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Designed Restructuring of Iodine with Microporous SiO2.

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tion no, CCDC-179-119. Copies of the data can be obtained free of charge on
application to The Director, CCDC, 12 Union Road, Cambridge CB2 1%
UK (fax: int. code +(1223)336-033; e-mail: teched(ychemcrys.cam.ac.uk).
J. Bregman, K Osaki, G. M. J. Schmidt, F. I. Sonntag, J. Chem. SOC.1964,
2021
S. M . Aldoshin. M. V. Alfimov, L. 0.Atovmyan, U. F. Kaminsky, V. F. Razurnov. A G. Rachinsky, Mol. Cryst. Liq. Crvsr. 1984, 108, 1
G. Kaupp. E. Jostkleigrewe, H. J. Herrmann, Angeu. Chem. 1982, 94, 457;
A n g m . Chern. I n l . Ed. Engl. 1982, 21, 435.
H. G. Voelz. Angrit.. Chem. 1975,87,721; Angeu. Chem. Int. Ed. Engl. 1975,
14, 688: ti. Hczel. h i d . 1973, 85, 334 and 1973. 12, 298.
As long as product molecules of 2 are not yet aligned in their own crystal lattice,
hut in the rebuilt lattice of 1, short-wavelength excitation can cause a photochemical reverse reaction. Only crystalline 2 photodimerizes exclusively to
form the cyclobutane derivative [9].
The lack of absorption of light at 2. = 365 nm by the crystalline product 2
prevents the formation of its [2 +2]-dimer. Irradiation of 1 (4 h) with light from
a 150 W Hanau Hg high-pressure lamp passed through a Wertheimer UVW-55
bandpass filter (isolation of the 365nm light with 2.8% contribution from
334 nm light ( % transmission <1 at 315 nm and at 410 nm)) in a powder
cuvette leads to a considerable shift of the diffuse reflectance spectrum t o
curve bin Figure I . whereas the broad-band irradiation (>.> 300 nm) ofcrystalline 2 produces a decrease in the long-wavelength absorption and an increase
in a band of the photodimer 191 at 266 nm.
G. Kaupp. G'IT Fach;. Lab. 1993,37,284, 581, and references therein (English
translation In WWW under http://kaupp(&kaupp.chemie.uni-oldenburg.de);
Angeu Chon. 1992, 104.606. 609; Angeu. Chem. Inr. Ed. Engl. 1992, 31, 592.
595: G. Kaupp. J. Schmeyers. ihrd. 1993, 105, 1656 and 1993, 32, 1587.
The compounds 1 and 2 melt at 92.8 and 118.2"C, respectively. Their enthalpies of melting according to differential scanning calorimetry (DSC, 40150 C. 20 K per min) are AHfu= 19.6 and 25.4 kJmo1-I After solidification
of 1 another phase with m.p. 73.4 C and AHcu=18.7 kJmol-' appears
without chemical change (according t o 'H NMR analysis). The state diagram
of 1:2 is complicated: between the eutectics at 67 and 114°C there are several
other endothermic peaks in DSC irrespective of the mixing ratio (particularly
pronounced at 80 and l O l ' C ) , which cannot yet be reliably interpreted.
Microscopy of copulverized samples of 1 and 2 indicate that liquid phases can
be excluded
S. K . Kearsley. G. R. Desiraju, Proc. R . SOC.A 1985. 397, 157.
The 90% light penetration depth derived with the Lambert-Beer law for cmsx
-15000 Lmol. ' c m ~ i . r / = 1 . 2 3 9 g c m ~ ' f r o m F i g u r1e atapproximatelydiagonal position of the chromophore is less than 100 double layers at 302, 313,
and 334 nm. and 370 double layers at 365 nm.
