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New Multiresponsive Chromic Soft Materials: Dynamic Interconversion of Short 2,7‐Dicyanomethylenecarbazole‐Based Biradicaloid and the Corresponding Cyclophane Tetramer
Author(s) -
Wang Deliang,
Capel Ferrón Cristina,
Li Jie,
GámezValenzuela Sergio,
Ponce Ortiz Rocio,
López Navarrete Juan T.,
Hernández Jolín Víctor,
Yang Xiaodi,
Peña Álvarez Miriam,
García Baonza Valentín,
Hartl František,
Ruiz Delgado M. Carmen,
Li Hongxiang
Publication year - 2017
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.201702659
Subject(s) - tetramer , chemistry , molecule , dimer , covalent bond , carbazole , monomer , conjugated system , crystallography , photochemistry , organic chemistry , polymer , enzyme
This work reports on a quinodimethane‐type molecule, 2,7‐dicyanomethylene‐9‐(2‐ethylhexyl)carbazole ( 1 ), one of the shortest π‐conjugated biradicaloids reported to be stable in solution under ambient conditions. This carbazole‐based quinoidal precursor is able to form a macrocyclic σ‐bonded tetramer ( 2 ). The resolved single‐crystal X‐ray structure of tetramer 2 shows that four molecules of 1 are linked together through four long (CN) 2 C−C(CN) 2 bonds (1.631 Å) resulting from coupling of the unpaired electrons in biradicaloid 1 . Dynamic interconversion between monomer 1 and cyclophane tetramer 2 is achieved by reversible cleavage and recovery of the four (CN) 2 C−C(CN) 2 bonds upon soft external stimuli (light absorption, temperature and pressure), which is accompanied by significant color changes. These novel photo‐, thermo‐, and mechanochromic properties expand the versatility of π‐conjugated biradicaloid compounds as novel functional materials that, in combination with spin chemistry and dynamic covalent chemistry, can be relevant in molecular machines, sensors, and switches.