Independent Switching of Cubic Nonlinear Optical Properties in a Ruthenium Alkynyl Cruciform Complex by Employing Protic and Electrochemical Stimuli

摘要

Materials with optimized nonlinear optical (NLO) properties are required for various applications, including processing of optical signals, optical data storage, nanophotonics, and biophotonics. There has been significant recent interest in the reversible switching or modulation of NLO properties. Specific procedures that have been employed to switch NLO properties include protonation/ deprotonation, oxidation/reduction, and photoisomerization sequences, almost all reports considering two "states" only and providing data for a single wavelength only. Very recently, quadratic and cubic NLO properties have been switched between three distinct states for the first time. We have previously shown that the NLO properties of ruthenium alkynyl complexes can be conveniently switched electrochemically via the reversible M~(Ⅱ/Ⅲ) couples. We report herein synthesis of a quadrupolar ruthenium alkynyl cruciform complex, its reversible conversion to tetravinylidene complex or tetraruthenium(Ⅲ) tetracationic complex forms by protonation or oxidation, linear and nonlinear proto- and electrochromism studies that reveal switching of NLO properties, cubic NLO wavelength-dependence studies for the alkynyl complex, its tetracation, and the vinylidene complex, and theoretical studies that shed light on the optical behavior.