Structures of tetracyanoethylene and its tricyanovinyl derivatives with intramolecular charge transfer: A review

Chetkina, L. A.; Bel’skii, V. K.

doi:10.1134/1.1496057

Cited by 9 publications

(6 citation statements)

References 76 publications

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“…[1][2][3][4] Crystalline tetracyanoethylene (TCNE, C 6 N 4 ) possesses rich solid state behavior, exhibiting many polymorphs. Being the strongest p-acid, 5 it also acts as a unique electron acceptor in many key charge-transfer complexes. As a result of TCNE's singular properties, it has been extensively investigated from both basic and applications stand points, e.g.…”

Section: Introductionmentioning

confidence: 99%

Phase transition between cubic and monoclinic polymorphs of the tetracyanoethylene crystal: the role of temperature and kinetics

Schatschneider

Liang²,

Jezowski

et al. 2012

CrystEngComm

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Prediction of the relative stabilities and phase transition behavior of molecular crystalline polymorphs is highly coveted as distinct phases can possess different physical and chemical properties while having similar energies. Crystalline tetracyanoethylene (TCNE, C 6 N 4 ) is known to exhibit rich solid state phase behavior under different thermodynamic conditions, as demonstrated by a wealth of experimental studies on this system. Despite this fact, the role of temperature and kinetics on the phase diagram of TCNE remains poorly understood. Here, first-principles calculations and highresolution Fourier-transformed infrared (HR-FTIR) spectroscopy experiments are used to study the relative stabilities of the cubic and monoclinic phases of TCNE as a function of temperature. Specifically, density-functional theory with the van der Waals interactions method of Tkatchenko and Scheffler (DFT+vdW) is employed. The accuracy of this approach is demonstrated by the excellent agreement between the calculated and experimental structures. We find that the cubic phase is the most stable polymorph at 0 K, but becomes less favorable than the monoclinic phase at 160 K. This temperature-induced phase transition is explained on the basis of varying close contacts and vibrational entropies as a function of temperature. These findings are supported by a temperaturedependent HR-FTIR linewidth study of the CMN vibrons.

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Section: Introductionmentioning

confidence: 99%

Phase transition between cubic and monoclinic polymorphs of the tetracyanoethylene crystal: the role of temperature and kinetics

Schatschneider

Liang²,

Jezowski

et al. 2012

CrystEngComm

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“…Owing to its high electron affinity, this molecule forms many charge transfer complexes with a variety of electron donors. These charge transfer complexes are reported to exhibit exotic electrical, magnetic and other physico-chemical properties [1,2]. Recently an interesting TCNE-based compound has been synthesized [3] wherein the magnetization states can be switched using visible light of different wavelengths.…”

Section: Introductionmentioning

confidence: 99%

Pressure-induced transitions in tetracyanoethylene: a Raman scattering study

Rao

Sakuntala

Deb

et al. 2005

J. Phys.: Condens. Matter

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We report the results of high-pressure Raman scattering studies of the cubic and monoclinic polymorphs of tetracyanoethylene (TCNE). The evolution of the Raman spectrum at high pressures suggests that the cubic form is stable up to about 8 GPa. Subsequent pressurization leads to a gradual loss of transparency, and the sample becomes opaque to visible light above 14 GPa. In the monoclinic samples, qualitative changes are observed in the Raman spectrum above 3.6 GPa which indicate a subtle phase transition around this pressure. These changes are reversible when the pressure is reduced from peak values of about 4.5 GPa. At still higher pressures, the sample progressively becomes black, similar to what is observed in cubic TCNE. The Raman spectrum of the sample above 7 GPa is indicative of polymerization of TCNE. The spectrum of the pressure cycled opaque phase shows broad features characteristic of an amorphous phase, which is understood as being due to random cross-linking of TCNE in the pressure-reducing cycle.

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“…One hydrogen atom from a water molecule is disordered over two half-occupied positions, H 2b9 and H 2b99 . As already described for anionic p-benzoquinone salts 39,40 and in particular for lithium chloranilate salts, 41,42 the dianionic organic molecule consists of two resonance sub-systems with delocalized electrons separated by two C-C single bonds (Fig. 1).…”

Section: Resultsmentioning

confidence: 79%

The low/room-temperature forms of the lithiated salt of 3,6-dihydroxy-2,5-dimethoxy-p-benzoquinone: a combined experimental and dispersion-corrected density functional study

et al. 2013

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International audienceFollowing our first experimental and computational study of the room temperature (RT) form of the tetrahydrated 3,6-dihydroxy-2,5-dimethoxy-p-benzoquinone dilithium salt (Li2DHDMQ?4H2O), we have researched the occurrence of hydrogen ordering in a new polymorph at lower temperature. The study of polymorphism for the Li2DHDMQ?4H2O phase employs both experimental (single crystal X-ray diffraction) and theoretical approaches. While clues for disorder over one bridging water molecule were observed at RT (b form), a fully ordered model within a supercell has been evidenced at 100 K (a form) and is discussed in conjunction with the features characterizing the first polymorphic form reported previously. Density functional theory (DFT) calculations augmented with an empirical dispersion correction (DFT-D) were applied for the prediction of the structural and chemical bonding properties of the a and b polymorphs of Li2DHDMQ?4H2O. The relative stability of the two polymorphic systems is evidenced. An insight into the interplay of hydrogen bonding, electrostatic and van der Waals (vdW) interactions in affecting the properties of the two polymorphs is gained. This study also shows how information from DFT-D calculations can be used to augment the information from the experimental crystal diffraction data and can so play an active role in crystal structure determination, especially by increasing the reliability and accuracy of H-positioning. These more accurate hydrogen coordinates allowed for a quantification of H-bonding strength through a topological analysis of the electron density (atoms-in-molecules theory)

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Structures of tetracyanoethylene and its tricyanovinyl derivatives with intramolecular charge transfer: A review

Cited by 9 publications

References 76 publications

Phase transition between cubic and monoclinic polymorphs of the tetracyanoethylene crystal: the role of temperature and kinetics

Phase transition between cubic and monoclinic polymorphs of the tetracyanoethylene crystal: the role of temperature and kinetics

Pressure-induced transitions in tetracyanoethylene: a Raman scattering study

The low/room-temperature forms of the lithiated salt of 3,6-dihydroxy-2,5-dimethoxy-p-benzoquinone: a combined experimental and dispersion-corrected density functional study

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