Andrey Yu. Rogachev

A Main Group Metal Sandwich: Five Lithium Cations Jammed Between Two Corannulene Tetraanion Decks

Characterization of the lithium-ion arrangement between two carbon sheets may ultimately aid in the design of battery electrodes. Lithium-coordinated polyaromatic anions such as tetrareduced corannulene, C20H104− (14−), are useful substrates to model and ultimately improve the graphitic electrodes in lithium-ion (Li+) batteries. Previous studies suggested that 14− forms dimers encasing four Li+ ions in solution. Here, we report a single-crystal x-ray diffraction analysis confirming the formation of a sandwich-type supramolecular aggregate with a high degree of alkali metal intercalation. In contrast to the prior model, our data reveal that five Li+ ions are sandwiched between the two tetrareduced corannulene decks, and 7Li nuclear magnetic resonance spectroscopy delineates a conserved structure in tetrahydrofuran solution. Remarkably, the sandwich is robust in both solution and solid states even in the presence of crown ethers that compete for Li+ coordination. These results should help elucidate Li+ intercalation motifs between curved carbon surfaces more broadly.

Isolation and Hydrogenation of a Complex with a Terminal Iridium–Nitrido Bond

An N for Ir: The synthesis and X-ray crystal structure of a late-transition-metal complex with a terminal nitrido ligand and its hydrogenation to the related amido complex are reported (see scheme).

Selective endo and exo binding of alkali metals to corannulene.

The ion size matters: the structures of corannulene monoanions crystallized with Cs(+) and Rb(+) ions in the presence of [18]crown-6 reveal the intrinsic binding preferences of alkali metals and allow evaluation of the bowl deformation caused by negative charge distribution and metal binding. The large cesium cation coordinates exclusively to the concave face of C(20) H(10)(-), whereas the smaller rubidium cation exhibits convex binding.

A Strain‐Releasing Trap for Highly Reactive Electrophiles: Structural Characterization of Bowl‐Shaped Arenium Carbocations

In addition toits own unique properties, corannulene serves as a primarymodel for both theoretical and experimental studies for avariety of curved carbon networks ranging from fullerenes tonanotubes.Todate,theorganicreactionsofcorannulenehavebeen mainly limited tothe derivatization of its exteriorand tosynthetic transformations of rim-bound functional groups.

Clamshell Opening in the Mixed‐Metal Supramolecular Aggregates Formed by Fourfold Reduced Corannulene for Maximizing Intercalated Metal Content

The first members of a new class of supramolecular organometallic compounds with mixed-alkali-metal cluster cores, LiK5 and Li3 K3 , sandwiched between two four-fold reduced corannulene decks are prepared and fully characterized. The triple-decker supramolecular anions, [(C20 H10 (4-) )(LiK5 )(6+) (C20 H10 (4-) )](2-) and [(C20 H10 (4-) )(Li3 K3 )(6+) (C20 H10 (4-) )](2-) , illustrate a record ability of bowl-shaped and highly charged corannulene to provide all its sites, five benzene rings fused to a central five-membered ring, for binding of six alkali-metal ions. The previously unseen engagement of the hub-site of C20 H10 (4-) in lithium binding is accompanied by unprecedented shifts up to -24 ppm in (7) Li NMR spectra. The discussion of product formation mechanism, augmented by calculations, is provided.

Insights Into Metal−π Arene Interactions of the Highly Lewis Acidic Rh24+ Core with a Broad Set of π-Ligands: From Ethylene to Corannulene and C60-Fullerene

The first systematic theoretical investigation of interactions of the Lewis acidic Rh(II) centers with a number of pi-ligands having isolated unsaturated carboncarbon bonds (acetylene and ethylene) or delocalized pi-systems with planar (benzene, naphthalene, acenaphthylene, and pyrene) or curved surfaces (corannulene and the C(3)-hemifullerene), including the C(60)-fullerene, has been undertaken. The effect of size, geometry, site specificity, and curvature of pi-ligands on their interaction energy with Rh(II) has been examined. The geometric and electronic structures of pi-adducts have been modeled at the DFT level of theory by using the hybrid Perdew-Burke-Ernzerhof parameter free exchange-correlation functional (PBE0). The nature of Rh(II)-pi interactions was found to be similar in all products with the bonding energy ranging from 14.59 kcal/mol in the benzene adduct to 50.13 kcal/mol in the fullerene complex. Importantly, the quantitative evaluation of two bonding components, namely, ligand-to-metal and metal-to-ligand contributions, allowed us to rationalize the observed trends in pi-binding affinity of the selected ligands as well as in stability of the resulting products. These trends deduced from DFT calculations are important for considering the synthetic feasibility of novel pi-complexes in these systems.

