Master of Science (MS)
David J. Brook
free radical, information storage, self-assembly, verdazyl
The goal of this research project was to prepare a self-assembled grid complex with a ditopic bis-verdazyl ligand and nickel(II) ions. A verdazyl is a relatively stable type of organic free radical in which the unpaired electron is delocalized over four nitrogen atoms. The ditopic verdazyl ligand was synthesized in six steps, and its coordination to metal ions, in particular Ni2+, was investigated. The hypothesized complex of the ligand with Ni2+ is potentially functional as a molecular magnet due to the free radical nature of the ligand; hence, the complex could be useful for information storage. The ligand was definitively characterized by mass spectrometry and ESR. The results of variable temperature ESR performed on the ligand dissolved in toluene at low temperatures indicate that the ground state of the diradical ligand is a singlet state rather than a triplet state. Infrared spectroscopy was also performed on the ligand and the resulting spectra indicated the presence of the correct functional groups of the ligand that was planned in the original design of the project. The characterization of the ligand was followed up with a number of semi-empirical A1 calculations on simpler systems to determine why the ground state of the ligand was a singlet state rather than a triplet state. The coordination compound of the ligand and Ni(II) was characterized by UV-visible spectrometry. In addition, ESI-MS was performed on the coordination compound, and the mass-to-charge ratio of the anticipated grid complex in a +1 oxidation state was observed. This ESI result was convincing evidence that self-assembly occurred. The coordination compound of the ligand with nickel will be further characterized by techniques for measuring magnetic
susceptibility and electrochemistry. If possible, X-ray crystallography will be performed on crystals of the compound.
Johnson, Erik Charles, "Synthesis of a Ditopic Verdazyl Ligand and Investigation of its Coordination to Transition Metals" (2015). Master's Theses. 4545.