Synthesis and Identification of a Trimethylenemethane Derivative π-Extended with Three Pyridinyl Radicals

A trimethylenemethane (TMM) derivative 12•, in which the parent TMM is π-extended by the symmetric insertion of three pyridine rings into the C−C bonds of TMM, has been synthesized by the alkali metal reduction of the isolated corresponding dication. Although the frozen-glass X-band cw-ESR spectrum of 12• gave unresolved fine structures due to the small ZFS parameters, pulsed ESR two-dimensional electron spin transient nutation (2D-ESTN) spectroscopy unambiguously can afford to identify diradical 12• as a triplet species.