Chlorine and temperature directed self-assembly of Mg-Ru2(II, III) carbonates and particle size dependent magnetic properties

A series of heterometallic magnesium diruthenium(II,III) carbonates, namely K{Mg(H2O)(6)}(2)[Ru-2(CO3)(4) Cl-2]center dot 4H(2)O (1), K-2[{Mg(H2O)(4)}(2)Ru-2(CO3)(4)(H2O)Cl]Cl-2 center dot 2H(2)O (2), K[Mg(H2O)(5)Ru-2(CO3)(4)]center dot 5H(2)O (3) and K[Mg(H2O)(4)Ru-2(CO3)(4)]center dot H2O (4), were synthesized from the reaction of Ru-2(CO3)(4)(3-) and Mg2+ in aqueous solution. Compound 1 is composed of ionic crystals with the Ru-2(CO3)4Cl(2)(5-): Mg(H2O)(6)(2+) : K+ ratio of 1:2:1. Compound 2 consists of two dimensional layer structures, in which each octahedral environment Mg(H2O)(4)(2+) bonds to two [Ru-2(CO3)(4)(H2O)Cl](4)(-) units in a cis manner forming a neutral square-grid layer {Mg(H2O)(4)Ru-2(CO3)(4)(H2O)Cl}(n). For compound 3, one water molecule of each Mg(H2O)(6)(2+) is substituted by an oxygen atom of Ru-2(CO3)(4)(3-) forming [Mg(H2O)(5)Ru-2(CO3)(4)](-), and then the neighboring Ru-2 dimers are linked together by the rest of the two oxygen atoms of carbonates to form a layer structure {Mg(H2O)(5)Ru-2(CO3)(4)}(n)(n-). In compound 4, the neighboring squared-grid layers {Ru-2(CO3)(4)}(n)(3n)-, similar to those in compound 3, are linked by each octahedral environment Mg(H2O)(4)(2+) in a cis manner forming the three-dimensional network {Mg(H2O)(4)Ru-2(CO3)(4)}(n)(n-). Compound 3 shows ferromagnetic coupling between Ru-2 dimers, and a long-range ordering is observed below 3.8 K. Compound 4 displays a magnetic ordering below 3.5 K, and a systematic study of the size-dependent magnetic properties of compound 4 reveals that the coercivity of 4 has been improved with reduced sample particle size from the micrometer to the nanometer scale.