Interpenetrating and non-interpenetrating 3-dimensional coordination polymer frameworks from multiple building blocks

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Solid State Sciences 7 (2005) 1522–1532www.elsevier.com/locate/sssc

Interpenetrating and non-interpenetrating 3-dimensional coordinatiopolymer frameworks from multiple building blocks

Darren Bradshaw, Matthew J. Rosseinsky∗

Department of Chemistry, The University of Liverpool, Liverpool L69 7ZD, UK

Received 16 December 2004; accepted 7 April 2005

Available online 18 October 2005

Abstract

Reaction of Co(NO3)2·6H2O with the multidentate ligands benzene-1,3,5-tricarboxylate (btc) and the flexible bipyridyl ligand 1,2pyridyl)ethane (bpe) affords the 3-dimensional coordination polymers [Co3(btc)2(bpe)3(eg)2]·(guests)1, where eg= ethylene glycol, and[Co2(Hbtc)2(bpe)2]·(bpe)2. Both phases are comprised of infinite metal-carboxylate dimer chains, linked into 2-dimensional sheets byligands. These sheets are further linked to adjacent sheets through covalent interactions,1, or through hydrogen-bonding interactions,2, to yieldthe 3-dimensional structures. Phase1 exhibits solvent filled 1-dimensional pores, whereas2 is triply-interpenetrated to form a dense solid arra 2005 Elsevier SAS. All rights reserved.

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1. Introduction

The design of porous materials using the concepts ofordination chemistry is currently a very topical area[1–4]due to their applications as selective adsorbents[5], gas stor-age [6] and separation[7] media and heterogeneous calysts[8–10]. Truly microporous materials with substantial vovolumes have been prepared with high degrees of struccontrol from both multidentate carboxylate[11] and bipyridyl-type [12] ligands. In order to develop fully rational framwork design of materials with enhanced complexity it ispropriate to investigate, not only the synthesis of networkwhich both ligands connect metal centres, but also the harchical assembly of infinite units characteristic of one liga[13,14]. Although in principle this offers access to more coplicated framework topologies than can be obtained witsingle framework-forming ligand, there are considerable addifficulties in controlling and predicting the structures of tresulting materials. Our initial explorations of such cheistry with cobalt-containing frameworks derived from threconnecting benzene-1,3,5-tricarboxylate (btc) and linearnecting 1,2-bis(4-pyridyl)ethane (bpe) ligands (Scheme 1) in-

* Corresponding author.E-mail address: [email protected](M.J. Rosseinsky).

1293-2558/$ – see front matter 2005 Elsevier SAS. All rights reserved.doi:10.1016/j.solidstatesciences.2005.04.020

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-Scheme 1. Representation of the carboxylate ligands 1,3,5-benzenetricalate (btc) and isophthalate (ip), and the flexible bipyridyl ligand 1,2-bispyridyl)ethane (bpe) employed or referred to throughout this work.

dicate the extent of structural diversity that can arise. Hewe report the synthesis and structure of two 3-dimensiona

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http://dx.doi.org/10.1016/j.solidstatesciences.2005.04.020

D. Bradshaw, M.J. Rosseinsky / Solid State Sciences 7 (2005) 1522–1532 1523

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ordination polymers derived from these multidentate buildblocks, linked in differing manners that exert a strong influeon the observed topology. A significant feature is the assbly of a structure in which there are two distinct types of mecentre, differing in whether their coordination sphere is copleted exclusively by the ligands that form part of the extenframework. As coordinatively unsaturated metals are neefor catalytic activity while saturated centres are requiredstructural stability, the development of chemistry in which btypes coexist in one structure[15] is important.

2. Experimental

Cobalt(II) nitrate hexahydrate, 1,3,5-benzenetricarboxacid and 1,2-bis(4-pyridyl)ethane were used as obtainedthe Aldrich Chemical Company. The ethylene glycol amethanol solvents employed were also used as obtainedwere not purified prior to reaction.

2.1. Synthesis of 1

A stock solution of Co(NO3)2·6H2O (60 mg, 0.2 mmol)and H3btc (30 mg, 0.14 mmol) was prepared in 20 mL eylene glycol (eg). This solution was split into five 4 mportions and placed into straight glass test tubes of diater 18 mm and each portion layered with fresh eg (5 mA solution of bpe (150 mg, 0.8 mmol) was prepared5 mL of MeOH and a 1 mL portion of this layered carefuonto the eg in each of the test tubes. The tubes were sewith parafilm and left to stand undisturbed at r.t. After aproximately eight weeks, pink plate-like crystals suitableX-ray analysis had formed. Microanalysis (bulk sample), cfor [Co3(btc)2(bpe)3(eg)2]·6MeOH·6eg C76H114Co3N6O34:C 49.81; H 6.27; N 4.59%. Found: C 49.10; H 5.08;4.92%. This analysis indicates that the bulk composition dnot correspond to the crystallographically-derived comption.

