Broadband Two-Photon Absorption Characteristics of Highly Photostable Fluorenyl-Dicyanoethylenylated  Fullerene Dyads (Postprint)
University of Massachusetts Lowell Lowell United States
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We synthesized four C60-light-harvesting antenna dyads C60 CPAF-Cn n 4, 9, 12, or 18 1-Cn for the investigation of their broadband nonlinear absorption effect. Since we have previously demonstrated their high function as two-photon absorption 2PA materials at 1000 nm, a different 2PA wavelength of 780 nm was applied in the study. The combined data taken at two different wavelength ranges substantiated the broadband characteristics of 1-Cn. We proposed that the observed broadband absorptions may be attributed by a partial -conjugation between the C60 cage and CPAF-Cn moieties via endinitrile tautomeric resonance, giving a resonance state with enhanced molecular conjugation. This transient state could increase its 2PA and excited-state absorption at 800 nm. In addition, a trend of concentration-dependent 2PA cross-section 2 and excited-state absorption magnitude was detected showing a higher value at a lower concentration that was correlated to increasing molecular separation with less aggregation for dyads C60CPAF-C18 and C60CPAF-C9, as better 2PA and excited-state absorbers.
- Inorganic Chemistry
- Atomic and Molecular Physics and Spectroscopy