Mass measurements in the endpoint region of the rp-process at SHIPTRAP

The Penning-trap mass spectrometer SHIPTRAP was designed for precision mass measurements of radionuclides produced in fusion–evaporation reactions. The latest measurement campaign covered heavy nuclei (A>90) related to the astrophysical rapid proton capture process. The masses of 34 neutron-deficient radionuclides have been measured since February 2006 with relative uncertainties between 5×10⁻⁸ and 1×10⁻⁷. Furthermore, the use of an octupolar RF excitation for the time-of-flight ion-cyclotron-resonance technique was investigated and an increase of the resolving power by a factor of ten was observed in agreement with simulations. This will allow to resolve isomeric states with excitation energies of a few 10 keV only.      

Thermophysical properties of Ni-Nb and Ni-Nb-Sn bulk metallic glass-forming melts by containerless electrostatic levitation processing

The containerless high-temperature high vacuum electrostatic levitation (ESL) technique was used for the determination of thermo-physical properties of the binary eutectic alloy, Ni_59.5Nb_40.5, and the ternary alloy Ni₆₀Nb_34.8Sn_5.2. The thermo-physical properties measured were density, specific heat over hemispherical total emissivity, surface tension and viscosity. The density for both the melts was found to be higher than that predicted by the rule of mixtures. This was attributed to strong attractive interaction between the constituents. The temperature dependent specific heat capacity of the binary alloy was determined by fitting with TEMPUS results. The hemispherical total emissivity was estimated to be 0.27. Using the specific heat data and the hemispherical total emissivity, the enthalpy and entropy of fusion were calculated for the binary alloy. The viscosities for both the alloys were fit with the Vogel-Fulcher-Tammann equation to obtain the fragility parameter. The surface tension for the binary alloy showed an anomalous positive gradient while that of the ternary alloy showed a small negative gradient with temperature.     

A General Catalytic Hydroamidation of 1,3‐Dienes: Atom‐Efficient Synthesis of N‐Allyl Heterocycles,Amides, and Sulfonamides

Transition‐metal‐catalyzed hydroamination reactions are sustainable and atom‐economical C N bond‐forming processes. Although remarkable progress has been made in the inter‐ and intramolecular amination of olefins and 1,3‐dienes, related intermolecular reactions of amides are still much less known. Control of the regioselectivity without analogous telomerization is the particular challenge in the catalytic hydroamidation of alkenes and 1,3‐dienes. Herein, we report a general protocol for the hydroamidation of electron‐deficient N‐heterocyclic amides and sulfonamides with 1,3‐dienes and vinyl pyridines in the presence of a catalyst derived from [{Pd(π‐cinnamyl)Cl}₂] and ligand L7 or L10 . The reactions proceeded in good to excellent yield with high regioselectivity. The practical utility of our method is demonstrated by the hydroamidation of functionalized biologically active substrates. The high regioselectivity for linear amide products makes the procedure useful for the synthesis of a variety of allylic amides.     

On the aspect of plane of appearance of Jahn-Teller and Renner-Teller intersections in tetra-atomic system—A case study with HCNO+

A search for configuration space with well-defined topological (Berry) phases corresponding to Jahn-Teller (JT) conical intersection (CI) and Renner-Teller (RT) parabolic intersection (PI) in the linear tetra-atomic molecular system on introduction of bending demonstrates the interesting aspect that these potential intersections may appear in the molecular plane as well as out of the molecular plane. While understanding this aspect is important for following the class of phenomena led by potential intersections, till date, studies on molecular systems, including pairs such as (C₂H₂⁺, HCNH) and (N₂H₂⁺, HBNH⁺), have not been able to clarify the issue. The present article includes calculation of nonadiabatic coupling terms involving four low-lying states of slightly bent HCNO⁺, a motivated choice of tetra-atomic with all four different atoms, to study this aspect associated with JT-CI and RT-PI in a slightly bent linear system. The plane of appearance of these effects has been advocated to be related to the electronic configuration of the concerned states of the molecular system.     

