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It has been a long-standing challenge to develop organic molecular capsules for selective anion binding in water.

The photophysical properties and photochemical reactivity of the organometallic mono(cyclooctatetraenide)-Ce(iii) complexes: [(C8H8)Ce(μ-X)(THF)2]2 X = O3SCF3− (1), Cl− (2), were studied.

5-Methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (ROY) is considered to be the most crystalline polymorphic organic molecule discovered to date with 12 fully characterized crystal structures present in the Cambridge Structural Database (CSD). However, metal complexes of ROY have not previously been described. Here, we explore the synthetic chemistry of ROY (denoted as

Highly modular and rational syntheses of titanium compounds containing ditelluride, terminal telluride, and bis(telluride) structural motifs are disclosed in this study. Titanate anions bearing two

A synthetic route has been developed for a series of 3d homobimetallic complexes of Mn, Fe, Co, Ni and Cu using three different pyridyldiimine (PDI) and pyridyldialdimine (PDAI) macrocyclic ligands with ring sizes of 18, 20 and 22 atoms. Crystallographic analyses indicate that while the distances between the metals can be modulated by the size of the macrocycle pocket, the flexibility in the alkyl linkers used to construct the macrocycles enables the ligand to adjust the orientation of the PD(A)I fragments in response to the geometry of the [M(2)(μ-Cl)(2)](2+) core, particularly with respect to Jahn-Teller distortions. Analyses by UV-Vis spectroscopy and SQUID magnetometry revealed deviations from the properties [M(2)(μ-Cl)(2)](2+)-containing complexes bound by standard mononucleating ligands, highlighting the ability of macrocycles to use ring-size to control the magnetic interactions of pseudo-octahedral, high-spin metal centers.

A series of Ca–Mn hemicubane clusters with topological analogy to the biological oxygen evolving complex are prepared. Those with closest structural analogy are active in the electrochemical activation of water in the decomposition of propylene carbonate.

This study presents the role of 5d orbitals in the bonding, and electronic and magnetic structure of Ce imido and oxo complexes synthesized with a tris(hydroxylaminato) [((2- t BuNO)C6H4CH2)3N]3- (TriNO x 3-) ligand framework, including the reported synthesis and characterization of two new alkali metal-capped Ce oxo species. X-ray spectroscopy measurements reveal that the imido and oxo materials exhibit an intermediate valent ground state of the Ce, displaying hallmark features in the Ce LIII absorption of partial f-orbital occupancy that are relatively constant for all measured compounds. These spectra feature a double peak consistent with other formal Ce(iv) compounds. Magnetic susceptibility measurements reveal enhanced levels of temperature-independent paramagnetism (TIP). In contrast to systems with direct bonding to an aromatic ligand, no clear correlation between the level of TIP and f-orbital occupancy is observed. CASSCF calculations defy a conventional van Vleck explanation of the TIP, indicating a single-reference ground state with no low-lying triplet excited state, despite accurately predicting the measured values of f-orbital occupancy. The calculations do, however, predict strong 4f/5d hybridization. In fact, within these complexes, despite having similar f-orbital occupancies and therefore levels of 4f/5d hybridization, the d-state distributions vary depending on the bonding motif (Ce[double bond, length as m-dash]O vs. Ce[double bond, length as m-dash]N) of the complex, and can also be fine-tuned based on varying alkali metal cation capping species. This system therefore provides a platform for understanding the characteristic nature of Ce multiple bonds and potential impact that the associated d-state distribution may have on resulting reactivity.

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The domino Michael/Mannich (DMM) annulation reaction between an N-sulfinyl lithiodienamine and an electrophilic alkene is developed for the synthesis of chiral 2-amino cyclohexenes, a key building block in asymmetric synthesis. The DMM reaction proceeds at low temperature while maintaining the stereochemical fidelity. The product functionalized amino cyclohexenes, here obtained in 55-82% yield with diastereomeric ratios as high as >19:1.

Decarbonylation along with P-atom transfer from the phosphaethynolate anion, PCO

A neutral and mononuclear niobium nitride complex (PNP)NbN(N[tBu]Ar) (PNP− = N[2-PiPr2-4-methylphenyl]2) can be isolated using the redox-active properties of the [PNP]− ligand.

