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An FTЦRaman Study of the Template ЦFramework Interaction in AlPO4-Based Molecular Sieves.

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1191 Crystal data for 2, C,,H,,MO,N,NIO,,:
M , = 998.87, triclinic. R. a =
10.1808(4), h=11.8098(5), c =13.2504(5)A, ct = 97.141(1). fi =106.978(1),
",
,-110.723(1)'. V = 1 3 7 8 2 1 ( 1 0 ) ~ ' , Z = 2 , p ~ , , , , = 2 . 4 0 7 g c m ~ 3 , M o , , ( ~ . =
0.71073
p = 24.83 c m - ' ; experimental and structure solution as for 1, see
ref. [16]; R1 = 0.0566. wR2 = 0.1087 for all 3947 reflections (R1 = 0.0412 for
3245 reflections with F,>4u(F,)).
[20] Crystal data for 3.8H,O. C,,H,,Cu,Mo,,N,O,,:
M , = 3214.16. monoclinic,
121~. u = 21.797(2). h = 3.7557(4). c = 24.42514) A. /3 = 108.823(2) , V =
1892.514) A', Z = 1. pcrlrd= 2.820gcm-', Mo,, radiation (1. = 0.71073 A),
p = 35.49cm-'; experimental and structure solution as for 1, see ref. [16];
R1 = 0 0749. 11R2 = 0.1489 for all 1361 reflections (Rl = 0.0627 for 1058 reflections with F,>4o(F0)).
[21] B. M. Gatehouse. P. Leveratt, J. Chem. Soc A 1968, 1399.
[22] K.-J. Range, A Fdssler, Acta Crj~.~fallogr
Sect. C. 1990. 46. 488.
[23] M. 1. Khan. Q. Chen, J. Zubieta, Inorg. Cl7im Actrr 1993, 213. 325.
[24] Y. Xu, L.-H. An, L:L. Koh, Chem. Matrr. 1996, 8, 814.
A),
In this study FT-Raman spectra have been obtained of morpholine within SAPO-34 and MeAPO-34 (Me = Zn, Mn, or
Mg) and of cyclohexylamine within SAPO-44 and MeAPO-44
species. Both the 34 and 44 structure types are based on the
framework of the zeolite chabazite, and they are selective catalysts for the formation of olefins from methanol.['] The synthesis and characterization of the samples investigated has been
reported in detail, and the Br~nstedacid sites in the calcined
samples have been assessed quantitatively by temperature-programmed desorption of ammonia.[*] Spectral assignments reported in this communication were aided by Raman measurements on liquid morpholine, cyclohexylamine, piperidine, and
tetrahydropyran in both neutral and protonated forms.
Figure 1 shows the N-H and C-H stretching region of the
Raman spectrum of morpholine, protonated morpholine, asprepared SAPO-34, and three MeAPO-34 samples. In neutral
An FT-Raman Study of the
Template-Framework Interaction
in AlP0,-Based Molecular Sieves
Sunil Ashtekar, Patrick J. Barrie,* Mark Hargreaves,
a n d Lynn F. Gladden*
The role played by the organic template in the synthesis of
zeolite and AlP0,-based molecular sieves is a poorly understood but frequently discussed topic.[*' AIP0,-based molecular
sieves are formed from the hydrothermal treatment of reactive
gels containing an organic base; the organic base is typically an
amine or quaternary ammonium complex. Incorporation of silicon into the framework leads to SAPO molecular sieves, and
incorporation of a metal (Me; for example Zn, Mn, Mg, Co)
leads to MeAPO species.[*]Some structures may be formed with
many different templates, while others require very specific templating species to be present.r31The commercial importance of
molecular sieves means that there is an increasing need to understand more about the template- framework interactions that
affect their synthesis.
Recently a number of computational studies have attempted
to provide insight into the template- framework interaction.[41
There are, however, problems in choosing appropriate force
fields and modeling the Coulombic interactions that exist between the framework and the template. Single-crystal X-ray
diffraction and I3C solid-state NMR studies on the template
structure and position are frequently hampered by considerable
disorder in the template location, particularly for SAPO materials.[*] In this communication we show that FT-Raman spectroscopy is an effective probe of the organic template and so has
the potential to examine template- framework interactions.
