Time- and Solvent-Dependent Self-Assembly of ... - ACS Publications

Article Cite This: J. Phys. Chem. C XXXX, XXX, XXX-XXX

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Time- and Solvent-Dependent Self-Assembly of Photochromic Crystallites Mariacristina Gagliardi,*,†,‡ Francesca Pignatelli,† and Virgilio Mattoli*,† †

Center for Micro Bio-Robotics @SSSA, Istituto Italiano di Tecnologia, viale Rinaldo Piaggio, 34, 56025 Pontedera, Italy MUSAM Multi-Scale Analysis of Materials, IMT School for Advanced Studies Lucca, piazza San Francesco, 19, 55100 Lucca, Italy

‡

S Supporting Information *

ABSTRACT: Molecular self-assembly provides complex structures and enables the tuning of system features on the nanoscale. Guided assembly, induced by external stimuli, gives hierarchical but static arrangements, limiting the exploitation in several fields. A dynamic arrangement can confer improved and smarter properties, but adaptive self-assembly requires new molecules and the knowledge of kinetics effects. The interest in adaptive self-assembly is constantly growing and comprises environmental-, chemical-, and field-adaptive molecules. Thus reversible adaptive self-assembly systems, which can be build and destroyed for several times, attract large attention. To contribute in this field, we report the particular post-solvato-control on solid habit morphology of the vinyl-terminated spiropyran derivative named 1-(5-hexenyl)3,3-dimethyl-6′-nitro-1,3-dihydrospiro[2H-indole-2,2′-[2H][1]benzopyran. For this molecule, the formation of supramolecular structures is solvent- and time-governed and exhibited reversible isomerization upon UV irradiation. We observed different solid habits by varying solvent polarity as well as an increasing degree of arrangement with time. Light-induced precipitation in nonpolar solvent afforded spherical merocyanine aggregates under mild conditions. This example of kinetics-controlled photochromic system has the potential to drive toward adaptive and dynamic self-assembly systems, with application in material science and for polymer functionalization.

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INTRODUCTION The repeating organization of any-size units in complex structures is widely diffused in the nature.1 On the atomic and molecular scales, assembly provides micro- or nanosystems in which atoms or molecules are arranged in specific spatial order that gives a repeating pattern. Atoms or molecules can self-assemble spontaneously or under external stimuli,2,3 guided by molecular machines,4,5 or exploiting particular interface properties.6 Guided assembly is often the only way to prepare structures that are unachievable via spontaneous thermodynamic processes. Molecular assembly is also a valid bottom-up approach to scale-down the system features.7 Adaptive self-assembly is typical of natural systems,8 allowing the majority of life activities. Synthetic adaptive self-assembling systems respond to pH,9−11 temperature,12,13 moisture,14,15 chemicals,16−18 light,19 or mechanical stimuli.20,21 Obtained systems are regulated by intermolecular noncovalent interactions,22 giving robust systems. Final products can change their structure and functionalities after environment adaptation. The noncovalent nature of the self-assembly makes systems reversible and adaptive to a multitude of stimuli. Adaptivity and reversibility increase system potential, which are suitable for several applications requiring smart properties. Molecular aggregation in solution is the consolidate technique exploited in particle and micelle preparation.23,24 Besides solvent-guided molecular assembly, interfacial assembly © XXXX American Chemical Society

is a valid approach to obtain complex structures, such as crystalline monolayers25 or membranes.26,27 Assembly in the solid state is less common, and there is a need for molecules that change their properties (e.g., conformation, dipole moment, or charge) without changing their physical state. Photoresponsive molecules are compounds that isomerize after UV or vis-light irradiation. Photoresponsive spiropyrans isomerize via the reversible heterolytic cleavage/rebinding of the spiro C−O bond upon UV/white-light exposure. The structural isomerism of spiropyrans consists of the switch from the closed (spiropyran, SP) to the open form (merocyanine, MC). The isomerization SP-to-MC under UV light gives a planar molecule;28 it is associated with changes of color29 and dipole moment, from 4 to 6 D to 14−18 D.30 MC can provide a zwitterionic or a quiniodal forms; the latter is favored in nonpolar solvents.31 Krongauz and coworkers reported, for the first time, the formation of globular quasi-crystals from SP derivatives solutions after UV exposure or under the effects of an electric field.32−34 More recently, larger quasi-crystals were produced with a prolonged UV exposure35 or in spiropyran-functionalized polymers.36 Cited works demonstrated that spiropyrans can assemble in solutions, giving spheroidal aggregates. A Received: June 29, 2017 Revised: October 9, 2017 Published: October 10, 2017 A

