Polymorphism in complexes with metal-metal interactions has been widely developed in (d10) gold(I) chemistry,1,2 and has recently been extended to (d8) platinum(II)-(s2) thallium(I) compounds.3 We are actively exploring similar stacked, square-planar rhodium(I) and iridium(I) complexes that often afford interesting supramolecular structures, and display tunable spectroscopic and photophysical properties. The polymorphic structures and metallophilic interactions are correlated with the observed colors and emissive behaviors that are sensitive to environmental effects, such as variations in pressure and temperature, or exposure to volatile organic solvents. Dimorphs of iridium(I) dicarbonyl-ketoiminate will be discussed in relation to their solid-state structures and red luminescence at low temperatures.

1. White-Morris, R. L.; Olmstead, M. M.; Balch, A. L. J. Am. Chem. Soc. 2003, 125, 1033-1040. 2. Gussenhoven, E. M.; Fettinger, J. C.; Pham, D. M.; Malwitz, M. A.; Balch, A. L. J. Am. Chem. Soc. 2005, 127, 10838-10839. 3. Stork, J. R.; Olmstead, M. M.; Balch, A. L. J. Am. Chem. Soc. 2005, 127, 6512-6513.