2.2. Synthesis of 2

Into a stirring eg solution (10 mL) containing Co(NO3)2·6H2O (45 mg, 0.15 mmol) and H3btc (27 mg, 0.13 mmolat r.t., was added an eg solution (10 mL) of BPE (100 m0.5 mmol) dropwise over a 12 h period. The resulting pink swas removed by gravity filtration and the filtrate left to standr.t. undisturbed. After approximately one month, pink bloshaped crystals suitable for X-ray analysis had formed. Mianalysis (bulk sample), calc. for C54H48Co2N6O14: C 57.76;H 4.31; N 7.48%. Found: C, 57.38; H 4.00; N 7.45%—the adtional water molecules detected by C H N analysis of2 indicatesthat this compound is slightly hygroscopic in nature, givincompositional formula of [Co2(Hbtc)2(bpe)2]·(bpe)·2(H2O).

3. X-ray crystallography

A crystal of 1 having dimensions 0.31× 0.15× 0.04 mmwas measured at 150 K on a Bruker Smart CCD area

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tector equipped with an Oxford Cryosystems low tempeture system using Mo-Kα radiation. Of the 13842 reflectionmeasured, all of which were corrected for Lorentz andlarisation effects and for absorption by semi-empirical meods based on symmetry-equivalent and repeated reflec(minimum and maximum transmission coefficients 0.83570.9764), 9708 were independent (Rint = 0.036). The struc-ture was solved by direct methods within SHELXS97[16]and refined by full matrix least squares methods on F2 [16].Disorder of the bipyridyl ring N(3)–C(45) and the metabound eg is modelled as outlined in the CIF file. Hydgen atoms were placed geometrically and refined with aing model (including torsional freedom for methyl groupand with Uiso constrained to be 1.2 (1.5 for methyl grouptimes Ueq of the carrier atom. All non-hydrogen atoms werefined anisotropically except those in the disordered cponents whose isotropic thermal parameters were restrato be approximately equal. Non-framework electron dsity was treated by the Spek[17] method for the modellingof disordered solvent to give the following refinementdices: data/restraints/parameters= 9708/32/373,R1 = 0.0457,wR2 = 0.1232 (for 6964 data withI > 2σI ) andR1 = 0.0586,wR2 = 0.1274 for all data (indices before application of tSpek method:R1 = 0.1066 (for 7053 data withI > 2σI ) andR1 = 0.1265,wR2 = 0.3668 for all data). Minimum and maxmum final electron density−0.672 and 0.953 e·Å−3. A weight-ing schemew = 1/[σ 2(F 2

o ) + (0.0738P)2 + 0.00P ], whereP = (F 2

o + 2F 2c )/3, was used in the latter stages of refin

ment.A crystal of 2 with dimensions 0.08 × 0.06 × 0.06 mm

was measured at 150 K, with Synchrotron radiation of walength 0.6900 Å at station 9.8 of the SRS at Daresbury Loratories using an AXS Smart CCD area diffractometer a

Table 1Crystal data and refinement summary for [Co3(btc)2(bpe)3(eg)2]·(guests)1 and[Co2(Hbtc)2(bpe)2]·(bpe),2

1 2

Formula C19.33H16.67CoN2O5.33 C27H22CoN3O6Formula weight 421.28 543.41Crystal system Triclinic TriclinicSpace group P-1 P-1a (Å) 10.0196(7) 10.1025(9)b (Å) 13.5634(10) 11.1759(9)c (Å) 17.5811(13) 12.5105(11)α (deg) 71.9680(10) 100.479(2)β(deg) 83.6250(10) 113.461(2)γ (deg) 78.8330(10) 102.562(2)V (Å3) 2225.6(3) 1206.25(2)Z 3 2Dcalcd (g/cm3) 0.943 1.496T (K) 150 150λ (Å) 0.71073 0.6900µ (cm−1) 0.601 0.761R1 (I > 2σ(I))a 0.0457 0.0468wR2 (I > 2σ(I))b 0.1232 0.1166

a R1 = ∑‖Fo| − |Fc‖/∑ |Fo|.b wR2 = |∑w(|Fo|2 − (|Fc|2)|/∑ |w(Fo)2|1/2, wherew = 1/[σ2(F2

o ) +(aP )2 + bP ]. P = (F2

o + 2F2c )/3.

