Influence Of Substituents Research Articles

Position of substituents directs the electron transfer properties of entatic state complexes: new insights from guanidine-quinoline copper complexes.

In a previous study, we showed that the properties and the ability as an entatic state model of copper guanidine quinoline complexes are significantly influenced by a methyl or methyl ester substituent in the 2-position. To prove the importance of the 2-position of the substituent, two novel guanidine quinoline ligands with a methyl or methyl ester substituent in the 4-position and the corresponding copper complexes were synthesized and characterized in this study. The influence of the substituent position on the copper complexes was investigated with various experimental and theoretical methods. The molecular structures of the copper complexes were examined in the solid state by single-crystal X-ray diffraction (SCXRD) and by density functional theory (DFT) calculations indicating a strong dependency on the substituent position compared to the systems substituted in the 2-position from the previous study. Further, the significantly different influence on the donor properties in dependency on the substituent position was analyzed with natural bond orbital (NBO) calculations. By the determination of the redox potentials, the impact on the electrochemical stabilization was examined. With regard to further previously analyzed guanidine quinoline copper complexes, the electrochemical stabilization was correlated with the charge-transfer energies calculated by NBO analysis and ground state energies, revealing the substituent influence and enabling a comparatively easy and accurate possibility for the theoretical calculation of the relative redox potential. Finally, the electron transfer properties were quantified by determining the electron self-exchange rates via the Marcus theory and by theoretical calculation of the reorganization energies via Nelsen's four-point method. The results gave important insights into the dependency between the ability of the copper complexes as entatic state model and the type and position of the substituent.

Ultra‐Broadband Organic THz Generators: Influence of Substituents on THz Phonon Vibrations in Phenolic Parallel‐Type Cation–Anion Assembly

AbstractOrganic terahertz (THz) crystals consist of polar molecules with various functional substituents, resulting in numerous molecular phonon vibrations in the THz frequency range. However, the effect of incorporating substituents into organic THz crystals on the resulting THz absorption is rather an unexplored area. In this work, by choosing an appropriate model system consisting of two benchmark organic nonlinear optical crystals, exhibiting an identical type of phenolic cation–anion assembly but different substituents, their ultra‐broadband THz wave generation characteristics are demonstrated and investigated. Compared to the unsubstituted crystals, the substituted crystals possess one more methoxy substituent on highly polar cationic chromophores. Their vibrational modes and THz absorption characteristics are investigated theoretically by periodic density functional theory and experimentally by ultra‐broadband THz spectroscopy up to 12 THz. In phenolic parallel‐type cation–anion assembled organic THz crystals, the existence of a methoxy substituent differently influences the molecular vibrations in low and high THz frequency ranges. In the lower THz frequency range, the unsubstituted crystals exhibit additional strong entire molecular vibrations, the so‐called cation‐on‐cation slipping vibrations, which do not exist in the substituted crystals. In contrast, the methoxy substituent leads to additional strong intramolecular vibrations in the higher THz frequency range.

Influence of substituents on the water oxidation performance for copper–bipyridine catalysts

Since it was first reported in 2012, copper-based molecular catalysts for water oxidation have gained significant attention. While investigations have endeavored to elucidate additional copper molecular catalysts for water oxidation and enhance their catalytic activities, few have systematically explored substituents' impact on their water oxidation performance. In this work, a series of copper-bipyridine catalysts, (2,2′-bipyridine)Cu(OH)2 derivatives with various substituents were synthesized by simply mixing the copper salts with 4,4′-R-2,2′-bipyridine ligands, where R represents seven distinct substituents. The UV–vis and FTIR spectra confirm the successful synthesis of the catalysts. However, only four of them are stable under the experimental conditions. The electrochemical studies show that their water oxidation potential follows the order of Cu-H < Cu-CH3 < Cu–OCH3 < Cu-CH2OH, indicating their water oxidation ability. Computation calculation indicates a linear relationship between the turnover frequency and the HOMO-LUMO energy gap. This work uncovers the influence of substituents on the catalytic properties of copper-bipyridine catalysts, offering valuable insights into the rational design of copper-based catalysts.

