The novel phenothiazinium photosensitizer QMB+ demonstrates unique spectroscopic properties upon reduction or reaction with an electron donor. The incorporation of a pyridine moiety into the phenothiazine framework significantly stabilizes the methylene blue structure due to electron delocalization over this region, as confirmed by density functional theory calculations. Importantly, the in-situ fluorescence - spectroelectrochemical measurements during reduction revealed a decrease in the original QMB+emission at 713 nm, accompanied by the appearance of a new emission band at 633 nm. This observation demonstrates that QMB+ retains its ability to emit red light; during the catalytic cycle, only an 80 nm shift in emission maxima occurs. The emission intensity of the reduction product is almost five times higher than the original fluorescence intensity of QMB+. The reversible 1e-/1H+ change is accompanied by the change of colour from blue QMB+ to violet radical cation QMB+center dot. The subsequent one-electron reduction leads to the leuco form, which is not colourless due to the presence of chromophores of an additional pyridine ring. This behaviour was proved to be facilitated in the presence of an efficient proton donor, which affects the required reduction potential. The QMB+ dye exhibits excellent photostability (at least 3000 s) upon irradiation with 575 nm light and can have higher lipophilicity due to its chemical structure in comparison with MB+. Also, both dyes were applied to polyacrylic fabrics, and their light-fastness was evaluated.

Molecular photoswitches represent a dynamic and ever-growing research area based on the ability of molecules to convert (switch) between cis- (Z) and trans- (E) isomers. Azobenzenes are the most popular and widely employed Z-E photoswitchable molecules in the development of photoresponsive, multifunctional smart materials for various applications. The promising avenues in this field include molecular fine-tuning of azobenzene- based photoswitches and the creation of single or dual-functional probes. This short overview highlights recent advances in the design of molecular photoswitches, particularly the molecular design strategies of azobenzene-based photoswitches with their structural and electronic features. Particular attention is paid to azoquinolines, which seem to be a promising alternative to azobenzenes in the design of novel multifunctional photoswitches with improved photochromic properties. Here, we have also developed the novel star-shaped multiazoquinoline photoswitch comprising individual azoquinoline-based photochromes connected to a central trisubstituted 1,3,5-triformylphloroglucinol core by quantum chemical calculations. This unique structure is favorable for independent Z-E isomerization of each azoquinoline-based photochrome within one macromolecule.

1-Indenones commonly occur in many bioactive and material molecules, thus their highly efficient synthesis attracts much attention from the synthetic community. In this manuscript, we reported an efficient method for their preparation. This reaction used the ortho-vinyl carboxylic acids as the starting material and took place through the intramolecular vinyl C-H acylation with carboxyl group. By the strategy, a wide range of 1-indenones, including both 3-substituted and 2,3-disubstituted ones, were precisely synthesized in high yields. Moreover, this reaction featured a high functional group tolerance. In addition, this reaction could be scaled up without any decrease in the reaction efficiency. We anticipate this new reaction will find wide applications in organic synthesis.

1-Indanones represent a significant class of organic compounds commonly found in many bioactive and functional materials. In this work, we reported an efficient method for their preparation. Mediated by a palladium catalyst, ortho-vinyl benzoic acids could undergo reductive cyclization in the presence of readily available formic acid, producing the corresponding 1-indanones in good to high yields. It is worth noting that high functional group tolerance was demonstrated. In addition, this reaction was easily scaled up. Mechanistic studies show that this reaction would be a tandem process involving cyclization, forming 1-indenones, and subsequent reduction with formic acid. We anticipate that this new reaction would find potential applications in organic synthesis.

