Effect of second-sphere coordination 12. Adduct formation behavior of crown ethers with ammine complexes of ruthenium containing a protic ligand of other type than ammine

Adduct formation of pentaammineruthenium complexes involving a different type of protic ligand, such as imidazole, was investigated for a series of crown ethers with different ring size. Changes in redox potential and in absorption spectra of the complex were measured on addition of crown ether to the complex solution. The magnitude of the change in both properties is dependent on the ring size of crown ethers. 1H-NMR spectra of the complex were measured in the presence of crown ethers in order to elucidate hydrogen bonding sites. The chemical shifts of NH proton of imidazol and ammine protons were measured at various concentrations of crown ethers. Adduct formation was discussed based on the features of dependences of those chemical shifts on crown ether concentration.

Graphical abstractAdduct formation was investigated for ruthenium complexes containing protic ligands of different types within a complex. 18-crown-6 ether showed different behavior of adduct formation from 15-crown-5 ether and 12-crown-4 ether. 18-Crown-6 ether binds step wisely to the complex, forming hydrogen bonds selectively at different protic ligand sites of the complex.Figure optionsDownload full-size imageDownload as PowerPoint slide