Reversibly Switchable Fluorescent Molecular Systems Based on Metallacarborane–Perylenediimide Conjugates

Abstract

Icosahedral metallacarboranes are q-shaped anionic molecules in which two icosahedra share one vertex that is am etal center. The most remarkable of these compounds is the anionic cobalt-based metallacarborane [Co(C 2 B 9 H 11) 2 ] À , whose oxidation-reduction processes occur via an outer sphere electron process. This, along with its low density negative charge, makes[ Co(C 2 B 9 H 11) 2 ] À very appealingt o participatei ne lectron-transfer processes. In this work, [Co(C 2 B 9 H 11) 2 ] À is tethered to ap erylenediimided ye to produce the first examples of switchable luminescentm olecules and materials based on metallacarboranes. In particular, the electronic communication of [Co(C 2 B 9 H 11) 2 ] À with the appended chromophore unit in these compounds can be regulated upon application of redox stimuli, which allows the reversible modulation of the emitted fluorescence. As such, they behave as electrochemically-controlled fluorescent molecular switches in solution, which surpass the performance of previous systemsb ased on conjugates of perylendiimides with ferrocene. Remarkably,t hey can form gels by treatment with appropriate mixtureso fo rganic solvents, which result from the self-assembly of the cobaltabisdicarbollide-perylendiimidec onjugates into 1D nanostructures. The interplay between dye p-stackinga nd metallacarborane electronic and steric interactions ultimately governs the supramolecular arrangementi nt hese materials, which for one of the compoundsp repared allows preserving the luminescent behavior in the gel state.

Far‐Red and Near‐Infrared Boron Schiff Bases (BOSCHIBAs) Dyes Bearing Anionic Boron Clusters

“…This result would imply that functionalization with this kind of boron clusters causes a strongly quenching of the luminescence, most likely because the presence of boron cluster prevents the electronic transition in the molecule. The phenomenon of fluorescence quenching was previously observed in different kind of compounds bearing COSAN moieties, such as organotin dyes [49] and metallacarborane‐perylenediimide conjugates [62] . In the latter, one or two COSAN units were tethered to the perylenediimide dye to produce switchable luminescent molecules, in which the emitted fluorescence could be reversible modulated upon application of a redox stimuli.…”

“…The phenomenon of fluorescence quenching was previously observed in different kind of compounds bearing COSAN moieties, such as organotin dyes [49] and metallacarborane-perylenediimide conjugates. [62] In the latter, one or two COSAN units were tethered to the perylenediimide dye to produce switchable luminescent molecules, in which the emitted fluorescence could be reversible modulated upon application of a redox stimuli. There, demonstrated that to achieve redox-controlled fluorescence switching in COSAN-fluorophore systems it is required a suitable composition and structure that allow a tuneable excited-state interaction between the dye and the COSAN as to selectively quench fluorescence in one of the redox states and selective access to the redox switching of the COSAN derivative without affecting the fluorophore.…”

Multimodal Fluorescence Switching Materials: One Dye to Have Them All

“…[ 11,31–40 ] As for the dye, we must select molecular emitters that, under controlled modification of the surrounding environment, are capable of undergoing both single‐ and two‐color fluorescence switching through different photochemical mechanisms. For instance, this is the case of the perylene diimide derivative N,N ′‐bis(1‐hexylheptyl)perylene‐3,4,9,10‐bis(dicarboximide) (PDI, Figure S1, Supporting Information), a bright and stable lime green fluorophore in diluted organic solutions whose emission can be i) switched off by photoinduced electron transfer (PET) in the presence of close‐by electron donors, [ 41,42 ] and ii) turned into red excimer luminescence upon aggregation in concentrated mixtures [ 41 ] or polymer media. [ 43 ] Therefore, the use of PCMs to modulate the behavior of this class of dyes offers a unique and straightforward approach toward photo‐ and thermofluorochromic materials that exhibit multiple switching modes.…”

PTCDI-Ph Molecular Layer Stack-Based Highly Crystalline Microneedles As Single-Component Efficient Photodetector

“…However, a greater understanding of the molecular packing and their optical and electrical properties has become essential for the fabrication of efficient organic electronic devices. − Recently, optoelectronic devices, such as organic photodiodes and phototransistors, based on organic semiconducting material have found potential applications in light detection and signal amplifications. − The major challenges with such devices are their poor photoconductivity and the stability. , Relatively large binding energy (∼0.3 to 1 eV) of the molecules prevents exciton dissociation and boosts carrier recombination. , As a result, it is challenging to improve the photocurrent for the devices based on a single layer. Various one-dimensional structures of inorganic materials have shown enhanced photocurrent and have been used for photodetection applications. − However, different derivatives of perylene diimides have been emerging as promising materials because of their significantly enhanced performances on photocurrent. ,− …”