Since the development of near-infrared Fourier transform methods, Raman spectroscopy has undergone a renaissance with
much improved signal-to-noise ratios.[61The different selection
rules from conventional infrared spectroscopy results in only
weak scattering from the molecular sieve framework, and so the
organic template may readily be studied.
[*] Dr. P J. Barrie, Dr. L. F. Gladden, S. Ashtekar, M. Hargreaves
Department of Chemical Engineering
University of Cambridge
Pembroke Street, Cambridge CB23RA (UK)
Fax: Int. code +(1223)334-796
e-mail' pjblO(<lcheng.cam.ac.uk
[**I We thank BNFL for provision of the Raman spectrometer.
876
G VCH Verlugsgesellschaft mhH, 0.69451
Weinheim.1997
3400
-
3200
G / cm-'
Figure 1. FT-Raman spectra of morpholine (a) and protonated morpholine (b),
as well as of morpholine in SAPO-34 (c), MgAPO-34 (d), MnAPO-34 (e), and
ZnAPO-34 (f) in the region 2500-3600 cm- '. The analysis of the chemical composition of the samples determined by ICP/AES yielded the following relative amounts
of framework elements: Si 0.164. Al 0.480, P 0.354 in SAPO-34; Mg 0.16, A1 0.35,
P 0.49 in MgAPO-34; Mn 0.13, A10.42, P 0.45 in MnAPO-34; Zn 0.21, A1 0.28, P
0.51 in ZnAPO-34 The spectra were obtalned on a Nicolet Magna-IR 750 spectrometer equipped with a Raman module and an InGaAs detector. The samples
were exposed to a laser power of 300-500 mW at an excitation wavelength of
1064 nm (Nd:YAG laser). Two hundred scans were co-added. The spectral resolution was 4 cm- I . An FT-Raman spectrum of CoAPO-34 was not informative due
to the strong cobalt d-d absorption band in the near-infrared region.
morpholine two N -H stretching bands are clearly observed at
3342 and 3302 cm- ' . The six-membered ring of morpholine will
be in the chair conformation, and the higher frequency band is
assigned to the conformation with the nitrogen atom's lone pair
in the axial position, while the lower frequency band has this
lone pair in the equatorial position."' The CH, stretching region
normally occurs at 2850-3000cm-', and the band at
2962 cm- ' and the shoulder at 2922 cm-' in liquid morpholine
can be attributed to antisymmetric stretching of CH,(O) and
CH,(N) groups. The region 2700-2830 cm-', known as the
Bohlmann region, contains principally overtone and combination bands enhanced by Fermi
These have considerable intensity for morpholine and depend mainly on the presence of a lone pair on the heteroatom adjacent to the CH,
11.121
0570-0833~Y7;3608-1)876S 17.50+ .SO10
Angen,. Clien?. Int. Ed. E n d . 1997. 36, No. 8
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Addition of dilute hydrochloric acid to morpholine protonates the amine group, resulting in loss of the simple N-H
stretch. In general, NH: vibrations give rise to weak Raman
bands below 3000 cm-', which tend to be masked by the more
intense CH, asymmetric vibrations. Protonation of the amine
group also removes the intense Bohlmann bands in the region
2700-2830cm-', as there is no longer any lone pair on the
nitrogen atom. Thus the main spectral features of protonated
I
morpholine are antisymmetric CH, vibrations (overlapping
bands at 2983 and 2970 cm- ') and symmetric CH, vibrations
(2871 cm-'); the latter are possibly affected to some extent by
the lone pair on the oxygen atom.
The spectra of as-prepared SAPO-34 and MgAPO-34 are similar to that of protonated morpholine but the signals are slightly
shifted to higher wavenumber: the major bands are now at
3012/2981 cm- ' and 2882 cm- '. This shift is probably a reflection of the confined space around the organic molecule. The
spectrum thus confirms that the organic template is in the pro- 1600 1500 1400 1300 1200 1100 1000 900
800
Y/cm-'
tonated form, which is to be expected given that the samples
were prepared under mildly acidic pH conditions.[*]
Figure 2. FT-Raman spectra ofmorpholme (a) and protonated rnorpholine (b), as
well as morpholine in SAPO-34 (c). MgAPO-34 (d), MnAPO-34 (e), and ZnAPOIn the case of MnAPO-34 the CH, antisymmetric stretch is
34 (f) in the region 600-1600cm".
