Comparative Study of TiO2, ZnO, and Nb2O5 Photoanodes for Nitro-Substituted Naphthoquinone Photosensitizer-Based Solar Cells.

This research focuses on the first demonstration of NO2Lw (2-hydroxy-3-nitronaphthalene-1,4-dione) as a photosensitizer and TiO2, ZnO, and Nb2O5 as photoanode materials for dye-sensitized solar cells (DSSCs). The metal-free organic photosensitizer (i.e., nitro-group-substituted naphthoquinone, NO2Lw) was synthesized for this purpose. As a photoanode material, metal oxides, such as TiO2, ZnO, and Nb2O5, were selected. The synthesized NO2Lw contains an electron-withdrawing group (-NO2) and anchoring groups (-OH) that exhibit absorption in the visible range. The UV-visible absorbance spectrum of NO2Lw demonstrates the absorption ascribed to ultraviolet and visible region charge transfer. The NO2Lw interacts with the TiO2, ZnO, and Nb2O5 photoanode, as shown by bathochromic shifts in wavelengths in the photosensitizer-loaded TiO2, ZnO, and Nb2O5 photoanodes. FT-IR analysis also studied the bonding interaction between NO2Lw and TiO2, ZnO, and Nb2O5 photoanode material. The TiO2, ZnO, and Nb2O5 photoanodes loaded with NO2Lw exhibit a shift in the wavenumber of the functional groups, indicating that these groups were involved in loading the NO2Lw photosensitizer. The amount of photosensitizer loading was calculated, showing that TiO2 has higher loading than ZnO and Nb2O5 photoanodes; this factor may constitute an increased JSC value of the TiO2 photoanode. The device performance is compared using photocurrent-voltage (J-V) curves; electrochemical impedance spectroscopy (EIS) measurement examines the device's charge transport. The TiO2 photoanode showed higher performance than the ZnO and Nb2O5 photoanodes in terms of photoelectrochemical properties. When compared to ZnO and Nb2O5 photoanodes-based DSSCs, the TiO2 photoanode Bode plot shows a signature frequency peak corresponding to electron recombination rate toward the low-frequency region, showing that TiO2 has a greater electron lifetime than ZnO and Nb2O5 photoanodes based DSSCs.

Synergistic and Additive Effects of Menadione in Combination with Antibiotics on Multidrug-Resistant Staphylococcus aureus: Insights from Structure-Function Analysis of Naphthoquinones.

Antimicrobial resistance (AMR) interferes with the effective treatment of infections and increases the risk of microbial spread and infection-related illness and death. The synergistic activities of combinations of antimicrobial compounds offer satisfactory approaches to some extent. Structurally diverse naphthoquinones (NQs) including menadione (-CH3 group at C2) exhibit substantial antimicrobial activities against multidrug-resistant (MDR) pathogens. We explored the combinations of menadione with antibiotic ciprofloxacin or ampicillin against Staphylococcus aureus and its biofilms. We found an additive (0.590 %) were also observed. However, preformed biofilms were not affected. Dent formation was also evident in S. aureus treated with the test compounds. The structure-function relationship (SFR) of NQs was used to determine and predict their activity pattern against pathogens. Analysis of 10 structurally distinct NQs revealed that the compounds with -Cl, -Br, -CH3 , or -OH groups displayed the lowest MICs (32-256 µg/mL). Furthermore, 1,4-NQs possessing a halogen or -CH3 moiety showed elevated ROS activity, whereas molecules with an -OH group affected cell integrity. Improved activity of antimicrobial combinations and SFR approaches are significant in antimicrobial therapies.

Metal complexes of a pro-vitamin K3 analog phthiocol (2-hydroxy-3-methylnaphthalene-1,4-dione): synthesis, characterization, and anticancer activity.

