Solvent-Dependent Dynamics of a Series of Rhenium Photoactivated Catalysts Measured with Ultrafast 2DIR

Abstract

The spectral dynamics of a series of rhenium photocatalysts, fac-Re(4,4'-R2-bpy)(CO)3Cl, where R = H, methyl, t-butyl, and carboxylic acid, as well as Re(1,10-phenanthroline)(CO)3Cl were observed in multiple aprotic solvents using two-dimensional infrared spectroscopy (2DIR). The carbonyl vibrational stretching frequencies showed slight variations due to the electron-donating or -withdrawing nature of the substituents on the bipyridine. The different substituents had minimal to no influence on the spectral diffusion time scales of the compounds within a particular solvent, but among the three different solvents investigated (DMSO, THF, and CH3CN), we find the spectral diffusion times to correlate with the solvent's donor number (DN). Because the donicity is a measure the Lewis basicity of the solvent, these findings may help establish a more complete dynamical picture of the photocatalysis, where the first chemical step following optical excitation is electron transfer from a sacrificial donor to the rhenium complex.

Dye aggregation identified by vibrational coupling using 2D IR spectroscopy

“…Nonetheless, we believe that the same conclusions should hold, since ReCC and ReC only differ by an anchoring group and we know from the previous work that the relaxation dynamics of the Re-CO groups are independent of the anchoring group. 11,40,41 Thus, we conclude that neither ReC nor ReCC have appreciable amounts of intra-aggregate relaxation.…”

On the Simulation of Two‐dimensional Electronic Spectroscopy of Indole‐containing Peptides

“…The advent of two‐dimensional (2D) spectroscopy , a nonlinear multipulse technique, introduced new potential tools for the determination of protein structures. The pioneering 2D technique, nuclear magnetic resonance (2DNMR) , is a key experimental methodology capable of resolving detailed structural information of proteins by detecting the couplings of spin transitions.…”

“…The technique has, however, some drawbacks like the lack millisecond temporal resolution which impedes its application to protein folding process . 2D spectroscopy has been recently extended in the optical domain to the infrared (IR), visible (VIS) and ultraviolet (UV) regimes, thus addressing vibrational (2DIR) and electronic (2DES) transitions . 2DIR is nowadays a standard technique that allows insights into the conformational dynamics through probing vibrational modes of backbone amide groups.…”

Solvent exchange in preformed photocatalyst-donor precursor complexes determines efficiency

“…Preferential solvation, on the other hand, shifts the maximum towards lower concentration of the preferred species. We expect TEOA to preferentially solvate the highly polar (14.1 Debye) 19 , 20 Re catalyst because TEOA is more polar than THF. We note that the spectral diffusion time scales change with increased concentration above 20% TEOA, and are anti-correlated with the solution's viscosity.…”

“…Decoupling from viscosity is not unusual, however, and has been seen in several contexts such as simple liquids, glass forming liquids, and liquid crystals. 19 , 21 – 24 …”