now split into two resolved bands, at 3014 and 2975 cm- while
in ZnAPO-34 three bands are observed at 3026, 3004, and
2977 cm- * (Figure 1). This provides clear evidence the template
structure or location in MnAPO-34 and ZnAPO-34 is different
Upon protonation, most of the methylene bands shift by about
from that in SAPO-34, and thus that there are different tem4 cm-' to higher frequency; there is now a symmetric C N + C
plate-framework interactions within them. The most likely inband at 876cm-', and the ring-breathing motion occurs at
teractions are hydrogen bonding between any Brernsted OH acid
lower frequency (825 cm-'). The spectra of SAPO-34 and
groups in the framework and the oxygen atom of the morphoMeAPO-34 species show small changes in frequency and relaline, and between the NH: hydrogens and oxygen atoms in the
tive intensity relative to that of the signals of pure protonated
framework. Such hydrogen bonding interactions are expected
morpholine, with some additional peaks that are again indicato cause some changes in vibrational frequency. Maximizing
tive of interactions between template and framework.
these favorable interactions with the framework may also cause
In conclusion, FT-Raman spectroscopy allows a vibrational
the morpholine molecule to adopt different conformations withspectrum of the organic template occluded in molecular sieves to
in the pore space (e.g., chair and boat conformations), and this
be obtained with little interference from the framework. Small
could cause the peak splittings that are observed here.
increases in vibrational frequency are observed that probably
A similar series of spectra were obtained of SAPO-44 and
relate to the confined space around the organic template. In the
MeAPO-44 species with cyclohexylamine as templating agent.
case of morpholine within MeAPO-34 species, significant peak
The neutral template as a pure liquid shows two NH,
splittings occur, indicating a strong template- framework interbands, due to symmetric and antisymmetric stretches, and
action and a possible change in conformation of the organic
strong bands in the Bohlmann region as well as the expected
molecule. Although Raman spectroscopy has not revealed preCH, vibrations. Protonation of cyclohexylamine results in a
cise information about the nature of template-framework insimpler FT-Raman spectrum with three strong bands at 2949
teractions, it does show that differences exist between the sam(asymmetric CH, stretch), 2908 (CH stretch) and 2863 cm-'
ples studied. The unexpected behavior observed for the
(symmetric CH, stretch) .[12,' 31 The spectra of SAPO-44,
morpholine/AlPO,-34 system is a n interesting result that warMgAPO-44, MnAPO-44, and ZnAPO-44 are virtually identical
rants further investigation by other techniques.
to this spectrum of protonated cyclohexylamine, but with a
small shift (2-8 cm-') to higher wavenumbers for all three
Received: October 25, 1996
main bands. In contrast to the situation for morpholine within
Revised version: January 2, 1997 [Z9690IE]
German version. Angew. Chem. 1997, 109,919-921
MeAPO-34 species, no additional peaks are observed in the
cyclohexylamine/MeAPO-44 system. This is indicative of less
interaction between the template and the framework, and probKeywords: aluminum phosphate * host -guest chemistry
ably reflects the fact that cyclohexylamine does not contain any
molecular sieves * Raman spectroscopy template synthesis
oxygen atom to which hydrogen bonding might occur.
Figure 2 shows the FT- Raman spectra in the low frequency
111 R. Szostak, Handbook of Molecular Sieves, Van Nostrand Reinhold, New
region for morpholine and the various element-substituted 34
York, 1992.
framework structures. In conventional IR spectroscopy this re[2l E. M. Flanigen, B. M. Lok, R L. Patton, S . T Wilson, Pure Appl. Chem. 1986,
58, 1351.
gion is dominated by the tetrahedral stretching motions of the
131 E. M . Flanigen, R. L. Patton, S. T. Wilson in Innovarlon in Zeolite Materials
framework, and little information on the template can normally
Science (Stud. Surf Sci. Catal. 1988, 37). p. 13.
be gleaned. By contrast, the FT-Raman spectra are dominated
[4] a) D. W. Lewis, C. R. A. Catlow. .I.M. Thomas, D. J. Willock. G. J Hutchings.
