After multiple attempts I've finally succeeded in synthesizing thallium cyanide. The prep was not terribly efficient but nevertheless there it is. This is made by combining saturated solutions of thallium(I) nitrate and an alkali cyanide. Thallium cyanide precipitates out. It's best done with cold solutions. Thallium cyanide is not stable at high temps and will begin to decompose in a hot solution. Solid thallium cyanide breaks down when heated (probably to the monovalent oxide). It is not photosensitive. However, it's always a brownish color when it first precipitates. It turns white after sitting under the solution it precipitated from overnight.