Neutral Complexes Research Articles

HOMO-LUMO energy gaps of complexes of transition metals with single and multi-ring aromatics

Optical and electronic properties of aromatics and their clusters are critical to interpreting phenomena ranging from flame-formed nanoparticles to interstellar dust. These properties are also important to their applications as organic semiconductor materials. Aromatic hydrocarbons often form coordination bonds with metal atoms and cations, forming complexes with electronic properties that differ from their parent aromatics. Metal incorporation to aromatics allows access to a versatile range of optical and electronic properties via the modulation of their band gaps. Here, we investigate the binding of four fourth-row transition metals (titanium, chromium, iron, and nickel) with four aromatic molecules (benzene, naphthalene, pyrene, and coronene), and the HOMO-LUMO energy gap of the metal-aromatic complexes using density functional theory calculations. Neutral and cationic (1+ and 2+) complexes are studied at different geometrical and spin configurations, and their binding energies and HOMO-LUMO gaps are computed for the ground state. It is observed that binding with metals can reduce the HOMO-LUMO gap of the aromatics significantly, and the gap energy of the metal-aromatic complexes is closely correlated with their ionization energy. The number of possible transitions from occupied to unoccupied molecular orbitals was also calculated, showing similar spectral energy features for naphthalene, pyrene, and coronene with and without metal incorporation.

Versatile Electroluminescence Color-Tuning Strategy of an Efficient Light-Emitting Electrochemical Cell (LEC) by an Ionic Additive.

The color-tuning strategies of solid-state light-emitting devices (ss-LEDs) are mainly focused on engineering molecular structures. In this paper, for the first time, we developed a facile strategy for tuning the electroluminescence (EL) color from orange to green through the addition of the ionic additive TBAP (tetrabutylammonium perchlorate). To achieve the active ionic emissive compound for use in a light-emitting electrochemical cell (LEC), the neutral biscyclometalated bromo tetrazole iridium(III) [Ir(ppy)2(BrTz)] was exchanged to its cationic complex, [Ir(ppy)2(BrTz-Me)]ClO4 (ppy = 2-phenyl pyridine, BrTz = 4-bromo-2-pyridine tetrazole, BrTz-Me = 4-bromo-2-pyridine methyl tetrazole) with a new synthetic strategy. This method allows employing neutral Ir-cyclometalated complexes, which are ruled out for use in LECs because of their non-ionic behaviors. In the following, an LEC based on the new cationic [Ir(ppy)2(BrTz-Me)]ClO4 as the emissive layer was fabricated between the FTO (fluorine-doped tin oxide) anode and Ga:In alloy cathode without using any additive or polymers, which makes this configuration the simplest ss-LED so far. By adding the ionic additives, the electroluminescence characteristics of [Ir(ppy)2(BrTz-Me)]ClO4 were dramatically increased, including luminance (L) from 162.8 cd/m2 for the device with an additive to 212.9 and 355.9 cd/m2 for devices containing LiTFSI (bis(trifluoromethane)sulfonamide lithium salt) and TBAP, respectively. In particular, when TBAP was added to the [Ir(ppy)2(BrTz-Me)]ClO4 complex, the irradiance was significantly increased from 166.4 to 220.8 μW/cm2 with an efficacy of 1.78 cd/A and external quantum efficiency (EQE) value of 2.14%. The obtained EL results clearly showed that adding TBAP and LiTFSI significantly improved the electroluminescence characteristics and tuned the electroluminescence color.

Manganese Tricarbonyl Diimine Bromide Complexes as Electrocatalysts for Proton Reduction.

