Spherical Aggregates and Crystal Structure of Naphthalenediimide

Nov 30, 2017 - Center for Analytical Instrumentation, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan. Cryst. Growth ... Crystal Gro...
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Spherical Aggregates and Crystal Structure of NaphthalenediimideBased Macrocycle and Complexation with Perylene Masahide Tominaga,*,† Masatoshi Kawahata,† Tsutomu Itoh,‡ and Kentaro Yamaguchi*,† †

Faculty of Pharmaceutical Sciences at Kagawa Campus, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan Center for Analytical Instrumentation, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan



S Supporting Information *

ABSTRACT: A naphthalenediimide-based macrocycle with adamantane parts was synthesized from naphthalenetetracarboxylic dianhydride and 1,3-adamantanedimethanamine. The addition of methanol to a chloroform solution of the macrocycle led to formation of spherical species and their fused network aggregates, which were transformed into crystals. X-ray analysis showed a crescent-shaped molecular structure. In the presence of perylene, charge-transfer cocrystals of sandwich-type complexes were generated via selfassembly of nanostructures.

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of methanol to a chloroform solution of 1, spherical species and their fused network aggregates were formed, and ultimately converted to crystals 1a. In the presence of perylene, spherical aggregation, fusion, and phase transition from the solution to co-crystals were observed. In co-crystals 1b, one perylene is sandwiched between two molecules of 1 by donor−acceptor interactions. Recently, we showed that cyclic adamantane-containing molecules self-assembled into hollow spheres and their fused network aggregates, which were then transformed into crystals.36,37 The aliphatic adamantane moieties in these compounds are required for the generation of self-assembled nanostructures and subsequent crystal formation. We therefore incorporated adamantane derivatives into NDI-based macrocycles with the aim of investigating the molecular assembly process. We designed and synthesized a macrocyclic naphthalene-1,8:4,5-bis(dicarboximide) dimer linked by a rigid methyleneadamantane spacer through covalent bonds. The synthesis of 1 is shown in Scheme 1. The reaction of naphthalenetetracarboxylic dianhydride with 1,3-adamantanedimethanamine in N,N-dimethylformamide gave 1 in 21% yield. The 1H NMR spectrum of 1 in CDCl3 shows one singlet from the aromatic protons, at 8.70 ppm, indicating that the product has a symmetric cyclic structure. The high-resolution mass spectrum had a molecular ion at m/z = 853.3205, for [M + H]+, which is consistent with the molecular weight of 1. The molecular structure of 1 was clearly established using single-crystal X-ray crystallography. Colorless single crystals 1a were obtained from 1 in a mixture of methanol and chloroform.

n recent decades, naphthalenetetracarboxylic diimide (NDI) derivatives have received considerable attention as ideal and popular building blocks for the development of semiconductor materials, catalysts, and chemosensors in a wide variety of fields, including materials science, biology, and supramolecular chemistry.1−11 Naphthalenediimides are interesting organic molecules because of their easy functionalization, good thermal stability, and tunable photophysical properties. NDI units have therefore been embedded in macrocycles, cages, catenanes, and rotaxanes as molecular building blocks,12−17 and in polymers, metal−organic frameworks, and covalent organic frameworks.18−23 Among numerous interesting and unique functional molecules with NDI parts, cyclic compounds have been used as host molecules for anions and neutral organic molecules, and as platforms for the investigation of electronic and magnetic properties by Stoddart, Wasielewski, Sanders, and other groups.24−32 In previous studies, two or three NDI units have been connected with methylenebenzene, chiral cyclohexane, or octamethylene spacers to regulate the distances and overlapping of their π-aromatic faces and to control the conformations of their skeletons. Supramolecular assemblies were recently constructed from NDI-containing macrocycles. Stoddart and co-workers reported the formation of supramolecular nanotubes from enantiomeric molecular triangles in 1,2-dihalohydrocarbons.33,34 Berndt and co-workers showed that rigid naphthalenediimide cyclophanes could be arranged into layers on an Au(1,1,1) surface.35 However, there have been fewer reports of the preparation of supramolecular nanostructures such as spherical and tubular aggregates than of acyclic NDI derivatives.1−5 Here, we report the synthesis and structural analysis of a naphthalenediimide-derived macrocycle containing adamantane parts (1). X-ray crystallographic analysis showed that 1 has a crescent-shaped molecular structure. On addition © XXXX American Chemical Society

Received: September 25, 2017

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DOI: 10.1021/acs.cgd.7b01361 Cryst. Growth Des. XXXX, XXX, XXX−XXX

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Scheme 1. Synthesis of NDI-Derived Macrocycle with Adamantane Units

The crystal structure has a crescent-like shape with a cavity formed by tilting of the aromatic planes toward each other (Figure 1). The centroid−centroid distance of the adamantyl

Figure 3. Top view of 1 and perylene in crystal 1b showing thermal ellipsoids. Solvent molecules are omitted for clarity.