The hydroxy analog of vitamin K3 (2-methylnaphthalene-1,4-dione) is known as phthiocol (2-hydroxy-3-methylnaphthalene-1,4-dione; pht). Both vitamin K3 and phthiocol possess anticancer and antihemorrhagic properties. Phthiocol is a noninnocent ligand and provides monodentate, bidentate, or tridentate coordination sites to metal ions. A series of transition metal complexes (Mn(II); 1 and 1A, Co(II); 2 and 2A, Ni(II); 3 and 3A, Cu(II); 4 and 4A, and Zn(II); 5 and 5A) are synthesized at 0 °C using sodium metal (1 to 5) and at 26 °C (1A to 5A). The chemical composition of the complexes obtained is of the type [M(phthiocolate)2(H2O)2]. At room temperature (26 °C), trans coordination of the phthiocolate ligand is achieved (1A through 5A), whereas at 0 °C and using sodium metal as a reductant, cis coordination is observed in Mn(II) complexes (1 and its methanol adduct 1B). A Na(I) complex of phthiocol, Na(pht), is isolated as a polymer. The ligand phthiocol and the complexes Na(pht), 1, 1A, and 3 crystallize in a monoclinic crystal system. X-ray structures reveal that the bond distances of coordinated phthiocol ligands are in the reduced naphthosemiquinone form in the complexes synthesized at 0 °C. The metal complexes of phthiocol (pht) were evaluated for their anticancer activity against MCF-7 (breast) and A549 (lung) cancer cell lines. Experiments like apoptosis, mitochondrial potential, reactive oxygen species (ROS) production, effect on the cell cycle, and cell proliferation were performed to compare selected complexes against both cell lines. The metal complexes of phthiocol synthesized at 0 °C showed substantial cytotoxic activity against MCF-7 and A549 cell lines. Further, effect of selected phthiocol complexes on peripheral blood mononuclear cells (PBMCs) was adventitious to realize their safety. Vitamin K3, phthiocol, and metal complex 4 successfully inhibited the enzymatic activity of human topoisomerase II. The multifunctionality of any anticancer agent influencing apoptosis, mitochondrial dysfunction, the effect on the cell cycle, and cell proliferation is crucial for defining the prognosis and precise treatment of cancer.

Naphthoquinoneoxime-Sensitized Titanium Dioxide Photoanodes: Photoelectrochemical Properties.

Naphthoquinoneoxime derivatives, viz., LwOx, 3-hydroxy-4-(hydroxyimino)naphthalen-1 (4H)-one; PthOx, 3-hydroxy-4-(hydroxyimino)-2-methylnaphthalen-1(4H)-one; and Cl_LwOx, 2-chloro-3-hydroxy-4-(hydroxyimino)naphthalen-1(4H)-one, are used in fabrication of dye-sensitized solar cells (DSSCs). The photophysical and electrochemical properties of the sensitizers were studied. The HOMO-LUMO energy gaps of the sensitizers (LwOx, PthOx, and Cl_LwOx) calculated by using the intersection of UV-visible and fluorescence spectra are 2.85, 2.71, and 2.87 eV, respectively. The energy band alignment energy level of the sensitizer, that is, the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO), should match with the energy level of the TiO2 conduction band and the redox potential of iodine/triiodide electrolyte to allow smooth electron transfer. The electrochemical characterization of sensitizers was done to find the LUMO and HOMO level of the sensitizer. It shows that the LUMO level of (LwOx, PthOx, and Cl_LwOx) is above the conduction band position of TiO2. Electrochemical impedance spectroscopy was used to study the charge transport resistance and electron lifetime of DSSCs. The charge transport resistance at the TiO2 |electrolyte|counter electrode interface was reduced in the Cl_LwOx device; thus, the electron lifetime of Cl_LwOx was enhanced compared to LwOx and PthOx sensitizers. The fabricated device was characterized using photocurrent density-voltage (J-V) measurement. It is observed that there was an enhancement in the overall power conversion efficiency (η) of the DSSCs fabricated by using Cl_LwOx sensitizers as compared to LwOx and PthOx sensitizer-loaded photoanodes. Enhancement in power conversion efficiency, that is, photovoltage and photocurrent, is achieved due to the chlorine substituent. Thus, the chlorine substituent naphthoquinoneoxime pushes the electron density, enhancing the pushing nature and facilitating the lone pair present in the N-OH moiety to attach to TiO2 more strongly.

Titania Nanorods Embedded with 2-Bromo-3-(methylamino)naphthalene-1,4-dione for Dye-Sensitized Solar Cells.

In a recent study, TiO2 nanorod electrodes were prepared by the hydrothermal approach followed by calcination at various temperatures from 300 to 600 °C. The effects of calcination temperature on the morphological and structural properties were investigated. The novel analogue of aminonaphthoquinone(2R-(n-alkylamino)-1,4-naphthoquinone) photosensitizer, viz. BrA1, 2-bromo-3-(methylamino)naphthalene-1,4-dione was synthesized from 2,3-dibromonaphthalene-1,4-dione. X-ray crystallographic data collection and refinement confirm that BrA1 crystallizes in the triclinic space group P 1̅. After loading BrA1, the photosensitizer on the annealed TiO2 nanorod (TiO2NR) electrodes, the optical properties of the photoanodes showed broadbands in each of the UV and visible regions, which are attributed to the π →π* and n → π* charge-transfer transitions, respectively. The dye-sensitized solar cell (DSSC) system was formed by loading the BrA1 photosensitizer on TiO2NR. The electrochemical impedance spectroscopy (EIS) analyses confirm that calcination temperature improves the charge transportation by lowering the resistance path during the photovoltaic process in TiO2NR (400 °C) photoanode-based DSSCs due to the sufficient photosensitizer adsorption and fast electron injection. Due to the effective light harvesting by the BrA1 photosensitizer and charge transport through the TiO2 nanorod, the power conversion efficiencies (PCE) of the TiO2NR (400 °C/BrA1-based) DSSCs were improved for 2-bromo-3-(methylamino)naphthalene-1,4-dione.