Manganese tricarbonyl diimine complexes bearing pyridine and imidazole ligands have been prepared as electrocatalysts for proton reduction using acetic acid as the proton source. The electron-donor ability of the diimine ligand is found to play an important role in determining the efficiency of the electrocatalysts with [MnBr(pybz)(CO)3] (pybz = 2-(2-pyridyl)benzimidazole) exhibiting the lowest overpotential (0.28 V) toward proton reduction. The [Mn(pybz)(CO)3(MeCN)]+ cationic complex prepared via debromination of [MnBr(pybz)(CO)3] by a silver salt has also been shown to catalyze proton reduction upon its electrochemical reduction. A neutral complex [Mn(pyridine-benzimidazolate)(CO)3(MeCN)], which can be synthesized by reacting [MnBr(pybz)(CO)3] with a strong base, has been detected using IR-SEC (infrared spectroelectrochemistry) as an intermediate species in the catalytic process. Using [MnBr(pybz)(CO)3] as the model electrocatalyst, we have carried out density functional calculations to propose a proton reduction mechanism consistent with our experimental observations.

Competing Routes in the Extraction of Lanthanide Nitrates by 1,10-Phenanthroline-2,9-diamides: An Impact of Structure of Complexes on the Extraction

The fact of the fracture of the extraction curve of lanthanides by 1,10-phenanthroline-2,9-diamides is explained in terms of the structure of complexes, solvent extraction data and quantum chemical calculations. The solvent extraction proceeds in two competing directions: in the form of neutral complexes LLn(NO3)3 and in the form of tight ion pairs {[LLn(NO3)2 H2O]+ (NO3-).

Single crystal investigation, spectroscopic, DFT studies, and in-silico molecular docking of the anticancer activities of acetylacetone coordinated Re(I) tricarbonyl complexes

Acetylacetone was used in the synthesis of the neutral complexes, fac-[Re(Acac)(CO)3(1,2-DiCH3Im)] (Re-1) and fac-[Re(Acac)(CO)3(2-CH3Im)] (Re-2), incorporating the (2 + 1) mixed ligand approach. The synthesized complexes were characterized by FT-IR, NMR, UV/Vis, and XRD. In addition, two new Re(I) tricarbonyl crystal structures (Re-1) and (Re-2) are reported, presenting distorted octahedral coordination of the ligands around the metal center. The spectroscopic, molecular properties, and molecular docking of the synthesized compounds as potential anticancer drug was investigated. Before characterization, the theoretical investigation was carried out using M062X-D3, ωB97XD, and PBE0-D3 methods with Gen and def2-SVP basis set. The binding score obtained upon docking both ligands against the 2w6w receptor is −6.8 kcal/mol and −6.9 kcal/mol respectively. Interestingly when both ligands were docked against the 5w9d receptor, it appears that the Re-1 drug bind more with a binding affinity of −6.7 kcal/mol while the Re-2 ligand was observed to have a binding score of −6.5 kcal/mol.

Anti-cancer study of Ni (II) and Zn (II)- chitosan complexes

Two neutral chitosan polymer complexes with Ni(II) and Zn (II) were prepared and characterized by molar conductivity measurements, IR spectroscopy. The prepared complexes were tested against two types of cancer cell lines {breast cancer (MCF-7) and ovarian cancer (A2780)}. That the Ni-chitosan complex was significantly active then the Zn-chitosan complex with IC50 value is 167.67± 4.6 mg/ml for (MCF-7) and 200.45± 8.23mg/ml for (A2780). Whereas IC50 value of Zn-chitosan complex 189.03± 3.7mg/ml for (MCF-7) and 231.70± 5.25mg/ml for (A2780)