A series of water-soluble molecules based on 8-isopropyl-2-methyl-5-nitroquinoline and 1,10-phenanthroline core were designed by introducing a π-conjugated bridge, vinyl unit -CH=CH-. We present the selective conversion of methyl groups located on the C2 and C9 positions in the constitution of selected quinoline or 1,10-phenanthroline derivatives, respectively, into vinyl (or styryl) products by applying Perkin condensation. The two groups of ligands differ in the presence of one or two arms. The structure of the molecule ((1E,1'E)-(1,10-phenanthroline-2,9-diyl)bis(ethene-2,1-diyl))bis(benzene-4,1,3-triyl) tetraacetate was determined by single-crystal X-ray diffraction measurements. The X-ray, NMR, and DFT computational studies indicate the influence of rotation (rotamers) on the physical properties of studied styryl molecules. The results show that the styryl molecules with the vinyl unit -CH=CH- exhibit significant static and dynamic hyperpolarizabilities. Quantum chemical calculations using density functional theory and B3LYP/6-311++G(d,p) with Grimme's dispersion correction approach predict the existence and relative stability of different spatial cis(Z)- and trans(E)-conformers of styryl derivatives of quinoline and 1,10-phenanthroline, which exhibit different electronic distribution and conjugation within the molecular skeleton, dipole moments, and steric interactions, leading to variations in their photophysical behavior and various applications. Our studies indicate that the rotation and isomerization of aryl groups can significantly influence the electronic and optical properties of π-conjugated systems, such as vinyl units (-CH=CH-). The rotation of aryl groups around the single bond that connects them to the vinyl unit can lead to changes in the effective π-conjugation between the aryl group and the rest of the π-conjugated system. The rotation and isomerization of aryl groups in π-conjugated systems significantly impact their electronic and optical properties. These changes can modify the efficiency of π-conjugation, affecting charge transfer processes, absorption properties, light emission, and electrical conductivity. In designing optoelectronic materials, such as organic dyes, organic semiconductors, or electrochromic materials, controlling the rotation and isomerization of aryl groups can be crucial for optimizing their functionality.

Osteoarthritis (OA) is a common chronic articular degenerative disease characterized by articular cartilage degradation, synovial inflammation/immunity, and subchondral bone lesions. Recently, increasing interest has been devoted to treating or preventing OA with herbal medicines. The mechanism of action of plant raw materials used in osteoarthrosis treatment is well documented. They are sought after because of the high frequency of inflammation of the knee joint among both elderly and young people engaged in sports in which their knee joints are often exposed to high-stress conditions. The purpose of this work was to present some most effective and safe plant medicines with proven mechanisms of action that can help to alleviate the growing social problem of osteoarthrosis caused in recent years. A review of the available literature based primarily on the latest editions of ESCOP and EMA monographs and the latest scientific papers has made it possible to select and propose medical management of osteoarthrosis by ranking plant medicines according to their effectiveness. Clinical studies of raw plant materials, such as Harpagophyti radix, Olibanum indicum, and Urticae foliumet herba have indicated that these drugs should be considered the first choice in osteoarthrosis treatment. The efficacy of Rosae pseudo-fructus, Salicis cortex, Filipendulae ulmariae flos et herba, Ribis nigri folium, and externally applied Capsici fructus and Symphyti radix, has also been proven by pharmacological studies. All the plant medicines mentioned in the paper have been studied in detail in terms of their phytochemistry, which can help doctors in their decisionmaking in the treatment of osteoarthrosis.

Water-soluble ligands based on a 1,10-phenanthroline core are relatively poorly studied compounds. Developing efficient and convenient syntheses of them would result in new interesting applications because of the importance of 1,10-phenanthrolines. In this manuscript, we describe novel and practical ways to introduce a carboxyl and, for the first time, a phenol and dithiocarboxyl group under mild reaction conditions. This strategy enables highly efficient and practical synthesis of suitable organosulfur compounds with high added value, high chemoselectivity, and a broad substrate range. We present the selective conversion of a hydroxydialdehyde in the form of 10-hydroxybenzo[h]quinoline-7,9-dicarbaldehyde into its derivative, unique hydroxydicarboxylic acid, by an oxidation procedure, giving 10-hydroxybenzo[h]quinoline-7,9-dicarboxylic acid. A similar procedure resulted in the formation of 9-methyl-1,10-phenanthroline-2-carboxylic acid by oxidation of commercially available neocuproine. An alternative method of obtaining 1,10-phenanthroline derivatives possessing carboxylic acid group can be based on the hydrolysis of ester or nitrile groups; however, this synthesis leads to unexpected products. Moreover, we apply Perkin condensation to synthesize a vinyl (or styryl) analog of 1,10-phenanthroline derivatives with phenol function. This reaction also demonstrates a new, simple, and efficient strategy for converting methyl derivatives of 1,10-phenanthroline. We anticipate that the new way of converting methyl will find wide application in chemical synthesis.

