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We report a molecular switching ensemble whose states may be regulated in synergistic fashion by both protonation and photoirradiation. This allows hierarchical control in both a kinetic and thermodynamic sense. These pseudorotaxane-based molecular devices exploit the so-called Texas-sized molecular box (cyclo[2]-(2,6-di(1H-imidazol-1-yl)pyridine)[2](1,4-dimethylenebenzene); 1⁴⁺, studied as its tetrakis-PF₆⁻salt) as the wheel component. Anions of azobenzene-4,4′-dicarboxylic acid (2H⁺•2) or 4,4′-stilbenedicarboxylic acid (2H⁺•3) serve as the threading rod elements. The various forms of 2 and 3 (neutral, monoprotonated, and diprotonated) interact differently with 1⁴⁺, as do the photoinducedcisortransforms of these classic photoactive guests. The net result is a multimodal molecular switch that can be regulated in synergistic fashion through protonation/deprotonation and photoirradiation. The degree of guest protonation is the dominating control factor, with light acting as a secondary regulatory stimulus. The present dual input strategy provides a complement to more traditional orthogonal stimulus-based approaches to molecular switching and allows for the creation of nonbinary stimulus-responsive functional materials.

 

The third industrial revolution has brought mankind into the information age. The development of information storage materials has played a key role in this transformation. Such materials have seen use in many application areas, including computing, logistics, and medicine. Information storage materials run the gamut from magnetic information storage media to molecular-based information storage materials. Among these, fluorescent-based information storage materials are of particular interest due to their unique properties, including an ability to store information with high levels of security, maintain mechanical stability, and respond to appropriately chosen external stimuli. In this review, we focus on recent advances involving the preparation and study of fluorescent materials-based information storage codes. For organisational purposes, these codes are treated according to the dimensionality of the code system in question, namely 1D-, 2D-, and 3D-type codes. The present review is designed to provide a succinct summary of what has been accomplished in the area, while outlining existing challenges and noting directions for future development. 

Two giant calix[n]phyrin derivatives namely calix- [8]- (4) and calix[16]phyrin (5), involving two and four BF2 units, respectively, were prepared through the condensation of the bis-naphthobipyrrolylmethene-BF2 complex (3) with pentafluorobenzaldehyde. Calix[n]phyrins 4 and 5 display extremely high extinction coefficients (3.67 and 4.82  105m1cm1, respectively) in the near-IR region, which was taken as initial evidence for strong excitonic coupling within these cyclic multi-chromophoric systems. Detailed insights into the effect of excitonic coupling dynamics on the electronic structure and photophysical properties of the macrocycles came from fluorescence, time-correlated single-photon counting (TCSPC) and transient absorption (TA) measurements. Support for these experimental findings came from theoretical studies. Theory and experiment confirmed that the coupling between the excitons depends on the specifics of the calix- [n]phyrin structure, not just its size. 

β,β′-Phenylene bridged hexaphyrin[1.0.1.0.1.0] (naphthorosarin), an expanded porphyrin possessing C 3v -symmetry, has been shown to possess unique electronic features. We now report a bimetallic Rh( i )-complex of naphthorosarin retaining 24 π-antiaromatic characteristics. The two Rh( i ) cations reside on opposite sides of the macrocyclic π-system and are separated at a distance consistent with a possible Rh( i )–Rh( i ) metallic bond interaction.