Nufure 1996,382, 604; b) D W Lewis, C. M. Freeman, C. R. A. Catlow, J
by the organic template. For pure liquid morpholine, fundaPkys. Chem. 1995,99,11194; c) T. V. Harris, S . I. Zones in Zeolires and Relurrd
mental bands such as methylene scissor (1460 and 1444 cm- '),
Microporous Materials. State ofthe Art 1994 (Stud. Surf. Sci. Carat. B 1994,
wag (1305 cm- I ) , twist (1202 cm-I), and rocking motions are
84), p. 29.
[5] J. J. Pluth, J. V. Smith, J. Phys. Chem. 1989, 93, 6516.
observed in this region, together with the symmetric CNC
[6] D. B. Chase. J A m . Chem. SOC.1986, 108,7485.
stretch (910 cm-') and a ring-breathing motion (834 cm-1).1121
-
',
-
Angew. Chem. Inr. Ed. Engl. 1997, 36, N o 8
0 VCH Verlagsgesell,~chaftmbH. 0-69451 Weinkeim, 1997
0570-0833/9713608-0877$1?.S0+ .SO10
877
COMMUNICATIONS
[7] a ) M. W. Anderson, B. Sulikowski, P. J. Barrie, J. Klinowksi, J: Phys. Chem.
1990, Y4. 2730, b) T. h i , H. Matsuda, H. Okaniwa, A. Miyamoto, Appl.
C o r d 1990. 58. 155.
[8] a ) S. Ashtekar. S V. V. Chilukuri, D. K. Chdkrabarty. J: Phys. Chem. 1994.98,
4878: b) S. Ashtekar. S. V. V. Chilukuri, A. M. Prakash, C. S. Harendranath,
D. K Chakrabarty. ihid. 1995, 99. 6937; c) S. Ashtekar, S. V. V. Chilukuri.
A. M. Prakash. D. K. Chakrabarty, ibrd. 19%, 100, 3665; d) S. Ashtekar,
A. M. Prakash, D K. Chakrabarty, S. V. V Chilukuri, 1 Chem. Soc. F a r u d q
Truns 1996. 92. 2481.
[9] D. Vedal, 0 H. Ellestad, B. Klaboe, Spectrochirnica Acfa A 1976, 32, 877.
[ l o ] E Bohlmann. Ange.ric Chem. 1957, 6Y. 641.
I
Mol. Srrucr. 1973, 17, 249.
[ll] E. E. Ernstbrunner, J. Hudec, .
1121 F.R. Dollish. E. G. Fateley, F. F. Bentley, Characteristic Ruman Frequencies of
Urganrc Cotnpound.~,Wiley, Chichester, 1974.
[I31 D. Lin-Vim. N. B Colthup, W. G. Fateley, J. G. Grasselli, Handbook o f l n / r u r ~ drind Runian Chararteri.stic Frequencies of Organic Molecules, Academic
Press. San Diego, 1991.
tic strategy for these is based on 1) conversion of the appropriate
vicinal bis(hydroxymethy1)-TTF 1['I into its corresponding,
new bis(sulfanylmethy1)-TTF 2 and 2) disulfide bridge formation by selective, intramolecular, oxidative ring closure.
We present here a straightforward access to new 3a and 3b by
the steps shown in Scheme 1 and report on their n-donor ability.
The latter is demonstrated by preliminary electrooxidation experiments with generation of the radical cation salts 3a.PF6 and
3a. ClO,, whose X-ray structures are presented together with
that of neutral 3a.