Figure 1. (a) Top and (b) side views of 1 in crystal 1a showing thermal ellipsoids. Solvent molecules are omitted for clarity.

groups is 12.43 Å. The dihedral angle between its two πaromatic faces is 53.0°. The distances between oxygen atoms are 7.59 and 7.74 Å at the upper rim and 3.40 and 3.56 Å at the lower rim. Columnar structures are built up by intermolecular π···π interactions between the NDI moieties in 1; the dihedral angle shows that the aromatic faces are parallel (Figures 2 and S1,

Figure 4. Packing diagram of 1 and perylene in crystal 1b: side view of the layer structure. Solvent molecules are omitted for clarity.

organized into layered structures by CH···O interactions between the NDI units and perylene. One chloroform molecule is accommodated in the cavity of 1 by CH···O interaction. Cocrystals were obtained when the initial ratios of 1 and perylene were 1:5 and 1:2 in a mixture of methanol and chloroform. However, co-crystals were not generated when the ratios were 1:1 and 2:1. In this solvent system, excess perylene is needed for the formation of co-crystals. The molecular assembly of 1 in the crystallization solvent used was investigated. Macrocycle 1 is soluble in chloroform, but less soluble in methanol. Methanol was added to a chloroform solution of 1 (methanol/chloroform = 35:65, v/v, 1.0 mM) and the solution was allowed to stand at 25 °C. Fieldemission scanning electron microscopy (FE-SEM) showed the formation of spherical particles of diameter approximately 300 nm after 1 h (Figures 5a and S4a). In transmission electron microscopy (TEM) images, the spheres were completely black, suggesting that the spherical aggregates are solid structures (Figure 5b).41,42 The internal structures of the spherical aggregates obtained from 1 differed from those previously reported for aggregates built from cyclic adamantane-bearing compounds. The SEM images show that with time the number of spherical aggregates decreased and those of microsized rods and sheets increased. Some network aggregates were produced by the fusion of spherical aggregates to minimize the surface area of the nanostructures in the relatively polar environment (Figures 5c and S4b). After 22 h, in the early stages after formation of crystals of 1a, microsized materials and solid spheres were mainly observed. In contrast, crystals were not

Figure 2. Packing diagram of 1 in crystal 1a: side view of the layer structure. Solvent molecules are omitted for clarity.

Supporting Information). Individual columns are fabricated and give a layered structure via CH···O interactions between the NDI units. One chloroform molecule is included in the cavity of 1 by halogen···π interaction.33 Perylene and its analogs, which are electron-donor molecules, interact with acyclic NDI derivatives to give charge-transfer complexes.38 Dark-green crystals of 1b were obtained from a chloroform/methanol solution of 1 and perylene in a 1:5 stoichiometric ratio; this color differs from those of both the solid components (Figure S2). One perylene molecule is sandwiched between the aromatic parts of two molecules of 1 by donor−acceptor interactions.39,40 The macrocyclic structure in crystal 1b is similar to that in crystal 1a (Figure 3). The face-to-face distance between the NDI parts and perylene is 3.40 Å. The complexes composed of 1 and perylene are arranged into columnar structures by π-stacking of NDI parts, with a distance of 3.35 Å (Figures 4 and S3). The columns are B

DOI: 10.1021/acs.cgd.7b01361 Cryst. Growth Des. XXXX, XXX, XXX−XXX

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Methanol was added to a chloroform solution (methanol/ chloroform = 4:6, v/v) of 1 (1.0 mM) and perylene (5.0 mM), and the solution was allowed to stand at 25 °C. After 1 h, crystals of perylene were generated from the solution, and SEM and TEM images indicated the production of large spherical objects of diameter approximately 400 nm (Figures 5d,e and S7a). The formation of network aggregates, microsized rods, and sheets, instead of spherical aggregates, gradually increased with time (Figures 5f and S7b). After 20 h, in the early stage after formation of co-crystals 1b, spherical architectures and microsized plate materials were predominantly observed (Figure 6). As a control experiment, excess perylene was added to a solution of 1 in methanol and chloroform; no cocrystals were generated, confirming that complexation of the two components in chloroform is essential for co-crystal formation. Yellow crystals were generated after 0.5 h from a solution of perylene (5.0 mM) in a mixture of methanol and chloroform (4:6, v/v); a SEM image showed the production of microsized blocks and plates (Figure S8). These experimental results suggest that one-dimensional columnar architectures consisting of 1 and perylene, identified by X-ray analysis of crystal 1b, could be partly involved in producing spherical and network aggregates in a polar environment because the macrocycles consist of two different segments, i.e., aliphatic adamantane parts and aromatic units bearing polar functional groups. It is worth noting that the generation of large spherical aggregates derived from 1 and perylene, relative to those built from 1, is possibly ascribed to donor−acceptor interactions in the columnar assemblies of the complexes.43 Molecular assembly and the dynamic behaviors of the two components are unique phenomena.44,45 The molecular assembly behavior was investigated in detail by synthesizing an adamantane-containing macrocycle with pyromellitic diimide (PMDI) parts from pyromellitic dianhydride and 1,3-adamantanedimethanamine in acetic acid; the product yield was 43% (Scheme 2). The preparations and guest-inclusion abilities of several PMDI-based macrocycles have been reported.46,47

