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. 2025 Mar 24;5(4):1707–1716. doi: 10.1021/jacsau.4c01218

Direct Edge Functionalization of Corannulene–Coronene Hybrid Nanographenes

Jovana Stanojkovic †, Natalia Terenti ‡, Mihaiela C Stuparu †,‡,*
PMCID: PMC12042022  PMID: 40313849

Abstract

graphic file with name au4c01218_0008.jpg

For more than a century, electrophilic aromatic substitution reactions have been central to the construction of a rich variety of organic molecules that are useful in all aspects of human life. Typically, small aromatic nuclei, such as benzene, provide an ideal substrate. An increase in the number of annulated aromatic rings enhances the number of potential reactive sites and frequently results in complex product mixtures. Thus, nanographenes with a relatively large aromatic system are seldom selective in their substitution positions. Moreover, nanographene substrates with a scope for multiple substitution reactions and patterns remain rare. Herein, we demonstrate that a curved aromatic system based on a corannulene–coronene hybrid structure comprising 48 conjugated sp2-carbon atoms allows for direct and regioselective edge functionalization through bromination, nitration, formylation, and Friedel–Crafts acylation in good yields. The postsynthetically installed functional groups can be modified through versatile organic chemistry transformations, including (mechanochemical) Suzuki-Miyaura, Sonogashira-Hagihara, and Buchwald-Hartwig amination reactions. Furthermore, the substitutions can be carried out in a sequential manner to yield heterofunctional structures. The edge-functionalization strategy enables modular access to nanostructures with appealing properties, such as strong fluorescence emission in the visible and near-infrared regions (475–900 nm) with record Stokes shifts (>300 nm), at an exceptionally small carbon footprint (C48).

Keywords: corannulene, coronene, edge-functionalization, electrophilic aromatic substitutions, nanographenes, near-infrared emission, regioselective, stokes shifts

Introduction

Electrophilic aromatic substitutions are among the most important reactions in organic chemistry.1 For decades, these reactions have been essential in providing access to substituted aromatic compounds and enabling studies that facilitate an understanding of the fundamental principles of physical organic chemistry. Small aromatic nuclei represent perfect substrates for such reactions.1 However, the selectivity of substitution and the reaction scope both become severely limited in the case of polynuclear aromatic hydrocarbons (systems comprising >25 conjugated sp2-carbon atoms).2−11 Chlorination remains the most predominant substitution reaction performed directly on pristine nanographenes.2−11 Due to the absence of selectivity, perchlorination is carried out to avoid the formation of an inseparable product mixture with varying degrees of chlorination.12,13

Despite the limitations, direct modification of nanographenes is arguably the most effective approach for introducing substituents into the aromatic scaffold. An alternative approach is to install the substituents on the nanographene precursors.2−11 This strategy requires the development of separate synthetic routes for differently substituted nanographenes. More importantly, the scope of substituents is often restricted due to their instability or incompatibility under nanographene formation (graphitization) conditions. For instance, intramolecular oxidative cyclodehydrogenation, a prevalent graphitization reaction, could be deterred by steric hindrance or alteration of the electronic energy levels by the substitution.14−16 A second alternative is in situ functionalization of the nanographene scaffold.17−19 Here, graphitization and functionalization occur simultaneously. However, this approach relies on serendipity and thus remains limited only to chlorination17 and triflyloxylation.18,19 In contrast to these approaches, postsynthetic direct substitution on the bare nanographene edge has the advantage of synthetic simplicity, as a single route to the pristine nanographene is required. This pristine aromatic scaffold can then be transformed into targeted structures through substitution reactions. This approach, however, remains underexplored.12,13,20−28 This limitation is noteworthy as substituents are critical in governing the properties and, hence, applications of nanographenes. For instance, biological applications necessitate peripheral decoration with hydrophilic chains endowing water solubility to the carbon nanostructures.24 The alkyl chains, on the other hand, dictate the self-assembly behavior, which ultimately affects their performances in devices.29 Thus, explorations of direct edge-functionalization routes have become a significant research goal in nanographene chemistry. In this context, we report on a nanographene scaffold that exhibits a considerable scope for electrophilic aromatic substitution reactions. Furthermore, the reactions are regioselective and allow for the practical preparation of a library of edge-functionalized nanographenes beginning with a single pristine substrate. Bifunctional structures can also be obtained through sequential reactions. Multiple substitution patterns lead to a low optical bandgap and strong emissive properties in the visible to the near-infrared range. Typically, such characteristics are achieved by enlarging the aromatic scaffold.30 However, a loss in solubility and associated challenges in molecular characterization are difficulties encountered in this approach. This is exemplified by the quest to synthesize a soluble C222 structure (containing 222 conjugated sp2-carbon atoms), which was realized only recently.31,32 Addressing the nanographene edge thus has the advantage that appealing molecular characteristics can be attained at a much lower carbon number (C48 in the present case) with the benefits of high solubility and unambiguous structural elucidation.

