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Department of Chemistry

 

Our research interests focus on understanding the structure, synthesis and reactivity of mixed-metal organometallic compounds and nanocatalysts.

 

Organometallics for synthesis

We are interested in the activities of molecular organometallic reagents and have used homo- and heterometallic reagents including Li-Al and Li-Zn systems to fabricate hydridic clusters and to function as chemoselective bases. We work on this with teams in Tokyo, Rennes and Bristol. Recent major advances include:

1) the first demonstration that directed benzylic lithiation can be used to generate tertiary carbanions (below right) and,

2) the combination of CuCN with organolithium reagents to give bimetallic bases such as (TMP)2Cu(CN)Li2.THF (TMP = 2,2,6,6-tetramethylpiperidide; below left) that have applications in directed cupration and C–C bond formation.

 

For the first tertiary carbanion syntheses by directed metalation and a comparison of anion structures in the solid state and in solution see Chem. Eur. J., 2011, 17, 8078 and 2012, 18, 11036.

See Chem. Sci., 2017, 8, 4904 for recent advances in lithium amidocuprate structural and mechanistic chemistry and Dalton Trans., 2016, 45, 6094 for the applications of lithium cuprates in the elaboration of halopyridines.

We have established the existence of adducts that may help to explain how cuprates of the type (amide)2Cu(Cl)Li2.L (below left; amide = TMP, L = Et2O) can exclude LiX to give highly active (amide)2CuLi.L. Steric effects associated with the amide ligand are thought to be crucial to controlling structure and are suggested if DMP (= cis-2,6-dimethylpiperidide) is used in place of TMP (below right).

See Chem. Eur. J., 2014, 20, 3908 for lithium amidocuprate adducts in directed aromatic cupration and for a recent invited review see Dalton Trans., 2014, 43, 14181.

 

Heterogeneous nanocatalysis

The ability to access stable and compositionally and dimensionally controllable metallic nanoparticles promises applications in catalysis. We prepare metal-based nanoparticles and use them to achieve controllably functional hybrid materials by encapsulation e.g. in mesostructured films. Recently, we have worked with members of Nagoya University to fabricate chitin-supported Ru-based catalysts active in the selective hydrogenation of arenes to cyclohexanes in water (Catal. Sci. Technol., 2016, 6, 5801) and have also moved into the field of photocatalysis, using semiconductor-based nanocomposites (e.g. of SnO2-PbS) in the detoxification of water (Nanoscale, 2016, 8, 2727) and Cu-Au nanocomposites the first late-stage N-alkylation of pharmaceutically relevant amines with alcohols at ambient temperature (Sci. Rep., 2018, 8, 6931).

In other work, we have collaborated with researchers at the Technical University of Eindhoven applications of the resulting microreactors have been developed in the areas of selective hydrogenation, nanotube growth, and fine chemicals synthesis. For our work on capillary microreactors wall-coated with mesoporous catalyst supports and the immobilization of Cu catalysts for microfluidic Ullmann SNAr-type C-O coupling reactions see Chem. Eur. J., 2012, 18, 1800.

 

 

We are interested in fundamental aspects of nanoparticle synthesis and structure. Recently, we have successfully fabricated oxidatively stable Cu-based nanocatalysts as evidenced by XRD and XPS (below). By introducing Zn we have also achieved CuZn nanoparticles with differing intermetallic ratios and predicted upper d-band energies for Cu. Cu-based catalysts were successfully deployed in multicomponent 1,3-dipolar cycloaddition reactions, yielding 1,2,3-triazoles using unprecedentedly low catalyst loadings and under facile conditions.

See Nanoscale, 2013, 5, 342 for the development of new routes towards Cu-based nanosystems and the application of Cu-based catalysts to triazole formation. Our interest in Cu-based nanoparticles, including how they progressively oxidize, has been reflected in work on the passivation of metal nanoparticles towards degenerative processes.  As part of a study into the preparation of magnetic nanoparticles for applications in catalysis we have fully characterized monodisperse magnetic seeds encapsulated by Fe3O4 and established the presence of a sub-surface carbon layer:

The presence of this layer may have implications for core stability (both Co and Fe have been shown to be oxidatively stable for months) and the ability to favour the synthesis of core-shell heterostructures. This is the subject of ongoing work that seeks to establish the generality of this encapsulation procedure.

