Achiral substituent- and stoichiometry-controlled inversion of supramolecular chirality and circularly polarized luminescence in ternary co-assemblies†

Fang Wang *, Liyun Lai , Min Liu , Quan Zhou * and Shaoliang Lin *
School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China. E-mail: 1509wangfang@ecust.edu.cn; qzhou@ecust.edu.cn; slin@ecust.edu.cn

First published on 28th March 2024

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Introduction

Supramolecular chirality, which represents periodic asymmetrical packing of molecules via noncovalent interactions, relates intimately to biomimetics,¹ chiral sensing,² asymmetric catalysis,³ optics,⁴ electronic materials,⁵ and circularly polarized luminescence (CPL).^6–9 One of the pivotal issues in supramolecular chirality is controlled chiral inversion.^10–15 This can be achieved by various external stimuli such as temperature,¹⁶ solvents,¹⁷ light,¹⁸ metal ions,¹⁹ pH,²⁰ and redox.²¹ However, most of the reported supramolecular chirality inversions have focused on single-component self-assembled systems,^22–25 and both basic and application research studies of multiple-component co-assemblies with controllable chirality are still limited. The study of supramolecular chirality inversion in multicomponent systems not only benefits simulation of complicated biosystems, but also provides considerable meaning to the rational design and manufacture of advanced chiroptical materials.^26–28

Multicomponent molecular self-assembly refers to the spontaneous aggregation of two or more molecules into specific structures at any scale through noncovalent forces including π–π stacking, charge-transfer, complementary hydrogen bonds, and electrostatic attraction.^29–32 In this process, not only the chiral species but also achiral ones could possibly exert significant influence on the regulation of supramolecular chirality.^33–35 By using different achiral species for co-assembly, the supramolecular chirality can be inverted in some two-component assemblies.^36,37 Typically, when various achiral fluorescent molecules are introduced into two-component assemblies, chirality can be transferred to the luminophores with easily achieved CPL-inversion properties.^38–40 In spite of these developments, the construction of three-component assemblies would provide more efficient and flexible ways to manipulate supramolecular chirality as well as CPL handedness.^41–45 However, since the systematic pathway complexity is magnified dramatically with increasing components, it is highly challenging to construct an integrated molecular self-assembly with ordered structures from ternary organic building units.

Herein, co-assembled ternary supramolecular systems composed of chiral fluorenylmethyloxycarbonyl (Fmoc)-protected phenylalanine (Phe) and leucine (Leu), achiral vinylnaphthalene derivatives (NC1, NC2 and NP), and 1,2,4,5-tetracyanobenzene (TCNB) were developed (Fig. 1). The supramolecular chirality of the ternary co-assemblies can be inverted by changing the Fmoc-amino acid residues. Typically, the supramolecular chirality can be further inverted by changing the position and the structure of substituted ethylene groups in the naphthalene ring of vinylnaphthalene derivatives. In particular, stoichiometry-induced inversion of supramolecular chirality was observed in Leu/NC2/TCNB co-assembled systems. Similar chirality inversions in the excited states were also observed in ternary systems, indicating the excellent repeatability of these phenomena. These inversions of supramolecular chirality and CPL as a result of three-component co-assembly were observed to be mainly mediated through alterations in hydrogen bonding interactions between Fmoc-amino acids and vinylnaphthalene derivatives with achiral substituents and stoichiometry variations, affecting the charge transfer and hydrogen bonding network responsible for packing pattern differences in the co-assemblies.

