Measurement of the ground state 2n pickup probability for 28Si+68Zn and its role in sub-barrier fusion enhancement

The ground state and excited state transfer yields for the 2-neutron pickup channel in the ²⁸Si+⁶⁸Zn system have been measured explicitly. The recoil mass separator at the nuclear Science Centre, New Delhi was used for the measurement. A NaI(T1) detector was used for detecting the deexcitation γ’s from the transfer products. The kinematic coincidence technique was employed for the transfer measurement. Simplified coupled channels calculations show that out of all transfer channels the major contribution to the sub-barrier enhancement comes from the ground state 2 neutron pickup channel with a ground state Q-value of+1.83 MeV.     

Straightforward Synthesis of 3‐Aminothiophenes Using Activated Amides

Herein, we describe a facile approach towards the synthesis of diversely substituted 3‐aminothiophenes. A wide range of functional groups can be incorporated at the C(2), C(4), and C(5) positions of the thiophenes, and this route is also suitable for the synthesis of fused bicyclic heterocycles such as 3‐aminotetrahydrobenzothiophenes. This methodology relies on a 6π‐electrocyclization involving a vinyl sulfide linked to a keteniminium salt, the latter being formed in‐situ through activation of the corresponding amide with triflic anhydride.     

Total Synthesis and Biological Evaluation of Heliolactone

Strigolactones are phytohormones, which affect diverse aspects of plant growth and development with potential application in modern agriculture. Recently, heliolactone has been isolated as a non‐canonical type of strigolactone from the root exudates of sunflower, and it could be involved in signaling in the rhizosphere as well as in planta. However, its biological activity is yet to be evaluated, due to its relative chemical instability and its low natural abundance. Herein, we describe the gram‐scale synthesis of heliolactone and its derivatives by using Stille cross‐coupling as the key bond‐forming reaction, and we disclose some of their biological activities (soil stability, binding ability to strigolactone receptor, corn germination, sunflower germination, Orobanche cumana germination and leaf senescence) in comparison with other canonical and non‐canonical strigolactones.     

Comparison of thermomagnetic history effects in weakly pinned single crystals of R 3Rh4Sn13 (R=Yb, Ca)

A comparative study of the thermomagnetic memory effects of J _c in two weakly pinned low T _c superconductors, Ca₃Rh₄Sn₁₃ (CaRhSn) and Yb₃Rh₄Sn₁₃ (YbRhSn), is presented. In both the systems, the peak effect (PE) phenomenon appears as an order-disorder transformation through stepwise amorphization of the flux line lattice (FLL). However, in CaRhSn. we can witness another disorder-driven transition (Bragg glass (BG) to a vortex glass (VG) in a distinct manner as in a single crystal of high T _c YBa₂Cu₃O_7-δ for H‖c.     

Effects of protonation on the spectroscopic properties of tetrapyridoacridine (TPAC) mono- and dinuclear Ru(II) complexes in their ground and (3)MLCT excited states

The spectroscopic behavior of mono- and dinuclear Ru(II) complexes (P, T, PP and TT, Figure 1) that contain the extended planar ligand tetrapyrido[3,2-a:2',3'-c:3' ',2' '-h:2' ',3' '-j]acridine (TPAC) and either 1,10-phenanthroline (phen) or 1,4,5,8-tetraazaphenanthrene (tap) as ancillary ligands is examined in water and as a function of the pH. These four complexes luminesce in aqueous solution. The analyses of the data in absorption lead to the pKa values in the ground state, and the data in emission show that the excited 3MLCT states are much more basic than the ground state. When the complex contains tap ligands (T and TT), a decrease in pH transforms the luminescent excited basic form into another luminescent excited protonated species, which emits more bathochromically. In contrast, with phen ancillary ligands (P and PP), the protonated excited state does not luminesce. The rate constant of first protonation of the 3MLCT state is diffusion controlled, except for the dinuclear PP complex, whose protonation takes place on the nitrogen of the acridine motif. For P, in which the protonation process is the fastest, it would take place on the nitrogen atoms of the nonchelated phen moiety of the TPAC ligand. These results allow also us to gain information on the localization of the excited electron in the 1MLCT state populated upon absorption as well as in the relaxed 3MLCT emissive state. Moreover as these complexes are interesting for their study with DNA, it can be concluded from these data that a portion of the excited species in interaction with DNA will be protonated.     

