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N-Butyl-2,3-bis(dicyclohexylamino)cyclopropenimine (1) crystallizes from benzene and hexanes in the presence of HCl as a monobenzene solvate of the hydrochloride salt, [1H]Cl⋅C6H6 or C31H54N3 +⋅Cl⋅C6H6, in the P21/n space group. The protonation of 1 results in the generation of an aromatic structure based upon the delocalization of the cyclopropene double bond around the cyclopropene ring, giving three intermediate C--C bond lengths of 1.41 A °, and the delocalization of the imine-type C--N double bond, giving three intermediate C--N bond lengths of 1.32 A °. Ion-ion and ion-benzene packing interactions are described and illustrated. [ABSTRACT FROM AUTHOR]

A series of Ca–Mn clusters with the ligand 2-pyridinemethoxide (Py-CH2O) have been prepared with varying degrees of topological similarity to the biological oxygen-evolving complex. These clusters activate water as a substrate in the oxidative degradation of propylene carbonate, with activity correlated with topological similarity to the OEC, lowering the onset potential of the oxidation by as much as 700 mV. [ABSTRACT FROM AUTHOR]

The discovery of solid‐phase, inexpensive transition‐metal‐based water oxidation catalysts is a central goal for renewable energy, and has led to a general consensus that a partially populated metal eg d‐electronic state is desirable, leading to favorable catalysis for certain elements in specific oxidation states. In manganese systems, the key species is manganese(III), whose high‐spin d4 electronic configuration places an unpaired electron in the eg orbital, which is postulated to contribute to electronic and structural features that support catalysis. Based on density functional theory calculations, it is predicted that electron transfer would be facilitated by a catalyst with alternating low‐ and high‐MnIII‐content sheets, which positions neighboring band edges in closer energetic proximity. The preparation of such catalysts is demonstrated for the first time and it is shown that the catalytic activity is maximized in these systems over more uniform, but more MnIII‐rich systems. The best catalyst possesses alternating high‐and low‐average oxidation state sheets with interlayer Cs+ ions, and has an overpotential of 450 mV at 10 mA, which represents an improvement of 250 mV over the best unmodified synthetic potassium birnessites. Using scanning tunneling spectroscopy, bandgap modulations consistent with the theoretically predicted band edge shifts are detected. [ABSTRACT FROM AUTHOR]

The role of geometric frustration of water molecules in the rate of water oxidation in the nanoconfined interlayer of manganese-oxide layered materials (birnessite, buserite) is examined in a well-controlled experiment. Calcium buserite is prepared, and used in a split-batch synthetic protocol to prepare calcium birnessite, sodium buserite, and sodium birnessite, and partially dehydrated sodium birnessite. Thus, four samples are prepared in which features effecting catalytic efficiency (defect density, average manganese oxidation state) are controlled, and the main difference is the degree of hydration of the interlayer (two layers of water in buserites vs. one layer of water in birnessite). Molecular dynamics simulations predict birnessite samples to exhibit geometric water frustration, which facilitates redox catalysis by lowering the Marcus reorganization energy of electron transfer, while buserite samples exhibit traditional intermolecular hydrogen bonding among the two-layer aqeuous region, leading to slower catalytic behavior akin to redox reactions in bulk water. Water oxdiation activity is investigated using chemical and electrochemical techniques, demonstrating and quantifying the role of water frustration in enhancing catalysis. Calculation and experiment demonstrate dehydrated sodium birnessite to be most effective, and calcium buserite the least effective, with a difference in electrocatlytic overpotential of ∼750 mV and a ∼20-fold difference in turnover number. [ABSTRACT FROM AUTHOR]

The properties of catenated nitrogen molecules, molecules containing internal chains of bonded nitrogen atoms, is of fundamental scientific interest in chemical structure and bonding, as nitrogen is uniquely situated in the periodic table to form kinetically stable compounds often with chemically stable N-N bonds but which are thermodynamically unstable in that the formation of stable multiply bonded N2 is usually thermodynamically preferable. This unique placement in the periodic table makes catenated nitrogen compounds of interest for development of high-energy-density materials, including explosives for defense and construction purposes, as well as propellants for missile propulsion and for space exploration. This review, designed for a chemical audience, describes foundational subjects, methods, and metrics relevant to the energetic materials community and provides an overview of important classes of catenated nitrogen compounds ranging from theoretical investigation of hypothetical molecules to the practical application of real-world energetic materials. The review is intended to provide detailed chemical insight into the synthesis and decomposition of such materials as well as foundational knowledge of energetic science new to most chemists. [ABSTRACT FROM AUTHOR]

Hydrogen atom transfer (HAT) reactions of an imidomanganese(V) corrole complex are described. The initial rate-determining HAT reaction has occurred via a concerted proton-electron transfer or a proton transfer followed by electron transfer (PR-ET).

