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.

scholarly journals Charge-transfer complexes of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with amino molecules in polar solvents

2015 ◽  
Vol 149 ◽  
pp. 75-82 ◽  
Author(s):  
Silvia Berto ◽  
Enrico Chiavazza ◽  
Valentina Ribotta ◽  
Pier Giuseppe Daniele ◽  
Claudia Barolo ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Charge Transfer Complexes ◽  
Polar Solvents

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.

Sign in / Sign up

Export Citation Format

Share Document