Dicopper(II) metallacyclophanes with photoswitchable oligoacene spacers: a joint experimental and computational study on molecular magnetic photoswitches

Abstract

Dinuclear copper(II) complexes of the metallacyclophane-type, (nBu₄N)₄[Cu₂(2,6-anba)₂] (1) and (nBu₄N)₄[Cu₂(1,5-naba)₂]·4H₂O (2) with photoactive 2,6-anthracene-(2,6-anba) and 1,5-naphthalenebis(oxamate) (1,5-naba) bridging ligands, are reported. They undergo a thermally reversible, solid-state photomagnetic (ON/OFF) switching between the moderately strong antiferromagnetically coupled dicopper(II) species and the corresponding magnetically uncoupled [4+4] photocycloaddition product. Density functional calculations give further insights on the intramolecular (“pseudo-bimolecular”) photocycloaddition reaction of the two facing 2,6-anthracene or 1,5-naphthalene spacers in this novel family of dicopper(II) oligoacenophanes. The unique ability of oligoacenes as photoswitchable antiferromagnetic wires between two Cu^II ions separated by relatively long intermetallic distances could be the basis for the development of new kinds of molecular spintronic devices, referred to as molecular magnetic switches.

Keywords:

• Copper
• density functional calculations
• magnetic properties
• oligoacenes
• photochemical reactivity

Acknowledgements

J.P. thanks the ACIISI-Gobierno Autónomo de Canarias (Project NANOMAC) for a postdoctoral contract. W.P.B. acknowledges the financial support from Brazilian agency Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and the Spanish Government through the University of València (Project PHB2012-0290) and the Spanish Government (Project PHB2012-0290). We acknowledge the staff in charge of the BM16-CRG beamline for the assistance and help in structural data collection. We are especially indebted to Dr Donatella Armentano (Università della Calabria) for unselfish help.