Ferrimagnetic Ordering and Anomalous Stoichiometry Observed for the Cubic, Extended 3D Prussian Blue Analogues (net3me)2mnii5(cn)12and (net2me2)2mnii5(c N)12: A Cation-Adaptive Structure

The reactions of Mn-II(O2CCH3)(2)with NEt(3)Me(+)CN(-)and NEt(2)Me(2)(+)CN(-)form (NEt3Me)(2)Mn-5(II)(CN)(12)(1) and (NEt2Me2)(2)Mn-5(II)(CN)(12)(2), respectively. Structure model-building and Rietveld refinement of high-resolution synchrotron powder diffraction data revealed a cubic [a=24.0093 angstrom (1), 23.8804 angstrom (2)] 3D extended structural motif with adjacent tetrahedral and octahedral Mn(II)sites in a 3:2 ratio. Each tetrahedral Mn(II)site is surrounded by four low-spin octahedral Mn(II)sites, and each octahedral Mn(II)site is surrounded by six high-spin tetrahedral Mn(II)sites; adjacent sites are antiferromagnetically coupled in 3D. Compensation does not occur, and magnetic ordering as a ferrimagnet is observed atT(c)=13 K for2based on the temperature at which remnant magnetization,M-r(T)-> 0. The hysteresis has an unusual constricted shape with inflection points around 50 and 1.2 kOe with a 5 K coercivity of 16 Oe and remnant magnetization,M-r, of 2050 emuOe mol(-1). The unusual structure and stoichiometry are attributed to the very ionic nature of the high-spin N-bonded Mn(II)ion, which enables the maximization of the attractive van der Waals interactions through minimization of void space via a reduced angle MnNC. This results in an additional example of the A(x)Mn(y)(II)(CN)(x+2y)(x=0,y=1;x=1,y=3;x=2,y=1;x=2,y=2;x=2,y=3;x=3,y=5; andx=4,y=1) family of compounds possessing an unprecedented stoichiometry and lattice motif that are cation adaptive structured materials.