Metal Complex Lipids for Fluid–Fluid Phase Separation in Coassembled Phospholipid Membranes

We demonstrate a fluid–fluid phase separation in 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphocholine (DMPC) membranes using a metal complex lipid of type [Mn(L1)] (1; HL1=1‐(2‐hydroxybenzamide)‐2‐(2‐hydroxy‐3‐formyl‐5‐hexadecyloxybenzylideneamino)ethane). Small amount of 1 produces two separated domains in DMPC, whose phase transition temperatures of lipids (Tc) are both lower than that of the pristine DMPC. Variable temperature fluorescent microscopy for giant‐unilamellar vesicles of DMPC/1 hybrids demonstrates that visible phase separations remain in fluid phases up to 37 °C, which is clearly over the Tc of DMPC. This provides a new dimension for the application of metal complex lipids toward controlling lipid distributions in fluid membranes. Coassembly of metal complex lipids with DMPC demonstrates a very rare fluid–fluid phase separation up to 37 °C.