"Click" synthesis of organo-silicon dendrimers, Main …
In this micro-review, the "click" synthesis and functions of organo-silicon dendrimers are summarized
Synthesis of an Organosilicon Dendrimer Containing …
In our previous works we have synthesized a number of luminescent organosilicon molecules, consisting of two types of luminophores (oligothiophenes with different conjugation length, connected through silicon atoms), which have the efficient energy transfer between them, leading to the co-called “dendritic molecular antennae effect”,. However, their PLQY was rather low (9–11%) that was limited by the PLQY of the acceptor luminophores used (ter- or quaterthiophene) and did not allow to call them NOLs. Bithiophenesilane monodendrons and dendrimers, the PLQY of which was significantly higher as compared to its constituent bithiophenesilanes, have also been reported. These nanoscale molecules, however, had only one type of luminophores and their PLQY was limited to 30%. The only dendritic molecule, which by its optical properties is very close to the NOLs reported in this work, is the oligoarylsilane dendrimer. This dendrimer has two types of luminophores (in fact, the same as in NOL-3 and NOL-4) within the intramolecular energy transfer efficiency of 88% and the overall PLQY of 41% that is too low for practical applications, in particular in plastic scintillators, described above.
NOLs can be considered as a particular type of “dendritic molecular antenna”, which consists of at least two types of luminophores united in one dendritic molecule with Förster energy transfer between them. However, most of the dendritic molecular antennas known nowadays are organic molecules or metal complexes, where luminophores can feely rotate relative to each other or linked through flexible groups,,,. This leads to a chaotic displacement of the luminophores relative to each other in the molecule of such dendrimers, resulting in theoretically high (90–99%), but experimentally decreased to 30–40% efficiency of Förster energy transfer and moderate to low overall PLQY. Recent results indicate that calculations based on just the changes in donor-emission lifetime and quantum yields clearly overestimate the excitation energy transfer efficiency, as many other nonradiative modes of de-excitation are widely ignored. Albeit there are a few examples of rigid dendritic molecular antennas with high luminescence quantum yields, ranging from 65 to 81%, their synthesis is complicated. It should be noted that small molecule artificial antennas have typical quantum yield between 12 and 60%. NOLs are rather simple rigid organosilicon molecules, which can be easily synthesized and possess high PLQY, measured experimentally in this work. Their overall PLQY is determined by multiplication of two parameters: 1) PLQY of the acceptor organic luminophor located in the center of NOLs and 2) the efficiency of intramolecular Förster energy transfer from the outer organic luminophores (donors) to the central organic luminophor (acceptor). Thus, choosing different acceptor luminophores with their own PLQYs leads to different PLQYs of the corresponding NOLs (compare PLQY of NOL-2 through NOL-7 having the same donor luminophores and different acceptor luminophores, see and ).
Synthesis of novel bifunctional organosilicon dendrons …
Giant pentane-soluble organo-silicon dendrimers have been synthesized using a triallylphenol brick according to a new divergent construction that uses a hydrosilylation−nucleophilic substitution sequence up to the ninth generation (G9). All the reactions were monitored by 1H, 13C, and 29Si NMR until G9, indicating that they were clean at the NMR accuracy until this last generation. MALDI TOF mass spectra were recorded for G1 to G4 and show the nature and amounts of defects that are intrinsic to the divergent construction. This technique and SEC (recorded up to G5) confirm the monodispersity (1.00 to 1.02) from G1 to G5. HRTEM and AFM images recorded for the high generations disclose the expected smooth dendrimer size progression and the globular shape. At G9, the theoretical number of termini (TNT) is 177 407 branches (abbreviation: G9-177 047). It is estimated that more than 105 terminal branches are actually present in the G9 dendrimer, far beyond the De Gennes “dense-packing” limit (6000 branches), and it is believed that the branch termini turn inside the dendrimer toward the core. This is corroborated by lower reaction rates and yields for the highest generation numbers presumably due to intradendritic reactions. It is probable that the dendritic construction is limited by the density of branches inside the dendrimer, i.e., far beyond the dense-packing limit.
9. Encapsulation and Stabilization of Gold Nanoparticles with “Click” Polyethyleneglycol Dendrimers. E. Boisselier, A. K. Diallo, L. Salmon, C. Ornelas, J. Ruiz, D. Astruc J. Am. Chem. Soc. 2010, 132, 2729–2742. Nanoscopic Assemblies Between Supramolecular Redox Active Metallodendrons and Gold Nanoparticles: Syntheses, Charaterization and Selective Recognition of H2PO4 -, HSO4 - and Adenosine-5’-Triphosphate (ATP2-) Anions. M.-C. Daniel, J. Ruiz, S. Nlate, J.-C. Blais, D. Astruc. J. Am. Chem. Soc. 2003, 125, 2617 – 2628.
2. Click Reactions Applied to Dendrimers - MDPI
DENDRIMERS: SYNTHESIS, PROPERTIES, BIOMEDICAL AND …
the synthesis and characterization of novel ..
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Dendrimers | Cell Membrane | Polymers
PAMAM-organosilicon (PAMAMOS) dendrimers ..
Construction of Giant Dendrimers Using a Tripodal …
Organosilicon Dendrimers and Irregular Hyperbranched Polymers
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