| Design, synthesis, and characterization of novel high-spin species are critical in better understanding the field of molecular magnetism. It is also critical in advancing the field to a level of application, where new magnetic materials can be used in daily life. In this work, structure-property relationships of mono- and bis(semiquinone)s (SQs) were studied, substituent effects on exchange coupling and other physical properties were investigated, and a series of novel manganese (II), copper (II) and zinc complexes were synthesized and characterized.; Within an isostructural series of SQs and their MnII and CuII complexes, substituents were found to modulate reduction potentials, UV-visible absorption maxima and exchange coupling. This work represents the first examination of whether an empirical relationship exists between these physical properties of these radical anionic systems and Hammett σ parameters.; In a related investigation, SQ species with planar geometry and their CuII complexes were prepared. Preliminary results indicate that substituent effects in these systems are nominal.; Finally, three meta-phenylene-type (MPL), ferromagnetically coupled bis(SQ)s (substituents = H, Ph, OCH3) were prepared to continue an earlier project which determined that both donating (NMe2) and withdrawing (NO2) groups attenuate the singlet-triplet gap (ΔEST ) in the ground-state triplet species. A relatively simple Hückel molecular orbital explanation described the effect. It is the first time that a singlet-triplet gap (ΔEST) of a ground-state triplet biradical has been affected by substituents. The results of this research were found to be consistent with earlier work. |
