NEW MATERIAL:A metal complex of formula I [L is group of formula II (n is 1W3); M3+ is metallic ion; n is valence of the metallic ion].

EXAMPLE: A complex of 1,4,7-triazacyclononance-N,N',N"-triacetic acid and manganese.

USE: An electrochromic element. The element can be produced by using a display electrode substrate having an electrode and an electrochromic material layer formed on a substrate and a counter electrode substrate having a counter electrode formed on a substrate, placing the display electrode substrate parallel to the counter electrode substrate facing the electrodes of both substrates to each other and inserting an electrolyte between both substrates.

PREPARATION: A tosylated diethylenetriamine of formula III and a tosylated ethylene glycol of formula IV are subjected to cyclization condensation reaction to obtain the compound of formula V (Ts is tosyl). The product is detosylated by hydrolysis and made to react with a halogenocarboxylic acid of formula VI (X is halogen) in an alkali to obtain an L-ligand of formula II, which is thermally reacted with a metallic ion M3+ to obtain the compound of formula I.