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Designed Assemblies in Open Framework Materials Synthesis An Interrupted Sodalite and An Expanded Sodalite.

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[HKh(FII,j,(lII'O,H)] inwrmetliate which has been characterized in path B
:ind which I I C \ ii further 5 7 kcalmol-' lower in energy [7a].
(251 .A wnilrir coiicIusion liiis been obtained for the formation o f t h c 0 5 ixmier ot
lhr: Ioriiiic
;icid
[7n]
(261 i i ) I. H o s o k a u x . S. I.Mui-nhashi. A C T Clirni. K I Y . 1990. 23. 49: b) A M. Joahi.
H. K J;iinc\. O i , ~ ~ / i i ~ / i i r t a /19YO.
/ i i ~ . sY. 199: c) L. Versluis, T. Ziegler. ihid. 1990.
9. 20x5. d) I<. H Morris. lnnrfi. C k i i . 1992. 31. 1471.
. S Bhandari. P. R. Rahlen. J. A m . C ' l i i w Soc. 1994. 116. 1839.
Y . A. M Mehel. K . Morokuma. J. A m . C%1~11. So.. 1994. 116.
1I W J 3
iL
C'Il(W?l. IYX2. Y4. 781, Arl,~L,ll. ChPIIl. In/. Ed. h f i l .
[2Yj a ) I< t l ~ l l l l ~ i ~ l l lAl/i'<,li.
1YX2. ? / , 71 I : h ) 'r. A. Alhright, J. K Burdett. M H. Whangbo. Orhirul Iritcrf i ( ' i i i i i i $ oi C i i c w i . s t ~ - i - .Wile!.
Kew York. 1985, pp. 352--35h.
Designed Assemblies in Open Framework
Materials Synthesis: An Interrupted Sodalite
and An Expanded Sodalite**
Pingyun Fcng, Xianhui Bu, and Galen D. Stucky*
A number of new framework materials based on zinc-oxygen
and phosphorus-oxygen tetrahedra have recently been characterized!" 21 some of which are structural analogs of natural
zeo1ites.I" These include zeolite X and h y d r o - ~ o d a l i t ewhose
[~~
structures werc established by Rietveld refinement of X-ray
powder data. The synthesis of solids with zinc phosphate open
frameworks can be carried out from -20 'C (zeolite X) to
200 C.I2' This composition also pushes the limits with respect to
the ionic radii of the tetrahedrally surrounded atoms (T atoms)
of materials with open frameworks; Zn" (0.60 A) is the largest
for ;I pure (TO;'. T'OY-) phase zeolite and P5* (0.17 A) is one
of the smallest ions.[41
One important aspect in the synthesis of framework materials
is thc mechanism by which the inorganic framework is assembled by the templating molecule. The piperazine molecule has a
number of features which can be used for such a study. The
recent studies on the trioxane-templated silica ~ o d a l i t e [sug~]
gest thxt the molecular dimension of the similarly sized piperazine molecule is ideal for organization of four-ring units into a
cage configuration. The directed hydrogen bonding should also
iinpoac at Icaat one symmetry operation of the molecule on the
framework. that is. the crystallographic site symmetry should be
a subgroup of the molecular point group symmetry. This is
distinct froin dynamic templating in which the inorganic condensation is around a spatially averaged distribution of the orga nic molecules.
In this study. we were interested in those cases in which the
symmetry of host frameworks i s determined by nonframework
template
A complication occurs for sodalite structures when the templating molecules are not only ordered but
also hxve a charge less than +3, as required to balance the
charge of a sodalite cage with ( T 3 + / T 4 + )or (T2+:T5+)
composition. We describe here two mechanisms by which the negative
charge of the framework is lowered to match that of guest molecules while preserving the sodalite type cage linking: cage interruption and expansion as discovered in two newly synthesized
[*] Prof. D r G L). Stucky. P. Feng. D r X. Bu
C'Iieini\lry 1)eparttneiit. University ol'California d t Santa Bai bara
Santn U:irhal-a. C A 93106 (USA)
1cIet':i~~l r i f code (805]893-4120
e - m a i l : \tuck y o shxray.tic5h.edu
+
[**I Ihi\ rcsciircli
was supported
( i r a i i l I ) M K 93-08511
in
part by the National Science Foundation under
zincophosphates. The cage interruption mechaniam involves the
removal of a tetrahedrally coordinated atom from the sodalite
cage which reduces the negative charge froin - 3 to - 1 per cage.
