Abstract We discuss the low temperature magnetic properties of (phthalocyaninato)-copper(II) iodide (Cu(pc)I). This molecular metal contains conductive stacks that incorporate a one-dimensional array of local Cu +2 moments strongly coupled to conduction electrons. Below 20K, the EPR g-value of the coupled spin system increases anomalously and at 8K the EPR signal broadens abruptly and becomes unobservable. Anomalies in the proton NMR spin-lattice relaxation times are observed at the transition temperature. Preliminary EPR experiments conducted on a newly synthesized series of materials, Cu xNi 1−x(pc)I, indicate the existence of a similar low temperature transition in the presence of various concentrations of loca moments.