Ar Complexes Research Articles

Redox Activity and Potentials of Bidentate N-Ligands Commonly Applied in Nickel-Catalyzed Cross-Coupling Reactions.

Bidentate N-ligands are paramount to recent advances in nickel-catalyzed cross-coupling reactions. Through comprehensive organometallic, spectroscopic, and computational studies on bi-oxazoline and imidazoline ligands, we reveal that a square planar geometry enables redox activity of these ligands in stabilizing nickel radical species. This finding contrasts with the prior assumption that bi-oxazoline lacks redox activity due to strong mesomeric donation. Moreover, we conducted systematic cyclic voltammetry (CV) analyses of bidentate pyridyl, oxazoline, and imidazoline nitrogen ligands, along with their corresponding nickel complexes. Complexation with nickel shifts the reduction potentials to a more positive region and narrows the differences in redox potentials among the ligands. Additionally, various ligands led to different degrees of bromide dissociation from singly reduced (L)Ni(Ar)(Br) complexes, reflecting varying reactivity in the subsequent activation of alkyl halides, a crucial step in cross-electrophile coupling. These insights highlight the significant electronic effects of ligands on the stability of metalloradical species and their redox potentials, which interplay with coordination geometry. Quantifying the electron-donating, π-accepting properties of these ligands, as well as their effect on catalyst speciation, provides crucial benchmarks for controlling catalytic activity and enhancing catalyst stability.

Photoinduced Group Transposition via Iridium‐Nitrenoid Leading to Amidative Inner‐Sphere Aryl Migration

AbstractWe herein report a fundamental mechanistic investigation into photochemical metal‐nitrenoid generation and inner‐sphere transposition reactivity using organometallic photoprecursors. By designing Cp*Ir(hydroxamate)(Ar) complexes, we induced photo‐initiated ligand activation, allowing us to explore the amidative σ(Ir–aryl) migration reactivity. A combination of experimental mechanistic studies, femtosecond transient absorption spectroscopy, and density functional theory (DFT) calculations revealed that the metal‐to‐ligand charge transfer enables the σ(N−O) cleavage, followed by Ir‐acylnitrenoid generation. The final inner‐sphere σ(Ir–aryl) group migration results in a net amidative group transposition.

Photoinduced Group Transposition via Iridium-Nitrenoid Leading to Amidative Inner-Sphere Aryl Migration.

We herein report a fundamental mechanistic investigation into photochemical metal-nitrenoid generation and inner-sphere transposition reactivity using organometallic photoprecursors. By designing Cp*Ir(hydroxamate)(Ar) complexes, we induced photo-initiated ligand activation, allowing us to explore the amidative σ(Ir-aryl) migration reactivity. A combination of experimental mechanistic studies, femtosecond transient absorption spectroscopy, and density functional theory (DFT) calculations revealed that the metal-to-ligand charge transfer enables the σ(N-O) cleavage, followed by Ir-acylnitrenoid generation. The final inner-sphere σ(Ir-aryl) group migration results in a net amidative group transposition.

Double trouble for prostate cancer: synergistic action of AR blockade and PARPi in non-HRR mutated patients.

Prostate cancer (PCa) is the most common cancer in men worldwide. Despite better and more intensive treatment options in earlier disease stages, a large subset of patients still progress to metastatic castration-resistant PCa (mCRPC). Recently, poly-(ADP-ribose)-polymerase (PARP)-inhibitors have been introduced in this setting. The TALAPRO-2 and PROpel trials both showed a marked benefit of PARPi in combination with an androgen receptor signaling inhibitor (ARSI), compared with an ARSI alone in both the homologous recombination repair (HRR)-mutated, as well as in the HRR-non-mutated subgroup. In this review, we present a comprehensive overview of how maximal AR-blockade via an ARSI in combination with a PARPi has a synergistic effect at the molecular level, leading to synthetic lethality in both HRR-mutated and HRR-non-mutated PCa patients. PARP2 is known to be a cofactor of the AR complex, needed for decompacting the chromatin and start of transcription of AR target genes (including HRR genes). The inhibition of PARP thus reinforces the effect of an ARSI. The deep androgen deprivation caused by combining androgen deprivation therapy (ADT) with an ARSI, induces an HRR-like deficient state, often referred to as "BRCA-ness". Further, PARPi will prevent the repair of single-strand DNA breaks, leading to the accumulation of DNA double-strand breaks (DSBs). Due to the induced HRR-deficient state, DSBs cannot be repaired, leading to apoptosis.

