Effect of the synthesis temperature on the dimensionality of hybrid fluorozincates

Article abstract of DOI:10.1016/j.jfluchem.2016.07.003

A series of new hybrid fluorozincates incorporating 5-aminotetrazole (Hamtetraz) is obtained from a same starting mixture of ZnF₂, HF solution and Hamtetraz in acetronitrile at different synthesis temperatures. The structures, determined by single crystal X-ray diffraction, exhibit various networks with dimensionalities that increase as a function of the synthesis temperature. At 120?°C, two phases, ZnF₂(H₂O)(Hamtetraz) (1) and ZnF₂(Hamtetraz)₂(2), coexist and display 1D infinite chains._∞[ZnN₂F₂O] chains are built up from ZnN₂F₃(H₂O) octahedra linked by opposite fluorine corners in 1, while_∞[ZnN₂F₂] chains of edge sharing ZnN₂F₄octahedra are found in 2. At 130?°C, dense layers appear in Zn₃F₅(H₂O)₂(amtetraz) (3); they result from the condensation of_∞[ZnF₃N₂] and_∞[ZnF₂NO] chains by fluorine corners to form a neutral 2D network. At 140?°C, [NH₄]·(Zn₄F₅(amtetraz)₄)·3H₂O (4) presents an anionic 3D network containing small cavities in which water molecules and ammonium cations are inserted. The thermal behavior of the coordination polymers 3 and 4 is studied by TGA analysis and X-ray thermodiffraction; an intermediate phase is observed during the decomposition of 4.

Full text of DOI:10.1016/j.jfluchem.2016.07.003

Journal of Fluorine Chemistry 188 (2016) 164–170
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Effect of the synthesis temperature on the dimensionality of hybrid
fluorozincates
Vanessa Pimenta, Quang Hoang Hanh Le, Annie Hemon-Ribaud, Marc Leblanc,
*
Vincent Maisonneuve, Jérôme Lhoste
LUNAM Université, Université du Maine, CNRS UMR 6283, Institut des Molécules et Matériaux du Mans (IMMM), Avenue Olivier Messiaen, 72085 Le Mans
Cedex 9, France
A R T I C L E I N F O
A B S T R A C T
Article history:
A series of new hybrid fluorozincates incorporating 5-aminotetrazole (Hamtetraz) is obtained from a
same starting mixture of ZnF2, HF solution and Hamtetraz in acetronitrile at different synthesis
temperatures. The structures, determined by single crystal X-ray diffraction, exhibit various networks
with dimensionalities that increase as a function of the synthesis temperature. At 120 ꢀC, two phases,
ZnF2(H2O)(Hamtetraz) (1) and ZnF2(Hamtetraz)2 (2), coexist and display 1D infinite chains. 1[ZnN2F2O]
chains are built up from ZnN2F3(H2O) octahedra linked by opposite fluorine corners in 1, while 1[ZnN2F2]
chains of edge sharing ZnN2F4 octahedra are found in 2. At 130 ꢀC, dense layers appear in
Zn3F5(H2O)2(amtetraz) (3); they result from the condensation of 1[ZnF3N2] and 1[ZnF2NO] chains by
Received 26 May 2016
Received in revised form 4 July 2016
Accepted 7 July 2016
Available online 11 July 2016
Keywords:
Hybrid fluoride
Tetrazole
MOF
fluorine corners to form a neutral 2D network. At 140 ꢀC, [NH4]
ꢁ
(Zn4F5(amtetraz)4) 3H2O (4) presents an
ꢁ
Solvothermal synthesis
Microwave heating
anionic 3D network containing small cavities in which water molecules and ammonium cations are
inserted. The thermal behavior of the coordination polymers 3 and 4 is studied by TGA analysis and X-ray
thermodiffraction; an intermediate phase is observed during the decomposition of 4.
ã 2016 Elsevier B.V. All rights reserved.