1524 D. Bradshaw, M.J. Rosseinsky / Solid State Sciences 7 (2005) 1522–1532

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equipped with an Oxford Cryostream low temperature stem. Of the 12 111 reflections measured, all of which wcorrected for both beam decay and absorption using a sempirical method based on equivalents (minimum and mmum transmission coefficients 0.9417 and 0.9588), 6541 windependent (Rint = 0.0466). The structure was solved arefined as for1 above. The non-coordinated bpe ligand wfound to be disordered, and was modelled as outlined inaccompanying CIF file. All non-hydrogen atoms werefined anisotropically, and hydrogen atoms were placedmetrically and refined with a riding model (including to

-

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-

sional freedom for methyl groups) and withUiso constrainedto be 1.2 (1.5 for methyl groups) timeUeq of the carrieratom. Structural refinement converged with the followingfinement indices: data/restraints/parameters= 6541/177/398,R1 = 0.0468,wR2 = 0.1166 (for 5463 data withI > 2σI ) andR1 = 0.0570,wR2 = 0.1224 for all data. Minimum and maxmum final electron density−0.439 and 0.574 e·Å−3. A weight-ing schemew = 1/[σ 2(F 2

o ) + (0.0693P)2 + 0.00P ], whereP = (F 2

o + 2F 2c )/3, was used in the latter stages of refin

ment. Detailed data collection and refinement parameterboth phases are summarised inTable 1.

lity

(a)

(b)

Fig. 1. Ortep plots of the co-ordination environment about the Co(II) centres in (a) phase1 and (b) phase2. Thermal ellipsoids are drawn at the 40% probabilevel, and all non-hydrogen atoms and non metal-bound species are omitted for clarity. Symmetry operation for atoms labelled ‘_2’= −x,−y,−z.


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4. Results and discussion

Reaction of cobalt(II) nitrate hexahydrate with 1,3,5-benztricarboxylic acid (H3btc) and 1,2-bis(4-pyridyl)ethane (bpin ethylene glycol (eg) affords the 3-dimensional coordinatpolymers1 and 2, in which infinite metal carboxylate chainpillared into sheets by flexible bipyridyl ligands, are furthlinked to adjacent sheets in chemically very distinct mannthat produce pronounced differences between the structThis is immediately apparent in the Co(II) co-ordination evironments based on the asymmetric units shown inFig. 1,

e

ss.

where 1 contains a second structurally distinct metal cenwhich plays a key role in the assembly of the structure. Bphases were prepared at ambient temperature from dilutlutions of the reagents: these solutions were allowed to slodiffuse for the preparation of1, and were more rapidly mixefor the preparation of2. This small difference in experimental procedure may, in part, account for the two very differstructures obtained.

The three-dimensional compounds1 and 2 have the samebasic two-dimensional structural unit. This layer is built-from rigid one-dimensional chains of octahedrally coordina

o

(a)

(b)

Fig. 2. (a) 1-dimensional cobalt-carboxylate dimer chains are the basic building block of both structures1 and2, illustrated here by phase2. The 1-D Co-carboxylatedimer chains in1 and2 are pillared by axially co-ordinated bpe ligands into 2-dimensional dimer-sheets, (b) and (c) respectively. In1 the bpe pillars are oriented tpreclude access through the sheet (b), whereas in2 the pillars are more favourably oriented resulting in large windows through the 2-D sheet (c).


(c)

Fig. 2. Continued.

