Self-Assembly and Formation of Chromonic Liquid Crystals from the

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Self-assembly and Formation of Chromonic Liquid Crystals from the Dyes Quinaldine Red Acetate and Pyronin Y J. Rodrigo Magana, Maria Homs, Conxita Solans, Marc ObiolsRabasa, Laura M. Salonen, and Carlos Rodriguez-Abreu J. Phys. Chem. B, Just Accepted Manuscript • DOI: 10.1021/acs.jpcb.5b10567 • Publication Date (Web): 23 Dec 2015 Downloaded from http://pubs.acs.org on December 29, 2015

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The Journal of Physical Chemistry

Self-assembly and Formation of Chromonic Liquid Crystals from the Dyes Quinaldine Red Acetate and Pyronin Y J.R. Maganaa, M. Homsa, C. Solansa, M. Obiols-Rabasab, L. M. Salonenc and C. RodríguezAbreuc, * a

Instituto de Química Avanzada de Cataluña, Consejo Superior de Investigaciones

Científicas (IQAC-CSIC), CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Jordi Girona 18-26, 08034 Barcelona, Spain. b

Division of Physical Chemistry, Lund University, Getingevägen 60, SE-22241 Lund,

Sweden. c

International Iberian Nanotechnology Laboratory, Av. Mestre José Veiga s/n, 4715-

330 Braga, Portugal.

1 ACS Paragon Plus Environment


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Abstract

The aqueous self-assembly behaviour of the dyes Quinaldine red acetate and Pyronin Y in a wide range of concentrations is reported here for the first time. 1H NMR spectroscopy, polarized-light optical microscopy and small and wide X-ray scattering were used to get insight into molecular interactions, phase boundaries and aggregate structure. Quinaldine red acetate and Pyronin Y self-organize into unimolecular

stacks

driven

by

attractive

aromatic

interactions.

At

high

concentrations, spatial correlation among the molecular stacks gives rise to nematic liquid crystals in both systems. Quinaldine red acetate additionally produces a rare chromonic O phase built of columnar aggregates with anisotropic cross-section ordered in a rectangular lattice. The O phase changes into a columnar lamellar structure as a result of a temperature-induced phase transition. Results open the possibility of finding chromonic liquid crystals in other commercially available dyes with a similar molecular structure. This would eventually expand the availability of these unique soft materials and thus introduce new applications for marketed dyes.


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Introduction Molecular self-assembly in aqueous medium is an important field of research with many related industrial applications. Surfactants and amphiphilic block copolymers are representative examples of self-organizing molecules to which much research has been devoted.1 In particular, lyotropic liquid crystals from those amphiphilic systems have been the subject of extensive studies. Another class of lyotropic mesophases is constituted by chromonic liquid crystals (CLCs), which are formed by a range of water-soluble multi-ring aromatic compounds. The self-assembly behaviour and the structure of chromonic molecules differ from those of conventional amphiphiles in many aspects: the molecules that form CLCs are rigid aromatic planks rather than flexible aliphatic rods. The solubilizing groups in these molecules are located at the periphery rather that at one end, and they do not show a Krafft point or a definite critical aggregate concentration.2 The molecules in CLCs arrange into columns driven by aromatic stacking interactions. Two common CLC mesophases have been widely reported, the chromonic Nematic or N phase and the chromonic hexagonal or M phase.2-4 Other CLC mesophases, such as the O phase featuring 2D rectangular array of columns, have been predicted by analogy with thermotropic discotic systems.4 Some evidence has been found for this phase3, 5 but to the best of our knowledge sufficient data on structural characterization is not available. Although CLCs have been known for decades, the range of molecules known to form chromonics mesophases is still limited to a few drug molecules,6-9 dyes10-30 and 3 ACS Paragon Plus Environment


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biomolecules.31-32 Studies on dyes have been sometimes hampered by impurities present in commercial samples: for instance, the presence of residual inorganic salts is known to strongly affect the phase behaviour of lyotropic liquid crystals.9, 12, 33 Several dyes (e.g., cyanine dyes) show a strong tendency to form CLCs in water at relatively low concentration. Unique structures such as lamellar, brick-wall aggregates and hollow pipes have been found.16-19,

