The Ground State\nof Multispin Systems Based on Verdazyl\nand Nitrene Radicals: An EPR and Quantum-Chemical Study

In this study, low-temperature EPR spectroscopy and quantum-chemical\ntechniques were employed to investigate multispin systems1,5-diphenyl-3-(3-nitrenophenyl)-6-oxoverdazyl\nand 1,5-diphenyl-3-(4-nitrenophenyl)-6-oxoverdazylthat contain\na nitrene center at either a <i>meta</i>- or <i>para</i>-position, respectively. Ground states and magnetic zero-field splitting\n(ZFS) parameters of these multispin systems were determined by experimental\nand computational methods. The results indicated that the high-spin\nquartet state is a ground state, and the quartet–doublet energy\ngap is close to 10 kcal/mol for the <i>para</i>-position\nof the nitrene group, with ZFS parameters <i>D</i> = 0.292\ncm<sup>–1</sup> and <i>E</i>/<i>D</i> =\n0.002 cm<sup>–1</sup>. In contrast, for the <i>meta</i>-position, the low-spin doublet state is favored with an energy gap\nof 1 kcal/mol. The observed difference in the ground states could\nbe qualitatively explained by an analysis of the spin density distribution\nand by delocalization of the unpaired π-electron of the nitrene\ncenter. Overall, this study provides valuable insights into the electronic\nstructures and magnetic parameters of such multispin systems.