High-pressure CO2-induced reduction of the melting temperature of ionic liquidsElectronic supplementary information (ESI) available: Fig. S1: ATR-IR spectrum of [C16mim][PF6] after it has been subjected to solution of ferrocene in CO2 at 50 °C and pressure of ca. 110 bar. See http://www.rsc.org/suppdata/cc/b2/b202759c/