13 C NMR spectra were collected on a Bruker 400 MHz Advance III spectrometer in d 6-DMSO. Melting points were measured on a Uni-Melt Thomas Hoover capillary melting point apparatus and are uncorrected. Elemental analyses were performed by Galbraith Laboratories, Inc.
Crystal Growth & Design, 2011
Crystal Growth & Design COMMUNICATION cations to hold the capsules together in the solid state, w... more Crystal Growth & Design COMMUNICATION cations to hold the capsules together in the solid state, which provided enhanced stabilities in aqueous solutions with high sodium concentrations and strongly basic pH. As these conditions are very similar to those found in nuclear wastes, the results reported here promise to provide in the near future the basis for a viable technology for sulfate separation from such wastes. ' ASSOCIATED CONTENT b S Supporting Information. Crystallographic data in CIF format, details of the X-ray structural determinations, synthetic procedures, sulfate separation and ligand recovery experiments. This material is available free of charge via the Internet at http:// pubs.acs.org.
Crystal Growth & Design, 2009
A family of supramolecular reagents containing two different binding sites, pyridine and aminopyr... more A family of supramolecular reagents containing two different binding sites, pyridine and aminopyrimidine, were allowed to react with iodo-or bromo-substituted benzoic acids in order to assemble individual molecules into larger architectures with precise intermolecular interactions, using a combination of hydrogen-and halogen-bonds. The hydrogen-bond based amino-pyrimidine/ carboxylic acid or amino-pyrimidinium/carboxylate synthons are responsible for the assembly of the primary structural motif in every case (7/7 times, 100% supramolecular yield), while I⋯N, Br⋯N, and I⋯O, halogen bonds play a structural supporting role by organizing these supermolecules into extended 1-D and 2-D architectures (5/7 times, 71% supramolecular yield). These results illustrate how two different non-covalent interactions can be employed side-by-side in the reliable construction of extended molecular solid-state networks with predictable connectivity and dimensionality.
Chemical Communications, 2011
Separation Science and Technology
Crystallization of urea-functionalized capsules self-assembled from a tripodal anion receptor(L1)... more Crystallization of urea-functionalized capsules self-assembled from a tripodal anion receptor(L1) was evaluated as a means to selectively separate sulfate from aqueous alkaline solutions simulating Hanford waste compositions. The crystallizing solids consist of anionic SO4(L1)2 capsules, and Mg(H2O)6 or Na2(H2O)4 hydrated cations,alternating in three-dimensional frameworks with NaCl-type topology. While both frameworks encapsulate sulfate selectively upon crystallization through the formation of complementary hydrogen bonds from the urea groups, the separation efficacy depends strongly on the nature of the cation, the pH, and the nature and concentration of competing anions in the solution. Crystallization of the Mg-based capsulesprovides an efficient sulfate separation from mildly alkaline solutions (pH
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Papers by Arbin Rajbanshi