Promises of Plasmonic Antenna-Reactor Systems in Gas-Phase CO2 Photocatalysis.

Sunlight-driven photocatalytic CO2 reduction provides intriguing opportunities for addressing the energy and environmental crises faced by humans. The rational combination of plasmonic antennas and active transition metal-based catalysts, known as "antenna-reactor" (AR) nanostructures, allows the simultaneous optimization of optical and catalytic performances of photocatalysts, and thus holds great promise for CO2 photocatalysis. Such design combines the favorable absorption, radiative, and photochemical properties of the plasmonic components with the great catalytic potentials and conductivities of the reactor components. In this review, recent developments of photocatalysts based on plasmonic AR systems for various gas-phase CO2 reduction reactions with emphasis on the electronic structure of plasmonic and catalytic metals, plasmon-driven catalytic pathways, and the role of AR complex in photocatalytic processes are summarized. Perspectives in terms of challenges and future research in this area are also highlighted.

Structures of the (Imidazole)nH+ ... Ar (n=1,2,3) complexes determined from IR spectroscopy and quantum chemical calculations

Here, we present new cryogenic infrared spectra of the (Imidazole)_{n}mathrm{H}^{+} (n=1,2,3) ions. The data was obtained using helium tagging infrared predissociation spectroscopy. The new results were compared with the data obtained by Gerardi et al. (Chem. Phys. Lett. 501:172–178, 2011) using the same technique but with argon as a tag. Comparison of the two experiments, assisted by theoretical calculations, allowed us to evaluate the preferable attachment positions of argon to the (Imidazole)_{n}mathrm{H}^{+} frame. Argon attaches to nitrogen-bonded hydrogen in the case of the (Imidazole)H^+ ion, while in (Imidazole)_{2}mathrm{H}^{+} and (Imidazole)_{3}mathrm{H}^{+} the preferred docking sites for the argon are in the center of the complex. This conclusion is supported by analyzing the spectral features attributed to the N–H stretching vibrations. Symmetry adapted perturbation theory (SAPT) analysis of the non-covalent forces between argon and the (Imidazole)_{n}mathrm{H}^{+} (n=1,2,3) frame revealed that this switch of docking preference with increasing complex size is caused by an interplay between induction and dispersion interactions.

A Full-Dimensional ab initio Intermolecular Potential Energy Surface and Dipole Moment Surfaces for H2O-Ar

Background: The H2O–Ar system has attracted significant interest in recent years because it is an important model to study inelastic scattering between atoms and triatomic molecules. A high-accuracy intermolecular potential energy surface (IPES) is the foundation for theoretical study on molecular collision dynamics for H2O–Ar. In addition, dipole moment surfaces (DMSs) are one of the prerequisites for spectral simulation. Objective: This study aimed to obtain a full-dimensional intermolecular potential energy surface and dipole moment surfaces for the van der Waals complex H2O–Ar. Methods: In this study, ab initio energy points were computed at the frozen-core (FC) explicitly correlated coupled-cluster [FC-CCSD(T)-F12a] level, with the augmented correlation-consistent polarized valence quadruple-zeta basis set plus bond functions. The permutation invariant polynomial neural network (PIP-NN) approach is adopted to fit the IPES, while the DMSs are constructed at the MP2/AVTZ level and fitted by the NN approach. Results: With a root-mean-square-error (RMSE) of 0.284 cm-1, the IPES can accurately describe the motion of the H2O–Ar complex between R = 4 and 20 a0 in the energy range up to 10000 cm-1. The fitting errors of all the data points are 6.192 and 6.509 mDebye for the X and Z components, respectively. The global minimum of -140.633 cm-1 has the plane geometry, while the dipole moment of H2O–Ar is 1.853 Debye at the equilibrium structure. Conclusion: In summary, we report a full-dimensional intermolecular potential energy surface for H2O–Ar. The IPES precisely reproduces CCSD(T)-F12a electronic energies with a large basis set. The corresponding dipole moment surfaces have also been reported. In comparison with previous work, the employment of the high-level ab initio method will make our IPES more reliable. Several typical 2D contour plots of the IPES and DMSs are also shown. The argon atom has a weak effect on the dipole moment of the H2O–Ar complex. The FORTRAN codes to generate 6D potentials and dipole moments reported here are available on request from the authors.