22

Nevertheless, their short and

long-range structures remain, in many instances, a matter of discussion. Additionally, the relationship between the molecular structure and the bulk phase behaviour is still not well understood. For example, small modifications in the architecture of a chromonic molecule, such as adding one functional group, can drastically change their aqueous behaviour.6 Herein, we report for the first time on the phase behaviour in wide range of concentration of two cationic dyes, Quinaldine red acetate (QR-Ac, hemicyanine dye, Figure 1a) and Pyronin Y (PyY, xanthene dye, Figure 1b). The iodine salt of Quinaldine red is utilized as a pH indicator and as molecular probe, whereas Pyronin Y is a widely used fluorescent RNA stain. As commercial Quinaldine red iodide is practically insoluble in water, we used a previously reported counterion-exchange strategy to enhance dye solubility and improve the likelihood of CLC occurrence.19 The iodine salt of Quinaldine red and Pyronin Y are known to form molecular stacks in dilute solutions,

34-35

but to our knowledge there is no report on the formation of

lyotropic liquid crystals from these dyes. This study aims at showing how new properties can be discovered for common dyes if the analysis and characterization window is expanded.


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Experimental Materials and preparation methods Quinaldine red iodide (QR-I, 95%, Acros Organics) was purified by washing the powder with water and recovering the insoluble fraction by filtration; this process was repeated three times before drying the insoluble fraction (80% of yield). The corresponding acetate salt was prepared by adding silver acetate (1.1 equivalents) into a solution of QR-I in EtOH (2.5 mmol of QR-I in 20 mL of EtOH). After removal of precipitated AgCl by filtration, the solvent was evaporated under nitrogen flow to obtain the solid QR-Ac with 95% yield (for characterization, see the SI). Pyronin Y (PyY, 96%, Sigma Aldrich) was used as received without further purification. Millipore ultrapure water (resistivity = 18.2 MΩ cm‒1) was used in all the experiments. Samples with high dye concentrations were placed in test tubes with a narrow constriction and flame-sealed. These samples were mixed by repeated centrifugation at 40 ºC. Characterization Temperature-Resolved Polarized Optical Microscopy. Polarized optical microscopy (POM) was performed with an Olympus BX51TRF6 microscope coupled to an Olympus DP73 digital camera. Samples were heated using a peltier hot stage with a precision of ± 1 ºC. Nuclear magnetic resonance (NMR). For 1H NMR spectroscopy, 750 µL of sample were placed in NMR tubes with a diameter of 5 mm. Spectra in D2O and DMSO-d6 were collected at 25 ºC in a Varian VNMRS spectrometer (400 MHz and 500 MHz).



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Small and Wide Angle X-ray Scattering (SAXS/WAXS). 1D SAXS patterns were obtained on a S3MICRO instrument (Hecus X-ray Systems) with point focalization, equipped with a GENIX microfocus X-ray source (λ = 1.54 Å) operating at 50 kV and 1 mA. The scattered intensity was recorded using a positionsensitive detector (HECUS). For the measurements, samples were placed in flamesealed glass capillaries. 2D SAXS/WAXS measurements were performed using a SAXSLab Ganesha 300XL instrument (SAXSLAB ApS), a pinhole collimated system equipped with a Genix 3D X-ray source (λ = 1.54 Å). Data were collected with a Pilatus 300K detector placed at sample-to-detector distance that yielded an overall q range of 0.1‒3 Å‒1. For calculations of structural parameters derived from SAXS data, the density of QR-Ac was assumed to be 1.1 g/cm3 (solid density of 1-Ethyl2-methyl quinolinium iodide) whereas the density of PyY was taken as 1.2 g/cm3 (same as xanthene). Results and discussion Self-assembly of QR-Ac and PyY in water at low concentration The molecular self-assembly of dyes at low concentration was studied by 1H NMR spectroscopy. The spectra of QR-Ac and PyY were measured at 0.0005, 0.0025, 0.005, 0.05, 0.5 and 5 wt% of dye in D2O and the signals show upfield shifts with increasing concentration (Figure 1). For concentrations lower than 0.0005 wt% the signal-to-noise ratio was too poor for signal detection. For both systems, a large concentration-dependent change upfield in the chemical shift ∆δ was found for most protons, typically in the range of 0.5–2 ppm. As it has been observed in chromonic systems, the continuous growth of molecular columns with increasing concentration


