Chemistry Commons^™

Supramolecular Pi-Donor/Acceptor Arrays Based On Redox-Active Metal-Organic Coordination Assemblies, Paola Benavides

All Dissertations

Coordination-driven self-assembly is an attractive strategy for constructing thermodynamically stable supramolecular coordination complexes, ranging from discrete metallacycles and cages to infinite coordination polymers and metal-organic frameworks for a variety of applications.

Chapter 1 discusses strategies for preparing supramolecular charge-transfer π-donor/acceptor assemblies and their potential applications.

Chapter 2 demonstrates that tricomponent self-assembly method, which was believed to yield 3D-cages, based on tetrapyridyl porphyrin (M’TPP, M’ = Zn or H₂), dicarboxylate ligands (XDC), and caped cis-Pt(II) corners, actually yields 2D-bowties featuring an M’TPP core and two parallel XDC linkers held together by four heteroligated PtII(N,O) corners. The 2D-bowties showed …

Well–Defined Donor–Acceptor Materials, Gabrielle A. Leith

Theses and Dissertations

The modularity of multivariant scaffolds such as covalent–organic frameworks (COFs) provides an unprecedented level of control in the alignment of donor (D) and acceptor (A) units, a demand that is driven by the production of optoelectronic, photonic, and spintronic devices. The foray into novel motifs bearing D-A ensembles in frameworks has been applied towards material property modulation for device performance enhancement. This dissertation presents an emerging trend in the development of D-A interfaces by highlighting recent advances probing D-A interactions in porous crystalline matrices and co-crystals, with a focus on energy transfer (ET) and charge transfer (CT) processes in pre-designed …

Radial Basis Densities And The Density Functional-Based Atom-In-Molecule: Designing Charge-Transfer Potentials, Godwin Amo-Kwao

Nanoscience and Microsystems ETDs

Classical potentials that are capable of describing charge transfer and charge polarization in complex systems are of central importance for classical atomistic simulation of biomolecules and materials. Current potentials—regardless of the system—do not generalize well, and, with the exception of highly-specialized empirical potentials tuned for specific systems, cannot describe chemical bond formation and breaking. The charge-transfer embedded atom method (CT-EAM), a formal, DFT-based extension to the original EAM for metals, has been developed to address these issues by modeling charge distortion and charge transfer in interacting systems using pseudoatom building blocks instead of the electron densities of isolated atoms. CT-EAM …

Fragment-Based Excitonic Coupled-Cluster Theory For Large Chemical Systems, Yuhong Liu

University of the Pacific Theses and Dissertations

Accurate energetic modeling of large molecular systems is always desired by chemists. For example, ligand-protein binding simulations and enzymatic catalysis studies all involve with a small energy difference. The energetic accuracy depends largely on a proper handling of electronic correlations. Molecular mechanics (MM) methods deliver a parameterized Newtonian treatment to these problems. They show great capability in handling large calculations but give only qualitatively good results. Quantum mechanics (QM) methods solve Schrödinger equations and exhibit much better energy accuracy, though the computational cost can be prohibitive if directly applied to very large systems.

Fragment-based methods have been developed to decompose …

Incorporation Of Charge Transfer Into Classical Molecular Dynamics Force Fields With Applications In Physical Chemistry., Marielle Soniat

University of New Orleans Theses and Dissertations

The presence of charge transfer (CT) interactions is clear in a variety of systems. In CT, some electron density is shifted from one molecule to another (non-bonded) molecule. The importance of this CT interaction is unclear. Previous attempts to look at the conse- quences of CT required the use of ab initio molecular dynamics (AIMD), a computationally intensive method. Herein, a method for including CT in force field (FF) simulations is described. It is efficient, produces charges in agreement with AIMD, and prevents long- ranged CT.

This CT MD method has been applied to monatomic ions in water. When solvated, …

Experimental And Theoretical Studies Of Binding Interactions In Divalent Transition Metal Cation-N-Donor Ligand Complexes: Structures, Sequential Bond Dissociation Energies, Mechanisms And Energetics Of Collision-Induced Dissociation, Holliness Nose

Wayne State University Dissertations

The thesis research described here involves a series of experiments that have been designed to probe the influence of the electronic structure of the metal cation, the nature and number of ligands, as well as the effects of chelation and steric interactions on the geometry and binding strength of transition metal cation-ligand complexes. The experimental studies make use of energy-resolved collision-induced dissociation (CID) techniques that are carried out in a custom-built guided ion beam tandem mass spectrometer (GIBMS) to probe the structures, energetics, and fragmentation behavior of the complexes of interest. Electronic structure theory calculations including several density functional theory …

Siloles Bearing Coordination-Active 2,5-Substituents: Synthesis, Reactivity, Structural And Spectral Properties., James Bryan Carroll

Dissertations

Siloles, or silacyclopentadienes and other group 14 metalloles are structurally analogous to their all-carbon analogue, cyclopentadiene, except for the heavy group 14 element (i.e., Si, Ge, Sn, and Pb) in the 1-position. The placement of the heavy element in this position allows for unique properties, such as high electron affinity, mobility, and bathochromically shifted optical spectra, as compared to cyclopentadienes, and the relatively low-lying lowest-unoccupied molecular orbital (LUMO) helps to account for these properties. The substituents about the silole have a significant impact on the electronics and properties observed, with 2,5-substituents inducing the most substantive changes. Even as many 2,5-substituents …

Theoretical Approaches To The Characterization Of Water, Aqueous Interfaces, And Improved Sampling Of Protein Conformational Changes, Alexis J. Lee

University of New Orleans Theses and Dissertations

Methods to advance the understanding of water and other aqueous systems are devel- oped. This work falls into three areas: The creation of better interaction potentials for water, improved methods for sampling configurational space, and the applications of these methods to understand systems of interest. Charge transfer has been shown by ab initio methods to be important in the water–water and water–ion interactions. A model for treating charge transfer in liquid water and aqueous systems is presented in this manuscript. The model is called Discrete Charge Transfer (DCT) and is based on the commonly-used TIP4P/2005 model, which represents the charge …

Mechanistic Studies On Xanthine Oxidoreductase Enzymes, Abebe Berhane

Chemistry and Chemical Biology ETDs

In humans, the xanthine oxidoreductase enzymes are known to catalyze the final two steps of purine metabolism by converting hypoxanthine successively to xanthine and uric acid. Xanthine oxidoreductase also metabolizes a wide variety of drugs in vivo, and activates a number of antiviral prodrugs of clinical importance. Therefore, understanding the reaction mechanism of this enzyme is of prime importance in furthering our understanding of enzyme-drug interactions. In order to provide a greater understanding on the reaction mechanism, theoretical and enzymatic spectroscopic experimental approaches have been utilized. The theoretical approaches were used to elucidate the electronic structure and geometry of the …