Spirocyclic derivatives of nitronyl nitroxides in the design of heterospin CuII complexes manifesting spin transitions

A method was developed for the synthesis of a nitronyl nitroxide containing cyclopentane substituents in positions 4 and 5 of the imidazoline ring, viz ., 2-(3-pyridyl)-4,5-bis(spiropentyl)-4,5-dihydro-1 H -imidazole-3-oxide-1-oxyl (L CP ). The reaction of Cu II hexafluoroacetylacetonate with L CP affords different products depending on the reaction conditions: mononuclear [Cu(hfac) 2 (L CP ) 2 ], binuclear [Cu(hfac) 2 L CP ] 2 , tetranuclear {[Cu(hfac) 2 ] 4 (L CP ) 2 }, or chain polymer {[Cu(hfac) 2 ] 3 (L CP ) 2 } n . Temperature changes induce structural transformations accompanied by a change in the spin state in exchange clusters in the solid [Cu(hfac) 2 L CP ] 2 and {[Cu(hfac) 2 ] 4 (L CP ) 2 }.