DOI: 10.1021/acs.jpcc.7b06388 J. Phys. Chem. C XXXX, XXX, XXX−XXX

Article

The Journal of Physical Chemistry C

Scheme 1. Isomerism of the Synthesized Vinyl-Terminated SP Derivative: Closed (left), Zwitterionic (center), and Quiniodal (right) Forms

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EXPERIMENTAL SECTION The photochromic molecule was the vinyl-terminated spiropyran derivative named 1-(5-hexenyl)-3,3-dimethyl-6′nitro-1,3-dihydrospiro[2H-indole-2,2′-[2H][1] benzopyran. Isomerization reaction, with the closed form and the open (zwitterionic and quiniodal) form, are illustrated in Scheme 1. General Experiments. NMR spectra were acquired on a Bruker Avance 400 MHz spectrometer; samples (10 mg mL−1) were dissolved in CDCl3 and analyzed at fixed temperature (27 °C). MS analysis was performed with an AbSciex 3200 QTRAP mass spectrometer, the samples were dissolved in acetonitrile/ formic acid 100/0.1 v/v, ion spray voltage: 5000 V, source temperature 350 °C, declustering potential 50 V, ion source gas: 25 L min−1, curtain gas: 25 L min−1, and the m/z ratio was monitored between 100 and 700 Da. UV−vis absorption spectra were recorded on a PerkinElmer LAMBDA 650; solvents used were all spectroscopic grade, and sample concentration was 0.05 mg mL−1 (0.13 mol mL−1). UV irradiation was performed by a UV source Hamamatzu LightningCure LC5 equipped by a light guide, introduced in the spectrometer chamber. The distance between the light guide and the sample was 6 cm. DSC thermograms were recorded on a Mettler Toledo DSC1 apparatus in the temperature range from 10 to 160 °C at a ramp rate of 10 °C min−1, and the analysis was performed in Al sealed capsules. Crystallization kinetics was evaluated on samples (0.5 ± 0.3 mg) casted on flat glass supports in the dark from five solvents (n-hexane, diethyl ether, tetrahydrofuran, methanol, and acetonitrile, 0.25 mg mL−1) with increasing polarity index, which represents a relative measure of the solvent interactions degree with several polar test solutes. Samples were analyzed by SEM, with an EVO ZEISS apparatus. Melting enthalpy was calculated by DSC thermograms in the first heating scan. HPLC chromatograms were acquired on a Shimadzu Prominence HPLC chromatograph, equipped by a photodiode array; the column was a Luna C8 (Phenomenex) thermostated at 30 °C, and acetonitrile/water (60/40 v/v) was used as mobile phase with an internal flow of 0.8 mL min−1. Values of absorbance for the quantitative analysis were acquired at 350 nm. Samples (20 μL) were withdrawn from the supernatant of the n-hexane solutions, added to a glass vial and evaporated, then dissolved in methanol (1 mL) for the chromatographic analysis. Data elaboration was obtained upon a calibration curve in the range of concentrations 0.16−2.56 μmol mL−1. Movies were recorded by a 3D digital microscope Hirox. Synthesis of Spiropyran Derivative. Reactants and solvents for syntheses were commercially available from Sigma-Aldrich and used as received. 2,3,3-Trimethylindolenine (12.7 mmol) and 6-bromo-1-hexene (11.9 mmol) were

