Monthly Archives: September 2023

Easy Access to Tertiary Amines from Carbonyl Compounds with Substituted Amine‐Boranes: A Substrate, Catalyst, and Additive‐Free Approach Under Mild Conditions

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Easy Access to Tertiary Amines from Carbonyl Compounds with Substituted Amine-Boranes: A Substrate, Catalyst, and Additive-Free Approach Under Mild Conditions

An operationally simple and efficient protocol for the transformation of carbonyl compounds to tertiary amines with various secondary amine-boranes is reported. The reaction proceeds at room temperature and requires a short reaction time under mild conditions. The reaction encompasses a broad substrate scope and furnishes good-to-excellent yields of the amines in a chemoselective fashion.


Abstract

Tertiary amines are ubiquitous and play an essential role in organocatalysis, pharmaceuticals, and fine chemicals. Amongst various synthetic procedures known for their synthesis, the reductive amination of carbonyl compounds has been found to be a proficient method. Over the past few decades, different synthetic strategies for reductive amination have been developed. Most of them suffer from the use of transition metals and/or harsh reaction conditions. Herein, we present an efficient, operationally simple protocol for the chemoselective transformation of carbonyl compounds to tertiary amines under benign conditions. The strategy encompasses a broad substrate scope under the metal-free condition at room temperature and does not require any solvent. A detailed mechanistic investigation was performed with the aid of control experiments and computational study to shed light on the reaction pathway.

New Molecular Design, Step‐Saving Synthesis, and Applications of Indolocarbazole Core‐Based Oligo(hetero)arenes

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New Molecular Design, Step-Saving Synthesis, and Applications of Indolocarbazole Core-Based Oligo(hetero)arenes

The introduction of 3, 4-ethylenedioxythiophene (EDOT) into indolocarbazole-based hole-transporting materials (HTMs) as π-spacers significantly promoted the PCEs of up to 17.5 % of their corresponding perovskite solar cells (PSCs).


Abstract

In this work, we have successfully synthesized 15 new examples (LLA01-06; LinLi01-10) of small-molecule hole-transporting materials (HTM) using the less explored indolocarbazole (ICbz) as core moiety. Different from previously reported ICbz HTMs, LinLi01-10 exhibit new molecular designs in which 3,4-ethylenedioxythiophene (EDOT) units are inserted as crucial π-spacers and fluorine atoms are introdcued into end-group molecules. These substantially improve the materials solubility and device power conversion efficiencies (PCEs) while fabricated in perovskite solar cells (PSC). More importantly, LinLi01-10 are generated by a sustainable synthetic approach involving the use of straightforward C−H/C−Br couplings as key transformations, thus avoiding additional synthetic transformations including halogenation and borylation reactions called substrate prefunctionalizations usually required in Suzuki reactions. Most HTM molecules can be purified simply by reprecipitations instead of conducting column chromatography. In contrast to LLA01-06 without additional EDOT moieties, PSC devices using LinLi01-10 as hole-transport layers display promising PCEs of up to 17.5 %. Interestingly, PSC devices employing seven of the LinLi01-10 as hole-transport molecules, respectively, are all able to show an immediate >10 % PCE (t=0) without any device oxidation/aging process that is necessary for the commercial spiro-OMeTAD based PSCs.

Dual Pd‐Acid Sites Confined in a Hierarchical Core‐Shell Structure for Hydrogenation of Nitrobenzene

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Dual Pd-Acid Sites Confined in a Hierarchical Core-Shell Structure for Hydrogenation of Nitrobenzene

A core-shell structured catalyst with dual active sites (Pd and acidic sites) was designed to investigate the synergistic effect of Pd and acid sites in TS-1 during the hydrogenation of nitrobenzene.


Abstract

A core-shell structured Pd@TS-1@meso-SiO2 catalyst with confined Pd nanometals has been fabricated by one-pot synthesis, impregnation method and sol-gel method. With the promotion of acid sites and protection of mesoporous silica shell, Pd@TS-1@meso-SiO2 shows higher activity than commercial comparison and higher stability than sample without mesoporous silica shell in the hydrogenation of nitrobenzene. The schematic illustration of the synergy effect is also proposed.

A Pincer Cobalt Complex as Catalyst with Dual Hydrogenation Activities for Hydrodeoxygenation of Ketones with H2

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A Pincer Cobalt Complex as Catalyst with Dual Hydrogenation Activities for Hydrodeoxygenation of Ketones with H2†

A homogeneous cobalt catalyst with dual hydrogenation activities was developed for deoxygenation of ketones with a Lewis acid as the co-catalyst. This protocol features a broad substrate scope and excellent functional group tolerance. Mechanistic studies supported a hydrogenation-dehydration-hydrogenation pathway for this hydrodeoxygenation reaction.


