Suppression of the dimerization of the viologen radical cation by cucurbit[7]uril (CB7) in water is a well-known phenomenon. Herein, two counter-examples are presented. Two viologen-containing thread molecules were designed, synthesized, and thoroughly characterized by (1)H DOSY NMR spectrometry, UV/Vis absorption spectrophotometry, square-wave voltammetry, and chronocoulometry: BV(4+), which contains two viologen subunits, and HV(12+), which contains six. In both threads, the viologen subunits are covalently bonded to a hexavalent phosphazene core. The corresponding [3]- and [7]pseudorotaxanes that form on complexation with CB7, that is, BV(4+)⊂(CB7)2 and HV(12+)⊂(CB7)6, were also analyzed. The properties of two monomeric control threads, namely, methyl viologen (MV(2+)) and benzyl methyl viologen (BMV(2+)), as well as their [2]pseudorotaxane complexes with CB7 (MV(2+)⊂CB7 and BMV(2+)⊂CB7) were also investigated. As expected, the control pseudorotaxanes remained intact after one-electron reduction of their viologen-recognition stations. In contrast, analogous reduction of BV(4+)⊂(CB7)2 and HV(12+)⊂(CB7)6 led to host-guest decomplexation and release of the free threads BV(2(·+)) and HV(6(·+)), respectively. (1)H DOSY NMR spectrometric and chronocoulometric measurements showed that BV(2(·+)) and HV(6(·+)) have larger diffusion coefficients than the corresponding [3]- and [7]pseudorotaxanes, and UV/Vis absorption studies provided evidence for intramolecular radical-cation dimerization. These results demonstrate that radical-cation dimerization, a relatively weak interaction, can be used as a driving force in novel molecular switches.

No abstract

This research includes the design and synthesis of new derivatives for rhodanine azo compounds (4a–c) containing a naphthalene ring. Physiochemical properties of the synthesized compounds were determined by their melting points, FTIR, 1H-NMR, 13C-NMR, and elemental analysis spectroscopic techniques. The biological activities of the newly prepared azo rhodanine compounds were evaluated against some pathogenic bacteria using three different bacterial species including (Escherichia coli., Pseudomonas aeruginosa, Staphylococcus aureus) and compared with amoxicillin as a reference drug. The results showed that our compounds have moderate-to-good vital activity against the mentioned pathogenic bacteria. The selectivity and sensitivity of the newly prepared rhodanine azo compounds with transition metals Co2+, Cu2+, Zn2+, Ni2+, and Fe3+ were studied using UV–vis and fluorescence spectroscopy techniques. Among the synthesized azos, azo 4c showed affinity toward Fe3+ ions with an association constant of 4.63 × 108 M−1. Furthermore, this azo showed high sensitivity toward Fe3+ ions with detection limits of 5.14 µM. The molar ratio and Benesi–Hildebrand methods confirmed the formation of complexes between azo 4c and Fe3+ with 1:2 binding stoichiometry. Therefore, azo 4c showed excellent potential for developing efficient Fe3+ chemosensors.

New Schiff bases and azo dyes derivatives have been synthesized via appropriate conventional methods using pyranoquinolinone as a starting material. The compounds obtained were characterized by spectral analysis and evaluated for anticancer activity in several human tumor cell lines: MCF-7 breast cancer, HepG2 liver cancer and HCT-116 colon carcinoma. 5-fluorouracil was used as a reference drug. The in vitro cytotoxicity screening results revealed that all tested compounds showed promising activity against MCF-7 cells. In particular, compounds 6a, 6b, and 7b showed excellent activity against the three human tumor cell lines. Structure-activity relationship studies indicated that the azo derivative with a trifluoromethoxy group (compound 7b) was the most potent candidate against the three human tumor cell lines (IC50, 1.82-8.06 μg/mL). Our findings highlight pyranoquinolinone analogues as a promising class of compounds for new anticancer therapies.

Oxidative stress is a causative factor in the pathophysiology of numerous diseases, such as diabetes, atherosclerosis, cancer, and neurodegenerative and cardiovascular diseases. Therapeutic antioxidants are promising candidates for preventing and treating conditions in which oxidative stress is a contributing factor. In this study, we report the design, synthesis and antioxidant activity of six compounds containing the 2-methoxyphenol moiety core structure. The synthesized derivatives were characterized using 1H NMR, 13C NMR, Fourier-transform infrared (FT-IR), and elemental analysis spectroscopy. The antioxidant properties of the compounds were evaluated using the 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH), 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), and oxygen radical absorbance capacity (ORAC) assay. New phenolic acid-derived compounds with antioxidant activity were identified.

A new series of substituted 2(1H)-pyridones (4a-i) and their glucosides (5, 6a-e) were prepared as potential agents against leukemia (HL-60) cells. Glucosides (5,6a-e) were synthesized using three independent methods. Microwave protocol as an ecologically new method was used to synthesize the target compounds. Structures of the new products were confirmed using one- and two-dimensional NMR spectroscopy. In vitro exposure of pyridones substituted at position 4 with a 2-thienyl or 2-(trifluoromethyl)phenyl were found to exhibit high antiproliferation activities; in particular, 3-cyano-4-(thien-2'-yl)-6-(4''-chlorophenyl)-2(1H)-pyridone (4c) and its glucoside analogue (6c) had the highest activity.

Quinoline analogues exhibited diversified biological activities depending on the structure type. A number of natural products with pyrano[3,2-c]quinolone structural motifs and patented chromenes were reported as promising cytotoxic agents. A molecular docking study was employed to investigate the binding and functional properties of 3-amino pyranoquinolinone 2a-c as anti-cancer agents. The three 3-amino pyranoquinolinone 2a-c showed an interesting ability to intercalate the DNA-topoisomerase complex and were able to obtain energetically favorable binding modes (−8.3 -−7.5 kcal/mol). Compound 2c containing butyl chain superiority over the other two compounds 2a-b which appeared to be involved in arene-H interactions with the two dG13 aromatic centers. The butyl chain also appeared to be immersed into a side subpocket formed by the side chains of Asn520 and Glu522 and the backbone amide of Arg503, Gly504, Lys505 and Ile506. Hence, the 3-amino pyranoquinolinone 2c used as starting material to prepare derivatives of pyrano[3,2-c]quinolone containing 1,2,4-triazine ring 4a-b which will enhance the anti-cancer activity. Pyrano[3,2-c]quinoline-2,5-diones 2a-c and 4a-b were evaluated in vitro on cell lines Ehrlich Ascites carcinoma cells (EAC), liver cancer cell line Hep-G2 and breast cancer cell line MCF-7 for the development of novel anticancer agents. The screening results revealed that compounds 4a-b were found most active candidates as anticancer agents.

Bacterial infections present a serious challenge to healthcare practitioners due to the emergence of resistance to numerous conventional antibacterial drugs. Therefore, new bacterial targets and new antimicrobials are unmet medical needs. Rhodanine derivatives are known to possess potent antimicrobial activities. In this study, we determined the activity spectrum of a series of new rhodanine derivatives against representative Gram-positive and Gram-negative bacterial strains. Compounds 3a and 5a had the highest activity with minimum inhibitory concentrations in the range of 1.12-2.5 μg/mL. Transmission electron microscope results confirmed that activities against bacteria occurred via rupturing of the cell wall. Molecular modeling results suggested that rhodanine derivatives have the potential to irreversibly bind to the penicillin-binding protein (PBP) Ser62 residue in the active site. Thus, our results suggested that these rhodanine derivatives could be potential antibacterial drug candidates with strong activity against Gram-negative bacteria.