Reactivity of α-diazo sulfonium salts: rhodium-catalysed ring expansion of indenes to naphthalenes.

In the presence of catalytic amounts of the paddlewheel dirhodium complex Rh2(esp)2, α-diazo dibenzothiophenium salts generate highly electrophilic Rh-coordinated carbenes, which evolve differently depending on their substitution pattern. Keto-moieties directly attached to the azomethinic carbon promote carbene insertion into one of the adjacent C-S bonds, giving rise to highly electrophilic dibenzothiopyrilium salts. This intramolecular pathway is not operative when the carbene carbon bears ester or trifluoromethyl substituents; in fact, these species react with olefins delivering easy to handle cyclopropyl-substituted sulfonium salts. When indenes are the olefins of choice, the initially formed cyclopropyl rings smoothly open with concomitant departure of dibenzothiophene, enabling access to a series of 2-functionalized naphthalenes.

Synthesis of a Triangle-Fused Six-Pointed Star and Its Electrocatalytic CO2 Reduction Activity.

As electrocatalysts, molecular catalysts with large aromatic systems (such as terpyridine, porphyrin, or phthalocyanine) have been widely applied in the CO2 reduction reaction (CO2RR). However, these monomeric catalysts tend to aggregate due to strong π-π interactions, resulting in limited accessibility of the active site. In light of these challenges, we present a novel strategy of active site isolation for enhancing the CO2RR. Six Ru(Tpy)2 were integrated into the skeleton of a metallo-organic supramolecule by stepwise self-assembly in order to form a rhombus-fused six-pointed star R1 with active site isolation. The turnover frequency (TOF) of R1 was as high as 10.73 s-1 at -0.6 V versus reversible hydrogen electrode (vs RHE), which is the best reported value so far at the same potential to our knowledge. Furthermore, by increasing the connector density on R1's skeleton, a more stable triangle-fused six-pointed star T1 was successfully synthesized. T1 exhibits exceptional stability up to 126 h at -0.4 V vs RHE and excellent TOF values of CO. The strategy of active site isolation and connector density increment significantly enhanced the catalytic activity by increasing the exposure of the active site. This work provides a starting point for the design of molecular catalysts and facilitates the development of a new generation of catalysts with a high catalytic performance.

Metal-ion-determined geometrical configurations of metallo-cages with different emission properties.

The formation of metallo-cages is affected by a variety of factors such as the ligands, metals, and anions, among which the impact of metals with different binding capacities is particularly important, but has rarely been studied in three-dimensional metallo-cages. Herein, we report the design of truxene-centered terpyridine ligands and the self-assembly of a series of tetrameric metallo-cages. The utilization of metal ions with strong (Zn2+, Fe2+) or weak (Cd2+) binding strength afforded 3D metallo-cages with low symmetry or highly symmetric metallo-tetrahedra, respectively, possessing totally different geometrical configurations. In addition, their photophysical properties and host-guest chemical properties were investigated.

A truncated triangular prism constructed by using imidazole-terpyridine building blocks.

The construction of low-symmetry topological supramolecular structures using bistable building blocks remains challenging. We report an unusual truncated triangular prismatic cage with D3h symmetry using a ligand with both cis- and trans-configurations upon coordination with metal. This work provides new ideas and methods for the future synthesis of low-symmetry topological supramolecules.

Anion-Regulated Hierarchical Self-Assembly and Chiral Induction of Metallo-Tetrahedra.

The precise control over hierarchical self-assembly of superstructures relying on the elaboration of multiple noncovalent interactions between basic building blocks is both elusive and highly desirable. We herein report a terpyridine-based metallo-cage T with a tetrahedral motif and utilized it as an efficient building block for the controlled hierarchical self-assembly of superstructures in response to different halide ions. Initially, the hierarchical superstructure of metallo-cage T adopted a hexagonal close-packed structure. By adding Cl- /Br- or I- , drastically different hierarchical superstructures with highly-tight hexagonal packing or graphite-like packing arrangements, respectively, have been achieved. These unusual halide-ion-triggered hierarchical structural changes resulted in quite distinct intermolecular channels, which provided new insights into the mechanism of three-dimensional supramolecular aggregation and crystal growth based on macromolecular construction. In addition, the chiral induction of the metallo-cage T can be realized with the addition of chiral anions, which stereoselectively generated either PPPP- or MMMM-type enantiomers.

A novel Algorithm for Solving the Prize Collecting Traveling Salesman Problem based on DNA Computing.

