Computational Study of Substituent Effects on Organometallic and Inorganic Compounds: A Novel Class of Paramagnetic Chemical Exchange Saturation Transfer Agents, and Cyclic Phosphazenes

Organometallic and inorganic complexes have generated many opportunities and challenges for a variety of applications including medicine and materials. We intend to present a computational study of the effect of chemical modifications to novel classes of organometallic compounds. Specifically, we will investigate Magnetic Resonance Imaging (MRI) agents and a set of novel polyphosphazenes through electronic structure computational techniques. We will investigate the MRI imaging agent metal-water bonding complexes, along with the mechanism of water exchange. Also, through a series of similar quantum mechanical calculations we will investigate the complexes structure, transition states, interactions, and elucidate the formation mechanisms of polyphosphazenes.;In the first study we will investigate MRI contrast agents, which have the purpose of increasing the sensitivity of MRI experiments. These complexes usually consist of a paramagnetic metal center, such as Gadolinium (Gd), or Europium (Eu) bound to a ligand to enhance contrast and reduce toxicity. Ligands also introduce some properties that the metal alone would not have, which may be tuned to enhance MRI contrast agents. We will investigate properties which we hypothesize influence MRI contrast, and increase our understanding of the mechanism to better enable rational design of novel agents. Using Quantum Mechanics (QM) we will be able to elucidate the electronic effects on the bound water oxygen by varying ligands substituents. We will also be able to predict the NMR of the metal bound oxygen and it corresponding protons. This will give us a theoretical base prediction for the complexes. With this quantum mechanical information we can move on to investigating other effects on the observed contrast signal, such as bulk solvent, and rotational effects.;In the second study, we will investigate cyclic polyphosphazenes which have several applications to areas of biomedical research, as well as uses in material science. Scientist may take advantage of unique substitution patterns, to create novel compounds and materials, similar to the plethora of benzene derivatives. Specifically, we will investigate chemical modifications to a group of cyclic phosphazenes. We will attempt to understand the mechanism of forming the compounds, and general reactivity. Using QM electronic structure calculations similar to one employed to investigate MRI contrast agents, we will deduce the lowest energy structure and therefore general reactivity for various phosphazene derivatives. We will then combine the data to formulate a potential reaction path. These investigations will contribute to better understanding of general structure and function of organometallic and inorganic systems.