Thermal and optical control of electronic states in a single layer of switchable paramagnetic molecules

The control of the charge distribution in a monolayer of switchable cobalt–dioxolene complexes undergoing Valence Tautomerism (VT) has been achieved by means of thermal and optical stimuli. Thiol-derivatised VT molecules have been grafted on polycrystalline gold surface as monolayers from solution. X-ray photoelectron spectroscopy and time-of-flight secondary ions mass spectrometry evidenced the formation of a covalent bond between intact VT molecules and the surface and excluded the presence of physisorbed molecules. X-ray absorption spectroscopy revealed that the temperature- and light-induced conversion profiles of the monolayer closely reproduce the ones found for the crystalline phase. This study demonstrates that a wet chemistry based approach allows to transfer switchable paramagnetic molecules at the nanoscale, widening the playground to develop new hybrid molecular based architectures for novel technologies.