3d- and 4f-based single molecule magnets

Research in the area of single molecule magnets began in 1991 with reports on a dodecanuclear mixed-valent manganese complex,^1,2 but took a new direction in 2003 with reports from Ishikawa of remarkable energy barriers for loss of magnetization.³ Since around 2011^4,5 advances in this area have been dominated by studies of molecules that contain a single lanthanide centrednormally dysprosium(III)dwith some studies of monometallic 3d-metal compounds. As there is only a single magnetic centre, these are sometimes called “single ion magnets”; this seems a catchphrase too far as clearly the entire molecule is needed for the properties observed. It is also important to differentiate this work from genuine studies of “single ion magnets”. For example, Heinrich and others,^6,7 have studied the magnetism of a single iondholmium(III) for exampledby scanning tunneling microscopy on a suitable surface. This is chemically a very different entity from any metal-organic lanthanide complex.