Phosphetene-based polyaromatics: structure-property relationships and chiroptical tuning.

We describe the synthesis of π-extended phosphetene rings (4-member P-rings) flanked with PAH systems of various topologies. These compounds are fully characterized including X-ray diffraction. The impact of both the polyaromatic platform and the P-ring on the structure, and the optical and redox properties are investigated both experimentally and theoretically. Although neither the P centre nor the 4-membered ring significantly takes part in the HOMO or LUMO orbitals, both structural features have an important modulating role in distorting the symmetry of the orbitals, leading to chiroptical properties. The stereogenic P-atom is used as a remote chiral perturbator to induce circularly polarized luminescence of the polyaromatic system. The dissymmetry factor is highly dependent on the polyaromatic topology, as supported by theoretical calculations.

Studies on the Coordination Patterns of Diamine-Bridged Tetraphenoxy Ligands with Group 3 and 4 Metals.

Alkane elimination reactions between the diamino- and dianilino-bridged tetrakis(phenolate) proligands 1a,b-H4 and precursors M(CH2SiMe3)3(THF)2, M(CH2C6H4-o-NMe2)3 (M = Sc and Y), and Hf(CH2Ph)4 were investigated. The diamino-bridged 1a-H4 afforded nonsymmetric complex 2a-Y2 incorporating two metal centers in different coordination environments. This one and other dinuclear compounds 2b-Sc2, 2a-Hf2, and 2b-Hf2 were characterized by NMR spectroscopy, elemental analysis, and X-ray diffraction study (for 2a-Y2 and 2b-Sc2) and turned out to be symmetric in solution. Compound 2a-Y2, upon treatment with 2 equiv of 2-phenylpyridine, afforded symmetric bis(aryl) product 3a-Y2, which was authenticated by NMR spectroscopy and X-ray crystallography. The mechanism of its formation was studied by DFT computations and presumably involves a cooperative reorganization process within the nonsymmetric parent 2a-Y2 to afford a symmetric isomer prior to its reaction with 2-phenylpyridine.

Radical and diradical states of bis(molybdenocene dithiolene) complexes.

The synthesis and characterization of two bis(dithiolene) proligands involving heteroatomic linkers such as 1,4-dithiine and dihydro-1,4-disiline between the two protected dithiolene moieties are described. Two bimetallic complexes involving these heteroatomic bridges between two redox active bis(cyclopentadienyl)molybdenum dithiolene moieties have been synthesized and characterized by electrochemistry, spectroelectrochemistry, and their properties rationalized with (TD-)DFT. Cyclic voltammetry experiments show sequential oxidation of the two redox centers with ΔE values between successive one-electron transfers varying according to the nature of the bridge. Depending on the nature of the heteroatomic bridge, the bis-oxidized complexes exhibit either a diradical character with both radicals essentially localized on the metallacycles, or a closed-shell dicationic state.

Dinuclear group IV metal complexes based on a bis(indenyl)-(E/Z)-stilbene platform: a potential prototype of "photoswitchable" catalysts for olefin polymerization.

The preparation of dizirconium complexes based on a novel bis(indenyl)-(E/Z)-stilbene platform was explored. Negishi coupling between the in situ-generated diorganozincates obtained from the respective o/m/p-(E/Z)-dibromostilbenes and the bromo-functionalized zirconocene (η5-Cp*)(η5-2-methyl-4-bromoindenyl)ZrCl2, or, alternatively, the preparation of bis(indene)stilbene pro-ligands {o/m/p-(E/Z)-BisIndSB}H2 through Negishi coupling of the corresponding dibromostilbenes with 4-bromoindene and subsequent metallation/transmetallation with Cp*ZrCl3 or Zr(NMe2)4, allowed the preparation of a series of dinuclear complexes. These were analyzed by NMR spectroscopy and some of them by iASAP-mass spectrometry and by X-ray diffraction studies. Experimental results were compared with DFT modelling of the targeted dinuclear complexes evidencing that the (E)-complexes are more stable by 7-11 kcal mol-1 than their (Z)-analogues. Thermal, uncontrolled isomerization of (Z)- to (E)-stilbene platform was observed experimentally for some systems, in the course of their synthesis, either from the (Z)-dibromostilbene reagent or on the dinuclear complexes resulting from the Negishi coupling. Photoisomerization of the (E)- and (Z)-{BisIndSB}H2 proligands and of complexes {o-(E)-BisIndSB}(Zr(NMe2)3)2 and {m-(E)-BisIndSB}(ZrCl2Cp*)2 was investigated under a variety of conditions. It proved effective for the proligands but induced decomposition of the dizirconium complexes. Time-dependent DFT (TD-DFT) computations were performed to identify unambiguously the nature of the observed absorption bands and account for decomposition of the complexes. Preliminary ethylene/1-hexene homo- and copolymerization investigations did not evidence putative cooperativity phenomena within these dinuclear systems nor significantly differentiated behavior between the (Z)- and (E)-isomers of a given type of complex under the reaction conditions investigated.

