Redox-switchable Cyclophanes for Handling Aromatic Compounds and metal Complexes

Title:

Redox-switchable Cyclophanes for Handling Aromatic Compounds and metal Complexes

Schedule:

Date: 11^th December, 2023 (Monday)

Time:  4 - 5 pm (HKT)

Venue: Lecture Theatre P1, Chong Yuet Ming Chemistry Building

Speaker:

Dr. Chaoyi YAO

Department of Organic and Polymer Chemistry

School of Chemistry and Chemical Engineering

Northeastern University

Abstract:

Classical cyclophane hosts are equipped with a redox-switching function by providing alcohol-ketone interconversion sites. With this principle, cyclophanes have been designed and synthesized. Controlling the hybridization state (sp2 or sp3) of key carbon atoms in the macrocycle in this way permits the erection or collapse of adjacent phenylene walls. The macrocycle cavity can become a relatively large and deep hydrophobic space or it can become a shrunken and shallow one. Shape complementary aromatic guests are therefore captured within the former in water whereas they are released from the latter.

Recognizing that classical cyclophanes are dimeric in nature enables us to synthesize trimeric versions, which are capable of capturing (polypyridine)Ru(II) metal complexes in water with submicromolar affinity. In some cases, remarkable selectivity of binding is seen. The release of the captured guests can be arranged as described above. Captured guests are shielded by the erect walls from environmental effects. Interactions of electronically excited guests with water or external quenchers is prevented. Coupling of ground-state guests with electrodes is hindered. Since released guests avoid such issues, sharp ‘off-on’ switching of photochemical and electrochemical properties are seen. The cyclophane-induced switching ‘on’ of luminescence of (bipyridine)2(2-pyridylimidazole)Ru(II) in water is a visual example. Some of these ‘off-on’ phenomena are instances of molecular logic-based computation where sequential logic and combinational logic are combined. Overall, these studies are contributions to the broad field of molecular information handling (MIH).

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