Extraordinary Modes of Bonding Enabled by the Triquinane Framework

Günbaş, Görkem; Mascal, Mark

doi:10.1021/jo401715s

Cited by 5 publications

(4 citation statements)

References 56 publications

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“…However, these compounds show under crystalline conditions proton localization between nitrogens as exclusive biophysical sites with short N-H and long N•••H bonds. These distances correspond (or differ) with (from) the hydrogen-bridge distances in DNA in dependence of the length of the N-N distance determined by the geometrical constraints of rigid frameworks as clearly demonstrated by Gunbas and Mascal [16]. The short-long distances 1.069Å and 1.733Å, correspond with the hydrogen bonding in the DNA duplex and similar systems.…”

Section: Introductionsupporting

confidence: 65%

A Molecular Description of Superconductivity of Sulfur Hydride and Related Systems under High-Pressure Conditions

Buck¹

2017

OJPC

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It has been shown that the recently discovered sulfur trihydride (H 3 S) can be considered as a superconductor with a transition temperature Tc of 203 Kelvin (K) at 155 GigaPascals (GPa). This is the highest Tc value reported for any superconductor. The established superconductivity occurs via the formation of a molecular system with sulfur atoms arranged on a body-centered cubic lattice. It has been generally accepted that the high Tc value is the result of an efficient electron-phonon interaction. The responsible substance formed by H 2 S under high pressure, may be considered as a compound with H 3 S stoichiometry creating an impressive network with hydrogens. We will focus on the hydrogen bonding between sulfur and hydrogens demonstrating a symmetrical arrangement. The geometry of the individual radical compound in relation to corresponding systems will be discussed. Ab initio calculations based on a linear three-center two-, three-and four-electron type of bonding clearly visualized in combination with the dynamics of the Van't Hoff concept, as described by us in various papers, give a good description of this exclusive network. We also discuss the superconductivity of related phosphorus hydrides and focus on the stability and geometrical differences with respect to the H 3 S system. These differences are significant, demonstrating the diversity in various structures in showing superconductivity.

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Section: Introductionsupporting

confidence: 65%

A Molecular Description of Superconductivity of Sulfur Hydride and Related Systems under High-Pressure Conditions

Buck¹

2017

OJPC

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“…However, although the simplest system[Me–F–Me] + is a stable minimum computationally, the idea that it could exist in solution under any circumstances is far-fetched. In order to imagine a viable system that could at least be generated as a reactive intermediate, certain design precepts must be considered: (1) the fluoronium ion should form intramolecularly; (2) the fluorine atom should be positioned between secondary carbons (primary would render a system very unstable, whereas tertiary carbons are less likely to form a symmetrical fluoronium); (3) we posit that, if an ether linkage can fit comfortably between the two carbon atoms, the isoelectronic, formally positively charged fluorine should as well.…”

Section: Design Of Systemmentioning

confidence: 99%

Search for a Symmetrical C–F–C Fluoronium Ion in Solution: Kinetic Isotope Effects, Synthetic Labeling, and Computational, Solvent, and Rate Studies

et al. 2015

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Recently, we reported evidence for the generation of a symmetrical fluoronium ion (a [C-F-C](+) interaction) in solution from a cage-like precursor, relying heavily on a single isotopic-labeling experiment. Paraphrasing the axiom that a strong claim must be met by as much evidence as possible, we seek to expand upon our initial findings with comprehensive labeling studies, rate measurements, kinetic isotope effect (KIE) experiments, synthetic studies, and computations. We also chronicle the development of the system, our thought process, and how it evolved from a tantalizing indication of fluoronium ion assistance in a dibromination reaction to the final, optimized system. Our experiments show secondary KIE experiments that are fully consistent with a transition state involving fluorine participation; this is also confirmed by a significant remote isotope effect. Paired with DFT calculations, the KIE experiments are indicative of the trapping of a symmetrical intermediate. Additionally, starting with an epimeric in-triflate precursor that hydrolyzes through a putative frontside SNi mechanism involving fluorine participation, KIE studies indicate that an identical intermediate is trapped (the fluoronium ion). Studies also show that the rate-determining step of the fluoronium forming SN1 reaction can be changed on the basis of solvent and additives. We also report the synthesis of a nonfluorinated control substrate to measure a relative anchimeric role of the fluorine atom in hydrolysis versus μ-hydrido bridging. After extensive testing, we can make the remarkable conclusion that our system reacts solely through a "tunable" SN1 mechanism involving a fluoronium ion intermediate. Alternative scenarios, such as SN2 reactivity, do not occur even under forced conditions where they should be highly favored.

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“…Compared to 33, neutral 78 is predicted to have slightly greater curvature and to be even more aromatic by the NICS criterion. 31 Besides 78, new ligands (see, for example, the use of substituted azatriquinane 79 to generate a cyclic Pt 10 ring), 48 new heterotriquianes/triquinacenes like 80-82, 49 and novel rigid macrobicyclic hosts (such as 'molecular diamond anvil' 83, which stabilizes divalent, sp-hybridized fluorine) 50 are just a couple of examples of curios that still lie in the future of this research program. The concepts in Figure 21 are published; many others are the subject of current and future research.…”

Section: The Futurementioning

confidence: 99%

Chemistry of the Heterotriquinanes and Heterotriquinacenes

Hafezi¹,

Mascal²

2021

Synlett

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Triquinanes are tricyclic hydrocarbons that have fused cyclopentane rings. Although there are linear and angular triquinanes that are doubly fused, this Account focuses exclusively on the ‘triquinacane’, or triply fused structure with a heteroatom (nitrogen or oxygen) on the C 3v symmetry axis. Azatriquinane- and oxatriquinane-based species tend to show remarkable and often unexpected chemistry, and have variously comprised the most basic trialkyl amine, a superbasic proton chelate, trigonal pyramidal ligand platforms, novel calixiform hosts, aromatic hemispheres of hetero-C20 fullerenes, cocrystallizing agents for eliminating rotational disorder in fullerene crystals, the first water-stable, chromatographable trialkyloxonium species, the first isolable allylic oxonium species, world-record C–O bond lengths, rapid SN2 reaction at a tertiary center, and R4O2+ (oxadionium) species.1 Introduction2 Azatriquinane3 Azatriquinacene4 Aromatic Azatriquinacene-Based Systems5 Oxatriquinane6 Tetravalent Oxygen7 Oxatriquinacene8 The Future

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Extraordinary Modes of Bonding Enabled by the Triquinane Framework

Cited by 5 publications

References 56 publications

A Molecular Description of Superconductivity of Sulfur Hydride and Related Systems under High-Pressure Conditions

A Molecular Description of Superconductivity of Sulfur Hydride and Related Systems under High-Pressure Conditions

Search for a Symmetrical C–F–C Fluoronium Ion in Solution: Kinetic Isotope Effects, Synthetic Labeling, and Computational, Solvent, and Rate Studies

Chemistry of the Heterotriquinanes and Heterotriquinacenes

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