Unusual Molecular and Supramolecular Structures of Chiral Low

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Unusual Molecular and Supramolecular Structures of Chiral Low Molecular Weight Organogelator with Long Perfluoroalkyl Chains Toshiyuki Sasaki, Akiko Egami, Tomoko Yajima, Hidehiro Uekusa, and Hisako Sato Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.8b00779 • Publication Date (Web): 31 May 2018 Downloaded from http://pubs.acs.org on May 31, 2018

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Crystal Growth & Design

Unusual Molecular and Supramolecular Structures of Chiral Low Molecular Weight Organogelator with Long Perfluoroalkyl Chains Toshiyuki Sasaki,*,†,# Akiko Egami,§ Tomoko Yajima,‡ Hidehiro Uekusa,§ Hisako Sato† †

Department of Chemistry, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577,

Japan. §

Department of Chemistry and Materials Science, Tokyo Institute of Technology, Ookayama 2-

12-1, Meguro-ku, Tokyo 152-8551, Japan. ‡

Department of Chemistry, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo, Japan.

ABSTRACT. Gels composed of low molecular weight gelators (LMWGs) are fascinating research targets from the viewpoints of applications because their functionalities are easily modified by designing their molecular structures. Some reliable gelator design approaches have been developed. However, new classes of molecular are sometimes discovered unexpectedly, suggesting that there remain unknown aspects about gelators. To obtain knowledge regarding gelation and crystallization ability, the crystal structure of N,N’-diperfluorooctanoyl-(1R,2R)-1,2diaminocyclohexane (RR-CF8), which is a derivative of 1,2-diaminocyclohexane, one of the

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most famous LMWGs, was investigated in addition to the vibrational circular dichroism (VCD) measurements. The crystal structure was solved from powder X-ray diffraction patterns because recrystallization of RR-CF8 afforded no suitable single crystals for single crystal X-ray diffraction measurement. Two unusual structural features were confirmed. One is that the perfluoroalkyl chain (PFC) of RR-CF8 forms a pseudo-racemic helix, or a mixture of right- (P) and left-handed (M) helices, while elsewhere, PFCs generally have one-handed helicity. The other is that an oxygen atom of one of the amide groups is free of hydrogen bonds, reducing the stability of 1-dimensional hydrogen-bonded assemblies. These unique structural features let us propose the reasonable explanations for the gelation and crystallization ability of RR-CF8. Furthermore, a factor of environment-dependent chirality inversion of RR-CF8 supermolecules was clarified by combining X-ray crystallography and solid-state VCD spectroscopy.

INTRODUCTION Gelators1,2 are fascinating research targets because of their applicability in close-to-life materials such as cosmetics and oil solidifying agents as well as crystal growth,3 drug delivery system4 and so on.5 For further sophisticated applications, it is necessary to develop a new generation of gelators which gelate in desired solvents with low critical gelation concentration (CGC) and forms nano fibers with desired properties. Low molecular weight gelators (denoted as LMWGs) have advantages especially from the viewpoint of functionality in accordance with structural designability.6–9 Various functional groups can be introduced to desired positions of target molecules, resulting in high functionalization and fine tunings of gelation ability. Construction of specific supramolecular structures is also a useful strategy for functionalization of gels.10–13 These advantages can be


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exploited by developing gelator design guidelines from the elucidation of gelation mechanisms.1,2,14–16 For this purpose, crystal structure analysis by X-ray diffraction measurements is one of the most powerful tools because supramolecular structures are observed directly.13,16–18 It is difficult, however, to conduct crystal structure analysis due to the typically low crystallinity of LMWGs. In addition, it is possible that supramolecular structures in gels are not consistent with those in crystals.19,20 Therefore, gel structures have been proposed based on combinations of various measurements.21–23 From this point of view, vibrational circular dichroism (VCD) spectroscopy is especially useful because VCD signals contains precise conformational information of chiral molecules. Previously, our group detected handedness inversion of supramolecular chirality in organic salt crystals and elucidated the mechanism by combination of X-ray crystallography and VCD spectroscopy.24 This example suggests that VCD spectra reflect not only chirality of single molecules but also that of supermolecules. It was also demonstrated that expected structures of chiral gels, derivatives of 1,2-diaminocyclohexane,8,25 were proposed based on VCD measurements.22,23,26,27 In this report, structural characterization was conducted on N,N’diperfluorooctanoyl-(1R,2R)-1,2-diaminocyclohexane (denoted as RR-CF8) in crystalline state, revealing unusual structural features and unique characteristics originating from their amide and perfluoro moieties. Interestingly, RR-CF8 shows low gelation and high crystallization ability while chiral 1,2-diaminocyclohexane-based gelators generally show the opposite tendency.8 In addition, the crystal structure and supramolecular structure of RR-CF8 is same in the powdered crystals as in the gel fibers according to the respective powder X-ray diffraction patterns.22 The unique molecular conformations and hydrogen bonding networks of RR-CF8 in crystalline state


