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Construction of supramolecular organic frameworks (SOFs) based on noria and bipyridine type spacers Rahul S. Patil, Chen Zhang, Charles L. Barnes, and Jerry L. Atwood Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.6b01464 • Publication Date (Web): 12 Dec 2016 Downloaded from http://pubs.acs.org on December 13, 2016

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Crystal Growth & Design

Construction of supramolecular organic frameworks (SOFs) based on noria and bipyridine type spacers Rahul S. Patil,a Chen Zhang,a Charles L. Barnes,a and Jerry L. Atwooda* a

Department of Chemistry, University of Missouri, 601 S College Ave Columbia, MO 65211

KEYWORDS: Macrocyclic compounds, Hydrogen bonded frameworks, crystalline solids, linkers

ABSTRACT: Among the class of porous crystalline materials, supramolecular organic frameworks (SOFs) have proven to be of great importance due to their potential applications in gas sorption/separation, catalysis, and nanotechnology. Herein, we present construction and characterization of two novel SOFs based on large macrocyclic compound- noria, and linker molecules such as 4,4’-bypyridine and 1,2-Bis(4-pyridyl)ethylene. Use of bipyridine type spacer molecules can partially or completely replace typical O-H···O intermolecular hydrogen bonds between noria molecules by O-H···N interactions. Due to the moderate length difference, the two spacer molecules lead to the assembly of 1D chains and 2D networks, respectively.

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Introduction: As one of the porous materials, supramolecular organic frameworks (SOFs) have attracted intensive attention because of their lucrative and potential applications in the field of selective gas sorption/separation,1,2 catalysis,3 drug delivery,4 and nanotechnology.5 SOFs are constructed from multiple organic modules held together via non-covalent interactions (e.g., hydrogen bonds, cation-π interactions, π-π interactions and van der Waals forces). The shape and architecture of these SOFs are modelled through these comparatively weak non-covalent interactions. However, the freedom of functional group modularity and high crystalline nature of the SOFs offer easy and effective evaluation of structure-property relationship of framework with various guest molecules.1 Thus, selection of building blocks is crucial with respect to overall shape and properties of SOFs. In that context, large organic macrocycles, such as cyclodextrin,6 cucurbiturils,7 calixarenes,8 and pillarenes9 have proven to act as useful building blocks for construction of SOFs. The unique cyclic shape and presence of various functional groups on these macrocyclic compounds make them favourable building blocks in construction of SOFs with variety of architectures. In particular, C-alkylresorcin[4]arenes (RsC) and Calkylpyrogallol[4]arenes (PgC) (subclasses of calix[4]arenes) offered construction of SOFs with different shapes and architectures ranging from dimeric capsule,10,11 metal-seamed dimers and hexamers,12-14 extended capsules,11,15 nanotubes,16 to hydrogen bonded hexamers.17,18 These SOFs of RsCs and PgCs have also been characterized to understand host-guest interactions19,20 and molecular recognition.21,22 These SOFs often enclosed void spaces and channels within the extended crystal structure, which are filled with disordered solvent molecules.15,23 To extend the studies of SOFs based on calixarenes, here we report synthesis of two novel SOFs using a large macrocycle- noria,(C102 H96 O24) and 4,4’-bipyridine (bpy) or 1,2-bis(4-pyridyl)ethylene (bpe) as


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building blocks (Figure 1A). The bpy and bpe were selected for synthesis of SOFs because of their linear shape and capability to act as spacers in similar SOFs.15,23,24 25 Bpy and bpe have pyridine functionalized ends which work as acceptors in the intermolecular hydrogen bonding interactions. Noria is also a double cyclic ladder-like oligomer where each ring has three alternate resorcinols (peripheral resorcinols) and methylene units where these two rings are connected through six resorcinols (bridged resorcinols) units (Figure 1B). Thus, this large macrocycle has six small partial bowl shaped cavities at the periphery and a large hydrophobic cavity at the centre. The diameter of central cavity is 5-7Å and the internal volume is calculated to be 160 Å3.26,27 Noria was synthesized from previously reported acid catalysed condensation reaction between resorcinol and glutyraldehyde in presence of concentrated HCl.28,29 Formation of cyclic oligomer was analysed with help of 1H, 13C, DEPT135 and HMQC NMR (Figure S1, S2, S3 and S4). The crystal structure of noria has already been reported where the single crystals of noria were grown through vapour diffusion of methanol into saturated solution of noria in dimethyl sulfoxide (DMSO).26 The crystal structure confirms the cyclic shape of noria and its interaction with solvent of crystallization such as DMSO. Owing to its large oligomeric nature, noria has very limited solubility in organic solvents and only dissolves in high boiling solvents such as dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAC), and Nmethyl-2-pyrrolidone (NMP).28 Thus, choice of solvent for crystallization of SOFs from noria is limited to above mentioned solvents. We crystallized noria in DMSO and used same solvent for crystallization of SOFs as well. Single crystals of the SOFs were grown by dissolving the components of the frameworks (noria, bpy/bpe) in hot DMSO followed by slow cooling of the saturated solution.


