Synthesis, structure and magnetic properties of transition metal complexes of the nitroxide 2′,5′-dihydro-4′,5′,5′-trimethyl-spiro-[4,5-diazafluorene-9,2′-imidazol]-1-oxyl

Abstract

With the radical 2′,5′-dihydro-4′,5′,5′-trimethyl-spiro-[4,5-diazafluorene-9,2′-imidazol]-1-oxyl L a series of transition metal complexes has been prepared: [ ML 3]( SbF 6) 2 · 4 H 2 O with M 2+ = Mn 2+ ( 1), Fe 2+ ( 2) , Co 2+ ( 3), Ni 2+ ( 4), Zn 2+ ( 5). Reaction of L with Cu 2+ in methanol yielded different products depending on the counterion. In the presence of weakly coordinating anions the Cu(I) complexes [Cu 2L 3](SbF 6) 2 · H 2O ( 6), [Cu 2L 3](OTf) 2 · 2MeOH ( 7) and [Cu 2L 3](ClO 4) 2 ( 8) were formed. Stronger coordinating counter ions gave the complexes CuL 2Cl 2 · H 2O ( 9), CuL 2Br 2 · H 2O ( 10) and CuL 2(NO 3) 2 ( 11). Also the synthesis of [Ag 2L 3](SbF 6) 2 · 2H 2O ( 12), Pd(L)Cl 2 · H 2O ( 13), Pt(L)Cl 2 · H 2O ( 14), Ni(L)Cl 2 ( 15a), Ni(L)Cl 2 · 4H 2O ( 15b) and [Ru(bipy) 2(L)]Cl 2 · 4H 2O ( 16) is reported. The magnetic moments of 1–6 and 10 correspond in the range 200–300 K to those expected for noninteracting spins of the metal ion and the radicals. At low temperatures spin pairing of metal and radical spins is observed for 1–3.