Syntheses, structures and magnetic properties of mono- and di-manganese inclusion compounds

Mono- and di-manganese inclusion compounds 1 and 2 are reported. Two mono-manganese molecules Mn(bpy)2(NO3)2 (bpy=2,2′-bipyridine) and [Mn(bpy)2(NO3)(H2O)]·NO3 coexist in the mole ratio of 1:1 in the structure of 1, while two di-manganese molecules [Mn2O(bpy)2(phtha)2(H2O)2]·(NO3)2 (phtha=phthalate) and [Mn2O(bpy)2(phtha)2(NO3)(H2O)]·NO3 in the structure of 2. Refluxing Mn(NO3)2/bpy/phthalic acid reaction mixtures in CH3CN leads to the isolation of 1, further concentration of the reaction solution in raising temperature results in 2. The Mn1 and Mn2 units in the inclusion compounds 1 and 2 are similar to other reported Mn1 and Mn2 analogs, respectively. The Jahn–Teller distortion was observed to give rise to the elongation along the OterminalMnOcarboxyl axes for all the four Mn(III) sites in 2, leading to unexpected longer Mn(III)Oaqua than Mn(II)Oaqua in 1. Extensive hydrogen bonding interactions among H2O, NO3 − and COOH were observed in the two inclusion compounds. Cyclic voltammetry of 2 in DMF displays two quasi-reversible redox couples at +0.10/+0.22 and −0.43/−0.36 V assigned to the Mn(III)Mn(IV)/2Mn(III) and 2Mn(III)/Mn(III)Mn(II), respectively. Variable temperature magnetic susceptibilities of 1 and 2 were measured. The data were fit to a model including axial zero-field splitting term and a good fit was found with D=1.77 cm−1, g=1.98 and F=1.48×10−5 for 1. For 2, the least-squares fitting of the experimental data led to J=2.37 cm−1, g=2.02 and D=0.75 cm−1 with R=1.45×10−3.