Next Generation Perimidinespirohexadienone Derivatives
Dr. Jason Gillmore, Hope College
Creating electron deficient perimidinespirohexadienone (PSHD) photochromes to “gate” sensitivity toward photoinduced charge transfer (PICT) reactions is the primary focus of the Gillmore group. Previous modification has included the replacement of the of the naphthalene moiety in the PSHDs with a quinoline, resulting in quinazolinespirohexadienones (QSHDs). In the present work, oxazinoquinolinespirohexadienones (OSHDs), QSHD analogs in which a bridging nitrogen atom is replaced with an oxygen, have been prepared and studied. Our computational methods would have predicted these to be more potent photooxidants. Unfortunately NMR, UV-vis, and X-ray analyses indicate these analogs are not photochromes but rather exist exclusively in the open, long wavelength (LW) form. Two tautomeric structures of this LW isomer are possible. Contradictory NMR and cyclic voltammetry evidence for the structure in solution will be presented and compared with X-ray diffraction data on the crystalline solid state structure. We have also begun to analyze the structures of compounds with similar tautomeric possibilities, prepared as synthetic intermediates en route to this product in an attempt to understand the observed lack of photochromism. In a second new direction, we have begun to attempt to prepare analogs of our QSHDs (and potentially OSHDs) in which the quinoline nitrogen is alkylated to form quinolinium salts. These are predicted to be potent photooxidants. But in addition to studying these alkylated photochromes for gating sensitivity to PICT, we are interested in studying these molecules' ability to perhaps gate DNA intercalation. This may occur as quinoliniums are potent intercalators, and there is a decrease in steric bulk near the quinolinium when the central perpendicular spirocyclic dienone moiety in the SW isomerizes to a more planar and offset quinonimine moiety in the LW upon photochromic rearrangement.
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