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Figure 1. A] Components of Frameworks. B] Peripheral and bridged resorcinols in noria. Result and Discussion: Crystal structure of 1 [(noria) 18(DMSO)] consists of noria molecules interacting with DMSO molecules through various intermolecular interactions such as hydrogen bonds and CH-π interactions. The parent noria itself possesses O-H···O (2.69Å-2.77Å) intramolecular hydrogen bonding interactions between the hydroxyl groups of peripheral resorcinols and bridged resorcinols. These intramolecular hydrogen bonds are responsible for holding six partial bowl


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shaped cavities and helped maintaining the overall macrocyclic shape of noria. Twelve hydroxyl groups on bridged resorcinols form O-H···O (2.57Å-2.62Å) intermolecular interactions with twelve DMSO molecules (Figure S5). However, six DMSO molecules also sit in the six partial bowl shaped cavities of noria interacting through weak CH-π interaction with electron cloud of cavities (Figure S5). Thus, one noria molecule is surrounded by eighteen DMSO molecules. Crystallographic expansion reveals that, noria molecules also stack on top of each other along [1 0 0] and [0 1 0] crystallographic direction (Figure S6 and S7).

Figure 2. A] Intermolecular interaction between noria and bpy along [100] direction in crystal structure of 2. B] Central parent noria molecule is connected to six noria molecules through twelve bpy molecules (Colour codes: Gray-Carbon, Blue: Nitogen, Red-Oxygen). The ability a noria to form multiple intermolecular hydrogen bonding interactions with neighbouring molecules encouraged crystallization of noria with bpy in similar conditions. Thus, plate like single crystals of 2 [(noria) 6(bpy) 19(DMSO)] were grown where asymmetric unit


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comprised of noria, bpy and DMSO molecules. Similar to 1, noria molecule also has O-H···O (2.63Å-2.95Å) intramolecular interactions among the peripheral and bridged hydroxyl groups. However, twelve hydroxyl groups of bridged resorcinols form O-H···N (2.65Å-2.70Å) hydrogen bonds with twelve bpy molecules (Figure 2A). The twelve hydrogen bonded DMSO molecules in 1 are replaced by bpy in 2. With the other end, these bpy molecules also form O-H···N intermolecular hydrogen bonds with six noria molecules. Thus, a parent noria molecule is connected with six noria molecules through twelve bpy molecules (Figure 2B). In extended crystal structure of 2, this intermolecular interaction resulted in the formation of 2D supramolecular network of hydrogen bonded noria and bpy. Multiple layers of hydrogen bonded noria and bpy are placed parallel to each other along [0 1 0] direction (Figure 3A). Although, these successive layers are placed a little offset to each other, they still enclosed channels along [1 0 0] crystallographic direction (Figure 3B). These channels are filled with disordered DMSO molecules which form weak van der Waals interactions with components of the framework.


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Figure 3. A] Multiple hydrogen bonded layers of noria and bpy placed parallel in extended crystal structure of 2. B] Spacefill view of channels enclosed in 2 along [1 0 0] crystallographic line (Colour codes: Gray-Carbon, Blue: Nitogen, Red-Oxygen). Introduction of bpy with noria induces formation of 2D arrangement with molecular level channels filled with solvent molecules in the extended framework. Thus, moderately longer spacer, bpe was next introduced with noria in similar crystallization conditions. Crystal structure of 3 [(noria) 2(bpe) 7(DMSO)] also has O-H···O intramolecular interactions similar to 1 and 2.