Synthesis of the dinuclear iron-imide cluster core [[[Fe.sub.2][([mu]-NR).sub.2]].sup.2+] is described and its structure elaborated. The protolytic substitution of bis(trimethyl)silylamide ligands by primary amines is an effective method for the synthesis of Fe-NR clusters but the susceptibility of alkyl substituents to [beta]-elimination limits the general applicability of protolytic cluster assembly using alkylamines.

Selective reaction of 2,6-isophthaloyl chloride at the methine positions of two dibenzotetramethyltetraaza[14]annulene (tmtaa) units results in tethering of the macrocycles by either one or two 2,6-isophthaloyl bridging groups. The single tethered dibenzotetramethyltetraaza[14]annulene derivative (SIT-tmtaa) was isolated and characterized by X-ray crystallography, ESI-MS, 1H and 13C NMR. The syn conformation of the two tmtaa units observed in the crystal structure, has tetraaza[14]annulene macrocycles that are more distorted from planarity than in the structure of the parent tmtaa. The di-nickel(ii) complex was prepared and characterized by ESI-HRMS, 1H and 13C NMR. DFT computations place the LUMO on the 2,6-isophthaloyl bridge rather than on the tethered tmtaa units and suggest that the 2,6-isophthaloyl tether provides a level of flexibility in the inter tmtaa distances that is comparable to the Pacman Effect observed for tethered porphyrins. [ABSTRACT FROM AUTHOR]

The crystal structures of two closely related compounds, 1-cyclo­hexyl-2-(2-nitro­phen­yl)-1,3-thia­zolidin-4-one, C15H18N2O3S, (1) and 1-cyclo­hexyl-2-(2-nitro­phen­yl)-1,3-thia­zolidin-4-one 1,1-dioxide, C15H18N2O5S, (2), are presented. These compounds are comprised of three types of rings: thia­zolidinone, nitrophenyl and cyclo­hexyl. In both structures, the rings are close to mutually perpendicular, with inter­planar dihedral angles greater than 80° in each case. The thia­zol­idinone rings in both structures exhibit envelope puckering with the S atom as flap and the cyclo­hexyl rings are in their expected chair conformations. The two structures superpose fairly well, except for the orientation of the nitro groups with respect to their host phenyl ring, with a difference of about 10° between 1 and 2. The extended structure of 1 has two kinds of weak C—H. . .O inter­actions, giving rise to a closed ring formation involving three symmetry-related molecules. Structure 2 has four C—H. . .O inter­actions, two of which are exclusively between symmetry-related thia­zolidinone dioxide moieties and have a parallel `give-and-take-fashion' counterpart. In the other two inter­actions, the nitrophenyl ring and the cyclo­hexane ring each offer an H atom to the two O atoms on the sulfone group. Additionally, a C—H. . .π inter­action between a C—H group of the cyclo­hexane ring and the nitrophenyl ring of an adjacent mol­ecule helps to consolidate the structure. [ABSTRACT FROM AUTHOR]

Tolnaftate, a classic antifungal compound, has been found to crystallize from 1:1 (v/v) acetone-water as large flat colorless needles in the centrosymmetric monoclinic space group P21/c. These crystals contain a 50:50 mixture of the (+ap,-sp,+ac,-ac) and (-ap,+sp,-ac,+ac) conformers. The bond lengths in the central CNOS unit are 1.3444 (19), 1.3556 (18) and 1.6567 (15) A À for C--N, C--O and C--S, respectively, and the CNOS and C3N moieties are flat and nearly coplanar with each other, consistent with the C--N bond possessing partial double-bond character. Tolnaftate and the four most closely related N,N-disubstituted thiocarbamates in the Cambridge Structural Database (CSD) all exist as E-conformational isomers in the solid state. Among these five compounds, tolnaftate is the only one in which the N-tolyl moiety is positioned trans to the S atom, i.e. the N-aryl substituent in each of the other compounds is positioned cis to their respective S atom. Notably, and more importantly, our experimental X-ray structure is unlike all prior theoretical models available for tolnaftate. The implication, either directly or indirectly, is that some of those theoretical models used in earlier studies to explain the spectroscopic properties of tolnaftate and to suggest which protein-ligand interactions are responsible for the binding of tolnaftate to squalene epoxidase are either inappropriate or structurally unreasonable, i.e. the results and conclusions from those prior studies are in need of critical reassessment. [ABSTRACT FROM AUTHOR]