Towards spin-crossover in pseudo-octahedral iron(III) complexes of strongly absorbing phenanthridine-based N^N^O- ligands

Paramagnetic complexes which can undergo spin crossover between different magnetic states that also strongly absorb light are highly attractive for the pursuit of optical magnetic technologies. Against this backdrop, we prepared a library of Fe(III) complexes ligated by monoanionic, tridentate N^N^O- ligands (RL: (2-R1-(4-imino-methyl)-phenanthridinyl)]-5-R2-phenolate where R1 = tBu, F, OMe, R2 = H or R = tBu, R2 = tBu) bearing strongly absorbing π-extended phenanthridine (benzo[c]quinoline) donors: [Fe(tBuL)2]PF6, [Fe(tBuLtBu)2]PF6, [Fe(FL)2]PF6, and [Fe(OMeL)2]PF6. The solid-state structures of three of the series were determined using single-crystal X-ray diffraction, confirming pseudo-octahedral coordination geometries. Electronic absorption spectra shows strong absorbances near 340 nm and 415 nm for the series due to π-π* and ligand-to-metal-charge-transfer (LMCT) transitions, respectively, along with a long absorptive tail that extends well into the visible region, only attenuating close to 850 nm. Magnetic measurements in the solid-state (SQUID magnetometry) and in solution (Evans’ Method) revealed the influence of ligand substituents. For example, the magnetic moment of [Fe(FL)2]PF6 in the solid-state remains more or less constant at a χmT ∼ 2.3 over a large temperature range (25–300 K) indicative of a mixed spin configuration that is maintained in solution at ambient temperature, while [Fe(tBuL)2]PF6 and [Fe(tBuLtBu)2]PF6 only reach values of ∼1.5 at higher temperature. In comparison, the χmT of [Fe(OMeL)2]PF6 undergoes a much more abrupt drop upon cooling, from ∼2.5 to below 0.5 at 100 K, consistent with spin-crossover type behavior.

Structure–Property Relationships with Functionalized Subphthalocyanines: Toward Photovoltaic Devices More Stable to Photooxidative Degradation Mediated by Singlet Oxygen

AbstractIn this work, the overarching goal of improving the photooxidative stability of organic components used in photovoltaic devices is addressed, focusing on the common problem of degradation mediated by singlet molecular oxygen. Through a systematic exploration of boron subphthalocyanines (SubPcs), the influence of donor and acceptor substituents on the SubPc's redox properties has been examined, including the SubPc's ability to (1) act as a photosensitizer for singlet oxygen generation and (2) deactivate singlet oxygen are examined. How singlet oxygen formation and removal are influenced by linking together three SubPcs in a compact structure and by linking a SubPc to another molecular unit of relevance for organic photovoltaics (indenofluorene‐extended tetrathiafulvalene) is also examined. Synthetic protocols rooted in acetylenic scaffolding, experimental and computational structure–property relationships (optical and redox properties, singlet oxygen quantum yields, and removal kinetics), and characteristics of a functional photovoltaic device using a SubPc molecule are presented, demonstrating that cyano functionalization results in remarkably enhanced organic photovoltaic device stability.

X-ray Crystal Structure, Hirshfeld Surface Analysis, DFT, and Anticancer Effect of 3-Hydroxy-4-phenyl-1,5-benzodiazepin-2-one Derivatives

