A Family of Discrete Magnetically Switchable Nanoballs



The thermal and light-induced magnetic properties of a family of discrete magnetically switchable “nanoball” species (3 nm in diameter) is reported. The self-assembly of these materials is accomplished by the use of the metallo building block, [Cu([Tp4-py])(NCCH3)] ([Tp4-py]=tris-[3-(4'-pyridyl)pyrazol-1-yl]hydroborate), combined with a [Fe(NCX)2] (X=S, Se and BH3) species. We previously showed that the thiocyanate analogue (Fe(NCS)-nano) undergoes a thermal and light-induced spin crossover (SCO)—the largest such discrete SCO material reported. Now included in this family are the Se and BH3 analogues, Fe(NCSe)-nano and Fe(NCBH3)-nano, which show increased thermal transition temperatures (T1/2=124 K, 162 and 173 K). This variation in transition temperature over the series S<Se<BH3 results in diverse photomagnetic properties, such that the light-induced excited spin state trapping (LIESST) effect is exhibited to varying degrees and at different temperatures by the S, Se and BH3 analogues.