1. Introduction
chemical nature of the precursors: organic linkers, metal cations or
counterions [11]. Depending on the transition metal ions and its
Hybrid inorganic–organic porous materials, also called porous
coordinationpolymers (PCPs) or metal-organic frameworks (MOFs),
represent a new generation of crystalline multifunctional porous
materials with potential applications in numerous fields, such as
energy or health [1,2]. The PCPs, considered as supramolecular
compounds with zeolite-like architectures, are built up from
inorganic units and organic linkers that lead eventually to 3D
frameworks with large cavities giving high surface area. Conse-
quently, these porous materials can show exceptional catalytic and
gas storage properties [3,4]. The first explored properties of MOFs
were focused on adsorption of H2 or CH4 which could be used as
future energy sources [5,6]. Nonetheless, CO2 capture [7] and gas
separation [8] are also seen as promising applications. The
adsorption properties of these architectures are strongly influenced
by numerous parameters such as the size and the topology of the
organic linkers [9] or the presence of unsaturated metal sites known
to be a key factor in gas adsorption [10]. To tune the network’s
topology, the most common approach consists to modify the
oxidation states, numerous coordination numbers from 2 to 7 give
multiple geometries leading to original network topologies. The
coordination numbers and the orientation of linker binding sites can
also modify the network topologies and influence the size and shape
of pores. The influence of metal cations and linkers has been largely
demonstrated for MOFs containing carboxylate ligands [12]. As
examples, MIL-53 [13] and MOF-5 [14] are prepared with
benzenedicarboxylateligandsandCr3+ andZn2+ cationsrespectively.
Ouellette et al. reported six new structures in the Cd(II)-1,2,4-
triazolate system by changing the counterion nature only (Fꢂ, Clꢂ,
2ꢂ
Brꢂ, Iꢂ, SO4 and NO3ꢂ) [15]. It must be noted that the metal
complexes with azoles as organic ligands are called Metal Azolate
Frameworks (MAFs).
In the present work, we focus on the synthesis of hybrid
fluorides with Zn2+ cation and aminotetrazole (Hamtetraz) as
linker. The deprotonated form of aminotetrazole (amtetraz)ꢂ, that
presents an aromatic cycle with four nitrogen donor atoms to form
NꢂꢂM bonds, is preferred in order to promote high network
dimensionality. The values of deprotonation acidic constants of
Hamtetraz/amtetrazꢂ couple (pKA = 4.6) and the HF/Fꢂ couple
(pKA = 3.2) are very close; this feature favours the crystallization of
fluorinated MAFs. Zn2+ cation is selected for its aptitude to accept
* Corresponding author.
E-mail address: jerome.lhoste@univ-lemans.fr (J. Lhoste).
http://dx.doi.org/10.1016/j.jfluchem.2016.07.003
0022-1139/ã 2016 Elsevier B.V. All rights reserved.

V. Pimenta et al. / Journal of Fluorine Chemistry 188 (2016) 164–170
165
different coordination geometries, from a tetrahedral environment
2. Results and discussion
to an octahedral geometry. Suh et al. have reported the synthesis of
Zn-based networks in which the Zn2+ coordination reversibly
changes from trigonal bipyramidal to tetrahedral geometry by a
desolvatation/solvation mechanism [16]. Therefore, it is expected
that the association of tetrazole cycles, fluoride ions and
unsaturated metal sites in porous materials will be propitious to
the gas uptake. While the literature is rich in terms of azole
compounds, the presence of fluoride counterions is sparse.
Thirteen metalate hybrids with fluorinated 2D or 3D networks
are reported to date; six phases integrate only Zn2+ cations [17–21]
2.1. Crystal structure description
Four new hybrid fluorozincates are obtained by solvothermal
synthesis at different temperature: ZnF2(H2O)(Hamtetraz) (1) and
ZnF2(Hamtetraz)2 (2) at 120 ꢀC, Zn3F5(H2O)2(amtetraz) (3) at 130 ꢀC
and [NH4]
ꢁ
(Zn4F5(amtetraz)4)
3H2O (4) at 140 ꢀC. The structures are
ꢁ
determined from single crystal X-ray diffraction data. Details of the
structure determinations are given in Table 1. Selected inter-
atomic distances of zincate and organic groups are gathered in
Table 2.
