Conjugated dendrimers have been studied for their use in preparing photoreactive materials and for their light harvesting properties.  One of the main goals of the Mississippi College Organic Research Group (MC-ORG) is 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 and therefore loss of conjugation and reduced light harvesting properties.  The MC-ORG has been synthesizing “flat” dendrimers that cannot lose this conjugation due to the ethynyl units being locked in place by ether connections.  These ether connections are made during an intermediate step when a monomacrocyclic dendrimer is formed.  The MC-ORG has successfully created a monomacrocyclic dendrimer with a three carbon ether connection.  The goal of this research is to determine whether a one, two, or four carbon connection would also form this ether connection without twisting of the ethynyl units.  This ether connection is in the position meta to the ethynyl groups.  Another goal will be to determine if one, two, three, and/or four carbon connections can be placed ortho to the ethynyl groups.  It will also be determined if amine bridges would also lock the ethynyl bridges in place and form flat dendrimers.  This amine connection is studied with different carbon lengths in the bridge and also 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 in order to determine if these various ether and amine connections will improve conjugation within the structure.  We gratefully acknowledge support from the NSF (EPS-0903787) and from the Mississippi College Catalysts, the alumni support group of the Department of Chemistry & Biochemistry.

How do ether and amine bridges affect the conjugation in monomacrocyclic dendrimers?

253rd National Meeting (2017)

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