The role of tagging atoms on the thermal stability and vibrational behavior of Nb9 clusters

Extensive comparative study of density functional theory calculations dedicated to analyzed the influence of the so-called tagging atoms on the thermal stability and vibrational behavior of small Nb9—Arn (n = 1–4) clusters are presented. We consider two-hybrid functional (HSEH1PBE and CAM-B3LYP) models to obtain minimum energy structures and, the relative concentrations of several Ar complexes configurations when varying the temperature of the system are determined by constructing partition functions and enthalpies. Under these considerations, it was found that the coexistence of two different isomers of the Nb9 clusters in a sample is highly probable. Additionally, some interesting points can be highlighted, for instance, i) the different hybrid exchange-correlation functionals modify the proportions of mole fractions in all cases, ii) the weighted average of the IR spectra proposed by the mole fractions have better agreement with the experimental data, iii) tagging atoms can induce significant variations in the infrared spectra, such variations consist mainly of noticeable changes in the relative intensity of the active infrared frequencies. In conclusion, even if the percentage of isomers shown in the mole fractions changes as a function of the hybrid exchange-correlation functional, the influence of tagging atoms makes some changes in the calculation of the partition function and in the simulated IR spectra. For this reason, it is suggested to include tagging atoms in theoretical calculations to have a better understanding of the experimental data.

Symmetry-Adapted Perturbation Theory Based on Multiconfigurational Wave Function Description of Monomers.

We present a formulation of the multiconfigurational (MC) wave function symmetry-adapted perturbation theory (SAPT). The method is applicable to noncovalent interactions between monomers which require a multiconfigurational description, in particular when the interacting system is strongly correlated or in an electronically excited state. SAPT(MC) is based on one- and two-particle reduced density matrices of the monomers and assumes the single-exchange approximation for the exchange energy contributions. Second-order terms are expressed through response properties from extended random phase approximation (ERPA). The dispersion components of SAPT(MC) have been introduced in our previous works [HapkaM.J. Chem. Theory Comput.2019, 15, 1016−102730525591; HapkaM.J. Chem. Theory Comput.2019, 15, 6712–672331670950]. SAPT(MC) is applied either with generalized valence bond perfect pairing (GVB) or with complete active space self-consistent field (CASSCF) treatment of the monomers. We discuss two model multireference systems: the H2 ··· H2 dimer in out-of-equilibrium geometries and interaction between the argon atom and excited state of ethylene. Using the C2H4* ··· Ar complex as an example, we examine second-order terms arising from negative transitions in the linear response function of an excited monomer. We demonstrate that the negative-transition terms must be accounted for to ensure qualitative prediction of induction and dispersion energies and develop a procedure allowing for their computation. Factors limiting the accuracy of SAPT(MC) are discussed in comparison with other second-order SAPT schemes on a data set of small single-reference dimers.

Determining the source and eruption dynamics of a stealth CME using NLFFF modelling and MHD simulations