The cage expansion mechanism involves the insertion of tetrahedral atom groups into the sodalite cage, which reduces the
cage charge from - 3 to -2 per cage. In both cases, the symmetry of template molecules (inversion center and twofold axis of
piperazine molecule, respectively) plays a structure-directing
role i n the formation of the new cage assemblies.
Crystals of ZnPOiPPZ' (zincophosphate with a monoprotonated piperazine) were grown by "nonaqueous" synthesis from
a mixture of Zn(N0,)2 6 H,O. H,PO,, ethylene glycol, and
piperazine. The molar ratio of the corresponding precursor oxides (ZnO and P20,), piperazine, and ethylene glycol was
1.0:0.96:0.91 : 2 5 . The gel was stirred at room temperature for
about 30 minutes. The mixture was heated at 17O'"C for four
days in a teflon-coated steel autoclave. The product was recovered by filtration and washed with deioniad water. Clear
needlelike crystals of typical dimensions 0.3 x 0.1 x 0.2 mm3
were obtained, which were suitable for an X-ray structure analysis (Fig. 1 a).
?(la!
cl
Fig 1 . Crystal structures of a ) ZnPO.'PPZ+ and b) ZnPOsPI'L' ' : ORTEP views of
zinc and phosphorus tetrahedra. A t o m labels having "a" mii "b" refer to syinmetry
generated atoms.
Crystals of ZnPO/PPZ2 (zincophosphate bvith a diprotonated piperazine) were grown from a mixture of Zn(NO,), . 6 H 2 0 ,
H,PO,, H,O, and piperazine. The molar ratio of the corresponding precursor oxides (ZnO and P20,). piperazine, and
water was 1.0:0.95:0.89:85.A white gel was formed at an approximate pH of 3 after stirring the mixture for about
15 minutes. The mixture was heated at 170 ' C' for four days i n
a teflon-coated steel autoclave. The product was recovered by
filtration and washed with deionized water. Clear platelike crystals of typical dimensions 0.20 x 0.17 x 0.03 mm3 were obtained.
which were suitable for an X-ray structure analysis (Fig. 1 b ) .
+
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ZnPO PPZ' has an interrupted sodalite-type structure which
obtained by removal of a T dtom ( Z n z +in this c'ise) from sites
ielated by one of the three twofold axes through opposing fourlings of the normal sodalite c'ige structure (Fig 2a and 3 '1) One
piperazine molecule per cage. whethei mono- or diprotonated.