further step in spiropyran assembly was reported by Florea et al.37 In their work, they described the spontaneous formation of SP aggregates at the air/solvent interface, using water/ethanol mixtures as liquid phase. The process lead to the formation of well-organized 3D daisy-like structures, tunable in size with solvent composition. In cited works, aggregation is not spontaneous but is triggered by an external factor. Induced isomerization is the key factor for aggregation, giving partially stable structures. Reported works do not exploit the dynamic spiropyran/ merocyanine equilibrium in the absence of the guiding stimulus, while intrinsic characteristics of spiropyran derivatives could be exploited in the preparation of adapting aggregates. Adaptivity is the key factor to fill the gap between properties of artificial and natural self-assembly systems, serving to tune features on the nano- or microscale. From this point of view, a deeper knowledge of assembly kinetics is fundamental38 and new tools are continuously developed to monitor this aspect.39,40 Spiropyran isomerism enables the use of this class of molecules in relevant technological applications. As an example, the dipole moment increase after isomerization to merocyanine can be exploited in organic electronics.41 Main applications of SPs and their derivatives in this field are related to the preparation of organic field-effect transistors (OFETs), providing phototunable behavior, in combination with other active polymers.42,43 Here we report the solvent- and time-dependent formation of SP structured aggregates in solid state. We successfully tuned solid habits, preparing samples by casting from different-polarity solvents. Obtained structures encompassed flat lamellae, filaments, daisy-like, and cilia-like structures. Solid structures were dynamic, and their degree of organization increased with time. Hierarchical organization was reversible upon UV irradiation and recovered after storage in the dark. To the best of our knowledge, similar structures and solvent memory have never been reported in the literature. Final structures were definitely different from quasi-crystals reported by Krongauz et al., in dimension and complexity of the structure. They were also different from daisy-like structures reported by Florea et al., where formation was not controlled by kinetics. This study provides a visual measurement of the SP tendency to form supramolecular structures, together with a quantitative measure of the time-dependent kinetics by means of thermal analysis. B


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The Journal of Physical Chemistry C dissolved in acetonitrile (10 mL) and refluxed (T = 70 °C) for 24 h. After being cooled to room temperature, the reaction mixture was suspended in n-hexane, and a dark-red/brown oil (1) was obtained following exsiccation at room temperature under vacuum for 2 h. The yield in weight after purification was ∼80% (3.5 g of product, corresponding to 14.5 mmol). 1H NMR (Figure S1) H (400 MHz, CDCl3): 7.96 (1H, C-5H), 7.61 (1H, C-7H), 7.56 (1H, C-6H), 6.50 (1H, C-4H), 5.74 (1H, N(CH2)4CHCH2), 5.06 (1H, CH− cis), 5.02 (1H,  CH− trans), 3.14 (2H, NCH2(CH2)3CHCH2), 2.15 (N(CH2)3CH2CHCH2), 1.53 (−CH3), 1.26 (NCH2(CH2)2CH2CHCH2). 13C-DEPT135-NMR (Figure S2): 122.51 (C-5), 115.17 (C-7), 129.94 (C-6), 123.17 (C4), 137.10 (N(CH2)4CHCH2), 115.85 (CH−), 49.39 (NCH 2 (CH 2 ) 3 CHCH 2 ), 32.80 (N(CH 2 ) 3 CH 2 CHCH 2 ), 25.69−27.12 (NCH2(CH2)2CH2CHCH2), 23.02 (−CH3). Product 1 was dissolved in ethanol (10 mL) and treated with a KOH water solution 1.4 M (10 mL). The suspension was maintained under stirring at room temperature for 30 min; then, the product was extracted with diethyl ether. The organic layer was casted under vented hood at room temperature, affording the product 2 as a purple oil. Product 2 was dissolved in ethanol (50 mL) together with 2-hydroxy-5-nitrobenzaldehyde (15 mmol) and refluxed (T = 70 °C) for 16 h, giving the product 3. After cooling to room temperature, the final product was precipitated in n-hexane, forming a dark-red/purple powder. The yield after purification was ∼50% (3 g, corresponding to 7.7 mmol); part of the product solubilized in the extraction phase, and thus it was casted and extracted twice, and an additional 2.6 mmol (1 g) was recovered with a final yield of 67%. Melting point: 87.6 °C. 1H NMR (Figure S3) H (400 MHz, CDCl3): 8.56 (1H, C-5H), 8.53 (1H, C-7H), 7.99 (1H, C-4H), 7.12 (1H, C-5H), 6.88 (1H, C-7H), 6.84 (1H, C-8H), 6.75 (1H, C-6H), 6.58 (1H, C-4H), 5.87 (1H, C3H), 5.74 (1H, N(CH2)4CHCH2), 4.99 (1H, CH− cis), 4.94 (1H, CH− trans), 3.14 (2H, NCH2(CH2)3CHCH2), 2.04 (N(CH 2 ) 3 CH 2 CHCH 2 ), 1.64 (−CH 3 ), 1.26 (NCH2(CH2)2CH2CHCH2). 13C-DEPT135-NMR (Figure S4): 126.16 (C-5), 125.80 (C-7), 127.35 (C-4), 119.37 (C5), 112.90 (C-7), 123.00 (1H, C-6), 123.00 (C-4), 118.36 (N(CH2)4CHCH2), 116.15 (CH2), 47.50 (NCH 2 (CH 2 ) 3 CHCH 2 ), 32.82 (N(CH 2 ) 3 CH 2 CHCH 2 ), 25.76−25.79 (NCH2(CH2)2CH2CHCH2), 21.73 (−CH3). Assignments were confirmed, for the final product, with 2D NMR spectra (Figures S5 and S6). EMS (ESI+) C24H26N2O3, expected 390.5 Da, found 391.2 Da (Figures S7 and S8). Calculation of Keq. Equilibrium constant Keq is expressed as

