DOI: 10.1002/chem.201304117
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& Self-Assembly
Controlled Nanodimensional Supramolecular Self-Assembly of Tetra-Alkylated Naphthalene Diimide Derivatives Sheshanath V. Bhosale,*[a] Namdev V. Ghule,[b, c] Mohammad Al Kobaisi,[a] Melissa M. A. Kelson,[a] and Sidhanath V. Bhosale*[b]
Abstract: Construction of thermodynamically stable nanostructures on the nano- to millimeter scales through noncovalent bonding plays an important role in material science. The self-assembly of tetra-alkylamino core-substituted naphthalene diimides (cNDIs) with variable alkyl chains (C8H17, C12H25, and C16H33) added on to the core leads to the formation of a variety of controlled morphologies and well-defined nanostructures. Such structures include nanorods, vesicular, belts, twisted ribbons, and donutlike morphologies (formed in CHCl3/MeOH and CHCl3/hexane mixtures) gener-
Introduction Construction of thermodynamically stable nanostructures on the nano- to millimeter scales, through noncovalent bonding, plays an important role in material science.[1] This tactic is pertinent in the development of well-designed nanomaterials and biomaterials, for which the use of p–p interactions and solvophobicity is required to produce well-defined nanostructures (nanobelts, nanowires, micellar, and vesicular aggregates). The methodology has been implemented on the larger aromatic macrocycles.[2] Naphthalene diimide, a smaller version of previously used p-conjugated polycyclic aromatic compounds, can be functionalized through the diimide nitrogen atoms or by core substitution. This functionalization can be used to produce analogues, for which the absorption and emission properties are tunable.[3] Core-substituted naphthalene diimides [a] Dr. S. V. Bhosale, Dr. M. Al Kobaisi, M. M. A. Kelson School of Applied Sciences RMIT University, GPO Box 2476V Melbourne, VIC-3001 (Australia) Fax: (+ 61) 3-9925-3747 E-mail:
[email protected] [b] N. V. Ghule, Dr. S. V. Bhosale Polymers and Functional Material Division Indian Institute of Chemical Technology Hyderabad-500607, Andhra Pradesh (India) E-mail:
[email protected] [c] N. V. Ghule Department of Organic Chemistry School of Chemical Sciences North Maharashtra University Jalgaon-425001, M.S. (India) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201304117. Chem. Eur. J. 2014, 20, 10775 – 10781
ated through solvophobic control. UV/Vis absorption and fluorescence spectroscopy demonstrate molecular aggregation in solution. Furthermore, SEM was employed to visualize the supramolecular self-assembled nanostructures. The growth of these structures is mainly due to packing of hydrophobic alkyl chains and p–p stacking of the cNDI core. The present study paves the way to rational and controlled designs of nanostructures made of optically active dyes (naphthalene diimide); this may open a new avenue towards tuning nanodimensional morphology.
(cNDIs) have attracted great attention due to the interesting electro-optical properties and potential applications in organic, supramolecular, medicine, material sciences, and organic electronics.[3a] Since then, NDIs have rapidly developed to a class of their own in an attractive strategy to create highly colorful, conducting, functional materials in a molecular[4] and supramolecular sense,[5] with significantly different photophysical properties than the core-unsubstituted counterparts.[3] During recent years, various groups have devoted their work to the expansion of the NDI moiety at the 2,6-[3–6] and 2,3,6,7core positions[7] (tetracene cNDI). Interestingly, tetracene NDI fused with five,[8] six, or seven laterally fused six-membered[9] heterocyclic acene diimides have attracted much attention due to their unique optical and electrical properties.[10] However, self-assembled nanostructures of cNDI derivatives have not yet been extensively studied, with only a few precise nanostructures reported.[5] The extended planar, rigid, naphthalene core of NDIs promotes spontaneous self-assembly, which has been used to prepare novel nanostructures. In our previous work,[5a–c] examples for self-assembly of alkylor oligoethylneneglycol annulation of six-membered heterocyclic aromatic rings, either on one side of the core of the NDIs (I and II in Scheme 1) or on both sides (III and IV), were reported. Precisely, the self-assembly of six-membered one-sided alkylannulated cNDIs (compound I) self-assemble into well-defined wormlike nanostructures and methoxytriethyleneglycol-annulated cNDIs (compound II) self-assembled into multilamellar vesicular aggregates with defined diameters. Interestingly, cNDIs annulated on both sides with long alkyl chains (compound III) or methoxytriethyleneglycol (compound IV) form a variety of well-defined nanostructures in polar and nonpolar solvent mixes through solvophobic control.