This study investigated the crystallographic and electronic properties of 1,5-benzodiazepine compounds, namely: cis-(3S,4S)-3-hydroxy-7,8-dimethyl-4-phenyl-1,3,4,5-tetrahydro-1,5-benzodiazepin-2-one 3b, trans-(3R,4R)-1-ethyl-3-hydroxy-7,8-dimethyl-4-phenyl-1,3,4,5-tetrahydro-2H-1,5-benzodiazepin-2-one 4, and trans-(3S,4S) 1-ethyl-3-ethoxy-7,8-dimethyl-4-phenyl-1,3,4,5-tetrahydro-1,5-benzodiazepin-2-one 5. Hirshfeld surface analysis was also applied to discern the intermolecular interactions, highlighting the significance of hydrogen bonding, van der Waals forces, and the influence of specific substituents. Furthermore, the MESP maps created using the density functional theory revealed the electrostatic nature of these molecules. The absence of dark blue regions on the MESP maps and variations due to different functional groups and substitutions were noteworthy findings. Collectively, this research offers crucial insights into the behaviour, interactions, and potential applications of new compounds. Finally, the anticancer effects of compounds 3b, 4, and 5 were evaluated against three cancer cell lines and one normal cell line, and the results showed that 3b and 4 had potent antiproliferative effects against all three cancer cell lines.

Revealing the Unique Role of Water in the Formation of Benzothiazoles: an Experimental and Computational Study.

We present here a joint experimental and computational study on the formation of benzothiazoles. Our investigation reveals a green protocol for accessing benzothiazoles from acyl chlorides using either water alongside a reducing agent as the reaction medium or in combination with stoichiometric amounts of a weak acid, instead of the harsh conditions and catalysts previously reported. Specifically, we show that a protic solvent, particularly water, enables the formation of 2-substituted benzothiazoles from N-acyl 1,2-aminothiophenols already at room temperature, without the need for strong acids or metal catalysts. DFT Molecular Dynamics simulations coupled with advanced enhanced sampling techniques provide a clear understanding of the catalytic role of water. We demonstrate how bulk water - due to its extended network of hydrogen bonds and an efficient Grotthuss mechanism - provides a reaction path that strongly reduces the reaction barriers compared to aprotic environments, namely more than 80 kJ/mol for the first reaction step and 250 kJ/mol for the second. Finally, we discuss the influence of different aliphatic and aromatic substituents with varying electronic properties on chemical reactivity. Besides providing in-depth mechanistic insights, we believe that our findings pave the way for a greener route toward an important class of bioactive molecules.

Elongation of N6-benzyladenosine scaffold via Pd-catalyzed C–C bond formation leads to derivatives with antiflaviviral activity

Decoration of nucleoside analogues with lipophilic groups often leads to compounds with improved antiviral activity. For example, N6-benzyladenosine derivatives containing elongated lipophilic substituents in the benzyl core efficiently inhibit reproduction of tick-borne encephalitis virus (TBEV), while N6-benzyladenosine itself potently inhibits reproduction of human enterovirus A71 (EV-A71). We have extended a series of N6-benzyladenosine analogues using effective synthetic methods of CC bond formation based on Pd-catalyzed cross-coupling reactions (Sonogashira and Suzuki) in order to study the influence of bulky lipophilic substituents in the N6 position of adenosine on the antiviral activity against flaviviruses, such as TBEV, yellow fever virus (YFV) and West Nile virus (WNV), as well as a panel of enteroviruses including EV-A71, Echovirus 30 (E30), and poliovirus type 2 (PV2). Reproduction of tested flaviviruses appeared to be inhibited by the micromolar concentrations of the compounds, while cytotoxicity in most cases was beyond the detection limit. Time-of-addition studies demonstrated that the hit compounds inhibited the stage of viral RNA synthesis, but not the stages of the viral entry or protein translation. As a result, several new promising antiflaviviral leads have been identified. On the other hand, none of the synthesized compounds inhibited enterovirus reproduction, indicating a possibility of involvement of flavivirus-specific pathways in their mechanism of action.

Theoretical Analysis of a Three-Component Reaction between Two Diazo Compounds and a Hydroxylamine Derivative: Mechanism, Enantioselectivity, and Effect of Cooperative Catalysis.