Figure 5. SEM images after (a) 1 h and (c) 3 h, and (b) TEM image after 1 h obtained from methanol/chloroform (35:65, v/v) solution of 1 (1.0 mM). SEM images after (d) 1 h and (f) 3 h, and (e) TEM image after 1 h obtained from methanol/chloroform (4:6, v/v) solution of 1 (1.0 mM) and perylene (5.0 mM).

generated after one month in chloroform, confirming that the driving force for molecular assembly can be largely attributed to a solvent effect (Figure 6).

Scheme 2. Synthesis of PMDI-Derived Macrocycle with Adamantane Units

Figure 6. Schematic diagram of self-assembly and crystal structures of 1, with or without perylene.

Complexation of the two components and their self-assembly in solution were investigated using 1H NMR spectroscopy. Spectra of solutions of 1 (1.0 mM) in chloroform-d and a mixture of methanol-d4 and chloroform-d (4:6, v/v) were recorded. When perylene (5.0 mM) was added to a CDCl3 solution of 1 (1.0 mM), the aromatic proton signal for 1 shifted upfield, indicating complex formation between 1 and perylene (Figure S5). On addition of methanol-d4 to a CDCl3 solution of 1 (1.0 mM) and perylene (5.0 mM), the signal shifted further upfield, suggesting that complexes of 1 with perylene are maintained under relatively polar conditions (Figure S6). The coassembly and morphology of 1 with perylene were similar to those in the absence of perylene, as confirmed by FE-SEM.

We obtained single crystals of 2a from a solution of 2 in a mixture of methanol and chloroform. Figure 7 shows that the molecular structure of 2 is similar in shape to that of 1. The centroid−centroid distance of the adamantyl groups is 11.53 Å. The dihedral angle between the two aromatic faces is 56.2°. The distances between the oxygen atoms in the PMDI units are 7.81 and 8.00 Å at the upper rim and 3.52 and 3.66 Å at the lower rim. The packing and intermolecular interactions of 2 are totally different from the one-dimensional π-stacking of 1 in crystal 1a. C

DOI: 10.1021/acs.cgd.7b01361 Cryst. Growth Des. XXXX, XXX, XXX−XXX

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Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.



AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected].

Figure 7. (a) Top and (b) side views of 2 in crystal 2a showing thermal ellipsoids. Solvent molecules are omitted for clarity.

ORCID

Masahide Tominaga: 0000-0003-3199-1882 Masatoshi Kawahata: 0000-0003-2865-4113

Columnar structures with CH···π interactions between the PMDI moieties in 2 are constructed, with a dihedral angle between the aromatic faces of 56.2° (Figures 8 and S9). The columns are assembled into layered structures by CH···O interactions between the PMDI and adamantane moieties. One chloroform molecule is trapped in the cavity of 2.

Notes

The authors declare no competing financial interest.



ACKNOWLEDGMENTS This work was supported by JSPS KAKENHI Grant Number JP16K05801. HRMS was performed at the Center for Analytical Instrumentation, Chiba University.



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Figure 8. Packing diagram of 2 in crystal 2a: side view of the layer structure. Solvent molecules are omitted for clarity.

Methanol was added to a chloroform solution of 2 (methanol/chloroform = 7:3, v/v, 1.0 mM), and the solution was allowed to stand at 25 °C. Crystals appeared after 19 h. After 1 and 3 h, SEM micrographs showed no formation of spherical and well-defined supramolecular aggregates. At the time of crystal formation, microsized rods and sheets were mostly observed. This shows that π-aromatic moieties influence the generation of solid spheres in solution. In conclusion, we investigated the synthesis, crystal structure, and solvent-induced assembly of NDI-based macrocycles containing adamantane units, which formed crystals through spherical and fused network aggregates in organic solutions. In the presence of perylene, co-crystals were produced via selfassembly of nanostructures, in which a perylene molecule was trapped by two molecules of 1 via donor−acceptor interactions to form a sandwiched structure. These findings regarding the transformation from two-component assemblies into co-crystals provide useful information for the construction of sophisticated and advanced supramolecular architectures and functional crystalline materials.48,49 The preparation of covalently linked macrocycles consisting of perylene diimides, and their molecular assembly, are currently under investigation.



REFERENCES

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.cgd.7b01361. Synthetic procedures, characterization data, NMR spectra, SEM images, and crystal data (PDF) Accession Codes

CCDC 1570420−1570422 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The D

DOI: 10.1021/acs.cgd.7b01361 Cryst. Growth Des. XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.cgd.7b01361 Cryst. Growth Des. XXXX, XXX, XXX−XXX