A dinuclear hafnium complex containing the parent imido ligand [(PN)(PNC)Hf=NH{μ

A complex role for chlorine radicals Radicals are atoms or molecules that are highly reactive because they have an unpaired electron. A common means of investigating whether they are involved in a particular reaction is to try to trap them with an acceptor compound. Yang et al. reinvestigated a photoinduced alkane oxidation reaction for which a trapping study had previously implicated alkoxy radicals. Their spectroscopic, kinetic, and isotopic labeling studies revealed that chlorine, rather than alkoxy, was the key radical intermediate; the prior trapping results had stemmed from its complexation with alcohols. Science , abd8408, this issue p. 847

Thermolysis of [

This report describes the first examples of unassisted C(sp)-C(sp

Transmetallation of [VCl

The super electron donor (SED) ability of 2-azaallyl anions has recently been discovered and applied to diverse reactivity, including transition metal-free cross-coupling and dehydrogenative cross-coupling processes. Surprisingly, the redox properties of 2-azaallyl anions and radicals have been rarely studied. Understanding the chemistry of elusive species is the key to further development. Electrochemical analysis of phenyl substituted 2-azaallyl anions revealed an oxidation wave at E1/2 or Epa = −1.6 V versus Fc/Fc+, which is ∼800 mV less than the reduction potential predicted (Epa = −2.4 V vs. Fc/Fc+) based on reactivity studies. Investigation of the kinetics of electron transfer revealed reorganization energies an order of magnitude lower than commonly employed SEDs. The electrochemical study enabled the synthetic design of the first stable, acyclic 2-azaallyl radical. These results indicate that the reorganization energy should be an important design consideration for the development of more potent organic reductants., The super electron donor (SED) capabilities of 2-azaallyl anions has recently been discovered and applied to diverse reactivity; their structures and electron transfer characteristics are reported herein.

A series of tetradentate tris(phosphinimine) ligands (R3P3tren) was developed and bound to CuI to form the trigonal pyramidal, C3v-symmetric cuprous complexes [R3P3tren-Cu][BArF4] (1PR3) (PR3 = PMe3, PMe2Ph, PMePh2, PPh3, PMe2(NEt2), BArF4 = B(C6F5)4). Electrochemical studies on the CuI complexes were undertaken, and the permethylated analog, 1PMe3, was found to display an unprecedentedly cathodic CuI/CuII redox potential (−780 mV vs. Fc/Fc+ in isobutyronitrile). Elucidation of the electronic structures of 1PR3via density functional theory (DFT) studies revealed atypical valence manifold configurations, resulting from strongly σ-donating phosphinimine moieties in the xy-plane that destabilize 2e (dxy/dx2−y2) orbital sets and uniquely stabilized a1 (dz2) orbitals. Support is provided that the a1 stabilizations result from intramolecular electrostatic fields (ESFs) generated from cationic character on the phosphinimine moieties in R3P3tren. This view is corroborated via 1-dimensional electrostatic potential maps along the z-axes of 1PR3 and their isostructural analogues. Experimental validation of this computational model is provided upon oxidation of 1PMe3 to the cupric complex [Me3P3tren-Cu][OTf]2 (2PMe3), which displays a characteristic Jahn–Teller distortion in the form of a see-saw, pseudo-Cs-symmetric geometry. A systematic anodic shift in the potential of the CuI/CuII redox couple as the steric bulk in the secondary coordination sphere increases is explained through the complexes' diminishing ability to access the ideal Cs-symmetric geometry upon oxidation. The observations and calculations discussed in this work support the presence of internal electrostatic fields within the copper complexes, which subsequently influence the complexes' properties via a method orthogonal to classic ligand field tuning., Secondary coordination sphere electrostatic effects tune the valence manifolds of copper centers, impacting molecular geometries, photophysical properties, and redox potentials.