The quinoline derivatives arouse interest due to their broad spectrum of activity. The phosphorus compounds under investigation, quinolinylphosphonic and -phosphinic acids and aminophenylphosphonic and -phosphinic acids, possess potent bioactive properties, mimicking amino acids, phosphate esters, anhydrides, or carboxylate groups in enzymes. Despite its potential value, there is no reported example of quinolinylphosphonic or -phosphinic acids with phosphonic or phosphinic functional groups connected directly to the benzene ring in quinoline constitution. The selected quinoline derivatives have been synthesized by adopting the Skraup-Doebner-Von Miller reaction. To this end, the syntheses of aminophenylphosphonic and -phosphinic acids were conducted and afforded the target products with high yield. All structures have been proven by the combination of NMR, IR, MS, and HRMS techniques and were rationalized based on DFT calculation. The structures of triphenylphosphane oxide (TPO), diphenylphosphosphinic acid (1c), (tert-butyl)phenylphosphinic acid (1d) and bis(3-nitrophenyl)phosphinic acid (2c) were determined by single-crystal X-ray diffraction measurements. The Hirshfeld surface analyses for 1c, 1d and 2c were performed to analyze the intermolecular interactions in their crystal structures. According to our findings, the presence of numerous intermolecular PO•••H, NO•••H, and CH•••O contacts stabilizes the crystal structures. The NO•••H interactions manifest in the IR spectrum of 2c crystal as a narrow band with a maximum at 3088 cm-1. The PO•••H intermolecular interactions are attributed to a weak experimental band at 1288 cm-1.

Carboxylic acids are readily available in both the natural and synthetic world. Their direct utilization for preparing organophosphorus compounds would greatly benefit the development of organophosphorus chemistry. In this manuscript, we describe a novel and practical phosphorylating reaction under transition metal-free reaction conditions that can selectively convert carboxylic acids into the P-C-O-P motif-containing compounds through bisphosphorylation, and the benzyl phosphorus compounds through deoxyphosphorylation. This strategy provides a new route for carboxylic acid conversion as the alkyl source, enabling highly efficient and practical synthesis of the corresponding value-added organophosphorus compounds with high chemo-selectivity and wide substrate scope, including the late modification of complex APIs (active pharmaceutical ingredients). Moreover, this reaction also indicates a new strategy for converting carboxylic acids into alkenes by coupling this work and the subsequent WHE reaction with ketones and aldehydes. We anticipate that this new mode of transforming carboxylic acids will find wide application in chemical synthesis.

This paper reports a Hirshfeld surfaces analysis of crystalline 2- and 4-methylmethcathinone (2-MMC and 4-MMC) hydrochlorides to analyze NH center dot Cl and CH center dot center dot center dot Cl intermolecular interactions and approve the formation of the N-+(2)-Cl- salt fragment in both 2-MMC center dot HCl and 4-MMC center dot HCl crystals. Two isomeric dimers were separated from the corresponding crystal packing to model IR spectra of the crystalline 2-MMC center dot HCl and 4-MMC center dot HCl species within the framework of density functional theory (DFT) and B3LYP/6-31G(d,p) approach. All observed IR bands were assigned and interpreted in the experimental spectra of the 2-MMC center dot HCl and 4-MMC center dot HCl standard crystal samples representing an important aspect of the forensic problem solvation. A detailed analysis of the nature of IR spectra for both isomers has shown that intermolecular interactions between the NH+2 and Cl- ionic moieties occur in two crystalline samples. The presence of the ionized form of the 2- and 4-MMC center dot HCl compounds with the NH2+ Cl- fragment is a key condition for the correct reproduction of the IR spectra when calculating the corresponding dimer structures as a model of a crystalline sample.

