A Redox-Active π-Extended Tetrathiafulvalene-Based Carbon Nanohoop Featuring Unique Kasha/Anti-Kasha Dual Emissions: Structure, Photophysical Properties, and Photoconductivity.

Developing functionalized cycloparaphenylenes (CPPs) that respond to various stimuli, particularly redox, remains challenging yet crucial for advanced nanocarbon applications. Here, we report the exploration of the synergy between the concave π-extended tetrathiafulvalene (exTTF) and the curved CPP scaffold for constructing the rigid, conjugated nanohoop exTTF[10]CPP. X-ray analysis reveals a unique spherical packing arrangement in which six adjacent nanohoops interlock through concave and convex interactions. Interestingly, fluorescence studies revealed that exTTF[10]CPP exhibited unexpected anti-Kasha emissions originating from higher excited states, along with Kasha emission from S1 excited state in toluene and THF. However, in a PMMA film, it displayed a redshifted Kasha emission. The unique Kasha/anti-Kasha dual-emission behavior represents a rarely explored photophysical phenomenon within exTTF derivatives and nanocarbon-based systems. Ultraviolet-Visible (UV-vis) absorption investigations showed that exTTF[10]CPP demonstrated reversible redox responsiveness with tunable binding affinity for C60 up to 1.92 × 106 M-1. Notably, femtosecond transient absorption measurements further revealed a prolonged lifetime of the charge-separated state, C60 •-/exTTF[10]CPP•+, which provides sufficient time for charge utilization. This exceptional charge-transfer property enhances the photocurrent in C60⊂exTTF[10]CPP-based cast film, which is 2.43 times higher than that of exTTF[10]CPP alone, highlighting its potential in photoelectronic device.