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were characterized from the viewpoints of chirality and gelation and crystallization ability based on X-ray crystallography and VCD spectroscopy. Chart 1. The molecular structure of N,N’-diperfluorooctanoyl-(1R,2R)-1,2-diaminocyclohexane (RR-CF8).

EXPERIMENTAL SECTION Materials. The low molecular weight gelators: N,N’-diperfluorooctanoyl-(1R,2R) or (1S,2S)-1,2diaminocyclohexane (RR-, or SS-CF8, respectively, and racemic one denoted as rac-CF8), were synthesized according to the previous reports.22All of the reagents and solvents employed in this study were commercially available and used without further purification. Crystal Structure Analysis from Powder X-ray Diffraction. A THF solution of RR-CF8 was evaporated, affording powdered crystals which were washed by chloroform and distilled water. Powder diffraction data of the crystals of RR-CF8 was then recorded at room temperature on a Rigaku SmartLab diffractometer with CuKα radiation and a D/teX Ultra detector covering 1.00– 70.00° (2θ). The powder X-ray diffraction pattern was then indexed using the program DICVOL0628 (M20 = 60.929 F20 = 139.130), giving the following unit cell with monoclinic metric symmetry: a =13.7467, b =5.2331, c = 22.0939Å, β = 93.910° (V = 1585.70Å3). From the systematic absences and consideration of unit cell volume (corresponding to Z = 2), the space


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group was assigned as P21. The profile was fitted using the Pawley method31 in the program DASH32 gave a good quality of fit (χ2 = 7.84). The molecular model was calculated by a DFT method (B3LYP 6-31+G*). Subsequent Rietveld refinement33 was carried out using the GSAS program.34 In the Rietveld refinement, standard restraints were applied to bond lengths and bond angles, and a global isotropic displacement parameter was also refined. The final Rietveld gave the following parameters: a = 13.7314(9) Å, b = 5.23203(22) Å, c = 22.1156(14) Å, β = 93.933(5)°, V = 1585.11(22) Å3; Rwp = 5.17%, Rp = 3.60%, RF2 = 13.56% (2θ range: 3.01– 60.01°; 5701 profile points; 246 refined variables; the corresponding Rwp for the Le Bail fitting was 3.21% (CCDC 1833372). Solid-state infrared (IR) and VCD Measurements. The solid-state IR and VCD spectra of the crystals of RR-CF8 were measured with a PRESTO-S-2016 spectrometer (JASCO, Co., Japan) using KBr pellets. A KBr pellet of each crystal was injected into an assembled cell with a window of 10 mmφ. The IR and VCD signals were accumulated during 5000–10,000 scans (ca. 1h–2 h) for each of the crystals. The resolution was 4 cm-1. The absorbance of the IR spectra was adjusted to ~ 1 for optimal measurements. The linear dichroism spectra were also measured. Computational details. The theoretical IR and VCD spectra of RR-CF8 were calculated using density functional theory (DFT) by the Gaussian 09 programme.35,36 The model structures were extracted from the crystal structures of RR-CF8. The geometry optimizations and IR/VCD calculations were performed using DFT at the B3LYP/6-31G (d,p) level of theory. The observed spectra were assigned based on animations of the molecular vibration with Gauss View 5.08 software (Gaussian Inc.).37 RESULTS and DISCUSSION


