Development of stopped-flow instrument with spectrophotometric detection for the study of fast reactions in supercritical carbon dioxide; kinetics of metalloporphyrin formation in supercritical carbon dioxide

A high-pressure stopped-flow instrument with spectrophotometric detection has been developed, which enables us to follow fast reactions with half-lives longer than 10 ms in supercritical carbon dioxide (scCO2) at various temperatures up to 150 °C and pressures up to 30 MPa. The rate of the metalloporphyrin formation reaction in scCO2 between 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin and bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)copper(II) (Cu(hfac)2) was successfully measured under a variety of excess concentrations (CCu) of Cu(hfac)2. Based on the dependence of the conditional first-order rate constants on CCu, the metalation mechanism was evaluated in scCO2.