Results and discussion

The self-assembly of different components was triggered by injecting deionized water into a minimal concentration stock solution in dimethyl sulfoxide (DMSO), followed by aging for at least 24 h. Both precipitates and gels were observed and characterized using UV-vis absorption spectra and fluorescence spectra (Fig. 2 and Fig. S1–S7†). L-Leu, NC1, NC2, NP and TCNB themselves formed precipitates with extremum photoluminescence (PL) emission peaks in the region of 335–418 nm, while a white gel with blue emission around 336 nm was obtained for L-Phe (Fig. S1 and S2†). After co-assembly, precipitates with green emission (502 nm) were formed for L-Phe/NP and L-Leu/NP (Fig. S3†). The absorption and emission spectra of both the co-assemblies showed an obvious red-shift due to the formation of hydrogen bonding between carboxyl and pyridyl groups (Fig. S4†). When changing the substituents of the incorporated vinylnaphthalenes from pyridyl (NP) to carboxyl (NC1 and NC2), L-Phe-based co-gels and L-Leu-based suspensions with blue emission (430–435 nm) were formed. The Fmoc-amino acids including L-Phe and L-Leu failed to form fluorescent charge transfer (CT) complexes with TCNB due to the self-sorting processes (Fig. S2 and S5†).^46,47 However, CT complexation between vinylnaphthalene derivatives (NC1, NC2 and NP) and TCNB generated stable yellow emission (Fig. S2†). Furthermore, new absorption bands with different intensities appeared in the region of 400–500 nm (Fig. S5†), which can be attributed to the different CT interactions from the vinylnaphthalene derivative donors to TCNB. From the corresponding emission spectra, the structureless and red-shifted peaks in the range of 525–535 nm were assigned CT emissions. In the presence of Fmoc-amino acids, these CT absorption and emission bands of NC1/TCNB and NC2/TCNB had no obvious change (Fig. 2a, b and Fig. S6, S7†), suggesting that the CT complexes were preserved in the ternary assembly systems. However, the CT emission band of NP/TCNB reflected a noticeable blue-shift phenomenon after introducing Fmoc-amino acids. The hydrogen bonding between carboxyl and pyridyl groups is considered to play an important role in the observed blue-shifted emission.

Since the amino acids have chiral centers, these self-assemblies were characterized using circular dichroism (CD) spectra to study the ground-state supramolecular chirality. Mirror-image CD signals were detected for the L- and D-Fmoc-amino acids (Phe and Leu) in the region of 250–350 nm (Fig. S8 and S9†). No CD signal was observed both for the individual NC1, NC2, NP, and TCNB and their CT complexes due to their achiral nature. When mixing Fmoc-amino acids with TCNB, the CD spectra only reflected the characteristics of Fmoc-amino acids because of the self-sorting behavior. However, new positive Cotton effects at 377 and 330 nm were observed for L-Phe/NC1 and L-Phe/NC2, respectively (Fig. S10†). This observation should be attributed to the absorption band of NC (NC1 or NC2), indicative of the nonsymmetrical spatial molecular arrangement of NC within the two-component co-assembly array. Moreover, the CD signal intensity increased with the ratio changing from 1:0.2 to 1:1 and decreased with the ratio of L-Phe/NC increasing from 1:1.5 to 1:2 (Fig. S11†). Therefore, the molar ratio of 1:1 was used in the two-component co-assembly. Similar chiral phenomena were also observed in Leu/NC1 and Leu/NC2. By changing the substituent at the vinyl group, L-Phe/NP showed a negative Cotton band at 400 nm compared to the positive band in L-Phe/NC co-assemblies, implying chirality inversion. In contrast to Phe, Leu showed inactive Cotton effects after the complexation with NP. Varying the configuration from the L- to the D-enantiomer gave well-defined mirror CD spectra for the co-assemblies (Fig. S10†). These observations suggested that effective chirality transfer was achieved from the Fmoc-amino acids to the vinylnaphthalene derivatives and the supramolecular chirality of the two-component assemblies could be inverted by changing the structure of substituents in the achiral molecules.

We further leveled up systematic complexity by introducing the electron-deficient TCNB by considering that (1) TCNB could form CT complexes with the electron-rich π-conjugated naphthalene moieties, which would extend the chiroptical properties such as luminescence colors and (2) the three-component co-assembly would provide more efficient and flexible ways for manipulating the supramolecular chirality. Compared to the binary assemblies, strong mirror-image CD signals were observed for all the ternary assemblies (1:1:1 molar ratio), in which obvious CD signals were detected corresponding to the wide CT absorption bands beyond 410 nm (Fig. 2a and c). This suggested the CT interactions between TCNB and naphthalene moieties and the chirality transfer from the amino acids to the CT complexes. Moreover, because the spectra of the ternary mixtures were distinct from those of the single- or two-component assemblies (Fig. 2c and Fig. S8–S11†), it was reasonable to deduce the formation of ternary co-assembled chiral systems. A negative Cotton effect at 500 nm was observed for the CT band of co-assembled L-Phe/NC1/TCNB, whereas a positive Cotton effect was detected for L-Phe/NC2/TCNB at 500 nm. The opposite sign of the CD signals implied that reversed supramolecular chirality could be obtained by varying the location of the acrylic acid group from the α- to the β-position in the naphthalene ring of achiral vinylnaphthalene derivatives. By changing the amino acid residues, a negative Cotton effect for the CT band of L-Leu/NC1/TCNB was obtained at 490 nm. However, compared to L-Phe/NC2/TCNB, L-Leu/NC2/TCNB exhibited an opposite CD signal with a negative Cotton peak at 475 nm, suggesting supramolecular chirality inversion. A similar chirality inversion result was obtained in L-Phe/NP/TCNB and L-Leu/NP/TCNB as confirmed by their opposite CD signals. Apparently, the supramolecular chirality of the ternary assemblies was not only determined by the substituents of the achiral electron donor molecules but also affected by amino acid residues, which differed from those of the binary assemblies.