Keq =

[MC] [SP]

nonpolar solvents (n-hexane, diethyl ether, and tetrahydrofuran).

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RESULTS AND DISCUSSION The ratio merocyanine/spiropyran in solution increased with solvent polarity (Table 1, Figure S9), confirming that the Table 1. Used Solvents, Polarity Indexes (PIs),45 and Equilibrium Constants (Keq) from UV Measurementsa

ϵ

× × × × ×

10−4 10−4 10−4 10−4 10−3

± ± ± ± ±

1.84 5.50 1.58 4.40 1.99

× × × × ×

10−5 10−5 10−4 10−4 10−3

variety of equilibrium constants and the solvatochromic behavior of the SP derivative (Figure S10) can affect molecule organization during casting. SP solutions were slightly colored after the immediate solubilization at room temperature (Figure S10b1), without any particular solvatochromic effect. After exposure to white light (WL, 60 s) samples did not significantly vary (Figure S10a1), while under UV light, SP moved to MC form (Figure S10c1) with notable changes of color and the formation of a visible precipitate in the n-hexane solution. UV spectra confirmed the presence of small fractions of MC in the equilibrium solutions (Figure S10b2), in particular, in polar solvents, whereas the weak signal characteristic of MC completely disappeared after WL exposure (Figure S10a2). Spectra of UV-exposed samples (Figure S10c2) showed a marked hypsochromic shift, with peak values of λ that decreased by increasing the polarity index of the solvent (Figure S10d). The marked solvatochromism of the MC isomer enables the use of SP derivatives as potential UV-induced polarity probe.44 After solvent casting, morphological analysis by SEM recorded only oily like unstructured depositions (Figure 1, day 0). We maintained prepared samples in the dark and repeated the morphological analysis for 1 week every 24 h. Samples progressively increased their degree of organization, giving crystallites with differentiated habits (Figure 1, days 1, 4, and 7). Whereas the concentration of the starting solution in each solvent did not affect habit formation (data not shown), solvent polarity affected the shape of obtained structures: The less polar solvent (n-hexane) afforded large and thin petal-like structures, whereas increasing solvent polarity structures progressively become more narrow and thicker, tending to filamentous structures in more polar solvents (methanol and acetonitrile). As a general rule, length and width tended to increase with time, with the exception of samples obtained from tetrahydrofuran. Samples formed large aggregates at early times, whereas bunches of lamellae tended to coalescence at late times. Shape ratios, evaluated as length/width, ranged from approximately 2 (sample casted from n-hexane) to 10 (sample casted from methanol). Morphological structure complexity increased over time, producing larger aggregation areas. The kinetics of supramolecular rearrangement was quantitatively studied by thermal analysis. We monitored melting enthalpy variation over time, detecting a progressive increase in

(1)

(λmax )l[SP]0 − A(λmax )

Keq 1.05 1.50 3.01 7.15 1.50

High standard deviations are attributed to the variable temperature, between 25 and 35 °C, in the UV chamber.

