Tetrathiafulvalene and 7,7,8,8,-tetracyano-p-quinodimethane in zeolite Y

Abstract

Tetrathiafulvalene (TTF) and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) are included in the pores of the zeolite Y framework structure (NaY), each species individually and both together as charge-transfer complexes by absorption from the liquid phase. The positions of these guest molecules are determined by powder diffraction, difference Fourier methods and subsequent structure refinement. The TCNQ is located in the centre of the 12-ring windows of NaY, while TTF is adsorbed in front of the 6-ring windows in the supercage. Identical positions are found for the guest molecules when both molecules are adsorbed. The effect of coordination on the guest within the zeolite was studied by UV–VIS and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopies. DRIFT measurements show a shift of the CN-valence vibration absorption band of TCNQ in NaY to higher wavenumbers due to a change in the triple bond character. UV–VIS spectra display a bathochromic shift (to lower wavelength) of the absorption bands of TTF after incorporation. On the other hand the shift of the charge transfer band is hypsochromic.