title: Matrix isolation ESR spectroscopy and magnetic anisotropy of D3h symmetric septet trinitrenes.
abstract: The fine-structure (FS) parameters D of a series of D3h symmetric septet trinitrenes were analyzed theoretically using density functional theory (DFT) calculations and compared with the experimental D values derived from ESR spectra. ESR studies show that D3h symmetric septet 1,3,5-trichloro-2,4,6-trinitrenobenzene with D = -0.0957 cm(-1) and E = 0 cm(-1) is the major paramagnetic product of the photolysis of 1,3,5-triazido-2,4,6-trichlorobenzene in solid argon matrices at 15 K. Trinitrenes of this type display in the powder X-band ESR spectra intense Z1-transition at very low magnetic fields, the position of which allows one to precisely calculate the parameter D of such molecules. Thus, our revision of the FS parameters of well-known 1,3,5-tricyano-2,4,6-trinitrenobenzene [E. Wasserman, K. Schueller, and W. A. Yager, Chem. Phys. Lett. 2, 259 (1968)] shows that this trinitrene has [line]D[line] = 0.092 cm(-1) and E = 0 cm(-1). DFT calculations reveal that, unlike C2v symmetric septet trinitrenes, D3h symmetric trinitrenes have the same orientations of the spin-spin coupling tensor D[^]SS and the spin-orbit coupling tensor D[^]SOC and, as a result, have negative signs for both the DSS and DSOC values. The negative magnetic anisotropy of septet 2,4,6-trinitrenobenzenes is considerably strengthened on introduction of heavy atoms in the molecules, owing to an increase in contributions of various excitation states to the DSOC term.
authors.affiliation: Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region 142432, Russian Federation. misochko@icp.ac.ru
authors.forename: Eugenii Ya
authors.initials: EY
authors.lastname: Misochko
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Akimov
authors.forename: Artem A
authors.initials: AA
authors.lastname: Masitov
authors.forename: Denis V
authors.initials: DV
authors.lastname: Korchagin
authors.forename: Sergei M
authors.initials: SM
authors.lastname: Aldoshin
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Chapyshev