Synthesis, characterization, electrochemical and photophysical properties of bimetallic complexes of rhenium(I) and osmium(II)

Monometallic and bimetallic diimine complexes of rhenium(I) and osmium(II), [(CO)3(bpy)Re(4,4′-bpy)](PF6) I, [(CO)3(bpy)Re(4,4′-bpy)Re(bpy)(CO)3](PF6)2II, [Cl(bpy)2Os(4,4′-bpy)](PF6) III and [Cl(bpy)2Os(4,4′-bpy)Os(bpy)2Cl](PF6)2IV, and a new heterobimetallic complex of rhenium(I) and osmium(II) [(CO)3(bpy)Re(4,4′-bpy)Os(bpy)Cl](PF6)2V (bpy = 2,2′-bipyridine; 4,4′-bpy = 4,4′-bipyridine) have been synthesized and characterized by various spectral techniques. The photophysical properties of all the complexes have been studied and a comparison is made between the heterobimetallic and corresponding monometallic and homobimetallic complexes. Emission and transient absorption spectral studies reveal that excited state energy transfer from the rhenium(I) chromophore (∗Re) to osmium(II) takes place. The energy transfer rate constant is found to be 8.7 × 107 s−1.

Graphical abstractMonometallic and bimetallic diimine complexes of rhenium(I) and osmium(II), [(CO)3(bpy)Re(4,4′-bpy)](PF6) I, [(CO)3(bpy)Re(4,4′-bpy)Re(bpy)(CO)3](PF6)2II, [Cl(bpy)2Os(4,4′-bpy)](PF6) III and [Cl(bpy)2Os(4,4′-bpy)Os(bpy)2Cl](PF6)2IV, and a new heterobimetallic complex of rhenium(I) and osmium(II) [(CO)3(bpy)Re(4,4′-bpy)Os(bpy)Cl](PF6)2V (bpy = 2,2′-bipyridine; 4,4′-bpy = 4,4′-bipyridine) have been synthesized and characterized by various spectral techniques. The photophysical properties of all the complexes have been studied and a comparison is made between the heterobimetallic and corresponding monometallic and homobimetallic complexes. Emission and transient absorption spectral studies reveal that an excited state energy transfer from the rhenium(I) chromophore (∗Re) to osmium(II) takes place. The energy transfer rate constant is found to be 8.7 × 107 s−1.Figure optionsDownload full-size imageDownload as PowerPoint slide