Ikirydinium A: a new indole alkaloid from the seeds of Hunteria umbellata (K. Schum)

Chemical investigations into samples of Hunteria umbellata (K. Schum) collected in Osun State, Nigeria, led to the discovery of a new indole alkaloid, ikirydinium A, featuring an unprecedented 3-alkylpyridinium-indole-2-carboxylate scaffold. Ikirydinium A was found to exhibit antimicrobial activity (IC₅₀ 0.6 μM) against Bacillus subtilis ATCC 6051. The involvement of a common intermediate in the biosynthesis of ikirydinium A and vinblastine is hypothesized.     

Benchmarking the completely renormalised equation-of-motion coupled-cluster approaches for vertical excitation energies

The vertical excitation energies for a comprehensive test set of about 150 singlet excited states of 28 medium-sized organic molecules computed using two variants of the completely renormalised (CR) equation-of-motion (EOM) coupled-cluster (CC) method with singles, doubles, and non-iterative triples, abbreviated as δ-CR-EOMCCSD(T), and the analogous two variants of the newer, left-eigenstate δ-CR-EOMCC(2,3) approach are benchmarked against the previously published CASPT2, CC3, and EOMCCSDT-3 results, as well as the suggested theoretical best estimate (TBE) values. The δ-CR-EOMCC approaches are also used to identify and characterise about 50 additional excited states, including several states having substantial two-electron excitation components, which have not been found in the previous work and which can be used in future benchmark studies. It is demonstrated that the non-iterative triples corrections to the EOMCCSD excitation energies defining the relatively inexpensive, single-reference, black-box δ-CR-EOMCC approaches provide significant improvements in the EOMCCSD data, while closely matching the results of the iterative and considerably more expensive CC3 and EOMCCSDT-3 calculations and their CASPT2 and TBE counterparts. It is also shown that the δ-CR-EOMCC methods, especially δ-CR-EOMCC(2,3), are capable of bringing the results of the CC3 and EOMCCSDT-3 calculations to a closer agreement with the CASPT2 and TBE data, demonstrating the utility of the cost-effective δ-CR-EOMCC methods in applications involving molecular electronic spectra. We show that there may exist a relationship between the magnitude of the triples corrections defining δ-CR-EOMCC approaches and the reduced excitation level diagnostic resulting from EOMCCSD.     

Antibacterial evaluation and molecular docking studies of pyrazole–thiosemicarbazones and their pyrazole–thiazolidinone conjugates

Molecular Diversity - A library of pyrazole–thiazolidinone conjugates was synthesized using a molecular hybridization approach through a Vilsmeier–Haack reaction. The compounds were...     

Influence of graphene nanoscrolls on the crystallization behavior and nano‐mechanical properties of polylactic acid

Graphene nanoscrolls (GNS), one‐dimensional carbon‐based nanomaterials, have been predicted to possess extraordinary characteristics due to their unique open topology with scrolled graphene monolayers. In this study, the conversion of planar 2‐D graphene nanoplatelets (GNPs) to tubular and scrolled 1‐D GNSs is described. The effects of GNS as a nucleating agent to modulate the morphology, crystallization, and nano‐mechanical properties of polylactic acid (PLA) were studied. The nucleating effect of GNS and its unique topological characteristics proves to influence the crystallization of PLA. Fourier transform infrared (FTIR) spectroscopy indicated nonpreferential interactions of PLA chains around GNS due to the bulky and helical PLA macromolecular chains. Superior interfacial interactions and strain in GNS provide better load transfer between GNS and PLA matrices, resulting in higher modulus and hardness. This study is the first detailed analysis to elucidate the role of unique GNS to favorably modulate the properties of a polymer.     

First report of toxicity of Xylopiaparviflora (A. Rich.) Benth (Annonaceae) root bark's essential oil against cowpea seed bruchid,Callososbruchus maculatus Fabricius (Coleoptera: Chrysomelidae: Bruchinae)

The fumigant toxicity of Xylopia parviflora (A. Rich.) Benth (Annonaceae) root bark's essential oil (EO) against cowpea seed bruchid, Callosobruchus maculatus, was investigated in the laboratory. Dose had significant (P < 0.0001) effect on mortality at 6 hours after treatment (HAT) at a concentration of 6.25 μL/mL air which exerted 81.70% mortality, while there was no mortality in all other lower doses. At 12 HAT, 75.05% and 90.00% mortality were observed at doses of 3.15 and 6.25 μL/mL air, respectively. It was significantly (P < 0.05) higher than the mortality (50.58%) observed when 0.78 μL/mL air was applied. The lethal time for 50% of assayed adults (LT₅₀) obtained when the bruchid was exposed to X. parviflora EO at a dose of 6.25 μL/mL air (2.71 h) was significantly lower than LT₅₀ obtained at exposure of bruchid to other lower doses of 0.78–3.15 μL/mL air.     