and seven others combine divalent cations (Fe2+, Zn2+, Ni2+
)
associated to trivalent cations (A = Al3+, Fe3+) [17,22,23–25]. Most of
the reported compounds are elaborated from 1,2,4-triazole or
derivatives and they are generally obtained by solvothermal
synthesis. While it is well known that the choice of the solvent or
the reaction temperature allows the control of the network
dimensionalities and topologies of metal carboxylates [26,27], the
effects of the synthesis parameters are rarely described for
fluorinated hybrids with nitrogen ligands. We have recently
evidenced 3D networks that are obtained in acidic conditions
and low azole concentrations [17,22,23]. Following an equivalent
synthesis strategy, this paper reports on four new compounds with
Hamtetraz and Zn2+ cations obtained by changing the synthesis
temperature only: ZnF2(H2O)(Hamtetraz) (1) and ZnF2(Hamtetraz)2
The structure of 1 is built up from neutral trans-chains
1[ZnF2N2O] oriented along the b axis (Fig. 1 left). These chains
contain ZnF3N2O octahedra connected by fluorine atoms F(2) and
by Hamtetraz in the N1,N2-bridging mode [17] (Scheme S1). The
presence of water molecule is confirmed by a long distance to Zn2+
(2.16 Å) compared to Zn-F(1) (2.10 Å). Fluoride ions, hydrogen
atoms of ꢂꢂNH2 of Hamtetraz and coordinated water molecules
ensure the stability of the structure (Fig. 1 right) via hydrogen
bonds (2.61–2.98 Å).
In 2, the condensation of (ZnF4N2) units by the connection of F–
F edges gives infinite 1[ZnF2(Hamtetraz)2] chains oriented along a
axis (Fig. 2 left). Nitrogen atoms of neutral tetrazole cycles, in N1-
bridging mode, occupy the axial positions of the octahedra.
Hydrogen bonds contribute to the stability of the structure with
NꢂꢂHꢁ ꢁ ꢁF(1) (2.58 and 2.89 Å) and NꢂꢂHꢁ ꢁ ꢁN (3.16 Å) intra- and
inter-chain interactions (Fig. 2 right).
(2) at 120 ꢀC, Zn3F5(H2O)2(amtetraz) (3) at 130 ꢀC and [NH4]
ꢁ
(Zn4F5(amtetraz)4)
ꢁ
3H2O (4) at 140 ꢀC. It is demonstrated that the
increase of the synthesis temperature results in increased network
dimensionality. We first describe the structures and the entities
condensation. Then, the thermal behavior of 3 and 4 is studied and
it is evidenced that 4 presents a crystalline intermediate with
possible unsaturated metal sites.
The crystal system of 3 is orthorhombic with Fmmm space
group. The architecture results from the stacking of (001) sheets
linked by interlayer bonds Ow–Hꢁ ꢁ ꢁOw (2.58 Å) along the c axis
(Fig. 3 left). The sheet can be described from inorganic 1D [100]
columns (Fig. 3 right) connected by deprotonated aminotetrazole
Table 1
Crystallographic data of ZnF2(H2O)(Hamtetraz) (1), ZnF2(Hamtetraz)2 (2), Zn3F5(H2O)2(amtetraz) (3) and [NH4]
ꢁ
(Zn4F5(amtetraz)4)
ꢁ3H2O (4) at room temperature.
Formula
1
2
3
4
ZnF2ON5CH5
ZnF2N10C2H6
Zn3F5O2N5CH6
Zn4F5O3N21C4H12
M
206.47
273.52
411.25
758.83
Crystal system
orthorhombic
2.331
P212121
6.2611(6)
6.9066(5)
13.6068(13)
–
monoclinic
2.222
P21/n
3.2988(1)
12.2103(4)
10.2295(3)
97.205(2)
408.8(1)
2
orthorhombic
3.098
Fmmm
3.9732(18)
17.551(7)
25.28(2)
–
monoclinic
2.260
P21/c
6.5873(1)
12.9396(3)
13.0141(3)
90.023(1)
1109.3(1)
2
rcalc (g cmꢂ3
Space group
a (Å)
)
b (Å)
c (Å)
b
(ꢀ)
V (Å3)
588.4(1)
4
4.152
1762.8(13)
8
8.175
Z
m
(Mo, K
a
) (mmꢂ1
)
3.026
4.374
F(000)
408
272
1552
730
No. of unique reflns
No. of obsd reflns [I > 2
Refined parameters
GOF
1712
1130
98
0.999
2476
2157
70
1.266
1171
956
53
1.257
2542
2469
162
1.250
s
(I)]
Final R indices [I > 2
s
(I)]
R1 = 0.0428
wR2 = 0.0771
R1 = 0.0738
wR2 = 0.0881
ꢂ0.496, 0.510
R1 = 0.0632
wR2 = 0.1737
R1 = 0.0685
wR2 = 0.1767
ꢂ1.025, 4.708
R1 = 0.0486
wR2 = 0.1431
R1 = 0.0660
wR2 = 0.1675
ꢂ1.614, 1.559
R1 = 0.0513
wR2 = 0.1428
R1 = 0.0523
wR2 = 0.1441
ꢂ0.863, 4.026
R indices (all data)
Largest diff. peak
and hole (eꢂ/Å3)
Crystallographic data (excluding structure factors) for all structures have been deposited at the Cambridge Crystallographic Data Centre, CCDC 1446241 (ZnF2(H2O)
(Hamtetraz) (1)),1044011 (ZnF2(Hamtetraz)2 (2)),1044009 (Zn3F5(H2O)2(amtetraz) (3)) and 1044010 ([NH4] (Zn4F5(amtetraz)4) 3H2O (4)). Copies of the data can be obtained,
free of charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, (fax: +44 1223 336033 or e-mail: deposit@ccdc.cam.ac.uk).
