First-Principles Studies on the Efficient Photoluminescent Iridium(III) Complexes with C^∧NN Ligands

The electronic structures and photophysical properties of several homoleptic iridium complexes IrL3 with C∧NN ligands, including 1 (L = 3,6-diphenylpyridazine), 2 (L = 1,4-diphenylphthalazine), 3 (L = 3-phenyl-5H-indeno[1,2-c]pyridazine), and 4 (L = 3-phenylbenzo[h]cinnoline), are investigated using the density functional method. The comparison between the calculated results of the four complexes shows that the assumed complex 4 may possess higher photoluminescent quantum efficiency than complexes 1–3 and is the potential candidate to be an efficient green-emitting material. The photophysical properties of the assumed complex 3 can be comparable to that of experimentally found complex 1. For 1 and 3, the emission energies are nearly the same, consistent with their similar HOMO–LUMO energy gaps. Their emission characters are also similar and mainly dominated by one ligand. For 4 and the experimentally found complex 2, although they have similar HOMO–LUMO energy gaps, and their luminescent nature is nearly the same and dominated by the three ligands, the emission spectrum of 4 is blue-shifted as compared to that of 2

Superatomic Three-Center Bond in a Tri-Icosahedral Au₃₆Ag₂(SR)₁₈ Cluster: Analogue of 3c-2e Bond in Molecules

Probing the nature of electronic stability for ligand-protected gold clusters is important in gold chemistry. A thermally stable Au36Ag2(SR)18 nanocluster was synthesized recently. It has a D3h tri-icosahedral [Au30Ag2]12+ core with 20 valence electrons, which does not follow the magic number of gold superatoms. Herein, we propose a superatomic three-center bond to unveil its electronic stability. The [Au30Ag2]12+ core is viewed as a union of three face-fused superatoms, and chemical bonding analysis suggests a three-superatom-center two-electron (3sc-2e) bond for the octet rule of each superatom, which mimics the bonding framework of the D3h O32– molecule. Moreover, a liganded tri-icosahedral [Au27Pt3Ag2]11+ core with 18 valence electrons is predicted, and three 2sc-2e bonds are formed between each of two superatoms to satisfy the octet rule (analogue of D3h O3), indicating the flexibility of superatomic bonding. Such a superatomic three-center bond extends the community of superatomic bonding and gives a new perspective for superatom assembling

Superatomic Three-Center Bond in a Tri-Icosahedral Au₃₆Ag₂(SR)₁₈ Cluster: Analogue of 3c-2e Bond in Molecules

Probing the nature of electronic stability for ligand-protected gold clusters is important in gold chemistry. A thermally stable Au36Ag2(SR)18 nanocluster was synthesized recently. It has a D3h tri-icosahedral [Au30Ag2]12+ core with 20 valence electrons, which does not follow the magic number of gold superatoms. Herein, we propose a superatomic three-center bond to unveil its electronic stability. The [Au30Ag2]12+ core is viewed as a union of three face-fused superatoms, and chemical bonding analysis suggests a three-superatom-center two-electron (3sc-2e) bond for the octet rule of each superatom, which mimics the bonding framework of the D3h O32– molecule. Moreover, a liganded tri-icosahedral [Au27Pt3Ag2]11+ core with 18 valence electrons is predicted, and three 2sc-2e bonds are formed between each of two superatoms to satisfy the octet rule (analogue of D3h O3), indicating the flexibility of superatomic bonding. Such a superatomic three-center bond extends the community of superatomic bonding and gives a new perspective for superatom assembling

G‑Quadruplex-Proximized Aptamers (G4PA) Efficiently Targeting Cell-Surface Transferrin Receptors for Targeted Cargo Delivery

DNA-assembled multiaptamer systems have been demonstrated to significantly promote the aptamer capacity of binding cell-surface-expressed proteins. However, how to conveniently harness them for efficient transmembrane delivery of targets remains a challenge. Toward this goal, here we engineer a G-quadruplex-proximized aptamer (G4PA) system in which a DNA aptamer specific for transferrin receptor (TfR) is guided by a bimolecular G4 and assembles into a dimerized proximity form that well matches homodimeric TfR highly expressed on the cancer cell surface. This system displays a higher capacity for targeting cell-surface TfR than the monomeric aptamer and super transmembrane transportation of nucleic acid cargoes, which is comparable to that of conventional liposome transfection but overcomes the lack of targeting ability of the latter. The G4PA system is then applied to the targeted delivery of siRNA for PLK1 gene silencing in positive cells rather than negative controls, showing great promise for use in precise anticancer therapy

Tin Porphyrin-Based Nanozymes with Unprecedented Superoxide Dismutase-Mimicking Activities

