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Abstract This study investigates the extent of$$\pi $$ $\pi$-orbital delocalization in Kohn-Sham (KS) density functional calculations in relation to the KS delocalization error (DE) for different classes of$$\pi $$ $\pi$-conjugated organic molecules. The set of molecules includes conjugated polyenes, Hückel aromatic cyclic polyenes, cyanines, and merocyanines. The DE, as probed by the curvature of the energyE(N) as a function of the electron numberNin fractional-electron calculations, causes corresponding trends in the extent of the delocalization of the$$\pi $$ $\pi$orbitals when the latter are chosen to be localized. The DE is assessed in comparison with calculations based on ‘optimally tuned’ functionals with range-separated exchange (OT-RSH) and varying fractions of exact exchange in the short-range limit of the interelectronic separation. The OT-RSH calculations produce negligibleE(N) curvature for all tested systems. An interpolation forE(N) proposed in the literature, which only requires integer-Ncalculations, gives excellent agreement with the fractional-NKS data, with the exception of the longer-chain merocyanines in conjunction with Hartree-Fock calculations. The breakdown of the fractional-electron calculations for the latter cases goes along with a triplet instability of the closed-shell singlet electronic structures. 

Abstract Reaction of Tl(OTf) with 2 equiv of bis(diisopropylamino)cyclopropenylidene (BAC) in THF results in formation of [Tl(BAC)₂(OTf)] (1) in moderate yields. Subsequent reaction of1with [K][H₂‐9‐BBN] ([H₂‐9‐BBN]⁻ = dihydrido 9‐boratabicyclo[3.3.1]nonane) in THF results in formation of [Tl(BAC)(μ‐H₂‐9‐BBN)]₂(3), also in moderate yield. Complex3is the first reported thallium borohydride. We attribute its thermal stability to the strong donor ability of the BAC co‐ligand. Both1and3exhibit trigonal pyramidal geometries about Tl⁺in the solid‐state, indicative of the presence of stereochemically active lone pairs. The hydride environment in3is calculated to exhibit a 3.9 ppm downfield shift attributed to spin‐orbit effects from the adjacent Tl center. 

ABSTRACT Access to benzofuran‐2(3H)‐one derivatives from readily available substrates under mild conditions is crucial in the pharmaceutical and plastics industries. We identified (Z)‐3‐(2‐phenylhydrazineylidene)benzofuran‐2(3H)‐one (P) during the recrystallization of (E)‐2‐(2,2‐dichloro‐1‐(phenyldiazenyl)vinyl)phenol using a 96% ethanol solution. The mechanism of the unexpected substrate conversion leading toPis investigated using density functional calculations. The computations revealed that ethanol is required to initiate the reaction viaTS1E, which involves a concerted deprotonation of ethanol by the basic diaza group of the substrate and an ethoxy group attacking the electrophilic center (Cl₂C), with an energy barrier of 28.3 kcal/mol. The resulting intermediate (I1E) is calculated to be unstable and can yield a cyclic chloroacetal adduct with a lower energy barrier of 2.2 kcal/mol via the ring‐closure transition state (TS2E). In the absence of water, the next steps are impossible because water is required to cleave the ether bond, yieldingP. A small amount of water (4% of the recrystallization solvent) can promote further transformation ofI2Evia the transition statesTS3E(∆G^‡ = 11.1 kcal/mol) andTS4E(∆G^‡ = 10.5 kcal/mol). A comparison of the ethanol/water‐ and only water‐promoted free energy profiles shows that the presence of ethanol is crucial for lowering the energy barriers (by about 5 kcal/mol) for the initial two steps leading to the cyclic chloroacetal (I2E), whereas water is then required to initiate product formation. 

Abstract The study of actinide electronic structure and bonding within rigorously controlled environments is fundamental to advancing nuclear applications. Here, we report a new set of isostructural actinide organometallics; An(COT^big)₂, (An = Th, U, Np, and Pu), where COT^bigis the bulky 1,4-bis(triphenylsilyl)-substituted cyclooctatetraenyl dianion (1,4-(Ph₃Si)₂C₈H₆)^2-. The actinide(IV) metallocene sandwiches have a clam-shell structure, offering a new molecular symmetry to exploref-orbital contributions in bonding. Combined experimental and computational studies reveal that An(COT^big)₂complexes strongly differ from the previously published coplanar An(COT)₂sandwiches due to the bent geometry and electron-withdrawing nature of the substituents. While COT^bigdisplays comparatively weaker electron donation, the low-energyf-ftransitions in An(COT^big)₂have increased molar absorptivity consistent with the removal of the parity selection rule and better energetic matching between ligand and actinide 5forbitals as the series is traversed. For Pu(COT^big)₂, covalent mixing of donor 5fmetal orbitals and the ligand-π orbitals is especially strong. 

In this work, we describe the easy synthesis of mercury complexes with the 1,5,9‐trimesityldipyrromethene (MesDPM) ligand. The compounds were characterized using standard analytic methods such as NMR, IR, as well as UV/Vis spectroscopy. The molecular structures in solid state were determined by SC‐XRD experiments. In addition, the 199Hg NMR chemical shifts were determined by measurements and quantum chemical calculations. 

Organometallic cerium(iv) and thorium(iv) alkynyl complexes were synthesized, and compared experimentally and theoretically. A cerium(iv)trans-influence ligand series was observed and analyzed. 

ABSTRACT This work implements a methodology for studying quadrupolar nuclear spin relaxation in ionic liquids. The dynamic behavior of the ions in the liquid is described by ab initio molecular dynamics (aiMD) with forces obtained from density functional theory (DFT) calculations with periodic boundary conditions and a non‐hybrid functional. The electric field gradient (EFG) driving the quadrupolar relaxation was calculated with free boundary conditions, using clusters that contained the ion of interest surrounded by two coordination shells treated quantum mechanically and augmented with a solvation model. Tests showed that EFG calculations using only the first coordination shell, containing five nearest neighbors, also provide a suitable model, because the relaxation rates differ by no more than 4% from the results from the two‐shell solvation. The results of this study show that the relaxation of the deuterated ethylammonium nitrate () occurs within the extreme narrowing regime for a spectrometer magnetic field T and is therefore characterized by the ensemble variance of the EFG and the correlation time associated with the EFG autocorrelation function. The quadrupolar relaxation of demanded molecular dynamics production times longer than 330 ps and averaging over multiple ions, as well as independent trajectories to get suitably converged relaxation rates. The calculated relaxation rate is Hz, about 60% above the rate reported experimentally. However, the approach utilized in the present study has an accuracy similar to, or better than, what has been previously reported for systems involving non‐ionic solvents that required simulations of 100 ps duration or less.