scholarly journals Charge transfer tuning by chemical substitution and uniaxial pressure in the organic complex tetramethoxypyrene–tetracyanoquinodimethane

2015 ◽  
Vol 17 (6) ◽  
pp. 4118-4126 ◽  
Author(s):  
Milan Rudloff ◽  
Kai Ackermann ◽  
Michael Huth ◽  
Harald O. Jeschke ◽  
Milan Tomic ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Electron Affinity ◽  
Uniaxial Pressure ◽  
Organic Complex ◽  
Chemical Substitution

Charge transfer is not enhanced by the larger electron affinity of the acceptor as evident from a comparison of the mixed-stack systems TMP–TCNQ and TMP–F4TCNQ.

Introduction

2003 ◽  
Author(s):  
Toshiaki Enoki ◽  
Morinobu Endo ◽  
Masatsugu Suzuki
Keyword(s):  
Electronic Structure ◽  
Charge Transfer ◽  
Ionization Potential ◽  
Molecular Orbital ◽  
Electron Affinity ◽  
Basic Unit ◽  
Charge Transfer Complexes ◽  
Vacuum Level ◽  
2D System ◽  
Lowest Unoccupied Molecular Orbital

There are two important features in the structure and electronic properties of graphite: a two-dimensional (2D) layered structure and an amphoteric feature (Kelly, 1981). The basic unit of graphite, called graphene is an extreme state of condensed aromatic hydrocarbons with an infinite in-plane dimension, in which an infinite number of benzene hexagon rings are condensed to form a rigid planar sheet, as shown in Figure 1.1. In a graphene sheet, π-electrons form a 2D extended electronic structure. The top of the HOMO (highest occupied molecular orbital) level featured by the bonding π-band touches the bottom of the LUMO (lowest unoccupied molecular orbital) level featured by the π*-antibonding band at the Fermi energy EF, the zero-gap semiconductor state being stabilized as shown in Figure 1.2a. The AB stacking of graphene sheets gives graphite, as shown in Figure 1.3, in which the weak inter-sheet interaction modifies the electronic structure into a semimetallic one having a quasi-2D nature, as shown in Figure 1.2b. Graphite thus features a 2D system from both structural and electronic aspects. The amphoteric feature is characterized by the fact that graphite works not only as an oxidizer but also as a reducer in chemical reactions. This characteristic stems from the zero-gap-semiconductor-type or semimetallic electronic structure, in which the ionization potential and the electron affinity have the same value of 4.6 eV (Kelly, 1981). Here, the ionization potential is defined as the energy required when we take one electron from the top of the bonding π-band to the vacuum level, while the electron affinity is defined as the energy produced by taking an electron from the vacuum level to the bottom of the anti-bonding π*-band. The amphoteric character gives graphite (or graphene) a unique property in the charge transfer reaction with a variety of materials: namely, not only an electron donor but also an electron acceptor gives charge transfer complexes with graphite, as shown in the following reactions: . . .xC + D → D+ C+x. . . . . .(1.1). . . . . .xC + A → C+x A−. . . . . .(1.2). . . where C, D, and A are graphite, donor, and acceptor, respectively.

scholarly journals 9-(Dicyanomethylidene)fluorene–tetrathiafulvalene (1/1)

2012 ◽  
Vol 68 (4) ◽  
pp. o932-o932 ◽  
Author(s):  
Amparo Salmerón-Valverde ◽  
Sylvain Bernès
Keyword(s):  
Crystal Structure ◽  
Charge Transfer ◽  
Title Compound ◽  
Ring System ◽  
Stacking Interactions ◽  
Inversion Center ◽  
Organic Complex ◽  
Compound C ◽  
Fluorene Derivative ◽  
The Mean

The title compound, C16H8N2·C6H4S4, crystallizes with the fluorene derivative placed in a general position and two half tetrathiafulvalene (TTF) molecules, each completed to a whole molecule through an inversion center. The fluorene ring system is virtually planar (r.m.s. deviation from the mean plane = 0.027 Å) and the dicyano group is twisted from the fluorene plane by only 3.85 (12)°. The TTF molecules are also planar, and their central C=C bond lengths [1.351 (8) and 1.324 (7) Å] compare well with the same bond length in neutral TTF (ca1.35 Å). These features indicate that no charge transfer occurs between molecules in the crystal; the compound should thus be considered a cocrystal rather than an organic complex. This is confirmed by the crystal structure, in which no significant stacking interactions are observed between molecules.