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No suitable single crystals of RR-CF8 for single crystal X-ray diffraction measurement were obtained from various standard organic solvents. Therefore, the crystal structure of RR-CF8 was derived from its powder X-ray diffraction pattern. Single Molecular Structure in Crystalline State. RR-CF8 has two chiral centers: R1 and R2, and two amide groups: AD1 and AD2 bonding to the R1 and R2, respectively (Figure 1a). The carbonyl groups of AD1 and AD2 direct toward the same direction (parallel) each other from the carbon to oxygen atoms. On the other hand, the two carbonyl groups of N,N’diperfluorobutanoyl-(1R,2R)-1,2-diaminocyclohexane (RR-CF4) direct toward the opposite direction (anti-parallel).18 RR-CF8 also has two linear perfluoroalkyl chains (PFCs), denoted as PFC1 and PFC2 and bonding to AD1 and AD2, respectively. The PFCs have interesting features. PFC2 has a onehanded helical conformation as generally observed in PFCs18,22,24,26,27,38–42 while PFC1 has a strained structure. The structures of PFCs were then precisely analyzed from the viewpoints of conformation and helicity. The carbon atoms of AD1, AD2, PFC1 and PFC2 are numbered Ca1, Cb1, Ca2 to Ca8 and Cb2 to Cb8, respectively, from the carbon atom of the AD to the edge of the PFCs. The dihedral angles Ca1-Ca2-Ca3-Ca4, Ca2-Ca3-Ca4-Ca5, Ca3-Ca4-Ca5-Ca6, Ca4Ca5-Ca6-Ca7 and Ca5-Ca6-Ca7-Ca8 in the PFC1 are +124°, +159°, +154°, -150°, and -131°, respectively. The dihedral angles mean that the first and last parts of PFC1 has plus, or lefthanded (M), and minus, or right-handed (P), helicity, respectively.43,44 In the case of the PFC2, the dihedral angles Cb1-Cb2-Cb3-Cb4, Cb2-Cb3-Cb4-Cb5, Cb3-Cb4-Cb5-Cb6, Cb4-Cb5-Cb6Cb7 and Cb5-Cb6-Cb7-Cb8 are -171°, -160°, -161°, -156°, and -149°, respectively. This helix has a minus direction judging from the edge of the PFC2, meaning it is a right-handed (P) helix. The helicity is made obvious by connecting the fluorine atoms in the PFCs as shown in Figure


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1c. In the PFCs, each carbon atom has two fluorine atoms except for the edge carbon which has three fluorine atoms. Viewed from the edge, the front fluorine atom at the left side or the right side is defined as Fα or Fβ, respectively, when the fluorine atoms are put on the upper side in the Newman projection. The Fαs as well as Fβs of the Cn (n = even number, a2 to a8 and b2 to b8 in the PFC1 and 2, respectively) were connected and colored in light blue and purple, respectively (Figure 1c(i)). In the same way, the Fαs and Fβs of the Cn (n = odd number, a3 to a7 and b3 to b7 in the PFC1 and 2, respectively) were also connected and colored in orange and green, respectively (Figure 1c(ii)). In PFC1, the first and last F–F connections downward to the right and left, respectively. This implies that PFC1 is a mixture of M and P helices, or left- and righthanded twist. In other words, PFC1 is pseudo-racemic even though PFC1 is directly bonded to the chiral center R1 with R configuration via amide bonds. This suggests that the chirality of R1 is incompletely transferred to PFC1. In the case of PFC2, on the other hand, the whole F–F connections downward only to the left in all cases, resulting in construction of a quadruple P helix. The chirality of the R2 propagates sufficiently to the PFC2. As a whole molecule, the ratio of the P helix exceeds the M helix in the crystal.


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Figure 1. Conformational analysis on the RR-CF8 in crystalline state: (a) top view, (b) side views from (i) AD side, (ii) PFC side, and (iii) Newman projection, and (c) the helicity of (i) PFC1 and (ii) PFC2.

Supramolecular Structure and Their Packing. As for the supramolecular structure of the component molecules, they are assembled to form a 1-dimensional (1-D) chain in a head-to-head manner by two one-sided intermolecular hydrogen bonds along the b axis (Figure 2a). The hydrogen bonding network has one hydrogen bond acceptor, two hydrogen bond donors, and seven component atoms (two hydrogen, two carbon, two nitrogen, and one oxygen atoms), and it is denoted as R12(7) according to graph set analysis (Figure 2b).45,46 The length of the hydrogen bonds: N–H···O=C between AD2···AD2 and AD1···AD2 of neighboring molecules, are 2.30 and 2.31 Å, respectively, which are distances from the hydrogen atoms to the oxygen atom. Unexpectedly, the oxygen atom of AD1 does not participate in hydrogen bonding networks unlike the other cases of 1,2-diaminocyclohexane-based LMWGs such as RR-CF4 which forms a 1-D column by two separated hydrogen bonds of each amide group (Figure 2c). It means that each RR-CF8 molecule is connected weakly, or flexibly, in 1-D hydrogen-bonded chains.