Comprehensive Summary

Reductive deoxygenation of ketones using H2 is a highly desirable but also challenging transformation in both chemical synthesis, industrial-scale petroleum and biomass feedstock reforming processes. Herein, we report a cooperative cobalt/Lewis acid (LA)-catalyzed hydrodeoxygenation of ketones using H2 as the reductant. In particular, the newly developed pincer cobalt catalyst possesses dual hydrogenation activities for both ketones and alkenes under the same reaction conditions. This reaction features a broad substrate scope, excellent functional-group compatibility, and potential applicability.

Equatorial Perturbation Driven Reaction Bifurcation in Non‐Heme Iron Complexes for Chlorite Oxidation

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Equatorial Perturbation Driven Reaction Bifurcation in Non-Heme Iron Complexes for Chlorite Oxidation

An experimental study is presented involving biomimetic models of iron complexes, namely N4Py and its methyl-substituted analogs (MeN4Py, N4PyMe). These complexes were reacted with sodium chlorite at room temperature and physiological pH of 5.0. Our results demonstrate that the iron complexes efficiently oxidize chlorite via formation of iron(IV) oxo intermediates albeit via different reaction pathways.


Abstract

Chlorine oxyanions have various applications, such as bleaching and oxidizers in rocket fuels. However, their high solubility in water and long environmental lifetimes have led to ecological concerns, especially regarding drinking water quality. This study focuses on the conversion of chlorite to chlorine dioxide, which is of significant interest as it exhibits superior antimicrobial activity and generates less harmful byproducts for water treatment. Two nonheme iron(II) complexes capable of producing chlorine dioxide from chlorite at room temperature and pH 5.0 are presented. These complexes oxidize chlorite through high-valent iron (IV)-oxo intermediates formed in-situ. The study establishes second-order rate constants for chlorite oxidation and investigates the effects and mechanisms involved by substituting a methyl group in the secondary coordination sphere of the FeIV(O)(N4Py) system. By employing kinetic analysis and spectroscopic investigations, the crucial elements for the reaction mechanism in chlorite oxidation are identified. These findings pave the way for future advancements in this field.

Zwitterionic Polymer: A New Paradigm for Protein Conjugation beyond PEG

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Zwitterionic Polymer: A New Paradigm for Protein Conjugation beyond PEG

PEGylation was usually recognized as a gold standard to improve the stability and half-life of protein drugs. Although hugely succussed, the drawbacks of PEGylated proteins, such as accumulated toxicity and anti-PEG antibodies, compromise the full therapeutic potential of protein drugs. With super-hydrophilicity and superior anti-fouling properties, zwitterionic polymer is gradually accepted as an alternative to PEG for protein conjugation. In this review, we discuss a series of features exhibited by protein-zwitterionic polymer conjugate that outperform PEGylated protein.


Abstract

To render protein drugs more suitable for clinical treatment, PEGylation has been widely used to ameliorate their inherent deficiencies, such as poor stability, rapid elimination in the bloodstream, and high immunogenicity. While increasingly PEGylated protein drugs have been approved by the FDA, the non-degradability of PEG and the emergence of anti-PEG antibodies after injection raise concerns about their cumulative chronic toxicity and long-term therapeutic efficacy. Zwitterionic polymer, with a unique structure containing equal amounts of positively charged and negatively charged groups, shows a different hydration behavior to PEG, which may be a superior PEG alternative for protein conjugation. In this concept review, a series of features beyond that of PEGylated protein exhibited by protein-zwitterionic polymer conjugate are discussed and some suggestions are presented for their future direction.

Voltage‐ and Power‐Conversion Performance of Bi‐functional ZrO2 : Er3+/ Yb3+ Assisted and Co‐sensitized Dye Sensitized Solar Cells for Internet of Things Applications

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Voltage- and Power-Conversion Performance of Bi-functional ZrO2 : Er3+/ Yb3+ Assisted and Co-sensitized Dye Sensitized Solar Cells for Internet of Things Applications

A bifunctional ZrO2  : Er3+/Yb3+ co-sensitized dye-sensitized solar cell shows a power conversion efficiency of 12.35 %. Six cells connected in series gave a VOC of 4.52 V, which is sufficient to power up internet of things (IoT) devices.


