4432-94-4Relevant articles and documents
Zero-Overlap Fluorophores for Fluorescent Studies at Any Concentration
Dhara, Ayan,Flood, Amar H.,Olsson, Andrew H.,Raghavachari, Krishnan,Sadhukhan, Tumpa,Sheetz, Edward G.
, p. 12167 - 12180 (2020)
Fluorophores are powerful tools for the study of chemistry, biology, and physics. However, fluorescence is severely impaired when concentrations climb above 5 μM as a result of effects like self-absorption and chromatic shifts in the emitted light. Herein, we report the creation of a charge-transfer (CT) fluorophore and the discovery that its emission color seen at low concentrations is unchanged even at 5 mM, some 3 orders of magnitude beyond typical limits. The fluorophore is composed of a triphenylamine-substituted cyanostar macrocycle, and it exhibits a remarkable Stokes shift of 15 ?000 cm-1 to generate emission at 633 nm. Crucial to the performance of this fluorophore is the observation that its emission spectrum shows near-zero overlap with the absorption band at 325 nm. We propose that reducing the spectral overlap to zero is a key to achieving full fluorescence across all concentrations. The triphenylamine donor and five cyanostilbene acceptor units of the macrocycle generate an emissive CT state. Unlike closely related donor-acceptor control compounds showing dual emission, the cyanostar framework inhibited emission from the second state to create a zero-overlap fluorophore. We demonstrated the use of emission spectroscopy for characterization of host-guest complexation at millimolar concentrations, which are typically the exclusive domain of NMR spectroscopy. The binding of the PF6- anion generates a 2:1 sandwich complex with blue-shifted emission. Distinct from twisted intramolecular charge-transfer (TICT) states, experiment-supported density functional theory shows a 67° twist inside an acceptor unit in the CT state instead of displaying a twist between the donor and acceptor; it is TICT-like. Inspired by the findings, we uncovered similar concentration-independent behavior from a control compound, strongly suggesting this behavior may be latent to other large Stokes-shift fluorophores. We discuss strategies capable of generating zero-overlap fluorophores to enable accurate fluorescence characterization of processes across all practical concentrations.
Nickel-Catalyzed Direct Cross-Coupling of Aryl Sulfonium Salt with Aryl Bromide
Ma, Na-Na,Ren, Jing-Ao,Liu, Xiang,Chu, Xue-Qiang,Rao, Weidong,Shen, Zhi-Liang
, p. 1953 - 1957 (2022/03/27)
The direct cross-couplings of aryl sulfonium salts with aryl halides could be achieved by using nickel as a reaction catalyst. The reactions proceeded efficiently via C-S bond activation in the presence of magnesium turnings and lithium chloride in THF at ambient temperature to afford the corresponding biaryls in moderate to good yields, potentially serving as an attractive alternative to conventional cross-coupling reactions employing preprepared organometallic reagents.
Nickel(II)/N-Heterocyclic Carbene Catalyzed Desulfinylative Arylation by C?S Cleavage of Aryl Sulfoxides with Phenylboronic Acids
Yi, Xiaowen,Chen, Kai,Guo, Junjun,Chen, Wei,Chen, Wanzhi
supporting information, p. 4373 - 4377 (2020/07/27)
Suzuki-Miyaura coupling of haloarenes is the most widely used protocol for the synthesis of biphenyls. Organosulfur compounds are promising electrophiles since they are abundant in nature and versatile in organic synthesis. We report here the desulfinylative Suzuki-Miyaura coupling of aryl sulfoxides with phenylboronic acids using bench-stable nickel/5-(2,4,6-triisopropylphenyl)imidazolylidene[1,5-a]pyridines as the catalyst. The ligands are readily prepared from common commercial chemicals. The method is applicable to both symmetric and unsymmetric aryl sulfoxides, and a range of biphenyls bearing various functional groups were obtained in up to 94% yield. (Figure presented.).