Aim and background: Introducing deuterium to a molecule is of interest to a wide variety of research, including investigation of reaction mechanisms or kinetics, analysis of drug metabolism, structural elucidation of molecules, and syntheses of isotopically labeled materials used for NMR spectroscopy and medicinal research. Objective: The transition-metal-free regioselective deuteration of 2-methylquinolin-8-ol (1a) and 2,5- dimethylquinolin-8-ol (2a) with ambient reaction conditions and low-cost reagents is described in the paper. Methods: Regioselective H/D isotope exchange has been presented by combining the following techniques 1H NMR, 13C NMR, GC-MS, and X-ray crystallography. The molecular orbitals of the deuterated molecule 1a have been calculated by density functional theory (DFT) to provide an elucidation of the isotope exchange. Result: The metal-free regioselective green deuteration based on modified Skraup-Doebner-Von Miller synthesis and water-d2 KOD solution or water-d2 D2SO4 solution of hydroxyquinolines was elaborated. Conclusion: The metal-free regioselective green deuteration of hydroxyquinoline-type compounds with ambient reaction conditions and low-cost reagents provided valuable tools for isotopic labeling. The modified Skraup-Doebner-Von Miller synthesis of deuterated hydroxyquinolines has the potential to allow higher deuteration capacity. The presented isotopic exchange reactions also possess synthetic values as the source of deuterated compounds for the studies of NMR spectroscopy, medicinal research, and drug discovery processes.

One-pot synthesis of selected P-vinylbenzyls under solvent-free conditions was elaborated on a multigram scale. Several techniques have been used to characterize properties of all new products: MS, HRMS, E.A., and multinuclear NMR in solution and solid-state. The structure of 5,5-dimethyl-2-(4-vinylbenzyl)-1,3,2-dioxaphosphinane 2-oxide (2 d) was determined by single-crystal X-ray diffraction measurements rationalized based on DFT calculation. The X-ray and NMR studies of 2 d indicate the appearance of an anomeric effect.

Two unique structures were isolated from the phosphorylation reaction of 10H-phenothiazine. The 5,5-dimethyl-2-(10H-phenothiazin-10-yl)-1,3,2-dioxaphosphinane 2-oxide (2a) illustrates the product of N-phosphorylation of phenothiazine. Moreover, a potential product of 2a instability, a thiophosphoric acid 2b, was successfully isolated and structurally characterized. Molecule 2a, similarly to sulfoxide derivative 3, possesses interesting phosphorescence properties due to the presence of d-pπ bonds. The X-ray, NMR, and DFT computational studies indicate that compound 2a exhibits an anomeric effect. Additionally, the syntheses of selected symmetrical and unsymmetrical pyridine-embedded phenazines were elaborated. To compare the influence of phosphorus and sulfur atoms on the structural characteristics of 10H-phenothiazine derivatives, the high-quality crystals of (4a,12a-dihydro-12H-benzo[5,6][1,4]thiazino[2,3-b]quinoxalin-12-yl)(phenyl)methanone (1) and selected phenazines 5,12-diisopropyl-3,10-dimethyldipyrido[3,2-a:3′,2′-h]phenazine (5) and 5-isopropyl-N,N,3-trimethylpyrido[3,2-a]phenazin-10-amine (6a) were obtained. The structures of molecules 1, 2a, 2-mercapto-5,5-dimethyl-1,3,2-dioxaphosphinane 2-oxide (2b), 3,7-dinitro-10H-phenothiazine 5-oxide (3), 5 and 6a were determined by single-crystal X-ray diffraction measurements.

New rhenium(I) tricarbonyl complexes based on the phenanthroline ligand were designed and synthesized to investigate the role of carbazole (cbz) and pyrrolidine (pyrr) substituents in determining thermal, electrochemical and optoelectronic properties. Both pyrr and cbz are electron-releasing substituents, but they differ in the steric hindrance and electron delocalization ability. The impact of pyrr and cbz on ground-and excited-state properties of [ReCl(CO)(3)(cbz(2)-CH(3)phen)] (1) and [ReCl (CO)(3)(pyrr(2)-CH(3)phen)] (2) were investigated with a range of techniques including cyclic voltammetry, absorbance and emission spectroscopies, transient absorption spectroscopy, and they were discussed in comparison with the model chromophore [ReCl(CO)(3)(CH(3)phen)] (3). Experimental results were supported by theoretical calculations. The most striking difference between the pyrr and cbz groups was seen in their impact on the LUMO energy level. While the attached carbazole groups decreased the LUMO energy of 1, the pyrrolidine ones in 2 resulted in the rise of LUMO energy level compared to the model chromophore. For both 1 and 2, the HOMO got energetically destabilized in agreement with electro-donor abilities of pyrr and cbz substituents. Structural modification of phen backbone resulted also in changes of distribution of occupied MOs of 1 and 2 in relation to 3. Experimentally, it was manifested in noticeable changes of electrochemical and photophysical behaviour of the resulting Re(I) complexes in relation to the model chromophore.