As the oxidative stress is related to human aging and many diseases, a diversity of antioxidant biomimetic enzymes to eliminate reactive oxygen species in vivo and maintain the redox balance has attracted intensive attention. Of particular interest are superoxide dismutase (SOD)-mimicking artificial enzymes that bear inherent characteristics of natural counterparts but overcome their deficiencies in thermal and acidic stability. Inspired by the metallized active center of natural SODs, here, we engineered different groups of metalloporphyrins and found that Sn-metallized porphyrins can act as novel SOD mimics, in which Sn-metallized meso-tetra­(4-carboxyphenyl) porphine (Sn-TCPP) can more effectively catalyze the disproportionation of superoxide radical anions (•O2–) into hydrogen peroxide and oxygen. Especially, Sn-TCPP-based metal–organic frame nanozyme (Sn-PCN222) displays an unusually high catalytic activity that remarkably exceeds those of commonly used counterparts. Such unprecedented catalytic behaviors are proposed to depend on the Sn­(IV)/Sn­(II) transition at the center of Sn-TCPP. In addition, the metal–organic framework (MOF) nanozymes also display higher thermal and acidic stability than natural SODs. Interestingly, we find that Sn-complexed methylated tetra-(4-aminophenyl) porphyrin shows an aggregation-induced SOD activity in an acidic environment, whereas conventional SOD mimics do not function well in this case. Given these unique features, our reported Sn-porphyrin-based nanozymes would be potent alternatives for natural SODs to be widely used in clinical treatments of oxidative stress-related diseases

Calcium-Differentiated Cellular Internalization of Allosteric Framework Nucleic Acids for Targeted Payload Delivery

Target delivery systems have extensively shown promising applications in cancer therapy, and many of them function smartly by responding to the cancer cell microenvironment. Here, we for the first time report Ca2+-differentiated cellular internalization of 2D/3D framework nucleic acids (FNAs), enabling the engineering of a conceptually new target delivery system using an allosteric FNA nanovehicle. The FNA vehicle is subject to a 2D-to-3D transformation on the cancer cell surface via G-quadruplexes responding to environmental K+ and thereby allows its cell entry to be more efficiently promoted by Ca2+. This design enables the FNA vehicle to target cancer cells and selectively deliver an antisense strand-containing cargo for live-cell mRNA imaging. It would open new avenues toward targeted drug delivery and find extensive applications in precise disease treatment

Effect of lignin on laccase activities during the decolorization of dyes by <i>E. taxodii</i>.

<p>(A): RBV5. (B): DR5B. (C): DB38. (D): DB22. Dyes concentration: 100 mg/L. Lignin contents: ▪, 0 mg/L; •, 100 mg/L; ▴, 300 mg/L; ▾, 500 mg/L.</p

Hexaazatrinaphthalene-Based Covalent Triazine Framework-Supported Rhodium(III) Complex: A Recyclable Heterogeneous Catalyst for the Reductive Amination of Ketones to Primary Amines

The development of efficient and recyclable heterogeneous catalysts is an important topic. Herein, a rhodium­(III) complex Cp*Rh@HATN-CTF was synthesized by the coordinative immobilization of [Cp*RhCl2]2 on a hexaazatrinaphthalene-based covalent triazine framework. In the presence of Cp*Rh@HATN-CTF (1 mo l% Rh), a series of primary amines could be obtained via the reductive amination of ketones in high yields. Moreover, catalytic activity of Cp*Rh@HATN-CTF is well maintained during six runs. The present catalytic system was also applied for the large scale preparation of a biologically active compound. It would facilitate the development of CTF-supported transition metal catalysts for sustainable chemistry

Azo Dye Biodecolorization Enhanced by <i>Echinodontium taxodii</i> Cultured with Lignin

<div><p>Lignocellulose facilitates the fungal oxidization of recalcitrant organic pollutants through the extracellular ligninolytic enzymes induced by lignin in wood or other plant tissues. However, available information on this phenomenon is insufficient. Free radical chain reactions during lignin metabolism are important in xenobiotic removal. Thus, the effect of lignin on azo dye decolorization in vivo by <i>Echinodontium taxodii</i> was evaluated. In the presence of lignin, optimum decolorization percentages for Remazol Brilliant Violet 5R, Direct Red 5B, Direct Black 38, and Direct Black 22 were 91.75% (control, 65.96%), 76.89% (control, 43.78%), 43.44% (control, 17.02%), and 44.75% (control, 12.16%), respectively, in the submerged cultures. Laccase was the most important enzyme during biodecolorization. Aside from the stimulating of laccase activity, lignin might be degraded by E. taxodii, and then these degraded low-molecular-weight metabolites could act as redox mediators promoting decolorization of azo dyes. The relationship between laccase and lignin degradation was investigated through decolorization tests in vitro with purified enzyme and dozens of aromatics, which can be derivatives of lignin and can function as laccase mediators or inducers. Dyes were decolorized at triple or even higher rates in certain laccase–aromatic systems at chemical concentrations as low as 10 µM.</p></div