[2.2]Paracyclophanes with Defined Substitution Pattern—Key Compounds for the Mechanistic Understanding of the Gilch Reaction to Poly(p‐phenylene vinylene)s

Abstract

12] In line with this observation it was recently reported that a (thiophenolato)cobalt(iii) and its (phenolato)cobalt(iii) analogue are oxidized at 0.55 and 0.36 V versus Fc þ /Fc, respectively to generate the coordinated thinyl and phenoxy radicals. S. We rationalize this behavior by a fast dimerization at ambient temperature of the radical 3 a with SÀS bond formation; however, 3 a is stable in frozen solution at < 77 K.[15] The EPR spectrum of the 2,4,6-tris(tert-butyl)phenylthiyl radical is similar; it also lacks observable hyperfine splitting

The Gilch Synthesis of Poly(p‐phenylene vinylenes): Mechanistic Knowledge in the Service of Advanced Materials

“…In order to achieve a maximum of significance, the set of experimental parameters selected for our investigations [62][63][64][65][66][67][68] was quite similar to those used in the majority of mechanistic studies on the Gilch reaction published in the literature.…”

“…Therefore, we started a research program dedicated explicitly to the elucidation of all open mechanistic facets of the Gilch synthesis and their implications on i) the control of molar masses, ii) the prevention of gel formation during polymer synthesis, and iii) the minimization of critical defects and chain termini in the resulting PPVs. [62][63][64][65][66][67][68] The first step in this program was the careful review and evaluation of all available mechanistic information not only for the Gilch reaction but also for all 'Gilch-related' PPV syntheses. a Guided by this groundwork, a step-by-step analysis was carried out of the intermediates, products, and side-products, and how the involved reactions proceed when syntheses are carried out either under the standard conditions or affected by specific modifications and additives.…”

Teaching Organic Electronics: The Synthesis of the Conjugated Polymer MEH-PPV in a Hands-on Experiment for Undergraduate Students

“…The radical reaction starting dimer 5 is generated by spontaneous dimerization of two p-quinodimethane 4 molecules. The dimerization only takes place in the shown constitution: the two aromatic units are bridged by an ethyl unit and the radicals are, due to radical stabilizing effects, located at the bromine bearing carbon atoms [24]. Subsequently the polymer grows toward the prepolymer 6 by adding p-quinodimethane 4 molecules at both chain ends.…”

Facile Synthesis of Well-Defined MDMO-PPV Containing (Tri)Block—Copolymers via Controlled Radical Polymerization and CuAAC Conjugation

“…The general polymerization mechanism proceeds via a self-initiating p-quinodimethane moiety, which is formed upon the 1,6-base elimination of a premonomer that then spontaneously polymerizes to form a precursor polymer [16,22,23]. Consequently, high conversions are easily reached within seconds to a few minutes enabling very fast polymerizations [24][25][26][27]. In a second step, elimination of the side group takes place, resulting in the desired conjugated polymer [15,23].…”

“…Controlling radical PPV polymerizations is not as straightforward as in standard vinyl radical polymerizations because of the in situ formation of the p-quinodimethane system and its enormous driving force to propagate, which hinders interaction in any control equilibrium of a reversible deactivation radical polymerization (RDRP) [24][25][26][27]. During propagation (associated with the kinetic rate coefficient for propagation, kp), aromaticity of the monomer is restored (see Scheme 1), resulting inevitably in a competition between the propagating radicals and the control agent.…”