4a (59%)
4b (M)%)
NaBH4,ZnCI,
A, THF
Method
Studies of the First S-Position Isomer
of Bis(ethylenedithio)tetrathiafulvalene**
CH+COCH,
CH2SCOCH3
DIBAI-H
-78°C. CH,CI,
Over the last two decades chemical modifications of the tetrathiafulvalene (TTF) framework[" have been developed to favor
enhanced dimensionality in the related charge-transfer salts.[']
One of the most promising strategies consists of introducing
additional sulfur atoms at the periphery of the TTF skeleton. In
particular, the famous bis(ethy1enedithio)-TTF (BEDT-TTF) is
known to form superconducting salts with the highest T, yet
observed for that series;[3,41 all of them exhibit two-dimensional
(2-D) character (for example p and K phases). The prominent
role of the outer sulfur atoms has also been recognized in highly
conducting or superconducting salts of TTF derivativesF5- 71
We therefore focused our attention on the peripheral S-position isomers of BEDT-TTF and (ethy1enedithio)-TTF (EDTTTF) A, B, and C as new synthetic targets. Our general synthe-
0
Ir
[*] Dr. P. Hudhomme, Prof. G. Duguay
Laboratoire de Synthese Organique
Universitk de Nantes
2 rue de la Houssiniere, 44072 Nantes Cedex 03 (France)
Fax: Int. code +(2)4074-5000
e-mail: hudhommec,a,chimie.univ-nantes.fr
Dr P. Blanchard. Dr. M. Salle. S Le Moustarder, Prof. A. Riou,
Prof. M. Jubault, Prof. A. Gorgues
lngenierie Moleculaire et Materiaux Organiques Universite d'Angers
2 Boulevard Lavoisier, 49045 Angers Cedex (France).
Fax: Int. code +(2)4173-5405
e-mail . blanchariu univ-angers.fr
[**I Financial support was provided by the CNRS, the Ministerede 1'Enseignement
Superieur et de la Recherche (MESR; research studentship for P. B.)$and the
Ville d'Angers (grant for S. L. M.). We thank Dr. S. Jobic, Institut des Materiaux de Nantes. for extended Hdckel calculations.
878
VCH Verlug~ge~eilschuft
mhH 0-69451 Weinheim. 1997
CHzOH
Sa, b
Piktrick Hudhomme,* Philippe Blanchard,*
Marc Salle, Soazig Le Moustarder, Arn6di.e Riou,
Michel Jubault, Alain Gorgues, and Guy Duguay
A
AorB
f--
I
(91%)
2b (96%)
28
38 R,R=SCH3
3b R-R = SCHzCH2S
Scheme 1. a: R, R = SCH,; b: R-R = SCH,CH,S. Synthesis of the disulfide TTFs
3 from bis(hydroxymethy1)-TTFs 1. Method A . DEADIPPh,. CHJOSH, THF,
5a: 58%. Method B: Me,NCH(OEt),, CH,COSH, A, CH,CI,. 5a: 59%. 5b: 60%.
The starting materials l a and Ib were prepared by our standard procedure.Iac1Cross-coupling (with P(OMe),) of two 2thioxo-I ,3-dithiole or 2-oxo-l,3-dithiole moieties afforded the
unsymmetrical 2,3-dimethoxycarbonyl derivatives 4a and 4b.
Reduction of the ester functionalities gave l a and Ib in 83 and
70 YO yield, respectively. Although the obvious reaction sequence starting from 1 (tosylation or bromination followed by
nucleophilic displacement with sodium hydrosulfide) failed,"]
the Mitsunobu reaction["] could be used. Thus, a one-pot conversion into 5a was achieved by treatment of l a with the diethyl
azodicarboxylate/triphenylphosphane (DEAD/PPh,) complex
and subsequent in situ displacement of the resulting leaving
group with thiolacetic acid, as described by Volante." However, in the case of compound Ib this procedure was not convenient due to the well-known sensitivity of the ethylenedithio
bridge with respect to bases."'] The hydroxy group was therefore activated with N,N-dimethylformamide dialkylacetal.[' 31
By treatment of Ib with excess thiolacetic acid and N,Ndimethylformamide diethylacetal, the corresponding bis(thiolester) 5b was formed in 60% yield. Compound 5a was
obtained from l a in 58 % yield by the same route.['41The dithi01s 2a and 2b were then generated by reduction and isolated in
91 and 96% yields, respectively, as orange/red, crystalline powders after purification on florisil and recrystallization." 51 Oxidative conversion of the dithiols into the disulfides['61was first
attempted for 2a with iodine in acetone/ethanol: a dark green
charge-transfer complex formed rapidly as a result of the n-do-
057#-0833~97~3608-0878$17
SO+ 5010
Angew Chem Int Ed Engl 1997, 36 No 8
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