Complexes of 1,10-phenanthrolines with cations of transition metals have broad range of applications. This work aims at designing and investigating phenothiazine and carbazole substituted 1,10-phenanthrolines as ligands for future complexes with transient metal cations. The combined electrochemical, spectroelectrochemical and DFT studies were employed to demonstrate the effect of broken symmetry in substituted 4,7-di(phenothiazine)-1,10-phenanthrolines on their spectroelectrochemical properties. A reversible color change (new absorption band around 500 nm) due to phenothiazine radical cation was observed in the first oxidation step. Results further indicate that phenothiazine substituents behave as two equivalent but almost electronically isolated redox centres. The work additionally presents a comprehensive reaction mechanistic study of oxidation and reduction processes complemented by HPLC-MS/MS identification.

The synthesis of hypodiphosphoric acid and its related compounds began in 1877, but no summary of the synthetic efforts has been reported. This review includes published papers related to the molecules containing the >P(=O)-P(=O)< fragment, which notably resembles the structure of the >P(=O)-O-P(=O)< moiety, the essential building block of many important molecules found in nature and in the field of medicinal chemistry. This review covers the strategies related to the synthesis of hypodiphosphoric acid (former name hypophosphoric acid), its ester form, and diphosphine dioxides. Finally, some properties and applications of these structures studied during this period are presented.

The vicarious nucleophilic substitution of hydrogen (VNS) reaction in electron-deficient nitroquinolines was studied. Properties of all new products have been characterized by several techniques: MS, HRMS, FTIR, GC-MS, electronic absorption spectroscopy, and multinuclear NMR. The structures of 4-chloro-8-nitroquinoline, 8-(tert-butyl)-2-methyl-5-nitroquinoline, 9-(8-nitroquinolin-7-yl)-9H-carbazole and (Z)-7-(9H-carbazol-9-yl)-8-(hydroxyimino)quinolin-5(8H)-one were determined by single-crystal X-ray diffraction measurements. The 9-(8-nitroquinolin-7-yl)-9H-carbazole and (Z)-7-(9H-carbazol-9-yl)-8-(hydroxyimino)quinolin-5(8H)-one illustrate the nitro/nitroso conversion within VNS reaction. Additionally, 9-(8-isopropyl-2-((8-isopropyl-2-methyl-5-nitroquinolin-6-yl)methyl)-5-nitrosoquinolin-6-yl)-9H-carbazole is presented as a double VNS product. It is postulated that the potassium counterion interacts with the oxygen on the nitro group, which could influence nucleophile attack in that way.

Recent research towards the development of the redox probes for in vivo applications focuses on near-infrared fluorescent sensors and tricyanofuran-based fluorophores gained popularity thanks to their favorable spectral properties. The tricyanofuran-based boronate probe (TCF-BA) has been proposed for specific fluorescent detection of selected biological oxidants in vitro and in vivo. Here, we report the detailed chemical reactivity of TCF-BA toward hydrogen peroxide, hypochlorite, and peroxynitrite in the presence and absence of glutathione, a major small molecule biothiol present intracellularly at millimolar concentrations. We demonstrate that, at the physiologically relevant concentration of glutathione, the TCF-BA probe forms an adduct, resulting in decreased reactivity of the probe toward the oxidants tested. Only peroxynitrite efficiently oxidizes TCF-BA in the presence of GSH. Furthermore, the fluorescent phenolic oxidation product, TCF-OH, also reacts with glutathione, which results in a decreased fluorescence intensity. This observation suggests that the results reported with TCF-based probes may be affected by the changes in intracellular glutathione, in addition to the desired analyte. We also report a modified probe (TCF-BA-2) derived from 1-naphthalene boronic acid, which has similar reactivity toward peroxynitrite. Although the TCF-BA-2 probe also reacts with glutathione, the absorption spectrum of its oxidation product, TCF–OH–2, is not influenced by glutathione and, therefore, can be applied for real-time monitoring of peroxynitrite formation in biological systems.