The mechanism, enantioselectivity, and effect of chiral phosphoric acid (CPA) cocatalyst were investigated by the density functional theory (DFT) for the three-component asymmetric aminohydroxylation between two diazo compounds and a hydroxylamine derivative. This type of cascade process is cooperatively catalyzed by Rh2(OAc)4 and CPA. The obtained results clearly indicate that the first step of the global reaction involves a nucleophilic attack at the nitrogen center of N-hydroxyaniline by rhodium-carbene intermediates producing imines. Subsequently, an enolate intermediate was recognized as the key species generated from the second diazo compound and the leaving benzyl alcohol (BnOH) fragment of the first step and in the presence of the same dirhodium catalyst. Then, the reaction is terminated by the asymmetric Mannich-type addition, delivering the aminohydroxylation products of an S-R conformation with the assistance of chiral phosphoric acid. The distortion/interaction analysis shows that the relative distortions of CPA and the enol play a vital role in the energy ordering of the stereocontrolling transition states (TSs). Furthermore, the influence of different substituents in CPA was fully rationalized by distortion/interaction analysis. This study opens up novel synthetic possibilities and improves the reaction predictability when exploring the related types of cooperatively catalyzed organic transformations.

Triphenylphosphine─Closed-Shell Metal Cation Interactions.

The interactions between group 1 and 11 monocations and group 2 dications with triphenylphosphine were studied by using a combination of correlated molecular orbital theory and density functional theory. Two binding modes were found: the front side (phosphorus lone pair) and back side (phenyl rings). Group 1 and 2 cations prefer binding to the π system rather than to the lone pair of the phosphorus atom, and their ligand binding energies (LBEs) correlate with the atomic ionic radii as well as the hardness of the atomic ion. Group 11 monocations prefer binding to the lone pair of the phosphorus atom, and their LBEs are correlated with the hardness of the cation but exhibit a different trend than for the groups 1 and 2 cations. The LBEs of the cations with C2H4, C6H6, and C6H5PH2 are also reported to aid in the analysis of the cation-π interactions and the influence of the PH2 substituent on the energy of this interaction. The LBEs for binding to C2H4 and C6H6 are the most complete and reliable set of values for these species.

Influence of bulky peripheral substituents on subphthalocyanine derivatives: Implications for photocatalytic and photoelectrochemical hydrogen production

A series of novel subphthalocyanine (SubPc) derivatives with bulky electron-donating substituents were synthesized for visible light-induced photocatalytic and photoelectrochemical hydrogen production. SubPc derivatives were decorated with bulky thiophenoxy (coded SubPc 1–2) and phenoxy (coded SubPc 3–4) substituents to compare the influence of the nature of the peripheral bulky substituents on the photophysical and photocatalytic activity of SubPc. The highest photocatalytic performance was obtained from SubPc 4, having diphenyl phenoxy substituents with an H2 production rate of 7.233 mmol g-1h−1. The photocatalytic hydrogen evolution activities of all SubPc sensitized TiO2 photocatalysts enhanced approximately four times in the presence of Pt co-catalyst. The photocatalysts showed remarkable long-term stability and reproducibility of H2 evolution over 24-hour irradiation. SubPc 4-based photocatalytic system reached a considerable catalytic activity with the H2 production of 16.022 mmol g−1 and a turnover number (TON) value of 34,089 for 24 h irradiation. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) studies were carried out to better understand the photocatalytic abilities of SubPc derivatives and develop a symbiotic connection with experimental investigations. The results highlight the importance of peripheral substituents in modifying electron density, dipole moment, and HOMO-LUMO energy levels and improving SubPc derivative light-harvesting performance. The presence of 2,6-diisopropyl on SubPc derivatives (SubPc 2 and 4) caused a significant change in the properties, resulting in favourable electron transport characteristics and, therefore, improving photocatalytic performance. Furthermore, the incorporation of TiO2, as shown in SubPc 1@TiO2 and SubPc 2@TiO2, resulted in a modest reduction in chemical hardness, implying increased charge transfer inside the molecule and, as a consequence, enhancing its efficacy as a sensitizer. These theoretical discoveries provide a solid foundation for the customized design and optimization of SubPc derivatives for effective photocatalytic applications.