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Intermolecular interactions in 3 involve O-H···O (2.56Å-2.67Å) hydrogen bonding interactions between eight hydroxyl groups from bridged resorcinols and eight DMSO molecules (Figure S8). Four hydroxyl groups on these bridged resorcinol also interact with four bpe molecules through O-H···N (2.67Å-2.73Å) interactions. These four bpe molecules are placed on diagonally opposite side of noria molecules with two bpe molecules interacting with same noria molecule on each side. Thus, out of twelve hydroxyl groups on bridged resorcinols, eight hydroxyl groups interact with DMSO while four hydroxyl groups interact with bpe spacers. With the other end, these four bpe molecules also form similar O-H···N (2.67Å-2.73Å) hydrogen bonds with two noria molecules. Thus, a parent noria molecule is connected to two noria molecules through four bpe molecules (Figure 4A). The crystallographic expansion reveals the alternated 1D arrangement of hydrogen bonded noria and bpe along [0 1 0] crystallographic axis. This intermolecular hydrogen bonding between noria and bpe reveals an alternate arrangement of noria and bpe in extended crystal structure along [001] direction (Figure 4B).


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Figure 4. A] Alternate 1D arrangement of noria and bpe in extended structure of 3 (Colour codes: Gray-Carbon, Blue: Nitogen, Red-Oxygen). B] Arrangement of 1D layers of noria and bpe in extended crystal structure of 3. Conclusion: Herein, we present two novel SOF materials synthesized by cocrystallization of noria and bipyridine type spacer molecules. Due to the moderate length difference of spacer molecules, bpy leads to the formation of 2D networks while bpe causes 1D arrangement of components of SOFs. Slightly offset arrangement of 2D layers of noria and bpy reveals the formation of channels enclosed within the framework. These results will shed light to the construction of SOF materials with various topologies by carefully choosing building blocks and spacer molecules.


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Future studies can be focused on the synthesis of 3D SOF materials with permanent and sizecontrollable pores and their applications such as gas adsorption and separation. Supporting Information Supporting information contains ChemDraw structure of noria, experimental details and characterization of compounds (NMR, additional crystallographic data and powder XRD data). Accession Codes CCDC 1451803, 1451804 and 1451805 contain the supplementary crystallographic data for this paper. These data are provided free of charge by The Cambridge Crystallographic Data Centre. AUTHOR INFORMATION Corresponding Author *Prof. Jerry L Atwood, Email: [email protected] Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Funding Sources and Acknowledgement We would like to acknowledge Wei Wycoff for helping with NMR facility at Department of Chemistry, University of Missouri-Columbia. The facility was supported by NSF (grant DBI0070359) and University of Missouri funding. Notes The authors declare no competing financial interest.


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ABBREVIATIONS bpy: 4,4’-bipyridine bpe: 1,2-Bis(4-pyridyl)ethylene DMSO: Dimethyl sulfoxide

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For Table of Contents Use Only: Construction of supramolecular organic frameworks (SOFs) based on noria and bipyridine type spacers Rahul S. Patil, Chen Zhang, Charles L. Barnes, and Jerry L. Atwood*

Synopsis: We herein present two novel supramolecular organic frameworks (SOFs) based on a large macrocycle, noria, and linker molecules such as 4,4’-bypyridine and 1,2-Bis(4-pyridyl)ethylene. Due to the moderate difference in length, the two spacer molecules result in the assembly of 1D chains and 2D networks, respectively.


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Figure 1. A] Components of Frameworks. B] Peripheral and bridged resorcinols in noria. 51x45mm (300 x 300 DPI)


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Figure 2. A] Intermolecular interaction between noria and bpy along [100] direction. B] Central parent noria molecule is connected to six noria molecules through twelve bpy molecules. 66x33mm (300 x 300 DPI)



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Figure 4. A] Alternate 1D arrangement of noria and bpe in extended structure of 3. B] Arrangement of 1D layers of nori and bpe in extended crystal structure of 3. 48x34mm (300 x 300 DPI)


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Table of content 44x37mm (300 x 300 DPI)



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Figure 3. A] Multiple hydrogen bonded layers of noria and bpy placed parallel in extended crystal structure of 2. B] Spacefill view of channels enclosed in 2 along [1 0 0] crystallographic line (Colour codes: GrayCarbon, Blue: Nitogen, Red-Oxygen). 47x41mm (300 x 300 DPI)


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