All biological pumps are autonomous catalysts; they maintain the out-of-equilibrium conditions of the cell by harnessing the energy released from their catalytic decomposition of a chemical fuel. 1-3 A number of artificial molecular pumps have been reported to date, 4 however they are all either fueled by light 5-10 or require repetitive sequential additions of reagents or varying of an electric potential during each cycle to operate 11-16 . Here we report on an autonomous chemicallyfueled information ratchet 17-20 that in the presence of fuel continuously pumps crown ether macrocycles from bulk solution onto a molecular axle without the need for further intervention. The mechanism uses the position of a crown ether on an axle to both promote barrier attachment behind it upon threading and to suppress subsequent barrier removal until the ring has migrated to a catchment region. Tuning the dynamics of both processes 20, 21 enables the molecular machine 22-25 to continuously pump macrocycles from their lowest energy state in bulk solution to a higher energy state on the axle. The ratchet action is experimentally demonstrated by the progressive pumping of up to three macrocycles onto the axle from bulk solution under conditions where barrier formation and removal occur continuously. The out-of-equilibrium [n]rotaxanes (characterised with n up to 4) are maintained for as long as unreacted fuel is present, after which the rings slowly de-thread. The use of catalysis to drive artificial molecular pumps opens up new opportunities, insights and research directions at the interface of catalysis and molecular machinery. Main The structure and mode of operation of the catalysis-driven molecular pump, 1, is shown in Fig. 1. One end of the axle is permanently blocked by a bulky triarylmethine group (brown); the other end of the axle (the N-terminus) is open for threading when in the form of a benzyl amine group (orange). The axle includes a chain of triazole heterocycles linked by short, propyl (-(CH 2 ) 3 -), spacers. Triazoles only

Biological systems exhibit a range of complex functions at the micro-and nanoscale under non-equilibrium conditions (e.g. transportation and motility, temporal control, information processing, etc.). Synthetic chemists also use out-of-equilibrium systems, for example in kinetic selection during catalysis, self-replication, dissipative self-assembly, synthetic molecular machines, and in the form of chemical oscillators. Key to non-equilibrium behavior are the mechanisms through which systems are able to extract energy from the fuel. In this Perspective we consider different examples using a common conceptual framework. We discuss how reaction cycles can be coupled to other dynamic processes through positive (acceleration) or negative (inhibition) catalysis to provide the thermodynamic impetus for diverse non-equilibrium behavior, in effect acting as a chemical engine. We explore the way that the energy released from reaction cycles is harnessed through kinetic selection in a series of what may have previously been considered somewhat disparate fields (systems chemistry, molecular machinery, supramolecular assembly and chemical oscillators), highlight common mechanistic principles, introduce concepts for the synchronization of chemical reaction cycles, and identify future challenges for the invention and application of non-equilibrium systems. MainBiological systems exhibit a broad range of complex functions, from transportation and motility 1-4 to temporal control 5,6 and information processing 7,8 , under non-equilibrium conditions realized by dissipating the chemical potential of high-energy species (typically the hydrolysis of adenosine triphosphate (ATP) or guanosine triphosphate (GTP) [3][4][5]7 ). Synthetic chemists are creating their own non-equilibrium systems, resulting in kinetic selection in catalysis, self-replicating systems 9,10 , dissipative assembly [11][12][13] , synthetic molecular machines 14-17 , and

