In the present work, gold electrodes were modified using a redox-active layer based on dipyrromethene complexes with Cu(II) or Co(II) and a dipodal anion receptor functionalized with dipyrromethene. These modified gold electrodes were then applied for the electrochemical detection of anions (Cl, SO, and Br) in a highly diluted water solution (in the picomolar range). The results showed that both systems, incorporating Cu(II) as well as Co(II) redox centers, exhibited highest sensitivity toward Cl. The selectivity sequence found for both systems was Cl > SO > Br. The high selectivity of Cl anions can be attributed to the higher binding constant of Cl with the anion receptor and the stronger electronic effect between the central metal and anion in the complex. The detection limit for the determination of Cl was found at the 1.0 pM level for both sensing systems. The electrodes based on Co(II) redox centers displayed better selectivity toward Cl anion detection than those based on Cu(II) centers which can be attributed to the stronger electronic interaction between the receptor-target anion complex and the Co(II)/Co(III) redox centers in comparison to the Cu(II)/Cu(I) system. Applicability of gold electrodes modified with DPM-Co(II)-DPM-AR for the electrochemical determination of Cl anions was demonstrated using the artificial matrix mimicking human serum.
A library of bidentate diols, as well as tridentate triols and aminodiols, derived from (+)-sabinol, was synthesized in a stereoselective manner. Sabinol was transformed into allylic trichloroacetamide via Overman rearrangement of the corresponding trichloroacetimidate. After changing the protecting group to Boc, the enamine was subjected to stereospecific dihydroxylation with OsO4/NMO, resulting in the (1R,2R,3R,5R)-aminodiol diastereomer. The obtained primary aminodiol was transformed to a secondary analogue. The ring closure of the N-benzyl-substituted aminodiol with formaldehyde was investigated and regioselective formation of the spiro-oxazolidine ring was observed. Hydroboration or dihydroxylation of sabinol or its benzyl ether with OsO4/NMO resulted in the formation of sabinane-based diols and triols following a highly stereospecific reaction. Treatment of sabinol with m-CPBA afforded O-benzoyl triol as a diastereoisomer of the directly dihydroxylated product, instead of the expected epoxy alcohol. The resulting aminodiols, diol, and triols were applied as chiral catalysts in the reaction of diethylzinc and benzaldehyde from moderate to good selectivity.
Only a few straightforward procedures for the preparation of indolo[2,3‐c]carbazoles are known, despite promising features for material applications. Herein we present a convenient synthesis of 5,10‐dihydrobenzo[a]indolo[2,3‐c]carbazoles using an oxidative cyclization of 1,2‐bis(1H‐indol‐2‐yl)benzenes prepared from readily accessible starting materials. Functionalization through electrophilic aromatic substitution reactions and palladium‐catalyzed cross‐coupling reactions were investigated, which lead to the isolation of new functionalized 5,10‐dihydrobenzo[a]indolo[2,3‐c]carbazoles, whose steady state electronic spectroscopy has been examined.
The
excited-state dynamics of four 5,10-dihydrobenzo[a]indolo[2,3-c]carbazoles in solution and in films
were studied with stationary and time-resolved spectroscopies. The
solvent dependency of the photophysics reveals no appreciable dipole
moment in the ground state. In the excited state, electron-withdrawing
substituents contribute to an outspoken charge-transfer character.
In films, although the molecules are mostly present as monomers, the
excited-state dynamics are characterized by a cascade of energy-transfer
processes to excited dimers and aggregates which dominate the photoluminescence
(PL) spectra. The properties of the aggregates depend on the used
substituents. The electroluminescence spectra obtained from single-layer
and multilayer devices mostly resemble the PL spectra, but show contributions
from other species such as electromers or electroplexes. It is inferred
that the different substituents lead to a different packing of the
carbazole moieties, each of which has different mobilities and recombination
probabilities.
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