Asymmetric Cross [10+2] Cycloadditions of 2-Alkylidene-1-indanones and Activated Alkenes under Phase-Transfer Catalysis

Isobenzofulvene species are versatile synthons in organic chemistry, which have been employed in diverse challenging higher-order cycloaddition reactions. Here, the first chemoselective and asymmetric cross [10+2] cycloaddition reaction between activated 2-alkylidene-1-indanones and a variety of electron-deficient alkenes has been developed, relying on the in situ generation of dearomative 1-hydroxyl isobenzofulvene anion intermediates under the catalysis of a newly designed bulky cinchona-derived phase-transfer compound. An array of fused frameworks with multifunctionalities were generally furnished in excellent diastereo- and enantioselectivity, even at 1 mol % catalyst loadings.     

Synthesis of Giant π-Extended Molecular Macrocyclic Rings as Finite Models of Carbon Nanotubes Displaying Enriched Size-Dependent Physical Properties

Bottom-up synthesis of π-extended macrocyclic carbon rings is promising for constructing length- and diameter-specific carbon nanotubes (CNTs). However, it is still a great challenge to realize size-controllable giant carbon macrocycles. Herein, a tunable synthesis of curved nanographene-based giant π-extended macrocyclic rings (CHBC[n]s; n=8, 6, 4), as finite models of armchair CNTs, is reported. Among them, CHBC[8] contains 336 all-carbon atoms and is the largest cyclic conjugated molecular CNT segment ever reported. CHBC[n]s were systematically characterized by various spectroscopic methods and applied in photoelectrochemical cells for the first time. This revealed that the proton chemical shifts, fluorescence, and electronic and photoelectrical properties of CHBC[n]s are highly dependent on the macrocycle diameter. The tunable bottom-up synthesis of giant macrocyclic rings could pave the way towards large π-extended diameter- and chirality-specific CNT segments.     

Multipolar Porphyrin-Triazatruxene Arrays for Two-Photon Fluorescence Cell Imaging

Two-photon excited fluorescent (TPEF) materials are highly desirable for bioimaging applications owing to their unique characteristics of deep-tissue penetration and high spatiotemporal resolution. Herein, by connecting one, two, or three electron-deficient zinc porphyrin units to an electron-rich triazatruxene core via ethynyl π-bridges, conjugated multipolar molecules TAT-(ZnP) _n (n=1–3) were developed as TPEF materials for cell imaging. The three new dyes present high fluorescence quantum yields (0.40–0.47) and rationally improved two-photon absorption (TPA) properties. In particular, the peak TPA cross section of TAT-ZnP (436 GM) is significantly larger than that of the ZnP reference (59 GM). The δ_TPA values of TAT-(ZnP)₂ and TAT-(ZnP)₃ further increase to 1031 and up to 1496 GM, respectively, indicating the effect of incorporated ZnP units on the TPA properties. The substantial improvement of the TPEF properties is attributed to the formation of π-conjugated quadrapole/octupole molecules and the extension of D -π-A-D systems, which has been rationalized by density function theory (DFT) calculations. Moreover, all of the three new dyes display good biocompatibility and preferential targeting ability toward cytomembrane, thus can be superior candidates for TPEF imaging of living cells. Overall, this work demonstrated a promising strategy for the development of porphyrin-based TPEF materials by the construction and extension of D -π-A-D multipolar array.     

