The synthesis, optical properties, spin-polarization path and magnetic ground-state studies of a novel nitronyl nitroxide biradical system based on the 2,6-bis(pyrazolylmethyl)pyridine unit is reported. Besides the presence of σ conjugation and a non-alternant pathway for spin polarization through the core as a coupling unit, the through-bond ferromagnetic interaction between spin carriers, although weak (0.06 cm–1 < ΔEST = 2J/kB < 0.6 cm–1), is preserved. It vanishes (2J/kB ≈ 0) upon coordination with Zn2+ metal ions, but is restored upon Zn2+ depletion with EDTA. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)