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Co(II) dimers, which constitute the backbone of the framworks (Fig. 2(a)). These chains themselves are held togeby bidentate-chelating and bidentate-bridging btc carboxylmetal interactions and are reminiscent of the [Ni2(ip)2]n chainin the recently reported 2-dimensional framework mate[Ni(ip)(4,4′-bipy)], 3 [18], where ip= isophthalate (Scheme 1).The Co cations within these dimers in1 and 2 are coor-dinated by two axial bipyridyl and three equatorial btc aions (Fig. 1) in a severely distorted octahedral environmewhich is reflected in the deviation of thetrans octahedral angles from ideal geometry [Phase1: O(6)–Co(1)–O(1), O(2)–Co(1)–O(5), N(1)–Co(1)–N(2); Phase2: O(5)–Co(1)–O(3),O(4)–Co(1)–O(6), N(1)–Co(1)–N(2)] (Fig. 1, Table 2). Coor-dination in the equatorial plane is also very distorted duethe chelating carboxylate interaction. The bite angle ofbtc carboxylate chelates are 60.27(6)◦ [O(1)–Co(1)–O(2)] and60.08(6)◦ [O(5)–Co(1)–O(6)] for1 and2, respectively, whichare narrower than the 60.9(1)◦ reported for the related mateial Co3(btc)2·12H2O [19]. The opposite angles, describedthe two bridging btc carboxylate oxygens and the metal ctre, are 105.91(6)◦ [O(5)–Co(1)–O(6)] for1 and 107.95(6)◦[O(3)–Co(1)–O(4)] for2 which further illustrate the distortioin the equatorial plane. The Co–O bond lengths for the cheinteractions are 2.209(2) and 2.148(2) Å for1, and 2.275(3)and 2.117(2) Å for2. The asymmetric chelating Co–O inteactions in1 and2 are much longer than the average 2.033observed for the bidentate-bridged Co–O bonds. The distabetween the centroids of the dimer units along the chains10.02 and 10.10 Å for1 and2 respectively, which are slightlshorter than that observed in3. The intermetallic separatio

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Table 2Selected bond lengths (Å) and angles (◦) about the Co centres in1 and2

1 2

Co(1)–O(1) 2.209(2) Co(1)–O(3) 2.039(2)

Co(1)–O(2) 2.148(2) Co(1)–O(4) 2.034(2)

Co(1)–O(5) 2.037(2) Co(1)–O(5) 2.117(2)

Co(1)–O(6) 2.019(2) Co(1)–O(6) 2.275(3)

Co(1)–N(1) 2.156(2) Co(1)–N(1) 2.141(5)

Co(1)–N(2) 2.142(2) Co(1)–N(2) 2.136(5)

Co(2)–O(3) 2.076(3) O(4)–Co(1)–O(6) 149.17(6)

Co(2)–O(7) 2.106(2) O(5)–Co(1)–O(3) 162.31(7)

Co(2)–N(3) 2.139(3) O(4)–Co(1)–O(3) 107.95(6)

Co(2)–O(3a) 2.076(3) O(5)–Co(1)–O(6) 60.08(6)

Co(2)–O(7a) 2.106(2) N(1)–Co(1)–N(2) 171.80(6)

Co(2)–N(3a) 2.139(3)

O(1)–Co(1)–O(2) 60.27(6)

O(5)–Co(1)–O(6) 105.91(6)

O(1)–Co(1)–O(6) 161.80(6)

O(2)–Co(1)–O(5) 151.32(6)

N(1)–Co(1)–N(2) 173.11(8)

O(7)–Co(2)–O(7a) 179.99(7)

O(3)–Co(2)–O(3a) 180.00(7)

O(3)–Co(2)–O(7) 89.06(7)

N(3)–Co(2)–N(3a) 180.00(9)

a Symmetry equivalent atoms 2− x,1− y,−z.

across the eight-membered dimeric units is 4.468 Å in1 and4.437 Å in2.

The 1-dimensional dimer chains in1 and2 are pillared into2-dimensional grid-like sheets through axial coordinationeach Co(II) centre to the bpe ligands (Fig. 2(b), (c)). Simi-lar rectangular grid coordination is observed in3 where axialµ-4,4′-bipy ligands link the infinite [Ni2(ip)2]n chains into a


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2-dimensional neutral framework. In1 and2 the Co–N bondlengths average 2.143 Å, and in both phases the pyridyl rare trans across the central bpe bond with torsion angles173.4◦ and 168.5◦ for 1 and 2 respectively. The planes othe two pyridyl rings of the bpe pillars are rotated by 120◦in 1 and 123.2◦ in 2. The bpe ligands orient themselvesform weak edge-face contacts with their nearest bpe nebours. Inter-pillar separation is not uniform, but close witdimeric units and distant between dimeric units: typically,closest intra-dimer bpe distances in1 and2 are around 0.2 Ålarger than that calculated from the van der Waals radiiphase1 the closest inter-dimer bpe contacts along the chainat 0.6 Å, only slightly larger than the intra-dimer distancesno accessible windows are formed alongc, perpendicular to thechain-stacking direction,b (Fig. 2(b)). In phase2, however, theinter-dimer pillar interactions between the bpe aromatic riare more favourably oriented, resulting in considerably laapertures than in1, such that the bpe pillars describe open w

sf

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sr

dows of width 3.5 Å and height 10.2 Å, based on vanWaals radii, perpendicular to the dimer-chain stacking dirtion. (Fig. 2(c)).

