3,4,5,6‐Tetrafluorophenylnitren‐2‐yl: A Ground‐State Quartet Triradical

Abstract

The photochemistry of 2-iodo-3,4,5,6-tetrafluorophenyl azide (7 d) has been investigated in argon and neon matrices at 4 K, and the products characterized by IR and EPR spectroscopy. The primary photochemical step is loss of a nitrogen molecule and formation of phenyl nitrene 1 d. Further irradiation with UV or visible light results in mixtures of 1 d with azirine 5 d', ketenimine 6 d', nitreno radical 2 d, and azirinyl radical 9. The relative amounts of these products strongly depend on the matrix and on the irradiation conditions. Nitreno radical 2 d with a quartet ground state was characterized by EPR spectroscopy. Electronic structure calculations in combination with the experimental results allow for a detailed understanding of the properties of this unusual new type of organic high-spin molecules.

Photochemistry of Furyl- and Thienyldiazomethanes: Spectroscopic Characterization of Triplet 3-Thienylcarbene

“…Neese’s ORCA program shows considerable promise for the analysis of a variety of high-spin organic reactive intermediates. 63–66 Unfortunately, we find that the ORCA calculations for the zero-field splitting parameters of triplet 3-thienylcarbene ( 13 ) are not robust. The computed values of D and E are much too sensitive to the basis set and level of theory.…”

EPR spectroscopic and computational characterization of the 2‐dehydro‐m‐xylylene and 4‐dehydro‐m‐xylylene triradicals

“…Thus, analogous to the dehydrotoluenes, 10 and 12 feature 4 A″ and 4 A 2 quartet ground states, respectively, with similar doublet–quartet splittings ( 10 : 5.3 kcal/mol; 12 : 7.9 kcal/mol; MRMP2/cc‐pVTZ//CASSCF/cc‐pVTZ), whereas the 2 A″ ground state of 11 lies 3.5 kcal/mol below the 4 A″ state . By a careful analysis of the zero‐field splitting (ZFS) parameters of derivatives of 10 and 12 , direct evidence for the contribution of carbenoid resonance structures 10b and 12b (i.e., polarization of the π system with an increase of spin density at the dehydrocarbon) could be obtained, as will be discussed in more detail below …”

“…Triradicals of the σσπ type have been realized as (fluorinated) dehydrophenylnitrenes 10–12 (Chart ) . Phenylnitrene 13 is well known to have a 3 A 2 ground state dominated by the electronic configuration (8b 2 ) 1 (3b 1 ) 1 , whereas the 1 A 2 open‐shell singlet state with the same orbital occupation pattern lies 15–16 kcal/mol higher in energy .…”

Light induced reactions in cryogenic matrices

“…Grote et al 57 investigated the photochemistry of 2-iodo-3,4,5,6-tetrafluorophenyl azide in argon and neon matrices at 4 K, characterizing the products by IR and EPR spectroscopies. The primary photochemical step was found to be the loss of a nitrogen molecule and formation of phenyl nitrene (Fig.…”

“…20 Observed photoproducts resulting from photolysis of matrix isolated 2-iodo-3,4,5,6-tetrafluorophenyl azide. 57 molecules in the solid matrix is made possible. Fig.…”