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) (<b>L</b>) and Ln(hfac)₃ (Ln(III) = Tb (<b>1</b>), Gd (<b>2</b>) and Yb(<b>3</b>); 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 <b>1</b>－<b>3</b> 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 <b>1－3</b>. Alternating current (AC) magnetic susceptibilities demonstrate that complex <b>1</b> displays frequency-dependent signals at low temperature, while room-temperature photoluminescence spectra of complex <b>1</b> 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) (<b>L</b>) and Ln(hfac)₃ (Ln(III) = Tb (<b>1</b>), Gd (<b>2</b>) and Yb(<b>3</b>); 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 <b>1</b>－<b>3</b> exhibit isomorphism. Magnetic studies reveal that the antiferromagnetic interactions between the Ln(III) ions and nitronyl nitroxide radicals in complexes <b>1－3</b>. Alternating current (AC) magnetic susceptibilities demonstrate that complex <b>1</b> displays frequency-dependent signals at low temperature, while room-temperature photoluminescence spectra of complex <b>1</b> exhibit strong characteristic emissions in the visible region.