Efficient Utilization of Higher‐Lying Excited States to Trigger Charge‐Transfer Events

Abstract

Several new fullerene-heptamethine conjugates, which absorb as far as into the infrared spectrum as 800 nm, have been synthesized and fully characterized by physicochemical means. In terms of optical and electrochemical characteristics, appreciable electronic coupling between both electroactive species is deduced. The latter also reflect the excited-state features. To this end, time-resolved, transient absorption measurements revealed that photoexcitation is followed by a sequence of charge-transfer events which evolve from higher singlet excited states (i.e., S(2)--fast charge transfer) and the lowest singlet excited state of the heptamethine cyanine (i.e., S(1)--slow charge transfer), as the electron donor, to either a covalently linked C(60) or C(70), as the electron acceptor. Finally, charge transfer from photoexcited C(60)/C(70) completes the charge-transfer sequence. The slow internal conversion within the light-harvesting heptamethine cyanine and the strong electronic coupling between the individual constituents are particularly beneficial to this process.

Low-Dimensional Carbon Allotropes: Ground- and Excited-State Charge Transfer with NIR-Absorbing Heptamethine Cyanine

“…By virtue of their electron-donating strength, they have emerged as a complement to fullerenes, which are the omnipresent electron acceptors in solar energy conversion schemes. 38,39 Importantly, electronic interactions between SWCNTs or NG and heptamethine cyanine are traceable by Raman spectroscopy, which, in the current work, corroborates the n-doping of the carbon allotropes. In the case of SWCNTs, which are intrinsically p-doped, molecular n-doping is rather scarce.…”

Interaction of Polymethine Dyes with Detonation Nanodiamonds

“…[15][16][17] Hitherto, there have been published quite a few works concerned with the interaction of polymethine dyes with fullerenes, carbon nanotubes, and graphene-like structures, up to their direct chemical bonding. [18][19][20] Withal, there is a group of carbon nanoparticles, namely detonation nanodiamonds (DND), for which, to the best of our knowledge, such studies have not yet been conducted. DND, introduced as far back as 1963, [21] are one of the first artificial carbon nanomaterials.…”

Light‐Harvesting Materials for Organic Electronics

“…Meng et al [29] have prepared a cyanine-C 60 dyad which was used to construct a photovoltaic device reaching a modest 0.1% light energy conversion efficiency at low incident light intensity. Our research group [30] has recently described the preparation of heptamethine cyanine C 60 and C 70 conjugates (14, 15) by reacting heptamethine cyanine aldehyde derivative with N-octylglycine, in the presence of the corresponding fullerene ( Fig. 9.12).…”