ꢁ
ꢁ

166
V. Pimenta et al. / Journal of Fluorine Chemistry 188 (2016) 164–170
Table 2
fluorine atoms (F(3)) result in an infinite trans-chain 1[ZnF3N2]
(Fig. 4 left). In the second chain, Zn(2)F4NO octahedra are linked to
two neighboring octahedra by two adjacent F–F edges and form a
zigzag chain 1[ZnF2NO] (Fig. 4 middle). The connection of these
chains by fluorine atoms F(1) and tetrazolate in N1,N2,N3,N4-
Selected inter-atomic distances of zincate and organic groups in ZnF2(H2O)
(Hamtetraz) (1), ZnF2(Hamtetraz)2 (2), Zn3F5(H2O)2(amtetraz) (3) and [NH4]
(Zn4F5(amtetraz)) 3H2O (4).
ꢁ
ꢁ
Zincate groups
Organic groups
bridging mode leads to a very compact network (r
= 3.098 g cmꢂ3).
1
2
3
Zn(1)-F(2)
Zn(1)-F(2)
Zn(1)-F(1)
Zn(1)-N(1)
Zn(1)-OW(1)
Zn(1)-N(2)
Zn(1)-N(4) x2
Zn(1)-F(1) x2
Zn(1)-F(1) x2
2.004(2)
2.005(2)
2.099(3)
2.113(4)
2.157(4)
2.160(4)
2.052(2)
2.099(2)
2.161(2)
N(1)-C(1)
N(1)-N(2)
N(2)-N(3)
N(3)-N(4)
N(4)-C(1)
N(5)-C(1)
N(4)-C(1)
N(4)-N(3)
N(3)-N(2)
N(1)-C(1)
N(1)-N(2)
C(1)-N(5)
N(1)-N(1)
N(1)-N(2)
N(2)-C(1)
C(1)-N(3)
C(1)-N(2)
1.329(6)
1.362(5)
1.285(5)
1.345(6)
1.330(6)
1.346(7)
1.336(3)
1.360(3)
1.280(4)
1.338(4)
1.354(4)
1.338(4)
1.30(1)
Consequently, the bidimensionnal compound 3 does not contain
any accessible porosity.
The structure of 4, obtained at the highest synthesis tempera-
ture, exhibits an anionic 3D framework with square tunnels along
[100] in which water molecules and ammonium cations are
inserted (Fig. 5 left). The oxygen or nitrogen atoms of isolated
species are statically disordered and are located on Ow(1)/N(11)
and Ow(2)/N(12) sites with O/N ratio equal to 0.75/0.25. The
structure results from two types of [100] chains, connected by
(amtetraz)ꢂ anions in the N1,N2,N4-bridging modes (Fig. 5 right).
