Synthesis of a novel one-handed helical poly(phenylacetylene) bearing poly(l-lactide) side chains

The living ring-opening polymerization of l-lactide was carried out by using organocatalyst to synthesize the molecular weight controlled poly(l-lactide) with an phenylacetylenyl end group (HCCPLLA), then the homopolymerization of HCCPLLA was performed by using two different rhodium catalysts. Low molecular weight poly-PLLA₆-1 (M_w,SEC-MALLS = 46,700) was synthesized by using Rh(nbd)BPh₄ as the catalyst, and higher molecular weight poly-PLLA₆-2 (M_w,SEC-MALLS = 471,000) was synthesized by using the [Rh(nbd)Cl]₂/Et₃N catalyst system. Then high molecular weight poly-PLLA₂₀, poly-PLLA₂₉, and poly-PLLA₆₈ were successfully synthesized by using the [Rh(nbd)Cl]₂/Et₃N catalyst system. The α values of the poly-PLLAs using [Rh(nbd)Cl]₂/Et₃N catalyst system were all in the range of 0.6–0.8, this means that these polymers possess linear flexible chain. It is concluded that [Rh(nbd)Cl]₂/Et₃N was more suitable for the synthesis of the cylindrical polymer brush, poly-PLLA with high molecular weight. The analyses of the CD spectra indicated that poly-PLLA possesses a predominantly one-handed helical conformation, temperature and solvents had significant influences on the helical structure of poly-PLLA.     

Synthesis and characterization of polylactide functionalized polyacetylenes

The paper deals with the synthesis and polymerization of novel poly(l-lactide)-derived acetylene monomers and the analysis of the thermal properties of the formed graft copolymers. Poly(l-lactide) macromonomers with different acetylene end groups were prepared using stannous octanoate as a catalyst in the presence of various hydroxyacetylenes. Next, the well-characterized macromonomers were subjected to polymerization using [{RhCl(nbd)}₂]/Et₃N and [RuCl₂(CH–o–OiPrC₆H₄)(IMesH₂)] to obtain graft copolymers. Investigation of these graft copolymers by GPC and NMR spectroscopy revealed the presence of some poly(l-lactide) formed as a side product during the ring opening polymerization of l-lactide. The thermal stability of the polymeric materials has been studied as a function of the polyacetylene backbone substituents and the length of poly(l-lactide) side chains. Introducing polyacetylene into polyester increased the polymer stability. The thermal degradation behavior of the synthesized materials depends on the length of poly(l-lactide) chains and also on l-lactide homopolymer impurities in the graft copolymers.     

o-Semiquinonato and o-iminosemiquinonato rhodium complexes. EPR study of the reactions in coordination sphere of rhodium

Chemical exchange saturation transfer (CEST) processes in aqueous systems are quantified by evaluation of z-spectra, which are obtained by acquisition of the water proton signal after selective RF presaturation at different frequencies. When saturation experiments are performed in vivo, three effects are contributing: CEST, direct water saturation (spillover), and magnetization transfer (MT) mediated by protons bound to macromolecules and bulk water molecules. To analyze the combined saturation a new analytical model is introduced which is based on the weak-saturation-pulse (WSP) approximation. The model combines three single WSP approaches to a general model function. Simulations demonstrated the benefits and constraints of the model, in particular the capability of the model to reproduce the ideal proton transfer rate (PTR) and the conventional MT rate for moderate spillover effects (up to 50% direct saturation at CEST-resonant irradiation). The method offers access to PTR from z-spectra data without further knowledge of the system, but requires precise measurements with dense saturation frequency sampling of z-spectra. PTR is related to physical parameters such as concentration, transfer rates and thereby pH or temperature of tissue, using either exogenous contrast agents (PARACEST, DIACEST) or endogenous agents such as amide protons and -OH protons of small metabolites.     

Rhodium-catalyzed direct oxidative cross-coupling of 2-aryl pyridine with benzothiazoles

A rhodium-catalyzed cross-coupling reaction of 2-aryl pyridine and benzothiazoles via dual C–H bond functionalization has been developed in the presence of copper salts. The reaction system provides a new approach to heterobiaryl species, which are ubiquitous in pharmaceuticals and nature products.     

Rhodium-catalyzed tandem aldol condensation–Robinson annulation between aldehydes and acetone: synthesis of 3-methylcyclohexenones

A simple catalytic, redox-neutral access to 3-methylcyclohexenones has been developed via rhodium catalysis in the presence of an amine additive and Ag₂CO₃. This process utilized simple aldehydes and acetone as substrates and tolerates a variety of functional groups. Disubstituted phenols were isolated in moderate yields when Cu(OAc)₂ was employed as an oxidant.     

