Final Activity Report Summary - SWITCHROM (Redox-Switchable Nonlinear Optical Metallochromophores: Towards Functional Materials)
SWITCHROM project aimed to study the nonlinear optical (NLO) properties of thin films of organotransition metal compounds. NLO behaviour is of interest for applications in areas such as optical data processing, and the compounds chosen are designed to show very large effects. The use of a conducting substrate for film deposition was intended to allow us to demonstrate the reversible switching of such effects under electrochemical stimulation. Two new series of organic compounds featuring a long hydrocarbon or fluorocarbon chain were synthesised to give a range of properties. Coordination of these seven ligands with ruthenium(II) provided new complexes which were characterised by various techniques including UV-visible absorption spectroscopy and cyclic voltammetry. These complexes are amphiphilic (surfactant-like), containing hydrophilic and hydrophobic portions that are ideally suited to the controlled formation of organised thin film materials.
Based on film stability considerations, one particular complex was selected and thoroughly investigated. This complex was successfully deposited on both hydrophilic glass slides and transparent conductive indium tin oxide (ITO) slides using a vertical dipping technique known as Langmuir-Blodgett deposition. This technique allowed us to control both the thickness of the film and also the bulk symmetry which is crucial for certain NLO effects such as second harmonic generation (SHG, frequency doubling). NLO measurements carried out using a 1064 nm laser showed a large SHG signal and the dependence of the intensity on the number of layers confirmed that the deposition is homogeneous. Using films on ITO integrated into an electrochemical cell allowed us to demonstrate for the first time a reversible redox-switching of bulk NLO behaviour, thus achieving the stated goal of the project. Future studies will address issues such as the magnitude and durability of the switching effect with a view to potential technological applications.
Based on film stability considerations, one particular complex was selected and thoroughly investigated. This complex was successfully deposited on both hydrophilic glass slides and transparent conductive indium tin oxide (ITO) slides using a vertical dipping technique known as Langmuir-Blodgett deposition. This technique allowed us to control both the thickness of the film and also the bulk symmetry which is crucial for certain NLO effects such as second harmonic generation (SHG, frequency doubling). NLO measurements carried out using a 1064 nm laser showed a large SHG signal and the dependence of the intensity on the number of layers confirmed that the deposition is homogeneous. Using films on ITO integrated into an electrochemical cell allowed us to demonstrate for the first time a reversible redox-switching of bulk NLO behaviour, thus achieving the stated goal of the project. Future studies will address issues such as the magnitude and durability of the switching effect with a view to potential technological applications.