BiCuI4(Pyridine)5 a neutral ligand-supported compound of BiI3 and CuI

Reaction of equimolar pyridine (Py) solutions BiI3 and CuI produces the Py-supported 1:1 bimetallic complex BiCuI4(Py)5 in quantitative yield. The title complex is only the second neutral complex to feature Cu−I−Bi bridging and shows an octahedral trans-[BiI4(Py)2] unit joined to a distorted tetrahedral CuI(Py)3 unit by an iodide bridge. The complex shows low thermal stability, decomposing under modest heating or vacuum to produce a mixture of BiI3 and CuI. Thus, it is a potential entry/precursor to BiI3/CuI chemistry. Natural Localized Molecular Orbital (NLMO) calculations were performed to analyze the nature of the Cu−I−Bi bonds, revealing that the title compound lies on the cusp of being [Cu(Py)3]+[BiI4(Py)2]−. Diffuse reflectance spectroscopy measurements show a strong absorption band with an optical bandgap energy of 1.94 eV. Theoretical density of states (DOS) and time-dependent density functional theory (TD-DFT) experiments to map the electronic structure assign the primary electronic transition as a mixed halide/metal-to-ligand charge transfer between Cu−I−Bi donor orbitals and Py π* acceptor orbitals.

Increasing Anticancer Activity with Phosphine Ligation in Zwitterionic Half-Sandwich Iridium(III), Rhodium(III), and Ruthenium(II) Complexes.

The synthesis and biological assessment of neutral or cationic platinum group metal-based anticancer complexes have been extremely studied, whereas there are few reports on the corresponding zwitterionic complexes. Herein, the synthesis, characterization, and bioactivity of zwitterionic half-sandwich phosphine-imine iridium(III), rhodium(III), and ruthenium(II) complexes were presented. The sulfonated phosphine-imine ligand and a group of zwitterionic half-sandwich P,N-chelating organometallic complexes were fully characterized by nuclear magnetic resonance (NMR), mass spectrum (electrospray ionization, ESI), elemental analysis, and X-ray crystallography. The solution stability of these complexes and their spectral properties were also determined. Notably, almost all of these complexes showed enhanced anticancer activity against model HeLa and A549 cancer cells than the corresponding zwitterionic pyridyl-imine N,N-chelating iridium(III) and ruthenium(II) complexes, which have exhibited inactive or low active in our previous work. The increase in the lipophilic property and intracellular uptake levels of these zwitterionic P,N-chelating complexes appeared to be associated with their superior cytotoxicity. In addition, these complexes showed biomolecular interactions with bovine serum albumin (BSA). The flow cytometry studies indicated that the representative complex Ir1 could induce early-stage apoptosis in A549 cells. Further, confocal microscopy imaging analysis displayed that Ir1 entered A549 cells through the energy-dependent pathway, targeted lysosome, and could cause lysosomal damage. In particular, these complexes could impede cell migration in A549 cells.

Two phosphorescent iridium(III) complexes containing simple l-alanine ligands as efficient sensors for Cu2+ ions

Two neutral iridium complexes Ir1 and Ir2 were synthesized using 2-(4-(trifluoromethyl)phenyl)pyridine (tfmppy) and 1-(4-(trifluoromethyl)phenyl)isoquinoline (tfmpiq) as cyclometalated ligands and l-alanine as ancillary ligand. The emission peaks of Ir1 and Ir2 are located at 518 nm and 610 nm and they exhibit intense green and red luminescence in acetonitrile solution with quantum efficiencies of 0.51 and 0.20. The effect of the modification of cyclometalated ligands on the spectral properties of the complexes was discussed in detail by theoretical calculation. After the addition of Cu2+ ions, the luminescence intensities of Ir1 and Ir2 were quenched by 90 % and 89 % respectively due to the paramagnetic effect formed by the combination of iridium complexes and Cu2+ ions. According to the titration experiment, a good linear relationship was found between the intensity at the emission peak and Cu2+ ions concentrations in the range of 0 μM to 15 μM, and the calculated detection limits were 0.54 μM and 0.59 μM. Moreover, the recognition of Cu2+ ions by Ir1 and Ir2 exhibits high interference and good reversibility. Therefore, complexes Ir1 and Ir2 containing simple amino acid as ancillary ligands can be used as “turn-off” phosphorescence sensors toward Cu2+ ions.