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Scheme 1. Core-substituted NDIs reported so far in the self-assembly. Scheme 2. Synthesis of tetra-alkyl-substituted naphthalene diimides.
In this work, we explore the development and use of directly tetra-alkylamino-substituted cNDIs (1, 2, and 3) with different lengths of the alkyl chains on the core, that is, C8, C12 and C16, respectively, for the solvophobically controlled assembly of nanostructures (Figure 1). Characteristically, tetra-alkylaminosubstituted cNDIs (1–3) possess two important properties resulting in formation of a variety of nanostructures through noncovalent interactions: 1) the aromatic core of the cNDI, which is designed to optimize the dispersive interactions (p–p stacking and van der Waals interactions) between the cores within a construct, and 2) variable lengths of the hydrophobic alkyl chains that help maximize the influence of solvents. These arrangements prevent crystallization and favor the directional growth of the nanostructure in a 1D–3D fashion (Figure 1).[5a–c]
wise, the reaction of 4 with dodecylamine (6) or hexadecylamine (7), resulting in the corresponding core-tetra-aminofunctionalized cNDI-C12 and cNDI-C16 (2 and 3) in 93 and 90 % yields, respectively, as a dark green solid after column chromatography (silica gel; dichloromethane/hexane, 1:1, v/v; see details in the Supporting Information). The normalized absorption and emission of tetra-alkylamino cNDIs (1–3) are shown in Figure 2 and 3. In chloroform, cNDIs (1–3) exhibits a distinct absorption band with a maximum at 639 nm (1: e = 30 600 m 1 cm 1, 2: e = 30 000 m 1 cm 1, 3: e = 29 500 m 1 cm 1), which is similar to that of reported tetraoctyl-substituted cNDIs.[12] This is characteristic for the S0–S1 transition of the isolated cNDI chromophores. A second absorption band appears at 395–512 nm with the maxima at 462 nm (e = 11 890 m 1 cm 1); this band can be attributed to Results and Discussion the electronic p–p* transition, involving only the NDI chromophores (Figure 2). The presence of two absorption bands in The tetra-alkylamino-substituted cNDI derivatives (1–3) were wide visible region provides the dark greenish color of the prepared by nucleophilic substitution of tetrabromo NDI 4[11] cNDIs (1–3).[7, 12] with alkylamino nucleophiles (5–7) in toluene at reflux temper[12] Figure 2 a shows the absorption spectra of the cNDIs (1-3) in ature under N2 atmosphere (Scheme 2). Typically, reaction of CHCl3/hexane (4:6, v/v), in which a reduction in peak intensity 4 with octylamine (5) afforded cNDI-C8 (1) in 96 % yield. Likealong with a significant blueshift of the S0–S1 absorptionmaxima band, that is, 41 nm (496 nm) shift, were observed. However, in CHCl3/MeOH (4:6, v/v), the cNDIs (1–3) exhibit a redshift at longer wavelengths, that is, 23 nm (662 nm) along with a loss of the fine structure (Figure 2 b). Furthermore, Figure 2 c shows the absorption spectra of cNDI-C12 (2) in various ratios of hexane and chloroform, as the ratio of hexane to chloroform increases (0, 10, 20, 35, and 40 %, v/v), aggregation is evidenced by a reduction in peak intensity along with a blueshift of the absorption maxima. Whereas an increase in the proportion of Figure 1. Schematic illustration of possible mechanisms for the formation of supramolecular nanostructures of methanol in chloroform led to tetra-alkylamino-substituted cNDIs 1–3 and the respective SEM micrographs (A–D). Chem. Eur. J. 2014, 20, 10775 – 10781
