Infrared Spectroscopy of Li Solvation in Diglyme: Ab Initio Molecular Dynamics and Experiment.

Infrared (IR) spectra of solutions of the lithium salt LiBF in diglyme, CHO(CHCHO)CH, are studied via IR spectroscopy and ab initio molecular dynamics (AIMD) simulations. Experiments show that the major effects of LiBF, compared to neat diglyme, are the appearance of a new broad band in the 250-500 cm frequency region and a broadening and intensity enhancement of the diglyme band in the 900-1150 cm region accompanied by a red-shift. Computational analysis indicates that hindered translational motions of Li in its solvation cage are mainly responsible for the new far-IR band, while the changes in the mid-IR are due to Li-coordination-dependent B-F stretching vibrations of BF anions coupled with diglyme vibrations.

Infrared Spectroscopy of Li Solvation in EmimBF and in Propylene Carbonate: Ab Initio Molecular Dynamics and Experiment.

Infrared (IR) spectra of solutions of the lithium salt LiBF in the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF) and in the organic solvent propylene carbonate (PC) are studied via infrared spectroscopy and ab initio molecular dynamics (AIMD) simulations. The measurements show that the major effects of LiBF in both solutions, compared to their neat counterparts, are the appearance of a new broad band in the 300-450 cm frequency region and a broadening of the IR structure in the 900-1200 cm region with the development of a new peak at 980 cm. Computational analysis indicates that hindered translational motions of Li in its solvation cage are mainly responsible for the former, while the latter is due to Li-induced structural changes and accompanying vibrational frequency shifts of constituent ions and molecules of the solutions.

CS capture in the ionic liquid 1-alkyl-3-methylimidazolium acetate: reaction mechanism and free energetics.

Reaction pathways for CS2 and COS in the ionic liquid, 1-ethyl-3-methylimidazolium (EMI+) acetate (OAc-), are studied using the ab initio self-consistent reaction field theory (SCRF) and molecular dynamics (MD) computer simulations. It is found that while CS2 converts to COS nearly at the 100% level through S/O exchange with acetate, both conversion and capture processes are kinetically possible for COS, yielding CO2/thioacetate and 1-ethyl-3-methylimidazole-2-thiocarboxylate (EMI-COS)/acetic acid as reaction products, respectively. These findings are in excellent agreement with recent experimental observations in the closely related 1-butyl-3-methylimidazolium acetate (BMI+OAc-) ionic liquid system.

CO capture in ionic liquid 1-alkyl-3-methylimidazolium acetate: a concerted mechanism without carbene.

Ionic liquids (ILs) provide a promising medium for CO capture. Recently, the family of ILs comprising imidazolium-based cations and acetate anions, such as 1-ethyl-3-methylimidazolium acetate (EMIOAc), has been found to react with CO and form carboxylate compounds. N-Heterocyclic carbene (NHC) is widely assumed to be responsible by directly reacting with CO though NHC has not been detected in these ILs.

Understanding the mechanism of CO2 capture by 1,3 di-substituted imidazolium acetate based ionic liquids.

Efficient CO2 capture by ionic liquids needs a thorough understanding of underlying mechanisms of the CO2 interaction with ionic liquids, especially when it involves chemisorption. In this work we have systematically investigated the mechanism of CO2 capture by 1,3 di-substituted imidazolium acetate ionic liquids using density functional theory. Solvent effects are analyzed using QM/MM and QM/QM approaches with the help of molecular dynamics simulations and ONIOM methods.

Toward a Materials Genome Approach for ionic liquids: synthesis guided by ab initio property maps.

The Materials Genome Approach (MGA) aims to accelerate development of new materials by incorporating computational and data-driven approaches to reduce the cost of identification of optimal structures for a given application. Here, we use the MGA to guide the synthesis of triazolium-based ionic liquids (ILs). Our approach involves an IL property-mapping tool, which merges combinatorial structure enumeration, descriptor-based structure representation and sampling, and property prediction using molecular simulations.

Mapping of functional groups in metal-organic frameworks.

We determined the heterogeneous mesoscale spatial apportionment of functional groups in a series of multivariate metal-organic frameworks (MTV-MOF-5) containing BDC (1,4-benzenedicarboxylate) linkers with different functional groups--B (BDC-NH2), E (BDC-NO2), F [(BDC-(CH3)2], H [BDC-(OC3H5)2], and I [BDC-(OC7H7)2]--using solid-state nuclear magnetic resonance measurements combined with molecular simulations. Our analysis reveals that these methods discern between random (EF), alternating (EI and EHI), and various cluster (BF) forms of functional group apportionments. This combined synthetic, characterization, and computational approach predicts the adsorptive properties of crystalline MTV-MOF systems.

Understanding the effect of side groups in ionic liquids on carbon-capture properties: a combined experimental and theoretical effort.

Ionic liquids are an emerging class of materials with applications in a variety of fields. Steady progress has been made in the creation of ionic liquids tailored to specific applications. However, the understanding of the underlying structure-property relationships has been slower to develop.

Atomistic simulations of liquid crystal mixtures of alkoxy substituted phenylpyrimidines 2PhP and PhP14.

We study liquid crystal mixtures of alkoxy substituted phenylpyrimidines 2-[4-(butyloxy)phenyl]-5-(octyloxy)pyrimidine (2PhP) and 2-[4-(tetradecyloxy)phenyl]-5-(tetradecyloxy)pyrimidine (PhP14) using molecular dynamics simulations at the all atom level. The molecular length of PhP14 is 1.8 times that of 2PhP, resulting in an interesting binary mixture phase diagram.

Self-assembled chiral superstructures composed of rigid achiral molecules and molecular scale chiral induction by dopants.

We explore the phase behavior of a rigid achiral bent-core model system. Nematic and smectic phases form at higher densities, whereas micelles and columns composed of chiral clusters of these molecules self-assemble at lower densities. No nucleation mechanism requiring transient chirality is possible in the formation of these chiral superstructures due to the rigid achiral nature of the substituents.

Cation identity dependence of crown ether photonic crystal Pb2+ sensing.

We quantitatively modeled the volume phase transition of a hydrogel containing a crystalline colloidal array with a crown ether ligand which binds Pb2+. The hydrogel volume response and the wavelength diffracted depend on the Pb2+ concentration and on both the ionic strength and the valence of the nonbinding ionic species. We successfully modeled the response of this hydrogel Pb2+ sensor to ionic strength and the cation valence of the added salts.