Octahedral tilting in MM'X4 metal-oxide organic layer structures

Three metal-oxide organic frameworks have been synthesized and characterized: vanadium 1,4-benzenedicarboxylate, V2O2F0.6(OH)1.4(BDC).0.4H 2O (1); indium 1,4-benzenedicarboxylate, In 2F2.2(OH)1.8(BDC).1.6H2O (2); and aluminum 1,4-benzenedicarboxylate Al2F3(OH)(BDC) (3). The three-dimensional structures of 1, 2, and 3 have the same framework topology as the previously reported vanadium (III) 1,4-benzenedicarboxylate, VIII2(OH)2F2(BDC). The frameworks consist of inorganic layers constructed from corner sharing ML 6 octahedra (M=V, In, Al and L=OH, F) linked by BDC ligands. The structures are related to a general class of perovskite-related layer structures with composition MM'X4. The layers show characteristic distortions that can be related to tilting of the ML 6 octahedra. In particular the structure of 1 consists of O-V distances that strongly alternate along the b axis. The electronic consequences of this distortion then create a tilting of the 1,4-benzenedicarboxylate ligand about the a axis. Crystal data: 1, orthorhombic, space group Pmna, a=7.101(2) A, b=3.8416(11) A, c=20.570(6) A; 2, orthorhombic, space group Cmcm, a=7.490(4) A, b=21.803(1) A, c=8.154(4) A; 3, monoclinic, space group P2(1)/m, a=10.7569(8) A, b=6.7615(3) A, c=7.1291(3) A, beta=76.02(1) degrees.     

A Terminal,Fluxional η4‐Benzene Complex with a Thermally Accessible Triplet State is the Primary Photoproduct in the Intercyclobutadiene Haptotropism of (CpCo)phenylenes

Low‐temperature irradiation of linear [3]‐ and [4]phenylene cyclopentadienylcobalt complexes generates labile, fluxional η⁴‐arene complexes, in which the metal resides on the terminal ring. Warming induces a haptotropic shift to the neighboring cyclobutadiene rings, followed by the previously reported intercyclobutadiene migration. NMR scrutiny of the primary photoproduct reveals a thermally accessible 16‐electron cobalt η²‐triplet species, which, according to DFT computations, is responsible for the rapid symmetrization of the molecules along their long axes. Calculations indicate that the entire haptotropic manifold along the phenylene frame is governed by dual‐state reactivity of alternating 18‐electron singlets and 16‐electron triplets.     

The mobility of PEG chains versus micellar stability towards the formation of PE‐b‐PEG nanohybrid shish‐kebab on carbon nanotubes

A comparative study of the effect of copolymer composition on nanohybrid shish‐kebab (NHSK) architecture on carbon nanotubes (CNTs) is presented. A semi‐crystalline amphiphilic di‐block copolymer, polyethylene‐b‐polyethylene glycol (PE‐b‐PEG) was used in this study. Copolymer composition was varied on the basis of the molecular weight of individual copolymers and the ratio between PE and PEG. NHSK structure was characterized using a combination of scanning and transmission electron microscopy. The mobility of PEG, which is determined by its chain length was found to have a significant impact on the periodic decoration of the copolymer on CNTs. With higher chain length or molecular weight, PEG chains provided better stability to micelles formed by the copolymer. Further, PEG assisted micellar stability to create a foundation for PE chains to interact and orient along the tube axis of CNTs as a function of the copolymer composition. It was found that the stability of NHSK architecture can also be changed over time at the same crystallization temperature. This work offers novel and fundamental insights towards the mobility of PEG in the copolymer and its disk‐shaped crystal's formation and micellar stability during crystallization with CNTs. This study provides a better understanding of a mechanically tunable NHSK where the architecture of copolymer crystals can be modified by adjusting the molecular weight of PEG.