Barium phosphidoboranes and related calcium complexes.

The attempted synthesis of [{Carb}BaPPh2] (1) showed this barium-phosphide and its thf adducts, 1·thf and 1·(thf)2, to be unstable in solution. Our strategy to circumvent the fragility of these compounds involved the use of phosphinoboranes HPPh2·BH3 and HPPh2·B(C6F5)3 instead of HPPh2. This allowed for the synthesis of [{Carb}Ae{PPh2·BH3}] (Ae = Ba, 2; Ca, 3), [{Carb}Ca{(H3B)2PPh2}·(thf)] (4), [{Carb}Ba{PPh2·B(C6F5)3}] (5), [{Carb}Ba{O(B(C6F5)3)CH2CH2CH2CH2PPh2}·thf] (6), [Ba{O(B(C6F5)3)CH2CH2CH2CH2PPh2}2·(thf)1.5] (7) and [Ba{PPh2·B(C6F5)3}2·(thp)2] (8) that were characterised by multinuclear NMR spectroscopy (thp = tetrahydropyran). The molecular structures of 4, 6 and 8 were validated by X-ray diffraction crystallography, which revealed the presence of Ba⋯F stabilizing interactions (ca. 9 kcal mol-1) in the fluorine-containing compounds. Compounds 6 and 7 were obtained upon ring-opening of thf by their respective precursors, 5 and the in situ prepared [Ba{PPh2·B(C6F5)3}2]n. By contrast, thp does not undergo ring-opening under the same conditions but affords clean formation of 8. DFT analysis did not highlight any specific weakness of the Ba-P bond in 1·(thf)2. The instability of this compound is instead thought to stem from the high energy of its HOMO, which contains the non-conjugated P lone pair and features significant nucleophilic reactivity.

Cyclic (amino)(barrelene)carbene Ru-complexes: synthesis and reactivity in olefin metathesis.

The synthesis of ruthenium-complexes with cyclic (amino)(barrelene)carbenes (namely CABCs) as ligands is reported. Isolated in moderate to good yields, these new complexes showed impressive thermal stability at 110 °C over several days. Good catalytic performances were demonstrated in various ring-closing metathesis (RCM), macrocyclic-RCM, ring-closing enyne metathesis (RCEYM), cross-metathesis (CM), and ring-opening cross metathesis (ROCM) reactions.

Synthesis and Chemoinformatic Analysis of Fluorinated Piperidines as 3D Fragments for Fragment-Based Drug Discovery.

The concise synthesis of a small library of fluorinated piperidines from readily available dihydropyridinone derivatives has been described. The effect of the fluorination on different positions has then been evaluated by chemoinformatic tools. In particular, the compounds' pKa's have been calculated, revealing that the fluorine atoms notably lowered their basicity, which is correlated to the affinity for hERG channels resulting in cardiac toxicity. The "lead-likeness" and three-dimensionality have also been evaluated to assess their ability as useful fragments for drug design. A random screening on a panel of representative proteolytic enzymes was then carried out and revealed that one scaffold is recognized by the catalytic pocket of 3CLPro (main protease of SARS-CoV-2 coronavirus).