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Figure 2. The structure of a 1-dimensional (1-D) chain by hydrogen bonds: (a) side view, (b) hydrogen bonding network with the graph set denotation, and (c) schematic representation of (i) a 1-D chain of RR-CF8 by one-sided hydrogen bonds and (ii) a 1-D column RR-CF418 by separated hydrogen bonds. Blue dotted lines represent hydrogen bonds.

Gelation and Crystallization Ability. Enantiopure 1,2-diaminocyclohexane-based LMWGs with hydrocarbon alkyl chains are known to gelate with a wide range of organic solvents at low concentrations while racemic ones prefer to form crystals.8 In contrast, 1,2-diaminocyclohexanebased LMWGs with PFCs (enp or rac-CFn+1, the “enp”, “rac”, and “n” denotes enantiopure, racemic, and the number of carbon atoms in each PFC, respectively) show different features. The order of gelation ability by acetonitrile is enp-CF7 > rac-CF7, enp-CF8 < rac-CF8, and enp-CF9 ≈ rac-CF9.27 Especially with respect to enp- and rac-CF8, the gelation ability is the order enpCF8 < rac-CF8 from polar to non-polar solvents.22 These results clearly demonstrate that PFCs affect greatly on crystallization and gelation ability.


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With respect to the LMWGs with short PFCs, for example enp-CF4 and rac-CF4, the former and the latter form head-to-head and head-to-tail type 1-D hydrogen-bonded column, respectively (Figure 4a). In these cases, two carbonyl moieties of each molecules are anti-parallel, and both of them form intermolecular hydrogen bonds.18 In the case of RR-CF8 with long PFCs, head-tohead type 1-D hydrogen-bonded chain was constructed in the similar way with enp-CF4 (Figure 4b). Two carbonyl moieties of each RR-CF8 molecule, however, are parallel, and only one of them forms intermolecular hydrogen bonds. This suggests that there are another important factors for molecular assembly and crystallization in addition to the hydrogen bonds. One of the factors is interactions between PFCs.47,48 As theoretically calculated, interaction energy of a perfluoro-alkane dimer mainly originates from dispersion force, and it is comparable to that of hydrocarbon-alkane dimer.49 Dipole-array model and related articles about perfluoroalkyl groups, reported by Hasegawa group,40–42 is also helpful to explain the importance of interactions among PFCs. According to the dipole-array model, long PFCs with seven or more –CF2– moieties spontaneously aggregate in 2-dimentional (2-D) manners because of their dipole···dipole interaction arrays. On the other hand, short PFCs with six or less –CF2– show no aggregation. With respect to enp/rac-CF8, they have only six –CF2–, and thus their dipole-based aggregation driving forces seem to be weak. Each of PFCs of enp/rac-CF8, however, has an AD group, of which dipole is large and can be alternative to –CF2–. Consequently, RR-CF8 has 2-D aggregation driving forces in the similar way with the dipole-array model. The other factor is dense packing of molecules. The influence of dense packing for crystallization is implied by the strained structure of PFC1 of RR-CF8. Although PFCs generally have one-handed helical conformation, PFC1 has a pseudo-racemic helical conformation because


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of contacts among surrounding molecules. These factors makes molecular assemblies in the three-dimensional direction well-balanced, affording improved crystallization ability. At the same time, the singularity of the length of PFCs in molecular assemblies is particularly worthy to note.

Figure 4. 1-D Hydrogen-bonded columns of (a) (i) rac-CF4 (Refcode: KUXJUK), (ii) RR-CF4 (Refcode: KUXNAU),18 and (b) a 1-D hydrogen-bonded chain of RR-CF8.

On the other hand, the low stability of 1-D chains of RR-CF8 because of the one-sided hydrogen bonds reduces gelation ability because formation of 1-D fiber is essential for the 1,2diaminocyclohexane-based LMWGs according to SEM observations.18,22,23,27 With respect to rac-CF8, RR- and SS-CF8 molecules can assembly alternatively to construct 1-D columns by forming intermolecular hydrogen bonds efficiently in the head-to-tail manner as the same way with the other racemic 1,2-diaminocyclohexane-based LMWGs. As a result, rac-CF8 forms fibers and shows the better gelation ability than that of enp-CF8, e.g. gelation ability by acetonitrile: enp-CF8 < rac-CF8.22,27 Chirality Analysis by Solid-state VCD Spectroscopy. Finally, solid-state IR and VCD measurements were conducted on the crystals of RR-, SS-, and rac-CF8 (Figure 5). The origins of IR and VCD signals were assigned by comparing the simulated IR and VCD spectra by DFT