Abstract

Giant power conversion efficiency is achieved by using bifunction ZrO2 : Er3+/Yb3+assisted co-sensitised dye-sensitized solar cells. The evolution of the crystalline structure and its microstructure are examined by X-ray diffraction, scanning electron microscopy studies. The bi-functional behaviour of ZrO2 : Er3+/Yb3+ as upconversion, light scattering is confirmed by emission and diffused reflectance studies. The bi-function ZrO2 : Er3+/Yb3+ (pH=3) assisted photoanode is co-sensitized by use of N719 dye, squaraine SPSQ2 dye and is sandwiched with Platinum based counter electrode. The fabricated DSSC exhibited a giant power conversion efficiency of 12.35 % with VOC of 0.71 V, JSC of 27.06 mA/cm2, FF of 0.63. The results, which motivated the development of a small DSSC module, gave 6.21 % and is used to drive a tiny electronic motor in indoor and outdoor lighting conditions. Small-area DSSCs connected in series have found that a VOC of 4.52 V is sufficient to power up Internet of Things (IoT) devices.

Water‐Soluble Fullerene Monoderivatives for Biomedical Applications

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Water-Soluble Fullerene Monoderivatives for Biomedical Applications

Monoderivatives of fullerenes functionalized with hydrophilic groups make them water soluble, while preserving the hydrophobic fullerene cage. These molecules have intriguing biomedical applications, including drug delivery, photodynamic therapy (PDT), antiviral and antimicrobial activity and reactive oxygen species (ROS)-scavenging abilities. Herein we discuss the synthesis and biomedical applications of water-soluble fullerene monoderivatives and their biological behavior based on their structures. (Image created with BioRender.com.)


Abstract

Monoderivatives of fullerenes functionalized with hydrophilic groups make them water soluble, while preserving the hydrophobic fullerene cage. This class of molecules have intriguing biomedical applications, including drug delivery, photodynamic therapy (PDT), antiviral and antimicrobial activity and reactive oxygen species (ROS)-scavenging abilities. In this Concept we discuss the synthesis and biomedical applications of water-soluble fullerene monoderivatives and their biological behavior based on their structures.

Direct Experimental Observations of Ion Distributions during Overcharging at the Muscovite‐Water Interface by Adsorption of Rb+ and Halides (Cl−, Br−, I−) at High Salinity

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Direct Experimental Observations of Ion Distributions during Overcharging at the Muscovite-Water Interface by Adsorption of Rb+ and Halides (Cl−, Br−, I−) at High Salinity

Classical electric double layer (EDL) models fail to describe ion distributions at charged solid-liquid interfaces at high salinity, where non-classical effects such as ion-ion correlations play a role. Here, the authors report the direct experimental determination of interfacial cation and anion distributions yielding new insights into the EDL structure and the associated adsorption isotherm data in the overcharging regime.


Abstract

Classical electric double layer (EDL) models have been widely used to describe ion distributions at charged solid-water interfaces in dilute electrolytes. However, the chemistry of EDLs remains poorly constrained at high ionic strength where ion-ion correlations control non-classical behavior such as overcharging, i. e., the accumulation of counter-ions in amounts exceeding the substrate's surface charge. Here, we provide direct experimental observations of correlated cation and anion distributions adsorbed at the muscovite (001)-aqueous electrolyte interface as a function of dissolved RbBr concentration ([RbBr]=0.01–5.8 M) using resonant anomalous X-ray reflectivity. Our results show alternating cation-anion layers in the EDL when [RbBr]≳100 mM, whose spatial extension (i. e., ~20 Å from the surface) far exceeds the dimension of the classical Stern layer. Comparison to RbCl and RbI electrolytes indicates that these behaviors are sensitive to the choice of co-ion. This new in-depth molecular-scale understanding of the EDL structure during transition from classical to non-classical regimes supports the development of realistic EDL models for technologies operating at high salinity such as water purification applications or modern electrochemical storage.

On The Nature of FeIV=Oaq in Aqueous Media: A DFT analysis

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On The Nature of FeIV=Oaq in Aqueous Media: A DFT analysis

Density functional calculations demonstrate that the FeIV=O2+ aq complexes form different analogous complexes according to the pH of the system.


Abstract

FeIV=Oaq is a key intermediate in many advanced oxidation processes and probably in biological systems. It is usually referred to as FeIV=O2+. The pKa's of FeIV=Oaq as derived by DFT are: pKa1=2.37 M06 L/6-311++G(d,p) (SDD for Fe) and pKa2=7.79 M06 L/6-311++G(d,p) (SDD for Fe). This means that in neutral solutions, FeIV=Oaq is a mixture of (H2O)4(OH)FeIV=O+ and (H2O)2(OH)2FeIV=O. The oxidation potential of FeIV=Oaq in an acidic solution, E0{(H2O)5FeIV=O2+/FeIII(H2O)6 3+, pH 0.0} is calculated with and without a second solvation sphere and the recommended value is between 2.86 V (B3LYP/Def2-TZVP, with a second solvation sphere) and 2.23 V (M06 L/Def2-TZVP without a second solvation sphere). This means that FeIV=Oaq is the strongest oxidizing agent formed in systems involving FeVIO4 2− even in neutral media.