The Role of Anisotropic Exchange in Single Molecule&amp;nbsp;Magnets: A CASSCF/NEVPT2 Study of the Fe&lt;sub&gt;4&amp;nbsp;&lt;/sub&gt;SMM Building Block [Fe&lt;sub&gt;2&lt;/sub&gt;(OCH&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;(dbm)&lt;sub&gt;4&lt;/sub&gt;] Dimer