Steric congestion in heavy pnictines alters oxidative halogenation pathways

Dihalotriorganopnictoranes serve as important synthetic precursors in Group 15 chemistry, but the influence of the organic substituents on the synthesis and reactivity of these compounds remains underexplored for the heavy pnictogens. We recently reported the isolation of Dipp3Sb (Dipp = 2,6-diisopropylphenyl). The bulky Dipp substituents permit the isolation of monomeric tetrahedral stibine oxide Dipp3SbO, yet also allow for the formation of the trigonal bipyramidal Dipp3SbF2. We now report the isolation of a sterically crowded bismuthine, Dipp3Bi. Reaction between Dipp3Bi and XeF2 afforded Dipp3BiF2, which features a distorted trigonal bipyramidal geometry in the solid state. Reaction between Dipp3Bi and PhICl2 resulted in the generation of 1-chloro-2,6-diisopropylbenzene. Reaction between Dipp3Sb and PhICl2 resulted in the formation of Dipp3SbCl2, which features a square pyramidal geometry in the solid state. Mes3SbCl2, Mes3SbBr2, Mes3BiCl2, and Mes3BiBr2 (Mes = mesityl) were structurally characterized and all exhibit trigonal bipyramidal geometries in the solid state. Solution-phase spectroscopic measurements reflect the fluxionality of all of these molecules, but theoretical analyses in the gas phase suggest that the square pyramidal geometry of Dipp3SbCl2 is more thermodynamically favorable than the trigonal bipyramidal geometry, possibly due to the presence of intramolecular secondary interactions between the Dipp and Cl substituents. These results highlight the ability of Dipp substituents to alter reactivity pathways of heavy pnictines.

Pd-PEPPSI catalysts bearing N-heterocyclic carbene ligands derived from caffeine and theophylline for Mizoroki–Heck and C(sp2)–H arylation reactions

The activity of three Pd-PEPPSI catalyst precursors bearing N-heterocyclic carbene (NHC) ligands derived from caffeine and theophylline was tested in Mizoroki–Heck reactions between styrene and five different aryl bromides bearing electron-donating or withdrawing substituents. Moderate to excellent conversions (44–98%) were achieved within 3 h at 100 °C with K2CO3 as the base and 1 mol% of catalyst in a green water/isopropanol mixture under a normal atmosphere. Electron-withdrawing groups favored the reaction and led to the highest yields of stilbene products (up to 85% after chromatographic purification). The activity of the three [PdX2(NHC)(Py)] complexes (X = Cl, I) was also probed in the C(sp2)–H arylation of two heterocyclic substrates using the same set of five representative aryl bromides. Experimental conditions were further optimized on a model reaction (1 mol% of catalyst in DMA at 120 °C for 4 h with KOAc as the base). Gratifyingly, 1-methyl-2-pyrrolecarboxaldehyde afforded high conversions (59–99%) and yields of isolated products (49–85%), with the best results obtained again under the influence of electron-withdrawing substituents. When a more challenging substrate, viz., 3,5-dimethylisoxazole was used, modest to satisfactory conversions (41–80 %) and yields (30–69%) could still be reached with the best catalyst for each reaction. The structural properties of the complexes under investigation were compared using X-ray crystallography and Hirshfeld surface analysis.

Oxygen-Containing Quaternary Phosphonium Salts (oxy-QPSs): Synthesis, Properties, and Cellulose Dissolution.

In the present study, the synthesis of oxygen-containing quaternary phosphonium salts (oxy-QPSs) was described. Within this work, structure-property relationships of oxy-QPSs were estimated by systematic analysis of physical-chemical properties. The influence of the oxygen-containing substituent was examined by comparing the properties of oxy-QPSs in homology series as well as with phosphonium analog-included alkyl side chains. The crystal structure analysis showed that the oxygen introduction influences the conformation of the side chain of the oxy-QPS. It was found that oxy-QPSs, using an aprotic co-solvent, dimethylsulfoxide (DMSO), can dissolve microcrystalline cellulose. The cellulose dissolution in oxy-QPSs appeared to be dependent on the functional group in the cation and anion nature. For the selected conditions, dissolution of up to 5 wt% of cellulose was observed. The antimicrobial activity of oxy-QPSs under study was expected to be low. The biocompatibility of oxy-QPSs with fermentative microbes was tested on non-pathogenic Saccharomyces cerevisiae, Lactobacillus plantarum, and Bacillus subtilis. This reliably allows one to safely address the combined biomass destruction and enzyme hydrolysis processes in one pot.

