Ring-shaped rhenium(I) multinuclear complexes: improved synthesis and photoinduced multielectron accumulation.

We successfully developed selective synthesis of strongly emissive ring-shaped Re(I) multinuclear complexes (RnP(x)(n+) in Chart 1) with much higher yields compared with the previously reported method. This improved method could also be employed to prepare a novel ring-shaped multinuclear complex composed of structurally different Re(I) units. Each Re unit in RnP(x)(n+) could electrochemically accept one electron, and the multielectron reduced states of RnP(x)(n+) were stable. In the presence of triethanolamine, the ring-shaped tetranuclear and hexanuclear complexes can be photochemically reduced and accumulate 2.9-3.6 and 4.4 electrons in one molecule, respectively.

CO2 capture by a rhenium(I) complex with the aid of triethanolamine.

A rhenium(I) tricarbonyl diimine complex with a N,N-dimethylformamide ligand captures one CO2 molecule in the presence of triethanolamine (TEOA), giving fac-[Re(I)(bpy)(CO)3{R2N-CH2CH2O-COO}] (bpy = 2,2'-bipyridine, R = CH2CH2OH). This could be a predominant complex in various photocatalytic CO2 reduction reactions using [Re(I)(N^N)(CO)3X](n+) (N^N = diimine ligand; X = monodentate ligand; n = 0, 1) type complexes in the presence of TEOA.

Systematic synthesis, isolation, and photophysical properties of linear-shaped Re(I) oligomers and polymers with 2-20 units.

Systematic synthesis routes have been developed for the linear-shaped rhenium(I) oligomers and polymers bridged with bidentate phosphorus ligands, [Re(N--N)(CO)3-PP-{Re(N--N)(CO)2-PP-}(n)Re(N--N)(CO)3](PF6)(n+2) (N--N = diimine, PP = bidentate phosphine, n = 0-18). These were isolated by size exclusion chromatography (SEC) and identified by (1)H NMR, IR, electrospray ionization Fourier transform mass spectrometry, analytical SEC, and elemental analysis. Crystal structures of [Re(bpy)(CO)3-Ph2PC[triple bond]CPPh2-Re(bpy)(CO)3](PF6)2, [Re(bpy)(CO)3-Ph2PC[triple bond]CPPh2-Re(bpy)(CO)2-Ph2PC[triple bond]CPPh2-Re(bpy)(CO)3](PF6)3 and [Re(bpy)(CO)3-Ph2PC2H4PPh2-{Re(bpy)(CO)2Ph2PC2H4PPh2-}(n)Re(bpy)(CO)3](PF6)(n+2) (bpy = 2,2'-bipyridine, n = 1, 2) were obtained, showing that they have interligand pi-pi interaction between the bpy ligand and the phenyl groups on the phosphorus ligand. All of the oligomers and polymers synthesized were emissive at room temperature in solution. For the dimers, broad emission was observed with a maximum at 523-545 nm, from the (3)MLCT excited-state of the tricarbonyl complex unit, [Re(N--N)(CO)3-PP-]. Emission from the longer oligomers and polymers with > or = 3 Re(I) units was observed at wavelengths 50-60 nm longer than those of the corresponding dimers. This fact and the emission decay results clearly show that energy transfer from the edge unit to the interior unit occurs with a rate constant of (0.9 x 10(8))-(2.5 x 10(8)) s(-1). The efficient energy transfer and the smaller exclusive volume of the longer Re(I) polymers indicated intermolecular aggregation for these polymers in an MeCN solution.