Mechanistic Study on CpRh(III)-Catalyzed [3 + 2] Annulation of Aniline Derivatives with Vinylsilanes: A DFT Study.

The rhodium(III)-catalyzed reaction of aniline derivatives that contain a pyrimidine-directing group with vinylsilanes results in the formation of C3-substituted indoline derivatives. The reaction path and formation of the indoline product with density functional theory calculations were analyzed. This study reveals that the whole catalysis can be characterized in the following stages: (I) C-H activation via concerted metalation deprotonation, (II) 2,1-vinylsilane insertion, (III) deprotonation of the NH amide proton, (IV) the oxidation of Ag+, and (V) reductive elimination. These steps are kinetically and thermodynamically feasible for experimental realization under mild conditions, and the insertion step with a barrier of 22.0 kcal/mol should not only be the critical step of regioselectivity but also the rate-determining step during the whole catalysis. Computations reveal that the Ag+ oxidation can accelerate the reductive elimination step after the formation of natural intermediate, thus highlighting the role of Ag+ as a catalytic promoter for the oxidatively induced reactivity of the Rh catalyst in C3-substituted indoline synthesis.

Theoretical and experimental investigation of doping M in ZnSe (M = Cd, Mn, Ag, Cu) clusters: optical and bonding characteristics.

The optical and bonding characteristics of doping ZnSe quantum dots (QDs) were investigated. Cd-, Mn-, Ag- and Cu-doped ZnSe were synthesized in aqueous solution. Theoretically, the intensity of the Cd-Se bond was similar to that of the Zn-Se bond, which illustrates that Cd can be doped into ZnSe materials at any ratio. We found that Mn-Se bonding was stronger than Zn-Se bonding. Ag-doped ZnSe nanoclusters show the same bonding and configuration as Cu-doped ZnSe. Moreover, Cd can be doped into ZnSe using both the substitution- and vacancy-doping method. For Mn-doped ZnSe clusters, small amounts of Mn impurity lead to stronger bonding with Se, but larger amounts of Mn impurity led to the formation of a Mn-Mn metal bond. The theoretical results show that it is difficult to form a vacancy-doping cluster for Mn-doped ZnSe materials. In experiments, the absorption and photoluminescence (PL) spectral wavelengths of Mn-doped ZnSe nanocrystals were the same as those of pure ZnSe nanocrystals, showing that the Mn impurity is not doped into ZnSe nanocrystals. Ag- and Cu-doped ZnSe nanocrystals have the same PL characteristics. The doping of an impurity is related to the solubility product, and not the bonding intensity.

Tuning the emission of aqueous Cu:ZnSe quantum dots to yellow light window.

Synthesis of internally doped Cu:ZnSe QDs in an aqueous solution still suffers from narrow tunable emissions from the blue to green light window. In this work, we extended the emission window of aqueous Cu:ZnSe QDs to the yellow light window. Our results show that high solution pH, multiple injections of Zn precursors, and nucleation doping strategy are three key factors for preparing yellow emitted Cu:ZnSe QDs. All these factors can depress the reactivity of CuSe nuclei and Zn monomers, promoting ZnSe growth outside CuSe nuclei rather than form ZnSe nuclei separately. With increased ZnSe QD size, the conduction band and nearby trap state energy levels shift to higher energy sites, causing Cu:ZnSe QDs to have a much longer emission.

Aqueous synthesis of nontoxic Ag2Se/ZnSe quantum dots designing as fluorescence sensors for detection of Ag(I) and Cu(II) ions.

We reported the synthesis of water-soluble and nontoxic Ag(2)Se/ZnSe Quantum Dots (QDs) using for fluorescence sensors. The influences of various experimental conditions including the synthesis pH, types of ligand, feed ratios, and the refluxed time on the growth process and fluorescence of QDs were investigated in detail. Under optimal conditions, Ag(2)Se/ZnSe QDs show a single emission peak around 490 nm with the maximal photoluminescence (PL) quantum yield (QYs) of 13.7 %. As-prepared Ag(2)Se/ZnSe QDs can be used for detection of Ag(II) and Cu(II). The detection limits are 1 × 10(-6) mol/L to 5 × 10(-5) mol/L for Ag (I), and 2 × 10(-6) mol/L to 1.10 × 10(-4) mol/L for Cu(II).

