Evaluation of the effect of graphene oxide-based nanocomposites on smear layer by a scanning electron microscope: Laboratory investigation

This study is to examine the effect of graphene oxide (GO) and GO-based nanocomposites (GO_EDTA, GO_CHIT) on the smear layer by scanning electron microscopy (SEM). Sixty human single-rooted anterior teeth were used. Samples were randomly categorised into six groups. Distilled water in group 1, 17% EDTA in group 2, chitosan (CHIT) solution in group 3, GO solution in group 4, GO_EDTA solution in group 5 and GO_CHIT in group 6 were used as irrigation solutions. Photomicrographs were acquired from the coronal, middle and apical parts of the samples by SEM. Statistical analyses were performed using Kruskal-Wallis, Mann-Whitney U and Wilcoxon tests. There was a statistically significant difference among the groups (p < 0.003). Adding GO to CHIT and EDTA did not affect removing the smear layer in all segments (p < 0.003). Incorporating GO into EDTA and CHIT solutions did not change their interaction with the smear layer.

Biphenylene-containing polycyclic conjugated compounds

There has been a growing emphasis on the synthesis of polycyclic conjugated compounds, driven by their distinct structural characteristics that make them valuable candidates for use in cutting-edge technologies. In particular, acenes, a subgroup of polycyclic aromatic compounds, are sought-after synthetic targets due to their remarkable optoelectronic properties which stem from their π-conjugation and planar structure. Despite all these promising characteristics, acenes exhibit significant stability problems when their conjugation enhances. Various approaches have been developed to address this stability concern. Among these strategies, one involves the incorporation of the biphenylene unit into acene frameworks, limiting the electron delocalization through the antiaromatic four-membered ring. This review gives a brief overview of the methods used in the synthesis of biphenylenes and summarizes the recent studies on biphenylene-containing polycyclic conjugated compounds, elucidating their synthesis, and distinct optoelectronic properties.

Click-Type Synthesis of Homoconjugated Push-Pull Chromophores: Computational Investigation of Optical and Nonlinear Optical (NLO) Properties

Homoconjugated push–pull chromophores were obtained by an efficient, click-type formal [2+2] cycloadditions. With these short synthetic transformations, complex chromophore structures were achieved in a single step without any by-product formation. Significant second-order optical nonlinearities have been calculated for the synthesized compounds.

Isoniazid Linked to Sulfonate Esters via Hydrazone Functionality: Design, Synthesis, and Evaluation of Antitubercular Activity

Isoniazid (INH) is one of the key molecules employed in the treatment of tuberculosis (TB), the most deadly infectious disease worldwide. However, the efficacy of this cornerstone drug has seriously decreased due to emerging INH-resistant strains of Mycobacterium tuberculosis (Mtb). In the present study, we aimed to chemically tailor INH to overcome this resistance. We obtained thirteen novel compounds by linking INH to in-house synthesized sulfonate esters via a hydrazone bridge (SIH1-SIH13). Following structural characterization by FTIR, ¹H NMR, ¹³C NMR, and HRMS, all compounds were screened for their antitubercular activity against Mtb H37Rv strain and INH-resistant clinical isolates carrying katG and inhA mutations. Additionally, the cytotoxic effects of SIH1-SIH13 were assessed on three different healthy host cell lines; HEK293, IMR-90, and BEAS-2B. Based on the obtained data, the synthesized compounds appeared as attractive antimycobacterial drug candidates with low cytotoxicity. Moreover, the stability of the hydrazone moiety in the chemical structure of the final compounds was confirmed by using UV/Vis spectroscopy in both aqueous medium and DMSO. Subsequently, the compounds were tested for their inhibitory activities against enoyl acyl carrier protein reductase (InhA), the primary target enzyme of INH. Although most of the synthesized compounds are hosted by the InhA binding pocket, SIH1-SIH13 do not primarily show their antitubercular activities by direct InhA inhibition. Finally, in silico determination of important physicochemical parameters of the molecules showed that SIH1-SIH13 adhered to Lipinski's rule of five. Overall, our study revealed a new strategy for modifying INH to cope with the emerging drug-resistant strains of Mtb.