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(Supporting information Figure S1). The strong couplet observed around 1690 cm-1 (No. 1) was assigned to the stretching vibrations of C=O bonds. For RR-CF8, the couplet is negative to positive from lower to higher frequency, agreeing with that of the simulated VCD spectrum. It should be noted that the positive and negative signs of the couplet, or chirality, by stretching vibrations of C=O of RR-CF8 crystals are opposite to those of RR-CF8 gels prepared by hexafluorobenzene.18 The crystal structure and VCD spectrum of RR-CF8 suggested one of the chirality inversion factors. Until now, two amide groups of each 1,2-diaminocyclohexane derivatives have been confirmed and considered to be anti-parallel to form hydrogen-bonded 1-D columns.18,50,51 However, the crystal structure analysis of RR-CF8 revealed that the two amide groups are parallel and form hydrogen-bonded 1-D chains. This difference results in the chirality inversion in VCD spectra. With respect to the weak peaks around 1540 cm-1 (No. 2) and 1230 cm-1 (No3, i–iv), they are originated from bending vibration of N–H and the stretching vibrations of C–F bonds of PFCs, respectively. The latter in the VCD spectra are relatively small even though those in the IR spectra are large. This is because one of the PFCs of RR-CF8 is a pseudoracemic helix (Figure 1), of which chirality is almost cancelled out.


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Figure 5. (a) IR and VCD spectra of RR-, SS-, and rac-CF8 in solid-states in the region of 1200– 2000 cm-1 and (b) 1200–1300 cm-1. (c) Simulated VCD spectra calculated for a pair of hydrogenbonded RR-CF8 molecules.

CONCLUSION In conclusion, the crystal structure of N,N’-diperfluorooctanoyl-(1R,2R)-1,2-diaminocyclohexane (RR-CF8), which is a derivative of 1,2-diaminocyclohexane-based low-molecular weight organogelators (LMWGs), was analysized from powder X-ray diffraction data. RR-CF8 has following three characteristics according to the precise investigation of the crystal structure in combination with solid-state vibrational circular dichroism (VCD) measurements. Firstly, two carbonyl moieties of each RR-CF8 molecule are parallel while those of 1,2-diaminocyclohexanebased LMWGs are generally anti-parallel. The conformational difference changes 1-dimensional (1-D) assembly manners by hydrogen bonds. The difference was also confirmed by solid-state VCD spectra as chirality inversion. Secondly, RR-CF8 has two types of helical perfluoroalkyl chains (PFCs): PFC1 with a mixture of M and P helical conformation, or pseudo-racemic helix, and PFC2 with P helical conformation in crystalline state. This demonstrates that helicity of PFCs is variable depending on environment. The weak chirality of PFCs was also observed in the solid-state VCD spectra, reflecting the pseudo-racemic structure. Finally, the PFCs of RRCF8 interacted with each other, reflecting favorable interactions among long PFCs. It could be said that the interactions among PFCs have a great impact on crystallization ability as implied by the difference between the 1-D hydrogen bonding networks of RR-CF8 and RR-CF4 crystals. This result will contribute to making models of molecular assemblies with PFCs. As mentioned


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above, combination of X-ray crystallography and VCD spectroscopy gave us important knowledge about chirality and crystallization and gelation ability of RR-CF8. ASSOCIATED CONTENT Supporting Information. Model structures for simulation, IR/VCD spectra, experimental and calculated powder diffraction patterns, and X-ray diffraction data (CIF). This material is available free of charge via the Internet at http://pubs.acs.org.” AUTHOR INFORMATION Corresponding Author * (T.S.) E-mail: [email protected]; tel. +81 45 787 2184 Present Addresses #

Department of Materials System Science, Yokohama City University, 22-2 Seto, Kanazawa-ku,

Yokohama, Kanagawa 236-0027, Japan. Author Contributions The manuscript was written through contributions of all authors. / All authors have given approval to the final version of the manuscript. / All authors contributed equally. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was financially supported by JSPS KAKENHI Grant-in-Aid for JSPS Research Fellow (Number 15J00237 to T.S.), the JSPS MEXT KAKENHI Grants-in-Aid for Exploratory