Designed Restructuring of Iodine
with Microporous SiO,**
Gernot Wirnsberger, Harald P. Fritzer, Alois Popitsch,
G i a n p i e t r o van de Goor, and Peter Behrens*
The pore systems of zeolites, which are accessible to many
ions and molecules, can not only be used in technical applications as catalysis and sorption, but also offer the opportunity for
a rich host -guest chemistry. Inorganic clusters with special electronic"1 or magneticC3] properties can be stabilized inside the
well-defined and uniform cavities of aluminosilicate zeolites.
However, the use of zeolites as host matrices bears an inherent
problem: As the framework is composed of [AlO,,,]- and
[SiO,,,] tetrahedra, it carries a negative charge that must be
balanced by the inserted species themselves or by guest cations
that are present in addition. Therefore, the properties of the
guest components will always be influenced by ionic interactions
with the host matrix or with the charge-compensating guest
cations.
In our attemptsf4]at the restructuring of guest components by
porous solids, we have used porosilsf5]rather than zeolites as
host components. The structures of porosils resemble those of
zeolites; however, their frameworks are composed of [SiO,,,]
tetrahedra only, which are interlinked through their vertices;
thus, the composition of a porosil framework is neutral S O , .
Porosils are prepared under mild solvothermal conditions; organic molecules, which are necessary to form a desired porosil
structure, become occluded in the cavities of the crystallizing
SiO, framework.f61The organic molecules can be removed oxidatively by calcination (treatment at high temperature), leaving
behind a (thermodynamically metastable)['] microporous SiO,
modification, whose empty void system can now be filled. In the
case of host-guest compounds with a porosil as the host component and with neutral guest species, the interactions are restricted to weak van der Waals type forces. The void structure of
the host framework thus determines the geometrical arrangement of the guest species and consequently also limits the electronic interactions between them. Insertion compounds of
iodine serve as an especially impressive example of this concept,
as changes in the electronic properties of the guest arrangement
can be monitored directly by changes in color.
We have used porosils with zero-, one-, two-, and threedimensional pore systems as host compounds : decadodecasil
3R (DDR["), silica-ZSM-22 (TON), silica-ferrierite (FER),
and silicalite-I (MFI). Their cavities or channel systems are
shown in Figure 1. Since the diameters of the pores of these host
Tailor-made host systems with designed topologies and
adapted surface properties are an important prerequisite for
supramolecular inorganic host-guest chemistry.['] Herein, we
show how the interactions between iodine molecules can be
controlled by the topotactical insertion into selected, crystalline
porous materials which assume a structure-directing role for the
arrangement of the guest species.
[*] Prof. Dr P. Behrens, D r G. van de Goor
Institut fur Anorganische Chemle der Universitat
Meiserstrasse 1, D-80333 Munchen (Germany)
Fax: Int code +(89)5902-578
e-mail: phew anorg.chemie uni-mnenchen.de
DipILIng. G Wirnsberger, Prof. Dr. H. P. Fritzer,
lnstitut fur Physikalische und Theoretische Chemie
Technische Universitat
A-8010 Graz (Austria)
Dr A. Popitsch
Institut fur Anorganische Chemie
Karl-Franzens-tiniversitii
A-8010 Graz (Austria)
[**I
Part of this work was supported by the Deutsche Forschungemeinschaft (Be
1664/1-2) and the Fonds der Chemischen Industrie. We thank Andreas M.
Schneider for assistance with the preparation of the figures.
A n g m . Chem lnr. Ed. Engl. 1996, 35, N O . 23/24
0 VCH
Fig. 1. Structures of the host systems (oxygen atoms are omitted): For DDR, a view
of the layers consisting ofpentagon dodecahedra is given on the left. In an ABCABC
stacking of these layers, cages (center) are formed which are typical for this structure. Each cage is surrounded by three other cages arranged at angles of 120" to each
other (right). For the other porosiis, views along the channels (left and center) and
schematic views of the channel systems (right) are given .
Verlagsgesellschufr mbH, 0-694S1 Weinherm. 1996
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systems are similar, they are suitable
for investigating the influence of the
different dimensionalities on the interactions between the iodine molecules.
