The synthesis, crystal structure, and physical characterization of the coordination compounds [Ni(en)(2)](4)[Fe-(CN)(5)NO](2)[Fe(CN)6]. 5H(2)O (1), [Ni(en)(2)][Fe(CN)(5)NO]. 3H(2)O (2), [Mn(3-MeOsalen)(H2O)](2)[Fe(CN)(5)NO] (3), and [Mn(5-Brsalen)](2)[Fe(CN)(5)NO] (4) are presented. 1 crystallizes in the monoclinic space group P2(1)/n (a = 7.407-(4) Angstrom, b = 28.963(6) Angstrom, c = 14.744(5) Angstrom, alpha = 90 degrees, beta = 103.26(4)degrees, gamma = 90 degrees. Z = 2). Its structure consists of branched linear chains formed by cis-[Ni(en)(2)](2+) cations and ferrocyanide and nitroprusside anions. The presence of two kinds of iron(II) sites has been demonstrated by Mossbauer spectroscopy. 2 crystallizes in the monoclinic space group P2(1)/c (a = 11.076(3) Angstrom, b = 10.983(2) Angstrom, c = 17.018(5) Angstrom, alpha = 90 degrees, beta = 107.25(2)degrees, gamma = 90 degrees, Z = 4). Its structure consists of zigzag chains formed by an alternated array of cis-[Ni(en)(2)](2+) cations and nitroprusside anions. 3 crystallizes in the triclinic space group P (1) over bar (a = 8.896(5) Angstrom, b = 10.430(5) Angstrom, c = 12.699(5) Angstrom, alpha= 71.110(5)degrees beta = 79.990(5)degrees gamma = 89.470(5)degrees, Z = 1). Its structure comprises neutral trinuclear bimetallic complexes in which a central [Fe(CN)(5)NO](2-) anion is linked to two [Mn(3-MeOsalen)](+) cations. 4 crystallizes in the tetragonal space group P4/ncc (a = 13.630(5) Angstrom, c = 21.420(8) Angstrom, Z = 4). Its structure shows an extended 2D neutral network formed by cyclic octameric [-Mn-NC-Fe-CN-](4) units. The magnetic properties of these compounds indicate the presence of quasi-isolated paramagnetic Ni2+ and Mn3+. Irradiated samples of the four compounds have been studied by differential scanning calorimetry to detect the existence of the long-lived metastable states of nitroprusside.