Synthesis of Bis(silylene) Iron Chlorides and Their Catalytic Activity for Dinitrogen Silylation.

In this study, three tetracoordinated bis(silylene) iron(II) chlorides, namely, [SiCHRSi]FeCl2 (1) (R = H), (2) (R = CH3), and (3) (R = Ph), were synthesized through the reactions of the three different bis(silylene) ligands [LSiCHRSiL] (L = PhC(NtBu)2, L1 (R = H), L2 (R = CH3), L3 (R = Ph)) with FeCl2·(THF)1.5 in THF. The bis(silylene) Fe complexes 1-3 could be used as effective catalysts for dinitrogen silylation, with complex 3 demonstrating the highest turnover number (TON) of 746 equiv among the three complexes. The catalytic mechanism was explored, revealing the involvement of the pentacoordinated bis(dinitrogen) iron(0) complexes [SiCHRSi]Fe(N2)2(THF), (4)-(6), as the active catalysts in the dinitrogen silylation reaction. Additionally, the cyclic silylene compound 10 was obtained from the reaction of L1 with KC8. Single-crystal X-ray diffraction analyses confirmed the molecular structures of complexes 1-3 and 10 in the solid state.

Impact of the 2,2'-Bithienyl Framework on the Charge-Transfer Emission of Triarylborane-Based o,o'-Substituted Biaryls.

Two new triarylborane-based o,o'-substituted 2,2'-bithienyls, BT-BNMe 2 and BT-BNBn 2 , which contain BMes2 and NMe2/NBn2 groups at the 3,3'-positions, have been synthesized. Similar to the o,o'-substituted biphenyl analogues, BP-BNMe 2 and BP-BNBn 2 , which contain BMes2 and NMe2/NBn2 groups at the 2,2'-positions, the steric effect of the amino group has significant influence on the conformation of the 2,2'-bithienyl skeleton. The boryl and amino groups are located at the same side of 2,2'-bithienyls axis with a short B···N distance (3.63 Å) for the NMe2-substituted BT-BNMe 2 . On the contrary, the two substituents are arranged on the two different sides of the 2,2'-bithienyls axis for BT-BNBn 2 , which is modified with bulky NBn2. Despite the remarkable differences in the steric structure, the two 2,2'-bithienyls display fluorescence at close wavelengths, which is in sharp contrast to the much red-shifted fluorescence of BP-BNMe 2 than BP-BNBn 2 . The theoretical calculations demonstrated that the two 2,2'-bithienyls have close highest occupied molecular orbital-lowest unoccupied molecular orbital gaps in the excited state, which firmly support the experimental results. Thus, the parent main chain framework can exhibit great impact on the charge-transfer emission of o,o'-substituted biaryls.

A triarylborane-based biphenyl exhibiting abrupt fluorescence enhancement at a specific high temperature.

A triarylborane-based biphenyl, 4,4'-dibromo-2-dimesitylboryl-2'-(N,N-dimethylamino)biphenyl (Br2-BN-BPh), exhibits very unique temperature-dependent fluorescence behavior. Although Br2-BN-BPh is weakly emissive at room temperature, its fluorescence increases abruptly at a specific high temperature (68 °C in MOE, 88 °C in toluene). In addition, the fluorescence still remains very strong even after cooling to room temperature, providing the possibility of the fluorescence detection of a specific high temperature.

Charge-Transfer Emitting Triarylborane π-Electron Systems.

Triarylboranes have attracted significantly increasing research interest as a remarkable class of photoelectronic π-electron materials. Because of the presence of vacant p orbital on the B center, the boryl group is a very unique electron acceptor that exhibits not only electron-accepting ability through p-π* conjugation but also high Lewis acidity to coordinate with Lewis bases and steric bulk arising from the aryl substituent on the B center to get enough kinetic stability. Thus, the incorporation of a trivalent B element into π-conjugated systems is an efficient strategy to tune the electronic and stereo structures and thus the photoelectronic properties of π-electron systems. When an electron-donating group, such as amino, is present, triarylboranes would likely display intramolecular charge-transfer transitions. These kinds of molecules are often highly emissive. In addition, the geometry of the molecules has a great impact on the emission properties. In this Forum Article, we herein describe our recent progress on the charge-transfer emitting triarylborane π-electron systems with novel geometries, which include the lateral boryl-substituted π-system with amino groups at the terminal positions, the o,o'-substituted biaryl π-system with boryl and amino groups at the o,o'-positions, a triarylborane-based BODIPY system, and a B,N/S-bridged ladder-type π-system. We mainly put the emphasis on the molecular design concept, structure-property relationships, intriguing emission properties and great applications of the corresponding triarylborane π-systems.

Experimental computed tomography-guided vena cava puncture in pigs for percutaneous brachytherapy of middle mediastinal lymph node metastases.

BACKGROUND: Percutaneous brachytherapy is a valuable method for the treatment of lung cancer and mediastinal lymph nodes metastasis. However, in some of the metastatic lymph nodes in the middle mediastinum, the percutaneous approach cannot be used safely due to possible damage to surrounding anatomical structures. We established an animal model (group of 12 pigs) to assess the safety and feasibility of computed tomography (CT)-guided vena cava puncture. METHODS: Under CT guidance, an 18G needle was used to puncture the anterior wall of the anterior vena cava (AVC) in 12 pigs. The 18G needle was chosen as it is similar in size to the needles employed for clinical application in brachytherapy. The incidence of complications and vital signs was monitored during the procedure. Thoracotomy was performed to remove AVC specimens, which were analyzed for histological evidence of vessel wall damage and repair. RESULTS: Following postoperative enhanced CT, two animals were found to have a small pneumothorax (one being hemopneumothorax). The intraoperative oxygen saturation of both animals was not significantly decreased and was maintained at 93-100%. No animals developed mediastinal hematoma. Preoperative, intraoperative, and postoperative changes in blood pressure, heart rate, hemoglobin, and blood oxygen saturation were not significant. Histological evaluation of AVC specimens showed that by 7 days following the procedure, the endothelial layer was smooth with notable scar repair in the muscularis layer. CONCLUSIONS: CT performed after the procedure and histological preparations confirmed the safety of the procedure. This indicates that percutaneous brachytherapy for metastatic middle mediastinal lymph nodes can be carried out via the superior vena cava.

Source apportionment of polycyclic aromatic hydrocarbons in surface sediment of mud areas in the East China Sea using diagnostic ratios and factor analysis.

Polycyclic aromatic hydrocarbons (PAHs) and aliphatic hydrocarbons (AHs) have been quantified for surface sediments collected from the East China Sea (ECS). Our results showed that relatively high levels of PAHs and AHs occurred in both the inner and outer mud areas, while their concentrations at the control site were much lower. AHs for all samples were dominated by the unresolved complex mixture (UCM). Results from diagnostic ratios revealed that sedimentary PAHs were mainly originated from mixed combustion residues of biomass, coal, and petroleum. Combustion residues of petroleum and oil were responsible for the presence of high AHs concentrations. We also conducted factor analysis (FA) to further characterize the PAH and AH sources. Four factors were identified based on the loading of components and attributed to coal and wood combustion (Factor 1), traffic-related sources (Factor 2), petrogenic source (Factor 3) and natural gas combustion (Factor 4).