1H and 13C NMR chemical shifts of 2-n-alkylamino-naphthalene-1,4-diones.

1H as well as 13C chemical shifts of 32 compounds of C (3) substituted 2-(n-alkylamino)-3R-naphthalene-1,4-dione (where n-alkyl: methyl, to octyl, R = H, Cl, Br, and CH3) are investigated through 1H, 13C, DEPT, gDQCOSY, and gHSQCAD NMR experiments and M06-2X/6-311++G (d,p) density functional theory are discussed. Single crystal X-ray structure of Br-3, as well as 18 different derivatives of naphthalene-1,4-diones, are revealed for its inter and intra-molecular hydrogen bonding interactions.

Metal-complexes as ligands to generate asymmetric homo- and heterodinuclear M(A)(III)M(B)(II) species: a magneto-structural and spectroscopic comparison of imidazole-N versus pyridine-N.

Ten hetero- and homodinuclear M(A)(III)M(B)(III) complexes, 1-10, containing the metal centers Fe(III)Zn(II) (1), Fe(III)Cu(II) (2), Fe(III)Ni(II) (3), Fe(III)Fe(II) (4), Fe(III)Mn(II) (5), Cr(III)Ni(II) (6), Cr(III)Zn(II) (7), Ga(III)Ni(II) (8), Co(III)Fe(II) (9), and Mn(III)Mn(II) (10) are described. The tridentate ligation property of the divalent metal complexes tris(1-methylimidazole-2-aldoximato)metal(II) with three facially disposed pendent oxime O-atoms has been utilized to generate the said complexes. Complexes were characterized by various physical methods including MS, IR, UV-vis, Mossbauer and EPR spectroscopy, cyclic voltammetry (CV), variable-temperature (2-290 K) magnetic susceptibility, and X-ray diffraction techniques. Binuclear complexes 1-10 contain three oximato anions as bridging ligands and are isostructural in the sense that they all contain a metal(III) ion, LM(A)(III) (L = 1,4,7-trimethyl-1,4,7-triazacyclononane), in a distorted octahedral environment M(A)(III)N(3)O(3) and a second six-coordinated divalent metal ion, M(B)(II), in a trigonally distorted M(B)(II)N(6) geometry. A comparison of the cyclic voltammograms of the complexes with those of similar systems reveal both ligand-centered and metal-centered redox processes. Complexes 2, 3, 5, and 6 display antiferromagnetic exchange coupling of the neighboring metal centers in the order Fe(III)Mn(II) (5) < Fe(III)Ni(II) (3) < Fe(III)Cu(II) (2) whereas Fe(III)Ni(II) (3) > Cr(III)Ni(II) (6). On the contrary, complex 10, containing high-spin Mn(III) and Mn(II) centers, exhibits ferromagnetic coupling yielding a "high-spin" molecule with an S(t) = (9)/(2) ground state. X-band electron paramagnetic resonance (EPR) spectroscopy for 6, Cr(III)Ni(II) and 3, Fe(III)Ni(II) has been used to establish the electronic ground state in great detail and to complement the magnetic susceptibility measurements. Moreover, computational results have been included to compare the sigma-bonding character of the nitrogen lone pair in imidazole-containing ligand and the analogous pyridine-containing oxime.

SOM assembly of hydroxynaphthoquinone and its oxime: polymorphic X-ray structures and EPR studies.

Investigation on solvent-induced polymorphism in X-ray structures of 2-hydroxy-1,4-naphthoquinone (Lawsone) 1, is carried out. In protic methanol, 1 crystallizes in monoclinic space group P2(1)/c (1a) comprising of 2D hydrogen bonded network via cyclic dimers. In aprotic solvent such as acetone on the other hand, 1 exhibits orthorhombic space group Pna 2(1) (1b) and emerges with 1D catemeric chain. Solvent-induced topological isomerism of cyclic dimers and helical catemeric chains arising from (i) bifurcated intra- and inter molecular hydrogen bondings viz. O-H...O=C interactions between C(2) hydroxyl and C(1), C(4) carbonyls, (ii) C-H...O interactions viz. C(3)-H...O(1)C(1) have been discussed. A signal for radical in 1 at g = 2.0058 is signatured by EPR spectrum and it's oxime derivative viz. 2-hydroxy-4-naphthoquinone-1-oxime 2, in solid state shows biradical and monoradical formation with aggregation of dimer and monomer due to non-covalent hydrogen bonds. Zero field split parameters for 2 are estimated to be D = 215 G, Ex = 13 G, Ey = 47 G at 298 K. A half field signal at 77 K indicates triplet ground state. Frozen glass EPR of 2 resolves as regioregular dimeric-monomeric species showing hyperfine interactions with 1-oximino nitrogen in dimer A (14N) = 15.5 G].