[Image: see text] A high-spin, mononuclear Ti(II) complex, [(Tp(tBu,Me))TiCl] [Tp(tBu,Me–) = hydridotris(3-tert-butyl-5-methylpyrazol-1-yl)borate], confined to a tetrahedral ligand-field environment, has been prepared by reduction of the precursor [(Tp(tBu,Me))TiCl(2)] with KC(8). Complex [(Tp(tBu,Me))TiCl] has a (3)A(2) ground state (assuming C(3v) symmetry based on structural studies), established via a combination of high-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy, solution and solid-state magnetic studies, Ti K-edge X-ray absorption spectroscopy (XAS), and both density functional theory and ab initio (complete-active-space self-consistent-field, CASSCF) calculations. The formally and physically defined Ti(II) complex readily binds tetrahydrofuran (THF) to form the paramagnetic adduct [(Tp(tBu,Me))TiCl(THF)], which is impervious to N(2) binding. However, in the absence of THF, the Ti(II) complex captures N(2) to produce the diamagnetic complex [(Tp(tBu,Me))TiCl](2)(η(1),η(1);μ(2)-N(2)), with a linear Ti=N=N=Ti topology, established by single-crystal X-ray diffraction. The N(2) complex was characterized using XAS as well as IR and Raman spectroscopies, thus establishing this complex to possess two Ti(III) centers covalently bridged by an N(2)(2–) unit. A π acid such as CNAd (Ad = 1-adamantyl) coordinates to [(Tp(tBu,Me))TiCl] without inducing spin pairing of the d electrons, thereby forming a unique high-spin and five-coordinate Ti(II) complex, namely, [(Tp(tBu,Me))TiCl(CNAd)]. The reducing power of the coordinatively unsaturated Ti(II)-containing [(Τp(tBu,Me))TiCl] species, quantified by electrochemistry, provides access to a family of mononuclear Ti(IV) complexes of the type [(Tp(tBu,Me))Ti=E(Cl)] (with E(2–) = NSiMe(3), N(2)CPh(2), O, and NH) by virtue of atom- or group-transfer reactions using various small molecules such as N(3)SiMe(3), N(2)CPh(2), N(2)O, and the bicyclic amine 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene.

Rare earth metal complexes of the proligand H3TriNOx ([(2-tBuNOH)C6H3CH2]3N) have been shown to afford separations of simple mixtures of rare earth metal salts. In particular, separations systems w...

In order to understand the effect of intramolecular proton acidity on CO2 reduction by Mn bipyridyl species, three fac-Mn(CO)3 bipyridine complexes containing intramolecular phenol groups of varyin...

A rare example of a dinuclear iron core with a non-linearly bridged dinitrogen ligand is reported in this work. One-electron reduction of [(tBupyrr2py)Fe(OEt2)] (1) (tBupyrr2py2- = 2,6-bis((3,5-di-tert-butyl)pyrrol-2-yl)pyridine) with KC8 yields the complex [K]2[(tBupyrr2py)Fe]2(μ2-η1:η1-N2) (2), where the unusual cis-divacant octahedral coordination geometry about each iron and the η5-cation-π coordination of two potassium ions with four pyrrolyl units of the ligand cause distortion of the bridging end-on μ-N2 about the FeN2Fe core. Attempts to generate a Et2O-free version of 1 resulted instead in a dinuclear helical dimer, [(tBupyrr2py)Fe]2 (3), via bridging of the pyridine moieties of the ligand. Reduction of 3 by two electrons under N2 does not break up the dimer, nor does it result in formation of 2 but instead formation of the ate-complex [K(OEt2)]2[(tBupyrr2py)Fe]2 (4). Reduction of 1 by two electrons and in the presence of crown-ether forms the tetraanionic N2 complex [K2][K(18-crown-6)]2(tBupyrr2py)Fe]2(μ2-η1:η1-N2) (5), also having a distorted FeN2Fe moiety akin to 2. Complex 2 is thermally unstable and loses N2, disproportionating to Fe nanoparticles among other products. A combination of single-crystal X-ray diffraction studies, solution and solid-state magnetic studies, and 57Fe Mossbauer spectroscopy has been applied to characterize complexes 2-5, whereas DFT studies have been used to help explain the bonding and electronic structure in these unique diiron-N2 complexes 2 and 5.

Multidentate pyrazolate ligands, 2-(5-tert-butylpyrazol-3-yl)-6-(diethylaminomethyl)pyridine (HNNN)Et and 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine (HNNNH), were metalated with PtII to form neu...

Both biological and industrial nitrogen reduction catalysts activate N(2) at multinuclear binding sites with constrained Fe–Fe distances. This contrasts with molecular diiron systems, which routinely form linear N(2) bridges to minimize steric interactions. Model compounds that capture the salient geometric features of N(2) binding by the nitrogenase enzymes and Mittasch catalysts would contribute to understanding their high N(2)-reduction activity. It is shown in the present study that use of a geometrically flexible, dinucleating macrocycle allows for the formation of a bridging N(2) ligand with an unusual Fe–Ct(N2)–Fe angle of 150° (Ct(N2) = centroid of N(2)), a geometry that approximates the α-N(2) binding mode on Fe(111) surfaces that precedes N(2) bond cleavage. The cavity size the macrocycle prevents the formation of a linear Fe–N(2)–Fe unit and leads to orbital interactions that are distinct from those available to the linear configuration.

