Journal of Fluorine Chemistry 101 (2000) 161±163
Rapid synthesis of hybrid ¯uorides by microwave heating
Son Phan Thanh, Fabrice Gaslain, Marc Leblanc, Vincent Maisonneuve*
Faculte des Sciences, Laboratoire des Fluorures, UPRES-A 6010, Universite du Maine,
Avenue Olivier-Messiaen, 72085 Le Mans, Cedex 9, France
Received 9 May 1999; accepted 6 July 1999
Abstract
Two new series of organic±inorganic ¯uorides are synthesized by microwave heating. These compounds constitute probably the ®rst new
materials obtained by this way. The conditions of synthesis and several structural features of these hybrid materials together with the
structure of the ®rst member of the series, [H3N(CH2)6NH3]AlF5, are reported. It crystallizes in the monoclinic system, space group P21,
Ê , b ˆ 5.507(1) A
Ê , c ˆ 12.658(2) A
Ê , ˆ 103.67(1)8, V ˆ 535(2) A
Ê 3, and Z ˆ 2. Its structure
with the lattice parameters a ˆ 7.894(2) A
consists of vertex-sharing in®nite chains of AlF6 octahedra connected by diprotonated 1.6 diamines. # 2000 Elsevier Science S.A. All
rights reserved.
Keywords: Microwave synthesis; Hybrid ¯uorides; Structural features
1. Introduction
2. Experimental
Microwave heating was ®rst used for digestion or drying
of solid materials. Recently, this technique has been
extended to the sintering of ceramics and the promotion
of organic or inorganic reactions [1]. Most of the experiments were done to reproduce the synthesis of known
compounds, often molecular sieves. Microwave heating
allows a shorter time of reaction as compared with the
conventional hydrothermal method; the heat transfer, due
to microwave absorption, is limited to the solvent and to the
starting materials in contrast with the classic method, where
heat is transferred from outside to inside. Obviously, this
advantage is very convenient for production cost lowering. It
seems also possible to get large crystals [2] or the inclusion
of chromophores in zeolites [3]. In addition, the crystallinity
and the morphology of some materials can be controlled [4].
The following list gathers the majority of these compounds
prepared by microwave heating (Hybrid compounds (zeolites): APO-5, APO-11, OMS-1, ZSM-5, VPI-5, cloverite
and mineral materials: BaTiO3, PbTiO3, Na5B2P3O13, apatite). Up to now, no work has been devoted to the synthesis of
new inorganic or hybrid inorganic±organic materials.
In this article, we present the preliminary studies of two
new series of hybrid compounds prepared by the microwave
route.
The synthesis of hybrid ¯uorides was achieved with a
microwave digestion system (MDS-2100, CEM Corporation). This microwave delivers approximately 950 W of
microwave energy at a frequency of 2450 MHz at full power.
The power may be programmed in percent increments to
control the heating rate. The internal pressure or temperature, sensed respectively by a transducer and a ®ber optic
probe with a phosphor sensor, can be regulated by monitoring the power. Microwave sample preparation requires to
respect a set of safety considerations.
The samples were obtained from a stirred mixture of
M2O3 (M ˆ Al, Ga) or MCl3 (M ˆ Cr, Fe, V) Ð 1.6, 1.8,
1.9, 1.10, 1.12 diaminohexane/octane/nonane/decane/dodecane Ð HF and ethanol. H3PO4 was added for the ®rst series
of compounds. The mixtures were loaded in polytetra¯uoroethylene (PTFE) autoclaves and heated for 2 h at 1908C.
The resulting materials were ®ltered, washed with ethanol
and dried in air.
*
Corresponding author.
E-mail address: [email protected] (V. Maisonneuve)
3. Results and discussion
The ®rst series (noted A) of hybrid compounds obtained
with 1.6, 1.9, 1.10 and 1.12 alkyldiamines appeared as
colorless transparent needles. Chemical analysis on several
crystals of 1.6 compound by an energy-dispersive-spectroscopy-equipped scanning electron microscope indicates an
0022-1139/00/$ ± see front matter # 2000 Elsevier Science S.A. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ( 9 9 ) 0 0 1 5 3 - 0
162
S.P. Thanh et al. / Journal of Fluorine Chemistry 101 (2000) 161±163
Fig. 1. XRD diffractograms of fluoroaluminophosphates (a) and fluoroaluminates (b) templated by the 1.6, 1.8, 1.9, 1.10, 1.12-diaminohexane/octane/
nonane/decane/dodecane. The position of the first intense peak is related to the number of carbon atoms of aliphatic diamines.
inorganic formulation close to Al(PO4)F4. Two diprotonated
1.6 diaminohexane cations must be necessary to balance the
four negative charges of the inorganic part; i.e., global
formulation is close to [N2CnH2n‡6]2Al(PO4)F4. The Xray powder (XRD) diffractograms of this new series of
¯uoroaluminophosphates templated with aliphatic diamines
are presented in Fig. 1 (left). Each pattern shows a ®rst
intense peak at low angle followed by weaker re¯ections.