A(λmax ) MC

PI 0.0 2.8 4.0 5.1 5.8

a

where [MC] and [SP] are molar concentrations of the species at the equilibrium. Introducing the Lambert−Beer equation and considering that [SP] = [SP]0 − [MC], we obtain Keq =

solvent n-hexane diethyl ether tetrahydrofuran methanol acetonitrile

(2)

In this equation, A(λmax) is the value of absorbance at the maximum peak wavelength, ϵMC(λmax) is the molar extinction coefficient of the MC isomer at the maximum peak wavelength, and l is the optical path. According to the literature,40 molar extinction coefficient was fixed to 35 000 M−1 cm−1 for polar solvents (methanol and acetonitrile) and 52 000 M−1 cm−1 for C


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Figure 1. Morphological analysis of samples, casted by different solvents, after increasing times.

Figure 2. Thermal analysis: (a) Melting enthalpy variation of samples obtained from different solvents versus times. (b) Thermograms acquired after different times (solvent: acetonitrile).

this parameter in all cases, except for samples obtained from nhexane. A correlation with solvent polarity arose after only 5 days, whereas no particular correlations were found at earlier times (Figure 2a). Melting enthalpy is related to the energy requested to decompose the supramolecular structure. Its increment confirmed the time-dependency of self-assembly. We studied the effect of UV on solid crystallite habits. Solid samples showed a color change upon UV irradiation, confirming that isomerization also occurred in the solid state. Isomerization destroyed the supramolecular organization (Figure 3), but UV effect was reversible and structuring was recovered after 24 h of storage in the dark.

The formation of solid crystallites did not exclude the formation of aggregates in solution. Thus, we evaluated the tendency and the kinetics of the SP derivative to form aggregates in solution under UV irradiation. Quasi-crystal formation reported by Krongauz and coworkers occurred at low temperatures and upon the effect of UV and electric fields. In our case, we observed a simple and fast aggregation in spherical particles (mean diameter: 0.62 ± 0.2 μm) at room temperature and in a few seconds in n-hexane. The fine hydrophilic/hydrophobic balance obtained with the selected alkyl (hydrophobic) spacer provided this mild procedure. Aggregate precipitation kinetics (Figure 4a) reported the halving of SP concentration in solution after 15 s of UV D


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Figure 3. Effect of UV exposure on habits of supramolecular structures obtained from SP solutions in different solvents.

Figure 4. Aggregate formation in solution: (a) Precipitation kinetics, evaluated by HPLC analysis. (b) SEM analysis of solid precipitates. Dissolution of precipitates in acetone (c) after recovery from n-hexane and (d) after 60 s from dissolution.

exposure (photon dose 1.32 × 10−5 E s−1) and a 90% decrease after 90 s. Recovered dark-blue solid was sphere-shaped (Figure 4b) and was stable for several weeks. Aggregates were dissolved in acetone, giving a colored solution (Figure 4c). The color vanished in a few tens of seconds (Figure 4d), confirming that aggregates obtained under UV irradiation were composed of MC molecules.

prepared and used in the manufacture of organic capacitors. Electrical behavior of obtained capacitors exploited the SP derivative isomerization also in solid state: It depended on the storing time in the dark and was tuned by modulating UV exposure and temperature. In a future work, we will demonstrate the use of our molecular switch in RFID devices, exploiting the discussed kinetics effects in light-triggered organic capacitors.

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CONCLUSIONS The proposed spiropyran derivative is a valid candidate for kinetic-governed self-assembly. Morphology of crystallites depended on the polarity of the solvent used for sample preparation. Different habit formation can be attributed to the variable equilibrium merocyanine/spiropyran in the starting solution, which changes by increasing solvent polarity. Habits evolved with time, giving more structured crystallites that required higher energies to be thermally destroyed. UV exposure provided the isomerization reaction also in solid state, causing habit destruction. On the contrary, molecules recovered the hierarchical organization after storing in the dark. The proposed derivative was also able to form sphere-shaped aggregates in solution under UV irradiation. Aggregation kinetics was faster and simpler than that reported in the literature. Solid aggregates were stable for a long time in the dark and did not lose their reversible isomerization when dissolved. The vinyl functional group paves the way for the use of our spiropyran derivative as comonomer for the synthesis of photoactive polymers, with potential applications in organic electronics. SP-functionalized copolymers were successfully