is unable to provide the three positive charges which are needed
to balance the negatively charged framework of dn uninterrupted zincophosphate sodalite structure The charge compensation
is achieved instead by removal of one lower charged T atom
(Zn") for every six T atoms, and the addition of four piotons,
which form hydi-oxyl groups with oxygen atoms f o r a net charge
gain of + 2 per cage The remaining - 1 charge on the edge is
b'ilanced by one monoprotonated piperazine molecule loc'itcd
at the center of the cage
ZnPO PPZ2+ has an expanded sodalite structure with eight
eight-rings instead of six-rings (Figs. 2c and 3 b) The structural
relationship between the expanded sodalite and the normal sodalite is described below Starting with a normal zincophosphate ~ o d n l i t e ' ~edge
]
([Zn,,P,z0,,]'2~). oriented such that
is
there die four four-rings on the equatorial plane, one four-ring
'ihove and one four-ring below (Fig 2 b), a hypothetical exp'inded structure can be derived by rotation of the top and
boltom four-rings by 90 followed by iiiaertion of four
ZnO(H,O), units and four PO(OH)Z units into eight T-0-T
connections between the four equatorial four-rings and two
four-rings above m d below This gives a stoichiometry of
[Zii,2P,20,,]'2[Zn,P,O,(H,O),(OH),]jt
which is identical
to the observed one. but with two water molecules coordinated
to e x h of the foui inserted zinc atoms and two OH groups
coordin'ited to each of the inserted four P atoms In the actual
stiucture (Fig 2c) one of the two w'iter molecules on each 7inc
and one of the two OH groups o n e d i phosphorus i n the 'ibove
hypothetical structure are distributed onto zinc m d phosphorus
,itoms 'icross the eight-rings This gives rise to the sodalite-type
cage liiik'ige with elongated cages s h m n g single four-rings or
single eight-rings (Fig 3 b) The reduction of the negative charge
froin - 3 for 'I normal sodalite cage to -2 for an expanded cage
is achieved with the introduction of one PO(0H): unit per cage
The unit cell volume of ZnPO PPZ'
is 1403 8(7) A' which is slightly more
than twiFe the cell volume of
688 01(3) A 3 for the normal zincophosphate sodalite 13] This is consistent with
four interrupted ccigesper unit cell The
volume increclae per cage over the normal sodalite is only 2 0 % which suggests
that the dimension of the template molecule is ideally suited for such a four-ring
'issembly In contrast. the volume increase per cage is as large as 53 7 % for
ZnPO PPZ2+ due to the cage elongdtion This extrn \pace inside the cage is
t
Zn
c
ep
a3
@?
9
(*
O&
I/
C
(4
(b)
(4
t i g 1 d) The intcirupted \od,ilite ~ i g ~e i t l the
i
rempl i t e moleculc loc,itcd oii the i i i ~ c r \ ~ ocentcr
ii
.it the L I ~ L
C e n t u hi the iiorindl ,iluinino\ilic~itc~od,iliteu g e c ) the cxpmdctl wd'ilite cdpc wilh the pipet L i ~ i ~ i dic,itwn
~u~ii
m d w'ttet iiioIc~uIco n the tuotold < i u
dround the lnverslon center on Which
I ig i I l l u w . i t i o n 01 the frmieuol k \ I I L I L ~ U I L m d soddite tqpc cdgc Iink'tge
Foui inteitupted sod.il~tec ~ g e siliriiitig vngle I O U I i l ne\ there x c 110 h i \ 11ng\
due 10 the T litotii teiiimdl h) f o u i eupmded \od,ilite L,ige\ >hztitiigsuiglc lour
chair conform'ition of the piperazine molecule h a e n point
symmetry of 2 171 with three individual syniinetry elements ( I , 2,
m ) , the template molecule therefore imposes its individual symmetry constraint oilto both types of frdineuork structures In
the expmded cage, the symmetry mntch I F 'ichieved between the
fr'imework 'ind two different template molecules, piperazine
and w'itei
In both structures. the symmetry information of the teinpl'ite
molecule is passed onto the framework mainly through guest fr'iinework hydrogen bonding a s illustiated in Figure 4 In ZnPO PPZ', the extra proton in the piperazinium monocation is
statisticdly distributed on two nitrogen sites Each template
0 bond to one of four
nitrogen 'itom forms 'it least one N - H
four-rings and inay h a w another N - H
0 bond depending
on whether the extra pioton i s located on it (Fig 4 a ) This
observ'itioii is in contrdst with the results with trioxane silica
soddite i n which the guest framework hydrogen bonding
mny only involve the weak C -H 0 interactions due to the
Lick of OH groups m d the trioxane molecule is orieiit'itionallq
disordeied lo preserve the cubic 5yi11inetr> Of the
I Ill$?\
cage ''1
t
'
(4
'I)
6
* *
(b)
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(4
(b)
In ZnPO 'PPZ". one bridging oxygen atom from each of the
four equatorial foul--rings forms the N-H . 0 type bonding to
each of the hydrogen atoms on NH, groups of piperazine molecules (Fig 3 b and 4 c ) . All four participating oxygen atoms are
on the same side of the four four-ring cluster due to the symmetry constraint imposed by a twofold axis. This is different from
ZnPWPPZ where four participating oxygen atoms are divided
on the two sides of the cluster formed from four four-rings, an
arrangcmenl consistent with the center of inversion. The hydrogen bonding between Zn(H,O) groups and extra-framework
H Z O molecules gives OH, tetrahedra (Fig. 4c).
