Wechselwirkungen in Kristallen, 176. Mitteilung, Redox-Reaktionen von Hexahydropyren: Kristallstrukturen seiner Radikalanion-Salze sowie von Trihydropyrenylium-tetrachloroaluminat und Dichtefunktionaltheorie-Berechnungen

Abstract

Edgar Heilbronner zum 80. Geburtstag gewidmet Redox Reactions of Hexahydropyrene: Crystal Structures of Its Radical-Anion Salts as well as of Trihydropyrenylium Tetrachloroaluminate and Density-Functional-Theory CalculationsHexahydropyrene 1, a doubly propane-1,3-diyl-bridged peri-naphthalene derivative wtih 10 p-electrons allows both oxidation to its cation as well as reduction to its radical-anion salts, which could be crystallized and structurally characterized ± a rather rare case for small unsaturated hydrocarbons. The unexpected formally threefold dehydrogenation by the oxidizing system AlCl 3 /H 2 CCl 2 (Bocks reagent) generated the hitherto unknown 1,2,3-trihydropyrene cation in two polymorphic crystals, which contain 12 p-electrons delocalized over three anellated six-membered rings comprising 13 p-centers. Structural comparison of the altogether four crystallized redox products [K solv 3 with the neutral hydrocarbon 1 reveals only small differences in bond lengths and angles, but establishes solvation contacts, p(h 6 )´´´K coordination in the polymer 2b, the flattening of one molecular half in the trihydropyren cation of 3 and ten H-bonds CH´´´Cl to the AlCl 4 À counter anion of 3. DFT/NBO Charge distributions, calculated based on the experimental structural parameters, show charge accumulation in the propanediyl bridges as well as in the peripheral naphthalene CÀC bonds of the radical anions. The largest changes result expectedly for the formally triply dehydrogenated 1, i.e. the trihydropyren cation of 3, with two slightly positive and partly considerably less negative p-centers.Ausgangspunkte. ± Ungesättigte p-Kohlenwasserstoffe lassen sich in aprotischen Lösungen durch Alkalimetalle zu ihren Molekülanionen reduzieren und die entstehenden Kontaktionen-Multipel kristallisieren sowie strukturell charakterisieren [2] (für ausgewählte neuere Veröffentlichungen über Kontaktionenpaare, s. [3]). Demgegenüber werden Molekülkation-Salze weit seltener isoliert und Paare reduzierter sowie oxidierter Molekülion-Salze desselben p-Kohlenwasserstoffes sind nach Recherche in der Cambridge Structural Database-Raritäten [4].Das 1,2,3,6,7,8-Hexahydropyren (1), ein in seinen peri-Positionen zweifach Propan-1,3-diyl-überbrücktes Naphthalin-Derivat, liegt im Kristall in Sessel-Konformation vor [5] (Schema 1 und Fig. 1) und in Lösung vermutlich im Gleichgewicht mit der WannenKonformation. Für das Molekül-Radikalanion lässt sich das Konformationsgleichgewicht durch Temperatur-abhängige ESR/ENDOR-Messungen nachweisen und die

Structure and Dynamic Behavior of Sodium–Diglyme Complex in the Graphite Anode of Sodium Ion Battery by 2H Nuclear Magnetic Resonance

“…This composition differs from that reported by Kim et al for the electrochemically prepared GIC; they estimated the ratio of Na/diglyme as 1:1 and proposed a corresponding structure of the complex. However, the 2:1 molecule/Na ion ratio was also inferred from cyclic voltammograms examined by Jache et al, and several examples of stable [Na­(diglyme) 2 ] complexes are reported in crystal structures. − Indeed, the optimized structure of a [Na­(diglyme) 2 ] complex, when calculated with a 6-31G basis set and Hartree–Fock method, has a diameter of 0.7–0.8 nm and therefore fits well into the expanded galleries of the GIC (0.84 nm). We therefore conclude that sodium ions in the GIC sample prepared in this research are coordinated by two diglyme molecules.…”