Spectroscopic investigation of Ruthenium complexes combined to naphthalimides: solvatochromism, luminescence and pi-stacking

Abstract

The present project proposes to synthesize, characterize and study the properties of new luminescent compounds of general formula [Ru(bpy)2(NI)2](PF6)2, which feature the family of substituted ligands naphthylamide (NI), such as N-pyridyl-1.8-naphthalimides (NI-L), 4-amino-N-pyridyl-1.8-naphthalimides (NI-NH2) and 4-nitro-N-pyridyl-1.8-naphthalimides (NI-NO2). These ligands are expected to tune the emission intensity and color of the compounds, and also the original t1/2 of the excited states of the complexes, through the introduction of the nitro substituents (electron-withdrawing effect) and amino (electron-donating effect).The interest in this study is based on the individual properties of each chromophore, R-NI and [Ru(bpy)2X2]: both are luminescent, and the NI ligands should act as "antennas" ligands, which absorb higher energy wavelengths and cause further sensitizing of the states of charge transfer, which is centered in the metal. Both feature solvatochromism and at least tree redox processes: two centered on the R-NI ligand and one in the Ru (II) ion, which also carry chromatic changes. Therefore, new properties should arise in the new complexes due to mutual disturbance caused by the building units.Both the ligand (NI) and the complex [Ru(bpy)2(NI)2](PF6)2 were synthesized based on adaptations of previously developed procedures in scientific initiation funded by FAPESP (process no. 2018/01419-9). As for the characterization, the chosen techniques will be NMR spectroscopy; absorption in the UV-visible and infrared; luminescence; mass spectrometry; elemental analysis and cyclic voltammetry. It is also worth mentioning the possibility of arrangement by pi-stacking of NI ligands in solution on polar solvents. The project also intends to explore this aspect which refers to Supramolecular Chemistry. (AU)