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Full Paper band at 592 nm (Figure 3 a), however in CHCl3/hexane (4:6, v/v) two distinct bands appear, one at 680 nm along with a new blueshifted (40 nm) band at 645 nm.[12] Interestingly, in CHCl3/ MeOH (4:6, v/v), the fluorescence emission is quenched to varying degrees (Figure 3 b). This is attributed to the self-assembly of 1–3 into aggregates that affect the electronic structure. Furthermore, Figure 3 c shows emission of cNDI-C12 (2) in various ratios of hexane and chloroform (0, 10, 20, 35, and 40 %, v/v); blue-shifts occur in the emission band at 680 nm at higher ratios of hexane (Figure 3 c). The fluorescence emission
Figure 2. UV/Vis spectra of cNDIs ([1--3] = 1 10 4 m) in a) CHCl3 and CHCl3/ hexane (4:6, v/v), b) CHCl3 and CHCl3/MeOH (4:6, v/v). c, d) The absorption of 2 (c = 1 10 4 m) in various ratios of hexane in CHCl3 and methanol in CHCl3 at room temperature, respectively; arrows indicate how the absorption intensity changes upon increasing the hexane and methanol percentage in the different mixtures.
a reduction in peak intensity along with a significant redshift of the absorption maxima (Figure 2 d). These features suggest an influence of solvent polarity and perhaps formation of larger aggregates, especially because similar behavior has been observed for monoannulated cNDIs and acene diimides.[5] The fluorescence emission of cNDIs (1–3) shows a band at 685 nm in neat CHCl3 upon excitation in the S0–S1 absorption Chem. Eur. J. 2014, 20, 10775 – 10781
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Figure 3. Emission spectra of cNDIs 1–3 (c = 1.2 10 4 m; lex = 592 nm) in pure CHCl3 as well as a) CHCl3/hexane, and b) CHCl3/MeOH mixtures. c, d) The absorption of cNDI (2, c = 1 10 4 m) in various ratios of hexane in CHCl3 and methanol in CHCl3 at room temperature, respectively; arrows indicate how the emission intensity changes upon increasing the ratios of hexane and methanol in chloroform.
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Full Paper of 2 was quenched along with slight redshift at higher ratios of methanol (0–40 %) in CHCl3 (Figure 3 d). The absorption and fluorescence spectroscopy suggest formation of p stacks of the rotationally displaced NDI chromophores. The cNDIs (1–3) give a blueshift in CHCl3/hexane, which is typical of H-type aggregates. On the other hand, in CHCl3/MeOH, the cNDIs (1–3) self-assemble into J-type aggregates. These effects are similar to that of J- and H-aggregates in cNDIs.[5] This type of aggregation may be directed by p–p stacking of the NDI core cooperatively with the peripheral alkyl groups; together this leads to the final aggregate type. This encouraged us to further investigate the self-assembly of the cNDIs (1–3) by using SEM imaging. Samples of cNDIs ([1–3] = 1.5 10 4 m) in CHCl3/hexane (6:4, v/v) and CHCl3/MeOH (6:4, v/v) were drop coated on a glass coverslip substrate and sputter coated with gold for 10 s at 0.016 mA Ar plasma (SPI, West Chester, USA) for SEM imaging with a FEI Nova NanoSEM (Hillsboro, USA) operating at high vacuum, which provided direct visualization of the self-assembled nanostructures (Figure 4 and 5). The SEM of cNDI-C8 (1) in the CHCl3/MeOH mixture showed that 1 had self-assembled into nanobelts, approximately 500 nm in width, which folds to form nanorods with 120 nm uniform diameters, which can further turn to form donut-shaped nanostructures (430 nm) by joining head to tail with shorter fibrils. Figure 1 shows a scheme of this mechanism with instances where the transition between the flat-belt and rodlike morphology can be observed. Few instances of flat short fibrils in transition to other morphologies can be observed as shows in Figure 4 a. cNDI-C12 (2) displays