DNA computing is a new pattern of computing that combines biotechnology and information technology. As a new technology born in less than three decades, it has developed at an extremely rapid rate, which can be attributed to its advantages, including high parallelism, powerful data storage capacity, and low power consumption. Nowadays, DNA computing has become one of the most popular research fields worldwide and has been effective in solving certain combinatorial optimization problems. In this study, we use the Adleman-Lipton model based on DNA computing for solving the Prize Collecting Traveling Salesman Problem (PCTSP) and demonstrate the feasibility of this model. Then, we design a simulation experiment of the model to solve some open instances of PCTSP. The results illustrate that the model can satisfactorily solve these instances. Finally, the comparison with the results of the Clustering Search algorithm and the Greedy Stochastic Adaptive Search Procedure/Variable Neighborhood Search method reveals that the optimal solutions obtained by this simulation experiment are significantly superior to those of the other two algorithms in all instances. This research also provides a method for proficiently solving additional combinatorial optimization problems.

Molecular characterization of a novel fungal alphaflexivirus reveals potential inter-species horizontal gene transfer.

Sclerotinia sclerotiorum is a notorious phytopathogenic fungus that harbors diverse mycoviruses. A novel positive-sense single-stranded RNA virus, Sclerotinia sclerotiorum alphaflexivirus 2 (SsAFV2), was isolated from the hypovirulent strain 32-9 of S. sclerotiorum, and its complete genome was determined. The SsAFV2 genome contains 7,162 nucleotides (nt), excluding the poly (A) structure, and is composed of four open reading frames (ORF1-4). ORF1 encodes a polyprotein that contains three conserved domains: methyltransferase, helicase, and RNA-dependent RNA polymerase (RdRp). The ORF3 putative encodes coat proteins (CP), with ORF2 and ORF4 encoding hypothetical proteins of unknown functions. Phylogenetic analysis revealed that SsAFV2 clustered with Botrytis virus X (BVX) based on multiple alignments of helicase, RdRp, and CP, but the methyltransferase of SsAFV2 was most closely related to Sclerotinia sclerotiorum alphaflexivirus 1, suggesting that SsAFV2 is a new member of the Botrexvirus genus within the Alphaflexiviridae family, and also revealed the occurrence of potential inter-species horizontal gene transfer events within the Botrexvirus genus during the evolutionary process. Our results contribute to the current knowledge regarding the evolution and divergence of Botrexviruses.

Tpy-Mn(II)-Tpy (Tpy = 2,2':6',2″-terpyridine)-Based Pentagonal Prism for Green Photodriven Oxidation.

In coordination-driven metal-organic cages, the transition metal ions are generally utilized as linkages. Employment of its unique properties with the aim of achieving specific applications still presents great challenges. Herein, we report a decametric metal-organic cage named pentagonal prism (Mn20LC10) based on Tpy-Mn(II)-Tpy connectivity (Tpy = 2,2':6',2″-terpyridine) in which Mn(II) serves as a linker and endows the resulting metal-organic cage with good photosensitivity. In the photooxidation of benzaldehyde, pentagonal prism Mn20LC10 showed a significantly increased level of 1O2 production, the fastest conversion time, good recyclability, and substrate versatility due to its greatly improved intersystem crossing ability. Notably, the abundant active sites of metal pentagonal prism Mn20LC10 enable its photooxidation under solvent-free and daylight conditions. This work provides approaches for the development of inexpensive, green, and low-cost photosensitizer systems.

Coordination-Driven Tetragonal Prismatic Cage and the Investigation on Host-Guest Complexation.

A coordination-driven host has been reported to encapsulate guests by noncovalent interactions. Herein, we present the design and synthesis of a new type of prism combining porphyrin and terpyridine moieties with a long cavity. The prism host can contain bisite or monosite guests through axial coordination binding of porphyrin and aromatic π interactions of terpyridine. The ligands and prismatic complexes were characterized by electrospray ionization mass spectrometry (ESI-MS), TWIM-MS, NMR spectrometry, and single-crystal X-ray diffraction analysis. The guest encapsulation was investigated through ESI-MS, NMR spectrometry, and transient absorption spectroscopy analysis. The binding constant and stability were determined by UV-Vis spectrometry and gradient tandem MS (gMS2) techniques. Based on the prism, a selectively confined condensation reaction was also performed and detected by NMR spectrometry. This study provides a new type of porphyrin- and terpyridine-based host that could be used for the detection of pyridyl- and amine-contained molecules and confined catalysis.

