Tuning the Photo-electrochemical Performance of RuII -Sensitized Two-Dimensional MoS2.

Covalently tethering photosensitizers to catalytically active 1T-MoS2 surfaces holds great promise for the solar-driven hydrogen evolution reaction (HER). Herein, we report the preparation of two new RuII -complex-functionalized MoS2 hybrids [RuII (bpy)2 (phen)]-MoS2 and [RuII (bpy)2 (py)Cl]-MoS2 . The influence of covalent functionalization of chemically exfoliated 1T-MoS2 with coordinating ligands and RuII complexes on the HER activity and photo-electrochemical performance of this dye-sensitized system was studied systematically. We find that the photo-electrochemical performance of this RuII -complex-sensitized MoS2 system is highly dependent on the surface extent of photosensitizers and the catalytic activity of functionalized MoS2 . The latter was strongly affected by the number and the kind of functional groups. Our results underline the tunability of the photovoltage generation in this dye-sensitized MoS2 system by manipulation of the surface functionalities, which provides a practical guidance for smart design of future dye-sensitized MoS2 hydrogen production devices towards improved the photofuel conversion efficiency.

Balancing connectivity with function in silver(i) networks of pyridyltriazole (tzpa) ligands results in the formation of a metallogel.

A new flexible and divergent 1,2,3-triazol-4-yl-picolinamide (tzpa) ligand 2 and the half-equivalent model ligand 1, both functionalised with pendant 3-pyridyl groups, are reported and their coordination behaviour with silver(i) ions is explored, both in the crystalline phase and through the formation of a supramolecular metallogel. The self-assembly of tzpa ligand 1 with AgCF3SO3 resulted in the formation of a 1D coordination polymer, binding in a bidentate fashion through the pyridyl and triazole nitrogen atoms of the tzpa binding site and a pendant pyridyl nitrogen atom of an adjacent ligand. Doubling the number of metal binding sites in ligand 2, while retaining the same metal binding domain, gives rise to the formation of a supramolecular metallogel on reaction with AgBF4 at 5 wt% in MeCN, possessing self-healing properties.

Fluorescent supramolecular hierarchical self-assemblies from glycosylated 4-amino- and 4-bromo-1,8-naphthalimides.

An investigation into the self-assembly of two 4-amino- and a 4-bromo-1,8-naphthalimide (Nap) based structures (1-3) possessing an appended glycan unit, from protic polar media, is presented. The results demonstrate the formation of complex hierarchical luminescent aggregates, wherein the morphologies, sizes and spherical structures were highly dependent on both the media and the Nap structure. Upon cleaving the native glycosidic bond, using an enzyme, the structure/morphology of the self-assembly of 3 in buffered solution was significantly transformed.

Exploring the reversible host-guest chemistry of a crystalline octanuclear Ag(i) metallosupramolecular macrocycle formed from a simple pyrazinylpyridine ligand.

Here we report the synthesis of two new 2-(2'-pyrazinyl)pyridine ligands, and explore their coordination chemistry with Cu(ii) and Ag(i) ions, leading to the discovery of metallosupramolecular architectures of surprising complexity. Differing only in the substitution pattern of a nitrophenyl substituent attached to the 4-pyridyl position, ligands L1 and L2 both form sulfate-bridged dinuclear complexes on reaction with copper sulfate, without coordination of the nitrogen atom at the pyrazine 4-position. However, on reaction with Ag(i), both ligands adopt bridging coordination modes which lead to dramatically different outcomes. Ligand L2 reacts with AgCF3SO3 to give a densely packed coordination polymer 3 of unusually low symmetry (Z' = 7), while the structural isomer L1 instead gives an octanuclear macrocycle 4 in the crystalline state. Macrocycle 4, containing crystallographically-defined solvent molecules within its central cavity as well as in the interstitial spaces, readily undergoes solvent exchange in a single-crystal-to-single-crystal transformation. This allows a direct comparison of guest solvent affinity from single component and mixed-component exchange solutions using a combination of X-ray diffraction, NMR and TGA techniques, revealing the fully reversible uptake and exchange preferences of this material.

Coordination chemistry of flexible benzene-1,3,5-tricarboxamide derived carboxylates; notable structural resilience and vaguely familiar packing motifs.

Flexible benzene-1,3,5-tricarboxamides (BTAs), organic species well-known for their tendencies to form functional soft-materials by virtue of their complementary hydrogen bonding, are explored as structurally reinforcing supramolecular building blocks in porous coordination polymers. We report the synthesis and characterisation of two related, carboxylate-terminated BTA derivatives, and the structure and functionality of their polymeric Cd(ii) complexes. The polycarboxylate ligand benzene-1,3,5-tricarboxamide tris(phenylacetic acid) H3L1 was prepared, and the analogous trimethyl benzene-1,3,5-tricarboxamide tris acetate Me3L2 was prepared and its single crystal structure elucidated. On reaction with cadmium nitrate in a DMF/H2O mixture, each BTA compound yielded coordination polymer species with columnar packing motifs comparable to the familiar BTA triple helix seen in purely organic systems. In the case of Me3L2, this transformation was achieved through a convenient in situ ester hydrolysis. Complex 1 is a 2-dimensional layered material containing tubular intralayer pores, in which amide-amide hydrogen bonding is a notable structural feature. In contrast, the structure of 2 contains no amide-amide hydrogen bonding, and instead a columnar arrangement of ligand species is linked by trinuclear Cd(ii) cluster nodes into a densely packed three-dimensional framework. The crystal structures revealed both materials exhibited significant solvent-accessible volume, and this was probed with thermal analysis and CO2 and N2 adsorption experiments; complex 2 showed negligible gas uptake, while compound 1 possesses an unusually high CO2 capacity for a two-dimensional material with intralayer porosity and surprising structural resilience to guest exchange, evacuation and exposure to air.

A resilient and luminescent stimuli-responsive hydrogel from a heterotopic 1,8-naphthalimide-derived ligand.

A heterotopic naphthalimide ligand N-(4-picolyl)-4-(4'-carboxyphenoxy)-1,8-naphthalimide HL is utilised for the formation of self-assembled soft materials. In the presence of K+ ions, L- forms a robust photoluminescent hydrogel 1 which is reversible under thermal, mechanical or chemical stimuli.

Nucleophilic reactivity of a copper(II)-superoxide complex.

Metal-bound superoxide intermediates are often implicated as electrophilic oxidants in dioxygen-activating metalloenzymes. In the nonheme iron α-ketoglutarate dependent oxygenases and pterin-dependent hydroxylases, however, Fe(III)-superoxide intermediates are postulated to react by nucleophilic attack on electrophilic carbon atoms. By reacting a Cu(II)-superoxide complex (1) with acyl chloride substrates, we have found that a metal-superoxide complex can be a very reactive nucleophile. Furthermore, 1 was found to be an efficient nucleophilic deformylating reagent, capable of Baeyer-Villiger oxidation of a number of aldehyde substrates. The observed nucleophilic chemistry represents a new domain for metal-superoxide reactivity. Our observations provide support for the postulated role of metal-superoxide intermediates in nonheme iron α-ketoglutarate dependent and pterin-dependent enzymes.