First direct assembly of molecular helical complexes into a coordination polymer

Luminescent triple-stranded helicates, formed between Tb(iii) ions and bis-acylpyrazolones, were directly assembled into a 1-D polymeric system.

Functionalized Corannulene Carbocations: A Structural Overview

A detailed structural overview of a family of bowl-shaped polycyclic aromatic carbocations of the type [C20 H10 R](+) with different R functionalities tethered to the interior surface of corannulene (C20 H10 ) is provided. Changing the identity of the surface-bound groups through alkyl chains spanning from one to four carbon atoms and incorporating a different degree of halogenation has led to the fine tuning of the bowl structures and properties. The deformation of the corannulene core upon functionalization has been revealed based on X-ray crystallographic analysis and compared for the series of cations with R=CH3 , CH2 Cl, CHCl2 , CCl3 , CH2 CH3 , CH2 CH2 Cl, and CH2 CH2 Br. The resulting carbocations have been isolated with several metal-based counterions, varying in size and coordinating abilities ([AlCl4 ](-) , [AlBr4 ](-) , [(SnCl)(GaCl4 )2 ](-) , and [Al(OC(CF3 )3 )4 ](-) ). A variety of aggregation patterns in the solid state has been revealed based on different intermolecular interactions ranging from cation-anion to π-π stacking and to halogen⋅⋅⋅π interactions. For the [C20 H10 CH2 Cl](+) ion crystallized with several different counterions, the conformation of the R group attached to the central five-membered ring of corannulene moiety was found to depend on the solid-state environment defined by the identity of anions. Solution NMR and UV/Vis investigations have been used to complement the X-ray diffraction studies for this series of corannulene-based cations and to demonstrate their different association patterns with the solvent molecules.

Convex and Concave Encapsulation of Multiple Potassium Ions by Sumanenyl Anions

Herein we report the novel complex consisting of di- and tripotassiumsumanenide, K7(C21H10(2-))2(C21H9(3-))·8THF (2), which was prepared by the treatment of sumanene (C21H12, 1) with excess K metal in THF. The X-ray structural determination revealed unique self-assembly of six potassium ions sandwiched by convex faces of two sumanenyl trianions in addition to novel interaction involving all 15 carbon atoms of three Cp-like moieties on the concave surface of the sumanenyl bowls outside the sandwich. The unique structural features of 2 are rationalized with the help of DFT calculations.

How to Make the σ0π2 Singlet the Ground State of Carbenes

Successful strategies have previously been developed to stabilize the σ(2)π(0) singlet states of carbenes, relative to σ(1)π(1) triplet states. However, little or no attention has been paid to the stabilization of the σ(0)π(2) singlet states. We present two simple strategies to stabilize the σ(0)π(2) singlet states of carbenes, relative to both the σ(2)π(0) singlet and σ(1)π(1) triplet states. These strategies consist of destabilization of the carbene σ orbital by two, adjacent, sp(2) nitrogen lone pairs of electrons and stabilization of the carbene 2p-π orbital by incorporating it into a five-membered ring, containing two double bonds, or into a six-membered ring, containing two double bonds and a sixth atom that has a low-lying empty π orbital. B3LYP, CASPT2, and CCSD(T) calculations have been performed in order to assess the success of these strategies in creating derivatives of cyclopenta-2,4-dienylidene and cyclohexa-2,5-dienylidene with σ(0)π(6) singlet ground states. Differences between the calculated geometries and binding energies of the Xe complexes of the σ(0)π(6) singlet ground state of 2,5-diazacyclopentadienylidene (5) and the σ(2)π(0) singlet states of CH2 and CF2 are discussed.