An Integrated Protocol for the Accurate Calculation of Magnetic Interactions in Organic Magnets

A new, fast, and efficient computational protocol for the accurate calculation of singlet triplet magnetic splittings in organic diradicals is tested and validated. This procedure essentially consists of three steps: the adoption of modified virtual orbitals (MVO) and a mixed variational-perturbational approach (CSPA) are now combined with a third method that exploits the reduction of the configurational space dimensions achieved by fragmentation/localization criteria. This innovative approach is successfully tested on four different substituted m-phenylene bis(tert-butyl) nitroxides, which show paramagnetic behavior, by computing singlet triplet energy gaps and comparing them with their experimental counterparts.