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Research (Number JP26620068 to H.S.) and Innovative Areas (Number JP16H00840 to H.S.), and JSPS KAKENHI Grant Number 17K05745 to H.U. The computations were performed using the Research Center for Computational Science, Okazaki, Japan. REFERENCES 1. Terech, P.; Weiss, R. G. Low Molecular Mass Gelators of Organic Liquids and the Properties of Their Gels. Chem. Rev. 1997, 97, 3133–3159. 2. Weiss, R. G. The Past, Present, and Future of Molecular Gels. What Is the Status of the Field, and Where Is It Going? J. Am. Chem. Soc. 2014, 136, 7519–7530. 3. Lorber, B.; Sauter, C.; Théobald-Dietrich, A.; Moreno, A.; Schellenberger, P.; Robert, M.-C.; Capelle, B.; Sanglier, S.; Potier, N.; Giegé, R. Crystal Growth of Proteins, Nucleic Acids, and Viruses in Gels. Prog. Biophys. Mol. Biol. 2009, 101, 13–25. 4. Shah, J. C.; Sadhale, Y.; Chilukuri, D. M. Cubic Phase Gels as Drug Delivery Systems. Adv. Drug Deliv. Rev. 2001, 47, 229–250. 5. Hirst, A. R.; Escuder, B.; Miravet, J. F.; Smith, D. K. High-Tech Applications of SelfAssembling Supramolecular Nanostructured Gel-Phase Materials: From Regenerative Medicine to Electronic Devices. Angew. Chem. Int. Ed. 2008, 47, 8002–8018. 6. Suzuki, M.; Hanabusa, K. L-Lysine-Based Low-Molecular-Weight Gelators. Chem. Soc. Rev. 2009, 38, 967–975. 7. Datta, S.; Bhattacharya, S. Multifarious Facets of Sugar-Derived Molecular Gels: Molecular Features, Mechanisms of Self-Assembly and Emerging Applications. Chem. Soc. Rev. 2015, 44, 5596–5637.


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8. Hanabusa, K.; Suzuki, M. Physical Gelation by Low-Molecular-Weight Compounds and Development of Gelators. Bull. Chem. Soc. Jpn. 2016, 89, 174–182. 9. Shigemitsu, H.; Hamachi, I. Design Strategies of Stimuli-Responsive Supramolecular Hydrogels Relying on Structural Analyses and Cell-Mimicking Approaches. Acc. Chem. Res. 2017, 50, 740–750. 10. Kiyonaka, S.; Sugiyasu, K.; Shinkai, S.; Hamachi, I. First Thermally Responsive Supramolecular Polymer Based on Glycosylated Amino Acid. J. Am. Chem. Soc. 2002, 124, 10954–10955. 11. Hill, J. P.; Jin, W.; Kosaka, A.; Fukushima, T.; Ichihara, H.; Shimomura, T.; Ito, K.; Hashizume, T.; Ishii, N.; Aida, T. Self-Assembled Hexa-peri-hexabenzocoronene Graphitic Nanotube. Science 2004, 304, 1481–1483. 12. Ajayaghosh, A.; Praveen, V. K.; Vijayakumar, C. Organogels as Scaffolds for Excitation Energy Transfer and Light Harvesting. Chem. Soc. Rev. 2008, 37, 109–122. 13. Shigemitsu, H.; Hisaki, I.; Senga, H.; Yasumiya, D.; Thakur, T. S.; Saeki, A.; Seki, S.; Tohnai, N.; Miyata, M. Structural Transformation between Supramolecular Nanofibers with Drastic Change of Conductivity by Heat and Ultrasound. Chem. Asian J. 2013, 8, 1372–1376. 14. Inoue, K.; Ono, Y.; Kanekiyo, Y.; Ishii, T.; Yoshihara, K.; Shinkai, S. Design of New Organic Gelators Stabilized by a Host-Guest Interaction. J. Org. Chem. 1999, 64, 2933–2937. 15. Weng, W.; Beck, J. B.; Jamieson, A. M.; Rowan, S. J. Understanding the Mechanism of Gelation and Stimuli-Responsive Nature of a Class of Metallo-Supramolecular Gels. J. Am. Chem. Soc. 2006, 128, 11663–11672.