Structure-property relationships of photofunctional diiridium(II) complexes with tetracationic charge and an unsupported Ir–Ir bond

In contrast to the extensively studied dirhodium(II) complexes and iridium(III) complexes, neutral or dicationic dinuclear iridium(II) complexes with an unsupported ligand are underdeveloped. Here, a series of tetracationic dinuclear iridium(II) complexes, featuring the unsupported Ir(II)–Ir(II) single bond with long bond distances (2.8942(4)–2.9731(4) Å), are synthesized and structurally characterized. Interestingly, compared to the previous unsupported neutral or dicationic diiridium(II) complexes, our DFT and high-level DLPNO-CCSD(T) results found the largest binding energy in these tetracationic complexes even with the long Ir(II)–Ir(II) bond. Our study further reveals that London dispersion interactions enhance the stability cooperatively and significantly to overcome the strong electrostatic repulsion between two half dicationic metal fragments. This class of complexes also exhibit photoluminescence in solution and solid states, which, to our knowledge, represents the first example of this unsupported dinuclear iridium(II) system. In addition, their photoreactivity involving the generation of iridium(II) radical monomer from homolytic cleavage was also explored. The experimental results of photophysical and photochemical behaviours were also correlated with computational studies.

Rhenium Tricarbonyl Complexes of Azodicarboxylate Ligands

The excellent π-accepting azodicarboxylic esters adcOR (R = Et, iPr, tBu, Bn (CH2-C6H5) and Ph) and the piperidinyl amide derivative adcpip were used as bridging chelate ligands in dinuclear Re(CO)3 complexes [{Re(CO)3Cl}2(µ-adcOR)] and [{Re(CO)3Cl}2(µ-adcpip)]. From the adcpip ligand the mononuclear derivatives [Re(CO)3Cl(adcpip)] and [Re(CO)3(PPh3)(µ-adcpip)]Cl were also obtained. Optimised geometries from density functional theory (DFT) calculations show syn and anti isomers for the dinuclear fac-Re(CO)3 complexes at slightly different energies but they were not distinguishable from experimental IR or UV-Vis absorption spectroscopy. The electrochemistry of the adc complexes showed reduction potentials slightly below 0.0 V vs. the ferrocene/ferrocenium couple. Attempts to generate the radicals [{Re(CO)3Cl}2(µ-adcOR)]•- failed as they are inherently unstable, losing very probably first the Cl- coligand and then rapidly cleaving one [Re(CO)3] fragment. Consequently, we found signals in EPR very probably due to mononuclear radical complexes [Re(CO)3(solv)(adc)]•. The underlying Cl-→solvent exchange was modelled for the mononuclear [Re(CO)3Cl(adcpip)] using DFT calculations and showed a markedly enhanced Re-Cl labilisation for the reduced compared with the neutral complex. Both the easy reduction with potentials ranging roughly from -0.2 to -0.1 V for the adc ligands and the low-energy NIR absorptions in the 700 to 850 nm range place the adc ligands with their lowest-lying π* orbital being localised on the azo function, amongst comparable bridging chelate N^N coordinating ligands with low-lying π* orbitals of central azo, tetrazine or pyrazine functions. Comparative (TD)DFT-calculations on the Re(CO)3Cl complexes of the adcpip ligand using the quite established basis set and functionals M06-2X/def2TZVP/LANL2DZ/CPCM(THF) and the more advanced TPSSh/def2-TZVP(+def2-ECP for Re)/CPCMC(THF) for single-point calculations with BP86/def2-TZVP(+def2-ECP for Re)/CPCMC(THF) optimised geometries showed a markedly better agreement of the latter with the experimental XRD, IR and UV-Vis absorption data.

Metal-Ligand Cooperativity to Assemble a Neutral and Terminal Niobium Phosphorus Triple Bond (Nb≡P).