Simultaneous Enhancement of Intracellular Optical Imaging and Photothermal Therapeutic Response by Octaarginine-Modified Fluorescent Dye Doped Pd@Ag@SiO2(RITC) Multifunctional Nanoparticles.

In the work, a novel multifunctional silica-based nanoplatform (Pd@Ag@SiO2(RITC)-R8) for bioimaging and photothermal therapy (PTT) of cancer cells has been developed. The Pd@Ag nanosheets encapsulated inside silica can act as effective near-infrared (NIR) absorbers for cancer photothermal therapy. Fluorescent dye, rhodamine B isothiocyanate (RITC), was covalently doped into the silica network to provide the capacity for optical imaging. After amine modification, the Pd@Ag@SiO2(RITC)-NH2 can be further conjugated with octaarginine (R8, a cell penetrating peptide) for enhancing the uptake of nanoparticles by cells. Confocal fluorescent images and flow cytometry analysis revealed that R8-conjugated nanoparticles (Pd@Ag@SiO2(RITC)-R8) were taken up by cells more efficiently. Correspondingly, the optical imaging and photothermal therapeutic efficiency of Pd@Ag@SiO2(RITC)-R8 upon cancer cells were also raised due to their higher cellular uptake when compared with that of Pd@Ag@SiO2(RITC)-NH2. Our results indicate that these multifunctional Pd@Ag@SiO2(RITC)-R8 may have great potential for applications in imaging-guided cancer photothermal therapy.

Theoretical Investigations on the Rh(III)-Catalyzed Oxidative C-H Activation/Annulation of Salicylaldehydes with Masked Enynes: Mechanism Insights and Regioselectivity Origins.

The mechanism underlying the rhodium(III)-catalyzed reaction of the C-H alkenylation/annulation reaction of salicylaldehydes with enynes has been thoroughly investigated using DFT calculations. Based on mechanistic studies, our focus primarily lies on the regioselectivity of asymmetric alkynes inserting into the Rh-C bond and the involvement of the auxiliary group OAc- in these reactions. Our theoretical study uncovers that, with acetate assistance, a stepwise SN2' cyclization, 1,3-Rh migration, ß-H elimination, and reductive elimination process occur. Furthermore, we also explore the role of substitution at Cα (CH3 vs H) in the reaction. As demonstrated in this work, these findings are applicable to other related reactions.

Degradation and dechlorination of trichloroacetic acid induced by an in situ 222 nm KrCl* excimer radiation.

Since the coronavirus disease 2019 (COVID-19) pandemic epidemic, the excessive usage of chlorinated disinfectants raised the substantial risks of disinfection by-products (DBPs) exposure. While several technologies may remove the typical carcinogenic DBPs, trichloroacetic acid (TCAA), their application for continuous treatment is limited due to their complexity and expensive or hazardous inputs. In this study, degradation and dechlorination of TCAA induced by an in situ 222 nm KrCl* excimer radiation as well as role of oxygen in the reaction pathway were investigated. Quantum chemical calculation methods were used to help predict the reaction mechanism. Experimental results showed that UV irradiance increased with increasing input power and decreased when the input power exceeded 60 W. Decomposition and dechlorination were simultaneously achieved, where around 78% of TCAA (0.62 mM) can be eliminated and 78% dechlorination within 200 min. Dissolved oxygen showed little effect on the TCAA degradation but greatly boosted the dechlorination as it can additionally generate hydroxyl radical (•OH) in the reaction process. Computational results showed that under 222 nm irradiation, TCAA was excited from S0 to S1 state and then decayed by internal crossing process to T1 state, and a reaction without potential energy barrier followed, resulting in the breaking of C-Cl bond and finally returning to S0 state. Subsequent C-Cl bond cleavage occurred by a barrierless •OH insertion and HCl elimination (27.9 kcal/mol). Finally, the •OH attacked (14.6 kcal/mol) the intermediate byproducts, leading to complete dechlorination and decomposition. The KrCl* excimer radiation has obvious advantages in terms of energy efficiency compared to other competitive methods. These results provide insight into the mechanisms of TCAA dechlorination and decomposition under KrCl* excimer radiation, as well as important information for guiding research toward direct and indirect photolysis of halogenated DBPs.