The excited-state supramolecular chirality of the multicomponent assemblies was measured using CPL spectra. Unfortunately, the binary assemblies of the Fmoc-amino acids and NC displayed almost silent CPL signals (Fig. S12†), although obvious dissymmetric optical properties were observed in CD spectra. For Leu/NP assemblies, no CPL was detected corresponding to the lack of CD signals. Only Phe/NP in two-component systems showed weak green CPL at around 510 nm with the dissymmetry g_lum factor (g_lum = 2 × (I_L − I_R)/(I_L + I_R)) at a 10⁻⁴ order of magnitude. However, yellow CPL emissions (535–560 nm) were detected in ternary co-assemblies (Fig. 2d and Fig. S13†), which are assigned to the CT emission region. Therefore, we successfully fabricated ternary co-assemblies where Fmoc-amino acids, vinylnaphthalene derivatives, and TCNB interacted synergistically. L-Phe/NC1/TCNB assemblies showed a positive CPL signal (left-handed), while L-Phe/NC2/TCNB assemblies displayed a negative CPL signal (right-handed), implying an inversion of CPL handedness. This result further confirmed the conclusion regarding the impact of substitution position on supramolecular chirality. By only changing the substituent of the incorporated achiral vinylnaphthalene derivatives from carboxyl to pyridyl, L-Phe/NP/TCNB assemblies exhibited handedness-inversed CPL compared to L-Phe/NC1/TCNB. Meanwhile, L-Leu/NC2/TCNB and L-Leu/NP/TCNB assemblies displayed positive CPL signals opposite to the corresponding ternary assemblies containing L-Phe, again reflecting an inversion of CPL handedness. These behaviors were further confirmed by the corresponding ternary co-assemblies derived from the other enantiomer D-Fmoc-amino acids. However, the CPL handedness of the ternary co-assemblies comprising Leu, NC (or NP), and TCNB is determined by the absolute chirality of Leu, which gave rise to left-handed CPL and right-handed CPL in cases of L- and D-enantiomers, respectively. These results are in good agreement with the CD results. The ternary co-assemblies afforded g_lum at a 10⁻³ order of magnitude (Fig. S13†). Overall, the ternary co-assemblies not only exhibited CPL signals in the CT emission bands, but also the handedness of CPL could be efficiently inverted by changing the achiral substituents including the Fmoc-amino acid residues and the spatial positions and structures of the substituents in achiral vinylnaphthalene derivatives.

To reveal the morphology of the assemblies, scanning electron microscopy (SEM) was employed. Irregular nanostructures were formed for the individual NC1, NC2, NP, and TCNB assemblies, while nanofibers with diameters ranging from 490 to 950 nm were obtained for the Phe and Leu assemblies (Fig. S14†). After the two-component co-assembly, thinner nanofibers with diameters of 515, 243, and 42 nm were also observed for the assemblies of Phe with NC1, NC2, and NP, respectively (Fig. S15†). For the binary co-assemblies of Leu/NC (or NP) and NC (or NP)/TCNB, the nanofibers and irregular nanostructures from the individual assemblies were absent. Leu/NP and Leu/NC1 assemblies were present as curved nanoribbons and hierarchical microstructures consisting of nanoflakes, respectively. Meanwhile, plates with different widths ranging from 74 to 790 nm formed in the Leu/NC2, NC1/TCNB, NC2/TCNB, and NP/TCNB assemblies (Fig. S15 and S16†). However, both nanofibers of Phe and irregular structures of TCNB were observed simultaneously for Phe/TCNB, suggesting a self-sorting process. For the failed CT complexation of Leu/TCNB, the nanofibers retained the Leu morphology. For the ternary assemblies, nanofibers with diameters of 365, 170, and 23 nm were obtained for Phe/NC1/TCNB, Phe/NC2/TCNB, and Phe/NP/TCNB, respectively (Fig. 3 and Fig. S17†). The sizes of the nanofibers were different from those of the one- or two-component assemblies. However, by using different kinds of amino acids, different morphologies of microflower-, microsheet-, and nanoribbon-assembled dendritic hierarchical structures were observed for Leu/NC1/TCNB, Leu/NC2/TCNB, and Leu/NP/TCNB, respectively. The SEM studies indicated the highly ordered molecular arrangements of these three kinds of components and how a slight change in the molecular structure of the building blocks dramatically influenced the co-assembly behavior.

