Graphene oxide and reduced graphene oxide hybrids with spin crossover iron(iii) complexes

Abstract

Graphene (rGO) based hybrid materials exhibiting electrical conductivity and spin crossover (SCO) behavior are reported. The non-conductive [Fe(qnal)₂]_nGO (1·GO) and [Fe(qsal)₂]_nGO (2·GO) hybrids have been prepared by employing the electrostatic interaction between the negatively charged graphene oxide (GO) nanosheet and the respective iron(III) complex cations in [Fe(qnal)₂]⁺Cl⁻ and [Fe(qsal)₂]⁺Cl⁻. The conductive [Fe(qnal)₂]_nrGO (1·rGO) and [Fe(qsal)₂]_nrGO (2·rGO) hybrids were obtained by thermal reduction of 1·GO and 2·GO. 1·GO and 1·rGO exhibit SCO behavior, and 1·rGO also shows a light-induced excited spin state trapping (LIESST) effect. Thus, in 1·rGO the electrical conductivity of rGO and the SCO behavior of [Fe(qnal)₂]⁺ coexist in a single structure. We propose that the observed cooperativity for the rGO nanosheet-bound iron(III) [Fe(qnal)₂]⁺ SCO material occurs through formation of large domains via π–π stacking between the graphene skeleton and the [Fe(qnal)₂]⁺ cations.