Figure2 shows the colors of the
iodine-porosil composites that were
prepared by the insertion of iodine into these hosts. Iodine in DDR is violet,
similar to the color of gaseous iodine,
indicating that the iodine molecules
are in a vapor-phase-like state. In contrast, the iodine in the TON host, in
Fig- 2- Colors of the
which the unidimensional channel sysiodine - porosil
comtem permits interactions between the
posites compared to that
,f solid
From top
iodine molecules in one dimension, is
to bottom: iodine in
violet to dark blue, similar to the color
DDR, iodine in TON,
observed for iodine-starch comiodine in FER, iodine in
pounds. Iodine inserted into the twoMFI, and solid iodine.
dimensional channel system of FER
exhibits a color between that of iodine
in DDR and TON. Interactions between iodine molecules in
three dimensions, which are, however, regularly interrupted by
the MFI silica framework, result in a red-brown color resembling that of liquid iodine.
These visual impressions can be quantified by UV/Vis spectroscopy. The absorptions in the visible region, which are responsible for the colors, vary in a characteristic fashion (Fig. 3 ) .
The spectrum of iodine in DDR
exhibits a relatively strong band
at 518 nmandoneofweakerintensity at 688 nm. The positions
of these bands coincide with
those observed for gaseous
iodine, and are atrributed to
the B+X transition (518 nm)
and the A+X
transition
(688 nm).['ol The notion that
iodine in DDR is in fact in a
vapor-phase-like state is also
supported by the composition
of the
which fits
for a structure in which each
cage of the DDR host structure
is occupied by one iodine moleI
300 400 500 600 700 800
cule and thus the iodine molehlnm
cules can be regarded as isolatFig 3. UV/Vis spectra (converted
ed from each other.["b1
to Kubelka-Munk functions F(R,))
In contrast to the cage strucof the iodine-porosil composites
ture of DDR, the one-dimenand of solid iodine: a) iodine in
DDR, b) iodine in TON, c) iodine in
sional channels of TON permit
FER, d) iodine in MFI, and e) solid
interactions between the iodine
iodine.
molecules along the channel
axis. The transition from isolated molecules to molecules that are part of an infinite chain (in
the limiting case) should manifest itself by a shift of the absorpIn fact, a 22 nm shift of the
tion bands to higher
B t X transition to 540 nm was observed for the iodine in TON.
In addition, the spectrum contains a broad shoulder in the region of the A + X transition, which is responsible for the dark
blue hue of this compound. Thus, the changes in the electronic
structure caused by the chainlike aggregation of the iodine molecules (which in turn is caused by the templating action of the
TON framework) are not only evident from a shift of the absorption band maxima, but also from changes in the intensities
and thus the transition probabilities.
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2778
V C H VerfagsgesellschafmbH, 0-69451 Wemheim, 1996
A further enhancement of the interaction between the iodine
molecules might be expected for the insertion compound of
FER, which possesses a two-dimensional channel structure.
However, the electronic spectrum shows that in this case the
geometric restrictions by the host are too strong to allow the
formation of a two-dimensional layered structure (which would
be regularly pierced by SiO,). The double maximum in the
strongest absorption band indicates the presence of two different iodine species, one of which is in a vapor-phase-like state
(maximum at 519 nm). For the second maximum at 537 nm, we
observe a shift to higher wavelengths, similar to that observed
for iodine in TON.
The MFI-based insertion compound reveals most clearly the
tendency of the iodine molecules to use the available volume for
maximizing their interactions. It possesses the highest concentration of
and its UV/Vis spectrum shows enhanced intensity in the region between 400 and 260nm in which
liquid iodine also has its strongest
abs~rptions.['~l
The Raman spectra in Figure4
confirm and supplement the picture
gained from the UV/Vis spectra. The
band for iodine encaged in the DDR
host structure occurs at 208cm-',
similar to that of gaseous iodine
(213 cm-'), which again supports
the idea of a vapor-phase-like state
of the inserted iodine. For the iodine
molecules restructured to a chainlike
arrangement by the TON framework,
the iodine-iodine vibration shifts to
199 cm-'. We attribute this shift
to the presence of intermolecular
iodine-iodine interactions, which
cause a weakening of the intramolecular iodine-iodine bond, resulting in
a decrease of its force constant.
