Complexes formed from reactions of Re(CO)3(H2O)3+ with amines used for biological buffering

Aqueous reactions of [Re(CO)3(H2O)3]Br with tris, tricine and 1,3-diamino-2-propanol, three polyfunctional amine ligands commonly used to buffer protein solutions, led to three new metal complexes. Re(CO)3(κ3-NH2,OH,O−–tris)·3H2O (1·3H2O), [HNEt3][Re(CO)3(κ3-NH2,O−,CO2−–tricine)]·[Re(CO)3(κ3-NH2,OH,CO2−–tricine)]·2H2O (2·2H2O), and [Re(CO)3(κ3-NH2,O−,NH2–diaminopropanol)]·[Re(CO)3(κ3-NH2,OH,NH2–diaminopropanol)][Br] (3) were isolated and characterized spectroscopically and by X-ray crystallography. Each of the three compounds displays intermolecular alcohol:alkoxide OH⋯O bonding. Ramifications of this reactivity as it relates to buffering agents competing as chelating agents when proteins bind Re(CO)3(H2O)3+ is discussed.

Graphical abstractAqueous reactions of [Re(CO)3(H2O)3]Br with tris, tricine and 1,3-diamino-2-propanol, three polyfunctional amine ligands commonly used to buffer protein solutions, led to three new metal complexes. Each compounds contain one or more ReI(CO)3 unit attached to a tridentate ligand. Ramifications of this reactivity relating to protein crystal growth is discussed.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Three new compounds of Re(CO)3+ bound to the polyfunctional amines were prepared. ► We present X-ray structural information, including intermolecular hydrogen bonding. ► We discuss the need to choose protein pH buffering agents in the presence of Re(CO)3(H2O)3+.