Polyiodides of transition metal trischelate cations: syntheses, structures, and spectral and electrical conductivity studies of [Mn(phen)(3)](I-3)(2)and [Mn(bpy)(3)](I-3)(1.5)(I-8)(0.25)

Two structurally significant polyiodides have been synthesized as salts of manganese(II) trischelates and characterized by three-dimensional X-ray cry stallographic data. The complex, [Mn(phen)(3)](I-3)(2) (1), where phen = 1, 10-phenanthroline, crystallizes in the hexagonal space group R (3) over bar with 6 mononuclear cations in a cell of dimensions, a = b = 16.456(3) Angs trom; c = 25.864(4) Angstrom. The structure has been refined to the final R -1 (wR(2)) values of 0.0365 (0.0782) based on 1981 (F greater than or equal to 4 sigma F) observed independent reflections. The structure of the [Mn(p hen)(3)](2+) cation is unexceptional, whereas there are two types of symmet ric I-3(-) ions with I-I distances of 2.828(1) and 2.912(1) Angstrom. The l onger I-3(-) ions and the trischelate cations form layers of hexagonal netw ork, while the shorter I-3(-) ions are present as linkages between the laye rs in the crystal. The complex, [Mn(bpy)(3)](I-3)(1.5)(I-8)(0.25) (2), wher e bpy = 2,2'-bipyridine, crystallizes in the monoclinic space group C2/c wi th 8 mononuclear cations in a cell of dimensions, a = 29.321(1) Angstrom; b = 12.9177(4) Angstrom; c = 23.2863(8) Angstrom; beta = 120.950(2)degrees. The structure has been refined to the final R-1 (wR(2)) values of 0.0536 (0 .1310) based on 4192 (F greater than or equal to 4 sigma F) observed indepe ndent reflections. The structure consists of [Mn(bpy)(3)](2+) cations, two types of I-3(-) ions, and infinite linear polyiodide chains of the composit ion, (I-8(2-))(n). Powder diffuse reflectance spectra measured for the comp lexes are similar exhibiting features at 23.0, 20.8, 18.5 and 17.2 kK, and are characteristic of the presence of I-3(-) ions. Room temperature magneti c susceptibility measurements gave the magnetic moments of 5.85 and 6.05 mu (B) for 1 and 2, respectively; the values are consistent with the expected spin-only magnetic moment for high-spin d(5) manganese(II) complexes. Singl e crystal EPR spectral measurements with the applied field aligned parallel to the trigonal or pseudo-trigonal symmetry axis of the molecules gave zer o-field splitting (D) values of 0.154 cm(-1) (g = 2.06) and 0.066 cm(-1) (g = 2.03) for 1 and 2, respectively. A comparison of the conductivities of t he complexes in a single crystal form reveals a higher anisotropic conducti vity for 2, which is attributed to the presence of linear polyiodide chains . (C) 1999 Elsevier Science S.A. All rights reserved.