Magnetic properties of coordination clusters with {Mn₄} and {Co₄} antiferromagnetic cores

Abstract

We present a joint experimental and theoretical characterization of the magnetic properties of coordination clusters with an antiferromagnetic core of four magnetic ions. Two different compounds are analyzed, with Co...

Independent and coherent transitions between antiferromagnetic states of few-molecule systems

“…Two of the four ions reside in an approximately octahedral ligand field and two in an approximately trigonal bipyramidal ligand field with a spin S = 5 2 (S = 3 2 ) for Mn II (Co II ). The ground state is AFM, as supported by magnetization measurements for the pristine molecules as well as for molecules grafted to CNTs [29][30][31]. Density functional theory (DFT) calculations of the isolated complexes [30] also yield an S z tot = 0 ground state, confirming the overall AFM nature of the intramolecular magnetic interactions in the simpler one-electron approximation.…”

“…The ground state is AFM, as supported by magnetization measurements for the pristine molecules as well as for molecules grafted to CNTs [29][30][31]. Density functional theory (DFT) calculations of the isolated complexes [30] also yield an S z tot = 0 ground state, confirming the overall AFM nature of the intramolecular magnetic interactions in the simpler one-electron approximation. The complexes retain their AFM nature when grafted covalently to the CNT [Figs.…”

“…To fabricate a system that exhibits distinct molecular S tot = 0 states, we use charge-neutral molecular [M 4 L 2 (OAc) 4 ] complexes [29,30] (H 2 L = 2,6-bis-[1-(2hydroxyphenyl)iminoethyl]-pyridine; HOAc = acetic acid; M = Mn II or Co II ). Those complexes (hereafter denoted as {Mn 4 } and {Co 4 }) are nearly isostructural and display a quasitetrahedral core of divalent metal ions interlinked by ligands [Fig.…”

“…The nanotubes were oxidized in air at 450°C, and then the field-effect-transistor structure of the quantum-dot device was fabricated using the substrate as a back gate and Pt leads ({Mn 4 }-based devices), or the device was fabricated and then the nanotubes oxidized ({Co 4 }-based devices). Here, [M 4 L 2 (OAc) 4 ] complexes (H 2 L = 2,6-bis-[1-(2-hydroxyphenyl)iminoethyl]pyridine, {Mn 4 } and {Co 4 }) were synthesized according to the literature [29,30] and bonded to the nanotubes by introducing the device into a solution of the complex (in acetonitrile solution for {Mn 4 }, in dichloromethane for {Co 4 }) for a week before rinsing away the noncovalently attached complexes over another week. A density of functionalization of ∼1 molecule/10 nm was achieved [31].…”