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Design and Synthesis of Shape-persistent Terpyridine-based Matallomacromolecules and Architectures
- Publication Year :
- 2012
-
Abstract
- Self-assembly has grown into an important facet in the realm of supramolecular chemistry. Since its onset, the ability to construct intricate ensembles has become an area of intense research. Utilizing the tpy-MII-tpy (tpy = 2,2′;6′,2″-terpyridine) coordinative interaction, many metallomacrocycles have been synthesized and isolated via both stepwise and self-assembled processes. The study of constitutional isomers in supramolecular chemistry has been limited, due to the scarcity of explored systems for study. However, from different benzene-cored tetrakisterpyridine ligands (1,2,3,4 vs. 1,2,4,5), two sets of novel isomers have been self-assembled with either CdII or ZnII, and their different drift times were ascertained using electrospray ionization mass spectrometry coupled with travelling wave ion mobility (ESI-TWIM-MS). Another set of isomeric metallomacrocycles were also synthesized from 60°- and 120°-oriented bisterpyridine ligands. Molecular modeling and ESI-TWIM-MS on these constitutional isomers suggest extensive differences between the two systems. By restricting the ability for self-assembly of geometrically-optimal ring systems, such as a triangle from a 60°-oriented ligand, has led to the isolation of a series of folded supramolecular tetramers or "Dondorff" rings. The photochemistry of these systems reveals lifetimes on the 1-2 ns timeframe, as well as typical UV-vis and photoluminescence (PL) spectra. By applying gradient mass spectrometry (gMS2), it was deduced that the order of bonding strength in the tetramers was CdII < ZnII < FeII < RuII. Near quantitative self-assembly of molecular triangles was achieved by the stoichiometric mixing of various substituted 60°-oriented bisterpyridine ligands with either CdII or ZnII. These triangles were characterized with 1H and 13C NMR, UV-vis, and PL spectroscopies, as well as ESI-TWIM-MS. The triangles were further assembled into nanofibers by layering with the hexavalent anion - sodium benzenehexacarboxylate. These fibers were analyzed with transmission electron microscopy (TEM) as well as selected area electron diffraction (SAXD), which revealed spacing values that correlated well with molecular modeling. Use of a Moore-type dendron, as a molecular antenna, led to the synthesis of a new family of 120°-oriented bisterpyridine ligands. Self-assembly of the ligands with CdII resulted in formation of supramolecular hexamers in high yields. The hexamers, characterized by ESI-TWIM-MS, as well as 1H and 13C NMR spectroscopies, were also studied for quantum yield values, which increased as a function of the increasing dendron generation attached to the metallomacrocycles.
- Subjects :
- Organic Chemistry
Terpyridine
Supramolecular Chemistry
Subjects
Details
- Language :
- English
- Database :
- OpenDissertations
- Publication Type :
- Dissertation/ Thesis
- Accession number :
- ddu.oai.etd.ohiolink.edu.akron1354651187