However, a comparison with the
spectrum of solid
(Fig. 4e)
shows that the extent of these interactions is much weaker than in bulk
Fig. 4. Raman spectra of
iodine. The splitting of the B t X
the iodine-porosil comtransition in the UV/Vis spectra indiposites and of solid iodine:
cated the presence of two different
a) iodine in DDR, b) iodine
in TON, c) iodine in FER,
iodine species for the iodine in FER;
d) iodine in MFI, and e) solid
the Raman spectrum confirms this
iodine; I in arbitrary units.
presumption. We ascribe the weak
band at 210 cm-' to isolated iodine
molecules, and the stronger band at 196 cm-' to a chainlike
arrangement of iodine molecules. Evidently, the apertures of the
ten-ring channels are just large enough to allow for interactions
between the iodine molecules (band at 196 cm-'), whereas the
iodine molecules in the eight-ring channels remain isolated
like those in iodine- DDR. For the insertion compound of MFI
we observe a band at 202 cm-', which we attribute again to
a chainlike arrangement of iodine molecules. In addition,
this signal exhibits a shoulder at 188 cm-'; this has to be
ascribed to iodine molecules that are allowed to exert even
stronger interactions. The only regions that permit such interactions are the spherical voids at the intersections of the channel
systems. On the one hand, each of these voids (9 A diameter) can
accommodate several iodine molecules, on the other, the molecules inside them are able to interact with those molecules that
reside in the channels through the ten-ring channels. It is
0570-0833/96/3523-27783 15-00+ .25/U
Angew. Chem. Int. Ed. Engl. 1996, 35, No. 23/24
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noteworthy that broad bands in the range from 175 to 185 cm-'
in Raman experiments on liquid iodine have been attributed to
the presence of (12)n molecular clusters.[161
Our investigations on iodine insertion compounds prepared
by topotactical reactions show that by restricting the geometrical arrangement of the iodine molecules, the electronic properties of the guest species can be engineered.
[to] An extensive description of these transitions and of the term s h e m e of gaseous
iodine can be found in: R. S. Mulliken, J. Chem. Phxs. 1971. .jj,288- 309. and
references therein.
[l11 a) From thermogravimetry (Mettler TA 2, heating rate: 10 K inin- I . reference:
A1,0,, crucible material AI,O,, atmosphere: Ar, flux rate 5 Lh") the following compositions result D D R : 120SiO,:6.0I2. TON 24Si0,'1.211.
FER: 36SiO2.3.2I,, MFI: 96SiO,:11.51,. b) The free volume of the cages is
350 A3, and thus, there is sufficient space to accommodate more than one I,
molecule per cage. Modeling studies in our group have shown. however, that
the inclusion of a second molecule per cage is disfavored energetically over
single occupation. The shortest intermolecular iodine iodine distance from the
modeling studies is about 5 5 A, clearly larger than the value of twice the van
der Waals radius of iodine (4.3 A). A. M. Schneider, P. Behrens. unpublished
results.
[12] J. K. Burdett, Prog. SolidSrare Chem. 1984, I S , 173-255.
[13L In order to compare the iodine concentrations in the different porosils. we have
3~normalizedthem to molecules per 1000 A'. The following values were obtained: D D R : 0.886, TON: 0 989. FER: 1.63, MFI: 2.15.
[14] M. Yao, N. Nakamura, H. Endo, 2. Ph,v,c. Chem. 1988, 157. 569-573.
1151 B. V. Shanabrook. J. S . Lannin. Solid Srate Commun. 1981. 38, 49-52.
[16] R. J. Magaria, J. S. Lannin. Phys. Rev. B 1985,32, 3819-3823.
