Research Abstracts Online
January 2010 - March 2011
University of Minnesota Duluth
Swenson College of Science and Engineering
of Chemistry and Biochemistry
PI: Viktor N. Nemykin, Associate Fellow
Electronic Structure and Spectroscopy of Transition Metal Porphyrinoids
Multinuclear-containing complexes with strong long-range metal-metal coupling represent an important class of metallocomplexes. These molecules are interesting both from the fundamental (multiredox processes, magnetic coupling, and unpaired electron density migration) and practical (opto-electronic materials for application in high-speed photonic or redox devices) points of view. Thus, the chemistry related to such compounds is of fundamental importance. Polyferrocenyl-containing molecules are among the best candidates for the multimetal redox active groups because of their well-known metal-metal coupling properties. Formation of the mixed-valence complexes in bisferrocenes was discovered a long time ago and the influence of the different factors on the formation and stability of mixed-valence states has been intensively investigated. The outstanding thermal and chemical stabilities as well as the possibility to tune a macrocyclic redox potential make porphyrins and related compounds among of the best candidates for the ligand, which can connect several redox-active metallocenters. These properties have been utilized in the first useful molecular storage device.
These researchers have recently confirmed the formation of the mixed-valence states in the meso-tetraferrocenylporphyrins. More importantly, the temperature-dependent electron migration between one of the ferrocene group and macrocycle has been observed. Since there is no convenient model for the explanation of the long-range metal-metal coupling present, it will be extremely useful to model properties of meso-tetraferrocenylporphyrins computationally. The researchers have prepared additional compounds in addition to these ferrocenyl-containing porphyrins. In these compounds, metallocenyl substituents are located in axial rather in equatorial position, which dramatically effects their optical, mixed-valence, and fluorescent properties. In order to understand the differences between these two groups of metallocenyl-containing porphyrins, the researchers need insight into their electronic structures as well as understanding of the spectroscopic differences, which will be modeled using modern computational approaches.
Derric Anderson, Graduate Student
Ryan Hadt, Graduate Student
Jared Sabin, Undergraduate Student
Pavel Solntsev, Research Associate