Incorporating Paramagnetic (IrCl62-)-Cl-IV in H-Bonded Networks of Metal-Phosphonate Hydrate: Slow Magnetic Relaxation and Proton Conduction

摘要

The large spin-orbital coupling and spatially extended valence orbitals of the Ir-IV (5d(5), S = 1/2 and L = 1) are parameters responsible for its interesting magnetism in addition to the geometrical arrangements in the crystals. In order to study the effect of the Ir center dot center dot center dot Ir distance on the magnetic behavior of (IrCl62-)-Cl-IV species, we made use of diamagnetic supramolecular hosts of (CoCaII)-Ca-III(notpH(x)) [notpH(6) = C9H18N3 (PO3H2)(3)] to accommodate the guest anion of (IrCl62-)-Cl-IV. Controlling the protonation of the acid affects the Co:Ca ratio and the degree of hydration but does not affect its coordination or the geometry to the cobalt center. Consequently, three different salts have been isolated, [(Co2Ca2II)-Ca-III(notpH(2))(2)(H2O)(8)]-((IrCl6)-Cl-IV)center dot 2H(2)O at pH 3.5 (1), [(Co2CaII)-Ca-III(notpH(3))(2) (H2O)(2) ]((IrCl6)-Cl-IV)center dot 4H(2)O at pH 2.5 (2), and [Co-2(III)(notpH(4))(2)]((IrCl6)-Cl-Iv)center dot 6H(2)O at pH 1.7 (3). The distance between the (IrCl62-)-Cl-IV anions varies in the sequence 3 < 1 < 2. Magnetic studies reveal that only 2 exhibits slow magnetic relaxation associated with (IrCl62-)-Cl-IV, which correlates with the large Ir center dot center dot center dot Ir distance (9.428 angstrom) and the absence of a halogen bond between neighboring (IrCl62-)-Cl-IV (Cl center dot center dot center dot Cl > 4.941 A). Furthermore, the different degree of protonation in 1-3 also poses influences on their proton conductivities which increase with the protonation of the phosphonate groups under 95% RH and 25 degrees C.