Premium
Dynamic Covalent Properties of a Novel Indolo[3,2‐ b ]carbazole Diradical
Author(s) -
BadíaDomínguez Irene,
PeñaÁlvarez Miriam,
Wang Deliang,
Pérez Guardiola Andrés,
Vida Yolanda,
Rodríguez González Sandra,
López Navarrete Juan T.,
Hernández Jolín Víctor,
Sancho García Juan C.,
García Baonza Valentín,
Nash Rosie,
Hartl František,
Li Hongxiang,
Ruiz Delgado M. Carmen
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202005211
Subject(s) - diradical , chemistry , carbazole , monomer , photochemistry , electron paramagnetic resonance , organic chemistry , excited state , nuclear magnetic resonance , polymer , physics , nuclear physics , singlet state
Abstract This work describes the synthesis and properties of a dicyanomethylene‐substituted indolo[3,2‐ b ]carbazole diradical ICz‐CN. This quinoidal system dimerises almost completely to (ICz‐CN) 2 , which contains two long C(sp 3 )−C(sp 3 ) σ‐bonds between the dicyanomethylene units. The minor open‐shell ICz‐CN component in the solid‐state mixture was identified by EPR spectroscopy. Cyclic voltammetry and UV–visible spectroelectrochemical data, as well as comparison with reference monomer ICz‐Br reveal that the nature of the one‐electron oxidation of (ICz‐CN) 2 at ambient temperature and ICz‐CN at elevated temperature is very similar in all these compounds due to the prevailing localization of their HOMO on the ICz backbone. The peculiar cathodic behaviour reflects the co‐existence of (ICz‐CN) 2 and ICz‐CN. The involvement of the dicyanomethylene groups stabilizes the close‐lying LUMO and LUMO+1 of (ICz‐CN) 2 and especially ICz‐CN compared to ICz‐Br, resulting in a distinctive cathodic response at low overpotentials. Differently from neutral ICz‐CN, its radical anion and dianion are remarkably stable under ambient conditions. The UV/Vis(–NIR) electronic transitions in parent (ICz‐CN) 2 and ICz‐CN and their different redox forms have been assigned convincingly with the aid of TD‐DFT calculations. The σ‐bond in neutral (ICz‐CN) 2 is cleaved in solution and in the solid‐state upon soft external stimuli (temperature, pressure), showing a strong chromism from light yellow to blue–green. Notably, in the solid state, the monomeric diradical species is predominantly formed under high hydrostatic pressure (>1 GPa).