Besides strong emission in the long-wavelength region to achieve deeper penetration and avoid scattering in biological tissue, another important optical characteristic is represented by the Stokes shift, the difference between the excitation and emission wavelengths. A large difference bodes well for biological imaging applications, as it minimizes crosstalk between the excitation source and observed emission and allows one to generate high-resolution images due to a high signal-to-noise ratio. Although great strides have been made recently in the preparation of emissive nanographene structures (entries 1–10, Table 1),24,33−44 a strong emission in the deep-red and near-infrared regions along with a large Stokes shift remains rare. Only the members of the helicene family, known to interact with light strongly,45−49 can achieve this with large systems comprising 124–186 annulated sp2-carbon atoms (entries 7–10, Table 1).41−44 On the other hand, commercially available fluorescent dyes with red and near-infrared emission, such as the rhodamine, boron dipyrromethene, and cyanine families, generally exhibit Stokes shifts below 30 nm, while state-of-the-art polycyclic aromatic hydrocarbons optimized for bioimaging purposes boast Stokes shifts in the range of 111–262 nm.50 In the present work (entry 11, Table 1), accessing long-wavelength emission with record-high Stokes shifts is achieved at an exceptionally small size. The chemistry is also modular, indicating adaptability of molecular structure to meet the requirements of a targeted application. Overall, therefore, this work demonstrates a broad scope for direct regioselective substitutions on the nanographene edge, opportunities for heterofunctionalizations, and the capacity to achieve attractive optoelectronic properties at a small carbon footprint.

Table 1. Examples of Known Highly Emissive Nanographenesab.

Entry Footprint Nanographene Φf bsλmax emλmax Stokes Shift
1 C38 Ovalenes33−36 67–89% 580–660 nm 600–670 nm <10 nm
2 C50 Thia-helicenes37 48% 400 nm 666 nm 266 nm
3 C68 Pyrene-helicenes I38 93% 538 nm 562 nm 24 nm
4 C76 Pyrene-helicenes II39 68% 592 nm 612 nm 20 nm
5 C80 Warped nanographenes24 37% 433 nm 528 nm 95 nm
6 C102 Aza-helicenes I40 32% 580 nm 588 nm 8 nm
7 C124 Aza-helicenes II41 28% 633 nm 770 nm 137 nm
8 C138 Extended helicenes I42 18% 510 nm 810 nm 300 nm
9 C144 Thia-helicenes II43 14% 630 nm 778 nm 148 nm
10 C186 Extended helicenes II44 34% 573 nm 733 nm 160 nm
11 C48 Corannulene–coronenes (this work) 1–82% 350–430 nm 510–695 nm 139–345 nm
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a

The carbon number (number of annulated sp2-carbon atoms) is shown as footprint.

b

This number represents the fundamental carbon scaffold without consideration for edge substituents.

Results and Discussion

Recently, we observed that a corannulene–coronene hybrid structure was chlorinated selectively (R = Cl, Scheme 1a) during an FeCl3-mediated Scholl reaction.17 A Density Functional Theory (DFT) calculation indicated that the positions adjacent to the newly formed bonds between the planar and the nonplanar segments exhibited the highest Fukui function (fk–) values.17 These positions, therefore, were anticipated to be the most receptive toward further reaction. This prompted us to examine the scope of electrophilic aromatic substitution reactions on the pristine nanographene structure 1 (Scheme 1b).17 For this, initially, bromination with the help of N-bromosuccinimide (NBS) as the brominating agent and boron trifluoride diethyl etherate (BF3·OEt2) as the source of Lewis acid was pursued. The reaction was carried out at room temperature and within minutes led to quantitative conversion to the bis-brominated product 2. 2D NMR using correlation spectroscopy (COSY) and nuclear Overhauser effect spectroscopy (NOESY) confirmed the regioselectivity of the substitution reaction (Figure 1).