Stationary concentration of 1O2 over 1O2 quantum yield: Next level of photoactivity analysis

The investigation of the activity of photosensitizers is a multivariate challenge for their further application in photocatalysis. Porphyrins are attractive photoactive molecules for chemical and biochemical applications, while their observed photocatalytic efficiency is a function of a variety of characteristics. In the present work the influence of porphyrin substituents on their photoactivity and photostability along with the solvent effect were studied and discussed in details. Series of experiments with 9,10-diphenylanthracene (DPA) as a selective 1O2 trap allowed to develop the approach for direct measurement of [1O2] and quantitatively evaluate the influence of various factors onto it. The processes of 1O2 relaxation, as well as its chemical and physical quenching were separated and analyzed individually. A kinetic scheme for the photosensitization process was treated with steady-state approximation to develop a mathematical apparatus, where a non-linear dependence between photosensitizer and singlet oxygen concentration was found. The general character of the derived non-linear dependence was proved experimentally for each studied porphyrin. Physical and chemical quenching rate constants of the studied porphyrins were calculated. DFT calculations allowed to find an empirical correlation between HOMO energies and observed rate constants. A plausible reaction mechanism between TPP and 1O2 was examined with Fast-NEB-TS method.

Photoionization of pentalene and derivatives

The vertical, valence ionization energies for pentalene (C8H6) and some of its derivatives have been calculated as free molecules in the gas phase using high-level ab initio coupled-cluster method: EOM-DLPNO-CCSD. Their valence electronic structures depend on the number, type and position of substituents. We have used the calculated vertical, valence ionization energies to simulate UV photoelectron spectra. HOMO-LUMO gaps and the influence of substituents on ionization energies and electronic structure were also studied. We discuss the antiaromaticity and bis-annulation effects in pentalenes.

The influence of substituents in governing the strength of the P-X bonds of substituted halophosphines R1R2P-X (X = F and Cl).

In this study, the gas-phase homolytic P-F and P-Cl bond dissociation energies (BDEs) of a set of thirty fluorophosphine (R1R2P-F) and thirty chlorophosphine-type (R1R2P-Cl) molecules have been obtained using the high-level W2 thermochemical protocol. For the R1R2P-F species, the P-F BDEs (at 298K) differ by up to 117.0kJmol-1, with (H3Si)2P-F having the lowest BDE (439.5kJmol-1) and F2P-F having the largest BDE (556.5kJmol-1). In the case of the chlorophosphine-type molecules, the difference in BDEs is considerably smaller (i.e., 72.6kJmol-1), with (NC)2P-Cl having the lowest P-Cl BDE (299.8kJmol-1) and (HO)2P-Cl having the largest (372.4kJmol-1). We have further analyzed the effect of substituents in governing the P-F and P-Cl BDEs by considering the effect of substituents in the parent halogenated precursors (using molecule stabilization enthalpies) and the effect of substituents in the product radicals (using radical stabilization enthalpies). Finally, we have also assessed the performance of a wide range of DFT methods for their ability to compute the gas-phase P-F and P-Cl BDEs contained in this dataset. We find that, overall, the double hybrid functional DSD-PBEB95 offers the best performance for both bond types, with mean absolute deviations of just 2.1 (P-F BDEs) and 2.2 (P-Cl BDEs) kJmol-1.

