ABSTRACT
The canonical double helical π-stacked array of base pairs within DNA interior has inspired the interest in supramolecular double helical architectures with advanced electronic, magnetic and optical functions. Here, we report a selective-recognized and chirality-matched co-assembly strategy for the fabrication of fluorescent π-amino acids into double helical π-aggregates, which show exceptional strong circularly polarized luminescence (CPL). The single crystal structure of the optimal combination of co-assemblies shows that the double-stranded helical organization of these π-amino acids is cooperatively assisted by both CH-π and hydrogen-bond arrays with chirality match. The well-defined spatial arrangement of the π-chromophores could effectively suppress the non-radiative decay pathways and facilitate chiral exciton couplings, leading to superior CPL with a strong figure of merit (glum = 0.14 and QY = 0.76). Our findings might open a new door for developing DNA-inspired chiroptical materials with prominent properties by enantioselective co-assembly initiated double helical π-aggregation.
Subject(s)
DNA , LuminescenceABSTRACT
The construction of chiroptical materials with controllable chirality is of special importance in biology and chemistry. Although tunable chirality can be realized in various systems, it remains a fundamental challenge to realize multimodulated chiral inversion. Herein, we report that chiral alanine derivative and fluorescent cyanostilbene derivative co-assemble to prepare supramolecular chiral systems, where twist nanofibers with totally inverted supramolecular chirality and circularly polarized luminescence are obtained through stoichiometric modulation. The supramolecular handedness can be inverted by means of altering the cooling rate and incorporating metal ions. The mechanism study reveals that the synergistic effect among hydrogen bonds, coordination interactions, and π-π stacking interactions contributes to the chirality inversion. This work establishes an effective strategy to precisely modulate supramolecular chirality in multiple ways, which shows great potential in developing smart chiroptical materials capable of achieving complex functionalities.
ABSTRACT
Switchable inversion of the sign of circularly polarized luminescence (CPL) in chiral supramolecular systems has gained remarkable interest because of its role in understanding the chirality-switching phenomena in biological systems and developing smart chiral luminescent materials. Herein, inspired by the histidine proton shuttle in natural enzymes, we synthesized a histidine π-gel (PyC3H) and realized reversible inversion of supramolecular chirality and CPL by receiving and then transferring a proton. It was found that in the course of histidine protonation by adding an external proton source, the transcription of intrinsic molecular chirality of PyC3H to the supramolecular level biased, achieving dynamic control over the PyC3H gel with left-handed CPL inversed into the right-handed one. The mechanism study revealed that the supramolecular chirality and CPL inversion are mainly affected by the cooperation adjustment of hydrogen bonds and π-π stacking upon histidine protonation and deprotonation, which causes the re-orientations of pyrene chromophores. This work sets up an alternative effective method to fabricate tunable CPL-active materials while using the same chiral small molecules, which provides a new insight into developing bio-inspired switchable supramolecular materials.
Subject(s)
Histidine/chemistry , Luminescent Measurements/methods , Circular Dichroism , Hydrogen Bonding , Protons , Quantum Theory , StereoisomerismABSTRACT
The selective interplay between dimensional morphology transition and signal transfer is an important feature for both nanomaterials and biosystems. While most of those reported examples considered either dimensional transition or signal transfer, the integrated interplay or selectivity for these two aspects in single self-assembled system has been rarely studied. Here, we report that a positively charged chiral π-building block could self-assemble into multidimensional nanostructures, which showed tunable circularly polarized luminescence (CPL). Impressively, when these CPL-active multidimensional structures interacted with two achiral dyes (positively charged ThT and negatively charged CNA), 3D nanocubes and 0D nanospheres showed neither chirality transfer nor energy transfer, while 2D nanoplates could successfully trigger a selective chirality or energy transfer depending on the charge type of acceptor dyes, which then emitted an enhanced CPL signal. This work demonstrated rational design of charged π-building block for the construction of dimension controllable and selective signal transfer self-assembly system, which might deepen the understanding the interplay of dimensional structures and signal transfer functions in natural and nano systems.
ABSTRACT
A cyanostilbene conjugated gelator was incorporated into the cavities of cyclodextrins via the host-guest interaction and the resulting supra-gelator from γ-CyD enabled chiroptical photo-switching, while the other gels showed enhanced circularly polarized luminescences.
ABSTRACT
Multiple noncovalent interactions can drive self-assembly through different pathways. Here, by coordination-assisted changes in π-stacking modes between chromophores in pyrene-conjugated histidine (PyHis), a self-assembly system with reversible and inversed switching of supramolecular chirality, as well as circularly polarized luminescence (CPL) is described. It was found that l-PyHis self-assembled into nanofibers showing P-chirality and right-handed CPL. Upon ZnII coordination, the nanofibers changed into nanospheres with M-chirality, as well as left-handed CPL. The process is reversible and the M-chirality can change to P-chirality by removing the ZnII ions. Experimental and theoretical models unequivocally revealed that the cooperation of metal coordination and π-stacking modes are responsible the reversible switching of supramolecular chirality. This work not only provides insight into how multiple noncovalent interactions regulate self-assembly pathways.
ABSTRACT
A naphthalene substituted histidine derivative was found to form an organogel showing circularly polarized luminescence (CPL) and the addition of non-fluorescent achiral benzoic acids could efficiently enhance the CPL via non-covalent interactions.