Discovery and Evolution of Six Positive-Sense RNA Viruses Co-infecting the Hypovirulent Strain SCH733 of Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum is a well-known phytopathogenic fungus with a wide host range. Identifying novel mycoviruses in phytopathogenic fungi is necessary to develop novel strategies for plant health protection and contribute to understanding the origin of viruses. Six new mycoviruses with positive single-stranded RNA genomes co-infecting the hypovirulent strain SCH733 of S. sclerotiorum were identified using a metatranscriptomic approach, and their complete genome sequences were molecularly determined. These mycoviruses belong to the following five families: Narnaviridae, Mitoviridae, Deltaflexviridae, Botourmiaviridae, and Ambiguiviridae. Three of these mycoviruses belong to existing International Committee on Taxonomy of Viruses (ICTV)-recognized species. Two of these newly identified mycoviruses have unique genomic features that are significantly different from those of all known mycoviruses. Phylogenetic analysis revealed that these six mycoviruses included close as well as distant relatives of known mycoviruses, thereby providing new insight into virus evolution and classification. Mycovirus horizontal transmission and elimination experiments revealed that Sclerotinia sclerotiorum narnavirus 5 is associated with hypovirulence of S. sclerotiorum, although we have not shown that it is independently responsible for the hypovirulence phenotype. This study broadens the diversity of known mycoviruses infecting S. sclerotiorum and provides a clue toward limiting hypovirulence in S. sclerotiorum.

Supramolecular cuboctahedra with aggregation-induced emission enhancement and external binding ability.

Beyond the AIE (aggregation-induced emission) phenomenon in small molecules, supramolecules with AIE properties have evolved in the AIE family and accelerated the growth of supramolecular application diversity. Inspired by its mechanism, particularly the RIV (restriction of intramolecular vibrations) process, a feasible strategy of constructing an AIE-supramolecular cage based on the oxidation of sulfur atoms and coordination of metals is presented. In contrast to previous strategies that used molecular stacking to limit molecular vibrations, we achieved the desired goal using the synergistic effects of coordination-driven self-assembly and oxidation. Upon assembling with zinc ions, S1 was endowed with a distinct AIE property compared with its ligand L1, while S2 exhibited a remarkable fluorescence enhancement compared to L2. Also, the single cage-sized nanowire structure of supramolecules was obtained via directional electrostatic interactions with multiple anions and rigid-shaped cationic cages. Moreover, the adducts of zinc porphyrin and supramolecules were investigated and characterized by 2D DOSY, ESI-MS, TWIM-MS, UV-vis, and fluorescence spectroscopy. The protocol described here enriches the ongoing research on tunable fluorescence materials and paves the way towards constructing stimuli-responsive luminescent supramolecular cages.

An organic-Ru2+ cluster-initiated dendritic faced metallo-octahedron and its unpredictable photoactivity.

Herein, a novel 3D metal-organic ligand consisting of a folded Ru(II)-connected tetrameric cycle and two sets of 60° juxtaposed bisterpyridine arms was synthesized and its complexation with Zn2+ gave rise to dendritic-faced metallo-octahedron 6. Remarkably, octahedron 6 displayed unexpected photosensitization ability that could produce singlet oxygen (1O2) under white light irradiation.

Aggregation-Induced Emission Metallocuboctahedra for White Light Devices.

Materials for organic light-emitting devices which exhibit superior emission properties in both the solution and solid states with a high fluorescence quantum yield have been extensively sought after. Herein, two metallocages, S1 and S2, were constructed, and both showed typical aggregation-induced emission (AIE) features with intense yellow fluorescence. By adding blue-emissive 9,10-dimethylanthracene, pure white light emission can be produced in the solution of S1 and S2. Furthermore, due to the remarkable AIE feature and good fluorescence quantum yield in the solid state, metallocages are highly emissive in the solid state and can be utilized to coat blue LED bulbs or integrate with blue-emitting chips to obtain white light. This study advances the usage of metallocages as practical solid-state fluorescent materials and provides a fresh perspective on highly emissive AIE materials.

New Enhanced Method for Determination of Trace Sulfamethodxazole Based on the Fluorescence Behaviors of Cyclodextrins in Water Solutions.

The widespread occurrence of sulfonamides (SAs) in the environment water has rasied great concerns about their potential to antibiotics resistance. In this study, the fluorescence behaviors of sulfamethoxazole (SMZ) representing certain properties of the SAs mixed with three different kinds of cyclodextrins (CDs) in water solutions were investigated, respectively. The result reported that the shapes of the fluorescence peak and its position for the SMZ that were mixed with the CDs were almost the same as those of the standard SMZ, respectively. In addition, compared with the identical control sample the fluorescence of SMZ mixed with each of the CD was greatly enhanced. Therefore, a new simple, and sensitive spectrofluorimetric method for the determination of SMZ was established in water solutions. and the dynamic linear ranges varied from 0.01 to 0.7 mg/L with the detection limit of 7.1 ng/L. And the correlation coefficient was more than 99.9%. Significantly, this new method was successfully applied to direct determination of SMZ in pharmaceutical compounds. Moreover, the results showed that the SMZ could separately form the 1:1 supramolecular compound with each of the CD.

Reinforced Topological Nanoassemblies: 2D Hexagon-Fused Wheel to 3D Prismatic Metallo-Lamellar Structure with Molecular Weight of 119 K Daltons.