Decarbonylation along with P-atom transfer from the phosphaethynolate anion, PCO- , to the NbIV complex [(PNP)NbCl2 (Nt BuAr)] (1) (PNP=N[2-Pi Pr2 -4-methylphenyl]2 - ; Ar=3,5-Me2 C6 H3 ) results in its coupling with one of the phosphine arms of the pincer ligand to produce a phosphanylidene phosphorane complex [(PNPP)NbCl(Nt BuAr)] (2). Reduction of 2 with CoCp*2 cleaves the P-P bond to form the first neutral and terminal phosphido complex of a group 5 transition metal, namely, [(PNP)Nb≡P(Nt BuAr)] (3). Theoretical studies have been used to understand both the coupling of the P-atom and the reductive cleavage of the P-P bond. Reaction of 3 with a two-electron oxidant such as ethylene sulfide results in a diamagnetic sulfido complex having a P-P coupled ligand, namely [(PNPP)Nb=S(Nt BuAr)] (4).

Metal‐Ligand Cooperativity to Assemble a Neutral and Terminal Niobium Phosphorus Triple Bond (Nb≡P)

AbstractDecarbonylation along with P‐atom transfer from the phosphaethynolate anion, PCO−, to the NbIV complex [(PNP)NbCl2(NtBuAr)] (1) (PNP=N[2‐PiPr2‐4‐methylphenyl]2−; Ar=3,5‐Me2C6H3) results in its coupling with one of the phosphine arms of the pincer ligand to produce a phosphanylidene phosphorane complex [(PNPP)NbCl(NtBuAr)] (2). Reduction of 2 with CoCp*2 cleaves the P−P bond to form the first neutral and terminal phosphido complex of a group 5 transition metal, namely, [(PNP)Nb≡P(NtBuAr)] (3). Theoretical studies have been used to understand both the coupling of the P‐atom and the reductive cleavage of the P−P bond. Reaction of 3 with a two‐electron oxidant such as ethylene sulfide results in a diamagnetic sulfido complex having a P−P coupled ligand, namely [(PNPP)Nb=S(NtBuAr)] (4).

Experimental and theoretical investigation of a new non-symmetric salamo-like ligand and its tri-nuclear Zn(II) and Ni(II) complexes

Neutral homotrinuclear complexes [{Zn3(L)2(μ-OAc)2}2]·5EtOH and [Ni3(L)2(μ-OAc)2(MeOH)2]·2MeOH were obtained in the reactions of a new non-symmetric salamo-like ligand H2L (5-(N,N′-diethylamino)-2,2′-[ethylenedioxybis(nitrilomethylidyne)]phenolnaphthol) with the respective salts of M(OAc)2·2H2O (M = Zn(II) and Ni(II)), respectively. Single crystals of the ligand were also obtained. All the Zn(Ⅱ) and Ni(Ⅱ) complexes were structurally characterized by single crystal X-ray diffraction. Both Zn(Ⅱ) and Ni(Ⅱ) complexes are composed of two (L)2− units combined with three metal(Ⅱ) ions, where a pair of μ-OAc− ions bridging Zn1⋯Zn2 and Zn2⋯Zn3 or Ni1⋯Ni2 and Ni2⋯Ni1#1 neutralize the charge of the Zn(II) and Ni(II) complexes and stabilize the trinuclear structure. The two μ-OAc− ions are located on the same side of the Zn(Ⅱ) complex, while on different sides of the Ni(Ⅱ) complex. In addition, there are two methanol molecules in the Ni(Ⅱ) complex involved in the coordination. UV–vis absorption spectral analyses showed that the ligand (L)2− units have coordinated with Zn(Ⅱ) and Ni(Ⅱ) atoms. DFT calculations exhibited that the Zn(II) and Ni(II) complexes have higher kinetic stability and lower chemical reactivity. Fluorescence spectrum analyses indicated that the electrons of the ligand have transferred to the empty orbitals (LMCT) of the Zn(Ⅱ) and Ni(Ⅱ) atoms. Furthermore, to discern the interactions in the crystal structures, Hirshfeld surfaces analyses were evaluated. Molecular electrostatic potentials were calculated in order to find electrophilic and nucleophilic sites favorable for hydrogen bonds.

