Highly Strained 1,8-Naphthalene-Bridged Cyclic Oligophenylenes and Their Open-Shell Diradical Dications

Abstract

The synthesis and characterization of two 1,8naphthalene-bridged cyclic oligo-para-phenylenes with four or eight phenylene units are reported. Both molecules exhibit a highly strained structure with two nearly face-to-face arranged p,p′biphenylylene/p,p′-quaterphenylylene chains. Their dications were obtained by chemical oxidation with NO•SbF 6 , and both showed open-shell singlet diradical character with a small singlet−triplet energy gap.

Perylene‐Based Linear Nonalternant Nanoribbons with Bright Emission and Ambipolar Redox Behavior

“…In contrast to proton resonance signals of (NNR-1) 2 + , which could be clearly recorded at room temperature, the resonance signals of (NNR-2) 2 + appeared as the temperature decreased to 193 K (Supporting Information), similar to most typical diradicaloids with broadening NMR signals at room temperature due to a thermally populated triplet state. [28] In addition, the aromatic protons closest to the pentagonal rings of (NNR-1) 2 + and (NNR-2) 2 + were significantly upfield shifted (0.9-1.4 ppm) as compared to those of the respective neutral one (see more in Supporting Information), indicating the antiaromatic pentagons in a dicationic form.…”

Perylene‐Based Linear Nonalternant Nanoribbons with Bright Emission and Ambipolar Redox Behavior

“…These charged species in solution were extremely sensitive to moisture, but stable under inert atmospheres, allowing detailed characterization with proton NMR and UV/Vis‐NIR spectroscopy as well as variable‐temperature electron spin resonance (ESR) measurements. In contrast to proton resonance signals of (NNR‐1) 2+ , which could be clearly recorded at room temperature, the resonance signals of (NNR‐2) 2+ appeared as the temperature decreased to 193 K (Supporting Information), similar to most typical diradicaloids with broadening NMR signals at room temperature due to a thermally populated triplet state [28] . In addition, the aromatic protons closest to the pentagonal rings of (NNR‐1) 2+ and (NNR‐2) 2+ were significantly upfield shifted (0.9–1.4 ppm) as compared to those of the respective neutral one (see more in Supporting Information), indicating the antiaromatic pentagons in a dicationic form.…”

“…In contrast to proton resonance signals of (NNR-1) 2 + , which could be clearly recorded at room temperature, the resonance signals of (NNR-2) 2 + appeared as the temperature decreased to 193 K (Supporting Information), similar to most typical diradicaloids with broadening NMR signals at room temperature due to a thermally populated triplet state. [28] In addition, the aromatic protons closest to the pentagonal rings of (NNR-1) 2 + and (NNR-2) 2 + were significantly upfield shifted (0.9-1.4 ppm) as compared to those of the respective neutral one (see more in Supporting Information), indicating the antiaromatic pentagons in a dicationic form. The electronic absorption spectra of prepared (NNR-1) 2 + and (NNR-2) 2 + salts in DCM are shown in Figure 7a.…”

1,8‐Diarylnaphthalenes: Synthesis, Properties, and Applications

“…In this context, 1,8‐naphthalene‐bridged cyclic oligo( para‐ phenylenes) 127 with different numbers of phenylene units (n=1‐3) were designed and synthesized (Scheme 41). [76] The octyloxy group was attached onto the 2,7‐positions of the naphthalene unit to afford requisite solubility. Both molecules 127 exhibit a highly strained structure with two nearly face‐to‐face arranged p,p′‐ biphenylylene/ p,p′‐ quaterphenylylene chains.…”