Dimerization of 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical anions via σ-bond formation: crystal structure and EPR properties of bis(dipyridyl)platinum(II)–TCNQ, [Pt(2,2'-dipy)₂ ²⁺(TCNQ)₂ ²⁻]

Abstract

The title compound, obtained by the reaction of Pt(2,2'-dipy)zCl 2 with LiTCNQ, crystallizes in the triclinic space group PI with a = 7.891 (7), b --14.247 (2), c = 12.253 (2) A, (l = 130.01 (5), fl = 120.06 (6), ~, = 61.96 (6) °, Z = 1. The structure was solved by Fourier methods and refined by least-squares to R = 0.059, based on 4122 observed reflexions. The structure consists of [Pt(2,2'-dipy)z] 2+ cations and (TCNQ)~-anions. In the anions the unpaired electrons of two TCNQ-radicals form a o-bond of 1.65 A between two methylene C atoms, giving a diamagnetic but easily excitable ground state. A phase transition to a paramagnetic modification is observed at 87 °C.

The Early Years of 2,2′-Bipyridine—A Ligand in Its Own Lifetime

“…In some cases, the electronic demands of the bpy ligand to maximize conjugation in a planar conformation dominates and the geometry of the PtN 4 motif in the [Pt(bpy) 2 ] 2+ cation is distorted towards tetrahedral, with least squares planes angles between the near-planar bpy ligands between 30 and 37° (Figure 19a) [171,172,173]. In other cases, the electronic preference of the d 8 metal centre for a square-planar PtN 4 motif dominates, and the bpy adopts a V-shaped conformation about the interannular C–C bond (Figure 19b) [174,175,176,177,178,179]. Only in the compound [Pt(bpy) 2 ](ClO 4 ) 2 have both the square-planar and tetrahedral PtN 4 coordination geometries been structurally characterized.…”

“…The [Pt(bpy) 2 ] 2+ is distorted from the idealized square-planar geometry with the bpy ligands lying in the square-plane because of unfavourable steric interactions between H6 protons of the bpy ligands. The complexes are either distorted to ( a ) tetrahedral arrangement of the nitrogen donors about the platinum or ( b ) the ligands are riffled about a square-planar metal centre [179]. …”

Soft porous crystal meets TCNQ: charge transfer-type porous coordination polymers

“…In addition, TCNQ sometimes shows the formation of multimeric complexes which expands the structural diversity of the coordination frameworks, and especially, dimerization of the TCNQ radicals with s bonds leads to the enormous changes of the molecular structure and electronic state. 52 The s bonded dimer (TCNQ-TCNQ) is formed by the linking of two TCNQ radical anions and a divalent anion. The p-conjugated structure of whole TCNQ molecule is ruptured by the sp 3 type bond formation and the negative charges localize in each TCNQ moiety.…”

The crystal structure of the charge-transfer complex between N-ethylphenazinium (EtP) and dimerized 7,7,8,8-tetracyanoquinodimethanide (TCNQ) ions, (C14H13N2)2.C24H8N8

“…These dimerized ions, TCNQ22-, contain a long o bond with a C-C distance of 1.631 A. While preparing this manuscript we learned of another structure determination in which such a dimer was found (Dong, Endres, Keller, Moroni & N6the, 1977).…”