Application of High-Level Computational Methods to Supramolecluar Systems: Determination of Conformational Preference for Dendrimers and Molecular Baskets
| Main Author: | |
|---|---|
| Language: | English |
| Published: |
The Ohio State University / OhioLINK
2012
|
| Subjects: | |
| Online Access: | http://rave.ohiolink.edu/etdc/view?acc_num=osu1338259027 |
| id |
ndltd-OhioLink-oai-etd.ohiolink.edu-osu1338259027 |
|---|---|
| record_format |
oai_dc |
| spelling |
ndltd-OhioLink-oai-etd.ohiolink.edu-osu13382590272021-08-03T06:05:17Z Application of High-Level Computational Methods to Supramolecluar Systems: Determination of Conformational Preference for Dendrimers and Molecular Baskets Turner, Daniel Andrew Chemistry <p>The field of supramolecular chemistry focuses on important non-covalent interactions that determine the organization of a chemical system. Supramolecular chemistry was initially inspired by nature, and researchers have developed synthetic systems based on supramolecular principles applicable to such fields as catalysis, materials technology and even medicine. Therefore, new scaffolds are continuously being developed and the focus of this thesis is on two systems: dendrimers and molecular baskets. </p><p>The properties of supramolecular systems are driven by non-covalent interactions; therefore, determining conformational preferences is critical. For optically active compounds, one common experimental method is circular dichroism (CD) spectroscopy, which measures the differential absorption of left-handed and right-handed circularly polarized light. Computational methods can provide useful information to experiment in order to understand secondary structure. This thesis focuses on computational studies, using density functional theory (DFT), to gain an insight into the important non-covalent interactions behind the conformational preferences of dendrimers and molecular baskets. </p><p>A series of dendrons based on a pyridine-2,6-dicarboxamide focal unit have been developed by the Parquette group. When the amides are functionalized with larger groups, these dendrons adopt enantiomeric P or M helical conformations; chirality on the periphery causes formation of one helical isomer. Based on these studies, they developed a series of dendrimers functionalized with L-prolineamide groups as catalysts for the direct aldol reaction. Through a combination of experimental and computational studies, we were able to observe amplification of the stereoselectivity due to the increasing M helical bias of the dendron.</p><p>Rather than having the periphery of the dendron act as a catalyst, chiral bisoxazoline dendrons were installed on a catalytic biphenyl core and used as catalysts for asymmetric rhodium hydrogenation. Computational studies indicated that the P helical bias of the dendron created a P bias at the biphenyl core, resulting in the S product. Additionally, we determined that the position of dendron on the biphenyl core greatly affects the conformation of the core and causes significant changes in enantioselectivity.</p><p>The Badjić group has developed a series of molecular baskets that can encapsulate small molecules. One type of these baskets has three pyridine “gates” at the top, held together by silver(I) cation in a C3v orientation. Installing a chiral group into the scaffold causes the gates to orient in one specific direction. In addition to experimental studies, we used DFT calculations to determine a P helical preference for gating. When quinoline gates were complexed with copper(II) cation, the basket adopted an unexpected C1-symmetric square-pyramidal geometry at the rim.</p><p>Two new scaffolds are presented in this thesis, one with a larger porphyrin base and the other based on a cyclialkylation reaction to create a twisted cavitand. Experimental and computational studies have been used to determine the preference for binding inside and outside of the porphyrin basket. Mechanistic studies were conducted on a model compound in order to determine the rate-limiting step for cyclialkylation, and computational studies provided insight into the rate-limiting step and other rearrangement pathways.</p> 2012-06-25 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1338259027 http://rave.ohiolink.edu/etdc/view?acc_num=osu1338259027 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |
| collection |
NDLTD |
| language |
English |
| sources |
NDLTD |
| topic |
Chemistry |
| spellingShingle |
Chemistry Turner, Daniel Andrew Application of High-Level Computational Methods to Supramolecluar Systems: Determination of Conformational Preference for Dendrimers and Molecular Baskets |
| author |
Turner, Daniel Andrew |
| author_facet |
Turner, Daniel Andrew |
| author_sort |
Turner, Daniel Andrew |
| title |
Application of High-Level Computational Methods to Supramolecluar Systems: Determination of Conformational Preference for Dendrimers and Molecular Baskets |
| title_short |
Application of High-Level Computational Methods to Supramolecluar Systems: Determination of Conformational Preference for Dendrimers and Molecular Baskets |
| title_full |
Application of High-Level Computational Methods to Supramolecluar Systems: Determination of Conformational Preference for Dendrimers and Molecular Baskets |
| title_fullStr |
Application of High-Level Computational Methods to Supramolecluar Systems: Determination of Conformational Preference for Dendrimers and Molecular Baskets |
| title_full_unstemmed |
Application of High-Level Computational Methods to Supramolecluar Systems: Determination of Conformational Preference for Dendrimers and Molecular Baskets |
| title_sort |
application of high-level computational methods to supramolecluar systems: determination of conformational preference for dendrimers and molecular baskets |
| publisher |
The Ohio State University / OhioLINK |
| publishDate |
2012 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=osu1338259027 |
| work_keys_str_mv |
AT turnerdanielandrew applicationofhighlevelcomputationalmethodstosupramolecluarsystemsdeterminationofconformationalpreferencefordendrimersandmolecularbaskets |
| _version_ |
1719430675814154240 |