tens-of-micrometers-long belts, 1 mm in width (Figure 4 b). cNDI-C16 (3) with hexdecyl chains self-assembled into a ribbonlike morphology, approximately 700 nm wide and the length is in the range of a few tens of micrometers, as shown in Figure 4 c. Interestingly, no rods or vesicles can be seen in the case of cNDIs 2 and 3. The formation of nanorods and donut-like nanostructures in the case cNDI-C8 (1) may be due to the small size of the hydrophobic moiety and the high curvature of the molecular monolayer aggregates forming in solution or during solvent evaporation. Large hydrophobic moieties in cNDIs (2 and 3) allows only for flat arrangements to occur, forming only belts during solvent evaporation (see the Supporting Information, Figure S1–S3). On the other hand, cNDI-C8 (1) in CHCl3/hexane self-assembled into microneedles (A), which are formed through bunching of smaller fibril structures about 900 nm in diameter (C), and (B) nanovesicles with a size distribution between 20 and100 nm, as shows in Figure 5 a. Figure 5 b, reveals self-assembly of cNDI-C12 (2) in CHCl3/ hexane, which assembled into very long belts with 200 nm to 1 mm width in (D). Interestingly when the width of the belt is below 300 nm, it tends to form rods as in (E) and in the background of both micrographs, vesicular aggregates of 20– 40 nm can be observed. cNDI-C16 (3) shows (Figure 5 c) a similar trend of the structure to 2 with some twisted-belt structures similar in dimensions (for details see the Supporting Information, Figure S4–S6). We believe that the formation of vesicles may be due to the hydrophobicity of both solvents, causing Chem. Eur. J. 2014, 20, 10775 – 10781
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Figure 4. SEM images of controlled dimensions formed by cNDI-C8 (1), cNDIC12 (2), cNDI-C16 (3) in CHCl3/MeOH 6:4, v/v. a) cNDI-C8 (1) assembled into nanobelts, ca. 500 nm in width, that folds to form nanorods of about 120 nm in diameter turning and joining end to end to form a donut shape when possible. b) cNDI-C12 (2) formed very long belts, 1 mm in width, and c) cNDI-C16 (3) formed ribbonlike structures, with less than 1 mm in width. The scale bars are 10 mm in A, 1 mm in B and C, 10 mm in D, 5 mm in E, 10 mm in F and G, and 2 mm in H.
the aggregation of the molecule to bury the hydrophilic part of the molecule toward the center and letting the hydrophobic part maintain contact with the solvent (hexane); the same logic may be used for the formation of rods. To gain more structural information, the aggregates formed in 40 % hexane in CHCl3 were examined by AFM techniques. For AFM imaging, samples of 1–3 (10 4 m) in 40 % methanol or hexane in CHCl3 were spin coated onto silica wafers and analyzed in the tapping mode. An optical image of all the three
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Figure 6. Topographic AFM images of nanostructures formed by 1 (10 4 m) in a) MeOH/CHCl3 (4:6, v/v) and b) hexane/CHCl3 (4:6, v/v). c, d) The respective cross-section analysis.
Figure 5. SEM images of self-assemblies formed by cNDI-C8 (1), cNDI-C12 (2), cNDI-C16 (3) in CHCl3/hexane 6:4, v/v. a) cNDI-C8 (1) formed large needleshaped crystallites and nanovesicles of 20–100 nm as in B. b) cNDI-C12 (2) assembled into very long belts, 200 nm to 1 mm wide, as in C, when the width of the belt is < 300 nm, rodlike structures tend to form, as in D, in the background of both micrographs nanovesicles, 20–40 nm in size can be seen. c) cNDI-C16 (3) formed ribbonlike structures with dimensions 700 nm (E, F, and G). The scale bars are 10 mm in A, 1 mm in B, 2 mm in D and E, 2 mm in F and G, and 10 mm in H.