Context. Coronal mass ejections (CMEs) that exhibit weak or no eruption signatures in the low corona, known as stealth CMEs, are problematic as upon arrival at Earth they can lead to geomagnetic disturbances that were not predicted by space weather forecasters. Aims. We investigate the origin and eruption of a stealth event that occurred on 2015 January 3 that was responsible for a strong geomagnetic storm upon its arrival at Earth. Methods. To simulate the coronal magnetic field and plasma parameters of the eruption we use a coupled approach. This approach combines an evolutionary nonlinear force-free field model of the global corona with a MHD simulation. Results. The combined simulation approach accurately reproduces the stealth event and suggests that sympathetic eruptions occur. In the combined simulation we found that three flux ropes form and then erupt. The first two flux ropes, which are connected to a large AR complex behind the east limb, erupt first producing two near-simultaneous CMEs. These CMEs are closely followed by a third, weaker flux rope eruption in the simulation that originated between the periphery of AR 12252 and the southern polar coronal hole. The third eruption coincides with a faint coronal dimming, which appears in the SDO/AIA 211 Å observations, that is attributed as the source responsible for the stealth event and later the geomagnetic disturbance at 1 AU. The incorrect interpretation of the stealth event being linked to the occurrence of a single partial halo CME observed by LASCO/C2 is mainly due to the lack of STEREO observations being available at the time of the CMEs. The simulation also shows that the LASCO CME is not a single event but rather two near-simultaneous CMEs. Conclusions. These results show the significance of the coupled data-driven simulation approach in interpreting the eruption and that an operational L5 mission is crucial for space weather forecasting.

Rotational Spectrum and Molecular Structures of the Binary Aggregates of 1,1,1,3,3,3-Hexafluoro-2-propanol with Ne and Ar.

The structures and binding topologies of two binary van der Waals complexes 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)···Ne and ···Ar were investigated. The rotational spectra of these two complexes including several isotopic species containing 20Ne, 22Ne, 40Ar, 13C, and hydroxyl D were measured using a chirped pulse Fourier transform microwave spectrometer and a cavity-based Fourier transform microwave spectrometer. While HFIP was shown to exist in both the gauche and trans configurations based on previous reports, the rare gas atom is predicted to attach to HFIP in several different binding topologies, leading to a total of nine possible structural isomers for each complex. Only one isomer was detected for each species, and it corresponds to the most stable one predicted, based on the comparison of the experimental rotational constants and electric dipole moment components with the theoretical predictions and on the isotopic data. We applied quantum theory of atoms in molecules (QTAIM) and electrostatic potential calculations to examine the different rare gas binding sites and to explore the nature of the interactions in these two complexes and several previously reported alcohol···Ar complexes. The effects of fluorination are also discussed by comparison with the binary complexes of isopropanol···Ne and ···Ar.

Photofragment ion imaging in vibrational predissociation of the H2O+Ar complex ion.

Vibrational predissociation processes of the H2O+Ar complex ion following mid-infrared excitations of the OH stretching modes and bending overtone of the H2O+ unit were studied by photofragment ion imaging. The anisotropy parameters, β, of the angular distributions of the photofragment ions were clearly dependent on the type (branch) of rotational excitation, β > 0 for the P-branch excitations, while β < 0 for the Q-branch excitations, which were consistent with the previous theoretical predictions for the rotationally resolved optical transition of a prolate symmetric top. The translational energy distributions had a similar form, irrespective of the excitation modes. This result suggests that the prepared excited states underwent a common relaxation pathway via the bending or bending overtone state of the H2O+ unit. In addition, the available energy was preferentially distributed into the rotational energy of the H2O+ fragment ions rather than the translational energy. The mechanism of the rotational excitations of the H2O+ fragment ions was discussed based on the steric configuration of the H2O+ and Ar units at the moment of dissociation.

Structural characterization of [M,C,2H]+ products formed by reaction of 5d metal cations Pt+ and Ir+ with ethylene oxide and Ta+ with methane using messenger spectroscopy

Structural characterization of gas-phase [M,C,2H]+ (M = Ta, Ir, Pt), formed by reacting laser ablation formed M+ with ethylene oxide (c-C2H4O) or methane under multiple collision conditions, is achieved using infrared multiple-photon dissociation (IR-MPD) spectroscopy with the intracavity free-electron laser FELICE. After product formation, part of the product distribution is complexed with Ar, allowing for simultaneous recording of IR-MPD spectra of both bare [M,C,2H]+, which dissociates via dehydrogenation, and [M,C,2H]+∙Ar, which loses Ar. Comparison of the spectra with density functional theory (DFT) calculations allows for an internally consistent assignment of the spectra to the Ta+CH2 (3A′′) distorted carbene, Pt+CH2 (2A1) carbene, and to the HIr+CH (1A′) carbyne-hydride. Evidence for a symmetric Ta+CH2∙Ar (3B2) complex is also obtained. For Pt and Ir, these structures match those found in previous work when these species were formed by reaction of M+ with methane, CH4 and CD4. Under the current conditions, no clear signs of the previously observed Ir+CH2 (3A2) carbene product were found, consistent with its higher energy, especially after Ar complexation. Potential energy surfaces for the reactions of Pt+ and Ir+ with c-C2H4O are also computed.

