Description of the dataset: Origin of the data: Experimental spectroscopic measurements Data Type: experimental measurements, open access supporting information The data are in CSV, XLSX and FBSW. Supporting information are supplied in PDF format. Data generated by instruments: Varian Cary 5000 UV-Vis-NIR spectrophotometer for UV-Vis measurements, Varian Cary Eclipse fluorescence spectrophotomer for fluorescence quenching measurements. Analytical and procedural information: Stern-Volmer fluorescence quenching experiments and UV-Vis measurements. Definition of variables: Wavelength, Absorbance, Concentration Units of measurement: nanometers (nm), moles-per-litre (mol/l) Abbreviations: File names and data headers use the following abbreviations: SVQuench refers to Stern-Volmer quenching experiments MesAcrMe xx refers to data related to the catalyst 9-mesityl-10-methylacridinium. Xx is the amount of catalyst in mol/l (10-4 should be intended as 0.1 mmol/l and so on). EtAn xx refer to measurements related to 8-ethylanisol. Xx is the amount of quencher in mol/l as above. BenzAc xx refer to measurements related to benzoic acid. Xx is the amount of quencher in mol/l as above. Pyrz xx refer to measurements related to pyrazole. Xx is the amount of quencher in mol/l as above.

FBSW data is used by the proprietary software of the Varian spectrometers (CARY WinUV and Cary Eclipse). Information can be found at https://www.agilent.com/en/product/molecular-spectroscopy/uv-vis-uv-vis-nir-spectroscopy/uv-vis-uv-vis-nir-software/cary-winuv-software and https://www.agilent.com/en/product/molecular-spectroscopy/fluorescence-spectroscopy/fluorescence-software/cary-eclipse-software