molecules shows well-formed rodlike nanostructures in CHCl3/ MeOH (6:4, v/v, see the Supporting Information, Figure S7). The observed lengths appear to vary; widths and heights of assemblies of 1 are shown in Figure 6 a. The heights of profiles 1–2 are 30 and 60 nm, respectively; this means that the thinnest of the nanostructures double in size (Figure 6 b). As a result, the thickness of the formed nanostructures also varies up to several nanometers. The ratio of the diameter and heights of the Chem. Eur. J. 2014, 20, 10775 – 10781
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nanostructures suggests a flattening upon transfer from solution to the silicon surface. AFM imaging of samples of 1 in a nonpolar solvent mix (CHCl3/hexane; 6:4, v/v) spin coated onto silica wafers also shows regular aggregates, but of a much smaller diameter (Figure 6 c). The height of the aggregates formed by 1 was estimated to be 0.5–1.5 nm (Figure 6 d), which is approximately an order of magnitude smaller than that of the aggregates formed in methanol solution. Similarly, compound 2 and 3 selfassembled into defined nanostructures in nonpolar solvent (see the Supporting Information, Figure S8). Even though the structure is unknown, the results obtained are consistent with the nanostructures seen in the SEM images (Figure 4 and 5). Furthermore, an optical micrograph of 1 in CHCl3/MeOH (6:4, v/v) drop casted on a glass substrate highlights the flexible nature of the nanorods and at some instance they tend to form bundles. The typical nanorod length is between 0.5 and 1 mm. The green solution of c-NDI-C8 (1) in CHCl3/MeOH (6:4, v/v) consists of nanorods, as determined with negatively stained TEM (Figure 7 b). A droplet of 1 in the above solution was dropped onto a grid (400 mesh copper grid coated with a carbon film), thereafter stained with 2 % uranyl acetate and the grid was allowed to air dry at room temperature. Individual nanorod as well as a few instances of bundles of nanorods are clearly visible. The TEM image clearly shows that 1, self-assembled into nanorods, with a diameter of about 400–700 nm and lengths on the micrometer scale. The self-assembled nanostructures seen in TEM are consistent with the SEM and AFM analyses. Importantly, the cNDIs (1–3) failed to give any nanostructures in neat CHCl3 ; this is an indication of the subtleties of the solvophobicity in self-assembled processes. We postulate that, although the self-assembly is predominantly driven by p–p interactions between the cNDI cores, solvophobic interactions between long alkane chains on to the core, which maximize stability, play a crucial role in the formation (Figure 1). The
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Full Paper tetra-alkylamino-substituted cNDIs, close to the infrared region, may lead to applications in photonic and solar cells.
Experimental Section General methods and materials
Figure 7. a) Optical micrograph of 1 from a CHCl3/MeOH (6:4, v/v) solution on a glass substrate, showing flexible nanorods with millimeter-scale length, the scale bar represents 50 mm. b) TEM image of 1 prepared from a CHCl3/ MeOH (6:4, v/v) solution with individual (400–700 nm) and bundled nanorods upon staining with uranyl acetate, the scale bar represents 1 mm.
faster evaporation of chloroform drives the cNDIs out of solution and forces them to stabilize by producing complex supramolecular aggregates. cNDI-C8 (1) produces vesicular aggregates in CHCl3/hexane (6:4, v/v), and at a higher concentration, a large irregular crystalline solid. However, in CHCl3/MeOH (6:4, v/v), more complex supramolecular structures evolved due to the higher polarity of MeOH, by stabilizing the p-stacked aggregates over a larger area. The small size of the alkyl chains on 1 makes it easier for these sheets to stabilize further by folding to form nanorods. The SEM micrographs show that these rods of 1 produce even more complex structures by end-to-end joining of short rods to form donut-shaped structures. cNDIs 2 and 3 with large hydrophobic chains (C12H25 and C16H33) produce only rodlike and ribbonlike morphologies. The monolayer-sheet aggregates can stabilize more efficiently by stacking, which is due to the large hydrophobic regions that form more rigid sheets, reducing the stability-energy gain in the rod- and donut-formation processes even at higher concentrations. Importantly, cNDIs 1–3 self-assemble in a similar fashion even at higher concentrations, that is, 10 3 m (see the SEM images in the Supporting Information, Figure S7).