Influence of heteroatoms and substituents on structural and spectroscopic parameters of saturated six-member ring heterocycles: experimental and theoretical study of 1-methyl-1-germacyclohexane

The conformational analysis of newly synthesized compound, 1-methyl-1-germacyclohexane, is performed by means of a combined vibrational spectroscopy and theoretical methods. The liquid 1-methyl-1-germacyclohexane at room temperature is investigated using conventional ATR-FTIR, FT-IR (gas phase) and Raman methods. FT-IR spectra of the isolated in low-temperature neon and nitrogen matrices are registered. The further detailed vibrational conformational analysis is performed utilizing density functional theory and perturbation theory based methods. All possible 12 canonical ring conformations considering axial/equatorial CH3 group position are analyzed by utilizing DFT/B3LYP, DFT/M06-2X and MP2 at aug-cc-pVTZ theory level.The most stable conformer with the global energy minimum structure in the chair axial conformation is investigated in detail. Analysis of the potential energy surface reveals transition states (TS) and energy barriers. The conformational path is found to be as follows: chair (1C4)→ envelope/half-chair (TS)→ skew-boat (1S3 - C1 symmetry)→ boat (TS)→ skew-boat (1S5 - C2 symmetry). The energy barrier for 1C4 (chair) to 1S3 (skew-boat) conversion is 4.8 kcal/mol while for the reverse process equals to 0.5 kcal/mol.A similar conformational analysis is performed for different configurations of germacyclohexane, silacyclohexane and cyclohexane with mono- and disubstituents: CH2Cl, CH3, Cl and F. Such approach enables investigation of influence of the heteroatoms and substituents of various size and type on the structural parameters and conformational diversity.

Synthesis, Docking Studies and Evaluation of Chalcones as Anti-Helicobacter pylori and antitumoral Agents.

Helicobacter pylori colonizes the gastric epithelium of 50 % of world population and it is the main etiological agent of human chronic gastritis, peptic ulcer, and gastric cancer. In this study, we synthesized and characterized a series of 14 chalcones and evaluated their anti-H. pylori, NO inhibition (in vitro and in silico), and AGS cells cytotoxic effects. Compounds 3b and 3h showed MIC of 8 μg/mL. We observed structure-activity relationships, mainly related to the influence of methoxy substituent at C-2 (3b) and the nitro group at C-4 (3h) in chalcone scaffold. The fourteen chalcones inhibited the NO production in LPS-stimulated macrophages and showed potential for interaction on the active site of the iNOS enzyme. Finally, 3b and 3h showed the highest selectivity to the AGS cell lines. Thus, ours results suggest 3b and 3h as potential candidates for design of new and effective agents against H. pylori and related diseases.

Mono-Alkyl-Substituted Phosphinoboranes (HRP–BH2–NMe3) as Precursors for Poly(alkylphosphinoborane)s: Improved Synthesis and Comparative Study

A new synthetic pathway to various mono-alkyl-substituted phosphinoboranes HRP–BH2–NMe3 has been developed. The new synthetic route starting from alkyl halides and NaPH2 followed by metalation and salt metathesis is performed in a one-pot procedure and leads to higher yields and purity of the resulting phosphinoboranes, as compared to previously reported routes. Additionally, the scope of accessible compounds could be expanded from short-chained linear alkyl substituents to longer-chained linear alkyl substituents as well as secondary or functionalized alkyl substituents. The reported examples include primary alkyl-substituted phosphinoboranes RHP-BH2-NMe3 (R = n-butyl, n-pentyl, n-hexyl; 1a–c), the secondary alkyl-substituted derivatives iPrPH-BH2-NMe3 (2), and the functionalized alkyl-substituted 4-bromo-butyl-phosphinoborane (BrC4H8)PH-BH2-NMe3 (3). Compounds 1a, 1c, and 2 were additionally used for preliminary polymerization reactions via a thermal and a transition metal-catalyzed pathway, revealing the formation of high-molecular-weight polymers under certain conditions. Detailed investigations on the influence of temperature, concentration, substituents and reaction time on the respective polymerization reactions were performed.