Prolonged Charge-Separated States of Starburst Tetra(diphenylaminofluoreno)[60]fullerene Adducts upon Photoexcitation

Abstract

Construction of starburst C60(>DPAF-C9)4 pentads was coupled with the use of highly fluorescent diphenylaminofluorene-C9 (DPAF-C9) addends as donor components in conjunction with the fullerene acceptor during single-photon excitation processes. High quantum yields (PhiCS) of charge-separation processes in the range 0.83-0.90 for C60(>DPAF-C9)n (n = 1, 2, or 4) were obtained in the formation of C60*-(>DPAF*+-C9)(>DPAF-C9)n-1 transient states. The lifetime of the radical ion-pairs (tauRIP) was found to be 900 ns for starburst C60(>DPAF-C9)4 (3) samples, which is 6-fold longer than that of the linear analogue C60(>DPAF-C9) (1), with a ca. 2 times increase of the charge-separation rate (kCS) compared to that of 1. These data implied the important role of sterically hindered DPAF-C9 pendants arranged in a starburst-like environment that encapsulates the central C60 core on extending the tauRIP. We interpreted the phenomena by the occurrence of intramolecular migration or exchange of electron or positive charge among multiple DPAF-C9 pendants of C60*-(>DPAF*+-C9)(>DPAF-C9)n-1, which gives an increased rate in charge generation and delayed charge recombination.

Synthesis and characterization of highly photoresponsive fullerenyl dyads with a close chromophore antenna–C60 contact and effective photodynamic potential

“…These nonlinear photonic responsive data together with the nanosecond transient absorption measurements based on the linear photoexcitation of the same series of fullerenyl adducts provided strong evidence of the effectiveness of through-space periconjugation interactions. These interactions were proposed to facilitate the high efficiency of intramolecular electron and energy transfer processes from the DPAF-C n donor antenna to the C 60 acceptor cage upon photoexcitation 16,17. In this study, we further extended our investigation of the periconjugation approach by functional conversion of C 60 (>DPAF-C n ) dyad materials to produce molecules with broadband absorption characteristics.…”

Novel photoswitchable dielectric properties on nanomaterials of electronic core–shell γ-FeOx@Au@fullerosomes for GHz frequency applications

“…25 In benzonitrile (PhCN), electron-transfer process was found to dominate photophysical events giving the charge-separated (CS) state 1) in a long life-time. 31 A closely linked molecular nanostructure with periconjugation between C 60 > and the carbonyl moiety of DPAF-C n in a spacing distance of only ~3.5 Å 25 and the concurrence of keto-enol tautomerism at the conjugation bridge 29 were reasoned for the observed ultrafast photoresponsive rate.…”

Solvent and Concentration-Dependent Aggregation Study of C60Dyads and Multiads on Nonlinear Photonic Properties

“…Especially, both C 60 (>DPAF-C 9 ) 2 triads and C 60 (>DPAF-C 9 ) 4 pentads gave nonlinear light transmittance reduction and attenuation responses in femtosecond region with an observed low transmittance value (∼35%) at the high laser power above 80-650 GW/cm 2 (3). The phenomena were attributed to large fs 2PA cross-section values of C 60 (>DPAF-C 9 ) 2 and C 60 (>DPAF-C 9 ) 4 in the given concentration and, apparently, correlated to a higher number of DPAF-C 9 antenna in the structure of C 60 (>DPAF-C 9 ) 4 . The result also implied good photostability of these nanomaterials at high laser light energy.…”

“…A series of C 60 -keto-DPAF-C 9 assembly nanomaterials, where DPAF-C 9 represents 9,9-di(3,5,5-trimethylhexyl)-2-diphenylaminofluorene, including the monoadduct C 60 (>DPAF-C 9 ), the bisadducts C 60 (>DPAF-C 9 ) 2 , and the tetraadducts C 60 (>DPAF-C 9 ) 4 were synthesized and extensively studied recently for their nonlinear photonic properties (1)(2)(3)(4). All of these nanomaterials were found to exhibit large two-photon absorption (2PA) cross-sections in femtosecond (fs) and picosecond (ps) regions (3).…”