Photocatalysis of oligo(p-phenylenes): photochemical reduction of carbon dioxide with triethylamine

Abstract

4437MA-CVE sample. The technical assistance of Mrs. L. Mansuy in the synthesis of dialkyl viologens is also gratefully acknowledged. Registry No. di-C4 viologen, 36437-30-6; di-C, viologen, 6 159-05-3; di-C8 viologen, 32449-1 8-6; di-C4 viologen radical cation, 87922-26-7; di-C, viologen radical cation, 631 19-42-6; di-C8 viologen radical cation, 49765-26-6; PSSH, 50851-57-5; MA-CVE, 26935-44-4. have tried to interpret the data on semiquantitative grounds after having developed a kinetic model which takes very satisfactorily into account the disappearance of the reduced viologens in the absence of stabilizing agent. Acknowledgment.We are indebted to Dr. E. Pefferkorn (Institut Charles Sadron, Strasbourg) for providing us with the Photoreduction of C02 to formic acid (HCO,) and a small quantity of carbon monoxide (CO) can be achieved in nonaqueous polar solvent by using oligob-phenylenes) (OPP-n) as a photocatalyst and triethylamine (TEA) as a sacrificial electron donor under >290-nm irradiation, where the photocatalysis in N,N-dimethylformamide leads to the most effective formation of HC0,-and CO. Among OPP-n, OPP-3 and OPP-4 show high photocatalytic activity for the formation of HC02-, in which the apparent quantum yields of HCOT formation for OPP-3 and OPP-4 are 0.072 and 0.084, respectively. Although photocatalyst OPP-3 itself concurrently undergoes photo-Birch reduction during the photocatalysis, the turnover number for the formation of HC02-based on the reacted OPP-3 is calculated to be 4, implying a cyclic activity of the reduction system. The laser flash photolysis and pulse radiolysis studies reveal that the photocatalysis initially starts from the reductive quenching of the singlet state of OPP-n by TEA followed by the formation of the radical anion of OPP-n, OPP-n'-, resulting in direct electron transfer from OPP-n'-to C 0 2 molecules.

Photocatalytic CO 2 reduction with high turnover frequency and selectivity of formic acid formation using Ru(II) multinuclear complexes

“…The photocatalytic activities of (1,2), (1,3), and the mixed system of (1,0) and (0,1) deteriorated rapidly and the reaction solution turned black even in the early stages of irradiation, as described above. As a typical example, Fig.…”

“…6A, the deactivation of the photocatalysts ð1; 0Þ þ ð0; 1Þ, (1,2), and (1,3) is presumably due to the formation of similar oligomers and/or polymers from the reduced catalyst or catalyst unit produced during irradiation ¶ . Lower photocatalytic abilities of ð1; 0Þ þ ð0; 1Þ, (1,2), and (1,3) in the LIC1 were observed compared with those in the LIC2 ("products" vs. "TON HCOOH " in Table 1). As described above, the formation of the oligomers and/or polymers was enhanced with the lower light intensity.…”

“…Only a few photocatalysts for the selective formation of formic acid from CO 2 have been reported (3)(4)(5)(6)(7)(8). Although oligo(p-phenylenes) (3) or a mixed system of phenazine and Co cyclam (4) successfully photocatalyzed the reduction of CO 2 to formic acid, these systems cannot work with visible light.…”

Computational design of a renewable organic reagent for photochemical reduction of CO2 with visible light

“…9 The known organic photocatalysts that can accomplish this difficult step all operate with UV light. 5 The success of transition metal complexes in achieving the chemistry with visible light apparently arises from their ability to bind CO 2 •-to the metal, thereby making the reduction more favorable and reducing the energy of the photons required to drive it. 10 It is not at all obvious how one would adopt a similar strategy in an organic system.…”

“…3 In the prototype for the new strategy, we used a photocatalyst whose absorption maximum was in the UV. 5 Ultimately, such a photocatalyst will not be optimal if one wants to harness solar radiation as the energy source, because the maximum in the sea level solar irradiance spectrum occurs near 600 nm. We have obtained preliminary results showing that the same reducing agent will work with rhenium catalysts operating in the visible region.…”