Information is a physical quantity, a realisation that transformed the physics of measurement and communication in the latter half of the 20th Century. However, the relationship and flow between information, energy and mechanics in chemical systems and mechanisms remains largely unexplored. Here we analyze a minimalist experimental example of an autonomous artificial chemically-driven molecular motor -a molecular information ratchet -in terms of information thermodynamics, a framework that quantitatively relates information to other thermodynamic parameters. This treatment reveals how directional motion is generated by free energy transfer from the chemical to the mechanical processes involving the motor. We find that the free energy transfer consists of two distinct contributions that can be considered as "energy flow" and "information flow". We identify the efficiency with which the chemical fuel powers the free energy transfer and show that this is a useful quantity with which to compare and evaluate mechanisms of, and guide designs for, molecular machines. The study provides a thermodynamic level of understanding of molecular motors that is general, complements previous analyses based on kinetics, and has practical implications for designing and improving synthetic molecular machines, regardless of the particular type of machine or chemical structure. In particular, the study confirms that, in line with kinetic analysis, power strokes do not affect the directionality of chemically-driven molecular machines. However, we also find that under some conditions power strokes can modulate the molecular motor current (how fast the components rotate), efficiency with respect to how free energy is dissipated, and the number of fuel molecules consumed per cycle. This may help explain the role of such conformational changes in biomolecular machine mechanisms and illustrates the interplay between energy and information in chemical systems.

Chemically fueled autonomous molecular machines are catalysis-driven systems governed by Brownian information ratchet mechanisms. One fundamental principle behind their operation is kinetic asymmetry, which quantifies the directionality of molecular motors. However, it is difficult for synthetic chemists to apply this concept to molecular design because kinetic asymmetry is usually introduced in abstract mathematical terms involving experimentally inaccessible parameters. Furthermore, two seemingly contradictory mechanisms have been proposed for chemically driven autonomous molecular machines: Brownian ratchet and power stroke mechanisms. This Perspective addresses both these issues, providing accessible and experimentally useful design principles for catalysis-driven molecular machinery. We relate kinetic asymmetry to the Curtin−Hammett principle using a synthetic rotary motor and a kinesin walker as illustrative examples. Our approach describes these molecular motors in terms of the Brownian ratchet mechanism but pinpoints both chemical gating and power strokes as tunable design elements that can affect kinetic asymmetry. We explain why this approach to kinetic asymmetry is consistent with previous ones and outline conditions where power strokes can be useful design elements. Finally, we discuss the role of information, a concept used with different meanings in the literature. We hope that this Perspective will be accessible to a broad range of chemists, clarifying the parameters that can be usefully controlled in the design and synthesis of molecular machines and related systems. It may also aid a more comprehensive and interdisciplinary understanding of biomolecular machinery.

Photoluminescent coordination nanosheets (CONASHs) comprising three-way terpyridine (tpy) ligands and zinc(II) ions are created by allowing the two constitutive components to react with each other at a liquid/liquid interface. Taking advantage of bottom-up CONASHs, or flexibility in organic ligand design and coordination modes, we demonstrate the diversity of the tpy-zinc(II) CONASH in structures and photofunctions. A combination of 1,3,5-tris[4-(4'-2,2':6',2″-terpyridyl)phenyl]benzene (1) and Zn(BF) affords a cationic CONASH featuring the bis(tpy)Zn complex motif (1-Zn), while substitution of the zinc source with ZnSO realizes a charge-neutral CONASH with the [Zn(μ-OSO)(tpy)] motif [1-Zn(SO)]. The difference stems from the use of noncoordinating (BF) or coordinating and bridging (SO) anions. The change in the coordination mode alters the luminescence (480 nm blue in 1-Zn; 552 nm yellow in 1-Zn(SO)). The photophysical property also differs in that 1-Zn(SO) shows solvatoluminochromism, whereas 1-Zn does not. Photoluminescence is also modulated by the tpy ligand structure. 2-Zn contains triarylamine-centered terpyridine ligand 2 and features the bis(tpy)Zn motif; its emission is substantially red-shifted (590 nm orange) compared with that of 1-Zn. CONASHs 1-Zn and 2-Zn possess cationic nanosheet frameworks with counteranions (BF), and thereby feature anion exchange capacities. Indeed, anionic xanthene dyes were taken up by these nanosheets, which undergo quasi-quantitative exciton migration from the host CONASH. This series of studies shows tpy-zinc(II) CONASHs as promising potential photofunctional nanomaterials.