Δ-Keto-acid/hydroxy-lactone isomerization in some lichen depsides, depsidones and diphenyl ethers.

In some compounds in lichens, the carboxylic acid is ortho-substituted by an 2-oxoalkyl chain. This particular structure induces the existence of δ-keto-acid ka or hydroxy-lactone hl isomers, clearly identified by their NMR data and chemical properties, such as dehydration, methylation and behaviour in thermal conditions. Internal hydrogen bonding between the carboxylic acid and substituent in the ortho' position is proposed as an isomerization modulator: an H-bond acceptor (OCH3) leads to ka isomers, whereas hl isomers are obtained with an H-bond donor (OH).

Threading a Linear Molecule Through a Macrocycle Thanks to Boron: Optical Properties of the Threaded Species and Synthesis of a Rotaxane.

Two BODIPYs and two boron ß-diketonates were threaded through a macrocycle bearing a 2,2'-biphenol unit, showing thus the ability of boron to act as a gathering atom. The new threaded species were characterized by 1D and 2D NMR spectroscopy as well as by X-ray crystallography for one of them and their properties rationalized with quantum chemistry to unravel the vibronic contributions. The BODIPYs exhibited interesting fluorescence features with quantum yields up to 91 % and enhanced photostability compared to their non-threaded homologues. A rotaxane was synthesized using this threading strategy after stoppering and removing the boron with potassium hydroxide.

Phospha-cyanines in Their Ideal Polymethine State: Synthesis and Structure-Property Relationships.

We report the synthesis and full characterization of a family of phosphorus-containing polymethine cyanines (phospha-cyanines). The compounds are easily prepared in two steps, starting from readily available phosphanes. The impact of the P-substituents and the counterions on the structural and optical properties is investigated through a joint experimental/theoretical approach. Based on the study of the single-crystal X-ray diffraction structures, all phospha-cyanines present a bond length alternation close to zero, independently of the substituents and counterions, which indicates an ideal polymethine state. All these compounds display the typical cyanine-like UV-vis absorption with an intense and sharp transition with a vibronic shoulder despite possessing a reverse electronic configuration compared to "classical" cyanines. Time-dependent density-functional theory calculations allowed us to fully rationalize the optical properties (absorption/emission wavelengths, luminescence quantum yields). Interestingly, due to the tetrahedral shape of the P atom, the optical properties are independent of the counterion, which is in marked contrast with N-analogues, which enables predictive engineering of the phospha-cyanines regardless of the medium in which they are used.

Rhodium(i)-catalyzed cascade C(sp2)-H bond alkylation - amidation of anilines: phosphorus as traceless directing group.

We introduce a versatile Rh(i)-catalyzed cascade reaction, combining C(sp2)-H bond functionalization and amidation between N-arylphosphanamines and acrylates. This innovative approach enables the rapid synthesis of dihydroquinolinone scaffolds, a common heterocycle found in various pharmaceuticals. Notably, the presence of the phosphorus atom facilitates the aniline ortho-C(sp2)-H bond activation prior to N-P bond hydrolysis, streamlining one-pot intramolecular amidation. Moreover, we demonstrate the applicability of this reaction by synthesizing an antipsychotic drug. Detailed mechanistic investigations revealed the involvement of a Rh-H intermediate, with substrate inhibition through catalyst saturation.

[(CH3)2NH2]2PdBr4, a layered hybrid halide perovskite semiconductor with improved optical and electrical properties.

Inspired by the success of three-dimensional hybrid perovskites (CH3NH3)PbX3 (X = Cl, Br, I), two-dimensional (2D) organic-inorganic hybrid metal halides have drawn immense attention due to their highly tunable physical properties. Moreover, although 3D hybrid perovskite materials have been reported, the development of new organic-inorganic hybrid semiconductors is still an area in urgent need of investigation. Here, we used the dimethylammonium cation to construct a palladium-based halide perovskite material [(CH3)2NH2]2PdBr4 with a 2D layered structure. This layered perovskite undergoes one endothermic peak at 415 K corresponding to melting of the organic molecule. The thermal stability of the compound is up to about 500 K. The activation energy and conduction mechanisms are discussed, and the optical study shows a gap energy equal to 2.5 eV. The electrical AC conductivity is in the order of 10-4 Ω-1 cm-1, which confirms the semiconductor character of this material and indicates its importance in the optoelectronic domain.

