title: Dramatic variation of magnetic exchange through double end-on azide bridges in a series of ladder-like copper(II) coordination polymers.
abstract: Three ladder-like coordination polymers, [Cu2(phprpy)2-mu-(N3)2(N3)2], 1; [Cu2(terpy)2-mu-(N3)4Cu2-mu-(N3)2(N3)2], 2; and[Cu2(terpy)2-mu-(N3)2(N3)2Cu3-mu-(N3)4(N3)2], 3, consisting of Cu2+ ions with double end-on azide bridges were synthesized, their crystal structures and magnetic properties were determined, and spin dimer analysis was performed to explain the signs and strengths of their strong spin exchange interactions [phprpy is 4-(3-phenylpropyl)pyridine and terpy is 2,2':6,2''-terpyridine]. Although these compounds have ladder-like arrangements of Cu2+ ions, their magnetic structures are described as isolated dimers for 1 and 2 and as isolated trimers for 3. The predominant spin exchange paths in 1-3 have double end-on azide bridges linking adjacent Cu2+ ions, and the geometrical parameters of these bridging structures are similar. However, the spin dimer of 1 exhibits a strong ferromagnetic coupling; that of 2, a strong antiferromagnetic coupling; and that of 3, a weak ferromagnetic coupling. These findings are well explained by the present spin dimer analysis and show that the nature and geometry of the nonbridging ligands can have a strong influence on the sign and strength of the spin exchange interaction between Cu2+ ions connected by double end-on azide bridges.
authors.affiliation: Department of Chemistry, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Woodward
authors.forename: Rénal V
authors.initials: RV
authors.lastname: Backov
authors.forename: Khalil A
authors.initials: KA
authors.lastname: Abboud
authors.forename: D
authors.initials: D
authors.lastname: Dai
authors.forename: H-J
authors.initials: HJ
authors.lastname: Koo
authors.forename: M-H
authors.initials: MH
authors.lastname: Whangbo
authors.forename: Mark W
authors.initials: MW
authors.lastname: Meisel
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Talham