Polymer Composite Thermoforming: Ultrasonic-Assisted Optimization for Enhanced Adhesive Performance in Automotive Interior Components.

Dual-component epoxy resins are widely used for bonding different materials in automotive interior processing. However, due to the complexity and variability of automotive interior parts, uneven temperature distribution on curved surfaces during the thermoforming process can lead to uneven thermal stress distribution, damaging the interior components. This study focuses on addressing the damage issues caused by uneven thermal stress distribution during the thermoforming of automotive interior components. By monitoring the temperature and strain on the adhesive surface of the interior components during processing, using sensors and combining the readings with a finite element simulation, damage to the adhesive during processing was simulated. Based on this, a segmented thermoforming method for the model surface was employed, but it was found that this method did not significantly reduce the level of damage to the adhesive during application. Building upon the segmented simulation, significant results were achieved by applying temperature modulation at a certain frequency to adjust the damage of the interior components during processing. The techniques used in this study successfully reduced the unevenness of the adhesive surface temperature, improved the performance of the adhesive during application through segmented optimization and the application of ultrasound-assisted techniques, and markedly reduced the manufacturing process's energy consumption.

A theoretical study based on DFT calculations on the different influence of functional groups on the C-H activation process via Pd-catalysed ß-X elimination.

We have performed a series of theoretical calculations for palladium-catalyzed ß-X elimination reactions. The DFT calculation combined with energy decomposition analysis shows the determining factors of reactivity. Such as, the elemental composition, the structure of different functional groups and the stronger steric repulsions contribution.

Theoretical analysis of expanded porphyrins: Aromaticity, stability, and optoelectronic properties.

Expanded porphyrin systems are capable of binding a variety of substrates due to their increased cavity size and aromatic nature, holding important applications as magnetic resonance imaging contrast agents and as sensitizers for photodynamic therapy. It is there of fundamental interest to know the photoelectrical properties of expanded porphyrins using quantum chemistry calculations. In this work, we theoretically designed and screened a series of expanded porphyrins by incorporating terthiophene (TTH) and dithienothiophene (DTT) moieties. Our calculations showed that all the designed molecules exhibit excellent optoelectronic performance than the reference molecule. It is suggested that the porphyrin molecule with TTH moiety has better stability than the one with DTT moiety. Finally, we demonstrated that molecule 2 features with TTH moiety and the inverted selenophene ring outperform other molecules because it exhibits increased HOMO-LUMO gap, planar geometry, and strengthened aromaticity. We expect that this work can provide theoretical guidelines for the design of novel porphyrin materials.

Diatom Biodiversity and Speciation Revealed by Comparative Analysis of Mitochondrial Genomes.