C 1-Symmetric {cyclopentadienyl/indenyl}-metallocene catalysts: synthesis, structure, isospecific polymerization of propylene and stereocontrol mechanism.

A series of new Me2Si-bridged cyclopentadiene/indene proligands {Me2Si(R2',5'2-R3',4'2-Cp)(R2,R4,R5,R6-Ind)H2} (1a-j) with various substitutions both on the indene and cyclopentadiene moieties was prepared. The corresponding C1-symmetric group 4 ansa-metallocene complexes (M = Zr, Hf), namely, {Me2Si(Me4Cp)(Ind)}ZrCl2 (2a-Zr), {Me2Si(Me4Cp)(2-Me,4-Ph-Ind)}MCl2 (2b-M), {Me2Si(Me4Cp)(2-Me,4-Ph,6-tBu-Ind)}ZrCl2 (2c-Zr), {Me2Si(Me4Cp)(2-Me,4-Ph,5-OMe,6-tBu-Ind)}MCl2 (2d-M), {Me2Si(Me4Cp)(2-R',4-(3',5'-tBu2,4'-OMe-C6H2),5-OMe,6-tBu-Ind)}ZrCl2, R' = Me (2e-Zr), R' = Et (2f-Zr), {Me2Si(2,5-Ph2-3,4-Me2-Cp)(2-Me,4-(3',5'-tBu2,4'-OMe-C6H2),5-OMe,6-tBu-Ind)}ZrCl2 (2g-Zr), {Me2Si(Me4Cp)(2-Me,4-(3',6'-tBu2-carbazol-4'-yl)-Ind)}ZrCl2 (2h-Zr), {Me2Si(2,5-Me2,3,4-iPr2-Cp)(2-Me,4-Ph-Ind)}ZrCl2 (2i-Zr), {Me2Si(2,5-Me2,3,4-iPr2-Cp)(2-Me,4-Ph,6-tBu-Ind)}ZrCl2 (2j-Zr) and {Me2Si(Me4Cp)(2-Me-4,5-[a]anthracene-Ind)}MCl2 (2k-Zr) were synthesized and characterized by NMR spectroscopy and mass spectrometry. The solid-state molecular structures of 2b-Zr, 2d-Zr, 2e-Zr, 2f-Zr, 2j-Zr and 2k-Zr were determined by X-ray crystallography. The zirconocene complexes, once activated with MAO in toluene solution, exhibited propylene polymerization activities at 60 °C up to 161 000 kg(PP) mol(Zr)-1 h-1, affording highly isotactic polypropylenes (iPP) with [m]4 up to 96.5% and Tm up to 157 °C. Also, metallocene complexes 2b-e-Zr were supported on SiO2-MAO and evaluated in slurry bulk propylene polymerization at 70 °C, producing iPPs with [m]4 = 91.7-96.6 mol% and low regiodefects (0.2-0.3 mol%) content, with productivities up to 636 000 kg(PP) mol(Zr)-1 h-1. DFT calculations allowed rationalizing a polymerization reaction mechanism occurring through "chain-stationary" enchainment with preference for 1,2-insertions.

Synthesis, characterization and identification of inhibitory activity on the main protease of COVID-19 by molecular docking strategy of (4-oxo-piperidinium ethylene acetal) trioxonitrate.

