Toward a (bis)Trifluoromethyl-Substituted Quinazolinespirohexadienone(QSHD) Photochrome for Gating PICT
Dr. Jason Gillmore
In order to gate photoinduced charge transfer (PICT), photochromes need to be able to undergo an isomerization from a short wavelength (SW) form to a long wavelength (LW) form when exposed to UV light, and only revert back thermally. Gating of PICT is accomplished when the LW form has increased conjugation so that it can accept an electron more easily than the SW form. Synthetic steps have been taken to make the LW form more reducible while keeping the ground state reduction potential (Eºred) of the SW relatively unchanged. One of these steps has been the synthesis of a trifluoromethyl-substituted derivative of the QSHDs in which the electron withdrawing properties of the trifluoromethyl groups make the LW form more reducible. Due to the electron withdrawing effects of the trifluoromethyl groups, synthesis of the desired photochrome cannot be accomplished in the same way as past QSHDs. An improved method has been implemented using aryl iodides and bromides. Predicted reduction potentials of the target photochrome, synthesis using the halides thus far, and possible synthetic routes toward replacing the halides with trifluoromethyl groups are presented.
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