| Autor: |
Steffenfauseweh, Henric, Rottschäfer, Dennis, Vishnevskiy, Yury V., Neumann, Beate, Stammler, Hans‐Georg, de Bruin, Bas, Ghadwal, Rajendra S. |
| Předmět: |
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| Zdroj: |
Chemistry - A European Journal; 12/2/2024, Vol. 30 Issue 67, p1-7, 7p |
| Abstrakt: |
Diradicals based on a meta‐quinodimethane (m‐QDM) scaffold generally have a triplet ground state and are rather scarce. Herein, m‐QDM‐based non‐Kekulé diradicals [3,3′‐(NHC)2BP] (3‐NHC) (NHC = SIPr = C{N(Dipp)CH2}2; IPr = C{N(Dipp)CH}2, Me‐IPr = C{N(Dipp)CMe}2; Dipp = 2,6‐iPr2C6H3; BP = 1,1′‐C6H4C6H4) featuring N‐heterocyclic carbene (NHC) pendants are reported as crystalline solids. The EPR spectra of 3‐NHC show both allowed (Δms = 1) and forbidden (Δms = 2; 'half‐field') transitions characteristic for triplet diradicals. Variable temperature EPR studies however reveal a singlet ground state for 3‐SIPr. Consistent with the EPR spectra, calculations predict a remarkably small singlet‐triplet energy gap (ΔEST ≤ 0.26 kcal/mol) for the 3‐NHC compounds. The calculated singlet diradical character for the ground states of the 3‐NHC compounds amounts to ~99 %. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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