Hybrid Inorganic-Organic Complexes of Zn, Cd, and Pb with a Cationic Phenanthro-diimine Ligand.

The phosphonium-decorated phenanthro-imidazolyl pyridine ligand, LP+Br, readily reacts with zinc(II) and cadmium(II) bromides to give inorganic-organic zero-dimensional compounds [LP+ZnBr2]2[ZnBr4] (1) and [(LP+)2Cd2Br4][CdBr4] (2), respectively, upon crystallization. These salts are moderately fluorescent in the solid state under ambient conditions (λem = 458 nm, Φem = 0.11 for 1; λem = 460 nm, Φem = 0.13 for 2). Their emission results from spin-allowed electronic transitions localized on the organic component with the negligible effect of [MBr4]2- and MBr2 units. Contrary to ionic species 1 and 2, lead(II) bromide affords a neutral and water-stable complex [(LP+)2Pb3Br8] (3), showing weak room-temperature phosphorescence arising from spin-orbit coupling due to the heavy atom effect. The emission, which is substantially enhanced for the amorphous sample of 3 (λem = 575 nm, Φem = 0.06), is assigned to the intraligand triplet excited state, which is a rare phenomenon among Pb(II) molecular materials.

Theoretical Study of Complexes of Tetravalent Actinides with DOTA

1,4,7,10-Tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid (H4DOTA) is a prominent chelating ligand with potential applications in various fields, from radiotherapy to the separation of fission products. The present study explores the stability, structure, and bonding properties of its complexes with tetravalent actinides (An = Th, U, Np, Pu) using density functional theory and relativistic multireference calculations. Neutral complexes prefer to form symmetric (C4) structures with DOTA. The first coordination sphere of the actinide ions is readily saturated by a weakly bonded H2O ligand. The latter ligand reduces the molecular symmetry while exerting only marginal effects on the properties of the parent complex. An-ligand bonding is mainly electrostatic, but there are also significant charge-transfer contributions from DOTA to the An 6d/5f orbitals. The charge-transfer interactions and the covalent character of bonding increase gradually in the order of Th < U < Np < Pu, as indicated by analysis of the electron density distribution using the Quantum Theory of Atoms in Molecules.

Luminescent “Chugaev-type” cyclometalated iridium(III) complexes synthesized by nucleophilic addition of hydrazine

In this work, we describe a series of six neutral Chugaev-type chelating dicarbene iridium complexes with different cyclometalating ligands. The effects of different cyclometalating ligands on the emission properties of dicarbene iridium complexes are evaluated. The triazole- and NHC-derived cyclometalating ligands combine with the strong σ–donating Chugaev-type dicarbene ligand, resulting in phosphorescence that is blue-shifted compared to previously described analogues. The complexes are synthesized by the nucleophilic addition of hydrazine to cationic bis-isocyanide iridium complexes, characterized by 1H, 13C{1H}, and 19F NMR spectroscopy as well as high-resolution mass spectrometry. Four of the six molecular structures of the dicarbene complexes were determined by X-ray crystallography. Electrochemical properties of the compounds were evaluated by cyclic voltammetry analysis, which provides evidence that the HOMO and LUMO energies are dependent on the cyclometalating ligands employed. All the Chugaev-type iridium complexes exhibit blue to blue-green phosphorescence in solution at 77 K and all but one in poly(methyl methacrylate) (PMMA) thin films at room temperature. Although the quantum yields for all the complexes are modest, we succeeded in blue-shifting the emission wavelength of these dicarbene-type iridium complexes.

