Details

Autor(en) / Beteiligte

• Ramsaywack, Sharwatie

Titel

Synthesis and Properties of Donor/Acceptor Substituted Expanded Radialenes

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2009

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Cross-conjugated macrocycles are appealing to organic chemists not only because of their aesthetically pleasing structures, but also because the synthetic challenge that they offer is alluring. The Tykwinski group has contributed significantly to the synthesis and study of iso-polydiacetylenes (iso-PDAs) and expanded radialenes ([ n]ERs), both of which have two-dimensionally ( 2D) conjugated frameworks. These studies have shown that the iso-PDAs and [n]ERs can be tailored to achieve desirable properties. It has been a longstanding goal in the Tykwinski group to exploit the 20 conjugated framework of the [n]ERs to gain access to novel push-pull chromophores. The work described in this Thesis encompasses two central themes: (1) the modular syntheses of donor-acceptor substituted two-dimensionally (20) conjugated molecules, and (2) the investigation of their structure-property relationships. To this end, a series of iso-PDAs and [4]ERs were prepared and studied using differential scanning calorimetry, cyclic voltammetry, 13C NMR, UV-Vis, and fluorescence spectroscopies. A one-pot Sonogashira cross-coupling reaction of vinyl triflates and terminal ene-diynes afforded iso-PDAs bearing a wide range of functionalites, including trialkylsilyl protecting groups, propargyl alcohols, and electron-donating groups. A complementary approach, which relied on the use of orthogonal alkyne-protecting groups, was developed for the incorporation of electron-withdrawing functionalities. Precursor [4]ERs were synthesized via a generalized protocol involving a sequence of deprotection and Sonogashira cross-coupling reactions between iso-PDAs and dibromoolefins. Further functionalization of the [4]ER framework with donors/acceptors was achieved via deprotection and subsequent two-fold Sonogashira cross-coupling reactions between the terminal alkynes and various aryl iodides. The electronic properties of the iso-PDAs and [4]ERs were contingent upon the nature of the appended groups. However, the electronic properties of the [4]ERs did not mirror those of the corresponding iso-PDAs. X-Ray crystallography for one [4]ER derivative revealed that the radialene framework is not particularly strained, and in the solid state, it maintains a planar structure conducive to effective pi-overlap within the conjugated framework, comparable to other [4]ERs known to the Tykwinski group.