The Ruhlandt group's research focus is the chemistry of the heavy alkali and alkaline earth and selected rare earth metals. Particular research interests lie in the preparation of novel compounds with applications in polymerization and synthetic chemistry, the development of novel source materials for MOCVD applications, and the preparation of biomimetic calcium phosphonates to be used in bone cements and as bone scaffolding material.
Despite exciting applications in synthetic and polymer chemistry, the organometallic chemistry of the heavy alkaline earth metals remains poorly understood; major breakthroughs are only now emerging. Further progress critically depends on the development of reliable and facile synthetic regimen and the introduction of novel ligand systems to achieve improved understanding and utility of the many applications. Due to the similarities of divalent rare earth metal compounds and calcium and strontium due to similar size charge ratios, principles developed for the rare earth metal may be modified and used for the lesser developed alkaline earth metals. In the last few years, our group has developed synthetic methodologies and prepared several families of alkaline earth organometallics, leading to an increased understanding of the organometallics while opening new applications. Current work is extending this group of compounds and testing the novel materials in synthetic, medicinal and polymer applications.
Our second major research focus is the preparation of novel precursor materials for MOCVD leading to alkaline earth metal containing solid-state materials. Solid-state materials containing group 2 elements range from insulators to high temperature superconductors. Widely recognized are capacitance-based devices such as dynamic random access memory (DRAM) circuits. These require materials with a high dielectric performance, as displayed by alkaline earth metal titanates MTiO3 (M= Sr, Ba or mixtures thereof). Other applications include high temperature superconductors such as YBa2Cu3O7-δ, Bi2Sr2CaCu2O8-δ and Tl2Ba2Ca2Cu3O8 with a Tc as high as 134 K. Alkaline earth metals are also essential in flat panel displays based on electroluminesce technology. These contain a doped dielectric layer, typically a binary metal sulfide where the metal is either Ca, Sr, or Zn. Electroluminescent displays are not shock sensitive like liquid crystal displays, and do not require backlighting, cross polarizers or filters. Moreover, the displays are brighter than the more common LCD counterparts and display higher contrast. The preparation of the MOCVD precursors requires thermally stable, highly volatile precursor materials to enable the deposition of thin films. With a continuing need for optimal precursors, our work is geared towards the development of facile synthetic routes and the introduction of novel ligand systems. Research methods in the laboratory include inert gas chemistry both on a Schlenk line and in the glove box, low temperature crystallography, various NMR spectroscopic methods, IR spectroscopy, thermogravimetrical analysis, and more.
Deacon, G. B.; Junk, P. C.; Moxey, G. J.; Ruhlandt-Senge, K.; St. Prix, C.; Zuniga, M. F. Charge-Separated and Molecular Heterobimetallic Rare Earth - Rare Earth and Alkaline Earth - Rare Earth Aryloxo Complexes Featuring Intramolecular Metal-π-arene Interactions. Chem., Eur. J. 2009, 5503-5519.
Gillett-Kunnath, M. M.; MacLellan, J. G.; Forsyth, C. M.; Andrews, P. C., Deacon, G. B.; Ruhlandt-Senge, K. BiPh3 – A convenient synthon for heavy alkaline earth metal amides. Chem. Commun. 2008, 4490-4492.
Guino-o, M. A.; Campana, C. F.; Ruhlandt-Senge, K. A unique heterobimetallic calcium benzylate - an organometallic mixed metal species involving a heavy alkaline earth metal. Chem. Commun. 2008, 1692-1694.
Alexander, J. S.; Teng, W.; Allis, D. G.; Ruhlandt-Senge, K. Alkali metal diphenylmethanides: synthetic, calculations and structural studies. Chem., Eur. J. 2007, 13, 9899-9911.
Zuniga, M. F.; Deacon. G. B.; Ruhlandt-Senge, K. New structural features in heavy alkaline earth metal chemistry- molecular heterobimetallic Group I/Ba complexes. Chem., Eur. J. 2007, 13, 1921-1928.