Synthesis, Characterization, and Catalysis of Water‐Soluble Trimeric and Monomeric Palladium Complexes of 8‐Aminoquinolines

AbstractNew water soluble neutral and cationic palladium complexes were synthesized using 8‐aminoquinoline (8‐AQ) and 2‐methyl 8‐aminoquinoline (2‐Me 8‐AQ) ligands and their catalytic properties were evaluated. The neutral trimeric complexes having a Pd3N3 core were found to form when Pd(OAc)2 was reacted with 8‐AQ or 2‐Me 8‐AQ irrespective of the stoichiometry between the 2 reagents. Controlled addition of triflic acid to the neutral trimeric complex resulted in the formation of a trimeric cationic palladium complex as well as a monomeric cationic complex. A cationic palladium complex having two units of 2‐Me‐8AQ ligand was also synthesized from the cationic monomeric complex. Crystal structures of the new palladium complexes are reported in this study. The water‐soluble neutral palladium complex showed catalytic activity for the oxidation of benzyl alcohols to benzaldehydes, while the cationic palladium complexes were found to be efficient catalysts for the oxidation of styrenes to methyl ketones.

Palladium(II) Complexes with the 4,5‐Bis(diphenylphosphino)acenaphthene Ligand and Their Reactivity with Ethylene

AbstractThe last two decades have witnessed the development of homogeneous catalysts for ethylene homo‐ and co‐polymerization reactions based on late transition metals. When Pd(II) is the metal of choice, the best ligand‐metal combination deals with either bidentate nitrogen‐donor molecules or phosphinobenzene sulfonate derivatives. In this contribution we have investigated the coordination chemistry to Pd(II) of a bidentate phosphorus ligand, namely 4,5‐bis(diphenylphosphino)acenaphthene (1). Starting from the neutral complex, [Pd(1)(CH3)Cl], we obtained the cationic derivatives [Pd(1)(CH3)(L)][SbF6], with L being either CH3CN or 3,5‐lutidine. Using in situ NMR spectroscopy we investigated the reaction of [Pd(1)(CH3)(NCCH3)][SbF6] with ethylene, at room temperature, and ambient ethylene pressure. We discovered that [Pd(1)(CH3)(NCCH3)][SbF6] acts as a catalyst for butenes and hexenes synthesis with the relevant Pd‐ethyl intermediate as the catalyst resting state. At the same time the color of the solution turned from pale yellow to light red due to the formation of the dinuclear species [Pd(μ‐η2−C6H5)PPh)−PPh2]2[SbF6]2. Both the neutral Pd(II) complex, activated in situ by NaSbF6, and the monocationic acetonitrile derivative were tested in the ethylene homopolymerization reaction at high pressure, leading to low molecular weight, branched, polyethylene.

Elucidating behavioral and functional connectivity markers of aberrant threat discrimination in PTSD.

Patients with posttraumatic stress disorder (PTSD) tend to overgeneralize threat to safe stimuli, potentially reflecting aberrant stimuli discrimination. Yet, it is not clear whether threat overgeneralization reflects general discrimination deficits, or rather a specific bias related to aversive stimuli. Here we tested this question and characterized the neural correlates of threat discrimination. One-hundred and eight participants (33 PTSD; 43 trauma-exposed controls; 32 healthy controls) completed an emotionally neutral complex shape discrimination task involving identifying in 42 similar pairs the previously observed shape; and an emotionally aversive discrimination task, involving providing risk ratings for an aversive conditioned stimulus (CS+), and for several stimuli gradually differing in size from the original CS+. Resting state functional connectivity (rsFC) was collected before completing the tasks. No group differences emerged on the emotionally neutral task. Conversely, on the emotionally aversive task, individuals with PTSD had steeper linear risk rating slopes as the stimuli more resembled the conditioned stimulus. Finally, lower rsFC of amygdala-default mode network (DMN) and DMN-salience network (SN) were associated with steeper risk slopes, while for hippocampus-SN, lower rsFC was found only among participants with PTSD. Individuals with PTSD show deficits in discrimination only when presented with aversive stimuli. Dysregulated discrimination pattern may relate to a lack of input from regulatory brain areas (e.g., DMN/hippocampus) to threat-related brain areas (e.g., SN/amygdala).