See Nanoscale, 2013, 5, 5765 and Part. Part. Syst. Charact., 2018, in press for the synthesis and detailed characterization of M-Fe3O4 nanoparticles (M = Co, Fe), including using EFTEM and EELS point scan data (below) that proves the existence of intraparticle carbon. For the extension of detailed characterization of multimetallic core-shell architectures to the Fe3O4-encapsulation of more complex seeds see Nano Lett., 2015, 15, 2716 and Part. Part. Syst. Charact., 2016, 33, 749.

 

New composite materials

Our most recent work has focused on novel ways of immobilizing nanocatalysts using a new breed of porous support: monolithic metal-organic frameworks (monoMOFs).

With co-workers at Cambridge, we have been able to present a new type of composite material involving the in situ immobilization of photoactive nanoparticles within a monoMOF. For proof-of-concept we immobilized SnO2 using the zeolitic imidazolate framework ZIF-8. The composite SnO2@monoZIF-8 exploits the mechanical properties, structural resilience and density of a monoMOF, but leverages the photocatalytic action of the nanoparticles. In tests, this composite displayed outstanding photocatalytic properties, representing a critical advance in the field of treating toxic effluents. Full retention of catalytic activity was observed over multiple catalytic cycles. See Adv. Funct. Mater., 2018, 1705588.

Publications

Single-Source Bismuth (Transition Metal) Polyoxovanadate Precursors for the Scalable Synthesis of Doped BiVO4 Photoanodes
H Lu, V Andrei, KJ Jenkinson, A Regoutz, N Li, CE Creissen, AEH Wheatley, H Hao, E Reisner, DS Wright, SD Pike
– Advanced materials (Deerfield Beach, Fla.)
(2018)
30,
e1804033
Photocatalytic N-Methylation of Amines over Pd/TiO2 for the Functionalization of Heterocycles and Pharmaceutical Intermediates
LM Wang, K Jenkinson, AEH Wheatley, K Kuwata, S Saito, H Naka
– ACS Sustainable Chemistry and Engineering
(2018)
6,
15419
Preparation of bifunctional Au-Pd/TiO 2 catalysts and research on methanol liquid phase one-step oxidation to methyl formate
D Shi, J Liu, R Sun, S Ji, SM Rogers, BM Connolly, N Dimitratos, AEH Wheatley
– Catalysis Today
(2018)
316,
206
Advances in the Synthesis and Long-Term Protection of Zero-Valent Iron Nanoparticles
JP Mehta, BR Knappett, G Divitini, E Ringe, PA Midgley, D Fairen-Jimenez, AEH Wheatley
– Particle & Particle Systems Characterization
(2018)
35,
1800120
From synthesis to applications: Metal–organic frameworks for an environmentally sustainable future
BM Connolly, JP Mehta, PZ Moghadam, AEH Wheatley, D Fairen-Jimenez
– Current Opinion in Green and Sustainable Chemistry
(2018)
12,
47
N-Alkylation of functionalized amines with alcohols using a copper-gold mixed photocatalytic system (vol 8 , 6931, 2018)
L-M Wang, Y Morioka, K Jenkinson, AEH Wheatley, S Saito, H Naka
– Scientific Reports
(2018)
8,
9557
N-Alkylation of functionalized amines with alcohols using a copper-gold mixed photocatalytic system
L-M Wang, Y Morioka, K Jenkinson, AEH Wheatley, S Saito, H Naka
– Sci Rep
(2018)
8,
6931
Sol-Gel Synthesis of Robust Metal-Organic Frameworks for Nanoparticle Encapsulation
JP Mehta, T Tian, Z Zeng, G Divitini, BM Connolly, PA Midgley, JC Tan, D Fairen-Jimenez, AEH Wheatley
– Advanced Functional Materials
(2018)
28,
1705588
Harnessing Surface-Functionalized Metal–Organic Frameworks for Selective Tumor Cell Capture
X Qi, Z Chang, D Zhang, KJ Binder, S Shen, YYS Huang, Y Bai, AEH Wheatley, H Liu
– Chemistry of Materials
(2017)
29,
8052
Aluminium carboxylates as precursors for the synthesis of aluminium-oxo-cages
T-L Precht, A Peel, D Wright, A Wheatley
– ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY
(2017)
253,
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Research Interest Groups

Telephone number

01223 763966

Email address

aehw2@cam.ac.uk