Variations in topology and magnetic properties of hepta- and octacyanometallates of molybdenum with manganese(II).

Treatment of [Mn(dpop)(H2O)2]Cl2 (dpop = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo-[12.3.1]octadeca-1(18),2,12,14,16-pentaene) with K4[Mo(CN)7]·2H2O under varied synthetic conditions afforded four different compounds: {[Mn(dpop)]4[(dpop)Mn(H2O)]2[Mo(III)(CN)7]3·27H2O}n (1), {[(dpop)Mn(H2O)][Mo(III)(CN)7][Mn(dpop)]3[Mo(IV)(CN)8]·29H2O}n (2), {[(dpop)Mn(H2O)]2[Mo(IV)(CN)8]2[Mn(dpop)]4[Mo(III)(CN)7]·12H2O}n (3), and [(dpop)Mn(H2O)]2[Mo(IV)(CN)8]·9H2O (4). Compound 1 contains only [Mo(III)(CN)7](4-) anions and exhibits a corrugated two-dimensional layered architecture. The structure of 2 with a 1 : 1 ratio of Mo(III) : Mo(IV) is best described as a ladder-like chain composed of [Mo(III)(CN)7](4-)-based pentanuclear [Mo(III)Mn(II)4] fragments which are further linked by in situ produced [Mo(IV)(CN)8](4-) anions. In the case of 3, [Mn8Mo8] rings containing bent [Mo(III)Mn(II)2] fragments are extended into a two-dimensional layer with the ratio of [Mo(CN)7](4-) : [Mo(CN)8](4-) being 1 : 2. Compound 4 exhibits a bent trinuclear structure in which two CN(-) groups of [Mo(CN)8](4-) function as μ2-bridges to [Mn(dpop)(H2O)](2+) fragments. Magnetic studies suggest significant antiferromagnetic coupling interactions occur between Mo(III) and Mn(II) ions while, not surprisingly, interactions between the Mn(ii) ions through diamagnetic [Mo(IV)(CN)8](4-) anions are negligible. Compound 1 exhibits ferrimagnetic ordering below 3.0 K whereas 2 shows the signature of single molecule magnet behavior with slow relaxation of the magnetization and an effective energy barrier (U(eff)) of 8.1 K.