Dinitreno pentaradicals: organic sextet molecules

Abstract

A new sextet ground state molecule, the 2,4,6‐trichloro‐1,3‐dinitrenophenoxyl radical, was obtained upon UV photolysis of the corresponding diazido precursor in argon at 5 K. The sextet molecule is formed stepwise with the triplet nitrene, the quartet nitreno radical, and the quintet dinitrene as intermediates that were detected by EPR spectroscopy. IR and UV–Vis measurements only allowed us to observe the main product, the quintet dinitrene. The coupling between the two nitrene centers and the oxygen centered radical in the sextet state results in zero‐field splitting (zfs) parameters of |D/hc| = 0.088 cm−1 and |E/hc| = 0.009 cm−1, considerably larger than in previously reported organic sextet molecules. An analogous sextet dinitrene formed by replacing the oxygen centered radical by a carbon centered radical was also studied by EPR spectroscopy, and in this case the zfs parameters |D/hc| = 0.125 cm−1 and |E/hc| = 0.023 cm−1 indicate even larger spin localization. Copyright © 2016 John Wiley & Sons, Ltd.

Switching the Spin State of Pentafluorophenylnitrene: Isolation of a Singlet Arylnitrene Complex

“…Aryl nitrenes are key intermediates in a large number of reactions that have found applications in photoaffinity labeling − and photolithography and as building blocks for organic magnetic materials. − The photochemical and thermal decomposition of arylazides as suitable precursors of arylnitrenes has therefore been extensively studied (Scheme ). ,− The chemistry of arylnitrenes is complex, since, although these nitrenes show robust triplet ground states, they are born as highly reactive, long-lived open-shell singlets from their precursors.…”

Molecular Magnets: The Synthesis and Characterization of High‐Spin Nitrenes

“…Photolysis of matrix‐isolated precursors 35 a and b at 5 K with 365 nm light results in the formation of quintet dinitrenes 36 a and b, as shown by EPR, IR, and UV/Vis spectroscopy [37] . Subsequent irradiation with 254 nm light produces sextet dinitreno radicals 37 a and b , according to EPR observations.…”

“…Photolysis of matrix-isolated precursors 35 a and b at 5K with 365 nm light results in the formationo fq uintet dinitrenes 36 a and b, as shown by EPR, IR, and UV/Vis spectroscopy. [37] Subsequenti rradiation with 254 nm light produces sextetd initreno radicals 37 a and b,a ccording to EPR observations.T he sextet 37 a exhibits the ZFS parameters of j D j = 0.125 cm À1 and j E j = 0.023 cm À1 ,w hereas for sextet 37 b, j D j = 0.088 cm À1 and j E j = 0.009 cm À1 wered etermined. These new sextet organic speciese xhibit D values about one order of magnitude larger than previously reported sextet organic pentaradicals, where the spin density was more delocalized into the aromatic system.…”

Persistent Organic High‐Spin Trinitrenes

“…[24] Dinitrenes show characteristic absorptions around 450-500 nm. [25] From the absence of such absorptions in the spectra we conclude that dinitrene 14 a is not formed in detectable quantities, in accordance with the results from the IR experiments in Ar matrices.…”