Geometrically-Controlled and Site-Specifically-Functionalized Phenylacetylene Macrocycles

Jinshan Zhang, Douglas J. Pesak, James L. Ludwick, Jeffrey S. Moore

Research output: Contribution to journalArticlepeer-review

Abstract

A convergent, stepwise synthesis of linear phenylacetylene sequences (PASs) is described. The methodology allows for complete control over chain length, sequence order of monomers, and functional group placement. Chain growth follows geometric progression thus allowing sequences of length 2n, where n is the number of repetitive cycles, to be assembled in a total of just 3·n steps (two deprotections and one coupling for each cycle). Sequences of length other than 2n as well as sequences having a particular arrangement of co-monomer units, can also be realized by merging parallel repetitive cycles. Upon deprotection of the termini, these PASs can be cyclized to phenylacetylene macrocycles (PAMs) in high yield. Control over the ring structure of PAMs is determined by the chemistry of precursor PASs; the size of the macrocycle is related to the sequence length, while the geometry of the macrocycle and the position of the pendant functional groups on the macrocycle is governed by co-monomer sequence order. PAMs with four, five, six, seven, and twelve phenylacetylene monomer units, as well as a variety of site-specifically-functionalized PAMs, have been synthesized with this method. Finally, functional group transformations have been performed on some of the PAMs which lead to PAMs with new functionality. The versatile and efficient approach to this family of geometrically well-defined macrocycles offers potential for producing a set of modular building blocks to rationally assemble molecular crystals and liquid crystals. For this reason, the solid-state characteristics of the hydrocarbon skeletons are of interest. In spite of their solubility in common solvents, hydrocarbon PAMs are shown to yield crystals with remarkable thermal stability and high melting points. Three PAM hydrocarbons are shown not to exhibit melting transitions up to ca 400 °C, at which point an abrupt thermal irreversible reaction occurs, apparently involving a solid-state polymerization of the acetylene units.

Original languageEnglish (US)
Pages (from-to)4227-4239
Number of pages13
JournalJournal of the American Chemical Society
Volume116
Issue number10
DOIs
StatePublished - May 1 1994

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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