As shown in Figure 4, the molecular dimension of the piperazine inoleculc and the 90' ,'I80 distribution of hydrogen atoms
on the t i 4 0 nitrogen atoms make piperazine ii perfect molecule
for the orgunimtion of four four-ring units. In ZnPOiPPZ',
thcsc I'our Ihur-rings units share single four-rings to form layers
that arc interconnected into the three-dimensional sodalite type
framework by bridging bidentate -O-P(OH),-O- groups
(Fig. 3 a ) . Similar layers are also found in ZnP0:'PPZ' '
(Fig. -3 b ) ,
Both structures contain interruptions between tetrahedrally
suri-ounded atoms. Due to the charge difference of the piperiizinc molecules in the two structures as well ;IS the inclusion of
a water inolecule in the expanded structure, the style of interruption i s different. leading to two unique novel cages assemblies.
However. the) are similar to each other in that the cages are
interlinked in a manner analogous to that of sodalite. The interruption of the framework structure is one of the key structural
featurcs for se\eral zincophosphates"' as well as aluminophosphates.lHl I n the cases discussed herein it helps to reduce the
negativc charge on the framework.
The xynimetry matching between the inorganic host and template molecules are not limited to purely tetrahedral zincophostcms ;IS described above. Recently. we discovered a
new piperaline-teinplated vanadium(rv) phosphate (space
group: C ' I I I ) in which the syinnietry of the tetrahedral-octahedral framework is determined by the mirror- symmetry of the
tcmplate nioleculc.~ylIn this structure both two-centered and
three-centered hydrogen bonds are used to direct the assembly
of the vanadiiim(rv) phosphate into an extended array.
I n concluhion, we have demonstrated that all three individual
symmetry elements of a piperazine molecule can direct framework liirination and that partial zeolite-like cage structures can
be 5 ) nthcsirod by using a template design strategy. The results
are important for the elucidation of the synthesis mechanism of
sodnlite-hoscd zeolite inaterials in general and indicate that in
future i t may be possible to derive a strategy for the design of
new I'rmneuork structures as well as modification of existing
types utilizing template symmetry, charge matching. and directed hqdrogcti bonding between guest and host. This strategy
Fig. 4. Gucst-fi-;ime\bork hqdi-ogen bonding. :I) ZnPO:
P P l t . monoprotonated piper:irinium s l i o u i i 'is di-pimtoiiated due to its s l a t i s t i c i i l dictrihution o n llic t w o sites:
h) ZnPO:PPZZ +.top view of thc four qu,itorial four-rings
showing host. guest hqdrogcn bond\ hetwccn pipcrarine
N H , groups and framewnrk cxy:cii iitoiiii: c ) LnPO
PPZ' ' . side view of the four cquatoriiil four-rings shouing
host euest hvdroren bonds be1uccn exirr,i-l'rameaork
H 2 0 and H,O o n Zn tetrahedra iii tlic Inner portion oftlie
cage.
(c)
should apply to both interrupted and noninterrupted zeolitic
systems since the directed hydrogen bonds described above are
between the bridging framework oxygen atoms and piperazine
molecules.
