The copper salts of DCNQI (N,N'-dicyanoquinonediimine). quasi-three-dimensional system, show three possible modes of behavior at low temperatures: they remain metallic, they undergo a phase transition, or they have a suppressed phase transition, as is the case for alloyed copper salts. Deuteration of these salts can change their behavior. Alloyed deuterated copper-DCNQI salts have been investigated using electron spin resonance, susceptibility, and conductivity measurements, revealing a reduction of the phase transition temperature-with hysteresis-and reentry effects in the conductivity.