Syntheses, structures, and magnetic properties of a series of dimer lanthanide complexes with 5-isoquinoline-substituted nitronyl nitroxide

Three lanthanide-radical cyclic dimers with the formula [Ln(hfac)3(NIT-5-IQN)]2, derived from a new isoquinolyl-substituted nitronyl nitroxide ligand (NIT-5-IQN) (L) and Ln(hfac)3 (Ln(III) = Tb (1), Gd (2) and Yb(3); NIT-5-IQN = 2-(5-isoquinoly)-4,4,5,5 -tetramethyl-imidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetonato anion), were synthesized and characterized structurally and magnetically. Single-crystal structural analyses reveal that complexes 1－3 exhibit isomorphism, in which the NIT-5-IQN molecule acts as a bridging ligand linking two Ln(III) ions through the oxygen atom of the N–O group and the nitrogen atom from the isoquinoline unit to form a ring-like dimer. Magnetic studies reveal the antiferromagnetic interactions between the Ln(III) ions and nitronyl nitroxide radicals in complexes 1－3. Alternating current (AC) magnetic susceptibilities demonstrate that complex 1 displays frequency-dependent signals at low temperature, while room-temperature photoluminescence spectra of complex 1 exhibit strong characteristic emissions in the visible region. A series of lanthanide-radical dimers with the formula [Ln(hfac)3(NIT-5-IQN)]2, derived from a new isoquinolyl-substituted nitronyl nitroxide ligand (NIT-5-IQN) (L) and Ln(hfac)3 (Ln(III) = Tb (1), Gd (2) and Yb(3); NIT-5-IQN = 2-(5-isoquinoly)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetonato anion), were synthesized and characterized structurally and magnetically. Single-crystal structural analyses reveal that complexes 1－3 exhibit isomorphism. Magnetic studies reveal that the antiferromagnetic interactions between the Ln(III) ions and nitronyl nitroxide radicals in complexes 1－3. Alternating current (AC) magnetic susceptibilities demonstrate that complex 1 displays frequency-dependent signals at low temperature, while room-temperature photoluminescence spectra of complex 1 exhibit strong characteristic emissions in the visible region.