  Two decades of intensive research in lanthanide-based molecular nanomagnets
have brought the magnetic memory in molecules from liquid helium to liquid
nitrogen temperature. In the pursuit of new derivatives with improved
operational temperatures, several "rational" strategies have been proposed and
applied through a fluid transfer of knowledge between theoreticians and
experimentalists. These have mainly focused on the choice of the magnetic ion
and the design of an adequate coordination environment, both in terms of
magnetic anisotropy and molecular vibrations. However, much of the progress has
been achieved by serendipity, oversimplified theories and chemical intuition.
In order to draw conclusions on the chemical design key parameters that govern
the physical behavior of molecular nanomagnets in terms of magnetic memory, we
apply here a state-of-the-art inferential statistical analysis to a body of
over a thousand published experiments. Our analysis shows that the effective
barrier derived from an Arrhenius equation displays an excellent correlation
with the magnetic memory, and that there are only two promising strategies
between all alternatives proposed so far, namely terbium bis-phthalocyaninato
sandwiches and dysprosium metallocenes. In addition, we provide an interactive
dashboard for visualizing the collected data, which contains all the reported
cases between 2003 and 2019. This meta-study aims to dispel widespread
theoretical misconceptions and will allow researchers in the field to avoid
experimental blind alleys.
