Higher‐Excited‐State Photophysical Pathways in Multichromophoric Systems Revealed by Single‐Molecule Fluorescence Spectroscopy

Abstract

Singlets annihilated: A single‐molecule fluorescence spectroscopic study of multichromophoric peryleneimide‐substituted polyphenylene‐core dendrimers under various conditions indicates that increased intersystem crossing (see graphic) as a consequence of an annihilation process might represent a general motif for increased photobleaching of the first intensity levels in multichromophoric systems.

The Chemistry of Organic Nanomaterials

“…[324] These dendrimers (like the bischromophores mentioned in Section 5.3) behave as single photon sources, as efficient singlet-singlet annihilation means only one photon is emitted at a time even when more than one chromophore is excited simultaneously. [317,321,323,324] Both singlet-singlet and singlettriplet annihilation have been detected in these systems by SMS, but only the former can be visualized in studies on the ensemble. [301,303,304,310] Single-photon emission, in which light pulses each consisting of a single photon are produced at a user-determined time is a particularly exciting concept in modern electronics.…”

The Rylene Colorant Family—Tailored Nanoemitters for Photonics Research and Applications

“…[126] Careful analysis of the "on/off" jumps that correspond to different intensity levels in multichromophoric systems can result in quantitative information on ISC, and even ISC involving higher excited states (see Figure 12 b). [129] Besides the above-mentioned on/off blinking process, there is an additional rarer event that leads to longer fluorescence intermittence than excursion to the triplet state. Long off times (in the range of seconds) are caused by the formation of a radical anion on one of the rylene chromophores.…”

“…The application and quality of several of the structures discussed in Section 4.1 as singlephoton sources have already been investigated and quantified. [28,126,127,129,[136][137][138] Other approaches to generate singlephoton sources with dendronized rylene systems comprise shockwave-induced particle formation with compound 16, in which aggregation of the chromophores is prevented, and tightly packed particles with large cross-sections are produced. [45,46] Repeated excitation (as in the case of single-molecule studies) of the chromophores can also lead to ISC to the triplet state.…”

“…[119] Therefore, they represent an ideal scaffold since they do not interfere with energy-transfer processes themselves, provided that the chromophores involved are chosen to absorb and emit in the visible part of the spectrum. [118,120] A biphenyl unit 19 [121][122][123] or a tetraphenylmethane moiety 17 or 18 [28,[124][125][126][127][128][129] were chosen as central dendrimer cores for the preparation of polyphenylene dendrimers with different numbers of PMI chromophores at distinct locations of the periphery ( Figure 10). The tetraphenylmethane core ensures a higher structural rigidity as well as the formation of a globular architecture, whereas the biphenyl unit results in a higher degree of mobility along the biphenyl unit as well as a flatter architecture.…”

Counting Constituents in Molecular Complexes by Fluorescence Photon Antibunching

“…The introduction of pulsed laser excitation has greatly benefited the applications of photon antibunching at the Counting constituents in molecular complexes by fluorescence photon antibunching Samantha Fore, Ted A. Laurence, Christopher W. Hollars, Thomas Huser single molecule level [11,17] and enabled the study of multiple photophysical parameters simultaneously [18]. During the last few years, this technique was also extensively used to determine the number of active emitting sites in multichromophoric molecules , ranging from large conjugated molecules [19,20] to small dendritic molecules with very few chromophore units [21][22][23][24][25][26][27], and to determine the number of active chromophore units in fluorescent proteins [28]. Other recent applications have led to applications in photonic wire structures and macromolecular complexes [29][30][31].…”