We then varied the content of TCNB to examine the influence of the stoichiometric ratio on the induced supramolecular chirality. When fixing the molar ratio of Fmoc-amino acids and vinylnaphthalene derivatives at 1:1 and gradually increasing the concentration of TCNB (from 1:1:0 to 1:1:2), the intensity of CD signals from CT complexation first increased and then decreased, reaching a maximum at 1:1:1 molar ratio for the ternary assemblies with the exception of Leu/NC2/TCNB (Fig. 4a and Fig. S18, S19†). It was found that the CD signal for the CT band of the L-Leu/NC2/TCNB co-assemblies gradually enhanced with the increasing concentration of TCNB, and reached the maximum when the molar ratio of L-Leu/NC2/TCNB was 1:1:1. However, the CD spectral profiles were inverted and gradually increased in intensity when adjusting the ratio of L-Leu/NC2/TCNB from 1:1:1.5 to 1:1:2. Further increases in the ratio of L-Leu/NC2/TCNB to 1:1:2.5 or higher would weaken the chiroptical activity in the CD spectra, indicating that the optimum molar ratio for inverting the supramolecular chirality is L-Leu/NC2/TCNB = 1:1:2 (Fig. 4b). We also measured the CPL spectra between Leu/NC2/TCNB = 1:1:1 and 1:1:2 carefully. As shown in Fig. 4c and Fig. S13,† surprisingly, the CPL with g_lum at 10⁻³ grade inverted from L-Leu/NC2/TCNB = 1:1:1 to 1:1:2. In the case of D-Leu/NC2/TCNB, the mirror images of the CD and CPL spectra were obtained. Meanwhile, the opposite inversion of supramolecular chirality could be observed from the ternary co-assemblies of D-Leu/NC2/TCNB. The stoichiometry-controlled inversion of supramolecular chirality both in the ground and excited states is quite different from that of the previous multiple-component co-assembled systems.^48,49

To clarify how the stoichiometric ratio affects the induced supramolecular chirality, further investigations were conducted for the Leu/NC2/TCNB assemblies at the molar ratios of 1:1:1 and 1:1:2. The CT absorption peak of Leu/NC2/TCNB = 1:1:2 was slightly red-shifted and the CT emission band was red-shifted by 10 to 531 nm compared with that of Leu/NC2/TCNB = 1:1:1 (Fig. 4d and e). Thus, it was inferred that enhanced charge transfer occurred between NC2 and TCNB, rather than the CT effect of the Leu-TCNB component, and a sandwich stacked modality with a 1:2 (NC2:TCNB) binding ratio might form in the co-assembly. The 1:2 stoichiometry of NC2:TCNB was further proved by the red-shifted CT absorption and emission bands of NC2/TCNB = 1:2 compared with that of NC2/TCNB = 1:1. The SEM images for Leu/NC2/TCNB = 1:1:1 showed two-dimensional microplates (Fig. 4f). However, flower-like microstructures were observed for Leu/NC2/TCNB = 1:1:2, indicating distinct co-assembly behaviors according to the stoichiometric ratio.

