The Mississippi College Organic Research Group (MC-ORG) has been attempting to design and prepare flat, two-dimensional dendrimers. It has been found that when twisting occurs about the single bonds of the dendrons, there is a decrease in energy transfer which results in a loss of conjugation. This loss of conjugation is undesirable since conjugated dendrimers are of interest due to their use in preparing photoreactive materials and for their light harvesting properties. The MC-ORG has been attempting to synthesize “flat” dendrimers that should retain their conjugation due to the ethynyl units theoretically being locked in place by ether connections. These ether connections are created during an intermediate step when a monomacrocyclic dendrimer is formed. The goal of this research is to determine whether a one, two, three, or four carbon connection would form an ether bridge in positions both ortho and meta to the ethynyl groups without twisting of the ethynyl units. It will also be determined if amine bridges would lock the ethynyl bridges in place and form flat dendrimers. This amine connection is studied with different carbon lengths in the bridge and in the positions both ortho and meta to the ethynyl groups. To investigate these questions, optimum structures are computed at the SCF and DFT levels of theory. The functionals employed are B3LYP, M06-2X, and ωB97XD. All calculations use correlation consistent basis sets. Finally, time-dependent DFT calculations are used to investigate the UV-Vis spectra to determine if these various ether and amine connections will improve conjugation within the structure. The MC-ORG has created a monomacrocyclic dendrimer with a three-carbon ether connection. This monomacrocyclic dendrimer was found, both experimentally and computationally, to show some loss of conjugation. Since the process of creating this three-carbon ether bridge has already been developed, it will be determined if having two ethynyl units will reduce twisting and assist in retaining conjugation. It will also be determined if multiple macrocyclic dendrimers connected together in what is known as a “spider-web” dendrimer will improve conjugation.

Retention of conjugation in monomacrocyclic dendrimers with ether and amine bridges

255th National Meeting (2018)

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