Chem. & Biochem. Seminar Series: Catherine Oertel

As part of the Department of Chemistry & Biochemistry Seminar Series, Oberlin's own Professor and Chair of Chemistry and Biochemistry Catherine Oertel will present her sabbatical report on the topic "Hybrid inorganic-organic materials as pigments and semiconductors."

This seminar will be preceded by a light reception at 4:30 p.m. in the David Love Lounge.

Sponorsed by the Luke E. Steiner Lecture Fund.

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Abstract:

Hybrid inorganic-organic materials can be designed to have a wide range of properties because both the inorganic and organic components can be modified to influence structures.  This seminar will provide updates on two projects – one involving discovery and characterization of new hybrid materials and the second focusing on a long-used but incompletely understood hybrid pigment.   

Hybrid lead halides are currently receiving widespread attention as luminescent materials and potential components in photovoltaic cells.  While the great majority of these are based on octahedral Pb(II) centers, we have synthesized pyridium lead bromide and chloride, PyPb₂X₅ (X = Cl, Br), two-dimensional compounds based on seven-coordinate Pb(II).  The observation of an inherently asymmetric monocapped trigonal prismatic geometry was corroborated by electron localization function (ELF) calculations showing a stereochemically active 6s² lone pair.  Introduction of this locally asymmetric feature in these hybrid materials poses a potential design strategy for introducing new functionality through preparation of non-centrosymmetric materials.  In a new project area, we are studying alizarin red lake pigments, which are materials that have been used for hundreds of years and that can be viewed as inorganic-organic hybrids.  Because these pigments are amorphous, their structures are not fully understood, which is an impediment to conservation of objects involving red lake paints.  New X-ray methods such as pair distribution function analysis may provide new opportunities for improving understanding of these structures.  Within both project areas, the interplay of inorganic and organic components in influencing structures and properties will be discussed.