The btc ligands employed in the preparation of1 and2 aretrigonal directors, and thus have carboxylate functions thanot involved in the formation of the dimer chains. Theseditional btc carboxylate groups extend away from the dimchains on either side (Fig. 2(a)) and are deprotonated in1and protonated in2. This is reflected in the C–O bond lengtof these non-dimer forming carboxylates, which are 1.251[C(47)–O(6)] and 1.256(2) Å [C(47)–O(5)] in1 and 1.208(4)[C(7)–O(1)] and 1.316(4) Å [C(7)–O(2)] in2 to give, re-spectively, an anionic and a neutral dimer sheet. These ftional groups are thus available to complete the observed thdimensional structure of the materials.

In phase1 the deprotonated carboxylates from adjacdimer-sheets bind to a second set of octahedral metaltres, Co(2) (Fig. 3(a)). The coordination at these sites co

ensional

fo

(a)

Fig. 3. (a) The dimer-sheets in1 are covalently cross-linked along 001 through monodentate carboxylate interactions to further Co(II) centres. (b) The 1-dimchannels (along 100) generated by this cross-linking represented by their van der Waals surfaces. The axially co-ordinated bpe pillars associated with the dimer-sheetsare represented by the blue surfaces, and those with the Co(2) sites by the orange surfaces. The bpe pillars bound to the Co(2) sites run between thosermed by thedimer-sheets and thus reduce the window diameters that provide access to the porosity.


(b)

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sists of trans monodentate carboxylates and two eg solvmolecules in the equatorial plane, with two axial bpeands completing the coordination at this second Co siteis striking that this site, unlike Co(1), has a labile coordition sphere as it is not exclusively completed by framewoforming ligands. The Co(2)–Obtc bond lengths are 2.076(2)and lie between those distances observed for the bidechelating and bidentate bridging interactions at Co(1).Co(2)–Oeg bond lengths are, at 2.106(2) Å, slightly longthan the Co(2)–Obtc distances. The organisation of the band the solvent molecules in the equatorial plane is enfoby the strong hydrogen bonds between the btc monodecarboxylate oxygen, O(4), and the eg hydroxyl, O(7), whthe O–H· · ·O distance is 2.63 Å. This precludes accessany channels parallel to the chain-stacking direction,b, whichmay arise from this cross-linking of dimer-sheets (Fig. 3(a)).Flexible bpe ligands axially coordinate to Co(2), with siilar Co–N bond lengths to the dimer-chain pillars, andfound to be disordered over two sites with occupancies79.0:21.0%. The bpe ligands pillar the labile linking metal c

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tres with an identical separation to that observed withindimer-sheets. Covalent cross-linking of the metal-carboxydimer sheets in1 by the Co(2) sites generates 1-dimensiochannels alonga with window dimensions 11.0 × 12.2 Å.These apertures are reduced by approximately half alongc-direction by the bpe pillars bound to the bridging Co(2) sto give an actual window size of 5.5× 12.2 Å. The total extra-framework volume in phase1, determined by summing voxemore than 1.2 Å from the framework using the program PLTON [17] is 48%. The solvent occupying this space is crtallographically ill-defined, however, removal of the resid(non-framework) electron density from the refined structufollowed by treatment of the data with the SQUEEZE[17]routine, suggests a cavity electron population of 99.3 e− performula unit, consistent with two eg and two MeOH mocules (100 e−) per Co centre, giving a compositional fomula for 1 of [Co3(btc)2(bpe)3(eg)2]·6MeOH·6eg. This con-curs with TGA and outgas data where heating to 100◦C, orevacuating at ambient temperature under high vacuum rein the loss of 38% of the mass of1, consistent with the los


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of guests and metal-bound eg (calculated 37.6%), to affocrystalline phase which is not isostructural with1 (Figs. S1and S2, Supporting Information). The purple desolvated phprepared by outgassing1 at room temperature is non-poroto N2 at 77 K. However ethanol vapour can be taken up298 K to fill 54% of the calculated solvent accessible volu(from PLATON) atp/p0 = 0.9. The ethanol sorption isotherdisplays a gate pressure[5] required to give guest accessp/p0 = 0.3 on the adsorption leg and marked hysteresis udesorption (Fig. S3, Supporting Information), which is constent with a structural change or re-arrangement driven byguest. However, as microanalysis and powder diffraction(Supporting Information) clearly indicate that as-made1 is notwholly phase pure, phases other than1 may be contributingto this bulk sorption behaviour, and further investigationsneeded.