[17] J:L. Guth, H. Kessler, J. M. Higel, J. M. Lambhn, J. Patarin. A. Seive~J. M.
Chezeau, R Wey, ACS Symp Ser. 1989, 3YN. 176-195. A. Kuperman, S.
Nadimi, S. Oliver, G. A Ozin, J. M. Garces, M . M. Olken. Narure 1993, 365,
239-242; J. Patarin, M. Soulard, H. Kessler. J.-L. Cuth. J. Baron. Zeolitcs
1989. Y. 397-404.
~
Experimental Procedure
Syntheses of the porosils TON, FER, and MFI were performed according t o the
litsrature [17]. A new procedure was developed for D D R : A mixture of hydrofluoric
acid, water. ammonium fluoride, I-aminoadamantane, and SiO, (Cab-osil M-5,
Fluka)in themolar ratio0.15:20.1:0.15:1 wasmaintainedat433 K for21 daysin
a Teflon-lined autoclabe. After the mixture had been cooled to room temperature,
the crystalline product was filtered off, freed from amorphous gel residues by
treatment with Zci NaOH, and washed neutral with H,O. The organic molecules
occluded inside the porosils were removed by calcination in air. For that purpose,
the porosils are heated to the final calcination temperature (DDR, TON, F E R 1123 K, MFI: 923 K)over two days. kept at this temperature for another two days
and then cooled to room temperature within one day. Insertion of iodine was
performed in the \apor phase at 433 K in Teflon-lined autoclaves. After a reaction time of four days. iodine-porosil compounds were obtained. from which
iodine desorbed above 313 K. At room temperature. they are srable for several
weeks
UV/Vis spectra in diffuse reflection were obtained on a Beckmann spectrometer
model DK-2A. Quartz powder was used as a reference and for dilution of the
samples. Raman spectra were recorded with an FT-Raman apparatus (Nicole1
FT-Raman 910); thc 1064 nm line of a Nd:YAG laser was used for excitation. For
each measurement 200 scans were accumulated; the laser power was 200 mW for the
insertion compounds. and 20 mW for bulk iodine.
Received June 3, 1996 [Z9184 IE]
German version: Angew. Chem 1996, 108, 2951 -2953
Keywords: iodine compounds - host -guest chemistry
compounds zeolite analogues
-
- silicon
A. Miiller. H Reuter. S . Dillinger, Angew. Chem. 1995, 107, 2505-2539;
Angew. Chem. I n / . Ed. Engl. 1995, 34, 2328-2361.
G. D Stucky, Prog. lnorx. Chem 1992.40.99-178;G. A. Ozin, A. Kuperman,
A. Stein, Angtw. Chem. 1989,101,373-390; Angew Chem. I n / . Ed. Engl. 1989,
28,359-376;G. A. Ozin, Adv. Mater. 1992,4,612-649; G A. Ozin,S. Ozkar,
ibid 1992. 4, 11 -22; G . A Ozin, ibid. 1994, 6, 71 -76; N. Herron, J. Inclusion
Phenom. Mol. Recognit. Chem. 199521,283-298; P. Behrens, G D. Stucky.
in Comprehensive Supramolecular Chemistrj', Vol. 7 (Eds.: G. Alberti, T. Bein),
Pergamon, Oxford, pp. 721 -772.
P. P. Edwards, L. J. Woodall, P A. Anderson, A. R. Armstrong, M. Spaski,
Chem. Sac. Rev. 1993,305-312;V. I. Srdanov, N. P Blake, D. Markgraber, H.
Metiu, G. D. Stucky, Stud. Surf. Sci. Catal. 1994, 85, 115-144.
G van de Goor, Thesis, University of Konstanz, 1995; P Behrens, G . van de
Goor, M. Wark. A. Tmoska, A. Popitsch, J. Mol. Srruct. 1995, 348. 8590.
For the classification and nomenclature of dense and microporous silicate
modifications see: F. Liebau, H., Gies, R. P. Gunawardane, B. Marler, Zeolites
1986,6. 373- 377.
