The introduction of liquid microjet technology, enabling vacuum-based probes of the liquid phase, has allowed researchers to develop an exciting range of new experiments in the last ten years. Such experiments are designed to gain greater insight into molecular behavior inside liquids and at liquid interfaces, in turn providing a new tool for physical chemistry. For example, ultrafast photoelectron and X-ray spectroscopies provide a new window on time-resolved photophysics and photochemistry, redox thermodynamics, solvation and liquid structure, and condensed phase electronic structure. Chemical speciation at liquid interfaces, scattering and energy loss as particles move through liquids, and even nanoparticle and MOF preparations may now be more readily analyzed. This issue will showcase recent developments and applications of liquid microjets for chemical research. This special issue, guest-edited by Stephen Bradforth (University of Southern California), Gil Nathanson (University of Wisconsin-Madison), and Robert Seidel (Helmholtz-Zentrum Berlin), will highlight recent developments in Applications of Liquid Microjets in Chemistry. Check back frequently as this special issue builds online.

Epoxide/CO₂ ROCOP using L2

Several research teams have investigated s-block heterodinuclear metal complexes of L2, particularly focusing on the influence of local electric fields on electron, proton, and hydrogen atom transfers. (40−43) We selected L2 for heterodinuclear polymerization catalysis using transition metals(II/III) and s-block metals(I/II) (Figure 4, left). Our prior work using L1 showed that these metal combinations were ineffective, but the “crown ether” binding pocket in L2 is much better suited to s-block metal coordination chemistry. First, L2 complexes using four different metal combinations were investigated for CHO/CO₂ ROCOP: Zn(II)Na(I), Mg(II)Na(I), Co(III)Na(I), and Zn(II)Mg(II). (44) The Zn(II)Mg(II) complex was completely inactive, in contrast to the synergy observed using these metals with L1 (vide supra). (35) Mg(II)Na(I) also showed a low activity, but Zn(II)Na(I) showed promising performances (TOF = 29 h^–1, PCHC selectivity = 94%, 1 bar CO₂, 0.025 mol % catalyst). The best catalyst was Co(III)Na(I), which showed a very high activity (TOF = 1590 h^–1, PCHC selectivity >99%, 100 °C, 1 bar CO₂, 0.025 mol % catalyst); it is the most active low-pressure CHO/CO₂ ROCOP catalyst reported to date.