These chains contain alternating ZnF2N4 monomers or Zn2F4N4
dimers linked by opposite fluorine corners to form infinite
1[ZnFN4] and 1[Zn2F3N4] chains, respectively. The metal cations
adopt an octahedral geometry in ZnF2N4 and a trigonal bipyrami-
dal geometry in Zn2F4N4. These chains were recently mentioned in
Zn(1)-F(3) x2
Zn(1)-F(1) x2
Zn(1)-N(1) x2
Zn(2)-OW(1)
Zn(2)-F(2) x2
Zn(2)-N(2)
Zn(2)-F(1)
Zn(2)-F(2)
Zn(1)-F(3) x2
Zn(1)-N(8) x2
Zn(1)-N(3) x2
Zn(2)-F(2)
Zn(2)-N(6)
Zn(2)-N(1)
Zn(2)-F(2)
Zn(2)-F(1)
Zn(3)-F(3) x2
Zn(3)-N(4) x2
Zn(3)-N(9) x2
1.990(1)
2.103(5)
2.149(5)
2.000(5)
2.029(1)
2.060(6)
2.120(5)
2.162(5)
2.015(4)
2.163(7)
2.158(6)
1.957(4)
2.008(6)
2.021(5)
2.081(4)
2.127(1)
2.047(4)
2.132(6)
2.169(7)
1.377(8)
1.348(8)
1.34(2)
1.348(8)
[Hdma] (Zn4F5(amtetraz)4) [17].
ꢁ
4
N(1)-C(1)
N(1)-N(2)
N(2)-N(3)
N(3)-N(4)
N(4)-C(1)
C(1)-N(5)
N(6)-C(2)
N(6)-N(7)
N(7)-N(8)
N(8)-N(9)
N(9)-C(2)
C(2)-N(10)
1.338(9)
1.354(8)
1.298(9)
1.335(9)
1.310(9)
1.37(1)
1.35(1)
1.36(1)
1.31(1)
1.33(1)
1.30(1)
1.36(1)
2.2. Influence of the synthesis temperature on the network
dimensionality
Four new fluorozincates have been prepared from the same
starting mixture at different temperatures. At 120 ꢀC, ZnF2(H2O)
(Hamtetraz) (1) and ZnF2(Hamtetraz)2 (2) develop 1D networks in
which the aminotetrazole linker is neutral. In 1, the N1,N2-bridging
mode is observed; the linker acts as a bridging ligand between two
metallic centres with a ratio Zn/Hamtetraz equal to 1. In 2,
Hamtetraz establishes only one NꢂꢂM bond in N1-bridging mode,
and the Zn/Hamtetraz ratio is 1/2. At 130 ꢀC, the tetrazole ligand is
deprotonated and displays a N1,N2,N3,N4-bridging mode in the 2D
network of Zn3F5(H2O)2(amtetraz) (3); the Zn/amtetraz ratio is 3.
This (amtetraz)ꢂ deprotonated form is also observed in the 3D
(amtetraz)ꢂ along b (Fig. 3 left and right). Two types of chains,
corresponding to two crystallographic independent Zn2+ sites, 8 h
(Zn(1)) and 16 m (Zn(2)), built up the inorganic columns (Fig. 4
right). Corner sharing Zn(1)F4N2 octahedra linked by opposite
Fig. 1. 1[ZnF2N2O] chain (left) and [010] projection (right) of ZnF2(H2O)(Hamtetraz) (1). Dashed lines represent the hydrogen bonds.
Fig. 2. 1[ZnF2N2] chain (left) and [100] projection (right) of ZnF2(Hamtetraz)2 (2). Dashed lines represent the hydrogen bonds.

V. Pimenta et al. / Journal of Fluorine Chemistry 188 (2016) 164–170
167
Fig. 3. [100] projection of Zn3F5(H2O)2(amtetraz) (3) (left) and [010] projection of inorganic column in 3 (right). Dashed lines represent the hydrogen bonds.
Fig. 4. View of 1[ZnF3N2] (left) and 1[ZnF2NO] chains (middle) observed in inorganic 1D [100] columns (right) of 3.
Fig. 5. [100] projection of [NH4]
ꢁ
(Zn4F5(amtetraz)4) 3H2O (4) (left) and connection of the [100] chains (right).
ꢁ
network of [NH4]
ꢁ
(Zn4F5(amtetraz)4)
ꢁ
3H2O (4), prepared at 140 ꢀC.
dimensionality. The second effect concerns the metal complexa-
tion; the aminotetrazolate anions are in competition with aqua
ligands. At 130 ꢀC, 3 contains two coordinated water molecules and
one azolate per three zinc atoms. At 140 ꢀC, water molecules are
replaced by nitrogen atoms giving 4 with one organic molecule per
one zinc atom.