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16. Shigemitsu, H.; Hisaki, I.; Kometani, E.; Yasumiya, D.; Sakamoto, Y.; Osaka, K.; Thakur, T. S.; Saeki, A.; Seki, S.; Kimura, F.; Kimura, T.; Tohnai, N.; Miyata, M. Crystalline Supramolecular Nanofibers Based on Dehydrobenzoannulene Derivatives. Chem. Eur. J. 2013, 19, 15366–15377. 17. C. Jiaxi, Shen, Z.; Wan, X. Study on the Gel to Crystal Transition of a Novel SugarAppended Gelator. Langmuir, 2010, 26, 97–103. 18. Yajima, T.; Tabuchi, E.; Nogami, E.; Yamagishi, A.; Sato, H. Perfuorinated Gelators for Solidifying Fuorous Solvents: Effects of Chain Length and Molecular Chirality. RSC Adv. 2015, 5, 80542–80547. 19. Ostuni, E.; Kamaras, P.; Weiss, R. G. Novel X-ray Method for In Situ Determination of Gelator Strand Structure: Polymorphism of Cholesteryl Anthraquinone-2-carboxylate. Angew. Chem. Int. Ed. Engl. 1996, 35, 1324–1326. 20. Houton, K. A.; Morris, K. L.; Chen, L.; Schmidtmann, M.; Jones, J. T. A.; Serpell, L. C.; Lloyd, G. O.; Adams, D. J. On Crystal versus Fiber Formation in Dipeptide Hydrogelator Systems. Langmuir 2012, 28, 9797. 21. Piepenbrock, M.-O. M.; Lloyd, G. O.; Clarke, N.; Steed, J. W. Metal- and Anion-Binding Supramolecular Gels. Chem. Rev. 2010, 110, 1960–2004. 22. K. Kohno, K. Morimoto, N. Manabe, T. Yajima, A. Yamagishi, H. Sato, Promotion Effects of Optical Antipodes on the Formation of Helical Fbrils: Chiral Perfluorinated Gelators. Chem. Commun. 2012, 48, 3860–3862.


17


Page 18 of 23

23. Sato, H.; Yajima, T.; Yamagishi, A. An Intermediate State in Gelation as Revealed by Vibrational Circular Dichroism Spectroscopy. RSC Adv. 2014, 4, 25867–25870. 24. Sasaki, T.; Hisaki, I.; Miyano, T.; Tohnai, N.; Morimoto, K.; Sato, H.; Tsuzuki, S.; Miyata, M. Linkage Control Between Molecular and Supramolecular Chirality in 21-Helical HydrogenBonded Networks Using Achiral Components. Nat. Commun. 2013, 4, 1787 (DOI: 10.1038/ncomms2756). 25. Hanabusa, K.; Yamada, M.; Kimura, M.; Shirai, H. Prominent Gelation and Chiral Aggregation of Alkylamides Derived from trans-1,2-Diaminocyclohexane. Angew. Chem. Int. Ed. Engl. 1996, 35, 1949–1951. 26. Sato, H.; Yajima, T.; Yamagishi, A. Chiroptical Studies on Supramolecular Chirality of Molecular Aggregates. Chirality 2015, 27, 659–666. 27. Sato, H.; Yajima, T.; Yamagishi, A. Helical Inversion of Gel Fibrils by Elongation of Perfluoroalkyl Chains as Studied by Vibrational Circular Dichroism. Chirality 2016, 28, 361– 364. 28. Boultif, A.; Louër, D. Powder Pattern Indexing with the Dichotomy Method. J. Appl. Crystallogr. 2004, 37, 724–731. 29. Wolff, P. M. The Definition of the Indexing Figure of Merit M20. J. Appl. Crystallogr. 1972, 5, 243. 30. Smith, G. S.; Snyder, R. L. FN: A Criterion for Rating Powder Diffraction Patterns and Evaluating the Reliability of Powder-Pattern Indexing. J. Appl. Crystallogr. 1979, 12, 60–65.


18

Page 19 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


31. Pawley, G. S. Unit-Cell Refinement from Powder Diffraction Scans. J. Appl. Crystallogr. 1981, 14, 357–361. 32. David, W. I. F.; Shankland, K.; Van de Streek, J.; Pidcock, E.; Motherwell, S. DASH version 3.5, Cambridge Crystallographic Data Centre, Cambridge, U.K., 2004. 33. Rietveld, H. M. A Profile Refinement Method for Nuclear and Magnetic Structures. J. Appl. Crystallogr. 1969, 2, 65–71. 34. Larson, A. C.; Von Dreele, R. B. GSAS, Los Alamos Laboratory, Report No. LA-UR-86-748, Los Alamos National Laboratory, Los Alamos, NM, 1987. 35. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O ̈ .; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, Revision E.01; Gaussian, Inc., Wallingford, CT, 2009.