Computational Investigation of Substituent Effect on the Thermodynamics and Kinetics of β-Hydrocarbyl Elimination from a Rhodium(I) Iminyl Complex

This study investigates the effect of different substituents on the β-hydrocarbyl elimination reaction of the Rh(I) iminyl complexes (H3P)3Rh[N=CAr2]; Ar = para-C6H4X (X = NH2, OMe, Me, H, F, COOH, CHO, CN) and formation of (H3P)3Rh–Ar complexes and para-C6H4X(CN) molecules using MPW1PW91-based quantum mechanical calculations. There are correlations between Hammett constants for the para-substituted (σp) functional groups of electron withdrawing (EDGs) and donating (EDGs) groups with the relative energies, thermodynamic parameters and the rate constant of this reaction. Also, the calculated Wiberg indices of the Rh-C bond values are used to illustrate the Rh–N bond cleavage and Rh–C bond formation. The rate constants of the β-hydrocarbyl eliminations are computed from 300 to 1200 K, in gas phase.

Aryl C(sp2)-X Coupling (X = C, N, O, Cl) and Facile Control of N-Mono- and N,N-Diarylation of Primary Alkylamines at a Pt(IV) Center.

We present the first example of an unprecedented and fast aryl C(sp2)–X reductive elimination from a series of isolated Pt(IV) aryl complexes (Ar = p-FC6H4) LPtIVF(py)(Ar)X (X = CN, Cl, 4-OC6H4NO2) and LPtIVF2(Ar)(HX) (X = NHAlk; Alk = n-Bu, PhCH2, cyclo-C6H11, t-Bu, cyclopropylmethyl) bearing a bulky bidentate 2-[bis(adamant-1-yl)phosphino]phenoxide ligand (L). The C(sp2)–X reductive elimination reactions of all isolated Pt(IV) complexes follow first-order kinetics and were modeled using density functional theory (DFT) calculations. When a difluoro complex LPtIVF2(Ar)(py) is treated with TMS–X (TMS = trimethylsilyl; X= NMe2, SPh, OPh, CCPh) it also gives the corresponding products of the Ar–X coupling but without observable LPtIVF(py)(Ar)X intermediates. Remarkably, the LPtIVF2(Ar)(HX) complexes with alkylamine ligands (HX = NH2Alk) form selectively either mono- (ArNHAlk) or diarylated (Ar2NAlk) products in the presence or absence of an added Et3N, respectively. This method allows for a one-pot preparation of diarylalkylamine bearing different aryl groups. These findings were also applied in unprecedented mono- and di-N-arylation of amino acid derivatives (lysine and tryptophan) under very mild conditions.

Comparative Analysis of the Interaction Potentials of the Ozone Molecule with Atoms of Noble Gases: O3–Ar and O3–He Complexes

The interaction energy of the ozone molecule with atoms of noble gases (Ar and He) is analyzed. The coupled cluster methods CCSD(T) and CCSD(T)-F12 with orbital basis sets including electrons from diffuse orbitals (aug-cc-pVXZ for X = D, T, Q, 5, … CBS) have been used. The geometrical configurations corresponding to the structures with global minima are established. The full three-dimensional grids of the interaction potentials with more than 4800(5300) points have been fitted for the O3–Ar(He) complexes with root-mean-square values of 0.421(0.567) cm–1. The interaction energy was additionally calculated for the O3–He complex with one internal coordinate r1 of ozone stretched to Δr1 = 0.2 and 0.4a0.

Analytic intermolecular potential energy surface and first-principles prediction of the rotational profiles for a symmetric top ion-atom complex: A case study of H3O+-Ar.