In this case, the linker, in N1,N2,N4-bridging mode, ensures the
connectivity between three Zn2+ cations; the Zn/amtetraz ratio is
equal to 1. It clearly appears that the increase of the synthesis
temperature leads to the condensation of metal entities and the
increase of the dimensionality. Two effects influence the formation
of the solids: the partial decomposition of tetrazole and the
competition for the metal complexation. At highest temperature, a
part of Hamtetraz decomposes into ammonia which increases the
pH of the reaction media [28,29]. Consequently, the amino-
tetrazole is deprotonated, with four available electron-donor N
atoms, promoting the establishment of NꢂꢂM bonds and a high
2.3. Thermal behaviour of 3 and 4 and infrared spectra analysis for 4
The TG curve of Zn3F5(H2O)2(amtetraz) shows three successive
weight losses (Fig. 6). The first step between 180 ꢀC and 260 ꢀC is
attributed to the dehydration of 3 (exp.: 8.9%, calc. 8.8%). Then, the

168
V. Pimenta et al. / Journal of Fluorine Chemistry 188 (2016) 164–170
Fig. 6. Thermogravimetric analysis and thermal evolution of the X-ray diffractograms of Zn3F5(H2O)2(amtetraz) (3) under air at 2 ꢀC minꢂ1
.
second weight loss, up to 380 ꢀC, corresponds to the loss of
tetrazole linkers and HF gas, leading to the formation of ZnO and
ZnF2 (exp.: 22.0%, calc. 21.2%). At 900 ꢀC, ZnF2 is totally hydrolysed
in zinc oxide (exp.: 10.1%, calc. 10.7%). X-ray thermodiffraction
shows three domains (Fig. 6). 3 is stable up to 180 ꢀC; the loss of
two water molecules between 180 ꢀC and 280 ꢀC results in the
formation of an quasi-amorphous phase. Above 280 ꢀC, ZnF2
appears and is gradually transformed to ZnO above 380 ꢀC.
Three successive weight losses are also observed on the TG
curve of 4. The first event, between 130 ꢀC and 220 ꢀC, corresponds
to the loss of three water molecules and one ammonium fluoride
(exp.: 12.7%, calc. 12.0%). A plateau is observed up to 340 ꢀC and is
compatible with the existence of an intermediate phase. Then, a
second weight loss, in which the fluoride entities and a part the of
organic ligands are eliminated, leads to the formation of Zn(CN)2 at
360 ꢀC (exp.: 31.8%, calc. 32.9%). The last weight loss is assigned to
the hydrolysis of zinc cyanide to zinc oxide (exp.: 12.4%, calc.
12.5%). X-ray thermodiffraction is in good agreement with TG
analyses and confirms the existence of an intermediate compound
(Fig. 7). The initial phase is stable up to 140 ꢀC; above this
temperature, a shift of the peaks positions toward larger angles
occurs together with a variation of the intensities. These features
Fig. 7. Thermogravimetric analysis and thermal evolution of the X-ray diffractograms of [NH4]
ꢁ
(Zn4F5(amtetraz)4) .
3H2O (4) under air at 2 ꢀC minꢂ1
ꢁ

V. Pimenta et al. / Journal of Fluorine Chemistry 188 (2016) 164–170
169
Fig. 8. Evolution of the infrared spectra of [NH4]
ꢁ
(Zn4F5(amtetraz)4) 3H2O (4) after treatment at increasing temperatures under air atmosphere.
ꢁ
are consistent with the appearance of a crystalline intermediate
between 140 ꢀC and 280 ꢀC after the loss of NH4F and H2O. At high
temperature, ZnO is formed.
molecules are located. The loss of H2O and NH4F leads to a porous
neutral network with an expected ZnF(amtetraz) formula con-
taining unsaturated metal sites. The crystalline intermediate is
currently studied in order to determine its structure and to
evaluate the gas uptake capacity. Furthermore, we are currently
investigating the luminescence of these new materials as it is
already shown in Zn2+ hybrid materials [31]. Subsequent papers
will focus on these issues.
To evidence the presence and the elimination of ammonium
cations and water molecules in 4 on heating, IR spectra were
collected after heating at increasing temperatures under air and
cooling to room temperature. The spectra show two domains of
vibrational NꢂꢂH and OꢂꢂH energy [30]. The first domain between
3200 and 2810 cmꢂ1 and the second domain around 1400 cmꢂ1 are
respectively assigned to stretching vibrations and bending
vibrations (Fig. 8). When the heating temperature increases
several bands progressively disappear, which is in agreement
4. Experimental
4.1. Synthesis
+
with the elimination of the NH4 and H2O species. At 220 ꢀC, the
ammonium cations and water molecules are totally removed.