In this investigation a single crystal of (4-oxo-piperidinium ethylene acetal) trioxonitrate (4-OPEAN) was synthesized by modifying the mechanism of gradual evaporation at ambient temperature. The operational groupings are found in the complex material in the elaborate substance, according to the infrared spectrum. Single crystal X-ray diffraction suggests, (4-OPEAN) with the chemical formula (C7H12NO2)NO3 belongs to the orthorhombic space group Pnma and is centrosymmetric in three dimensions with the aforementioned network configurations, a = 11.7185(8) Å, b = 7.2729(6) Å, c = 11.0163(8) Å, Z = 4, V = 938.89(12) Å3, R = 0.0725 and wR = 0.1762. Many N-H…O and C-H…O hydrogen bridges, both bifurcated and non-bifurcated, link the 4-oxo-piperidinium ethylene acetal cations to the trigonal (NO3-) anions. Molecular geometry and optimal parameters of (4-OPEAN) have been determined via DFT computations at the theory-level B3LYP/6-311 ++ G(d, p), these have been contrasted with the X-ray data already available. Hirshfeld surface analysis has made it possible for the visualization and quantification of relationships between molecules in the crystal composition. Quantum theory atoms in molecules, electron location function, decreased density gradient, and localized orbital locator research have all been used to explore non-covalent interactions in crystal structure. In order to pinpoint both the nucleophilic and electrophilic locations that support hydrogen bond formation, the molecule electrostatic potential was determined. The greatest and lowest energies of occupied and unfilled molecular orbitals, together with additional derived atomic characteristics, show the material to be extremely stable and hard. According to a molecular docking study, 4-OPEAN may exhibit inhibiting effects on the 6Y84 and 7EJY virus proteins from corona (COVID-19).

Regiospecific Reduction of 4,6-Dinitrobenzimidazoles: Synthesis, Characterization, and Biological Evaluation.

The regiospecific reduction of 4,6-dinitrobenzimidazole derivatives leading to the corresponding 4-amino-6-nitrobenzimidazoles was studied. The identification of the formed product structures was accomplished by spectroscopic and X-ray diffraction data. The anticancer and antiparasitic activities of the synthesized compounds were examined, and promising activities against Toxoplasma gondii and Leishmania major parasites were discovered for certain 4,6-dinitrobenzimidazoles in addition to moderate anticancer activities of the 4-amino-6-nitrobenzimidazole derivatives against T. gondii cells. However, the tumor cell experiments revealed a promising sensitivity of p53-negative colon cancer cells to these compounds.

Crystal Chemistry, Optic and Magnetic Characterizations of a New Copper Based Material Templated by Hexahydrodiazepine.

Crystals of the new organic-inorganic material (DAP-H2)[CuBr4] (1); (DAP = hexahydrodiazepine (C5H14N2)) were successfully synthesized by slow evaporation and characterized by single-crystal X-ray diffraction, infrared spectroscopy, thermal analysis, UV-Vis-NIR diffuse reflectance spectroscopy, and magnetic measurements. X-ray investigation demonstrates that 1 crystallizes in the monoclinic space group C2/c. The supramolecular crystal structure of 1 is guided by several types of hydrogen bonding which connect anions and cations together into a three-dimensional network. The optical band gap was determined by diffuse reflectance spectroscopy to be 1.78 eV for a direct allowed transition, implying that it is suitable for light harvesting in solar cells. The vibrational properties of this compound were studied by infrared spectroscopy, while its thermal stability was established by simultaneous TGA-DTA from ambient temperature to 600 °C. The study of the photoresponse behavior of an optoelectronic device, based on (C5H14N2)[CuBr4], has shown a power conversion efficiency (PCE) of 0.0017%, with J sc = 0.0208 mA/cm2, V oc = 313.7 mV, and FF = 25.46. Temperature dependent magnetic susceptibility measurements in the temperature range 1.8-310 K reveal weak antiferromagnetic interactions via the two-halide superexchange pathway [2J/k B = -8.4(3) K].

Circularly Polarized Luminescence from Cyclic (Alkyl)(Amino) Carbene Derived Propellers.

Organic circularly polarized luminescence (CPL)-active molecular emitters featuring dynamic propeller-like luminophores were prepared in one step from cyclic(alkyl)(amino) carbenes (CAACs). These molecules exhibit through-space arene-arene π-delocalization and rapid intramolecular inter-system crossing (ISC) in line with their helical character.

