Paquette, M. M.; Patrick, B. O.; Frank,* N.L. Determining the Magnitude and Direction of Photoinduced Ligand Field Switching in Photochromic Metal–Organic Complexes: Molybdenum–Tetracarbonyl Spirooxazine Complexes J. Am. Chem. Soc. 2011 133, 10081-10093 (JUL 6 2011). DOI: 10.1021/ja109776z
The ability to optically modulate the intrinsic properties of transition metals (e.g., redox potentials, emission/absorption energies, and spin states) with photochromic metal ligand complexes is an important strategy for developing "smart" materials. We have described a methodology for using metal carbonyl complexes as spectroscopic probes of ligand field changes associated with light-induced isomerization of photochromic ligands. Changes in ligand field between the ring-closed spirooxazine (SO) and ring-opened photomerocyanine (PMC) forms of photochromic azahomoadamantyl and indolyl phenanthroline-spirooxazine ligands are demonstrated through FT-IR, (13)C NMR, and computational studies of their molybdenum tetracarbonyl complexes. Light-induced isomerization of the photochromic ligands was therefore found to lead to changes in the energies of their frontier MOs, which in turn leads to changes in pi-acceptor ability and ligand field strength. Ligand field changes associated with photoisomerizable ligands allow tuning of excited-state and ground-state energies that dictate energy/electron transfer, optical/electrical properties, and spin states of a metal center upon photoisomerization, positioning photochromic ligand-metal complexes as promising targets for smart materials.