The treatment of Mn3O(O2CPh)6(py)2(H2O) with 2,2'-biphenol (biphenH2) and NEt3 in MeCN leads to formation of (NEt3H)2[Mn(biphen)2(biphenH)] (2). Complex 2 crystallizes in monoclinic space group P2(1)/c with (at -146-degrees-C) a = 22.830 (15) angstrom, b = 9.982 (6) angstrom, c = 19.268 (16) angstrom, beta = 108.27 (3)-degrees, Z = 4 and V = 4169.39 angstrom3. The structure was solved by direct methods and refined to R (R(W)) of 6.67% (6.14%) by using 1620 unique reflections with F > 2.33-sigma(F). The structure of the anion consists of a five-coordinate, trigonal-bipyramidal Mn(III) center ligated by two chelating biphen groups and a monodentate biphenH, the second phenoxide oxygen being protonated and not ligated to the Mn. A similar reaction system using 3,3',5,5'-tetrabromobiphenol leads to the product (NEt3H)2[Mn(Br4biphen)2(O2CPh)] (3) whose IR spectrum suggests its structure to be similar to 2 with a chelating (eta-2) benzoate replacing the monodentate biphenH group. Treatment of complex 2 with 2,2'-bipyridine (bpy) in CH2Cl2 yields a black solution: layering with hexanes and storage at -20-degrees-C leads to crystallization of Mn2(biphen)2(biphenH)(bpy)2 (4) whereas storage at room temperature leads to crystallization of (bpyH)[Mn(biphen)2(bpy)] (5). Complex 4 crystallizes in monoclinic space group P2(1)/c with (at -155-degrees-C) a = 13.373 (5) angstrom, b = 10.508 (4) angstrom, c = 39.005 (22) angstrom, beta = 90.67 (2)-degrees, Z = 4, and V = 5480.59 angstrom3. The structure was solved by direct methods and refined to R (R(W)) of 7.19% (6.83%) by using 2607 unique reflections with F > 2.33-sigma(F). The complex is mixed-valence (Mn(II), Mn(III)), and the structure consists of two Mn atoms bridged by two oxygen atoms from two biphen groups, the other oxygen atoms of which are terminally ligated to the Mn(III) center. Six-coordination of the latter is completed by a chelating bpy. The Mn(II) has a chelating bpy, and five-coordination is completed by a monodentate biphenH, the second oxygen of which is protonated as in 2. The Mn(II) and Mn(III) coordination geometries are distorted square-pyramidal and octahedral, respectively. The structure of complex 5 is assumed to be a six-coordinate, distorted octahedral monomer. Variable-temperature solid-state magnetic susceptibility studies on complex 4 at 10.0 kG are reported; the effective magnetic moment, mu-eff/Mn2, steadily increases from 7.12-mu-B at 302.4 K to a maximum of 8.31-mu-B at 8.00 K, and then decreases slightly to 8.24-mu-B at 5.00 K, consistent with an intramolecular ferromagnetic exchange interaction. Complex 4 is the first Mn(II)Mn(III) complex to exhibit a ferromagnetic interaction. In order to characterize fully the ferromagnetic coupling in this complex, magnetic susceptibility data were collected in the low-temperature range (approximately 2-15 K) at fields of 10.0, 24.5, 34.1, and 43.5 kG. All data, including that at high temperatures, were least-squares fit with a full-matrix (30 x 30) diagonalization approach. Isotropic Zeeman interactions and magnetic exchange interactions, as well as axial zero-field splitting for the Mn(II) (D1S(z1)2) and Mn(III) (D2S(z2)2) ions, were included as matrix elements. All data were handled well by parameters of J = +0.86 cm-1, g = 1.83, D1 = 1.0 cm-1, and D2 = -1.6 cm-1. The ground state at zero field is the m(s) = -5/2 component of the S = -9/2 state. In the approximately 5-23-kG region, the m(s) = -7/2 component becomes the ground state, and finally above approximately 23 kG, the m(s) = -9/2 component crosses over to become the ground state. This is confirmed by the saturation of the magnetization at 1.78 K and 43.5 kG. EPR spectra were recorded at 8-60 K for powdered solid samples and a CH2Cl2/toluene frozen solution. The spectra exhibit two main features at g almost-equal-to 2 and g almost-equal-to 5 and show little variation over the temperature range explored. The g almost-equal-to 5 feature shows resolved manganese hyperfine structure in the frozen-solution spectrum.