We report a family of two-dimensional hybrid perovskites (2DHPs) based on phenethylammonium lead iodide ((PEA)$_2$PbI$_4$) that show complex structure in their low-temperature excitonic absorption and photoluminescence (PL) spectra as well as hot exciton PL. We replace the 2-position (ortho) H on the phenyl group of the PEA cation with F, Cl, or Br to systematically increase the cation's cross-sectional area and mass and study changes in the excitonic structure. These single atom substitutions substantially change the observable number of and spacing between discrete resonances in the excitonic absorption and PL spectra and drastically increase the amount of hot exciton PL that violates Kasha's rule by over an order of magnitude. To fit the progressively larger cations, the inorganic framework distorts and is strained, reducing the Pb-I-Pb bond angles and increasing the 2DHP band gap. Correlation between the 2DHP structure and steady-state and time-resolved spectra suggests the complex structure of resonances arises from one or two manifolds of states, depending on the 2DHP Pb-I-Pb bond angle (as)symmetry, and the resonances within a manifold are regularly spaced with an energy separation that decreases as the mass of the cation increases. The uniform separation between resonances and the dynamics that show excitons can only relax to the next-lowest state are consistent with a vibronic progression caused by a vibrational mode on the cation. These results demonstrate that simple changes to the structure of the cation can be used to tailor the properties and dynamics of the confined excitons without directly modifying the inorganic framework., Comment: 39 pages

Biscationic quaternary phosphonium compounds (bisQPCs) represent a promising class of antimicrobials, displaying potent activity against both Gram-negative and Gram-positive bacteria. In this study, we explored the effects of structural rigidity on the antimicrobial activity of QPC structures bearing a two-carbon linker between phosphonium groups, testing against a panel of six bacteria, including multiple strains harboring known disinfectant resistance mechanisms. Using simple alkylation reactions, 21 novel compounds were prepared, although alkene isomerization as well as an alkyne reduction were observed during the respective syntheses. The resulting bisQPC compounds showed strong biological activity, but were hampered by diminished solubility of their iodide salts. One compound (P2P-10,10 I) showed single-digit micromolar activity against the entire panel of bacteria. Overall, intriguing biological activity was observed, with less rigid structures displaying better efficacy against Gram-negative strains and more rigid structures demonstrating slightly increased efficacy against S. aureus strains.

The separation and purification of niobium and tantalum, which co-occur in natural sources, is difficult due to their similar physical and chemical properties. The current industrial method for separating Ta/Nb mixtures uses an energy-intensive process with caustic and toxic conditions. It is of interest to develop alternative, fundamental methodologies for the purification of these technologically important metals that improve upon their environmental impact. Herein, we introduce new Ta/Nb imido compounds: M(

Ligand protonated IrI bisphosphine carbonyl complexes isolated as halide salts equilibrate with their neutral IrIII–H congeners in solution. The equilibrium constant and energy barrier to interconversion are dependent on the identity of the halide.

The domino Michael/Mannich (DMM) annulation reaction between an

This report describes an isostructural series of dinuclear iron, cobalt, and nickel complexes bound by a redox-active macrocyclic ligand. The series spans five redox levels (34–38 e–/cluster core),...

Sodium perchlorate (NaClO4) crystallizes with adiponitrile (ADN) as a 1:3 solvate to produce (ADN)3NaClO4, a solid electrolyte for sodium ion conduction. The solid possesses high thermal stability ...

A series of thorium(IV)-imido complexes was synthesized and characterized. Extensive experimental and computational comparisons with the isostructural cerium(IV)-imido complexes revealed a notably more covalent bonding arrangement for the Ce═N bond compared with the more ionic Th═N bond. The thorium-imido moieties were observed to be 3 orders of magnitude more basic than their cerium congeners. More generally, these results provide unique experimental evidence for the larger covalent character of 4f05d0 Ce(IV) multiple bonds compared to its 5f06d0 Th(IV) actinide congener.

