Characterization of barium sulphate as a TLC material for the separation of plant carboxylic acids

Summary A mixture of barium sulphate and calcium sulphate has been shown to be a good TLC material for the detection and the quantification of a variety of carboxylic acids known to be plant growth regulators and carboxylic acids of importance in the citrus fruit industry.     

A simple,rapid, and robust “on-the-go” identity testing of biotherapeutics using FTIR spectroscopy

The stunning rise of biotherapeutics as successful treatments of complex and hard-to-treat diseases, in particular cancer, has necessitated the development of a rapid analytical method capable of differentiating these otherwise significantly similar antibody-based products. The existing methods for product identification pose significant drawbacks in terms of the consumption of time and labor. Here, we present an FTIR spectroscopy-based simple, rapid, and robust method that is capable of differentiating between the biotherapeutics (both innovator products and biosimilars). The proposed approach uses partial least-squares-discriminant analysis to pinpoint subtle differences in the FTIR spectra of the samples, enabling us to not only identify the product but also calculate its concentration. This FTIR-based method can be used to fulfill the identity testing requirement of a pharmaceutical drug in its final packaged form set by the US Food and Drug Administration. Along with this, identity testing can also be deployed at multiple steps in the manufacturing process and can also be used by the appropriate regulatory or government agency for tackling counterfeits of biotherapeutic products.     

Fluorescent aluminum chelate complexes as modified precursors for nano-structured alumina

A series of new mononuclear heteroleptic derivatives of aluminum(III), {[(CH₃COCHCOCH₃)AlL] (1 and 4)}, {[(C₆H₅COCHCOC₆H₅)AlL] (2, 5, and 7)}, and {[(C₉H₆NO)AlL] (3 and 6)}, have been synthesized by reacting Al(OPrⁱ)₃ with tridentate Schiff base H₂L^x (H₂L¹ = C₁₃H₁₀BrNO₂; H₂L² = C₁₄H₁₃NO₃; H₂L³ = C₁₇H₁₃NO₂) and β-diketone/8-hydroxyquinoline (β-diketone = acetylacetone/dibenzoylmethane) in 1?:?1?:?1 stoichiometry using anhydrous benzene and ethanol. All the complexes were characterized by elemental analysis, FTIR, and NMR (¹H and ¹³C) spectral studies. Molecular structures obtained from single-crystal XRD of aqua 1 (1a) and DMSO coordinated 2 (2a) authenticate their existence. Further, nanostructured α-alumina was synthesized from 1 by well-established sol–gel method and was characterized by powder XRD, TEM, and EDX analyses.     

Preparation of chiral cholestanofluorene and its electron-rich derivatives for isolation of a stable cation-radical salt

A simple and practical synthesis of a variety of chiral fluorene derivatives is described where a cholestane moiety is attached to the carbon 9 of the fluorene ring system from readily available starting materials. An appropriately substituted fluorene derivative (i.e., R = OMe) forms a highly colored (chiral) cation-radical that can be isolated as robust hexachloroantimonate salt. Interestingly, the simplest cholestanofluorene (i.e., R = H) can also be transformed into a dibromo derivative (i.e., R = Br), a precursor to the (poly)cholestanofluorenes where the cholestane moieties will serve not only as groups that impart chirality but also allow them to be soluble in common organic solvents. The details of these works are described.     

A new class of chiroptical molecular switches based on the redox-induced conformational changes

A series of optically active bis(catecholketal)s 1-3 were prepared, and their chiroptical properties were investigated experimentally and theoretically, demonstrating that they undergo conformational changes upon 1-e(-) oxidation and can be used as redox-responsive chiroptical molecular switches.     

Calculations of the optical spectra of hydrocarbon radical cations based on Koopmans' theorem

The first few bands in the optical spectra of radical cations can often be interpreted in terms of A-type transitions that involve electron promotions from doubly occupied to the singly occupied molecular orbital (SOMO) and/or B-type transition which involve electron promotion from the SOMO to virtual molecular orbitals. We had previously demonstrated that, by making use of Koopmans' theorem, the energies of A-type transitions can be related to orbital energy differences between lower occupied MOs and the highest occupied MO (HOMO) in the neutral molecule, calculated at the geometry of the radical cation. We now propose that the energies of B-type transitions can be related similarly to energy differences between the lowest unoccupied MO (LUMO) and higher virtual MOs in the dication, also calculated at the geometry of the radical cation, by way of an extension of Koopmans' theorem to virtual MOs similar to that used sometimes to model resonances in electron scattering experiments. The optical spectra of the radical cations of several polyenes and aromatic compounds, the matrix spectra of which are known (or presented here for the first time), and for which CASSCF/CASPT2 calculations are available, are discussed in terms of these Koopmans-based models. Then the spectra of five poly(bicycloalkyl)-protected systems and that of hexabenzocoronene, compounds not amenable to higher level calculations, are examined and it is found that the Koopmans-type calculations allow a satisfactory interpretation of most of the features in these spectra. These simple calculations therefore provide a computationally inexpensive yet effective way to assign optical transitions in radical ions. Limitations of the model are discussed.