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A unique decarbonylation of an amino acid derivative catalytic system has been established via palladium-catalyzed C-C bond and C-N bond dual activations. By employing 8-aminoquinoline as the directing group, this transformation has been found to facilitate the high chemoselectivity to decarbonylation of amino acid derivatives rather than intramolecular deamination or cross-dehydrogenative coupling reactions. This method provides a straightforward avenue for constructing diverse functionalized amide compounds in good to excellent yields. We proposed a possible reaction pathway that may go through the C-C bond and C-N bond dual activations on the basis of the mechanistic studies.

Heparin was employed as the stabilizing agent in the synthesis of peroxidase-mimicking Pd nanoparticles. The heparin-capped Pd nanozyme can act as both the signal amplifier and the selective binder of protamine. The most efficient nanozyme with the mean size of 3.5 nm consists of 70.8% metallic Pd 0 and 29.2% Pd 2+ species. Enzyme kinetic studies show that the K m values are 0.036 mM for 3,3',5,5'-tetramethylbenzidine and 78 mM for H 2 O 2 . Protamine shows strong affinity to the heparin-capped Pd nanozyme, and induces an apparent aggregation of the nanoparticles. This results in a significant inhibition of the peroxidase-mimicking activities. Hence, the oxidation of TMB by H 2 O 2 to a blue product with a maximum absorption at 652 nm is suppressed. Based on this finding, a photometric assay is developed for the determination of protamine. The linear response is in the concentration range 0.02 ~ 0.8 μg mL -1 , and the limit of detection is 0.014 μg mL -1 . This assay presents high selectivity toward other biological substances. Graphical abstract Highly active and selective Pd nanozyme was synthesized through adopting heparin as the capping agent for quantitative determination of protamine.

Glutathione-capped Pd nanoparticles with a size of 1.4-3.5 nm are facilely synthesized for peroxidase nanomimetics. The molar ratio of [Na2PdCl4]/[GSH] greatly affects the physicochemical properties including particle sizes, surface charge states and enzymatic activities. The most efficient Pd-based nanozyme, consisting of approximately 57% metallic Pd(0) species with an average diameter of 2.6 nm, exhibits the K(m) value of 0.068 mM toward 3,3',5,5'-tetramethylbenzidine and 156 mM toward hydrogen peroxide. Ag(+) selectively binds to Pd(0) species through metallophilic interactions and induces an apparent aggregation of Pd nanoparticles. This is the first report that Ag(+) significantly inhibits the peroxidase mimicking activity of Pd nanoparticles. A Pd-based nanozyme is employed to explore colorimetric detection of Ag(+) with the limit of detection of 1.2 nM. This developed sensing system is potentially applicable for quantitative detection of Ag(+) in drinking water as well as Ag nanoparticles in aqueous solution.

Highly active subnano Pd clusters were synthesized using i-motif DNA as the template through characterization via ESI MS, DLS, XPS, UV-vis, and FTIR. It is indicated that Pd1-Pd5 clusters are generated at a [Pd]/[base] ratio of 0.2, Pd8 to Pd9 clusters are generated at a [Pd]/[base] ratio of 0.5, and large nanoparticles with the size about 2.6 nm are formed at a [Pd]/[base] ratio of 2.0. The i-motif-stabilized Pd8-Pd9 clusters show high catalytic activity toward the reduction of 4-nitrophenol with a relative rate constant value of 2034 min(-1) (mM Pd)(-1). DFT calculations disclose that the unique structure of the i-motif with consecutive hemiprotonated CH(+)·C pairs can efficiently ligate Pd ions at the N3 sites of cytosines and that the synthesized Pd clusters consist of metallic Pd atoms as well as positively charged Pd that is ligated by nucleobases, which is capable of facilitating the activation of the nitryl group of 4-nitrophenol. This work suggests a promising pathway to preparing subnano metal catalysts with enhanced catalytic activity using programmable DNA scaffolds.

Both conventional heating and ultrasound effect on the cyclopalladated ferrocenylimines catalyzed Suzuki reaction of phenylboronic acid with a range of arylhalides in neat water was investigated. Heterogenous reaction of electron-withdrawing arylchlorides with phenylboronic acid could also result in good yields by using Cat. 2. It was found that the ultrasonic irradiation could dramatically accelerate the Suzuki reaction to achieve comparable results.

