Understanding and controlling the surface composition of metalloporphyrins in ionic liquids (ILs) is crucial for designing photoactive materials. Here, we investigate the interfacial behavior of zinc‐didodecylporphyrin molecules (Zn‐DDP) dissolved in the hydrophobic ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate C 4 C 1 ImPF 6 using angle‐resolved X‐ray photoelectron spectroscopy (ARXPS). Upon mild heating, Zn‐DDP undergoes spontaneous demetallation, evidenced by the appearance of aminic (–NH–) and iminic (=N–) nitrogen XPS signals characteristic of the free‐base porphyrins. Partial hydrolysis of PF 6 ‐ anions produces phosphate species that contribute to the demetallation process. Concentration‐dependent measurements reveal extremely high surface enrichment of porphyrins at the IL/vacuum interface, reaching surface saturation already at about 0.50% mol Zn‐DDP content in the bulk. The dodecyl chains of porphyrins at the outer surface are oriented toward the vacuum in a buoy‐like configuration. Temperature‐dependent ARXP spectra reveal that for unsaturated interfaces, surface enrichment increases with increasing temperature. Our findings provide molecular‐level insights to guide the design of porphyrin‐based photoactive interfaces in ionic liquid systems.
Ceccatto et al. (Mon,) studied this question.