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Purpurogallin (PPG), an orange-red crystalline compound from nutgalls and oak bark, is an exemplar of numerous, ubiquitous natural colorants, biosynthesized through oxidative dimerization-decarboxylation of phenolic compounds. It possesses antioxidant, anticancer, and anti-inflammatory effects. Herein, a robust method is presented to allow students to expediently make this interesting compound that contains a tropolone ring, whose identity initiated a paradigm shift in the understanding of aromaticity. 1D and 2D nuclear magnetic resonance (NMR) spectroscopic data ([superscript 1]H, [superscript 13]C-DEPT-Q, HSQC, HMBC) were used to identify which protons are connected to carbon atoms. Fourier transform infrared spectroscopy (FT-IR), mass spectrometry, and X-ray diffraction were used to provide complementary information. Importantly, sufficient historical detail is given to provide a useful narrative that highlights the shift from deductive and synthetic proof of structural identity to modern methods of structural elucidation. As a minor, but important, aspect of iron gall inks, PPG links the work of important western historical documents from Da Vinci's Vitruvian Man to the United States Declaration of Independence. In the experience of the authors, such a pedagogic approach enlivens students with practical exercises which place them within the historical arc and reasoning of notable scientists, adding a sense of scientific discovery.

We have synthesized four new oxygen/sulfur(O^S) chelate complexes, [Zn(L)2], where L represents different ligands: methyl-3-hydroxy-3-(furyl)-2-propenedithioate (L1, 1), methyl-3-hydroxy-3-(p-fluorophenyl)-2-propenedithioate (L2, 2), methyl-3-hydroxy-3-(p-chlorophenyl)-2-propenedithioate (L3, 3), and methyl-3-hydroxy-3-(p-bromophenyl)-2-propenedithioate (L4, 4). These complexes have been characterized by using IR, multinuclear NMR (1H, 13C{1H}, and 19F{1H}), and UV-vis spectroscopy. The structural characterization of complexes 1, 2, and 4 was further achieved by single crystal X-ray diffraction (SCXRD). The supramolecular structures of these complexes are stabilized by non-covalent C–H⋯π (ZnOSC3, chelate), C–S⋯π (ZnOSC3, chelate), π⋯π (ZnOSC3,), C–H⋯O, C–H⋯F–C and C–H⋯H–C interactions. The luminescence properties of Zn(II) complexes 1–4 were studied at room temperature in the solid phase. The antileishmanial activity was evaluated for all complexes. Complexes 1 and 4 exhibited significant anti-promastigote and anti-amastigote activities, with IC50 values of 2.0 and 1.33 μg mL−1, and 2.79 and 2.02 μg mL−1, respectively. Additionally, cytotoxicity assays demonstrated that these Zn(II) β-oxodithioester complexes were toxic to promastigotes, but showed reduced toxicity towards RAW 264.7 cell lines at varying concentrations. Furthermore, the optical band gap energies of complexes 1–4 were measured and found to exhibit semiconducting behavior. [ABSTRACT FROM AUTHOR]

The mechanism for microwave absorption in a film has previously been numerically verified from the theoretical formula for RL and attributed to angular and amplitude effects with a simple geometrical representation from energy conservation unique to the film. Starting from the case where |RL| = 0, using basic transmission-line theory and mathematics, it is confirmed theoretically here that the mechanism for absorption mechanism in a film, responsible for the minima of the reflection loss RL/dB, is best explained by wave cancelation theory rather than by impedance matching theory. This theoretical proof also reveals that the mechanisms for a film and material are different. The flaws of neglecting the phase effects of interfaces in a film in quarter-wavelength theory are also quantitatively discussed from transmission-line theory. Contrary to the theory held currently, the reported minima of RL/dB originate from phase effects in the film rather than from the resonance peaks for the intrinsic frequencies of a material. [ABSTRACT FROM AUTHOR]

In Part I of this work published previously, it was proved from the transmission-line theory that impedance matching (IM) theory should be replaced by wave cancellation theory, film is different from the material, and the phase effects from interfaces should be considered in quarter wavelength theory. In this Part, it is shown that energy penetration for a film cannot be defined and IM is flawed because it cannot be proved theoretically or shown to be consistent with experimental data. The multi-absorption peaks in a film originate from wave cancellation under the constraint of energy conservation rather than from the resonances from the material. [ABSTRACT FROM AUTHOR]

An experiment published in this "Journal" has been revisited and it is found that the curve pattern of the anodic polarization curve for iron repeats itself successively when the potential scan is repeated. It is surprising that this observation has not been reported previously in the literature because it immediately brings into question the long accepted and well-known explanations involving a passive film. A qualitative and plausible explanation is provided from surprisingly simple principles for this new finding. Some important pedagogic conclusions have been derived from this work. It is noteworthy that the somewhat complicated phenomenon can be simply explained, thus providing two important lessons to students. First, even well-accepted scientific work studying simple processes may be incomplete and worthy of further study, and second, such processes may be explained simply at the undergraduate level. The contents of the paper also confirm that presenting curricular contents in a new and more correct manner is beneficial, interesting, and that research in curricular contents represents one of the important forms of educational research. (Contains 4 figures.)

Three mixed-valence trinuclear cobalt(III)–cobalt(II)–cobalt(III) complexes, [CoII{(μ-L1)(μ-OAc)CoIII(OAc)}2]·2.67H2O (1), [CoII{(μ-L1)(μ-OOCPh)CoIII(DMSO)0.8(OOCPh)0.2}2](ClO4)1.6 (2) and [CoII{(μ-L2)(μ-OOCPh)CoIII(DMSO)0.75(OOCPh)0.25}2](ClO4)1.5 (3), have been synthesized using two tetradentate N2O2 donor 'reduced Schiff base' ligands, H2L1 {1,3-bis(2-hydroxybenzylamino)2,2-dimethylpropane} and H2L2 {2,2′-[1,1′-(propane-2,2-diyldiimino)diethylidene]diphenol}, and acetate or benzoate as anionic co-ligands. These complexes have been characterized by spectroscopic measurements and their solid state structures have been determined by single crystal X-ray diffraction analysis. The cobalt(III)–cobalt(II)–cobalt(III) skeletons of complexes 1 and 2 are linear, centrosymmetric; but in complex 3, it is non-centrosymmetric. Both the central cobalt(II) and terminal cobalt(III) atoms are hexa-coordinated in all three complexes. The structure directing role of several noncovalent interactions in the solid state of the complexes has been investigated focusing on the H-bonding interactions mediated by the co-crystallized water molecules in 1 and the perchlorate counterions in 2 and 3. Thermo-gravimetric analysis (TGA) provided a thermal driven pathway to observe the loss of lattice water molecules from complex 1. All the complexes show good electrical conductivity, which has been rationalized by band gap measurements. The band gap in the solid state was determined experimentally and also by DFT calculations and it confirms that each of the complexes behaves as a semiconductor. These complexes have been used to fabricate Schottky barrier diodes. [ABSTRACT FROM AUTHOR]