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causes shielding of the protons, which displaces the chemical shifts upfield, the so-called ring-current effect.19, 25, 27 There is a difference between the chemical shifts of monomers and aggregates, but only one single averaged spectrum is observed because of fast molecular exchange between the two states (> 10‒3 s‒1).27 No sign of leveling off can be observed in the curves in Figure 1, and thus it can be inferred that aggregates and monomer coexist in the range of concentrations studied. Such coexistence is commonly found in self-aggregating dyes.30 Also, NMR signals become wider above 5 wt% for both dyes, since the relaxation time of the aggregates becomes shorter as their size and concentration increases. The chemical shifts of the phenylene ring protons (9 and 10 in Figure 1a) of QRAc decrease significantly (> 1.4 ppm) with increasing concentration, indicating that the phenylene ring undergoes efficient aromatic stacking interactions within the aggregates. 1H‒1H NOE correlation peaks of some of the protons of the quinolinium ring with those of the dimethylamine moiety suggest an antiparallel arrangement of QR-Ac in the stacks, with the electron-rich dimethylaniline in close proximity to the electron-deficient quinolinium moiety (for NOESY spectra and other NMR data, see the supporting information). Such correlations were not found in DMSO-d6, where QR-Ac aggregation was not detected. A similar molecular stacking has been reported for the dye Sunset Yellow in both experimental36 and simulation studies.37 As expected, the change in the chemical shift of the protons of the acetate counterion is negligible due to its weak interactions with the aggregates, probably because of efficient solvation of this ion in water. Recorded UV-vis spectra of QR-Ac aqueous solutions (Supporting Information, Fig. SI1) were similar to those of the iodine salt,35 with a main band at around 500 7 ACS Paragon Plus Environment


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nm that shows a slight blue shift to shorter wavelengths as concentration increases, which is ascribed to exciton coupling between molecules in close proximity inside aggregates. The aromatic protons of PyY (1‒4, Figure 1b) show pronounced decreases in chemical shifts with increasing concentration (changes between 0.8 and 1.2 ppm), whereas the protons of the dimethylammonium moieties shift much less ( a). The cross-sectional area of the aggregates in 2D rectangular phase (AC) can be estimated from:

= (2)

where is the volume fraction of QR-Ac in the system.. The estimated crosssectional area is around 130 Å2, which is slightly larger than the area of a single molecule (∼110 Å2) calculated with Spartan® (Wavefunction Inc.). As concentration increases, the distance between aggregates in the O phase becomes shorter (Figure 5). The lattice parameters, peaks positions and relative intensities are summarized in Table 1.

Table 1. Peak positions q, relative intensities I, and lattice parameters a and b for the Ophase of QR-Ac/ water system at different concentrations at 25 ºC. [C] (wt%) 59.37 60.25 61.75 64.4 66 68

q02 (Å) 0.372 0.377 0.382 0.392 0.406 0.411

q11 (Å) 0.455 0.463 0.469 0.483 0.491 0.502

q04 (Å) --0.764 0.788 0.814 0.827

q22 (Å) 0.914 0.923 0.934 0.953 0.992 1.007

a (Å)

b (Å)

I (q02)

I (q11)

I (q04)

I (q22)

15.13 14.98 14.65 14.22 14.08 13.80

33.71 33.28 32.86 32.05 30.95 30.33

1 1 1 1 1 1

0.65 0.51 0.54 0.82 1.26 0.81

--0.47 0.44 0.64 0.49

0.55 0.60 0.53 0.51 0.73 0.53

SAXS data for the O phase as a function of temperature is available in tables SI1 and SI2 (Supporting Information). A possible stacking arrangement giving such dimensions is shown in Scheme 1a. As seen in Figure 4d, 2D SAXS patterns show a partial alignment characteristic of long anisotropic aggregates. The axial arcs in the WAXS region are almost 14 ACS Paragon Plus Environment

