Synthesis and electronic properties of bridged [8]-, [12]- and [16]-cyclo-para-phenylenes

Fabien Lucas (1) , Joëlle Rault-Berthelot (1) , Cassandre Quinton (1) , Cyril Poriel (1)

1 ISCR - Institut des Sciences Chimiques de Rennes

Hoop-shaped pi-conjugated macrocycles constitute a new family of pi-conjugated systems displaying unique properties induced by their radially directed pi-orbitals. The electronic properties of these nanohoops are deeply dependent on their budding units and their size. We report herein the first size dependence study of [8]-, [12]- and [16] cyclo-para-phenylenes bridged by nitrogen atoms. The properties were elucidated by H-1 NMR, cyclic voltammetry, UV-vis absorption and fluorescence spectroscopy (in solution and in thin film). Thus, this work reports one of the largest bridged nanohoops synthesized, namely [4]cyclo-para-9-ethylhexyl-2,7-diphenyl-carbazole [16]CPP4N, an analog of [16]CPP, which displays an alternation of four unbridged biphenylenes and four nitrogen bridged biphenylenes. Removing either all the unbridged phenylenes ([4]cyclo-para-9-ethylhexyl-carbazole [8]CPP4N, an analog of [8]CPP) or one budding unit ([3]cyclo-para-9-ethylhexyl-2,7-diphenyl-carbazole [12]CPP3N, an analog of [12]CPP) allows decreasing the size of the nanohoop with nevertheless drastically different consequences on the properties. This is what we aim at reporting in this work.

Domaines: Chimie

Fabien Lucas, Joëlle Rault-Berthelot, Cassandre Quinton, Cyril Poriel. Synthesis and electronic properties of bridged [8]-, [12]- and [16]-cyclo-para-phenylenes. Journal of Materials Chemistry C, 2022, 10, pp.14000-14009. ⟨10.1039/d2tc00881e⟩. ⟨hal-03798111⟩