Synthesis and photobiological evaluation of Ru(II) complexes with expanded chelate polypyridyl ligands

Photoreactive Ru(II) complexes capable of ejecting ligands have been used extensively for photocaging applications and for the creation of photocisplatin reagents. The incorporation of distortion into the structure of the coordination complex lowers the energy of dissociative excited states, increasing the yield of the photosubstitution reaction. While steric clash between ligands induced by adding substituents at the coordinating face of the ligand has been extensively utilized, a lesser known, more subtle approach is to distort the coordination sphere by altering the chelate ring size. Here a systematic study was performed to alter metal-ligand bond lengths, angles, and to cause intraligand distortion by introducing a linker atom or group between two pyridine rings. The synthesis, photochemistry, and photobiology of five Ru(II) complexes containing CH2, NH, O, and Slinked dipyridine ligands was investigated. All systems where stable in the dark, and three of the five were photochemically active in buffer. While a clear periodic trend was not observed, this study lays the foundation for the creation of photoactive systems utilizing an alternative type of distortion to facilitate photosubstitution reactions.

Automated summary

A systematic study was conducted to alter metal-ligand bond lengths, angles, and intraligand distortion by changing the chelate ring size and introducing a linker atom or group. This study lays the foundation for creating photoactive systems using alternative types of distortion to enhance photosubstitution reactions.