A stable oxoverdazyl free radical: Structural and magnetic characterization

Ferromagnetic intermolecular exchange interaction in ethynyl-verdazyl radical crystals

“…Despite the weak value of J, it remains that the slipped 1D chains obtained in 2 has guaranteed the obtention of the ferromagnetic interactions that were theoretically predicted. The absence of head-over-tail stacking, which has been previously observed and correlated with antiferromagnetic interactions in the case of 1,5-dimethyl-3-IJaryl)-6-oxoverdazyl with aryl = imidazolyl, 12 pyridyl, 2 2-hydroxyphenyl 13 and 4-acetamidophenyl, 19 is striking, although the exact impact of the phenylethynyl substituent on crystal packing remains an open question.…”

Manganese(iii)-mediated cyclodimerization of a hydrazinyl derivative generating an unprecedented 1,2,3,5,6-substituted leuco-verdazyl ring

“…1-4 Such stable radicals, characterized by their unpaired electron, are of fundamental interest and have been extensively investigated for their potentially interesting magnetic properties. [5][6][7][8] Verdazyl radicals (Scheme 1; 3) are commonly obtained by in situ one-electron oxidation of leuco-verdazyl molecules (2), which are synthesized by reaction of a formazan derivative (1) with formaldehyde in the presence of potassium hydrogensulfate (Scheme 1). 9,10 Scheme 1 General synthetic route to 1,3,5-substituted verdazyl radicals.…”

Intermolecular π‐dimer of oxoverdazyl radicals with long‐distance multicenter (2e/8c) bonding via nitrogen atoms

“…These radicals (including 6‐oxoverdazyl derivatives illustrated in Chart ) and their transition metal coordination complexes recently attracted attention as a new building block for the molecule‐based magnets 51. Thus, preparation and solid‐state characterization of verdazyl‐based substances became a focus of many structural reports and materials science publications 52–54. Still, the single example of a intramolecular π ‐dimer reported for these open‐shell species took place in the solid‐state structure of ferrocene‐bridged oxoverdazyl diradical in which π ‐bonding is assisted by the pre‐arrangement of verdazyl fragments in parallel planes separated by ∼3.3 Å 50.…”

“…It should be mentioned that most of the reported structures of verdazyl radicals involved phenyl‐ (or other arene‐) substituted compounds 52–54. The solid‐state structural data for the simplest hydrogen‐ and methyl‐substituted derivatives were lacking (although many of the verdazyl derivatives are air‐ and water‐stable and can be stored for a long time without decomposition and thus seem quite suitable for crystallization).…”