A Bimetallic Benzene-1,2,4,5-Tetrathiolate (btt) Molybdenocene Complex Cp2 Mo(btt)MoCp2 : Radical and Diradical States.

Benzene-1,2,4,5-tetrathiolate (btt) has been used as a bridging ligand to prepare a redox active (molybdenocene dithiolene)-based bimetallic complex Cp2 Mo(btt)MoCp2 , which exhibits four successive electron transfers up to the tetracation. Spectro-electrochemical investigations together with DFT and TD-DFT calculations evidence that the two electroactive MoS2 C2 metallacycles are electronically coupled in the monocationic as in the dicationic state. Two salts of the dication [Cp2 Mo(btt)MoCp2 ]2+ have been structurally characterized with PF6 - and HSO4 - counterions, showing different chair or boat conformations associated with variable folding angles of the two MoS2 C2 metallacycles along the S-S hinge. The bis-oxidized dicationic complex exhibits a diradical character, with both radicals essentially localized on the metallacycles and with antiferromagnetic coupling evidenced from magnetic susceptibility measurements.

Structural insights into interactions of new polymeric (µ-oxo) bridged Cu(II) complexes of taurine with yeast tRNA by spectroscopic and computational approaches and its application towards chemoresistant cancer lines.

RNA-targeted drugs are considered as safe treatment option for the cure of many chronic diseases preventing off-targeted delivery and acute toxic manifestations. FDA has approved many such RNA therapies in different phases of clinical trials, validating their use for the treatment of various chronic diseases. We report herein, new water-soluble (µ-oxo) bridged polymeric Cu(II) complexes of taurine (2-aminoethane sulfonic acid) complexes 1 and 2. The therapeutic potency of 1 and 2 was ascertained by studying biophysical interactions with tRNA/ct-DNA. The experimental results demonstrated that the complexes interacted avidly to nucleic acids through intercalation mode depicting a specific preference for tRNA in comparison to ct-DNA and, moreover 2 showed higher binding propensity than 1. The electrophoretic behaviour of the complexes with plasmid pBR322 DNA and tRNA were examined by gel mobility assay that revealed a concentration-dependent activity with complex 2 performing more efficient cleavage as compared to complex 1. Cytotoxicity results on cancer cell strains displayed higher cytotoxicity than complex 1 against treated cancer cells. The synthesized copper(II) taurine complexes have met the basic criteria of anticancer drug design as they are structurally well-characterized, exhibiting good solubility in water, lipophilic in nature with superior intercalating propensity towards tRNA and cytotoxic in nature.

Single Crystal Investigations, Hirshfeld Surface Analysis, DFT Studies, Molecular Docking, Physico-Chemical Characterization, and Biological Activity of a Novel Non-Centrosymmetric Compound with a Copper Transition Metal Precursor.

A novel organic-inorganic hybrid non-centrosymmetric superconductor material [2-ethylpiperazine tetrachlorocuprate(II)] has been synthesized and investigated by means of Fourier transform infrared spectroscopy, single-crystal X-ray crystallography, thermal analyses, and density functional theory (DFT) studies. The single-crystal X-ray analysis indicates that the studied compound crystallizes in the P212121 orthorhombic space group. Hirshfeld surface analyses have been used to investigate non-covalent interactions. Organic cations [C6H16N2]2+ and inorganic moieties [CuCl4]2- alternatively connect N-H···Cl and C-H···Cl hydrogen bonds. In addition, the energies of the frontier orbitals, highest occupied molecular orbital, lowest unoccupied molecular orbital, the reduced density gradient analyses and quantum theory of atoms in molecules analyses, and the natural bonding orbital are also studied. Furthermore, the optical absorption and photoluminescence properties were also explored. However, time-dependent/DFT computations were utilized to examine the photoluminescence and UV-vis absorption characteristics. Two different methods, 2, 2-diphenyl-1-picryhydrazyl radical and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid radical scavenging, were used to evaluate the antioxidant activity of the studied material. Furthermore, the title material was docked to the SARS-CoV-2 variant (B.1.1.529) in silico to study the non-covalent interaction of the cuprate(II) complex with active amino acids in the spike protein.