We presented the first three-dimensional (3D) ab initio intermolecular potential energy surface (PES) for the H3O+-Ar complex. The electronic structure computations were carried out at the explicitly correlated coupled cluster theory-F12 with an augmented correlation-consistent triple zeta basis set. Analytic 3D PES was obtained by least-squares fitting the multi-dimensional Morse/Long-Range (mdMLR) potential model to interaction energies, where the mdMLR function form was applied to the nonlinear ion-atom case for the first time. The 3D PES fitting to 1708 points has root-mean-square deviations of 0.19 cm-1 with only 108 parameters for interaction energies less than 500 cm-1. With the 3D PES of the H3O+-Ar complex, we employed the combined radial discrete variable representation/angular finite basis representation method and Lanczos algorithm to calculate rovibrational energy levels. The rotational profiles of the O-H anti-stretching vibrational bands of v3 +(S)←0+ and v3 -(A)←0- for the H3O+-Ar complex were predicted and were in good agreement with the experimental results.

Electronic Spectrum and Photodissociation Chemistry of the 1-Butyn-3-yl Cation, H3CCHCCH.

The B̃1A' ← X̃1A' electronic spectra of the 1-butyn-3-yl cation (H3CCHCCH+) and the H3CCHCCH+-Ne and H3CCHCCH+-Ar complexes are measured using resonance enhanced photodissociation over the 245-285 nm range, with origin transitions occurring at 35936, 35930, and 35928 cm-1, respectively. Vibronic bands are assigned based on quantum chemical calculations and comparison of the spectra with those of the related linear methyl propargyl (H3C4H2+) and propargyl (H2C3H+) cations. The photofragment ions are C2H3+ (major) and C4H3+ (minor), with the preference for C2H3+ consistent with master equation simulations for a mechanism that involves rapid electronic deactivation and dissociation on the ground state potential energy surface.

A new four-dimensional ab initio potential energy surface and rovibrational spectra for the C2H2–Ar complex

ABSTRACT We report a new four-dimensional potential energy surface for the C2H2–Ar complex involving the and normal modes for the symmetric stretching and asymmetric stretching vibration of the C2H2 molecule. The potential was constructed at the coupled-cluster singles and doubles with noniterative inclusion of connected triples [CCSD(T)]-F12 level with augmented correlation-consistent polarized-valence triple-zeta (aug-cc-pVTZ) basis set supplemented with midpoint bond functions (3s3p2d1f1g). Two vibrationally averaged potentials with C2H2 at the vibrational ground and excited states were obtained by the integration of the potential over the and coordinates. It was found that each averaged potential has two equivalent T-shaped global minima, two equivalent local minima as well as three saddle points among them. The global minima are located at = 3.97 Å, = 61.4°/118.6° with a well depth of 125.47 cm−1. The rovibrational energy levels and bound states were calculated adopting radial discrete variable representation (DVR)/angular finite basis representation (FBR) and the Lanczos algorithm. The calculated band origin for C2H2–Ar is red-shift by −0.9937cm−1 in the region of C2H2, which reproduces the observed value of −1.0749cm−1 successfully. Furthermore, the calculated microwave and infrared transition frequencies are in well good agreement with the experiment data.

Aryl–X Bond-Forming Reductive Elimination from High-Valent Mn–Aryl Complexes

C–X bond reductive elimination and oxidative addition are key steps in many catalytic cycles for C–H functionalization catalyzed by precious metals; however, engaging first row transition metals in these overall 2e– processes remains a challenge. Although high-valent Mn aryl species have been implicated in Mn-catalyzed C–H functionalization, the nature and reactivity of such species remain unelucidated. In this work, we report rare examples of stable, cyclometalated monoaryl MnIII complexes obtained through clean oxidative addition of Ar–Br to MnI(CO)5Br. These isolated MnIII–Ar complexes undergo unprecedented 2e– reductive elimination of the Ar–X (X = Br, I, and CN) bond and MnII induced by 1e– oxidation, presumably via transient reactive MnIV species. Mechanistic studies suggest a nonradical pathway.