Molecular Horizons PhD Exit Seminar - Samuel Marlton

The photoproperties of molecules including dyes, sunscreens, fluorescence tags, and photoinitiators are dependent on the interplay of multiple quantum states. The outcomes from this interplay are challenging to predict and especially challenging to control.

To tackle the challenge, this project targets the photostability of isolated molecules using combined ion-mobility, laser photodissociation and mass-spectrometry techniques, in combination with quantum chemical calculations. Ion mobility, photodissociation and mass spectrometry techniques prove to be well suited for assessing the key parameters of internal charge location and assessing their impact.

The effects of charge on photostability are outlined using several systems including protonated nicotine, protonated quinazoline, protonated indazole, protonated benzimidazole and photoinitiators clustered with metal cations. It is revealed that the position of charge (protons or metal cations) shift the energies of electronic quantum states. This is understood as the charge generating an internal orientated electric field. By changing the field strength and orientation, a molecule’s photoproperties can be tuned. This work has set up new experimental protocols for determining and predicting the photostability of molecules in the presence of charge, and provides insight into tuning the properties of photoinitiators for broader applications.