The vaporization enthalpies of [C n TPP][Cu(F 6 -acac) 3 ] ( n = 14, 16) and [C n mim][Cu(F 6 -acac) 3 ] ( n = 8, 10), a new type of chelate-based ionic liquids (ChILs), were measured by thermogravimetric analysis (Δgl H om( T av ) = 73.2-83.7 kJ mol -1 ), which decreased compared to their non-chelate counterparts (difference up to 34.1 kJ mol -1 ). This can be explained by the fact that the increase in the polar region size by chelate ions mainly leads to the decrease in Coulomb forces based on the micro-biphasic separation in ionic liquids. Vaporization enthalpies at experimental temperatures were adjusted to a reference temperature by the Verevkin's method, and compared with the data calculated by the Kabo's method, which illustrated clear differences on ChILs. In addition, some physicochemical properties of [C n TPP][Cu(F 6 -acac) 3 ] ( n = 14, 16) were measured including density, viscosity, conductivity, and surface tension.