The solid-state behaviour of 4,6-dioxo-5,5-diethylenepyrimidine-2-isobutylurea
Abstract
The solid-state behaviour of 4,6-dioxo-5,5-diethylenepyrimidine-2-isobutylurea (PIBU) has been investigated. Two polymorphic forms have been identified, a monoclinic α form and a triclinic γ form, both of which undergo a destructive phase transition below 165 K. The α form undergoes an additional temperature-dependent phase transition at approximately 250 K to give the β form. All three forms of PIBU have been structurally characterised by