Diatoms (Bacillariophyta) constitute one of the most diverse and ecologically significant groups of phytoplankton, comprising 100,000-200,000 species in three classes Bacillariophyceae, Mediophyceae, and Coscinodiscophyceae. However, due to the limited resolution of common molecular markers including 18S rDNA, 28S rDNA, ITS, rbcL, and cox1, diatom biodiversity has not been adequately ascertained. Organelle genomes including mitochondrial genomes (mtDNAs) have been proposed to be "super barcodes" for distinguishing diatom species because of their rich genomic content, and the rapid progress of DNA sequencing technologies that has made it possible to construct mtDNAs with increasing throughout and decreasing cost. Here, we constructed complete mtDNAs of 15 diatom species including five Coscinodiscophyceae species (Guinardia delicatula, Guinardia striata, Stephanopyxis turris, Paralia sulcata, and Actinocyclus sp.), four Mediophyceae species (Hemiaulus sinensis, Odontella aurita var. minima, Lithodesmioides sp., and Helicotheca tamesis), and six Bacillariophyceae species (Nitzschia ovalis, Nitzschia sp., Nitzschia traheaformis, Cylindrotheca closterium, Haslea tsukamotoi, and Pleurosigma sp.) to test the practicality of using mtDNAs as super barcodes. We found that mtDNAs have much higher resolution compared to common molecular markers as expected. Comparative analysis of mtDNAs also suggested that mtDNAs are valuable in evolutionary studies by revealing extensive genome rearrangement events with gene duplications, gene losses, and gains and losses of introns. Synteny analyses of mtDNAs uncovered high conservation among species within an order, but extensive rearrangements including translocations and/or inversions between species of different orders within a class. Duplication of cox1 was discovered for the first time in diatoms in Nitzschia traheaformis and Haslea tsukamotoi. Molecular dating analysis revealed that the three diatom classes split 100 Mya and many diatom species appeared since 50 Mya. In conclusion, more diatom mtDNAs representing different orders will play great dividends to explore biodiversity and speciation of diatoms in different ecological regions.

Complete mitochondrial genome of Coscinodiscus granii (Coscinodiscophyceae, Bacillariophyta).

Coscinodiscus is a genus common in marine phytoplankton, with some species thought to have a significant negative ecological impact. However, the availability of their genome sequences is rather limited. Here, we assembled and annotated the first complete mitochondrial genome (mtDNA) of the species Coscinodiscus granii L.F.Gough 1905, as part of our efforts to gain a better understanding of the genetic characteristics of Coscinodiscus taxa at a genomic level. The circular mtDNA was 34,970 bp in length and encoded 60 genes, including 32 protein-coding genes (PCGs), 24 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and two conserved open reading frames (orfs). The overall GC content of C. granii mtDNA was 24.30%, which was slightly lower than that of C. wailesii (25.00%), the first species in the genus Coscinodiscus whose mtDNA has been reported, and higher than that of Melosira undulata (21.60%), the first species in the class Coscinodiscophyceae whose mtDNA has been reported. As expected for congeneric species, phylogenetic analysis using concatenated amino acid sequences of 27 shared PCGs suggested that C. granii has a closer evolutionary relationship with C. wailesii. Coscinodiscus was found to be monophyletic in the phylogeny. The complete mtDNAs of more Coscinodiscus species will facilitate the exploration of the evolutionary relationships of species in the Class Coscinodiscophyceae.

CASSCF/CASPT2 calculation of the low-lying electronic states of the CH3Se neutral radical and its cation.

Electronic states of the CH(3)Se and its cation CH(3)Se(+) have been studied using the complete active space self-consistent field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) methods in conjunction with the ANO-RCC(TZP) basis set. To investigate the Jahn-Teller effect on the CH(3)Se radical, C(s) symmetry was used for CH(3)Se in calculations. The results show that the Jahn-Teller effect is very small (69 cm(-1)) and the 1(2)A' state is slightly more stable than the 1(2)A'' state (8 cm(-1)). The CH(3)Se has been found to have a 1(2)A' ground state with a C-Se bond distance of 1.975 A. The computed C-Se stretching nu(6)(a') frequency is 554.1 cm(-1), which is in good agreement with the experimental values of 600 +/- 60 cm(-1). The calculations for CH(3)Se at 3.621 and 5.307 eV are attributed to 1(2)A' --> 2(2)A'(1(2)A(1)) and 1(2)A' --> 2(2)A'', respectively. The vertical and adiabatic ionization energies were obtained to compare with the PES data.

A theoretical study of the low-lying electronic states of the AlCCH radical and its ions.

