/ Chemistry Department

Gillmore Research Group

Students have the opportunity to join a thriving externally funded organic photochemistry research group at Hope College, with a primary focus on incorporating undergraduate students into all aspects of the research endeavor.

Organic Photochemistry For Materials Applications

Teaching Old Photochromes New Tricks

Student collaborators gain familiarity with organic synthesis, photochemistry, electrochemistry, reactive (radical and ion radical) intermediates, polymers and materials research. Together, we develop syntheses of novel organic photochromes which we apply to a range of different applications based on more than just their changing colors.

Photochromic organic molecules are compounds that undergo a reversible photochemical rearrangement from a short wavelength (SW) form to a long wavelength (LW) form, with reversion occurring thermally, photochemically or both. The vast majority of organic photochromes have been investigated for applications in ophthalmic lenses (e.g., Transitions® lenses), novelty items or data storage applications all related to their color change. Studies of the spectral changes, molar absorptivity, reversibility and fatigue resistance predominate. Exploration of other dynamic properties of photochromic compounds has been far more limited. In the Gillmore Research Group at Hope College, we attempt to make use of the changes in shape and electronics that accompany the color change of a photochrome.

Photochromes from the perimidinespirocyclohexadienone family are being prepared and studied as potential "photochromic photooxidants", where the electronic changes between SW and LW affect the ability of these dyes to initiate electron transfer reactions. This can add an additional level of gating, or control, to photoinduced electron transfer processes that can be applicable to either microfabrication or photoresponsive plastics for data storage or optical waveguiding applications. Students are synthesizing known and novel compounds in this family of compounds. Students also do all the characterization of structure, photophysical properties, and ground and excited state electrochemical properties, using NMR, UV-Vis, Cyclic Voltammetry and other techniques.

The Gillmore Group is also investigating a newly reported family of BF2-coordinated azo dyes, primarily for their change in shape, rather than color. These dyes absorb at significantly longer wavelengths than conventional azo dyes. The Gillmore group is working to install synthetic handles on these dyes which others have developed, so that, together with the group of Professor Matthew Smith in the Hope College Department of Engineering, we might incorporate them into polymeric materials. In polymer networks, if properly ordered, it is possible to couple the molecular shape change of an azo dye to bulk shape change of the material. These are known as photomechanical materials (PMMs), which expand, contract, or bend in response to light. PMMs have applicability to a variety of wireless actuators. Moving from the UV to blue-green absorbance of conventional azo dyes to the red or even near-infrared absorbance of these BF2-coordinated azo dyes will make PMMs more relevant to biological applications while decreasing competitive absorption by other device components and minimizing photodegradation of materials. Students on this project make, purify and characterize a range of dyes, monomers and model compounds, as well as ultimately polymers. We study the photochromic and eventually the photomechanical properties of the dye monomers and polymers.

Finally, the Gillmore group also applies computational modeling to help us understand the systems we study. For instance, we have developed methods to allow accurate and efficient prediction of redox properties to guide us to the most promising next generation targets in our photochromic photooxidants project.