Dimorphism in a 2,2′,2′-terpyridyl compound

Chloro-(2,2',2 -terpyridine)platinum(II) chloride dihydrate, [Pt(terpy)Cl]Cl . 2H(2)O, crystallizes from aqueous EtOH (1:1) as a yellow dimorph, but from dilute (1 M) HCl as its less stable red dimorph. X-ray powder photography shows that, above 100 degreesC, the red form converts into the yellow form.