The solid-state structures of the Na+, Li+, and NH4+ salts of the 4,5-dihydroxybenzene-1,3-disulfonate (tiron) dianion are reported, namely disodium 4,5-dihydroxybenzene-1,3-disulfonate, 2Na+·C6H4O8S22-,·-4,5-dihydroxybenzene-1,3-disulfonato-bis[aqualithium(I)] hemihydrate, [Li2(C6H4O8S2)(H2O)2]·0.5H2O, and diammonium 4,5-dihydroxybenzene-1,3-disulfonate monohydrate, 2NH4+·C6H4O8S22-·H2O. Intermolecular interactions vary with the size of the cation, and the asymmetric unit cell, and the macromolecular features are also affected. The sodium in Na2(tiron) is coordinated in a distorted octahedral environment through the sulfonate oxygen and hydroxyl oxygen donors on tiron, as well as an interstitial water molecule. Lithium, with its smaller ionic radius, is coordinated in a distorted tetrahedral environment by sulfonic and phenolic O atoms, as well as water in Li2(tiron). The surrounding tiron anions coordinating to sodium or lithium in Na2(tiron) and Li2(tiron), respectively, result in a three-dimensional network held together by the coordinate bonds to the alkali metal cations. The formation of such a three-dimensional network for tiron salts is relatively rare and has not been observed with monovalent cations. Finally, (NH4)2(tiron) exhibits extensive hydrogen-bonding arrays between NH4+ and the surrounding tiron anions and interstitial water molecules. This series of structures may be valuable for understanding charge transfer in a putative solid-state fuel cell utilizing tiron. [ABSTRACT FROM AUTHOR]

Recent developments in organic crystalline electrolytes for lithium and sodium ion conduction have demonstrated bulk conductivities in the range of 10−4 S cm−1 with negligible grain boundary resistance. Experimental results from EM, XRD, and DSC point to a liquid boundary layer at the crystalline surface in equilibrium with the bulk solid that conducts ions between the grains. In this report we examine this behavior in the electrolyte DMF·LiCl (DMF = N,N-dimethylformamide), which has a bulk conductivity of 1.6 × 10−4 S cm−1, but which decomposes between 360–380 K. Molecular dynamics simulations predict a number of quantitative parameters consistent with experimental observation, such as decomposition temperature (Td(theor) = 380 K, Td(obs) = 360 K), bulk conductivity (σheor = 7 × 10−4, σobs = 1.6 × 10−4) and density (dtheor = 1.209 g mL−1, dobs = 1.306 g mL−1). Further, a number of qualitative properties of the material are predicted by simulation, namely, the crystal packing arrangement, the mechanism of decomposition by expulsion of DMF from the LiCl lattice, the existence of a liquid-like grain boundary layer, and most importantly, negligible grain boundary resistance from increased mobility of ions in the boundary layer vs. the bulk. Finally, from quantum mechanical calculations, various interaction energies between fragmental components explain lattice stability and decomposition of the co-crystal, and highlight the contributions from various possible small aggregates. The theoretical calculations predict decomposition of smaller aggregates, such as those expected in the liquid-like surface, to be more facile than larger aggregates that are more likely to be found in the crystal interior. [ABSTRACT FROM AUTHOR]

Abstract: Two lead complexes, Tetrakis(μ3‐(4‐methyl‐3‐nitrophenyl imido lead (II))) 1, and Bis(2‐nitrodiphenyl amido lead(II)) 2, were prepared by protolysis of bis(bis(trimethylsilyl)amido)lead(II) with two compounds relevant to double‐base propellant stabilizers: 2‐nitrodiphenylamine (NDPA) and 4‐methyl‐3‐nitroaniline. Crystal structures were determined as tetrahydrofuran solvates, and exhibit a number of unusual geometric features, including low lead coordination number. Heats of combustion and formation were determined using bomb calorimetry and converted to energy density using crystallographic densities. Compound 1 has an energy density of 30 MJ/L, whereas 2 was 38.2 MJ/L. [ABSTRACT FROM AUTHOR]

