乙酸/氧气法高效合成取代卟啉

卟啉在结构上可视为是由4个吡咯类亚甲基的α-碳原子通过次甲基桥互联而形成的大分子杂环化合物,具有高度共轭结构。 随着卟啉与金属的配合物即金属卟啉的催化特性受到广泛关注,取代卟啉的高效合成日益显示出重要的学术和应用价值。 但是现有的丙酸法和乙酸/硝基苯法存在卟啉收率低、环境污染严重等问题,导致取代卟啉的成本居高不下,限制了其广泛应用。 本文利用乙酸/氧气法,在120 ℃下控制反应物浓度为0.24 mol/L,并在反应第一阶段(前30 min)通入氧气,得到四(4-溴苯基)卟啉(化合物d),产率高达53.8%。 该方法是高效合成取代卟啉的新方法,卟啉骨架形成和氧化两个反应同时进行,方法简单、绿色且收率高,有望大幅度降低取代卟啉的合成成本。     

Atropisomers of meso Tetra(N-Mesyl Pyrrol-2-yl) Porphyrins: Synthesis,Isolation and Characterization of All-Pyrrolic Porphyrins

Atropisomerism has been observed in a variety of biaryl compounds and meso-aryl substituted porphyrins. However, in porphyrins, this phenomenon had been shown only with o-substituted 6-membered aromatic groups at the meso-position. We show herein that a 5-membered heteroaromatic (N-mesyl-pyrrol-2-yl) group at the meso-position leads to atropisomerism. In addition, we report a ‘one-pot’ synthetic route for the synthesis of ‘all-pyrrolic’ porphyrin (APP) with several N-protection groups (Boc, Cbz, Ms and Ts). Among these groups, we found that only the Ms group gave four individually separable atropisomers of meso-tetra(N-Ms-pyrrol-2-yl) porphyrin. Furthermore, the reductive removal of Cbz- was achieved to obtain meso-tetra(pyrrol-2-yl) porphyrin. Thus, our synthetic procedure provides an easy access to a group of APPs and stable atropisomers, which is expected to expand the application of novel APP-based materials.     

一种天线分子与卟啉染料自组装在染料敏化太阳能电池中的应用

以卟啉分子H2-pTCPP作为基础染料,通过配位自组装的方法将天线分子S3修饰到染料结构中。结果表明经天线分子修饰后染料敏化太阳能电池器件的整体性能得到了极大的改善。天线效应有效地提高了器件的光子捕获能力,光电流得到了显著的提高,并且电荷复合行为也得到了明显的抑制。基于H2-pTCPP的电池器件显示了1.18%的转换效率,而经过天线分子修饰后的Mn-pTCPP+S3显示了2.64%的转换效率,性能提高了1.2倍。     

Structurally Interesting Diarymethane Derivatives from Securidaca inappendiculata

Securines A—E, three dimeric diarymethane derivatives ( 1 — 3 ) and two enantiomeric diarymethane derivative monomers ( 4 and 5 ), were isolated and characterized from the medicinal plant Securidaca inappendiculata. Compounds 1 and 2 are a pair of enantiomeric diarymethane derivative dimers, and compound 3 is a mesomeric diarymethane derivative dimer. Their structures were determined by a combination of spectroscopic data, X‐ray crystallography, electronic circular dichroism (ECD) analysis, and computational ECD calculations. Dimeric compounds 1 — 3 showed moderate antiplasmodial activities with IC₅₀ values of 0.9, 1.4, and 1.5 μM, respectively.     

On‐Surface Synthesis and Characterization of Triply Fused Porphyrin–Graphene Nanoribbon Hybrids

On‐surface synthesis offers a versatile approach to prepare novel carbon‐based nanostructures that cannot be obtained by conventional solution chemistry. Graphene nanoribbons (GNRs) have potential for a variety of applications. A key issue for their application in molecular electronics is in the fine‐tuning of their electronic properties through structural modifications, such as heteroatom doping or the incorporation of non‐benzenoid rings. In this context, the covalent fusion of GNRs and porphyrins (Pors) is a highly appealing strategy. Herein we present the selective on‐surface synthesis of a Por–GNR hybrid, which consists of two Pors connected by a short GNR segment. The atomically precise structure of the Por–GNR hybrid has been characterized by bond‐resolved scanning tunneling microscopy (STM) and noncontact atomic force microscopy (nc‐AFM). The electronic properties have been investigated by scanning tunneling spectroscopy (STS), in combination with DFT calculations, which reveals a low electronic gap of 0.4 eV.     