Photophysics of Glycosylated Derivatives of a Chlorin,Isobacteriochlorin and Bacteriochlorin for Photodynamic Theragnostics: Discovery of a Two‐photon‐absorbing Photosensitizer

The photophysical properties of a chlorin, isobacteriochlorin and bacteriochlorin built on a core tetrapentafluorophenylporphyrin (TPPF₂₀) and the nonhydrolyzable para thioglycosylated conjugates of these chromophores are presented. The photophysical characterization of these compounds was done in three different solvents to correlate with different environments in cells and tissues. Compared with TPPF₂₀ other dyes have greater absorption in the red region of the visible spectrum and greater fluorescence quantum yields. The excited state lifetimes are from 3 to 11 ns. The radiative and nonradiative rate constants for deactivation of the excited state were estimated from the fluorescence quantum yield and excited state lifetime. The data indicate that the bacteriochlorin has strong absorption bands near 730 nm and efficiently enters the triplet manifold. The isobacteriochlorin has a 40–70% fluorescence quantum yield depending on solvent, so it may be a good fluorescent tag. The isobacteriochlorins also display enhanced two‐photon absorption, thereby allowing the use of 860 nm light to excite the compound. While the two‐photon cross section of 25 GM units is not large, excitation of low chromophore concentrations can induce apoptosis. The glycosylated compounds accumulate in cancer cells and a head and neck squamous carcinoma xenograft tumor model in mice. These compounds are robust to photobleaching.     

Aldol reaction of kojic acid using alumina supported base catalyst and enzymatic resolution of the aldol adduct by CALB

An efficient and ecofriendly aldol reaction of kojic acid with aldehydes using a heterogeneous reusable catalyst (alumina modified with base) is developed. Enzymatic hydrolytic resolution of the racemic acetylated aldol adduct 2 was achieved using lipase from Candida antarctica type B (CALB). The key feature of this enzymatic resolution is that regioselective deacetylation of ester derived from the primary alcohol located away from the stereocentre occurred in the presence of adjacent secondary acetate.     

Hydrogen‐Bond‐Driven Controlled Molecular Marriage in Covalent Cages

A supramolecular approach that uses hydrogen‐bonding interaction as a driving force to accomplish exceptional self‐sorting in the formation of imine‐based covalent organic cages is discussed. Utilizing the dynamic covalent chemistry approach from three geometrically similar dialdehydes ( A , B , and D ) and the flexible triamine tris(2‐aminoethyl)amine ( X ), three new [3+2] self‐assembled nanoscopic organic cages have been synthesized and fully characterized by various techniques. When a complex mixture of the dialdehydes and triamine X was subjected to reaction, it was found that only dialdehyde B (which has OH groups for H‐bonding) reacted to form the corresponding cage B₃X₂ selectively. Surprisingly, the same reaction in the absence of aldehyde B yielded a mixture of products. Theoretical and experimental investigations are in complete agreement that the presence of the hydroxyl moiety adjacent to the aldehyde functionality in B is responsible for the selective formation of cage B₃X₂ from a complex reaction mixture. This spectacular selection was further analyzed by transforming a nonpreferred (non‐hydroxy) cage into a preferred (hydroxy) cage B₃X₂ by treating the former with aldehyde B . The role of the H‐bond in partner selection in a mixture of two dialdehydes and two amines has also been established. Moreover, an example of unconventional imine bond metathesis in organic cage‐to‐cage transformation is reported.     

C4 Cumulene and the Corresponding Air‐Stable Radical Cation and Dication

A neutral C₄ cumulene 1 that includes a cyclic alkyl(amino) carbene (cAAC), its air‐stable radical cation 1 ^.+, and dication 1 ²⁺ have been synthesized. The redox property of 1 ^.+ was studied by cyclic voltammetry. EPR and theoretical calculations show that the unpaired electron in 1 ^.+ is mainly delocalized over the central C₄ backbone. The commercially available CBr₄ is utilized as a source of dicarbon in the cumulene synthesis.