MNGAPO-2 - SYNTHESIS AND CHARACTERIZATION OF [MNGA(PO3OH)(2)(PO4)][C6N2H14], A NEW MICROPOROUS MANGANESE-GALLIUM PHOSPHATE

A new open-framework manganese-gallium phosphate has been synthesized under solvothermal conditions and characterized by. single-crystal XRD , thermogravimetric analysis, and magnetic susceptibility measurements [crystal data: [MnGa(PO3OH)(2)(PO4)][C6N2H14], M-r = 525.76. monoclin ic, space group P2(1)/n (No. 14), a 10.193(1), b = 14.276(1), and c = 10.380 (1) Angstrom, beta = 91.184(8)degrees, V = 1510 Angstrom(3), Z = 4, R = 5.8%, R-w = 7.8% (2331 observed data with I > 3 sigma(I))]. T he structure consists of MnO5, GaO4, and PO4 units linked to form a th ree-dimensional microporous framework encapsulating 1,4-diazabicyclo[2 .2.2]octane cations. The Mn2+ ions have distorted square-pyramidal geo metry and exist in Mn-2(HPO4)(4) units within the framework. Antiferro magnetic ordering at T-N = 10(1)K is ascribed to coupling between Mn2 ions in these subunits, and the temperature dependence of the suscept ibility can be successfully fitted assuming a Heisenberg exchange inte raction (J = -2.07(1) cm(-1), g = 2.25(1)). At higher temperatures (>7 0 K) Curie-Weiss paramagnetism is observed (theta = -20.2(2) K, mu(eff ) = 6.69(1)mu(B)).