Synthesis, molecular and electron transport properties of 2-alkyltrinitrofluoren-9-ones

1985 ◽  
Vol 63 (1) ◽  
pp. 147-152 ◽  
Author(s):  
Beng S. Ong ◽  
Barkev Keoshkerian ◽  
Trevor I. Martin ◽  
Gordon K. Hamer
Keyword(s):  
Charge Transfer ◽  
Electron Transport ◽  
Transport Properties ◽  
Electron Affinity ◽  
Electron Donors ◽  
The Other ◽  
Bulky Substituent ◽  
Other Hand ◽  
Electron Transport Properties ◽  
Polymer Compatibility

2-Alkyltrinitrofluoren-9-ones 2 were conveniently synthesized by controlled nitration of 2-alkylfluoren-9-ones 5 with a mixture of red fuming HNO3 and concentrated H2SO4 at 0–25 °C. The precursors 5 were derived from the corresponding 2-acylfluorenes by appropriate reduction of the acyl function, followed by base-catalysed O2-oxidation at the C-9 position. The regiochemistry of nitration was interesting: with a sterically bulky substituent in 5, nitration occurred at C-4, -5, and -7 positions, affording 2-alkyl-4,5,7-trinitrofluoren-9-one in over 35% yield; on the other hand, 5 with a primary alkyl function underwent nitration predominantly at C-3, -5, and -7 positions. By virtue of its alkyl function, 2-alkyltrinitrofluoren-9-one 2 displayed better solubility and polymer compatibility characteristics than its non-alkylated analog, TNF. However, the charge transfer interactions of 2 with electron donors were weaker than those of TNF, despite the fact that they both have the same electron affinity. Both 2 and TNF exhibited good electron transport properties in poly(N-vinylcarbazole) matrices.

Charge-transfer Complexes with Nitrate Esters as Electron Acceptors

1972 ◽  
Vol 50 (20) ◽  
pp. 3340-3349 ◽  
Author(s):  
T. Urbański ◽  
B. Hetnarski ◽  
W. Południkiewicz
Keyword(s):  
Charge Transfer ◽  
Electron Affinity ◽  
Electron Acceptors ◽  
Stable Complex ◽  
Charge Transfer Complexes ◽  
Polar Solvents ◽  
Nitrate Esters ◽  
High Enthalpy ◽  
Unstable Complex

Nitrate esters of alcohols, containing from one to six O-nitro groups, react with tetramethyl-p-phenylenediamine (TMPD) in non-polar solvents to yield Wurster cation. The number of O-nitro groups necessary to produce 1 mol of Wurster cation is at least three. This is now explained in terms of the enthalpy of the reaction related to the electron affinity of nitrate esters; esters with five to six O-nitro groups show a relatively high enthalpy manifested by their ability to form charge-transfer complexes. Initially an unstable complex A is formed which then gives Wurster cation, both reactions being fast. A slow transformation then occurs into more stable complex B having the composition: 1 mol TMPD–2 mol of pentanitrates or 1 mol TMPD–1 mol of hexanitrate. TMPD in complex B was transformed into tetramethyl-p-quinonediimine dication.That all nitrate esters with one to four O-nitro groups do not form complexes A and B may be due either to their relatively low enthalpy (and electron affinity), or to more favorable structures of complexes A and B of pentanitrates of D-xylitol and penta- and hexanitrates of hexitols with TMPD.

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