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orthogonal to the equatorial SAXS reflections, evidencing that the stacking direction is perpendicular to the rectangular symmetry plane, in agreement with the proposed array shown in Scheme 1a. Above 45 ºC, SAXS patterns (Figure 4c) feature two well-defined reflections corresponding to the planes with Miller indices of (1 0) and (2 0), characteristic of a lamellar phase (ColL) and a broad, rather diffuse reflection (hump) at lower q that varies with concentration (Bragg distance from 17 Å to 20 Å). Such reflection can be assigned to structural features within the lamellae, namely, positional correlation of the columnar aggregates in the same layer with a characteristic separation distance. The pattern for the ColL resembles that of mesh phases found in surfactant systems.41-43 However, the ColL phase is different from lamellar phases usually found in surfactants and amphiphilic block copolymers systems.44 In the ColL mesophase, molecules are arranged in columns inside each layer (Scheme 1b). 2D patterns for the ColL phase again give evidence of a partial alignment, characteristic of anisotropic aggregates (Figure 4e). The width of the molecular layer in a lamellar phase dπ can be calculated by = ∗ (3) where d is the Bragg distance from the first SAXS peak (i.e. distance between layers) and ϕf is the dye volume fraction.



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Scheme 1. Representation of proposed structures for a) chromonic columnar rectangular mesophase, O phase, and b) columnar lamellar mesophase, ColL for the QR-Ac/water system. Relevant structural parameters are also indicated. The calculated width of the layers is about 8 Å, similar to those reported by Tiddy and co-workers for cyanine dyes in brick-wall unimolecular layers,17,

22

and

matching with the width of a single QR-Ac molecule. This is in agreement with the proposed molecular array depicted in Scheme 1b. The distance between layers (d) decreases with increasing concentration (Figure 5). From the gathered evidence we cannot completely rule out the brick-wall lamellar structure proposed by Tiddy and co-workers,17, 22 but the configuration depicted in Scheme 1 would imply merely a rearrangement of the columns during the O phase‒ ColL phase transition, which is more likely to occur than a simultaneous major change in molecular stacking. In fact, the layered structure with columnar organization shown in Scheme 1b is known to exist in certain discotic compounds,45 although to our knowledge, it has never been reported for chromonic systems.


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Figure 4. Characteristic SAXS/WAXS pattern of QR-Ac for (a) nematic phase at 50 wt% and 25 °C, (b) O phase at 65 wt% and 25 °C, and (c) lamellar phase (ColL) at 65 wt% and 50 °C, dmica is a reflection caused by the mica sample holder, (d) and (e) 2D patterns of rectangular O phase, and lamellar ColL phase, respectively.



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Figure 5. Structural parameters of QR-Ac phases as a function of dye concentration. Bragg d spacing from the first SAXS peak at 25 ºC for nematic phase (squares), O phase (circles) and lamellar ColL phase at 50 ºC (triangles). The inset shows the log-log plot of 1/d vs volume fraction ϕf. The slope of the double logarithm plot of the inverse Bragg spacing from the first SAXS peaks (1/d) vs volume fraction ϕf (inset Figure 5) shows values of 0.6 and 0.7 for the nematic and O phase respectively and 1.5 for the Lcol phase . These values are characteristic of columnar (≈0.5) and one and two-dimensionally swelling layers (>1) respectively, in agreement with the phase behaviour discussed above.


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Phase behaviour and structure of PyY/water system. The phase diagram of PyY in water was constructed as shown in Figure 6. PyY forms CLCs depending on the temperature and concentration. From 45 wt% to 73 wt% PyY features an N phase at room temperature, as confirmed by the optical textures under the microscope (Figure 7a). The N phase coexists with an isotropic liquid in a wide range of concentrations, which can be confirmed by POM (Figure 7b). This wide “coexistence-zone” has been observed in other chromonic systems, such as the Bordeaux dye/water system.10 Above 73 wt% the N phase coexists with a crystalline solid; this region was not further studied. It is evident that PyY mesomorphism is less complex than that of QR-Ac, demonstrating the effect of molecular architecture on phase behaviour.



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Figure 6. Partial phase diagram of PyY in water as a function of concentration and temperature. N and I denote nematic and isotropic phases, respectively.

Figure 7. Polarized optical microscopy textures of PyY for (a) nematic phase (60 wt% dye) at 25 °C, (b) nematic phase in coexistence with isotropic solution (60 wt% dye) at 55 °C. Structural analysis of PyY phases in water was carried out by SAXS/WAXS. The SAXS patterns of the N phase show a broad band indicative of positional correlation between columns (see the supporting information, Figure SI4). Similarly to QR-Ac, for PyY the distance between aggregates decreases as the concentration increases (Figure 8). The WAXS reflection corresponding to the stacking distance between the aromatic moieties, Bragg distance = 3.4 Å, q = 1.8 Å‒1, was also observed for PyY (see supporting information, Figure SI5).