M E. Davis, R. F. Lobo, Chem. Muter. 1992, 4, 756-768.
I. Petrovic, A. Navrotsky, M. E. Davis, S. I. Zones,. Chenz. Mater. 1993, 5,
1805-1813; A. Navrotsky, I. Petrovic, Y.Hu, C.-Y Chen, M. E. Davis, Micropor. Muter. 1995, 4, 95-98; N. J. Henson, A. K. Cheetham, J. D. Gale,
Chem. Marer. 1994, 6, 1647-1650.
These abbreviations conform to the guidelines for the nomenclature of zeolites
and zeolite-type materials proposed by the International Zeolite Association.
See: W. M. Meier, D. H. Olson, C. Baerlocher, Arlas ofZeolite Structure Types,
4th ed., Butterworth-Heinemann, London, 1996; W. M. Meier, D. H. Olson,
C. Baerlocher, Zeolites 1996, f7.
It should be noted that, in spite of the similarities between iodine-starch and
iodine-cyclodextrin inclusion compounds on the one hand and the iodine
insertion compound of TON on the other, the iodine species are chemical19
different: In TON, the iodine chains are made up of neutral iodine holecules,
whereas the iodine chains in iodine-starch compounds and its derivatives
always exhibit a negative charge: R C. Teitelbaum, S. L. Ruby, T. J. Marks, J
Am Chem. Soc. 1980,102,3322-3328; W. Saenger, Naturwissenschafrren 1984,
7 / , 31 -36.
A~. WM . .
Chm? In/ Ed Enzl.
1996,35,No. 23/24
C
A Noninterpenetrated Molecular Ladder with
Hydrophobic Cavities**
Pierre Losier and Michael J. Zaworotko*
Crystal engineering of supramolecular architectures sustained by coordinate covalent bonds['. 21 or hydrogen bondsL3]
represents a rapidly expanding field that offers potential for
rational development of new classes of functional solids. It is
now established that the architectures of coordination polymers
can be reliably predicted, since previously known metal coordination environments are propagated into one- (1 D), two- (2D),
and three-dimensional (3D) motifs with rigid multitopic organic
"spacer" ligands. Recent examples include d i a m ~ n d o i d ,hon~~]
eycomb,['] grid,". '. 61 ladder,[71brick
and octahedral[*]
frameworks from tetrahedral, trigonal, and octahedral metal
templates (e.g. Zn", Cd", Ag', Cu', Scheme 1). Unfortunately,
if the void created in this way is more than 50% of the crystal
by voIume, it is almost always reduced by interpenetration o r
s e l f - i n ~ l u s i o n . [ ' ~We
~ - ~report
~
herein what is to our knowledge
the first example of a noninterpenetrated molecular ladder:
[C0(N0,)~(4,4'-bpy),.,], (1) (4,4'-bpy = 4,4'-bipyridine), an
open framework infinite ladder that clathrates small organic
guests despite possessing a cavity that is large enough to selfinclude.[6]
In principle, the formation of molecular square grids"' 2.4J or
molecular ladders/brick walls['] depends on the metal-to-ligand
ratio (I :2 or 1 : 1.5, respectively). We therefore anticipated that
reaction of [Co(NO,),].6 H,O with three molar equivalents of
4,4'-bpy would afford a square grid polymeric motif.['] However, when the reaction was conducted with 1.5 or 3 molar
[*] Prof. Dr. M. J. Zaworotko, Dr. P. Losier
Department of Chemistry, Saint Mary's University
Halifax, Nova Scotia, B3H 3C3 (Canada)
Fax. Int. code +(902) 496 8106
e-mail: mike.zaworotko@stmarys.ca
I**]This work
was supported by the NSERC (Canada) and the Environmental
Science and Technology Alliance of Canada.
VCH Verlagsgesellschaft mbH. 0-69451 Weinheim, 1996
OS70-ON33/9613S23-2779 $ 15.00+ .2510
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