Table 1.

Classification of DESs.

Type	General Formula	Terms
I	${\mathrm{Cat}}^{+}{\mathrm{X}}^{-}z{\mathrm{MCl}}_x$	M = Zn, Sn, Fe, Al, Ga, In
II	${\mathrm{Cat}}^{+}{\mathrm{X}}^{-}z{\mathrm{MCl}}_x.y{\mathrm{H}}_2\mathrm{O}$	M = Cr, Co, Cu, Ni, Fe
III	${\mathrm{Cat}}^{+}{\mathrm{X}}^{-}z\mathrm{RZ}$	Z = CONH2, COOH, OH
IV	${\mathrm{MCl}}_x+\mathrm{RZ}={\mathrm{MCl}}_{x-1}{}^{+}.\mathrm{RZ}+{\mathrm{MCl}}_{x+1}{}^{-}$	M = Al, Zn and Z = CONH2
V	Non-ionic DES	Composed only of molecular substances