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Figure 8. Bragg spacing from the first SAXS peak at 25 °C as a function of PyY concentration. To estimate the cross-sectional area of the columns in the nematic phase, a hexagonal array of cylinders can be assumed as first approximation.10 In fact, atomic simulations of the nematic phase formed by the dye Sunset Yellow show a loose hexagonal packing of the chromonic columns.37 In a hexagonal array of cylinders, the square of the Bragg distance (d2) varies linearly with the inverse volume fraction following the expression: =

√

∗ (4)

where Ac is the cross-sectional area of a cylindrical aggregate. Ac can be determined from the slope of the d2 vs shown in Figure 9.



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Figure 9. Variation of the square of the Bragg distance with the inverse volume fraction of the PyY/water system. Within this approximation, a cross-sectional area of ca. 130 Å2 is obtained. This value is slightly larger than the area for a PyY molecule, 100 Å2, calculated with Spartan® (Wavefunction Inc.). It is thus reasonable to infer that PyY forms unimolecular stacks. The intercolumnar distances in PyY are shorter than the ones observed for the QRAc/water system (Figure 5), again suggesting a smaller cross-sectional area of the aggregates. The concentration needed for liquid crystal formation for PyY is higher than that for QR-Ac, probably due to the smaller aggregate cross-sectional area and therefore smaller effective volume fraction. The aggregation of PyY differs from that of xanthone-derived dyes that form multi-molecular cross-section aggregates.28


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It appears that small changes in molecular architecture have a large impact in the self-assembly behaviour. SAXS measurements of PyY samples as a function of temperature (see Supporting information, Fig. SI5) revealed a sudden increase in the d-spacing at the nematicisotropic phase transition. From Eq. 4, this is most likely caused by an increase in the cross sectional area of aggregates (Ac); other possible causes are density and hydration changes that may result in a decreased effective volume fraction of aggregates. A similar variation of d-spacing with temperature was found for QR-Ac (Supporting information, Fig. SI6)

Conclusions The self-aggregation behaviour of two cationic dyes has been studied. From 1H NMR spectroscopy in D2O, it was inferred that monomer and aggregates coexist in all concentrations studied for both dyes. The proton chemical shifts of the phenylene group for QR-Ac decrease strongly as concentration increases, evidencing efficient intermolecular aromatic interactions. 1H‒1H NOE spectroscopy suggests that QR-Ac forms antiparallel stacks in D2O, with dimethylaniline interacting with the quinolinium moiety. Likewise, PyY shows a behaviour expected for self-aggregation into stacks with aromatic cores lying on top of each other. With higher concentration, both QR-Ac and PyY form chromonic liquid crystals in water. Data from QR-Ac/water and PyY/water systems suggest that both form unimolecular columnar aggregates. The concentration at which they form liquid crystals is higher than the one reported for other dyes (e.g., pinacyanol acetate forms liquid crystals at 0.75 wt%),19 most likely due to the considerably smaller aggregate 23 ACS Paragon Plus Environment


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cross-sectional area. These results show the importance of the excluded volume of the columnar aggregates on the formation of chromonic liquid crystals. QR-Ac forms a rectangular O phase at high concentration, suggesting aggregates with anisotropic cross-section. A rearrangement of the aggregates occurs when the rectangular phase changes into a lamellar phase presumably formed by layers composed of molecular stacks. In contrast, PyY only forms nematic liquid crystals in water in the studied concentration range, highlighting the effect of molecular architecture on the complexity of phase mesomorphism. This work opens the possibility of finding chromonic liquid crystals in other commercially available hemicyanine and xanthene-based dyes, of which aggregation properties remain unknown. This would eventually expand the availability and knowledge on these unique soft materials, and thus, open the possibility of tailormade chromonic molecules for new applications in the market. Funding sources The authors acknowledge financial support from the European Commission under the Seventh Framework Program by means of the grant agreement for the Integrated Infrastructure Initiative N. 262348 European Soft Matter Infrastructure (ESMI). J.R.M. acknowledges funding from the Ministerio de Economia y Competitividad, Spain (Grant: EEBB-I-15-10167 and project: CTQ2011-29336-C03-01). C.R.-A. acknowledges funding from EU FP7 Cooperation Program, NMP-theme (Grant no. 314212) and InveNNta project financed by EU Programme for Cross-border Cooperation: Spain-Portugal (POCTEP 2007−2013).


