Reduction of Carbon‐rich Compounds

Sternfeld, Tamar; Rabinovitz, Mordecai

doi:10.1002/3527607994.ch13

Cited by 9 publications

(5 citation statements)

References 95 publications

(183 reference statements)

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“…The reduction of polycyclic aromatic hydrocarbons (PAHs) attracts significant attention from fundamental and applied viewpoints. − Chemical reduction of PAHs with alkali metals yields negatively charged π-conjugated carbanions which may undergo structural changes − and core transformation, − in addition to reductive dimerization processes. − These reactions also afford new solid materials with intriguing electronic, − conducting, − and magnetic properties. , However, an in-depth understanding of materials properties and structure–property correlations is often impeded by the lack of pure single-crystalline phases. For example, the chemical reduction of triphenylene (C 18 H 12 , 1 ) was first reported by Paul et al back in 1956, revealing a notable color change upon reaction of 1 with alkali metals in THF.…”

Section: Introductionmentioning

confidence: 99%

Tuning Magnetic Interactions Between Triphenylene Radicals by Variation of Crystal Packing in Structures with Alkali Metal Counterions

et al. 2021

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The monoanion of triphenylene (C18H12, 1) was generated in THF using several alkali metals (Na, K, Rb, and Cs) as reducing agents and crystallized with the corresponding cations in the presence of 18-crown-6 ether. The UV–vis spectroscopy points to the metal-dependent coordination environment of the triphenylene monoanion-radicals, 1 ·–, in solution. The X-ray diffraction characterization confirmed the formation of a solvent-separated ion pair (SSIP) with sodium ions, [{Na+(18-crown-6)(THF)2}(1 ·–)] (2), and three contact-ion pair (CIP) complexes formed by larger alkali metal ions, [{K+(18-crown-6)}(1 ·–)] (3), [{Rb+(18-crown-6)}(1 ·–)] (4), and [{Cs+(18-crown-6)}(1 ·–)] (5). Structural analysis of the series reveals a notable geometry perturbation of the triphenylene framework in 2 caused by one-electron acquisition, which is further enhanced by direct metal binding in 3–5. This has been correlated with the aromaticity changes and charge redistribution upon one-electron reduction of 1, as revealed by the computational studies. The EPR spectroscopy and magnetic susceptibility measurements confirm antiferromagnetic interactions corresponding to an S = 1/2 system in the solid state. The magnetic behavior of 3–5 correlates with the arrangement of triphenylene radicals in the crystal structures. All three compounds exhibit antiferromagnetic (AFM) interactions between S = 1/2 radicals in the solid state, but the exchange coupling in 4 and 5 is notably stronger than that in 3, which leads to AFM ordering at 3.8 K in 4 and at 2.0 K in 5. The magnetic phase transitions in 4 and 5 can be interpreted as originating from interactions between the chains of the AFM-coupled S = 1/2 radicals.

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Section: Introductionmentioning

confidence: 99%

Tuning Magnetic Interactions Between Triphenylene Radicals by Variation of Crystal Packing in Structures with Alkali Metal Counterions

et al. 2021

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“…Polycyclic hydrocarbons (PCHs) very often exhibit rich redox chemistry in addition to unique electronic and optical properties. Explorations of the charge distribution, magnetism, electronic structure, and solid-state morphology of redox-active PCHs are well-engrained areas of physical organic chemistry. − The practical application of redox-active PCHs and related materials has seen considerable growth in recent years as the limits of traditional inorganic-based systems are becoming evident. − A related field experiencing a burst of activity involves the synthesis and characterization of PCHs with biradical character. − Typically, high levels of reactivity are associated with the pair of loosely correlated electrons. As a consequence of new synthetic approaches and improved spectroscopic techniques, numerous stable biradical PCHs have been reported in the past decade. , The molecules exhibit many favorable properties, including redox amphoterism, strong absorption in the visible spectrum, small frontier orbital energy gaps (<1.5 eV), large second hyperpolarizabilities, and the opportunity of modulating spin state through thermally accessible triplet states. − …”

Section: Introductionmentioning

confidence: 99%

A Biradical Balancing Act: Redox Amphoterism in a Diindenoanthracene Derivative Results from Quinoidal Acceptor and Aromatic Donor Motifs

et al. 2016

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The reduced and oxidized states of an open-shell diindeno[b,i]anthracene (DIAn) derivative have been investigated by experimental and theoretical techniques. As a result of moderate biradical character and the ability of cyclopenta-fused scaffolds to stabilize both positive and negative charges, DIAn exhibits rich redox chemistry with four observable and isolable charged states. Structural and electronic properties of the DIAn system are brought to light by UV-vis-NIR and Raman spectroelectrochemical measurements. Aromatization of the diindeno-fused anthracene core upon successive single-electron injections is revealed through single-crystal X-ray diffraction of radical anion and dianion salts. We present a rare case where the pseudoaromatic/quinoidal ground state of a neutral biradical polycyclic hydrocarbon leads to a stable cascade of five redox states. Our detailed investigation of the transformation of molecular structure along all four redox events provides a clearer understanding of the nature of charge carriers in ambipolar organic field-effect transistors.

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“…Thus, synthesis of new derivatives based on the system 4 by introducing bulky groups to stabilize the neutral radical state or some alkyl groups as a probe of magnetic resonance measurements at the appropriate positions is underway. Studies on the curved phenalenyl anion provide molecular design criteria of novel polycyclic aromatic hydrocarbon anions for exploration in molecular functionalities and importantly contribute to elucidation of electronic structures of C 70 systems …”

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confidence: 99%

Curve-Structured Phenalenyl Chemistry: Synthesis, Electronic Structure, and Bowl-Inversion Barrier of a Phenalenyl-Fused Corannulene Anion

et al. 2008

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We have demonstrated the features of curve-structured phenalenyl chemistry, for the first time. A phenalenyl-fused corannulene anion has been designed by the annelation of a six-memberd ring across peri-positions of corannulene and generated as a stable species in a degassed solution. The 1H and 13C NMR spectra have shown the highly symmetrical structure and high-field shifts of protons and carbons at the asterisked positions in the chemical structure, indicating the occurrence of large negative charge densities at these positions. These results well agree with the HOMO picture and the electrostatic potential surface, demonstrating the phenalenyl anion-type electronic structure is retained in the curved-surface pi-system. The calculated bowl-inversion barrier of the anion (11.3 kcal/mol) is larger than that of corannulene (9.2 kcal/mol) because of peri-annelation of the corannulene skeleton. The calculations of the barriers of the neutral radical (12.6 kcal/mol), radical dianion (8.1 kcal/mol), and trianion (5.4 kcal/mol) of the phenalenyl-fused corannulene have exhibited a stepwise flattening of the curvature with increase in negative charge. Therefore, we have revealed that the bowl-inversion barrier of the anion is governed by the setoff of the peri-annelation and negative charge effects.

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Reduction of Carbon‐rich Compounds

Cited by 9 publications

References 95 publications

Tuning Magnetic Interactions Between Triphenylene Radicals by Variation of Crystal Packing in Structures with Alkali Metal Counterions

Tuning Magnetic Interactions Between Triphenylene Radicals by Variation of Crystal Packing in Structures with Alkali Metal Counterions

A Biradical Balancing Act: Redox Amphoterism in a Diindenoanthracene Derivative Results from Quinoidal Acceptor and Aromatic Donor Motifs

Curve-Structured Phenalenyl Chemistry: Synthesis, Electronic Structure, and Bowl-Inversion Barrier of a Phenalenyl-Fused Corannulene Anion

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