The AlCCH radical is a photolysis product of the aluminum-acetylene adducts and has been considered as a molecule with potential interest in astrophysics. In this study, the low-lying electronic states of the AlCCH radical, cation, and anion have been studied by using complete active space self-consistent field and multiconfigurational second-order perturbation theory. The geometrical parameters, electron configurations, excitation energies, oscillator strengths, and harmonic vibrational frequencies are calculated in C(S) symmetry. For the X(1)Sigma(+) state of AlCCH, the calculated C-C and C-Al stretching modes are in good agreement with experimental reports. Moreover, the vertical excitation energy (T(v)) of 1(1)Pi is 3.68 eV, which is close to the experimental value of 3.57 eV. The electron transitions of AlCCH(+), X(2)Sigma(+) --> 1(2)Pi, X(2)Sigma(+) --> 2(2)Sigma(+), and X(2)Sigma(+) --> 1(2)Sigma(-), are predicted at 2.57, 4.51, and 4.61 eV, respectively. For AlCCH(-), the transition X(2)Pi --> 1(2)Sigma(-) occurs at 3.02 eV. The ionization potentials of AlCCH are computed in order to provide a theoretical guidance to the photoelectron spectrum of the AlCCH radical.

Seawater silicate fertilizer facilitated nitrogen removal via diatom proliferation.

Dissolved inorganic nitrogen (DIN) enrichment accompanied by silicate deficiency in seawater can promote dinoflagellate growth over diatom growth and induce further negative ecological consequences. Here, we propose an easily exercisable method for silicate fertilization as a remedy of eutrophication. In the laboratory, rice husk ash (RHA) released silicate and phosphate in an atomic ratio range of 38-113 without a significant influence on DIN. During incubations of silicate-limited waters, low-dose fertilization increased the diatom/dinoflagellate ratio by 1-5 times. With the high-dose fertilizer addition, DIN, with an initial concentration of 7.63 ±â€¯0.95 µmol l-1, was exhausted in three days, and the diatom abundance increased by 19 times on the 5th day. The silicate fertilization method presented here can be applied independently in eutrophicated waters for dinoflagellate suppression and dissolved nitrogen removal; this method could also work as a supplementary measure to existing nutrient (N, P) reduction and biomanipulation efforts.

Nutrient-limitation induced diatom-dinoflagellate shift of spring phytoplankton community in an offshore shellfish farming area.

As mariculture expands offshore in response to the increasing demand for seafood, a new set of ecological concerns arises. We report on presented phosphate and silicate deficiencies in spring in the Zhangzi Island area, northern Yellow Sea, used for farming scallops. Silicon limitation was observed at up to 77.3% of stations, with an average silicate concentration as low as 1.7 µM in March 2014. Average phosphate concentration decreased from 0.12 to 0.05 µM from March to May. Stoichiometric ratios and absolute concentrations indicate that 78%-90% of stations showed phosphate limitation. Correspondingly, the phytoplankton community shifted from predominately diatoms to dinoflagellates. The higher frequency of nutrient limitation in farmed areas, compared with unseeded areas and northern Yellow Sea in general, imply intensified bottom-up controls on scallop production. The "bottle-neck" effect of limited food availability in spring suggests that carrying capacity was originally overestimated, when calculated from annual primary production.

Theoretical studies on low-lying electronic states of cyanocarbene HCCN and its ionic states.

Geometries of 10, 7, and 6 low-lying states of the HCCN neutral radical, its anion and cation, were optimized by using the complete active space self-consistent field (CASSCF) method in conjunction with the aug-cc-pVTZ basis set, respectively. Taking the further correlation effects into account, the second-order perturbations (CASPT2) were carried out for the energetic correction. Vertical excitation energies (T(v)) at the ground state geometry of the HCCN neutral radical were calculated for 11 states. The results of our calculations suggest that the spin-allowed transitions of HCCN at 4.179, 4.395, 4.579, 4.727 and 5.506 eV can be attributed to X(3)A'' --> 2(3)A'', X(3)A'' --> (3)A', X(3)A --> 3(3)A'', X(3)A'' --> 2(3)A', and X(3)A'' --> 3(3)A', respectively. The singlet-triplet splitting gap of HCCN is calculated to be 0.738 eV. The vertical and adiabatic ionization energies were obtained to compare with the PES data. The results we obtained were consistent with the available experiment results.