Scheme 1. (a) Direct Transformation of Corannulene–Coronene Hybrid into Substituted Structures through Selective Electrophilic Aromatic Substitution Reactions on the Nanographene Edge. (b) (i) Bromination: NBS, BF3·Et2O, DCM, rt, 20 min; (ii) Nitration: HNO3, Ac2O, rt, 4 h; (iii) Formylation: Cl2CHOCH3, TiCl4, DCM, rt, 5 h; (iv) Acylation: CH3COCl, AlCl3, rt, 24 h.

Scheme 1

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Figure 1.

Figure 1

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(a) Chemical structure of 1, showing the COSY and NOESY interactions among different types of protons with the help of red and blue arrows, respectively. (b) Aromatic proton resonances for 1 (top) and 2 (bottom). (c) Chemical structure of 2, showing the interactions of COSY and NOESY among different types of protons with the help of red and blue arrows, respectively. (d) COSY spectra for 1. Inset shows the magnified area. (e) NOESY spectra for 1. (f) COSY spectra for 2. Inset shows magnified area. (g) NOESY spectra for 2.

Encouraged by the quantitative bromination, nitration using a nitric acid and acetic anhydride mixture was carried out. In 4–5 h of reaction time, bis-nitro and mononitro compounds 3a and 3b could be isolated in 54 and 13% isolated yields, respectively. A lowering of the reaction time and nitric acid content could be used to favor the monosubstitution to 31%. The Rieche formylation was carried out using dichloromethyl methyl ether acting as the formyl source and titanium tetrachloride (TiCl4) acting as the catalyst. This reaction led to the formation of aldehyde 4 in an 89% isolated yield. In contrast to bromination and nitration, the formylation stopped at monosubstitution, likely due to the mild nature of the electrophile and/or the deactivating nature of the aldehyde substituent. Finally, Friedel–Crafts acylation using AlCl3 and acetyl chloride at room temperature led to the formation of bis-acetyl 5a and monoacetyl 5b in isolated yields of 41 and 34%, respectively.

The direct electrophilic aromatic substitution reactions on 1 provided practical access to substituted nanographenes 2–5. Thus, further functional group transformations were targeted (Scheme 2). For this, initially, bis-brominated compound 2 was chosen. A cyanation with copper(I) cyanide (CuCN) led to an efficient transformation to bis-cyano compound 6. The introduction of electron-withdrawing cyano functionalities directly on the polyaromatic scaffold is seen as a rewarding task as it has the potential to dramatically enhance the electron acceptor properties of the curved aromatic systems.51,52 Thus, a clean transformation to 6 (98% isolated yield) was encouraging. The introduction of electron donors, on the other hand, is anticipated to enable a red-shift in the absorption spectrum. To achieve this goal, palladium-catalyzed Buchwald–Hartwig C–N cross-coupling lent itself to the installation of amines directly onto the aromatic scaffold in 52% isolated yield (7).53−55

Scheme 2. Functional Group Transformations.

Scheme 2

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(i) Rosenmund-von Braun reaction: CuCN, NMP, 210 °C, 2 h; (ii) Suzuki–Miyaura reaction: a) PhB(OH)2, Pd(P(t-Bu)3)2, CsF, dioxane, 80 °C, 72 h; b) Ball milling, 30 Hz, Pd(OAc)2, K2CO3, NaCl, 110 °C, 3 h; c) Ball milling, 30 Hz, Pd(OAc)2, K2CO3, PPh3, 125 oC, 1.5 h; (iii) Buchwald–Hartwig reaction: PhNH2, Pd(dppf)2Cl2·CH2Cl2, DPPF, NaOt-Bu, 130 °C, 72 h; (iv) Sonogashira–Hagihara reaction: Pd(PPh3)2Cl2, CuI, NEt3, THF, 100 °C, 3 h.

X-ray crystallography corroborated the regioselectivity conclusions based on the NMR data (Figure 2). These studies also indicated that bowl depth, defined by the distance between the centroid of the central five-membered ring and the mean plane of the ten carbon atoms of the rim, for nanographenes 8, 9, and 11 was approximately 1 Å (as compared to 0.87 Å of parental corannulene). In all cases, the molecules interacted via multiple π–π-stacking interactions through their planar aromatic surfaces.