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpcc.7b06388. NMR spectra of intermediate 1 and final product (1H, 13 C-DEPT135, 1H-1H-COSY, and 13C-1H-COSY). Keq versus polarity index. Solvatochromic behavior in different solvents. (PDF) Crystallite nucleation in n-hexane (movie). Solid aggregate precipitation in n-hexane (movie). (ZIP)

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AUTHOR INFORMATION

Corresponding Authors

*M.G.: E-mail: [email protected]. *V.M.: E-mail: [email protected]. ORCID

Mariacristina Gagliardi: 0000-0002-5860-3141 Virgilio Mattoli: 0000-0002-4715-8353 Notes

The authors declare no competing financial interest. E


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(20) Raeburn, J.; Cardoso, A. Z.; Adams, D. J. The Importance of the Self-Assembly Process to Control Mechanical Properties of Low Molecular Weight Hydrogels. Chem. Soc. Rev. 2013, 42, 5143−5156. (21) Chen, X.; Smith, N. M.; Iyer, K. S.; Raston, C. L. Controlling Nanomaterial Synthesis, Chemical Reactions and Self Assembly in Dynamic Thin Films. Chem. Soc. Rev. 2014, 43, 1387−1399. (22) Wang, A.; Shi, W.; Huang, J.; Yan, Y. Adaptive Soft Molecular Self-Assemblies. Soft Matter 2016, 12, 337−357. (23) Fetsch, C.; Gaitzsch, J.; Messager, L.; Battaglia, G.; Luxenhofer, R. Self-Assembly of Amphiphilic Block Copolypeptoids − Micelles, Worms and Polymersomes. Sci. Rep. 2016, 6, 33491. (24) Lau, K. H. A.; Castelletto, V.; Kendall, T.; Sefcik, J.; Hamley, I. W.; Reza, M.; Ruokolainen, J. Self-Assembly of Ultra-Small Micelles from Amphiphilic Lipopeptoids. Chem. Commun. 2017, 53, 2178− 2181. (25) Castelli, A.; de Graaf, J.; Prato, M.; Manna, L.; Arciniegas, M. P. Tic-Tac-Toe Binary Lattices from the Interfacial Self-Assembly of Branched and Spherical Nanocrystals. ACS Nano 2016, 10, 4345− 4353. (26) Oh, S.; Yang, M.; Bouffard, J.; Hong, S.; Park, S. J. AirLiquid Interfacial Self-Assembly of Non-Amphiphilic Poly(3-hexylthiophene) Homopolymers. ACS Appl. Mater. Interfaces 2017, 9, 12865−12871. (27) Coelho, J. P.; Mayoral, M. J.; Camacho, L.; Martín-Romero, M. T.; Tardajos, G.; López-Montero, I.; Sanz, E.; Á vila Brande, D.; GinerCasares, J. J.; Fernández, G.; Guerrero-Martínez, A. Mechanosensitive Gold Colloidal Membranes Mediated by Supramolecular Interfacial Self-Assembly. J. Am. Chem. Soc. 2017, 139, 1120−1128. (28) Piantek, M.; Schulze, G.; Koch, M.; Franke, K. J.; Leyssner, F.; Krüger, A.; Navío, C.; Miguel, J.; Bernien, M.; et al. M. W. Reversing the Thermal Stability of a Molecular Switch on a Gold Surface: RingOpening Reaction of Nitrospiropyran. J. Am. Chem. Soc. 2009, 131, 12729−12735. (29) Nuernberger, P.; Ruetzel, S.; Brixner, T. Multidimensional Electronic Spectroscopy of Photochemical Reactions. Angew. Chem., Int. Ed. 2015, 54, 11368−11386. (30) Klajn, R. Spiropyran-Based Dynamic Materials. Chem. Soc. Rev. 2014, 43, 148−184. (31) Brieke, C.; Rohrbach, F.; Gottschalk, A.; Mayer, G.; Heckel, A. Light-Controlled Tools. Angew. Chem., Int. Ed. 2012, 51, 8446−8476. (32) Krongauz, V. A.; Fishman, S. N.; Goldburt, E. S. Quasi-Crystals Growth from Photochromic Spiropyrans on Irradiation in a Constant Electric Field. J. Phys. Chem. 1978, 82, 2469−2474. (33) Krongauz, V. A.; Goldburt, E. S. Quasi-Crystals from Irradiated Photochromic Dyes in an Applied Electric Field. Nature 1978, 271, 43−45. (34) Shvartsman, F. P.; Cabrera, I. R.; Weis, A. L.; Wachtel, E. J.; Krongauz, V. A. Investigation of the Quasi-Liquid Crystal Structure. J. Phys. Chem. 1985, 89, 3941−3946. (35) Onai, Y.; Mamiya, M.; Kiyokawa, T.; Okuwa, K.; Kobayashi, M.; Shinohara, H.; Sato, H. Colored Merocyanine Aggregates: Long Lived Crystals of Large Size (10−100.mu.m) and Deaggregation of Small Aggregates in Solutions. J. Phys. Chem. 1993, 97, 9499−9505. (36) Kotharangannagari, V. K.; Sánchez-Ferrer, A.; Ruokolainen, J.; Mezzenga, R. Photoresponsive Reversible Aggregation and Dissolution of Rod-Coil Polypeptide Diblock Copolymers. Macromolecules 2011, 44, 4569−4573. (37) Florea, L.; Scarmagnani, S.; Benito-Lopez, F.; Diamond, D. SelfAssembled Solvato-Morphologically Controlled Photochromic Crystals. Chem. Commun. 2014, 50, 924−926. (38) Fukui, T.; Kawai, S.; Fujinuma, S.; Matsushita, Y.; Yasuda, T.; Sakurai, T.; Seki, S.; Takeuchi, M.; Sugiyasu, K. Control Over Differentiation of a Metastable Supramolecular Assembly in One and Two Dimensions. Nat. Chem. 2016, 9, 493−499. (39) Tantakitti, F.; Boekhoven, J.; Wang, X.; Kazantsev, R. V.; Yu, T.; Li, J.; Zhuang, E.; Zandi, R.; Ortony, J. H.; Newcomb, C. J.; Palmer, L. C.; Shekhawat, G. S.; de la Cruz, M. O.; Schatz, G. C.; Stupp, S. I. Energy Landscapes and Functions of Supramolecular Systems. Nat. Mater. 2016, 15, 469−476.