Ethyl-2-(2-chloroethyl)acrylate: a new very versatile α-cyclopropylester cation synthon. Efficient synthesis of cyclopropane ester derivatives by Michael addition-induced cyclization reaction

We report here the use of the readily accessible ethyl-2-(2-chloroethyl)acrylate as a new very versatile α-cyclopropylester cation synthon, which reacts efficiently and selectively with carbon-, nitrogen-, sulfur- or phosphorus-centered nucleophiles through Michael addition followed by intramolecular capture of the incipient ester enolate to afford funtionalized cyclopropane esters in high yields.     

Ru(TAP)3]2+-photosensitized DNA cleavage studied by atomic force microscopy and gel electrophoresis: a comparative study

Topological modifications of plasmid DNA adsorbed on a variety of surfaces were investigated by using atomic force microscopy (AFM). On mica modified with 3-aminopropyltriethoxysilane (APS) or poly-L-lysine, the interaction between the plasmid DNA and the surface "freezes" the plasmid DNA conformation deposited from solution, and the AFM images resemble the projection of the three-dimensional conformation of the plasmid DNA in solution. Modified mica with low concentrations of Mg(2+) leads to a decrease in the interaction strength between plasmid DNA and the substrate, and the AFM images reflect the relaxed or equilibrium conformation of the adsorbed plasmid DNA. Under these optimized deposition conditions, topological modifications of plasmid DNA were produced under irradiation in the presence of [Ru(TAP)(3)](2+) (TAP = 1,4,5,8-tetraazaphenanthrene), which is a non-intercalating complex, and were followed as a function of illumination time. The observed structural changes correlate well with the conversion of the supercoiled covalently closed circular form (ccc form) into the open circular form (oc form), induced by a single-strand photocleavage. The AFM results obtained after fine-tuning of the plasmid DNA-substrate interaction compare well with those observed from gel electrophoresis, indicating that under the appropriate deposition conditions, AFM is a reliable technique to investigate irradiation-induced topological changes in plasmid DNA.     

Design,Synthesis and Biological Evaluation of Simplified Analogues of the Major Corn Strigolactones,Zealactone and Zeapyranolactone

Strigolactones are one of the phytohormones, which have multiple activities on plant growth and development. Since these strigolactone activities are highly associated with crop yield, use of strigolactone could be a promising technology in modern sustainable agriculture. The major strigolactones in corn root exudates have been identified as zealactone 1a/b and zeapyranolactone. We recently disclosed the first total synthesis of zealactone 1a/b together with its biological activity in corn. Herein, we describe the design and synthesis of simplified analogues of both corn-derived strigolactones with their bioavailability in soil and their biological activities. These compounds would be potential leads for the development of synthetic strigolactones for the agronomical use in a more sustainable crop production.     

Stereoselective Synthesis and Biological Profile of All Stereoisomers of Lactam Analogues of Strigolactones GR24 and GR18

Strigolactones (SLs) are signaling molecules involved in plant development and governing interactions with soil microorganisms in the rhizosphere as well as the germination of parasitic weeds. Developing their use in Crop Protection is a promising approach to a sustainable agriculture by mitigating biotic and abiotic stresses. Recently, a new class of lactam analogues of SL has emerged, namely strigolactams, displaying outstanding potency to induce the germination of parasitic weed O. cumana as well as enhanced chemical and soil stability. Herein, we describe the stereoselective synthesis of GR24 and GR18 lactams harnessing the chemistry of chiral keteniminium (KI) salts, in particular the unprecedented reactivity of chloro-substituted KI, supported by DFT calculations. We disclose subsequently the biological activity on corn of the 32 stereopure strigolactams prepared, highlighting the crucial influence of stereochemistry and lactam substitution, rationalized by docking analyses. Finally, we performed stability studies in soil, which reveal that stereoisomers display very different half-lives, reflecting the significant impact of stereochemistry on degradation kinetics.     

Novel Synthetic Approach towards Amino-Substituted Polycyclic Aromatic Hydrocarbons through Electrocyclization of Keteniminium Salts

Polycyclic aromatic hydrocarbons (PAHs) are an important family of molecules in science and technology. Amino-substituted PAHs are promising building blocks to create attractive molecules for materials science. However, the synthetic limitations have hampered to produce diverse structures of amino-substituted PAHs. Here we describe a novel efficient synthetic method to access amino-substituted PAHs through the electrocyclization of highly reactive keteniminium species. We demonstrated the synthesis of various amino-substituted PAHs and disclosed some of their photophysical properties. Furthermore, combination with theoretical calculation revealed that the multiple electrocyclization reactions of keteniminium species is a stepwise process and the fusion of additional aromatic ring to the substrate accelerates the electrocyclization.