The position of the ®rst peaks moves simultaneously to the
low angle with the increasing of the length of carboned
chain of the diamine. The series of materials (noted A),
prepared by classical hydrothermal experiments with the
same starting materials, except the solvent constituted by a
mixture of water and ethanol (60/40), gave similar XRD
diffractograms and an analogous evolution of the ®rst peak
[5]. However, the positions of these ®rst peaks differ. For the
1.6 diamine compounds, the dhkl value decreases from
Ê for A series to 11.73 A
Ê for A series. Consequently,
13.52 A
the structures are probably slightly different. The structure
with 1.6 diaminohexane (ULM-13) is known [6]. It is
built up from inorganic sheets formulated [Al4(PO4)3(HPO4)F6]5ÿ separated by organic layers consisting of
1.6 diammonium cations and water molecules. One of
the amines connects the inorganic layers and is oriented
perpendicularly to the layers. A linear relationship has been
established between the length of the chain of the diamine
and the interlayer distances, indicating that the organic
molecules are always perpendicular to the organic sheets
in this ULM-13 series. The structure of 1.6 hybrid compound prepared by microwave synthesis is currently investigated to shed light on the structural differences and the
in¯uence of the synthesis with a binary solvent.
The second series (noted B) of hybrid compounds using
1.6, 1.8, 1.10 and 1.12 alkyldiamines, prepared without
H3PO4, present a lamellar morphology. A very small single
crystal was isolated in the sample with the 1.6 diamine.
Crystal data were collected on a STOE AED2 4-circle
diffractometer. The structural determination [7] has
revealed a [H3N(CH2)6NH3]AlF5 formulation and a monoclinic symmetry (P21). The structure consists of in®nite
chains of vertex-sharing AlF6 octahedra (Fig. 2, left). These
octahedra are cis-connected along b-axis. The inorganic
chains are linked each other by two crystallographically
inequivalent amines (Fig. 2, right). The charge balance is
achieved by diprotonation of 1.6 diamine. The cohesion
between the inorganic and organic parts is ensured by a set
of hydrogen bonds. The syntheses using diamines with
longer alkyl chains (CnH2n‡4N2 with n ˆ 8, 10, 12) give
Fig. 2. Projections of [H3N(CH2)6NH3]AlF5 structure in a±b (a) and a±c (b) planes.
S.P. Thanh et al. / Journal of Fluorine Chemistry 101 (2000) 161±163
163
Table 1
Cell parameters of the A series of hybrid materials [D]MF5
[1.6 diamine]AlF5
[1.8 diamine]AlF5
[1.10 diamine]AlF5
[1.12 diamine]AlF5
[1.6 diamine]FeF5
[1.6 diamine]CrlF5
[1.6 diamine]VF5
[1.6 diamine]GaF5
Ê)
a (A
Ê)
b (A
Ê)
c (A
(8)
Ê 3)
V (A
7.894(2)
7.897(7)
7.897(2)
7.871(2)
8.030(2)
7.969(2)
7.991(2)
7.994(3)
5.507(1)
5.496(2)
5.474(2)
5.476(2)
5.800(1)
5.692(1)
5.794(1)
5.707(1)
12.658(2)
14.770(4)
17.118(9)
19.366(4)
12.537(3)
12.493(3)
12.503(3)
12.602(4)
103.67(1)
97.71(2)
92.80(2)
90.20(4)
103.50(2)
104.04(2)
103.87(2)
103.65(2)
535(2)
635(3)
739(2)
835(1)
567(3)
549(3)
562(4)
559(3)
powdered products. The XRD patterns of B series show a
same aspect and an evolution similar to that of the A series
(Fig. 1, right). The re®ned cell parameters of iso-structural
[D]AlF5 (D ˆ 1.8, 1.10, 1.12 alkyldiammonium) are
reported in Table 1. The evolution of cell volumes is linear
with the number of carbon atoms of alkyled chain. Moreover, the substitution of aluminum by other metallic cations
using 1.6 diamine demonstrates the capacity of the structure
to accommodate different metal sizes. Owing to the very
similar XRD patterns, the structure of the metal-substituted
compounds must be isotype to the structure of [1.6 hexanediammonium]AlF5. The evolution of the cell parameters shows that the structure adapts mainly the metal
size by increasing the b parameter (Table 1). The expansion
of the MF6 octahedron size induces the elongation of the
in®nite chains.
These two new series of hybrid ¯uorides prove clearly the
advantages of microwave heating: short time of crystallization, low temperature, and, addition, it seems possible to
synthesize original phases inaccessible by other routes.
Finally, this method, favored by the recent development
of microwave technique, is a powerful tool for the exploration of chemical diagrams.
Acknowledgements
The authors are grateful to Jean Renaudin for useful
discussions.
References
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