ACKNOWLEDGMENTS This work was funded by the Istituto Italiano di Tecnologia. We acknowledge Dr. Giovanni Signore (Laboratorio NEST, Scuola Normale Superiore, Pisa) for providing the mass spectroscopic analysis.

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REFERENCES

(1) Thiruvengadathan, R.; Korampally, V.; Ghosh, A.; Chanda, N.; Gangopadhyay, K.; Gangopadhyay, S. Nanomaterial Processing Using Self-Assembly-Bottom-Up Chemical and Biological Approaches. Rep. Prog. Phys. 2013, 76, 066501. (2) Kundu, P. K.; Samanta, D.; Leizrowice, R.; Margulis, B.; Zhao, H.; Börner, M.; Udayabhaskararao, T.; Manna, D.; Klajn, R. LightControlled Self-Assembly of Non-Photoresponsive Nanoparticles. Nat. Chem. 2015, 7, 646−652. (3) Packwood, D. M.; Han, P.; Hitosugi, T. Chemical and Entropic Control on the Molecular Self-Assembly Process. Nat. Commun. 2017, 8, 14463. (4) Meng, W.; Muscat, R. A.; McKee, M. L.; Milnes, P. J.; El-Sagheer, A.; Bath, J.; Davis, B. G.; Brown, T.; O’Reilly, R. K.; Turberfield, A. J. An Autonomous Molecular Assembler for Programmable Chemical Synthesis. Nat. Chem. 2016, 8, 542−548. (5) Wang, X.; Miller, D. S.; Bukusoglu, E.; de Pablo, J. J.; Abbott, N. L. Topological Defects in Liquid Crystals as Templates for Molecular Self-Assembly. Nat. Mater. 2015, 15, 106−112. (6) Chen, Y.; et al. Ultra-Fast Self-Assembly and Stabilization of Reactive Nanoparticles in Reduced Graphene Oxide Films. Nat. Commun. 2016, 7, 12332. (7) Calandra, P.; Caschera, D.; Liveri, V. T.; Lombardo, D. How SelfAssembly of Amphiphilic Molecules Can Generate Complexity in the Nanoscale. Colloids Surf., A 2015, 484, 164−183. (8) Lehn, J. M. Toward Self-Organization and Complex Matter. Science 2002, 295, 2400−2403. (9) Wang, C.; Wang, Z.; Zhang, X. Amphiphilic Building Blocks for Self-Assembly: From Amphiphiles to Supra-Amphiphiles. Acc. Chem. Res. 2012, 45, 608−618. (10) Zhang, X.; Wang, C. Supramolecular Amphiphiles. Chem. Soc. Rev. 2011, 40, 94−101. (11) Feng, Y.; Chu, Z. pH-Tunable Wormlike Micelles Based on an Ultra-Long-Chain ”Pseudo” Gemini Surfactant. Soft Matter 2015, 11, 4614−4620. (12) Lu, Y.; Yang, Y.; Sellinger, A.; Lu, M.; Huang, J.; Fan, H.; Haddad, R.; Lopez, G.; Burns, A. R.; Sasaki, D. Y.; Shelnutt, J.; Brinker, C. J. Self-Assembly of Mesoscopically Ordered Chromatic Polydiacetylene/Silica