Two Gd^(Ⅲ) Fe^(Ⅲ)4 metallacrown complexes are presented and analyzed for their magnetic properties.One of these species is newly identified and exhibits a bent ring geometry as opposed to the more conventional flatt...Two Gd^(Ⅲ) Fe^(Ⅲ)4 metallacrown complexes are presented and analyzed for their magnetic properties.One of these species is newly identified and exhibits a bent ring geometry as opposed to the more conventional flatter conformation of the other.Both complexes are quite similar magnetically,exhibiting antiferromagnetic exchange coupling values ca.J(Fe^(Ⅲ)-N-O-Fe^(Ⅲ))=-7 cm^(-1) and J(Gd^(Ⅲ)-O-Fe^(Ⅲ))=-0.7 cm^(-1).When analyzed for the molecular magnetocaloric effect,maximum -ΔS_(m) values of 7.3 J K^(-1) kg^(-1) at 3 K and at 6.1 J K^(-1) kg^(-1) at 4 K were exhibited.A detailed structural-magnetic correlation is established and an assessment of several similar magnetic metallacrowns with diverse metal combinations is given with regards to their potential magnetocaloric properties.Strategies for improving the magnetocaloric properties within the Metaln+Fe^(Ⅲ)4 family of metallacrowns are proposed regarding the ratio between coupling parameters J(Fe^(Ⅲ)-N-O-Fe^(Ⅲ))/J(Metal^(n+)-O-Fe^(Ⅲ)).展开更多
基金supported by the National Science Foundation(NSF)under the grants CHE-1664964(V.L.P.)CHE-0840456 for X-ray instrumentation+1 种基金the Rackham Graduate School for international travel fundingNSF grant DGE-1256260.
文摘Two Gd^(Ⅲ) Fe^(Ⅲ)4 metallacrown complexes are presented and analyzed for their magnetic properties.One of these species is newly identified and exhibits a bent ring geometry as opposed to the more conventional flatter conformation of the other.Both complexes are quite similar magnetically,exhibiting antiferromagnetic exchange coupling values ca.J(Fe^(Ⅲ)-N-O-Fe^(Ⅲ))=-7 cm^(-1) and J(Gd^(Ⅲ)-O-Fe^(Ⅲ))=-0.7 cm^(-1).When analyzed for the molecular magnetocaloric effect,maximum -ΔS_(m) values of 7.3 J K^(-1) kg^(-1) at 3 K and at 6.1 J K^(-1) kg^(-1) at 4 K were exhibited.A detailed structural-magnetic correlation is established and an assessment of several similar magnetic metallacrowns with diverse metal combinations is given with regards to their potential magnetocaloric properties.Strategies for improving the magnetocaloric properties within the Metaln+Fe^(Ⅲ)4 family of metallacrowns are proposed regarding the ratio between coupling parameters J(Fe^(Ⅲ)-N-O-Fe^(Ⅲ))/J(Metal^(n+)-O-Fe^(Ⅲ)).
