Slow magnetic relaxation and selective luminescent probe in a 2p-3d-4f heterotrispin chain

Three types of radical-3d/3d-4f heterotrispin complexes [(Cu(hfac) 2 ) 4 (NIT-4-OMe-4PyPh) 2 ] ( 1 ), {[(Cu(hfac) 2 ) 3 (NIT-4-OMe-4PyPh) 2 ]} n ( 2 ) and {[Cu(hfac) 2 ][(NIT-4-OMe-4PyPh)] 2 [Ln(hfac) 3 ]} n (Ln = Gd 3 ; Tb 4 ; Dy 5 ; Ho 6 ) (NIT-4-OMe-4PyPh = 2-[4-methoxy-3-(4-pyridinylmethoxy)phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetonate) have been successfully synthesized by adjusting various experimental conditions. Compound 1 is a six-spin cyclic structure including a cyclic molecular structure with two Cu(hfac) 2 units linked by free NO groups, while complex 2 possesses a one-dimensional topological structure consisting of cyclic [Cu-radical] 2 dimers bridged by Cu II ions. Compounds 3-6 display a series of 2p-3d-4f heterotrispin chains in which NIT-4-OMe-4PyPh radical ligands linked Ln III and Cu II ions in "head-to-head" mode through pyridine-N atoms and NO moieties. The magnetic behavior for complex 1 revealed a dominant antiferromagnetic exchange interaction between the radical and five coordinated Cu II ions while for 2 , just a ferromagnetic Cu-ON interaction was obviously observed. Furthermore, Tb and Dy heterotrispin chains showed field-induced slow magnetic relaxation behaviors. In particular, Tb derivative shows the characteristic emission peaks of Tb III ion and can be developed as a prospective recyclable luminescent probe for detecting Fe 3+ ion. Three types of radical-3d/3d-4f heterotrispin complexes have been obtained. The Tb derivative reveals slow magnetic relaxation and a selective luminescent probe coexisting in a molecular entity.