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Acknowledgements The authors are grateful to Prof. Peter Schurtenberger (Lund University, Sweden) for kindly giving access to X-ray instrumentation. The authors also thank Yolanda Ruiz (IQAC/CSIC, Spain) for her help with NMR experiments, and the Small Angle X-ray Scattering service from IQAC/CSIC for their help on the meassurements.

ASSOCIATED CONTENT

Supporting information NMR Spectroscopy Proton chemical shifts are expressed in parts per million (δ scale) and are calibrated using the residual undeuterated solvent peak as an internal reference (D2O: δ 4.80; (CD3)2SO: δ 2.50). Data for 1H NMR spectra are reported as follows: chemical shift (δ, ppm) (multiplicity, coupling constant/Hz, integration, assignment). Multiplicities are reported as follows: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, or combinations thereof. Carbon chemical shifts are expressed in ppm (δ scale) and are referenced to the carbon resonances of the solvent (CD3)2SO: δ 39.52). Atom numbering is arbitrary. The assignment of protons was done based on twodimensional NMR spectroscopy experiments.



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Quinaldine Red Acetate 3

2 1

4

8 5

9 10

6

7 12

11

13 14 1

H NMR (400 MHz, D2O): 1.40 (t, J = 7.4 Hz, 3 H, H‒C(13)), 1.93 (s, 3 H, H‒C(14)),

2.35 (s, 6 H, H‒C(11)), 4.27 (q, J = 8.0 Hz, 2 H, H‒C(12)), 5.73 (d, J = 8.80 Hz, 2 H, H‒ C(10)), 6.43 (d, J = 15.6 Hz, 1 H, H‒C(7)), 6.87 (d, J = 8.8 Hz, 2 H, H‒C(9)), 7.33 (d, J = 15.2 Hz, 1 H, H‒C(8)), 7.51‒7.55 (m, 1 H, H‒C(4)), 7.62 (d, J = 9.6 Hz, 1 H, H‒C(1)), 7.70 (d, J = 8.0 Hz, 1 H, H‒C(3)), 7.73‒7.79 (m, 2 H, H‒C(5) and H‒C(6)), 8.00 (d, J = 8.8 Hz, 1 H, H‒C(2));13C NMR (100 MHz, D2O): 12.9, 23.1, 38.4, 45.5, 108.0, 110.7, 116.9, 118.4, 120.4, 126.6, 127.4, 129.5, 130.7, 133.8, 137.4, 141.2, 147.9, 151.6, 153.4, 181.2. 1

H NMR (400 MHz, (CD3)2SO): 1.54 (t, J = 7.1 Hz, 3 H, H‒C(13)), 1.55 (s, 3 H, H‒

C(14)), 3.09 (s, 6 H, H‒C(11)), 5.05 (q, J = 7.1 Hz, 2 H, H‒C(12)), 6.84 (d, J = 9.0 Hz, 2 H, H‒C(10)), 7.47 (d, J = 15.4 Hz, 1 H, H‒C(7)), 7.82‒7.89 (m, 3 H, H‒C(9) and H‒C(4)), 8.09 (ddd, J = 8.8, 7.2, 1.6 Hz, 1 H, H‒C(5)), 8.25 (dd, J = 8.0, 1.4 Hz, 1 H, H‒C(3)), 8.32 (d, J = 15.4 Hz, 1 H, H‒C(8)), 8.44 (d, J = 9.0 Hz, 1 H, H‒C(6)), 8.54 (d, J = 9.3 Hz, 1 H, H‒C(1)), 8.80 (d, J = 9.2 Hz, 1 H, H‒C(2));

13

C NMR (100 MHz, (CD3)2SO): 13.8, 24.8,

45.5, 110.7, 111.9, 118.4, 120.3, 122.4, 127.1, 128.0, 130.1, 132.1, 134.4, 138.1, 142.0, 149.7, 153.0, 155.4, 172.6 (one signal hidden under the carbon resonance of the solvent).