NADH, composed of metal binding, charged and redox groups, acts as a "three-in-one" template to construct peroxidase mimicking Pd nanoclusters (NCs). The physicochemical properties of Pd NCs are highly dependent upon the molar ratio of [NADH]/[Na2PdCl4], thereby contributing to distinct peroxidase mimicking activities. The ultrasmall Pd nanozyme that contains 30% metallic Pd0 species, exhibits the Km of 0.063 mM toward TMB and 80.8 mM toward H2O2. Notably, addition of heparin enables the enhancement of its peroxidase-like activity in neutral media. A colorimetric assay was well-established at pH 6 for quantitatively monitoring heparin in aqueous solution and biological fluid. The linear response lies in the range of 0.5–25 µg mL−1, with the limit of detection of 1.1 ng mL−1. This work paves a promising pathway to manufacture highly active enzyme mimetics with desirable physicochemical properties. [ABSTRACT FROM AUTHOR]

Selective hydrogenation of α, β-unsaturated aldehydes has always been a hot research topic owing to favorable thermodynamics in C C hydrogenation. In this work, a series of Pd/SnO 2 nanocatalysts were facilely synthesized under mild conditions, via the reduction of Na 2 PdCl 4 by dimethylaminoborane. Under galvanostatic electrolysis at 3.33 mA cm−2 for 8 h, the selective conversion of cinnamaldehyde (CAL) was achieved over Pd/SnO 2 -coated carbon fiber in neutral phosphate buffer, giving the cinnamyl alcohol (COL) selectivity of 78.85% at the conversion of 84.88%. The Pd/SnO 2 nanocatalysts outperform commercial Pd/C catalysts, showing high COL selectivity and faradaic efficiency. The cathodic reduction potential of CAL over Pd 4·3 /SnO 2 occurs at −0.92 V. The SnO 2 support is beneficial to promote the C O adsorption of CAL and lower the HER activity of Pd nanocatalysts, thereby contributing to superior activity of Pd 4·3 /SnO 2 for selective hydrogenation of CAL. [Display omitted] • Pd/SnO 2 nanocatalyst realizes electrocatalytic hydrogenation of cinnamaldehyde. • The SnO 2 support facilitates the adsorption of C O bond for cinnamaldehyde. • SnO 2 is beneficial to lower the HER activity of Pd as compared to commercial Pd/C. • Pd/SnO 2 achieves high conversion, C O selectivity and faradaic efficiency. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Controlled synthesis of noble metal nanocatalysts with desirable catalytic activities remains a great challenge. Inspired by electron-rich functional groups and supramolecular assembly properties of natural nucleotides, herein we propose a versatile approach to construct Pd nanocatalysts through employing seven nucleotides as both electron donors and stabilizers. The catalytic performance of nucleotide-Pd complexes are greatly associated with the chemical structures of nucleobases as well as the number of phosphate groups. Guanosine 5′-triphosphate-Pd complexes possess high activities in the hydrogenation reduction of 4-nitrophenol assisted by NaBH 4 , with the relative rate constant of 7770 min−1 mM−1 at 25 °C. Pd(II)-coordinated nucleotides are also promising in NaBH 4 -mediated degradation of organic dyes. This work demonstrates a green and facile process to construct Pd nanocatalysts containing abundant active sites under the assistance by natural nucleotides. [ABSTRACT FROM AUTHOR]

• Electrochemical-induced switch toward C=O bond in Pd-catalyzed CAL hydrogenation. • The COL selectivity is up to 90% in neutral pH with considerable faraday efficiency. • The self-standing Pd cathode outperforms other catalysts for CAL hydrogenation. • Large π-conjugated system is decisive to C=O selectivity. • Organic solvent retards total hydrogenation of semi-hydrogenated products. It is particularly challengeable to achieve C=O selectivity for Pd catalysts in thermal catalytic hydrogenation of cinnamaldehyde (CAL). This work offers a new electrochemical strategy that enables an unexpected switch toward C=O bond for CAL hydrogenation, based on the specific interaction between CAL and electrolyte-modulated Pd surface. Under galvanostatic electrolysis, guanosine 5′-monophosphate-modulated Pd electrode affords a record cinnamyl alcohol (COL) selectivity of 90.3% in neutral catholyte with no sacrifice of CAL conversion, showing the faradaic efficiency of 68.2%. It is of great interest to find that the aromatic moiety of CAL determines the preferential activation toward C=O bond over Pd surface under electric field. It is reported for the first time that selective hydrogenation of α, β-unsaturated aldehydes can be altered by electrochemical environment located between Pd electrode and surrounding electrolyte involving alkali cation along with organic solvent. [Display omitted] [ABSTRACT FROM AUTHOR]