Rccci\cd: N w c i n b e r 3. 1994
Re\,ised version' March 17. 1995 [Z 7451 IE]
German version .Aii,yeii. U7ciii. 1995. 1/17. 1911 1911
~
Keywords: hydrogen bonding . sodalites . solid-state structures
. template syntheses . zeolites
[IJ R. H. Jones. J. Chen. G. Sanknr, J M . Thomas i n %rw/ii(,r id R[~/rii(~r/.I.li(~ni/i1. Weitkaiiip. H. ti. K x y r . H. l'lbifcr. ',V. Holdei-ich).
Elsevier. Amsterdam. 1994. p. 2229.
[2] T. E. Gier. G. D. Stuck>. ,Voitiir.c ( / , o i i r / o i i ) 1991. 349. i i l X .
131 T. M Nenoff, W. T. A. Harrison. T. E . Gier. Ci D Stuchy. .I .AIII. ( ' / i o i i . S o ( .
1991. il.7. 37x.
131 T M Nenol'f. W. T. A. Harrison. T.E . Gier. N . L Keder. C. M. Z,ireinhii. V 1.
Srdano\.. J. M . Nicol. G. D. Srucky. Inor-c.. C ' / W I > . 19Y4. 33. 2472.
[5] K.Futterer. h' Depmeier, F;. Altorfcr. P. Behren5. 1. t.clschc. Z. hr.,i/ri//o,q,-.
1994. 2OY. 517.
[(I] W Depmcier. Z. Ar.i\/d/o-c.r.. 1992. i Y 9 . 75.
[7] W.T. A. Harrison. T. E. Martin. T. E Gier. G D. SttiLkb. .I ,Mnrt.r.. C ' / i w i i .
1992. 2. 175.
0 Huo. R. Xu. S
Li, Z. Md. J. M . Thomas. I<. H. .lono. ,A M.Chippindale.
J. C,/icin. S I X . C/7<vil.Coiiiniiit!. 1992. 875.
[Y] X. Ru. P. Fens. G . D. Stucky. .I C / ~ ( WSo(.
? . < ' / i u i i , ~ ' ~ J I ~ I I I ~ uin/ I .press.
.
[S]
[lo] a) Crkstal data for ZnPO PPZ': [ Z I ~ , ( P ~ , ] ( H ~ P O , J ~ ] ( C , H , N ? H,\I, ) .=
306.9. space group C2:<,. [I = 13.370(41. /I = 12.X3i4). 1 = 8.20713) A,
- 94.79(1) . I ' = 1402.8(7) A'. I = 4. J I ~ , , , ~ ,=
, 7.40 gciii I . cnlorless needle.
tal si7e0.2X x 0.10 x 0.07 mill3. Mo,,. j . = 0 71071 .A
ciil 'ibwrption cnrrection. lilln= 0.56. I,,,,l, = 0.SO. 1
11 R = 0.061 for 11s parameters and 1587 iiniqiic retlcc
h ) ('rystiil d i i t d for ZnP0:PPZ" : [Zii(HLO)Zii(PO,)(HPO,)], (H,O)
(C,H,N,H,).- LI =785.61. space proup C : c . ( I = l2.!l93(7j. /J = 14.X97(8).
< = ll.X49(6)A./j = 97.821(3). i = 2115i21 A'./ = 4.1'. ,,.,,= ?..ihXgcm-'.
colorle\\ plate. crystal m e 0.20 x 0.17 x 0.0.3 inin'. \lok,. I = 0.71073 A.
11 = 4.99 n n n - ' . einpirical ;ibsorption corrcctioii, I;,,,,, = 0
(I,,,,,< = 60 . R = 0.049. I I R = 0.00 for I91 parainctct-s ;iiid 24
tinns with I > 3 u(/).c i Further details ofthe crystal striicturc investigation are
;i\ailabls on request l'rom tlir Dii-ector of the C;iinbridge
Data Centei-. I ? L ' i i i o n Road. GB-Cxmbridge CtlZ 1 EL ! i J K ) . 011 qiiotiiig the
toll journal cit'itinn.
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framework, synthesis, open, expanded, sodalite, designer, material, interrupt, assemblies
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