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H NMR (400 MHz, D2O), QR-Ac 0.5 wt%



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13

C NMR (100 MHz, D2O), QR-Ac 0.5 wt%


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1

H NMR (400 MHz, (CD3)2SO), QR-Ac 0.5 wt%



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13

C NMR (100 MHz, (CD3)2SO), QR-Ac 0.5 wt%


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2D 1H‒1H NOESY (400 MHz, D2O); QR-Ac 0.5 wt%



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2D 1H‒1H NOESY (400 MHz, (CD3)2SO); QR-Ac 0.5 wt%


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Pyronin Y 1

2 3

4 5 1

H NMR (400 MHz, D2O): 3.03 (s, 12 H, H‒C(5)), 6.16 (s, 2 H, H‒C(4)), 6.67 (dd, J =

9.1, 1.6 Hz, 3 H, H‒C(3)), 7.23 (d, J = 9.2 Hz, 2 H, H‒C(2)), 7.82 (s, 1 H, H‒C(1)).

1

H NMR (500 MHz, D2O), PyY 0.5 wt%



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UV-Vis Spectroscopy. Experiments were performed in a Varian Cary 300 spectrophotometer instrument. Measurements were performed at 25 ºC.

Figure SI1. Absorption coefficient of QR-Ac at different concentrations in water at 25 ºC.


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Fluorescence Spectroscopy. Experiments were performed in a Varian Cary Eclipse 4000 spectrophotometer instrument. Measurements were performed at 25 ºC at an exitation wavelength of 530 nm.

Figure SI2. Fluorescence spectra of PyY (excitation wavelength = 530 nm) at different concentrations in water at 25 ºC. The fluorescence is completely quenched at 0.08 wt%.



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Micro-Differential Scanning Calorimetry (Micro-DSC). Samples were placed in a hermetically sealed 850 µl hasteloid batch vessel. Measurements were recorded using a Setaram Micro-DSC III. Micro-DSC scans for concentrated (> 60 wt%) samples presented a small transition peak with enthalpy values of around 0.1 kJ/mol (Figure SI3) that could be ascribed to a rectangular to lamellar phase transition. A larger peak at lower temperatures attributed to a crystalline solid–liquid crystal transition was also observed with an enthalpy value of around 3 kJ/mol.

Figure SI3. Micro DSC curves of a 68 wt% QR-Ac sample in water.


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Small and wide angle X-ray Scattering. Experiments were performed in an Anton Paar SAXSess mc2 instrument. Data were collected with an image plate detector. Samples were placed in flamne-sealed capillaries (0.9 mm in diameter and 0.01 mm wall thickness) for the measurement.

Figure SI4. Representative SAXS/WAXS pattern for a 50wt% PyY sample at 30 ºC in water.



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Figure SI5. Bragg spacing from the most intense peak in the dye nematic phase as a function of temperature for a 60 wt% sample of PyY


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Figure SI6. Bragg spacing from the most intense peak in the dye nematic phase as a function of temperature for a 50 wt% sample of QR-AcSI1.



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Table SI1. Experimental Peak positions for the QR-Ac/water O phase at different concentrations at 30 ºC [C] (wt%) 59.37 60.25 61.75 64.4 66 68

q02 (Å) 0.369 0.375 0.379 0.388 0.401 0.407

q11 (Å) 0.450 0.458 0.465 0.479 0.495 0.500

q04 (Å) --0.760 0.773 0.808 0.818

q22 (Å) --0.928 0.946 0.987 1.001

Table SI2. Experimental Peak positions for the QR-Ac/water O phase at different concentrations at 35 ºC [C] (wt%) 59.37 60.25 61.75 64.4 66 68

q02 (Å) -0.373 0.373 0.383 0.395 0.401

q11 (Å) -0.454 0.459 0.469 0.488 0.498

q04 (Å) --0.751 0.768 0.800 0.810

q22 (Å) --0.928 0.937 0.982 0.992


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Corresponding Author Carlos Rodriguez Abreu (email: [email protected]) Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

Abbreviations QR-Ac, Quinaldine Red Acetate; PyY, Pyronin Y; CLC, Chromonic Liquid Crustal; NMR, Nuclear Magnetic Resonance; NOESy, Nuclear Overhauser Effect Spectrometry; POM, Polarized Optical Microscopy; SAXS/WAXS, Small and Wide Angle X-ray Scattering; DSC, Differential Scanning Calorimetry; UV-Vis, Ultraviolet-Visible.



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ToC Table of Contents Graphic


Self-Assembly and Formation of Chromonic Liquid Crystals from the

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