Keggin‐type Polyoxometalates [PW11O39MCl]5– with Noble Metals (M = Rh and Ir): Novel Synthetic Entries and ESI‐MS Directed Reactivity Screening

A new synthetic entry to iridium Keggin‐type polyoxometalate complexes from [PW₁₁O₃₉]^7– and K₃[IrCl₆] under harsh conditions is reported. The complex [PW₁₁O₃₉IrCl]^5– ( 1 ^5–) featuring an IrCl functionality was obtained in high yield and characterized by NMR spectroscopic and ESI‐MS techniques. The presence of Li⁺ (3–4 M) is essential for a quantitative yield of 1 ^5–. The reactivities of 1 ^5– and its rhodium analogue [PW₁₁O₃₉RhCl]^5– in ligand substitution at the noble metal site were studied. Thiocyanate coordination successfully yielded (Bu₄N)₅[PW₁₁O₃₉M(SCN)] [M = Rh ( 2a ), Ir, ( 3a )]. In both cases, the SCN ligands are coordinated by sulfur atoms, according to ¹³C NMR and IR spectroscopic data. Gas‐phase fragmentation reactions of compounds 2a and 3a were also investigated by collision‐induced dissociation (CID) experiments. Reaction of [PW₁₁O₃₉RhCl]^5– with NaN₃ resulted in Cl^– to OH^– replacement accompanied by the liberation of the RhCl fragment, whereas 1 ^5– proved unreactive with NaN₃. Attempts to coordinate NO₂^– are adversely affected by competing noble metal excision with formation of free [PW₁₁O₃₉]^7–.     

Rhodium(III)‐Catalyzed C?C and C?O Coupling of Quinoline N‐Oxides with Alkynes: Combination of C?H Activation with O‐Atom Transfer

[Cp*Rh^III]‐catalyzed C H activation of arenes assisted by an oxidizing N O or N N directing group has allowed the construction of a number of hetercycles. In contrast, a polar N O bond is well‐known to undergo O‐atom transfer (OAT) to alkynes. Despite the liability of N O bonds in both C H activation and OAT, these two important areas evolved separately. In this report, [Cp*Rh^III] catalysts integrate both areas in an efficient redox‐neutral coupling of quinoline N‐oxides with alkynes to afford α‐(8‐quinolyl)acetophenones. In this process the N O bond acts as both a directing group for C H activation and as an O‐atom donor.     

Characterization Reaction of Benzoyl Methylene Triphenylphosphorane and Benzoyl Methylene Tri-n-buthylphosphorane with Rhodium (III) and Ruthenium (III) Chloride. A Multinuclear NMR Study

The reactions of title ylide (C 6 H 5 ) 3 PCHCOC 6 H 5 , (BPPY) and (n-C 4 H 9 ) 3 PCHCOC 6 H 5 , (BBuPY) with rhodium (III) and ruthenium (III) chloride in equimolar ratios using methanol as solvent have yielded crystals of [(BPPY-H) 3 Rh], ( 1 ), [(BPPY) 2 Ru(MeOH) 2 (H 2 O) 2 ]Cl 3 , ( 2 ), and [Ru(BBuPY)Cl 2 S 2 ]Cl (S = H 2 O or CH 3 OH), ( 3 ). The IR and 1 H, 13 C, 31 P NMR data of the products were obtained. Analytical and NMR data are consistent with the cyclometalated and octahedral structures for ( 1 ) and ( 2 ) respectively.     

Dy^(3+)掺杂Lu_(2)O_(3)和Y_(2)O_(3)单晶光纤下转换荧光测温性能EI北大核心CSCD

稀土倍半氧化物单晶光纤材料凭借超高的熔点(~2400℃)、稳定的物化性能以及灵活的结构被认为是极具潜力的高温传感介质。本文采用激光加热基座(LHPG)法,成功生长了透明无开裂Dy^(3+)离子掺杂的倍半氧化物单晶光纤Lu_(2)O_(3)和Y_(2)O_(3)。依据Dy^(3+)离子的^(4)I_(15/2)和^(4)F_(9/2)能级为一对热耦合能级对(TCLs),测试得到了430~520 nm波长范围内的下转换荧光光谱。荧光强度比(FIR)结果显示,晶体在298~673 K温度范围内的荧光强度具有良好的温度相关性。其中Dy∶Lu_(2)O_(3)在该范围内的最大相对灵敏度和绝对灵敏度分别为0.97%·K^(-1)(315 K)和1.62×10^(-4) K^(-1)(673 K),展现出更为优异的温度传感性能。