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In this paper, a unique orthogonal photoresponsive tristable [3]rotaxane molecular shuttle (R1) is constructed, which consists of two CBPQT4+ macrocycles interlocked via a dumbbell component containing three recognition sites, including photoswitchable azobenzene (AB) and naphthalene-derived azobenzene (NP-AB) units separated by a 1,5-dioxynaphthalene (DNP) unit. The two azo units that are encapsulated by the CBPQT4+ macrocycles in the pristine state can be E/Z photoisomerized separately upon irradiation using UV (365 nm) and yellow (>550 nm) light (for the AB unit) and using blue (420–430 nm) and yellow (>550 nm) light (for the NP-AB unit), thus achieving the distinctive orthogonal phototriggered shuttling of the CBPQT4+ macrocycles between the azo and DNP units. This means that charge transfer (CT) absorption (at 620 nm, generated from the NP⊂CBPQT4+ encapsulation complex) related to R1 can be fully photoregulated between three spectral states with good reversibility. Moreover, UV-light-irradiated [2]rotaxane analogues that are embedded with NP-AB or AB units are found to be insensitive to red light (620 nm) irradiation. These features, together with the peculiarity of the orthogonal photo-responsiveness, enable this novel photochromic [3]rotaxane to be potentially applied as a multistate molecular switch or as an optical information storage medium with non-destructive readout.

Low-molecular-weight supramolecular hydrogels are of significant attractive soft materials as particular functions can be facilely introduced by the straightforward fabrication of such self-assembled systems. In this study, an azobenzene-bridged dicationic pyridinium salt was synthesized, from which photoresponsive supramolecular hydrogel could be fabricated through the π-π stacking and hydrophobic interactions in the aqueous solution. By taking advantages of the UV–vis light induced E/Z photoisomerization behaviors of the incorporated azobenzene photochromophore, reversible gel-sol transformation of such supramolecular hydrogel could be achieved under the alternating UV–vis irradiation conditions. We believed that this photoresponsive supramolecular hydrogel will be a good supplementary in the creation of intelligent soft material.

A photoswitchable [2]rotaxane with unique photogated macrocyclic shuttling is constructed by incorporating the photoswitchable azobenzene (AB) and nonphotoactive biphenyl (BP) units into the axle as two terminal recognition sites, bridged by a naphthalene (NAP) unit. The UV (λ = 379 nm)/blue (λ = 440–450 nm) lights triggered Z/E photoisomerization of the AB unit can drive the cyclobis(paraquat-p-phenylene) (CBPQT4+) macrocycle to shuttle between the two terminal recognition sites. Such macrocyclic translational movement can be photogated by a steric barrier generating from the green-light (λ = 520–525 nm)-triggered cycloaddition reaction between the NAP unit on the thread and a triazolinedione (TAD) additive. Upon standing in dark, the photocycloadduct undergoes disassociation which restores the phototriggered macrocyclic shuttling ability. The construction of such photogated photoresponsive molecular shuttle can provide new approach to improve the switching controllability of rotaxane, which is beneficial to fabricate rotaxane-based nanosystems and materials with high performance.

Novel visible-light responsive hydrogen-bonded supramolecular polymers have been successfully constructed by using a linear molecule, which consists of two ureido-pyrimidinone (UPy) moieties connected by a photochromic ortho-tetrafluorinated azobenzene (TFAB) linker. Benefiting from the visible-light responsive feature of the TFAB unit, reversible photoisomerization between the two isomers of the monomer can be achieved. The E-isomer prefers to form a linear supramolecular polymer through the intermolecular quadruple hydrogen bonding interactions between UPys, whereas the Z-isomer facilely forms a cyclic dimer. Therefore, the polymerization mechanisms and properties of such supramolecular polymers, e.g. reversible visible-light induced gel–sol transformation behaviour, can be regulated by the reversible visible-light triggered E/Z photo-isomerization of the TFAB chromophore.

The development of artificial self-assembling systems with dynamic photo-regulation features in aqueous solutions has drawn great attention owing to the potential applications in fabricating elaborate biological materials. Here we demonstrate the fabrication of water-soluble cucurbit[8]uril (CB[8])-mediated supramolecular polymers by connecting the fluorinated azobenzene (FAB) containing monomers through host-enhanced heteroternary π-π stacking interactions. Benefiting from the unique visible-light-induced E→Z photoisomerization of the FAB photochromophores, the encapsulation behaviors between the CB[8] macrocycle and the monomers could be regulated upon visible light irradiation, resulting in the depolymerization of such CB[8]-mediated supramolecular polymers.

Light-triggered photoisomerization of the azobenzene (AB) unit in bistable [2]rotaxanes can cause the shuttling of the macrocycle on the dumbbell, resulting in distinctive dual spectral variation characteristics: (1) the spectral change of the photochromic unit and (2) the variation of the charge-transfer band. By employing the CT bond region as an output signal, non-destructive readout of optical information could be achieved.