Acenaphthylene‐Fused Cyclo[8]pyrroles with Intense Near‐IR‐Region Absorption Bands

Abstract

An acenaphthylene-fused cyclo[8]pyrrole was synthesized by using an oxidative coupling reaction of the corresponding 2,2'-bipyrrole. Two conformational isomers 1 a and 1 b were isolated, and their molecular structures were elucidated by X-ray crystallographic studies. The less-polar and lower-symmetry 1 b isomer can be converted into the 1 a isomer through a thermal ring flip. Application of the perimeter model developed by Michl to magnetic circular dichroism spectroscopic data and theoretical calculations demonstrate that there is a marked redshift of the near-IR absorption maxima relative to cyclo[8]isoindole because there is a significant stabilization of the LUMO due to the differing effects of a fused ring expansion with acenaphthylene and benzene moieties on the frontier π molecular orbitals.

Bandgap Engineering in π-Extended Pyrroles. A Modular Approach to Electron-Deficient Chromophores with Multi-Redox Activity

“…It was found that, starting from compound 2, the HLG could be progressively reduced by structural elaboration of the acceptor end of the fused pyrrole. Switching off the acceptor functionality by reduction of the amide groups was also considered (compound 1), and was indeed predicted to result in a broadened HLG (3.81 eV), comparable with those calculated for reported electron-rich systems, the unsubstituted acenaphthopyrrole 49−53 and its 2,5-di-tert-butyl derivative 54 (3.89 and 3.97 eV, respectively, at the same level of theory). In 2, the KS bandgap (3.70 eV) is comparable with that predicted for 3,4-dichloroacenaphthopyrrole 53,55 (3.64 eV).…”

Cyclo[9]pyrrole: Selective Synthesis of [34]Nonaphyrin(0.0.0.0.0.0.0.0.0)

“…Dibromopyrrole 1 was prepared via protection of the NH moiety of acenaphtho­[1,2- c ]­pyrrole by treatment with n -BuLi and ethyl chloroformate, followed by bromination with NBS. Pyrrole 2 was prepared via the Miyaura–Ishiyama borylation of iodopyrrole in 63% yield. Terpyrrole 3 was obtained via the Suzuki–Miyaura cross-coupling of 1 with 2 .…”

Benzene-fused bis(acenaphthoBODIPY)s, stable near-infrared-selective dyes

“…In order to increase the solubility of the target acenaphtho derivatives in common organic solvents, two tert -butyl groups were introduced into acenaphthylene, and the resulting compound was converted to ethylacenaphtho[1,2- c ]pyrrole-1-carboxylate 2. 18 Formylation of 2 with the Vilsmeier reagent gave α-formylated compound 3a in 98% yield ( Scheme 1 ). The formyl group of 3a was converted to an acetoxymethyl group by reduction with NaBH 4 followed by acetylation with Ac 2 O and 4-dimethylaminopyridine (DMAP).…”

“…POCl 3 (1.9 mL, 23.6 mmol) was added to dry DMF (2.2 mL, 24.5 mmol) at 0 °C under an argon atmosphere, and the mixture was stirred at rt for 30 min. After acenaphthopyrrole 2 ( ref. 18 ) (6.22 g, 16.6 mmol) in dry CH 2 Cl 2 (115 mL) was added at rt, the mixture was stirred for 90 min.…”

“… 16 We have also reported the effective elongation of absorption maxima in the case of BODIPYs 17 and cyclo[ n ]pyrroles. 18 This acenaphtho-fusion method was successfully applied to the preparation of bisBODIPYs with stable NIR chromophores.…”