Figure 2.

Figure 2

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(a,b) Top views of the X-ray crystal structure of 9, (c) side view, and (d,e) packing structures, along with aromatic stacking interactions between the planar regions of the nanographenes. Thermal ellipsoids were scaled at the 50% probability level. The hydrogen atoms, t-Bu groups, and solvent molecules are omitted for clarity.

Having installed the electron-withdrawing and electron-donating substituents directly onto the nanographene edge, a linker strategy was considered. For this, a palladium-catalyzed Suzuki–Miyaura reaction was carried out with commercially available boronic acid partners carrying electron-donating dimethylamino and electron-withdrawing cyano and ethyl ester functionalities having a phenyl linker (Scheme 2). These reactions provided targeted compounds 8–10 in 16–25% isolated yields. With established protocols for the mechanochemical Suzuki–Miyaura reaction, the product yields could be increased in all cases (37–65%).56−58 Further benefits of mechanochemistry59 involved the use of comparatively inexpensive palladium acetate as a catalyst, a much shorter reaction time, and the lack of a need for organic solvent to carry out the reaction.57 Thus, the next functionalization was carried out only with mechanochemistry and yielded acetyl compound 11 in 47% yield.

The Sonogashira–Hagihara reaction allowed for the installation of phenylene ethynylene groups using commercially available alkynes. Akin to 9 and 10, 12 and 13 carried cyano and ester groups. These compounds were isolated in 57 and 20% yields, respectively, and demonstrated the corannulene–coronene nanographene substrate to be a feasible partner in multiple metal-catalyzed coupling reactions.

In considering the introduction of electron-donating substituents into the system, an alternative approach would be to reduce the bis-nitro compound 3a to bis-amines. However, this transformation led to a complex product mixture that could not be separated. Thus, mononitro compound 3b was used instead and led to a successful reduction to monoamine 14 in an isolated yield of 91% (Figure 3a).

Figure 3.

Figure 3

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(a,b) Top views of the X-ray crystal structure of 15, (c) side view, and (d,e) packing structures along with aromatic stacking interactions. Thermal ellipsoids were scaled at the 50% probability level. Hydrogen atoms, t-Bu groups, and solvent molecules are omitted for clarity.

The monosubstituted structures offer the opportunity for introducing a second functional group as a reactive site remains available for a further substitution reaction. This avenue was explored with the help of compound 4 (Scheme 3b). The aldehyde group was first reduced with the help of sodium borohydride (15) and then masked with the help of the tert-butyldimethylsilyl (TBDMS) group (16). A nitration to 17 and removal of the protecting group furnished heterofunctional nanographene 18. These preliminary results suggest that the other monosubstituted structures (mononitro (3b), acyl (5b), and amine (14)) are potential precursors for a heterobifunctionalization strategy to further enhance molecular complexity and function. The X-ray crystal structure of 15 confirmed the regioselectivity of monofunctionalization (Figure 3).

Scheme 3. (a) Synthesis of Nanographene Amine through Reduction of the Nitro Group; (i) Reduction: HCOONH4, Pd/C, MeOH, 70°C, 3 days. (b) (i) Reduction: NaBH4, THF/MeOH, rt, 5 h; (ii) silylation: TBDMSCl, Imidazole, DCM, rt, 26 h; (iii) nitration: HNO3, Ac2O, rt, 24 h; (iv) desilylation: TBAF, THF, rt, 1.5 h.

Scheme 3

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The number and nature of the substituents had a significant impact on the optical properties (Table 2 and Figure 4). As anticipated, fluorescence emission was low for molecules carrying halogen atoms or nitro groups.60,61 Monoaldehyde showed broad emission within the 500–800 nm range with a quantum yield (Φf) of 11%. The placement of a ketone group increased Φf to 18%. The introduction of a second ketone further increased photoluminescence to 26%. Cyano substituents showed similarly high Φf (27%) in the yellow-red region. The placement of phenylamines retained this emission range with a Φf of 20%. The phenyl-linked systems exhibited emission in the red to near-infrared region (λedge = 900 nm) with a good Φf of 10–17%. An introduction of planar acetylene π-bridges led to materials with an excellent Φf of 65–82%. This observation was akin to the fluorenyl-2,7-ethynylene motif, which can be traced on the nanographene surface and is known to exhibit a quantum yield of unity, albeit in the UV range.62,63 The advantage of this motif in the nanographene setting thus leads to highly emissive materials in the red region. Finally, the TBDMS-carrying compound exhibited a Φf of 28%, the highest among nonacetylene structures.