All reagents were purchased either from Sigma Aldrich or Merck and used without any further purification. All the solvents were received from commercial sources and purified by standard methods. Naphthalene tetracarboxy dianhydride, octyl amine, dodecyalamine, hexadecyal amine, CHCl3, methanol, CH2Cl2, and hexane were purchased from Aldrich and used without purification, unless otherwise specified. UV/Vis absorption spectra were recorded on a PerkinElmer Lambda 40p spectrometer. 1H and 13C NMR spectra were recorded on a Bruker spectrometer with CDCl3 as solvent and tetramethylsilane as an internal standard. The solvents for spectroscopic studies were of spectroscopic grade and used as received. Mass spectrometric data were obtained by the ESI-MS technique on an Agilent Technologies 1100 Series (Agilent Chemistation Software) mass spectrometer. HRMS were obtained with an ESI-QTOF mass spectrometry.
UV/Vis absorption spectroscopy An aliquot of the stock solutions of 1–3 (0.2 mL, c = 10 3 m) was transferred to various ratios of CHCl3/hexane, CHCl3/MeOH in different volumetric flasks, to a final volume of 2 mL. The solutions were allowed to equilibrate for 2 h prior to the spectroscopic measurements.
Fluorescence spectroscopy Fluorescence emission spectra were recorded on a Horiba Jobin Yvon FluoroMax-4-Spectrofluorometer. All experiments were performed in a quartz cell with a 1 cm path length and 592 nm excitation wavelength. Solutions were prepared in a similar manner as for the UV/Vis study.
Sample preparation
Conclusion Herein, we report the synthesis and the supramolecular self-assembly of tetra-alkylamino, core-substituted, naphthalene diimides, which form microstructures, such as nanorods and donutlike microbelts with controlled dimensions, in CHCl3/MeOH and CHCl3/hexane mixes through solvophobic control. The aromaticity of the naphthalene diimide core along with the crystalline packing of the hydrophobic alkyl chains give a unique design. It provides a tolerant feature that can be exploited in an array of novel supramolecular microstructures, in which growth of the structures is mainly due to packing of hydrophobic alkyl chains and p–p stacking of the NDI core. The present study paves the way to rational and controlled designs of nanostructures, made of an optically active dye (naphthalene diimide); this may open a new avenue towards the tuning the well-controlled architectures. The present study can be applied in more elaborated supramolecular nano- and microstructures for the development of functional nanomaterials for electronic as well as biomedical applications. The longer absorption and emission range of Chem. Eur. J. 2014, 20, 10775 – 10781
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Stock solutions (c = 1 10 3 m) of 1–3 were prepared in CHCl3. Aliquots of the stock solutions (0.2 mL) were transferred separately to four different volumetric flasks of 1) CHCl3 (100 %), 2) CHCl3/MeOH (6:4, v/v), 3) CHCl3/MeOH (6:4, v/v) to a final volume of 2 mL. The solutions were allowed to equilibrate for 2 h prior to the SEM measurements.
SEM SEM measurements were performed on a FEI Nova NanoSEM (Hillsboro, USA) operating at high vacuum and SEM images were collected. Freshly prepared samples of 1–3 (0.5 mL) were sputter coated with gold for 10 s at 0.016 mA Ar plasma (SPI, West Chester, USA) after drop casting the solutions on a glass coverslip and solvent evaporation.
