Tetracyanoethylene (TCNE): The Characteristic Geometries and Vibrational Absorptions of Its Numerous Structures

Abstract

Tetracyanoethylene (TCNE) undergoes numerous reactions and is reported to exist in many structural motifs. Identification of these forms and motifs can be challenging. Nonetheless, the number of nu(CN) absorptions and their frequencies provide insight with respect to the specific forms and charge on the TCNE fragment. Particularly informative is the average of the fundamental nu(CN) bands, as well as the length of the central C-C bond. This Review discusses the assignment of structure and formal charge for TCNE-containing compounds. Scrutiny of previous assignments reveals some discrepancies which are discussed, and provides a basis for further study of TCNE structure-function relationships. Several multimetal complexes with bridging [TCNE](z) units exhibit mixed valency and extensive delocalization. The scarcity of suitable model compounds, especially those with M(d(pi-pi*)) backbonding to the CN groups, have thwarted the detailed description of these valence ambiguous compounds; thus, new well-characterized polynuclear compounds are needed.

Unusually Long, Multicenter, Cationδ+⋅⋅⋅Anionδ−Bonding Observed for Several Polymorphs of [TTF][TCNE]

“…According to the AIM methodology, an intermolecular bond presents a (3,À1) bcp in the electronic density of the complex. This bcp connects two bonded atoms, and can be characterized by the electron density (1) and Laplacian (5 2 , the sum of the curvatures of the density at the bcp, obtained by adding the eigenvalues of the second derivative of the density at the bcp). In all known hydrogen bonds and van der Waals bonds the 1 at the bcp is very small, and the 5 2 is positive.…”

MnII(TCNE)3/2(I3)1/2–A 3D Network‐Structured Organic‐Based Magnet and Comparison to a 2D Analog

“…[11,14] High resolution powder X-ray diffraction [15] (Fig. S1a) À that comprise the sheets, nMnNC is 156.5(6)8.…”

Density functional study of the magnetic coupling inV(TCNE)2

“…These constraints include ͑i͒ the observed stoichiometry V͑TCNE͒ 2 , 3,8,10 ͑ii͒ the suggested octahedral coordination for the metal ion, 14 ͑iii͒ the presence of uncoordinated cyano groups, 7,10,31 and ͑iv͒ the dimensionality of the material forming a periodic crystalline network of V atoms and TCNE molecules. The resulting structure consists of a rectangular planar array of V atoms and TCNE molecules which form bidimensional planes linked through parallel chains of trans--bonded TCNEs.…”