In order to further understand the mechanism of chirality transfer and the inversion of the chiral signal and clarify the molecular stacking mode of the co-assemblies, we analysed the assemblies by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). FTIR spectral results indicated that intermolecular hydrogen bonds between amide/pyridine units and carboxylic acid groups were formed for all the amino acid-based two- or three-component co-assemblies (Fig. 5a–c and Fig. S20†). Typically, the co-assembly enabled spectroscopic variations of individual assemblies. The FTIR spectrum of L-Phe/NC1 assemblies displayed the amide I band at 1618 cm⁻¹, the amide II band at 1536 cm⁻¹, and stretching vibration bands of CO from carboxyl groups at 1718 and 1686 cm⁻¹, which were different from those of the respective L-Phe and NC1 self-assemblies (Fig. 5a and Fig. S20†). The observations implied the formation of hydrogen bond networks through the amide and carboxylic acid units in the co-assemblies. However, for L-Phe/NC1/TCNB assemblies, we did not notice any obvious shift change in the FTIR spectrum compared to that of the L-Phe/NC1 assemblies, suggesting that the hydrogen bonds from the amide and carboxylic acid moieties remained intact. Moreover, the amide I maximum for L-Phe/NC2/TCNB occurred at a higher (8 cm⁻¹) frequency than that for L-Phe/NC1/TCNB, indicating a decrease in amide hydrogen-bonding. However, L-Phe/NP/TCNB assemblies showed that the amide I band shifted from 1618 to 1625 cm⁻¹, the amide II band shifted from 1536 to 1539 cm⁻¹, and new bands at 1690 and 1589 cm⁻¹ were observed compared to that for L-Phe/NC1/TCNB (Fig. 5a and b). This suggested the formation of carboxylic acid–pyridine hydrogen bonds and a change in the hydrogen bonding pattern within the amide groups of L-Phe/NP/TCNB upon changing the substituent of vinylnaphthalene derivatives from carboxyl to pyridyl. Furthermore, when the amino acid residues were changed from Phe to Leu residues, the stretching vibration bands of L-Phe/NP/TCNB at 1720 and 1690 cm⁻¹ disappeared and a new strong vibrational band at 1714 cm⁻¹ was observed in L-Leu/NP/TCNB. This indicated that the carboxylic acid–pyridine hydrogen bonds were affected to some extent by the steric hindrance of the amino acid residue. For Leu-based assembled systems, compared with L-Leu exhibiting an amide II band at 1541 cm⁻¹ and carboxylic bands at 1720 and 1679 cm⁻¹, a broad carboxylic band of L-Leu/NC2 centered at 1698 cm⁻¹ was observed, and a strong amide I band at 1623 cm⁻¹ emerged (Fig. 5c and Fig. S20†), thus verifying the co-assembly between L-Leu and NC2. However, for L-Leu/NC2/TCNB = 1:1:1, the broad carboxylic band of L-Leu/NC2 centred at 1698 cm⁻¹ split into two bands at 1717 and 1687 cm⁻¹, implying that the hydrogen bonds were changed by the charge transfer between NC2 and TCNB. Upon further increasing the amount of TCNB, the carboxylic band at 1687 cm⁻¹ shifted to 1698 cm⁻¹, the amide I band shifted from 1626 to 1635 cm⁻¹ and a smaller amide II band centered at 1533 cm⁻¹ was observed for L-Leu/NC2/TCNB = 1:1:2. The results demonstrated that the amide–amide and carboxylic acid–carboxylic acid hydrogen bonding interactions became weaker upon changing the L-Leu/NC2/TCNB molar ratio from 1:1:1 to 1:1:2. Therefore, charge transfer complexes of 1:2 stoichiometry formed between NC2 and TCNB altered the hydrogen bonding mode. FTIR studies confirmed that the primary driving forces for the ternary co-assemblies were cooperative hydrogen bonds of different types including amide–amide, carboxylic acid–pyridyl, and carboxylic acid–carboxylic acid hydrogen bonds. The multiple hydrogen bonds play a pivotal role in chirality transcription owing to their highly selective and directional characteristics. Thus, it was suggested that the formation of ternary co-assemblies with different chiroptical properties may be attributed to synergistic effects of these different kinds of hydrogen bonding interactions.

Molecular packings of the ternary co-assemblies were probed by XRD analysis (Fig. 5d–f and Fig. S21†). Different from the one- or two-component assemblies, the powder XRD patterns of the ternary co-assemblies demonstrated new peaks, indicating that a new phase was very likely formed. For example, the scattering pattern of the L-Phe/NC2/TCNB system was distinguishable and totally different from that of L-Phe, NC2, TCNB, L-Phe/NC2, and NC2/TCNB assemblies (Fig. 5d and Fig. S21†). After excluding these combinations, new diffraction peaks were found at 1.51 and 0.71 nm (1/2), suggesting a lamellar molecular packing mode. However, the emerged band at 0.78 nm was contributed by the ternary co-assembly of L-Phe/NC1/TCNB. XRD plots of L-Phe/NP/TCNB, L-Leu/NP/TCNB, and L-Leu/NC2/TCNB also displayed the presence of lamellar structures with the interlayer spacings of 1.19 and 0.61, 1.24 and 0.62, and 1.25 and 0.62 nm, respectively (Fig. 5e and f). However, the XRD pattern of the L-Leu/NC2/TCNB = 1:1:2 assemblies showed significant differences from that of the L-Leu/NC2/TCNB = 1:1:1 assemblies. The corresponding d-spacings were 1.51 and 0.75 nm (1/2), suggesting that a lamellar structure was still formed with a larger d-spacing (1.51 nm) than that for L-Leu/NC2/TCNB = 1:1:1 (1.25 nm). These XRD results demonstrated the presence of lamellar arrangements and the diverse stacking features of aggregation in the ternary co-assemblies.

