Structure, ferromagnetic ordering, anisotropy, and spin reorientation for the two-dimensional cyano-bridged bimetallic compound K2Mn3(H2O)(6)[Mo(CN)(7)](2)center dot 6H(2)O

The title compound, K2Mn3(H2O)6 [Mo(CN)(7)](2) . 6H(2)O, has been synthesiz ed by slow diffusion of aqueous solutions saturated in KNO3 and containing K-4[Mo(CN)(7)]. 2H(2)O and [Mn(H2O)(6)](NO3)(2), respectively. The compound crystallizes in the monoclinic system, space group C2. The Mo site is surr ounded by six -C-N-Mn linkages and one terminal cyano group in a strongly d istorted pentagonal bipyramid fashion. There are two distorted octahedral M n sites, both with four -N-C-Mo linkages and two water molecules in trans c onformation. The structure is two-dimensional with anionic layers perpendic ular to the a axis and K+ ions located between the layers. Each layer is co nstituted of two parallel gridlike sheets made of edge-sharing Mo2Mn2 lozen ge motifs, connected by Mn(CN)(4)(H2O)(2) units situated between the sheets . Thorough magnetic investigations have been carried out. First, it has bee n demonstrated that the magnetic axes are collinear with the a, b, and c* c rystallographic directions. The temperature and field dependences of the ma gnetization in both the de and ac modes have been measured along the princi pal axes. The angular dependence of the magnetization in the bc* plane as a function of the external field has also been measured. These investigation s have revealed that the compound orders ferromagnetically at T-c= 39 K, wi th a small hysteresis effect along the c* axis. Furthermore, a field-induce d spin reoffentation has been detected. The b axis is the easy magnetizatio n axis in low field, and the bc* plane is very anisotropic. When the field reaches a critical value, the bc* plane becomes almost isotropic. From the magnetic data, the magnetic phase diagram has been determined. When a singl e crystal of K2Mn3(H2O)(6)[Mo(CN)(7)](2). 6H(2)O is partially dehydrated un der vacuum, its shape remains unchanged, but T-c is shifted up to 72 K, and the spin reorientation is suppressed. The partially dehydrated material pr esents a coercive field of 1.3 kOe along b at 5 K. These findings have been compared to those reported recently for a three-dimensional material of th e same family (the alpha-phase Mn-2(H2O)(5)-Mo(CN)(7) . 4H(2)O).