Craig J. Richmond

Integrated 3D-printed reactionware for chemical synthesis and analysis

Three-dimensional (3D) printing has the potential to transform science and technology by creating bespoke, low-cost appliances that previously required dedicated facilities to make. An attractive, but unexplored, application is to use a 3D printer to initiate chemical reactions by printing the reagents directly into a 3D reactionware matrix, and so put reactionware design, construction and operation under digital control. Here, using a low-cost 3D printer and open-source design software we produced reactionware for organic and inorganic synthesis, which included printed-in catalysts and other architectures with printed-in components for electrochemical and spectroscopic analysis. This enabled reactions to be monitored in situ so that different reactionware architectures could be screened for their efficacy for a given process, with a digital feedback mechanism for device optimization. Furthermore, solely by modifying reactionware architecture, reaction outcomes can be altered. Taken together, this approach constitutes a relatively cheap, automated and reconfigurable chemical discovery platform that makes techniques from chemical engineering accessible to typical synthetic laboratories.

Assembly of a gigantic polyoxometalate cluster {W200Co8O660} in a networked reactor system.

A giant leap: A networked reactor system was used for the first time for the discovery and synthesis of new polyoxometalates, including the gigantic title system. The system comprises of three reactors connected in a triangular array with a central triply connected reactor. This system was used to screen multiple one-pot reactions and reaction variables for the automated syntheses of polyoxometalates.

Exploring the mobility of nanoscale polyoxometalates using gel electrophoresis

Polyoxometalate clusters encompass a vast library of molecular metal-oxo anions with a large range of mass, size, and charge and are generally formed under one-pot conditions, where many species may exist in solution at any given time. Herein we demonstrate that conventional gel electrophoresis can be used to separate metal oxide based nanomaterials from mixtures, and as a result identify cluster types as a function of their surface charge density. In particular we demonstrate that the nanoscale clusters, contrary to current understanding, have mobility that is a function of the surface charge density at high concentrations. This means that when considering the structural diversity of metal oxide nanomaterials, the variation of charge, size, shape or other structural properties causes a difference in mobility that can be used to both characterise and separate the nanoscale oxides in solution.

Water oxidation catalysis with ligand substituted Ru–bpp type complexes

A series of symmetric and non-symmetric dinuclear Ru complexes of general formula {[Ru(R2-trpy)(H2O)][Ru(R3-trpy)(H2O)](μ-R1-bpp)}3+ where trpy is 2,2′:6′,2′′-terpyridine, bpp− is 3,5-bis(2-pyridyl)-pyrazolate and R1, R2 and R3 are electron donating (ED) and electron withdrawing (EW) groups such as Me, MeO, NH2 and NO2 have been prepared using microwave assisted techniques. These complexes have been thoroughly characterized by means of analytical (elemental analysis), spectroscopic (UV-vis, NMR) and electrochemical (CV, SQWV, CPE) techniques. The single crystal X-ray structures for one acetate- and one chloro-bridged precursor have also been solved. Kinetic analysis monitored by UV-vis spectroscopy reveals the electronic effects exerted by the ED and EW groups on the substitution kinetics and stoichiometric water oxidation reaction. The catalytic water oxidation activity is evaluated by means of chemically (CeIV), electrochemically, and photochemically induced processes. It is found that, in general, ED groups do not strongly affect the catalytic rates whereas EW groups drastically reduce catalytic rates. Finally, DFT calculations provide a general and experimentally consistent view of the different water oxidation pathways that can operate in the water oxidation reactions catalyzed by these complexes.

A new C–C bond forming annulation reaction leading to pH switchable heterocycles

A C-C bond forming reaction resulting from the alpha-addition of carbon based nucleophiles to N-bromoethyl phenanthridinium leads to the formation of 2,3-dihydro-12H-pyrrolo[1,2-f]phenanthridine-based derivatives which undergo reversible ring-opening/closing under pH control.

Fine Tuning Reactivity: Synthesis and Isolation of 1,2,3,12b-Tetrahydroimidazo[1,2-f]phenanthridines

A facile route for the synthesis and isolation of 1,2,3,12b-tetrahydroimidazo[1,2-f]phenanthridines (TIPs) has been developed. The heterocycle is a reactive intermediate in the three-step cascade synthesis of 2,3-dihydro-1H-imidazo[1,2-f]phenanthridinium cations (DIPs), a biologically active DNA intercalating framework; however, the intermediate has previously only been characterized in situ. Derivatization of the structure at the imidazo-N position controls the reactivity of the intermediate with respect to electronic potential and pK(a) allowing isolation of a selection of TIP structures. Correlations between these parameters and reaction outcome have been made, and other influences such as steric and solvent effects have also been investigated.

Incorporation of a ruthenium–bis(pyridine)pyrazolate (Ru–bpp) water oxidation catalyst in a hexametallic macrocycle

New terpyridine-functionalised analogues of the in,in-[{RuII(trpy)}2(μ-bpp)(H2O)2]3+ water oxidation catalyst (bpp = bis-(2-pyridyl)pyrazolate) have been synthesised and used to create a hexametallic {Fe2Ru4} macrocycle. The macrocyclic WOC precursor contains two catalyst units linked by two {Fe(R-trpy)2} bridges and shows similar catalytic activity for water oxygen when compared to the non-cyclic catalyst precursors. The synthesised complexes were fully characterised by standard voltammetric and spectroscopic techniques (CV, DPV, NMR, MS, UV and IR) and the assessment of their performance as WOCs was performed using a CeIV chemical oxidant in aqueous triflic acid.