Supramolecular Proton Conductors Self-Assembled by Organic Cages

Proton conduction is vital for living systems to execute various physiological activities. The understanding of its mechanism is also essential for the development of state-of-the-art applications, including fuel-cell technology. We herein present a bottom-up strategy, that is, the self-assembly of Cage-1 and -2 with an identical chemical composition but distinct structural features to provide two different supramolecular conductors that are ideal for the mechanistic study. Cage-1 with a larger cavity size and more H-bonding anchors self-assembled into a crystalline phase with more proton hopping pathways formed by H-bonding networks, where the proton conduction proceeded via the Grotthuss mechanism. Small cavity-sized Cage-2 with less H-bonding anchors formed the crystalline phase with loose channels filled with discrete H-bonding clusters, therefore allowing for the translational diffusion of protons, that is, vehicle mechanism. As a result, the former exhibited a proton conductivity of 1.59 × 10–4 S/cm at 303 K under a relative humidity of 48%, approximately 200-fold higher compared to that of the latter. Ab initio molecular dynamics simulations revealed distinct H-bonding dynamics in Cage-1 and -2, which provided further insights into potential proton diffusion mechanisms. This work therefore provides valuable guidelines for the rational design and search of novel proton-conducting materials

Structural studies into πˑˑˑπ interactions and their cooperativity effect on the spin crossover behaviour of a novel series of naphthalimide compounds

The crystal engineering of metal-organic materials is an active area of research in the field of materials science with a wide variety of diverse functions, properties, and promising applications. Prominent work has been pioneered over the last few decades in crystal engineering where structure directing components have been systematically built into molecular building blocks. However, this has not been fully exploited, particularly in the field of magnetically switchable materials. The numerous interesting properties of spin crossover (SCO) active systems, combined with the current trend to develop molecular electronics and machines has resulted in a dramatic increase in the exploration compounds exhibiting this phenomenon. Modifying the solid-state interactions between metal complexes is essential for controlling the nature of the SCO event. One approach to achieve this is to use supramolecular chemistry to assemble complexes into high ordered arrays through non-covalent supramolecular interactions. Hydrogen bonding is typically the main tool used to control the formation of networks in crystal engineering due to its reproducible, well defined, and directional properties. Previous work has investigated the effect that hydrogen bonding and halogen bonding has on the cooperative nature of the SCO event, which proposed that other supramolecular interactions can also alter the nature of this cooperativity. The focus of this work is on utilising π⋯π interactions to systematically modify the SCO transition. The use of π⋯π stacking interactions has been become prevalent since the discovery that the electron density within the π systems defines the strength of the interaction. The established order of stability in the interaction of two π systems is π-deficient⋯π-deficient > π-deficient⋯πrich > π-rich⋯π-rich. A key aim of this project is to exploit π⋯π stacking interactions for the engineering of magnetically switchable metal-organic supramolecular networks. Naphthalimide-based functional groups were identified as the target for this project because of: a) their inherent ability to induce SCO in Fe(II); b) the long range ordering achieved through πstacking and c) the interesting photophysical properties of the 1,8-naphthalimide moiety. The electron deficient 1,8-naphthalimide systems have not only been utilised as ligand scaffolds for metal complexes, but also investigated as non-coordinating anions to incorporate this structure directing group into the lattice. While systematically varying the nature of substituents on naphthalimide backbone, we will use quantum crystallography methods to develop an understanding of how subtle changes in electron withdrawing/donating substituents influence the nature of interactions, and accordingly how π⋯π interactions influence magnetic properties. The calculation of the intermolecular interaction energies has resulted in an array of information which provides insights, that we wish to develop into detailed structure function relationship, thereby increasing control over the behaviour of magnetic materials

descriptor data

<p>descriptor data</p

Dataset for JMP

<p>Dataset for JMP</p

Report for data driven

<p>Report for data driven</p

3D

<p>3D</p

Markush structure for 19,25

<p>Markush structure for 19,25</p

Markush structure for 5,6,7,8,9,10,11,12

<p>Markush structure for 5,6,7,8,9,10,11,12</p