The synthesis of manganese cluster complexes templated by polyhedral oligomeric silsesquioxane-derived ligands is described. MnII3(Ph7Si7O12)2Pyr4 (1) and MnII4(Ph4Si4O8)2(Bpy)2(Py)2 (3) are prepared by replacement of the amide ligands of Mn(NR2)2 (R = SiMe3) via ligand protolysis by the acidic proton of the respective silsesquioxane-derived silanols. Complex 1 is shown to undergo ligand rearrangement by reaction with O2, which results in oxidation of the cluster to a mixed MnII/III cluster, concomitant with cleavage of the Si-O bonds of the ligand, releasing a [Ph2Si-O]+ unit, opening a new ligating siloxide group, and resulting in the formation of Mn3(Ph6Si6O11)2Pyr4 (2). The ligand framework of 1 can also be perturbed by a base. The addition of LiOH/BuLi delivers a soluble equivalent of Li2O to 1, resulting in cleavage of the Si-O bonds and linkage of the resulting exposed silicon atoms by the new oxide, giving a linked ligand variant that templates a Li2Mn3 cluster, Mn3Li2(Ph7Si7O12OPh7Si7O12)DMF5Pyr (4). These systems are characterized by single-crystal X-ray diffraction, absorption spectroscopy, Fourier transform infrared, cyclic voltammetry, and CHN combustion analysis. Mechanistic implications for the Si-O bond cleavage events are discussed.

A series of 2,6-diiminopyridine-derived macrocyclic ligands have been synthesized via [2+2] condensation around alkaline earth metal triflate salts. The inclusion of a tert-butyl group at the 4-position of the pyridine ring of the macrocyclic synthons results in macrocyclic complexes that are soluble in common organic solvents, thereby enabling a systematic comparison of the physical properties of the complexes by NMR spectroscopy, mass spectrometry, solution-phase UV-Vis spectroscopy, cyclic voltammetry and single-crystal X-ray crystallography. Solid-state structures determined crystallographically demonstrate increased twisting in the ligand, concurrent with either a decrease in ion size or an increase in macrocycle ring size (18, 20, or 22 membered rings). The degree of folding and twisting within the macrocycle can be quantified using parameters derived from the N(pyr)-M-N(pyr) bond angle and the relative orientation of the pyridinediimine (PDI) and pyridinedialdimine (PDAI) fragments to each other within the solid state structures. Cyclic voltammetry and UV-Vis spectroscopy were used to compare the relative energies of the imine π* orbital of the redox active PDI and PDAI components in the macrocycle when coordinated to redox inactive metals. Both methods indicate the change from a methyl to hydrogen substitution on the imine carbon lowers the energy of the ligand π* system.

In the crystalline state of the title solvate, C

This communication describes the C–C bond activation of acetonitrile and the trapping of the methyl and cyanide fragments by macrocyclic, dicobalt complexes. Both products display unique structural features as a result of the constraints imposed by the macrocycle. The bridged species [((3)PDI(2))Co(2)(μ-CN)(PMe(3))(2)][OTf] ([Co(2)CN](+)) exhibits atypical Co–CN–Co binding, and upon either phosphine dissociation or oxidation, the flexible ligand framework is able to switch between different binding modes of μ-cyanide. Further, the bridging methyl species [((3)PDI(2))Co(2)(μ-CH(3))(PMe(3))][OTf] ([Co(2)CH(3)](+)) is the first structurally characterized dicobalt complex with a bridging methyl group.

The synthesis of bona fide organometallic CeIV complexes is a formidable challenge given the typically oxidizing properties of the CeIV cation and reducing tendencies of carbanions. Herein, we report a pair of compounds comprising a CeIV − Caryl bond [Li(THF)4][CeIV(κ2-ortho-oxa)(MBP)2] (3-THF) and [Li(DME)3][CeIV(κ2-ortho-oxa)(MBP)2] (3-DME), ortho-oxa = dihydro-dimethyl-2-[4-(trifluoromethyl)phenyl]-oxazolide, MBP2– = 2,2′-methylenebis(6-tert-butyl-4-methylphenolate), which exhibit CeIV − Caryl bond lengths of 2.571(7) – 2.5806(19) Å and strongly-deshielded, CeIV − Cipso 13C{1H} NMR resonances at 255.6 ppm. Computational analyses reveal the Ce contribution to the CeIV − Caryl bond of 3-THF is ~12%, indicating appreciable metal-ligand covalency. Computations also reproduce the characteristic 13C{1H} resonance, and show a strong influence from spin-orbit coupling (SOC) effects on the chemical shift. The results demonstrate that SOC-driven deshielding is present for CeIV − Cipso 13C{1H} resonances and not just for diamagnetic actinide compounds., Ce(IV) organometallic compounds are rare due to Ce(IV) being a powerful oxidant. Herein, the authors explore the covalency of a pair of organocerium complexes bearing a Ce(IV)-C(aryl) bond and examine their structure by NMR spectroscopy, X-ray diffraction analysis, and computational calculations.