New regimes of energy density in energetic materials may be achieved by replacement of oxidizing nitro groups with stronger oxidants such as oxychlorine species. We report the energetic material 1,3-di- tert-butyltetrazolium-5-imidoperchloratomanganese(II) 2, which crystallizes as an oligomeric cubane cluster. Bomb calorimetry on the amorphous, solvent-free phase gives an energy density of at least 40±3 MJ L−, higher than hydrocarbon combustion in air, more than twice that of traditional energetic nitramines, and ≈70 % higher than that of the unmetalated tetrazolium perchlorate salt without metal linkage. The effects of solid-state structure, charge, and lattice energy on the energy of 2 are discussed. [ABSTRACT FROM AUTHOR]

Birnessite, a layered-structure MnO2, is an earth-abundant functional material with potential for various energy and environmental applications, such as water oxidation. An important feature of birnessite is the existence of Mn(III) within the MnO2 layers, accompanied by interlayer charge-neutralizing cations. Using first-principles calculations, we reveal the nature of Mn(III) in birnessite with the concept of the small polaron, a special kind of point defect. Further taking into account the effect of the spatial distribution of Mn(III), we propose a theoretical model to explain the structure-performance dependence of birnessite as an oxygen evolution catalyst. We find an internal potential step which leads to the easy switching of the oxidation state between Mn(III) and Mn(IV) that is critical for enhancing the catalytic activity of birnessite. Finally, we conduct a series of comparative experiments which support our model. [ABSTRACT FROM AUTHOR]

Polynuclear metal clusters frequently feature geometric structural features not common in traditional coordination chemistry. These structures are of particular interest to bioinorganic chemists studying metallocluster enzymes, which frequently possess remarkably unusual inorganic structures. The structure of the manganese cluster μ5-oxido-di-μ3-phenoxido-hexa-μ-phenoxido-hexakis(pyridine-κ N)hexamanganese(II) pyridine monosolvate, [Mn5(C6H5O)8O(C5H5N)6]·C5H5N or MnII5(μ-OPh)6(μ3-OPh)2(μ5-O)(Py)6·Py, containing an unusual trigonal bipyramidal central oxide, is described. The compound was isolated from a reaction mixture containing bis(trimethylsilylamido)manganese(II) and phenol. The central O atom is presumed to have originated as adventitious water. The molecule crystalizes in a primitive monoclinic crystal system and is presented in the centrosymetric P2/ n space group. The molecule possesses crystallographically imposed twofold symmetry, with the central O atom centred on the twofold axis and surrounded by a distorted trigonal bipyramidal arrangement of Mn atoms, which are further bridged by phenoxide ligands, and terminally ligated by pyridine. A pyridine solvent molecule resides nearby, also situated on a crystallographic twofold axis. The cluster is compared to three closely related previously reported structures. [ABSTRACT FROM AUTHOR]

Due to the flammability of liquid electrolytes used in lithium ion batteries, solid lithium ion conductors are of interest to reduce danger and increase safety. The two dominating general classes of electrolytes under exploration as alternatives are ceramic and polymer electrolytes. Our group has been exploring the preparation of molecular solvates of lithium salts as alternatives. Dissolution of LiCl or LiPF6 in pyridine (py) or vinylpyridine (VnPy) and slow vapor diffusion with diethyl ether gives solvates of the lithium salts coordinated by pyridine ligands. For LiPF6, the solvates formed in pyridine and vinylpyridine, namely tetrakis(pyridine-κ N)lithium(I) hexafluorophosphate, [Li(C5H5N)4]PF6, and tetrakis(4-ethenylpyridine-κ N)lithium(I) hexafluorophosphate, [Li(C7H7N)4]PF6, exhibit analogous structures involving tetracoordinated lithium ions with neighboring PF6− anions in the I and Aea2 space groups, respectively. For LiCl solvates, two very different structures form. catena-Poly[[(pyridine-κ N)lithium]-μ3-chlorido], [LiCl(C5H5N)] n, crystalizes in the P212121 space group and contains channels of edge-fused LiCl rhombs templated by rows of π-stacked pyridine ligands, while the structure of the LiCl-VnPy solvate, namely di-μ-chlorido-bis[bis(4-ethenylpyridine-κ N)lithium], [Li2Cl2(C7H7N)4], is described in the P21/ n space group as dinuclear (VnPy)2Li(μ-Cl)2Li(VnPy)2 units packed with neighbors via a dense array of π-π interactions. [ABSTRACT FROM AUTHOR]