19


Page 20 of 23

36. Cheeseman, J. R.; Frisch, M. J.; Devlin, F. J.; Stephens, P. J. Ab Initio Calculation of Atomic Axial Tensors and Vibrational Rotational Strengths Using Density Functional Theory. Chem. Phys. Lett. 1996, 252, 211–220. 37. Dennington, R.; Keith, T.; Millam, J. Gauss Views Version 5, Semichem Inc., Shawnee Mission KS, 2009. 38. Bunn, C. W.; Howells, E. R. Structures of Molecules and Crystals of Fluorocarbons. Nature 1954, 174, 549–551. 39. Monde, K.; Miura, N.; Hashimoto, M.; Taniguchi, T.; Inabe, T. Conformational Analysis of Chiral Helical Perfluoroalkyl Chains by VCD. J. Am. Chem. Soc. 2006, 128, 6000–6001. 40. Hasegawa, T.; Shimoaka, T.; Shioya, N.; Morita, K.; Sonoyama, M.; Takagi, T.; Kanamori, T. Stratified Dipole-Arrays Model Accounting for Bulk Properties Specific to Perfluoroalkyl Compounds. ChemPlusChem 2014, 79, 1421–1425. 41. Hasegawa, T. Understanding of the Intrinsic Difference Between Normal- and PerfluoroAlkyl Compounds Toward Total Understanding of Material Properties. Chem. Phys. Lett. 2015, 627, 64–66. 42. Shimoaka, T.; Tanaka, Y.; Shioya, N.; Morita, K.; Sonoyama, M.; Amii, H.; Takagi, T.; Kanamori, T.; Hasegawa, T. Surface Properties of a Single Perfluoroalkyl Group on Water Surfaces Studied by Surface Potential Measurements. J. Colloid Interface Sci. 2016, 483, 353– 359. 43. Cahn, R. S.; Ingold, S. C.; Prelog, V. Specification of Molecular Chirality. Angew. Chem. Int. Ed. Engl. 1966, 5, 385–415.


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Page 21 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


44. Prelog, V.; Helmchen, G. Basic Principles of the CIP-System and Proposals for a Revision. Angew. Chem. Int. Ed. Engl. 1982, 21, 567–583. 45. Etter, M. C. Patterns in Hydrogen Bonding: Functionality and Graph Set Analysis in Crystals. Acc. Chem. Res. 1990, 23, 120–126. 46. Sasaki, T.; Ida, Y.; Hisaki, I.; Yuge, T.; Uchida, Y.; Tohnai, N.; Miyata, M. Characterization of Supramolecular Hidden Chirality of Hydrogen-Bonded Networks by Advanced Graph Set Analysis. Chem. Eur. J. 2014, 20, 2478–2487. 47. Tsuzuki, S.; Uchimaru, T.; Mikami, M.; Urata, S. Magnitude and Orientation Dependence of Intermolecular Interaction Between Perfluoroalkanes: High Level Ab Initio Calculations of and Dimers. J. Chem. Phys. 2002, 116, 3309–3315. 48. Tsuzuki, S.; Uchimaru, T.; Mikami, M.; Urata, S. Magnitude and Orientation Dependence of Intermolecular Interaction of Perfluoropropane Dimer Studied by High-Level Ab Initio Calculations: Comparison with Propane Dimer. J. Chem. Phys. 2004, 121, 9917–9924. 49. Tsuzuki, S.; Honda, K.; Uchimaru, T.; Mikami, M. Estimated MP2 and CCSD(T) Interaction Energies of Alkane Dimers at the Basis Set Limit: Comparison of the Methods of Helgaker et al. and Feller. J. Chem. Phys. 2006, 124, 114304 (1–7). 50. Anthony, S. P.; Basavaiah, K.; Radhakrishnan, T. P. Chiral Vicinal Bis(amide) Molecules: Polar/Helical Assemblies in Crystals and Second Harmonic Generation. Cryst. Growth Des. 2005, 5, 1663–1666.


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51. Bendzińska-Berus, W.; Warżajtis, B.; Gajewy, J.; Kwit, M.; Rychlewska, U. Trityl Group as an Crystal Engineering Tool for Construction of Inclusion Compounds and for Suppression of Amide NH···O═C Hydrogen Bonds. Cryst. Growth Des. 2017, 17, 2560–2568.


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SYNOPSIS. Crystal structure of a low molecular weight organogelator was solved from powder X-ray diffraction patterns, giving knowledge regarding its chirality and crystallization/gelation ability.


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Unusual Molecular and Supramolecular Structures of Chiral Low

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