Table 2. Absorbance and Emission Properties of the Nanographenes as Measured in Chloroform at Room Temperaturea.

  Absorbance
 Fluorescence
 Stokes Shift
Compound λmax (nm) Eg(opt) (eV)b λem (nm)c Φf (%)d nme (cm–1)f
Corg 290, 320 (sh)h 3.57 423, 437 0.80 147 (8370)
1 367, 387, 405 (sh), 457, 490 2.47 506, 530 (sh) 21.65 139 (646)
2 347 (sh), 370, 391, 412, 470, 500 2.35 650 0.08 280 (4620)
3a 315, 367, 405 (sh), 428, 520 2.19 680 0.8 313 (4525)
3b 315, 368, 387 (sh), 409, 470, 505 2.29 545, 660 0.73 177 (1450)
4 298, 350 (sh), 368, 386 (sh), 419, 475, 507 2.28 570 11.17 202 (2180)
5a 296, 350 (sh), 368, 390, 411, 467, 500 2.38 545 26.28 177 (1650)
5b 350 (sh), 368, 387, 408, 460, 495 2.43 533 18.22 165 (1440)
6 295, 350 (sh), 370, 407, 430, 500 (sh), 540 2.13 598, 646 (sh) 27.40 228 (1800)
7 355, 376, 420, 520 2.19 588 20.74 233 (2220)
8 350, 421, 496(sh), 550, 613 1.81 675 8.34 325 (1500)
9 350, 423, 550, 640 1.82 685 17.48 335 (1030)
10 335 (sh), 350, 423, 503, 550, 628 1.78 695 9.13 345 (1535)
11 297, 353 (sh), 370, 391, 413, 466, 496 2.35 525, 561 (sh), 685 16.83 155 (1110)
12 300 (sh), 353, 372, 405, 429, 535 2.13 573, 620 (sh) 65.53 201 (1240)
13 300 (sh), 352, 370, 406, 430, 531 2.11 579, 629 82.70 209 (1560)
14 354, 370, 388, 409, 470, 505 2.29 555 13.53 185 (1780)
15 350 (sh), 368, 386, 412, 460, 490 2.44 510, 545 (sh) 18.01 142 (801)
16 340 (sh), 368, 388, 405, 458, 490 2.45 510, 538 (sh) 28.63 142 (801)
17 315, 368, 388, 412, 470, 505 2.29 513, 548 (sh), 665 (sh) 3.03 145 (308)
18 315, 368, 390, 413, 470, 503 2.29 660 0.42 292 (4730)
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a

The wavelength in bold indicates the major signal.

b

Calculated from the long-wavelength absorption edge (Eg(opt) = 1240/λonest).

c

Obtained by exciting each absorption maximum.

d

Calculated using integration sphere (conc ∼6 × 10–6).

e

Stokes shift in nm is calculated as the difference between absorption and emission maxima.53

f

Stokes shift in cm–1 is calculated as the difference between lowest energy absorption band and emission maximum.

g

Cor = corannulene.

h

sh = shoulder.

Figure 4.

Figure 4

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UV–vis absorption and fluorescence emission of 3a underlining Stokes shifts typical in the present family of nanographenes (left). Emission spectra of some of the nanographenes highlight spectral tunability (right).