3-Alkynylindoles as Building Blocks for the Synthesis of Electronically Tunable Indole-Based Push-Pull Chromophores

In this study, two different classes of push–pull chromophores were synthesized in modest to excellent yields by formal [2+2] cycloaddition-retroelectrocyclization (CA-RE) reactions. N-Methyl indole was introduced as a new donor group to activate alkynes in the CA-RE transformations. Depending on the side groups’ size and donor/acceptor characteristics, N-methyl indole-containing compounds exhibited λ_max values ranging between 378 and 658 nm. The optoelectronic properties of the reported D–A-type structures were studied by UV/vis spectroscopy and computational studies. The complete regioselectivity observed in the products was elaborated by one-dimensional (1D) and two-dimensional (2D) NMR studies, and the electron donor strength order of N-alkyl indole and triazene donor groups was also established. The intramolecular charge-transfer characteristics of the target push–pull chromophores were investigated by frontier orbital depictions, electrostatic potential maps, and time-dependent density functional theory calculations. Overall, the computational and experimental results match each other. Integrating a new donor group, N-alkyl indole, into the substrates used in formal [2+2] cycloaddition-retroelectrocyclizations has significant potential to overcome the limited donor-substituted substrate scope problem of CA-RE reactions.

Iron-Catalyzed α-C-H Cyanation of Simple and Complex Tertiary Amines

This manuscript details the development of a general and mild protocol for the α-C-H cyanation of tertiary amines and its application in late-stage functionalization. Suitable substrates include tertiary aliphatic, benzylic, and aniline-type substrates and complex substrates. Functional groups tolerated under the reaction conditions include various heterocycles and ketones, amides, olefins, and alkynes. This broad substrate scope is remarkable, as comparable reaction protocols for α-C-H cyanation frequently occur via free radical mechanisms and are thus fundamentally limited in their functional group tolerance. In contrast, the presented catalyst system tolerates functional groups that typically react with free radicals, suggesting an alternative reaction pathway. All components of the described catalyst system are readily available, allowing implementation of the presented methodology without the need for lengthy catalyst synthesis.

Synthesis and Optoelectronic Properties of Iptycene–Naphthazarin Dyes

We report the synthesis and characterization of iptycene–naphthazarin dyes by using a sequential Diels–Alder approach. The tautomerization of naphthazarin was used as the key step in the synthesis, with structures confirmed by single-crystal X-ray and NMR analysis. The systematic trends in electronic properties were investigated by UV/Vis spectroscopy. BF2 complexes of the dyes were prepared by reaction with BF3·OEt2 in CH2Cl2.

Naphthazarin-Polycyclic Conjugated Hydrocarbons and Iptycenes

The synthesis of a set of naphthazarin-containing polycyclic conjugated hydrocarbons is described herein. Sequential Diels-Alder reactions on a tautomerized naphthazarin core were employed to access the final conjugated systems. Complete conjugation across the backbone can be achieved through complexation with BF₂, as observed by ¹H NMR analysis and UV/vis spectroscopy. Precise synthetic control over the degree of oxidation of naphthazarin quinone Diels-Alder adduct 10 is additionally demonstrated and enables us to direct its subsequent reactivity. Finally, this work serves to demonstrate the potential for naphthazarin as a building block in the synthesis of novel organic electronic materials.

Homoconjugated and Spiro Push–Pull Systems: Cycloadditions of Naphtho- and Anthradiquinones with Electron-Rich Alkynes

We report the synthesis and characterization of three new classes of push–pull chromophores using [2+2]-cycloaddition reactions of electron-rich alkynes and electron-poor alkenes. Previous investigations have focused on the reactions of cyano-substituted electron acceptors. This study demonstrates that cyano-free electron acceptors, naphtho- and anthradiquinones, can also be used to access extended push–pull systems. The effects of the structural changes on the spectroscopic and electronic properties were investigated by UV/vis spectroscopy. Structures were confirmed by X-ray and NMR analysis in solution.