Issue 71, 2024

Chemical reduction of π-expanded functionalized pentacene: cooperation of side group in alkali metal binding

Abstract

Chemical reduction of a vertically expanded pentacene, TIPS-peri-pentacenopentacene (TIPS-PPP), with sodium metal in THF readily afforded a doubly-reduced product isolated as [{Na+(THF)3}2(TIPS-PPP2−)]. Single-crystal X-ray diffraction revealed the formation of a π-complex of TIPS-PPP2− with two {Na+(THF)3} moieties. The sodium ion is coordinated to three C-atoms at the most negatively charged edge sites and at the lateral ethynyl group. The delocalisation of the charge on the ethynyl function is accompanied by its notable elongation (Δ = 0.015 Å) coupled with the contraction of the adjacent single C–C bond (Δ = 0.033 Å). Bond length analysis supported by Harmonic Aromaticity Oscillator Model (HOMA) shows that the dianion can be written with four aromatic sextets in agreement with the Clar representation. Although TIPS-PPP2− has 36 π-electrons (4n), it does not show a global magnetic paratropic response. The rings with the most negative charge density have a very low paratropic response, while the other rings have a low diatropic response. Overall, the dianion is a non-aromatic molecule.

Graphical abstract: Chemical reduction of π-expanded functionalized pentacene: cooperation of side group in alkali metal binding

Supplementary files

Article information

Article type
Communication
Submitted
03 Jul 2024
Accepted
07 Aug 2024
First published
14 Aug 2024

Chem. Commun., 2024,60, 9526-9529

Chemical reduction of π-expanded functionalized pentacene: cooperation of side group in alkali metal binding

M. Pennachio, Z. Wei, M. Mamada, M. Frigoli and M. A. Petrukhina, Chem. Commun., 2024, 60, 9526 DOI: 10.1039/D4CC03318C

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