Jong Hun Moon

A Benzobisimidazolium-Based Fluorescent and Colorimetric Chemosensor for CO2

A new sensor for the fluorescent and colorimetric detection of CO(2) is described. The system utilizes fluoride to activate a tetrapropyl benzobisimidazolium salt and operates in the absence of an exogenous base. On the basis of spectroscopic and theoretical analyses, the mode of action of the present system is ascribed to the fluoride-induced formation of an N-heterocyclic carbene intermediate that reacts with CO(2) to form an imidazolium carboxylate.

Ratiometric Fluorescent Chemosensor for Silver Ion at Physiological pH

Bis-pyrene derivative 1, bearing two pyrene and pyridine groups, was synthesized as a ratiometric fluorescent chemosensor for Ag(+) in aqueous solution. Fluorescent chemosensor 1 displayed a selective ratiometric change with Ag(+), which was attributed to the excimer-monomer emissions of pyrenes. A mechanism for the binding mode was proposed based on fluorescence changes, NMR experiments, and theoretical calculations.

Highly Efficient Organic Hole Transporting Materials for Perovskite and Organic Solar Cells with Long‐Term Stability

Small molecules based on N-atom-linked phenylcarbazole-fluorene as the main scaffold, end-capped with spirobifluorene derivatives, are developed as organic hole-transporting materials for highly efficient perovskite solar cells (PSCs) and bulk heterojunction (BHJ) inverted organic solar cells (IOSCs). The CzPAF-SBF-based devices show remarkable device performance with excellent long-term stability in PSCs and BHJ IOSCs with a maximum PCE of 17.21% and 7.93%, respectively.

A Chromo‐Fluorogenic Tetrazole‐Based CoBr2 Coordination Polymer Gel as a Highly Sensitive and Selective Chemosensor for Volatile Gases Containing Chloride

Crystalline coordination polymers are a newer class of organic–inorganic hybrid nanomaterials created by infinitely extending metal–ligand coordination interactions. These polymers show promise in a broad range of applications, including gas storage, molecular sieves, ion exchange, sensing, magnetism, and catalysis. [1, 2] Recently, a rational-design strategy for supramolecular gels based on the concept of coordination polymers is attracting interest. [3–6] In particular, recent studies have demonstrated that simple bridging organic units can facilitate the formation of coordination polymer gels in the absence of auxiliary moieties (e.g., urea, sugar, cholesterol, long alkyl chains), offering new possibilities to produce functional soft materials from structurally

Fluorescent Sensing of Triphosphate Nucleotides via Anthracene Derivatives

A nucleotide is composed of a nucleobase, a five-carbon sugar, and phosphate groups. Recognition of these three sites can provide useful information for the development of selective fluorescent receptors for a specific nucleotide. In this paper, anthracene derivatives with two imidazolium groups at the 1,8- and 9,10-positions, quaternary ammonium groups, or the boronic acid group were examined for the recognition of nucleotides, such as ATP, GTP, CTP, TTP, UTP, ADP, and AMP, via fluorescence changes. The anthracene group provides the interaction between the bases of the nucleotides. The imidazolium and quaternary ammonium groups induce hydrogen bonding interactions with the phosphate groups of the nucleotides. The boronic acid group can interact with the ribose of the nucleotides.

Cyclic benzobisimidazolium derivative for the selective fluorescent recognition of HSO4−via a combination of C–H hydrogen bonds and charge interactions

In this study, a novel fluorescent cyclic benzobisimidazolium derivative was designed and prepared for the selective recognition of HSO4−. Pre-organization, neutral C–H hydrogen bonds and charge interactions play key roles in recognizing HSO4− in aqueous solution. Spectroscopic studies, including UV-vis and fluorescence, showed that this cyclic receptor exhibited high selectivity in response to HSO4−. X-Ray crystal data, NMR data and theoretical calculations are presented to explain its unique binding mode.

Copper-Catalyzed trans-Hydroboration of Terminal Aryl Alkynes: Stereodivergent Synthesis of Alkenylboron Compounds

A Cu-catalyzed highly Z-stereoselective hydroboration of alkynes with 1,8-naphthalenediaminatoborane (HB(dan)) is developed. DPEphos (bis[(2-diphenylphosphino)phenyl]ether)-ligated Cu catalysts produced alkenylboron compounds from terminal alkynes with excellent Z-stereoselectivity. In contrast, using a SIPr-CuCl complex as the precatalyst exclusively produced E-hydroboration products at mild conditions. Both catalytic procedures form alkenylboron products stereocomplementary to each other, constituting stereodivergent hydroboration of alkynes through Cu catalysis. Deuterium labeling and isomerization studies support the Z-selective hydroboration via trans-addition of the boron reagent to terminal alkynes as opposed to precedent noble-metal-catalyzed trans-hydroborations.

Copper-Catalyzed Enantioselective Hydroboration of Unactivated 1,1-Disubstituted Alkenes

We report an efficient and highly enantioselective hydroboration of aliphatic 1,1-disubstituted alkenes with pinacolborane using a phosphine-Cu catalyst. The method allows facile preparation of enantiomerically enriched β-chiral alkyl pinacolboronates from a range of 1,1-disubstituted alkenes with high enantioselectivity up to 99% ee. Unprecedented enantiodiscrimination between the geminal alkyl substituents was observed with functional group compatibility in the hydroboration. Furthermore, a catalyst loading as low as 1 mol % furnished the desired product without a decrease in yield or selectivity, demonstrating its efficiency in gram scale synthesis.

Size dependent electronic band structures of β- and γ-graphyne nanotubes

In the present paper, density functional theory calculations have been implemented by using Dmol3 to study the electronic band structures of β-graphyne nanotubes (βGyNTs) and γ-graphyne nanotubes (γGyNTs). Our results found different GyNTs show diverse electronic band structures. All βGyNTs have quite small band gaps without any correlation with tube size. Meanwhile, γGyNTs, no matter zigzag or armchair, exhibit semiconductor characteristics with oscillatory band gap ranging from 0.48 eV to 1.20 eV. Furthermore, based on the variation of band gap, both zigzag and armchair γGyNTs can be divided into two subgroups: 2m and 2m + 1 where n is a positive integer, following the order of 2m + 1 > 2m.

Systematic Strategy for Designing Immidazolium Containing Precursors To Produce N-Heterocyclic Carbenes: A DFT Study

A series of cationic N-heterocyclic carbene (NHC) precursors that can be utilized as fluorescent chemosensors for carbon dioxide capture were investigated by density functional theory (DFT) calculations. Activation energy barriers for the reactions of the cationic NHC precursors and hydrogen carbonate (HCO3(-)) based on intrinsic reaction coordinate (IRC) profiles as well as proton affinity of the precursors were compared. The calculated proton affinity of 1-ethyl-3-methylimidazol-2-yliene was in good agreement with experimental one within the margin of error. We clarified main factors to lower the activation energy barrier based on the correlation among the number of N-heterocyclic functional group, aromatic ring size, and structural characteristics for the candidate compounds. On the basis of the results, it was verified that some of our model systems spontaneously generate NHCs without any specific catalyst.