Exploiting Substituent Effects for the Synthesis of a Photooxidatively Resistant Heptacene Derivative

Abstract

Substituent effects have been exploited to produce an unusually persistent heptacene derivative. In total, four new heptacene derivatives with varying levels of photooxidative resistance (1 < 2 < 3 < 4) have been synthesized. A combination of p-(t-butyl)thiophenyl substituents at positions 7 and 16 (i.e., arylthio substituents attached to the most reactive ring) and o-dimethylphenyl substituents at positions 5, 9, 14, and 18 (i.e., steric resistance on neighboring rings) make heptacene derivative 4 especially resistant to photooxidation. It persists for weeks as a solid, for 1-2 days in solution if shielded from light, and for several hours in solution when directly exposed to both light and air. Heptacene derivative 4 has been fully characterized. It possesses a small HOMO-LUMO gap of 1.37 eV.

Beyond Pentacenes: Synthesis and Properties of Higher Acenes

“…Two more aryl substituted heptacenes (53 and 54) were prepared and investigated by the Miller group in 2009 (Fig. 26) [58]. Beyond Pentacenes: Synthesis and Properties of Higher Acenes 19 As expected, the 7,16-di(p-tert-butylphenyl)heptacene 53 decomposed rapidly in solution in an ambient atmosphere in the presence of light, while the four additional o,o-dimethylphenyl substituents in 54 enhance the stability somewhat [58].…”

Infrared vibrational and electronic transitions in the dibenzopolyacene family

“…Though the polyacene molecules are reactive, their derivatives seem to be more stable [17][18][19]. Payne et al [17], Chun et al [18], and Kaur et al [19] have reported the synthesis of heptacene derivatives.…”

“…Payne et al [17], Chun et al [18], and Kaur et al [19] have reported the synthesis of heptacene derivatives. Weisman et al [20] have reported a theoretical and spectroscopic study of dibenzopolyacene molecules up to the dibenzo[jk,a1b1]octacene range.…”

Photogeneration of Octacene and Nonacene

“…Recent work has shown that bulky substituents kinetically stabilize the heptacene framework, thus providing interesting compounds for materials applications. [13][14][15] Clars discouraging statement surely refers to experiments under conventional conditions at room temperature. By using cryogenic matrix-isolation techniques, we have defied Clars prediction and herein report the synthesis of octacene (3) and nonacene (4).…”