P-2.2-04
Structural characterization of fluorenone dye in zeolite L
L. Gigli1, G. Agostini2, R. Arletti3, E. Fois4, C. Lamberti2, G. Tabacchi4, S. Quartieri5, G. Vezzalini1
1 Chemical and Geological Sciences Department, UNIMORE, Largo S. Eufemia
19, 41121 Modena
Italy, lara.gigli@unimore.it.
2 Department of Inorganic, Physical, Materials Chemistry, NIS Center of
Excellence, and INSTM Unit, UNITO, Torino, Italy
3 Earth Sciences Department, UNITO, Torino, Italy 4 DSAT and INSTM, UNINSUBRIA, Como, Italy
5 Physics and Earth Sciences Department, UNIME, Messina, Italy
Keywords: Zeolite L, dye incorporation, in situ synchrotron XRPD, structure refinement.
Introduction
Zeolite L (ZL) [K8.46(Al8.35Si27.53)O72 •17.91H2O, framework type LTL, s.g. P6/mmm] is an
appealing and excellent host for the supramolecular organization of different kinds of molecules and complexes. The capacity of this zeolite, characterized by monodimensional 12-ring channels, to induce an ordered geometrical arrangement of dye molecules, is used for the design of antenna systems and charge-transfer complexes [1-3] Relatively few experimental structural
information is available about the orientation and alignment of the dye
molecules in the zeolite pores, hence a detailed structural characterization is of great importance for understanding the functionality of these host-guest
systems.
Experimental
In this study, the neutral dye fluorenone (C13H8O) (FL) was inserted from the gas phase
(sublimation temperature 130 °C) into ZL dehydrated at 200 °C for 12 h under vacuum (10-4 mbar), so to assure that water molecules did not block the
pathway for molecule entering [4]. Synchrotron X-ray powder diffraction experiment were performed at Gilda beamline (ESRF, Grenoble) on both dehydrated and FL-loaded zeolite L (FL-ZL). The diffraction data clearly evidenced the embedding of the dye into the channels, as well as the minor presence (6.9 %) of fluorenone molecules on the zeolite surface. As a
consequence, the structure of FL-ZL was determined by a two-phases Rietveld refinement in the hexagonal space group P6/mmm [5]. The background was empirically fitted using a Chebyschev polynomial with 15 variable coefficients and the peak profiles were modeled by a pseudo-Voight function.
Results and discussion
The incorporation of FL into the channels of dehydrated ZL was confirmed by a significant
change of the unit cell parameters (Table 1). 1.7 FL molecules per unit cell were located in the large
12-membered ring channel running parallel to c axis. The strong interaction between FL carbonyl
group and the extraframework potassium cation, predicted by theoretical modeling [6], is
experimentally confirmed by the short bond distances (2.77 Å)(Figure 1). Such an interaction explains why FL molecules are not displaced by water molecules when FL-ZL hybrid is re-exposed to the air [6].
Table 1 RIETVELD RESULTS ZL as synthetized Unit cell a= 18.3059(2) c=7.5116(1) V= 2177.08(6) Dehydrated ZL a= 18.3802(2) c=7.5017(1) V= 2194.81(4) Dehydrated ZL/FL a= 18.3416(2) c=7.5164(1) V=2189.89(7)
Figure 1 Projection along c axis of the hybrid-FL-ZL structure. Dark grey: K sites; light grey: C sites; black: FL carbonyl oxygen atoms.
Conclusions
The structural refinement of FL-ZL hybrid allowed to localize 1.7 FL molecules in the 12-ring
channels. The strong interaction of FL carbonyl oxygen with K atoms is in line with the stability of
this material under ambient conditions. References
[1] G. Calzaferri (2012) Langmuir, 28, 6216-6231.
[2] C. Botta, S. Destri , M. Pasini, P. Picouet , G. Bongiovanni, A. Mura , M. Uslenghi, G. Di Silvestro , R. Tubino.
(2003) Synthetic Metals 139, 791–794.
[3] N. Gfeller, S. Megelski, G. Calzaferri. (1999) J. Phys. Chem. B, 103, 1250-1257. [4] A. Devaux, C. Minkowski, G. Calzaferri (2004) Chem. Eur. J. 10, 2391- 2408.
[5] R. M. Barrj, R and H. Villigj (1969) Zeitschrift fur Kristallographie, Bd. 128, S. 352-370 [6] E. Fois, G. Tabacchi, G. Calzaferri. 2010 J. Phys. Chem. C, 114, 10572–10579
