Chlorine and temperature directed self-assembly of Mg–Ru2(ii,iii) carbonates and particle size dependent magnetic properties†
Abstract
A series of heterometallic magnesium diruthenium(II,III) carbonates, namely K{Mg(H2O)6}2[Ru2(CO3)4Cl2]·4H2O (1), K2[{Mg(H2O)4}2Ru2(CO3)4(H2O)Cl]Cl2·2H2O (2), K[Mg(H2O)5Ru2(CO3)4]·5H2O (3) and K[Mg(H2O)4Ru2(CO3)4]·H2O (4), were synthesized from the reaction of Ru2(CO3)43− and Mg2+ in aqueous solution. Compound 1 is composed of ionic crystals with the Ru2(CO3)4Cl25− : Mg(H2O)62+ : K+ ratio of 1 : 2 : 1. Compound 2 consists of two dimensional layer structures, in which each octahedral environment Mg(H2O)42+ bonds to two [Ru2(CO3)4(H2O)Cl]4− units in a cis manner forming a neutral square-grid layer {Mg(H2O)4Ru2(CO3)4(H2O)Cl}n. For compound 3, one water molecule of each Mg(H2O)62+ is substituted by an oxygen atom of Ru2(CO3)43− forming [Mg(H2O)5Ru2(CO3)4]−, and then the neighboring Ru2 dimers are linked together by the rest of the two oxygen atoms of carbonates to form a layer structure {Mg(H2O)5Ru2(CO3)4}nn−. In compound 4, the neighboring squared-grid layers {Ru2(CO3)4}n3n−, similar to those in compound 3, are linked by each octahedral environment Mg(H2O)42+ in a cis manner forming the three-dimensional network {Mg(H2O)4Ru2(CO3)4}nn−. Compound 3 shows ferromagnetic coupling between Ru2 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.