The starting reactants were ZnF2 (ꢃ99%, Alfa Aesar), 4%
hydrofluoric acid solution ‘4% HF’ (2.28 mol Lꢂ1) prepared from
‘40% HF’ (HF Riedel de Haen, 22.8 mol Lꢂ1), 5-aminotetrazole
The results obtained for
4 by thermal analyses and IR
spectroscopy confirm the existence of a crystalline intermediate
that is strongly structurally related to 4 after elimination of H2O
and NH4F. X-ray thermodiffraction shows that the structure is
globally maintained and a possible chemical formula for the
intermediate compound is ZnF(amtetraz). It can be assumed that
this phase contains unsaturated zinc coordination sites, known to
exacerbate gas adsorption; the theoretical porosity is estimated to
24%. In order to confirm this hypothetical formulation, the
structure is under determination by an ab initio approach and
complementary solid-state 19F NMR and BET studies are per-
formed. This work and the effect of the solvent on the network
topology will be discussed in a forthcoming of paper.
monohydrate ‘Hamtetraz H2O’ (99%, Alfa Aesar) and acetronitrile
ꢁ
solvent ‘ACN’ (Sigma–Aldrich, 19.0 mol Lꢂ1). All compounds were
solvothermally synthesized under autogenous pressure in Teflon-
lined Parr type autoclaves for 72 h. They were prepared from the
same starting mixture: ZnF2 (78 mg, 0.75 mmol), 4% HF (2.634 mL,
6 mmol), Hamtetraz H2O (78 mg, 0.75 mmol) and ACN (5 mL,
ꢁ
45 mmol) in molar proportions 1/8/1/60. Only the synthesis
temperature was changed to obtain four new complexes from
120 ꢀC to 140 ꢀC. All resulting products were washed with ACN,
filtered and dried at room temperature. For each preparation, X-ray
diffraction was used to find the known phases (EVA software) but
numerous peaks were not indexed. Then, crystals were selected to
identify the new phases. The comparison of simulated and
experimental diffraction patterns show that 1 and 2 are predomi-
nant at 120 ꢀC, 3 at 130 ꢀC and 4 at 140 ꢀC (Fig. S1). It must be noted
that in these conditions, no phase is pure: the crystalline powders
are a mixture of hybrid phases, contaminated with impurities,
3. Conclusion
This paper evidences the temperature effect on the network
dimensionality. In the case of hybrid fluorides associating zinc
cations and aminotetrazole, four new compounds with various
dimensionalities are identified for a narrow domain of synthesis
temperature (120–140 ꢀC): higher the temperature, higher the
network dimensionality and the aminotetrazole decomposition.
ZnF2, ZnF2
ꢁ
4H2O or [NH4] (ZnF3) issued from the aminotetrazole
ꢁ
decomposition at high temperature. In order to obtain pure phases,
several experiments were carried out in a CEM microwave oven
(MARS 5) and Teflon lined autoclaves at T = 160 ꢀC during 1 h.
[NH4]
ꢁ
(Zn4F5(amtetraz)4) 3H2O (4) displays an anionic 3D frame-
ꢁ
work with square cavities in which ammonium cations and water
Despite attempts to achieve phase purity for
1 and 2 by

170
V. Pimenta et al. / Journal of Fluorine Chemistry 188 (2016) 164–170
modification of the nature of reactants and the synthesis
temperature, only and were obtained pure. Pure
Appendix A. Supplementary data
3
4
Zn3F5(H2O)2(amtetraz) (3) appeared from a mixture of 156 mg
Supplementary data associated with this article can be found, in
ZnF2 (1.5 mmol), 5.27 mL HF 4% (12 mmol), 4 mL H2O (222 mmol),
the
online
version,
at
http://dx.doi.org/10.1016/j.
5.75 mL ACN (90 mmol), 156 mg Hamtetraz
250
L NH3 (Prolabo, 16.5 molLꢂ1, 4.1 mmol). The replacement of
the solvent mixture 4 mL H2O/5.75 mL ACN by 2.5 mL H2O/7.25 mL
ACN led to pure [NH4] (Zn4F5(amtetraz)4) 3H2O (4). The crystalline
purity of 3 and 4 was confirmed by X-ray powder diffraction
(Fig. S2).
ꢁ
H2O (1.5 mmol) and
jfluchem.2016.07.003.
m
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