A study of the hydrogen abstraction reactions of C2H radical with CH3CN, C2H5CN, and C3H7CN by dual-level generalized transition state theory.

The hydrogen abstraction reactions C2H + CH3CN --> products (R1), C2H + CH3CH2CN --> products (R2), and C2H + CH3CH2CH2CN --> products (R3) have been investigated by dual-level generalized transition state theory. Optimized geometries and frequencies of all the stationary points and extra points along the minimum-energy path (MEP) are performed at the BH&H-LYP and MP2 methods with the 6-311G(d, p) basis set, and the energy profiles are further refined at the MC-QCISD level of theory. The rate constants are evaluated using canonical variational transition state theory (CVT) with a small-curvature tunneling correction (SCT) over a wide temperature range 104-2000 K. The calculated CVT/SCT rate constants are in good agreement with the available experimental values. Our calculations show that for reaction R2, the alpha-hydrogen abstraction channel and beta-hydrogen abstraction channel are competitive over the whole temperature range. For reaction R3, the gamma-hydrogen abstraction channel is preferred at lower temperatures, while the contribution of beta-hydrogen abstraction will become more significant with a temperature increase. The branching ratio to the alpha-hydrogen abstraction channel is found negligible over the whole temperature range.

GNAQ mutation R183Q as a potential cause of familial Sturge-Weber syndrome: A case report.

Sturge-Weber syndrome (SWS) is a rare neurocutaneous disorder whose etiology remains unclear. To investigate the genetic contribution underlying this disease, the genetic variants of a 4-generation family with a history of SWS was analyzed in the present study. SWS was diagnosed in 3 of the family members (II-1, III-11 and IV-6). Sanger sequencing was performed to identify mutations in G protein subunit αq (GNAQ) and RAS p21 protein activator 1 exons in the 3 patients with SWS and other unaffected family members. Notably, a non-synonymous single-nucleotide variant at codon 183 on exon 4 of the GNAQ gene was identified as the only pathogenic site. This variant generated a substitution of arginine (R) with glutamine and resulted in a change of function of the encoded protein. Evolutionary conservation analysis revealed that the mutated residue 183 (R) of GNAQ is highly conserved across several vertebrate species. Furthermore, an immunofluorescence staining assay demonstrated that the substitution of arginine with glutamine resulted in a change in the sub-cellular localization of the GNAQ recombinant protein in vitro. These findings may aid in the development of novel diagnostic markers and/or therapeutic targets for the treatment of patients with familial SWS.

Theoretical study on alkali-metal doped N3H3 complexes: an in-depth understanding of the origin of electride and alkalide and their large nonlinear optical properties.

By doping the model complexant N3H3 with one or two lithium atoms, the geometrical and electronic structures as well as static electric properties of the resulting Li(N3H3), (N3H3)Li' and Li(N3H3)Li' complexes can be explored using the B3LYP, BHandHLYP, CAM-B3LYP and MP2 methods. All three complexes, especially Li(N3H3), were found to have large first hyperpolarizabilities (ß 0). Meanwhile, Li(N3H3) and Li(N3H3)Li' exhibited electride and alkalide characteristics, respectively. The dependance of electric properties of alkalide Li(N3H3)Li' on the alkali atoms involved and the complexant layer number were revealed by investigating the related M(N3H3)Li' and Li(N3H3)M' (M = Na and K), and Li(N3H3) n Li' (n = 2, 3) systems. Note that the ß 0 value of alkalide M(N3H3)M' increased not only with the increasing atomic number of the M'(-) anion but also with that of the M(+) cation, which differs from previously reported cases. In addition, the electric properties of the Li(N3H3)Li' alkalide were enhanced by increasing the complexant layers. However, it was found that both the complexant-complexant and the complexant-Li' interactions reduced with the addition of N3H3 layers, so no stable structures were found for larger Li(N3H3) n Li' complexes. Graphical Abstract Geometrical and electronic structures as well as static electric properties of Li(N3H3), (N3H3)Li' and Li(N3H3)Li' complexes were explored using B3LYP, BHandHLYP, CAM-B3LYP and MP2 methods.