Breaking the semi-quinoid structure: spin-switching from strongly coupled singlet to polarized triplet state.
2,7-TMPNO (4,5,9,10-tetramethoxypyrene-2,7-bis(tert-butylnitroxide)) was found to exist in semi-quinoid form with unprecedented strong intramolecular magnetic exchange interaction of 2 J/kB = 1185 K operating over a distance of 10 A. Structural transformations with the activation energy of ΔEeq = 949 K were observed by varying the temperature, from more quinoid structure at low temperature to more biradicaloid structure at higher temperature. Moreover, this molecule undergoes a transient spin transition from singlet to polarized triplet state upon photoexcitation revealed by TREPR spectroscopy. The spin Hamiltonian parameters were determined to be S = 1, g = 2.0065, D = -0.0112 cm(-1), and …
CCDC 950752: Experimental Crystal Structure Determination
Related Article: Prince Ravat, Yoshio Teki, Yoshikazu Ito, Elena Gorelik, Martin Baumgarten|2014|Chem.-Eur.J.|20|12041|doi:10.1002/chem.201403338