Free Access
Microsc. Microanal. Microstruct.
Volume 6, Number 5-6, October / December 1995
Page(s) 545 - 550
Microsc. Microanal. Microstruct. 6, 545-550 (1995)
DOI: 10.1051/mmm:1995146

Polymorphism in the $\bf [(TTF)_2(TCNE)_2]$ Charge-Transfer Complex

Antonella Ciccarese1, Dore Augusto Clemente2, Armando Marzotto3 et Cesare Pecile4

1  Dipartimento di Biologia, Università di Lecce, Via Monteroni, 73100 Lecce, Italy
2  Dipartimento di Ingegneria dei Materiali e Chimica Applicata, Università di Trieste, Via Valerio 2, 34127 Trieste, Italy
3  Dipartimento di Chimica Inorganica, Metallorganica ed Analitica, Università di Padova, Via Loredan 4, 35131 Padova, Italy
4  Dipartimento di Chimica Fisica, Università di Padova, Via Loredan 2, 35131 Padova, Italy

The reaction between tetrathiafulvalene (TTF) and tetracyanoethylene (TCNE) yields two polymorphs ($\alpha$ and $ \beta$) both having formula $\rm [(TTF)_2^{2\delta +}(TCNE)_2^{2\delta -}]$ with similar molecular structure. Both polymorphs display a stack structure of the type $\cdots$(TTF-TTF)(TCNE-TCNE)(TTF-TTF) (TCNE-TCNE)$\cdots$ but they differ in crystal structure for hydrogen bonding system and lamellar sheets. These two CT complexes possess an high resistivity ( $\cong 10^9~\Omega$.cm) and a degree of charge-transfer of $\delta =0.54e$ estimated through the C-S bond length.

6150K - Crystallographic aspects of polymorphic and order disorder transformations.
7215N - Collective modes: low dimensional conductors.
6165 - Crystal structure of specific organic compounds.
6150L - Crystal binding.

Key words
charge exchange -- crystal structure -- electrical resistivity -- hydrogen bonds -- organic compounds -- polymorphism -- synthetic metals -- TTF sub 2 TCNE sub 2 -- charge transfer complex -- polymorphism -- tetrathiafulvalene -- tetracyanoethylene -- molecular structure -- stack structure -- crystal structure -- hydrogen bonding -- lamellar sheets -- resistivity -- C S bond length -- 1E9 ohmcm

© EDP Sciences 1995