Nanocomposites. Nature 2001, 410, 913−917. (13) Tsuda, A.; Sakamoto, S.; Yamaguchi, K.; Aida, T. A Novel Supramolecular Multicolor Thermometer by Self-Assembly of a PiExtended Zinc Porphyrin Complex. J. Am. Chem. Soc. 2003, 125, 15722−15723. (14) Wei, H.; Shi, N.; Zhang, J.; Guan, Y.; Zhang, J.; Wan, X. pHResponsive Inorganic-Organic Hybrid Supramolecular Hydrogels With Jellyfish-Like Switchable Chromic Luminescence. Chem. Commun. 2014, 50, 9333−9335. (15) Harada, A.; Kobayashi, R.; Takashima, Y.; Hashidzume, A.; Yamaguchi, H. Macroscopic Self-Assembly Through Molecular Recognition. Nat. Chem. 2011, 3, 34−37. (16) He, S.; Qu, M.; Feng, Y. Gas-Induced Reversible Dispersion/ Aggregation of Graphene. ChemNanoMat 2015, 1, 438−444. (17) Guo, Z.; Feng, Y.; He, S.; Qu, M.; Chen, H.; Liu, H.; Wu, Y.; Wang, Y. CO(2)−Responsive ”Smart” Single-Walled Carbon Nanotubes. Adv. Mater. 2013, 25, 584−590. (18) Liu, L.; Rui, L.; Gao, Y.; Zhang, W. Self-Assembly and Disassembly of a Redox-Responsive Ferrocene-Containing Amphiphilic Block Copolymer for Controlled Release. Polym. Chem. 2015, 6, 1817−1829. (19) Kumar, S.; Raghavan, S. R. Photogelling Fluids Based on LightActivated Growth of Zwitterionic Wormlike Micelles. Soft Matter 2009, 5, 797−803. F


Article

The Journal of Physical Chemistry C (40) Aliprandi, A.; Mauro, M.; De Cola, L. Controlling and Imaging Biomimetic Self-Assembly. Nat. Chem. 2015, 8, 10−15. (41) Orgiu, E.; Samorí, P. Organic Electronics Marries Photochromism: Generation of Multifunctional Interfaces, Materials, and Devices. Adv. Mater. 2014, 26, 1827−1845. (42) Li, Y.; Zhang, H.; Qi, C.; Guo, X. Light-Driven PhotochromismInduced Reversible Switching in P3HT−Spiropyran Hybrid Transistors. J. Mater. Chem. 2012, 22, 4261−4265. (43) Ishiguro, Y.; Hayakawa, R.; Chikyow, T.; Wakayama, Y. Optically Controllable Dual-Gate Organic Transistor Produced via Phase Separation between Polymer Semiconductor and Photochromic Spiropyran Molecules. ACS Appl. Mater. Interfaces 2014, 6, 10415− 10420. (44) Florea, L.; McKeon, A.; Diamond, D.; Benito-Lopez, F. Spiropyran Polymeric Microcapillary Coatings for Photodetection of Solvent Polarity. Langmuir 2013, 29, 2790−2797. (45) Caude, M.; Jardy, A. Normal-Phase Liquid Chromatography. In Handbook of HPLC; CRC Press, 1998.

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