Two Blatter Radicals\nFace-to-Face: A Constrained Diradical\nArchitecture

Cofacial arrangement of two Blatter\nradicals enforced\nby the <i>peri</i>-naphthalene scaffold represents a new\napproach to stable\ndiradicals with strong through-space interactions. Two stereoisomers\nof the naphthalene-diradicals, <i>anti</i> and <i>syn</i>, are investigated by XRD, VT-EPR, UV–vis, electrochemical,\nkinetic, and DFT methods. In solutions, both stereoisomers exist as\nopen-shell singlets with Δ<i>E</i><sub>S‑T</sub> = −3.1 and −3.8 kcal mol<sup>–1</sup>, respectively.\nThe <i>anti</i> isomer was resolved into enantiomers and\nconverts to <i>syn</i> with Δ<i>G</i><sup>‡</sup><sub>298</sub> = 23.6(8) kcal mol<sup>–1</sup>.