Glassy magnets composed of metals coordinated to 7,7,8,8-tetracyanoquinodimethane: M(TCNQ)2 (M = Mn, Fe, Co, Ni)

The homologous series M(TCNQ)2 (M = Mn(II), Fe(II), Co(II), and Ni(II); TCNQ = 7,7,8,8-tetracyanoquinodimethane) prepared from reactions of [M(CH3CN)6][BF4]2 and [n-Bu4N][BF4] in CH3CN has been carefully analyzed from the perspective of synthetic issues and physical characterization, including complete magnetic analyses by the tools of dc and ac magnetometry. The preparative method was optimized to definitively establish the reproducibility of the chemistry as judged by infrared spectroscopy, thermal gravimetric analysis, powder X-ray crystallography, and elemental analysis. Scanning electron microscopic (SEM) and transmission electron microscopic (TEM) studies results are also in accord with the conclusion that these materials are pure, isostructural phases. The dc magnetic measurements reveal a spontaneous magnetization for the four materials at low temperatures with a weak field coercivity of 20, 750, 190, and 270 G at 2 K for Mn(TCNQ)2, Fe(TCNQ)2, Co(TCNQ)2, and Ni(TCNQ)2, respectively. At low tempera...