In phase2 the two-dimensional dimer sheets illustratin Fig. 2(c) are retained as the basic structural unit ofsolid. In this case, however, they are connected throughdrogen bonding interactions between the third btc functiona(a protonated carboxylate), and the nitrogen from a bpeand not involved in metal coordination. The non-coordinabpe species are disordered over two sites with occupan

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of 79.4:20.6%; the pyridyl rings of the free bpe speciestrans across the central ethane bond and are virtually conar. The hydrogen-bonding interactions to the protonatedcarboxylates are strong with O–H· · ·N distances of 2.62 ÅAs a result of these hydrogen-bonding interactions, andfavourable orientations of the bpe ligands that pillar the inite dimer chains, large 3-dimensional channels run throuout the structure. (Fig. 4) The windows offering access to thchannels defined by the hydrogen-bonded bpe ligands in2 are19.4× 7.7 and 16.4× 5.6 Å based on van der Waals radii. Thlarge open pore structure in2 allows interpenetration of threof these networks, to form a dense solid array with no solvaccessible volume (Fig. 5(a)) [17]. Interpenetration is not seein 1 due to the further pillaring of the linking groups (labiCo(2) centres) and the unfavourable inter-dimer bpe orietions alongc, which restrict the dimensions of the windowthat give access to the void volume. The three networks2are related by a translation along the crystallographicb-axis,where the centroids of the btc rings either side of the dichain in one network are aligned with the protonated btcboxylate Caromatic–Ccarboxylatebonds of the other two networkat a distance of 4.324(10) Å. This arrangement is such thaeach network, the btc rings on one side of each dimer-s

oieties.
Fig. 4. The open pore structure of a single network in2 resulting from the cross-linking of dimer-sheets through hydrogen-bonding interactions to free bpe mThe disordered components of the non-metal bound bpe species are not shown, and the yellow dashed lines represent strong hydrogen bonds.


e space.

rk, bu

(a)

Fig. 5. (a) Interpenetration of the three networks in2 shown as wire and space-filling representations; in this material there is no solvent accessible por(b) In 2 the centroids of the btc rings either side of the dimer chain in one network are aligned with the protonated btc carboxylate Caromatic–Ccarboxylatebonds ofthe other two networks, such that the btc rings on one side of each dimer-sheet are above the carboxylate bonds of the dimer-sheet in the next netwot thoseopposite are below the corresponding interactions of the previous network.

nentenheichrve

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are above the carboxylate bonds of the dimer-sheet in thenetwork, but those opposite are below the corresponding iactions of the previous network (Fig. 5(b)). Each dimer sheet ia given network is then hydrogen-bonded to an adjacent swithin that network by the non-coordinated bpe ligands, whpass through the other two networks to complete the obseinterpenetration.

The combination of two framework-forming ligands prduces structural diversity that, in this case, arises from thetential for hydrogen-bonding interactions between the ligawhen neither is coordinated to a metal centre[20]. This allowsthe bpe ligand to form the network observed in2 by coordi-

xtr-

et

d

-s

nation to Co and hydrogen bonding to btc. Despite this pnounced difference between the structures, the building uin the two phases are very similar, being two-dimensiosheets whose construction involves both framework-formligands.1 is particularly notable, in that it contains Co cetres that are either intrinsic to the framework—the coordinasphere is completed exclusively by ligands that form thetended structure—or potentially labile, as coordination involnon-framework forming eg solvent ligands. The presencethese distinct metal centres in a three-dimensional netwstructure indicates that frameworks consisting of dissimilarands and metals can generate structures in which metals


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qualitatively different roles, offering an opportunity for sitselective substitution to generate multi-metallic site-ordeframeworks.

All crystallographic data has been deposited with the Cbridge Crystallographic Data Centre in CIF format as supmentary material numbers CCDC-257851 and CCDC-257for 1 and 2, respectively. Copies of the data can be obtaifree of charge on application to CCDC, 12 Union RoCambridge CB2 1EZ, UK (fax: (+44)1223-336-033; [email protected]).

Acknowledgements

We thank the EPSRC for support under GR/N08537J.F. Bickley for single crystal and powder X-ray data collecton phase1, and S.J. Teat of the SRS at the CLRC DaresbLaboratories for single crystal data collection on phase2.

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Documents

Interpenetrating and non-interpenetrating 3-dimensional coordination polymer frameworks from multiple building blocks