Tailoring molecular functions by O-annulation of polycyclic aromatic hydrocarbons

Considering that the leading cause of degradation is related to aerobic oxidations, the access to disposable smart labels chemo-selectively responding to O2 could be a revolutionary in many field (food packaging, medical products, etc).

It is with this idea in mind that this project will develop O-annulated aromatic hydrocarbons that, through a selective reaction with O2, irreversibly retain an oxidising event and successively communicate it as a colour change under a human input.

To achieve it, we plan to prepare hybrid O-doped chromogenic polycyclic aromatic hydrocarbons that, in the presence of O2 and light, will act as a photosensitiser producing singlet O2. The reactive O2 will react with the chromogenic material itself to give an irreversible change. Integration of this material into an electrochromic display will result in a device that will operate irreversibly after it has been exposed to O2 and reversibly when not exposed to O2.

Background

Building on the know-how developed in Bonifazi’s group about peri-xanthenoxanthene (PXX), we inferred that O-doped molecular graphenes including anthranyl subunits could first sensitise 1O2, and then react with it to give endoperoxide (EPO) species breaking the conjugation.

The idea is to gain control of the synthesis of anthranyl synthons that can be exploited for programming oxo-substituted oligoacenes to be tranformed into a series of regularly O-doped ribbons. Aiming at controlling the 1O2-sensitising properties as well as the reactivity to form EPO, it has been envisaged to synthesised ribbons with different lengths, periphery topology, and doping ratio.

All newly prepared molecules will be thoroughly characterized by means of photophysical and electrochemical (CV, DPV and spectroelectrochemistry) techniques, as well as theoretical modelling.

The self-sensitizing properties of the O-doped PAHs derivatives in the presence of O2 will be tested as well as their electrochromic properties both in solution and in a prototype device. We hope to blend the O-doped PAH derivatives into inert polymeric films and study both the formation of the EPOs and their effect on the electrochromic properties. The idea is to be able to sense O2 level of at least 0.01%, that is considered the standard atmosphere at which a O2-sensitive good should be appropriately packaged

Project aims and methods

This training approach will not only bestow the student with a complete skill-set (see below) but it will generate awareness on the incredible research potential organic chemists can achieve through the O-doping route.

Additional topics included in the training are:
•study of the fundamentals of photophysics and photo/electro-induced processes
•design of photo- and electrochromic molecules and materials
•moulding of the functional materials
•engineering of electrochromic sensing prototypes.

More specific project skills will involve:
•running air-sensitive organic reactions
•purifying and isolating organic reaction products
•compound characterisation; use of 1H and 13C NMR, IR and MS and GC
•atomic Force Microscopy
•HPLC and GPC analysis systems
•scanning Electron Microscopy & Scanning Tunneling Microscopy
•thermal Gravimetric Analysis
•emission and UV-Vis-NIR Spectrophotometer
•cyclic-voltammetry and spectroelectrochemistry
•electrochromic devices
•X-Ray Diffraction
•device engineering.

Start date: 1st October 2019

Supervisor: Professor Davide Bonifazi - https://www.cardiff.ac.uk/people/view/161126-Bonifazi-Davide