2,6-Bis(pyrazolyl)pyridine Functionalised with Two Nitronylnitroxide and Iminonitroxide Radicals (original) (raw)

A Multifunctional High-Spin Biradical Pyrazolylbipyridine-bisnitronylnitroxide

Organic Letters, 2004

Synthesis and UV−vis, IR, and EPR spectroscopic characterizations, together with X-ray structural analysis, of functional nitronyl-and iminonitroxides attached to pyrazolylbipyridine are described. The exchange interactions between the nitronylnitroxides are found to be stronger than for the iminonitroxides. Although the substitution of a pyridine with the pyrazole ring leads to shorter distances and larger dipolar couplings, the exchange interaction is diminished. While compound 1 forms dimers in the solid state, the terpyridine 3 leads to supramolecular π-stacking. Page S5: Synthetic procedures (Scheme 1 and Scheme 2) towards biradical 1(NN) and 2 (IN) and the monoradical standards 20 (NN) and 21 (IN).

Organic radicals, a promising route towards original molecule-based magnetic materials

Coordination Chemistry Reviews, 2009

We describe our activities on radical-based compounds developed within the 6-year priority program of the DFG Schwerpunktprogramm "Molekularer Magnetismus". During this period, two families of radicals, based on nitroxide and verdazyl unpaired electron containing moieties, were used to build up purely organic compounds as well as coordination compounds. The versatility of their chemistry together with the variety and strength of the intra-and inter-molecular exchange interactions emphasised by calculation on model systems confirm the role of radicals as major building blocks for molecule-based magnetic materials.

Synthesis of Multitopic Verdazyl Radical Ligands. Paramagnetic Supramolecular Synthons

Organic Letters, 2004

The syntheses of several verdazyl radical and diradicals containing pyridine-based multitopic coordination sites are described. These compounds were designed to be paramagnetic analogues of oligopyridine metallosupramolecular building blocks. Verdazyls 1 are one of the few families of organic radicals stable enough to be prepared, handled, and isolated using conventional techniques. 1 In recent years, derivatives of 1 have attracted interest as open-shell ligands in coordination chemistry, as alternatives to the established complex chemistry of nitroxide radicals 2 and semiquinone radical anions. 3 The chelating capabilities of multidentate verdazyls such as 2, 4 3, 5 and 4 6 (among others 7) render them excellent ligands for transition metals, and the magnetic interactions between verdazyl-and metal-based spins can be exceptionally strong and ferromagnetic. 4a,5a As such, verdazyl radicals are outstanding candidates for the construction of metal-radicalbased molecular magnetic materials. The chelating environments offered by verdazyls 2-4 are structurally analogous to those found in 2,2′-bipyridine, 2,2′: 6′,2"-terpyridine, and 2,2′-bipyrimidine, respectively. The parent oligopyridines are, of course, part of one of the benchmark families of ligands in coordination chemistry. Nitrogen-containing aromatics have also been tremendously important in the burgeoning field of supramolecular coor-(1) (a) Neugebauer, F. A.