Conformational Dynamics of Monomer‐ versus Dimer‐like Features in a Naphthalenediimide‐Based Conjugated Cyclophane

The design and synthesis of an enantiomeric pair of 1,8‐diethynylanthracene‐bridged naphthalenediimide (NDI)‐based cyclophanes ( Cyclo‐NDI s) are reported. Each enantiomer of Cyclo‐NDI exhibits a circularly polarized luminescence signal with a relatively large luminescence dissymmetry factor (g_lum=±8×10^?3). We have further investigated the modulation of through‐space electronic communication between co‐facially oriented NDIs in a discrete Cyclo‐NDI with changes in the temperature. Tuning of the electronic communication results from the conformational transformation of monomer‐ versus dimer‐like features of Cyclo‐NDI , as confirmed by UV/Vis, fluorescence, circular dichroic, and NMR spectroscopic analysis. The temperature‐dependent optical response in the Cyclo‐NDI through the conformational transformation could be utilized as a highly sensitive and reversible optical thermometer in a wide temperature range (100 to ?80 °C).     

Rational Development of Remote C−H Functionalization of Biphenyl: Experimental and Computational Studies

A simple and efficient nitrile‐directed meta‐C?H olefination, acetoxylation, and iodination of biaryl compounds is reported. Compared to the previous approach of installing a complex U‐shaped template to achieve a molecular U‐turn and assemble the large‐sized cyclophane transition state for the remote C?H activation, a synthetically useful phenyl nitrile functional group could also direct remote meta‐C?H activation. This reaction provides a useful method for the modification of biaryl compounds because the nitrile group can be readily converted to amines, acids, amides, or other heterocycles. Notably, the remote meta‐selectivity of biphenylnitriles could not be expected from previous results with a macrocyclophane nitrile template. DFT computational studies show that a ligand‐containing Pd–Ag heterodimeric transition state (TS) favors the desired remote meta‐selectivity. Control experiments demonstrate the directing effect of the nitrile group and exclude the possibility of non‐directed meta‐C?H activation. Substituted 2‐pyridone ligands were found to be key in assisting the cleavage of the meta‐C?H bond in the concerted metalation–deprotonation (CMD) process.     

Conformational Panorama and Chirality Controlled Structure–Energy Relationship in a Chiral Carboxylic Acid Dimer

Chirality recognition in dimers of tetrahydro‐2‐furoic acid (THFA) was studied in a conformer‐specific manner using rotational spectroscopy and theoretical approaches. THFA shows a strong preference for the trans‐ over the cis‐COOH configuration. Two drastically different scenarios are possible for the detectable (THFA)₂: a kinetically preferred dimer bound by feeble interactions between two trans THFAs or a thermodynamically favored dimer with a double hydrogen‐bonded ring structure between two cis subunits. To identify the conformers responsible for the extremely dense rotational spectra observed, it was essential not only to locate several hundred homo/heterochiral (THFA)₂ minima in ab initio calculations but also to evaluate the energetic connectivities among the minima. The study further reveals an interesting chirality dependent structure–energy ordering relationship. A method for enantiomeric excess (ee) determination of THFA is presented using a recently proposed chiral self‐tag approach.     

Unique Thia‐Baeyer–Villiger‐Type Oxidation of Dibenzothiophene Sulfoxides Derivatives

The present research has demonstrated that selective C?S bond cleavages of dibenzothiophene and its derivatives are feasible by thia‐Baeyer–Villiger type oxidation, i. e. the oxygen insertion process within a sulfoxide‐carbon linkage, in the presence of porphyrin iron (III) and by ultraviolet irradiation originating from sunlight, high pressure Hg‐lamp or residentially germicidal ultraviolet lamp under very mild conditions. This reaction with tert‐butylhydroperoxide at 30.0 °C leads to dibenzo[1,2]oxathiin‐6‐oxide ( PBS ) in 83.2 % isolated yield or its hydrated products, 2‐(2‐hydroxyphenyl)‐benzenesulfinic derivatives ( HPBS ) in near 100 % yield based HPLC data. PBS and HPBS are a type of biological products detected on the C?S bond cleavage step through various oxidative biodesulfurization ( OBDS ) pathways, and are useful synthetic intermediates and fine chemicals. These observations may contribute on understanding delicately molecular aspect of OBDS in the photosynthesis system, expanding the C‐S cleavage chemistry of S‐heterocyclic compounds and approaching toward biomemic desulfurization with respect to converting sulfur contaminants to chemically beneficial blocks as needed and performing under the ambient conditions.