By a precise metallo-ligand design, the advanced coordination-driven self-assembly could succeed in the preparation of giant molecular weight of the metallo-architectures. However, the synthesis of a single discrete high-molecular-weight (>100 K Da) structure has not been demonstrated due to the insurmountable synthetic challenge. Herein, we present a two-dimensional wheel structure (W1) and a gigantic three-dimensional dodecagonal prism-like architecture (P1), which were generated by multicomponent self-assembly of two similar metallo-organic ligands and a core ligand with metal ions, respectively. The giant 2D-suprastructure W1 with six hexagonal metallacycles that fused to the central spoke wheel was first achieved in nearly quantitative yield, and then, directed by introducing a meta-substituted coordination site into the key ligand, the supercharged (36 Ru2+ and 48 Cd2+ ions) double-decker prismatic structure P1 with two wheel structure W1s serve as the surfaces and 12 connectivities serve as the edges, where a molecular weight up to 119 498.18 Da was accomplished. The expected molecular composition and size morphology was unequivocally characterized by nuclear magnetic resonance, mass spectrometry, and transmission electron microscopy investigations. The introduction of a wheel structure is able to add considerable stability and complexity to the final architecture. These well-defined scaffolds are expected to play an important role in the functional materials field, such as molecular encapsulation and medicine sustained release.

Aza-ortho-Quinone Methide and Its Conjugated Acid: Reactivity, Stability and Acidity.

Aza-o-quinone methides and their conjugated acids are reactive drug metabolites that might react with nucleophilic sites of DNAs and proteins to cause cancer or immune responses, and their reactivity with water is the key information to judge if these metabolites are harmful in living systems. For the first time, aza-o-quinone methide (1) and its conjugated acid (2) are observed by laser flash photolysis, and their reactivity, stability and acidity in water are determined.

Novel methods for the rapid detection of trace tetracyclines based on the fluorescence behaviours of Maillard reaction fluorescent nanoparticles.

The Maillard reaction and its fluorescent products have attracted widespread attention in the field of food safety and biology. Herein, the novel Maillard reaction fluorescent nanoparticles (MRFNs) as a fluorescent probe were synthesized via a "green" method with simple technical processes. In addition, the effects of tetracycline (TC) and chlorotetracycline (CTC) representing certain properties of tetracyclines (TCs) on the fluorescence behaviour of MRFNs were studied, respectively. The present study showed that the fluorescence intensity of MRFNs greatly enhanced with a linear increase in the CTC concentration. However, with the gradual increase in the TC concentration, the intensity of MRFNs tended to significantly decrease linearly. Based on this, novel fluorescence analysis methods for the simple and rapid detection of TC and CTC in water bodies were established, respectively. Significantly, the proposed detection methods were successfully adopted for detecting TC and CTC in some environmental water samples. Besides, the possible mechanisms for TC-induced fluorescence quenching and CTC-induced fluorescence enhancement of MRFNs were also discussed, respectively.

Precise Self-Assembly of Molecular Four- and Six-Pointed Stars.

A novel metal-organic ligand (MOL 2) has been prepared by linking two V-shaped bis-terpyridines with one X-shaped tetrakis-terpyridine through the stable connectivity. The complexation between MOL 2, X-shaped tetrakis-terpyridine, and Zn2+ gave rise to a supramolecular C6-symmetrical six-pointed star quantitatively. In addition, a mixture of MOL 2, K-shaped tetrakis-terpyridine, and Zn2+ afforded a C2-symmetrical four-pointed star. These metallo-supramolecular architectures were adequately characterized by NMR, ESI-MS, TWIM-MS, and TEM analyses.

Geometrically Complementary Self-Assembly of a Hexarhomboid Architecture from Two Ruthenium(II)-Organic Building Blocks.

A shape-persistent metallosupramolecular multirhomboid that inlays a hexarhomboid polygon in a three-lobed flat structure was prepared by means of coordination-driven self-assembly. The key ligands were synthesized by a "reaction on complex" strategy that becomes accessible to troublesome metalloorganic ligand L3. The formation here consists of four different starting components and two metal ions. Complementarity of the shape and size drives molecular puzzling and results in the multicomponent, quantitative self-assembled construct.

Metallaoctahedron Derived from the Self-Assembly of Tetranuclear Metal-Organic Ligands.

Construction of 3D terpyridine-based metallopolyhedra remains challenging because of the linear coordination geometry of ⟨tpy-MII-tpy⟩ connectivity. A progressive strategy is made by assembling tetranuclear terpyridyl metal-organic ligands to afford a novel regular octahedron, whose structure was established by NMR, electrospray ionization mass spectrometry, traveling-wave ion-mobility mass spectrometry, atomic force microscopy, and transmission electron microscopy. This strategy provides an efficient method for the construction of 3D terpyridine-based metallopolyhedra.