Synthesis of Supramolecular Assemblies Based on Donor-Acceptor Interactions and Study of Long-Range Electron Transfer
Tethered molecules consisting of two or more electron-donor groups of graded donor strength and steric crowding allows selective electron donor acceptor (EDA) complexation on the site of the non-hindered HMB donor, as confirmed by the spectral analysis and X-ray crystallography of the EDA crystals, i.e.
Upon laser excitation of the EDA complex, the cation radical of the hydroquinone ether is observed within a few picoseconds. Since charge-transfer excitation must first generate the HMB cation radical, the spectroscopic data point to an ultrafast intramolecular electron transfer (kINTRA) from the electron-rich hydroquinone ether to the relatively electron-poor cation radical (HMB+o), which leads to separation of the positive hole and the negative charge:
Similarly, the steric hindrance and other weak molecular forces are constantly exploited in my group to construct novel supramolecular assemblies for the preparation of molecular materials for practical usage.
We are actively pursuing the highly reversible and rapid C-C bond formation and breakage in tetraphenylene derivatives and related molecules (which is accompanied by dramatic color changes) for the construction of novel molecular devices that can be switched on and off by external stimuli (such as heat, light, electrical field, or change in pH). Ultimately, the easy fabrication of organic molecules and the high degree of synthetic flexibility in these functioning molecular devices will allow their ready modification and eventual incorporation into polymers and thin films for practical usage.