Synthesis of target cNDIs (1–3) N,N’-Bis-(n-octyl)-2,3,6,7-tetra(n-octylamino)-1,4,5,8-naphthalenetetracarboxylic diimide (1) A mixture of 4,5,9,10-tetrabromo-2,7-dioctylbenzo[lmn][3.8]phenanthroline-1,3,6,8(2H,7H)-tetraone (4, 0.5 g, 0.62 mmol)
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Full Paper and octylamine 5 (0.4 g, 3.1 mmol) in toluene (10 mL) was heated overnight at 110 8C under nitrogen atmosphere. Thereafter, toluene was removed on a rotary evaporator and the product was purified by column chromatography on a silica-gel column eluted with CH2Cl2 in hexane (5:100, v/v); this afforded a dark green crystalline material of 1 (600 mg, 96 %). All the characterization perfectly matches with reported data.[12a] 1H NMR (300 MHz, CDCl3): d = 9.39 (br s, 4 H), 4.22–4.17 (t, J = 7.5 Hz, 4 H), 3.40–3.36 (t, J = 6.6 Hz, 8 H), 1.73–1.71 (m, 4 H), 1.57–1.48 (m, 8 H), 1.29–1.22 (m, 60 H), 0.89– 0.83 ppm (m, 18 H); 13C NMR (75 MHz, CDCl3): d = 166.0, 146.9, 116.9, 107.8, 45.0, 40.3, 31.8, 31.7, 30.3, 29.2, 29.1, 28.0, 27.3, 27.0, 22.6, 14.0 ppm; IR (KBr): n˜ = 3261, 2969, 2936, 2855, 1645, 1631, 1581, 1527, 1454, 1279, 1173, 1142, 1124, 847, 793, 720 cm 1; HRMS (ESI): m/z: calcd (%) for C62H106N6O4 998.8276; found: 999.8278 [M + H] + . Following similar conditions, cNDI-C12 (2) and cNDI-C16 (3) were prepared by reacting compound 4 with 6 and 7, which yields, respectively, 93 and 90 % of 2 and 3 as a green solids.
Spectroscopic data of 2 1
H NMR (300 MHz, CDCl3): d = 9.39 (br s, 4 H), 4.22–4.17 (t, J = 7.6 Hz, 4 H), 3.40–3.36 (t, J = 6.7 Hz, 8 H), 1.79–1.71 (m, 4 H), 1.57– 1.48 (m, 8 H), 1.29–1.22 (m, 92 H), 0.90–0.86 ppm (m, 18 H); 13C NMR (75 MHz, CDCl3): d = 165.9, 146.9, 116.9, 107.8, 45.0, 40.3, 31.9, 31.3, 29.6, 29.5, 29.4, 29.3, 28.3, 27.4, 27.2, 23.1, 22.5, 14.3, 14.2 ppm; IR (KBr): n˜ = 3263, 2968, 2937, 2853, 1642, 1631, 1579, 1526, 1456, 1280, 1175, 1150, 1126, 845, 796, 721 cm 1; elemental analysis: calcd: C 76.54, H 11.36, N 6.87; found: C 76.48, H 11.27, N 6.57; Maldi mass: m/z: calcd for C78H138N6O4 : 1224.08; found: 1224.10 [M] + .
Spectroscopic data of 3 1
H NMR (300 MHz, CDCl3): d = 9.39 (br s, 4 H), 4.22–4.17 (t, J = 7.6 Hz, 4 H), 3.40–3.36 (t, J = 6.6 Hz, 8 H), 1.78–1.68 (m, 4 H), 1.57– 1.48 (m, 8 H), 1.26–1.22 (m, 124 H), 0.91–0.86 ppm (m, 18 H); 13 C NMR (75 MHz, CDCl3): d = 165.9, 146.8, 116.9, 107.8, 45.0, 40.3, 31.9, 31.4, 29.6, 29.5, 29.4, 29.3, 28.3, 27.4, 27.2, 23.1, 22.5, 14.2, 14.1 ppm; IR (KBr): n˜ = 3263, 2968, 2937, 2853, 1642, 1631, 1579, 1526, 1456, 1280, 1175, 1150, 1126, 845, 796, 721 cm 1; elemental analysis: calcd: C 77.95, H 11.83, N 5.80; found: C 77.78, H 11.67, N 5.69; HRMS (ESI): m/z: calcd. for C94H170N6O4 : 1448.4320; found: 1448.4317 [M + H] + .
Acknowledgements Shesh.V.B. acknowledges the Australian Research Council for financial support under a Future Fellowship Scheme (FT110100152) and the RMIT Microscopy and Microanalysis Facility (RMMF). Sidhanath V. Bhosale is grateful for financial support from the CSIR-Intel Coat (CSC 0114) program. We also thank A. Gupta (CSIRO) and P. Reineck (Monash University) for AFM analysis.
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Keywords: core-substituted naphthalene diimides nanostructures · self-assembly · SEM · solvophobic control
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