The versatility of the current emissive nanographene family is similar to ovalenes, which have found great success as fluorescent probes in biology.33−36 The ovalenes (λedge = 800 nm) display higher quantum yields, but their Stokes shifts are limited to only a few nanometers. In comparison, the current materials are significantly red-shifted (λedge = 900 nm) and display the largest Stokes shifts (>300 nm), calculated in accordance with Xie and Finney,53 known thus far. Typically, Stokes shifts are given in cm–1 as the distance between the lowest energy absorption and λmax of emission. However, we have emphasized the difference between λmax of absorption and λmax of emission in nm, as in bioimaging applications the excitation does not have to be at the lowest energy wavelength. To maximize the difference between the excitation and the emission wavelengths, as described in the introduction, sample excitation can be carried out at the λmax of absorption. Overall, thus, the current materials are expected to lead to emissive probes for high-resolution bioimaging applications. To achieve the water solubility necessary for such purposes, a transesterification reaction of 9 with polyethylene glycol monomethyl ether or the use of a polyethylene glycol-based aryl boronic acid as a coupling partner with 2 can be envisaged. This molecular pliability is also a feature that distinguishes the current concept from helicenes,41−44 which are extraordinary in their structure and function but lack versatility (in terms of structural adaptability), helicenes (entries 7–10, Table 1) belong to the first alternative described in the Introduction).

Conclusion

In summary, a corannulene–coronene hybrid structure is shown to be receptive toward multiple electrophilic aromatic substitution reactions at the nanographene edge. The substitutions are direct, selective, and yield good results . Thus, a new family of precisely functionalizable nanostructures can be accessed in a practical manner from a single substrate. The functionalizations can be sequential, thus allowing for the formation of heterofunctional structures. The structures exhibit edge-dependent optical properties that can be modulated through simple functional group transformations. In some cases, the emission extends into the near-infrared region. The results indicate that attractive optoelectronic properties, which are often accessed by enlarging the number of aromatic annulations and encountering typical solubility and characterization problems, can be achieved with a small carbon footprint, offering the advantages of high solubility and unambiguous characterization through molecular engineering at the nanographene edge. Since the chemistry is modular, edge functionalization with electron-rich and -deficient heterocycles carrying nitrogen, chalcogens, silicon, and boron can be envisaged to further gain a change in absorption and emission range and quantum yields. The ability to heterofunctionalize could lead to the placement of donor/acceptor substituents at the nanographene edge. The placement of cationic groups at the aryl substituents could potentially bring specific cellular uptake properties, such as the mitochondria-targeting capacity of phosphonium or the antibacterial capacity of ammonium and sulfonium salts. In these cases, the inherent optoelectronic properties can be used to image and track the location of the nanographene, as well as potentially generate reactive oxygen species24,31,64 for therapeutic purposes, thus leading to a new family of nanographene-based theragnostic materials.

Methods

The pristine nanographene was obtained through palladium-catalyzed dichlorination in an inert atmosphere in tetrahydrofuran in the presence of potassium carbonate and triphenylphosphine at 80 °C for a period of 5 h. The reaction mixture was filtered through a short pad of silica gel and washed with dichloromethane. The filtrate was concentrated under reduced pressure, and the crude residue was purified by flash chromatography using hexane and dichloromethane (9:1) as the eluent to furnish 1 in 99% isolated yield as an orange–yellow solid. This material was then used for further nanographene modification studies.

Acknowledgments

This work was financially supported by the Ministry of Education, Singapore, under the AcRF Tier 2 (MOE-T2EP10221-0002) and by the Ministry of Research, Innovation and Digitalization under Romania’s National Recovery and Resilience Plan PNRR–III-C9-2022–I8 program with Project code 167/15.11.22.

Data Availability Statement

The data that support the findings of this study are available in the Supporting Information of this article.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacsau.4c01218.

  • Details on experimental procedures, characterization data, mass spectra, NMR spectra, X-ray crystallography data, and optical spectra of all the compounds(PDF)

  • Crystal data of 8(PDF)

  • Crystal data of 9(PDF)

  • Crystal data of 11(PDF)

  • Crystal data of 15 (PDF)

Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

The authors declare no competing financial interest.

Supplementary Material

au4c01218_si_001.pdf (15.5MB, pdf)
au4c01218_si_002.pdf (101.3KB, pdf)
au4c01218_si_003.pdf (96KB, pdf)
au4c01218_si_004.pdf (170.1KB, pdf)
au4c01218_si_005.pdf (125.8KB, pdf)

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

au4c01218_si_001.pdf (15.5MB, pdf)
au4c01218_si_002.pdf (101.3KB, pdf)
au4c01218_si_003.pdf (96KB, pdf)
au4c01218_si_004.pdf (170.1KB, pdf)
au4c01218_si_005.pdf (125.8KB, pdf)

Data Availability Statement

The data that support the findings of this study are available in the Supporting Information of this article.

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