It is clear from the above results that the Fmoc-amino acids, the vinylnaphthalene derivatives and TCNB could synergistically co-assemble at the molecular scale. The ternary assemblies exhibited strong CD and CPL signals because of the chirality transfer from the chiral Fmoc-amino acids to the achiral luminous CT complexes. Notably, the CD and CPL signals of the ternary co-assemblies were successfully inverted by variations of the α-substituents of Fmoc-amino acids, the position and the structure of substituted ethylene groups in the naphthalene ring of vinylnaphthalene derivatives, and the stoichiometry. The underlying mechanisms for such transfer and inversion are illustrated in Fig. 5g. First, the Fmoc-amino acids combine with NC or NP through carboxylic acid–carboxylic acid or carboxylic acid–pyridyl hydrogen bonds and form ordered lamellar structures, in which TCNB interacts with the naphthalene moiety in a ratio of 1:1. Second, these layers serve as basic repeat units and further hierarchically self-assemble into higher order structures, in which multiple layers are stacked mainly via amide–amide hydrogen bonds and CT interactions. However, the transfer of chirality from the chiral center to the donor–acceptor fluorophore is strongly dependent on the spatial arrangement of these three component molecules. Structural parameters are crucial to packing modality, namely the steric hindrance of amino acid residues and the substituent position and structure in the present systems. These factors have a dramatic influence on the primary forces driving the co-assembly including amide–amide, carboxylic acid–pyridyl and carboxylic acid–carboxylic acid hydrogen bonds, which lead to the different packing modes, further changing the distorted direction of the molecules and thus causing the CD and CPL inversion. However, for the assemblies of L-Leu/NC2/TCNB = 1:1:2, one naphthalene unit from the NC2 molecule interacted with two TCNB molecules as confirmed by the stronger CT interactions and the weaker amide–amide and carboxylic acid–carboxylic acid hydrogen bonding interactions than those for L-Leu/NC2/TCNB = 1:1:1. The slightly different packing modes of the two CT complexes produced chiral species of the layer membranes with opposite handedness and different higher ordered structures (microplates at 1:1:1 and microflowers at 1:1:2 molar ratios), finally achieving the inversion of the CD and CPL signals. The noncovalent interactions and the molecular packing could be confirmed using the UV-vis and fluorescence spectra, and FTIR, SEM and XRD measurements.

Conclusions

In summary, ternary co-assemblies with steerable CPL have been fabricated from chiral aromatic amino acids, achiral vinylnaphthalene derivatives, and TCNB. Supramolecular chirality and CPL handedness of the ternary co-assemblies can be inverted by adjusting the stoichiometric ratio or altering the achiral substituents including the amino acid residues and the position and the structure of substituted ethylene groups in the naphthalene ring. A delicate balance between the different types of hydrogen bonding and charge transfer interactions and different molecular packing modes is proposed to account for the handedness inversion. This work provides an alternative route for efficiently avoiding pathway complexity to afford precise manipulation of ternary co-assemblies with desired chiroptical properties, which is helpful for better understanding of the subtle relationship between the molecular structure and supramolecular chirality and may show potential applications in chiral sensing and photoelectric devices.

Author contributions

Fang Wang contributed to conceiving and designing the experiments, supervision, project administration and funding acquisition. Liyun Lai participated in the acquisition of data. Fang Wang and Liyun Lai wrote the manuscript. Min Liu provided language help. Quan Zhou and Shaoliang Lin revised the manuscript and contributed to supervision and project administration. All the authors discussed the results and contributed to the manuscript.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (52303271) and the Fundamental Research Funds for the Central Universities (JKD01221663).

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Footnote

† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d4nr00392f

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