Theoretical Study on Photoisomerization Mechanisms of Diphenyl-Substituted N,C-Chelate Organoboron Compounds

N,C-chelate organoboron compounds are widely employed as photoresponsive and optoelectronic materials due to their efficient photochromic reactivity. It was found in experiments that two diphenyl-substituted organoboron compounds, namely B(ppy)Ph₂ (ppy=2-phenylpyridyl) and B(iba)Ph₂ (iba=N-isopropylbenzylideneamine), show distinct photochemical reactivity. B(ppy)Ph₂ is inert on irradiation, whereas B(iba)Ph₂ undergoes photoinduced transformations, yielding BN-cyclohepta-1,3,5-triene via a borirane intermediate. In this work, the complete active space self-consistent field and its second-order perturbation (CASPT2//CASSCF) methods were used to investigate the photoinduced reaction mechanisms of B(ppy)Ph₂ and B(iba)Ph₂. The calculations showed that the two compounds isomerize to borirane in the same way by passing a transition state in the S₁ state and a conical intersection between the S₁ and S₀ states. The energy barriers in the S₁ state of 0.54 and 0.26 eV for B(ppy)Ph₂ and B(iba)Ph₂, respectively, were explained by analyzing the charge distributions of minima in S₀ and S₁ states. The results provide helpful insights into the excited-state dynamics of organoboron compounds, which could assist in rational design of boron-based photoresponsive materials.     

Adsorption property of congo red from aqueous solution by Cu-BTC/SiO 2 composite

The adsorption behavior of congo red from aqueous solution on Cu-BTC/SiO2 was investigated. Cu-BTC/SiO2 with mesoporous structure and large surface area was prepared by loading Cu-BTC into the mesoporous silica using in-situ synthesis method. The X-ray diffraction, scanning electron microscopy, and nitrogen adsorption–desorption analysis were used to characterize the structure and morphology of the prepared materials. The adsorption studies showed that the adsorption isotherm of congo red on Cu-BTC/SiO2 fitted well with Freundlich adsorption model and congo red is easy to be adsorbed by Cu-BTC/SiO2. The thermodynamic study showed that the adsorption behavior of congo red on Cu-BTC/SiO2 is an exothermic process at temperature under investigation.     

光诱导的二芳基烯丙醇氰甲基化合成δ-酮腈的反应研究

以二芳基烯丙醇与溴乙腈为原料,开发了一种可见光诱导的合成δ-酮腈的方法.控制实验的结果表明,该反应可能是通过自由基机理进行的,溴乙腈作为氰甲基自由基源参与到反应中.     

Cooperative effect of Fe and Ti species over Fe–Ti–Ox catalysts on the catalytic hydrolysis performance of hydrogen cyanide

FeO_x, TiO₂, and Fe–Ti–O_x catalysts were synthesized and used in the catalytic hydrolysis of hydrogen cyanide (HCN). Nearly 100% HCN conversion was achieved at 250 °C over the Fe–Ti–O_x catalyst. TiO₂ rutile was detected over TiO₂, but not over Fe–Ti–O_x, which suggested that the interaction between Fe and Ti species could inhibit the TiO₂ phase transition. Furthermore, the interaction between Fe and Ti species over Fe–Ti–O_x could promote the selectivity of NH₃ and CO. The mechanism of hydrolysis of HCN over FeO_x, TiO₂, and Fe–Ti–O_x can be given as follows: HCN + H₂O → methanamide → ammonium formate → formic acid → H₂O + CO.     

利用空间位阻和氢溢流协同作用促进5-羟甲基糠醛选择性加氢制备5-甲基糠醛

化学工业生产中，用氢气为还原剂，通过选择性加氢可以制备多种重要化学品。5-羟甲基糠醛是重要的生物质基平台化合物，而5-甲基糠醛是用途广泛的化学品。由5-羟甲基糠醛加氢得到5-甲基糠醛是一条非常理想的路径，但是选择性活化C-OH非常困难。本文设计并制备了Pt@PVP/Nb₂O₅(PVP: 聚乙烯吡咯烷酮)催化剂，该催化体系巧妙地结合了位阻效应、氢溢流和催化剂界面的电子效应，系统研究了该催化剂对5-羟甲基糠醛选择性加氢制备5-甲基糠醛催化性能，在最优条件下，5-甲基糠醛的选择性可达92%。利用密度泛函理论计算研究了5-羟甲基糠醛选择性加氢制备5-甲基糠醛反应路径。