Nitronyl nitroxide bridged 3d-4f hetero-tri-spin chains: synthesis strategy, crystal structure and magnetic properties

Three series of 2p-3d-4f one-dimensional chains based on different substituted nitronyl nitroxide ligands have been synthesized, namely [(NIT-PhOEt) 2 Cu(hfac) 2 Dy(hfac) 3 ] 2 ·C 7 H 16 ( 1 ) and [(NIT-PhOEt) 4 {Cu(hfac) 2 }{Dy(hfac) 3 } 3 ]·H 2 O ( 2 ) (NIT-PhOEt = 2-(4′-ethoxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), [(NIT-PhOAll) 4 {Cu(hfac) 2 }{Ln(hfac) 3 } 3 ] (Ln III = Ho 3 , Er 4 , Yb 5 ; NIT-PhOAll = 2-(4′-allyloxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and [(NIT-PhOBz) 4 {Cu(hfac) 2 }{Ln(hfac) 3 } 3 ] (Ln III = Pr 6 , Sm 7 , Eu 8 ; NIT-PhOBz = 2-(4′-benzyloxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide). The crystal structures of complex 1 reveal that it is developed from alternating Dy(hfac) 3 units and Cu(hfac) 2 units bridged by NIT-PhOEt radicals coordinated by their NO groups. Complexes 2 and 3-8 are isostructural possessing 1D chains with repeating [Cu-Rad-Ln-Rad-Ln-Rad-Ln-Rad] moieties. The magnetic properties of all complexes were studied. For complexes 1 and 2 , their magnetic behaviors are attributed to the relationship between the exchange couplings for metal ions and the crystal field effect for Dy. For complexes 3-5 , the ferromagnetic exchange couplings between radical ligands and metal ions are dominated by the stronger contributions of the crystal field effect. For complexes 6-8 , the magnetic behaviors depend on the metal interaction and thermal depopulation of the excited levels for lanthanide ions. AC magnetic susceptibilities were measured for complexes 2 , 4 and 7 ; however, none of them exhibits single-chain magnetism behavior. Three series of 2p-3d-4f one-dimensional chains based on different substituted nitronyl nitroxide ligands have been synthesized with two kinds of crystal structures.