Research Guides

 

Research

Research Interests     Updated 03/09/2018

The group's research interests focus on the electronic structure of inorganic systems. We apply a variety of computational methods to a range of problems drawn from both transition-metal and main-group chemistry. The vast majority of our work involves close collaboration with experimental groups involved in the study of structure, magnetochemistry, electrochemistry and reactivity.

The electronic structure of cluster compounds

Metal cluster compounds present a significant challenge to models of structure and bonding - the work of Wade and Mingos in the 1970's, for example, revolutionised our understanding of electron-deficient boranes and their transition metal analogues. More recently, endohedrally encapsulated clusters, where a transition metal sits inside a cluster cage, have provoked interest, in part because they represent the smallest models for transition metal impurities in bulk semiconductors like silicon or germanium. In many cases the metal and cage are essentially independent units: 60-electron [Ni@Pb12]2-, for example, can be thought of as a closed-shell d10 metal inside a 'closo' [Pb12]2- icosahedron (4n + 2 = 50 valence electrons). In work with Prof José Goicoechea's group, we have explored a relatively new class of cluster where the vertices of the cluster are 3-connected rather than 4- or 5-connected, as is typical of deltahedral structures. 3-connected vertices are generally associated with electron precise (5n) electron counts, but if 5n electrons are assigned to the cage in e.g. [Ru@Ge12]3-, the metal is left in an unreasonably high oxidation state. The key to understanding these systems is to note that pairs of electrons can play a dual role, satisfying the valence requirements of the metal and the cluster simultaneously. This 'jigsaw' model emphasises the importance of interpenetration of the electron density at the metal and on the cluster. In cases where the endohedral transition metal ion lies in the middle of d-block, the ground-state wavefunction is typically strongly multi-configurational. In such cases, the CASSCF methodology offers an alternative perspective to DFT.

                          

Synthesis and Characterization of [Ru@Ge12]​3-​: An Endohedral 3-​Connected Cluster, G. Espinoza-Quintero, J. C. A. Duckworth, W. K. Myers, J. E. McGrady and J. M. Goicoechea, J. Am. Chem. Soc., 2014, 136, 1210.

 

The interactions between transition metal ions themselves are notoriously difficult to model theoretically, and the ground-state wavefunctions are typically poorly described by a single-determinant wavefunction. This problem is particularly pressing in the first-row transition metals, where the absence of a radial node in the 3d orbital means that electron-electron repulsions are large. We use CAS/GASSCF and CASPT2 methodologies to explore the evolution of metal-metal bonding in these systems, both as a function of composition and of oxidation state.

 

                                                 

Redox‐Dependent Metal−Metal Bonding in Trinuclear Metal Chains: Probing the Transition from Covalent Bonding to Exchange Coupling, M. Obies, N. R. Perkins, V. Arcisauskaite, G. A. Heath, A. J. Edwards and J. E. McGrady, Chem. Eur. J., 2018, 24, 5309.  HOT PAPER

Metal-metal Interactions in Trinuclear Chains, Chemistry Views, 2018.

In collaboration with Prof. Raphael Raptis (Florida International University), we have also investigated the nature of the mixed valency (localised or delocalised) in reduced ferric/ferrous clusters.

A Redox-Induced Spin-State Cascade in a Mixed-Valent Fe33-O) Triangle, E. Govor, Evgen, K. Al-Ameed, I. Chakraborty, C. S. Coste, O. Govor, Y. Sanakis, J. E. McGrady and R. G. Raptis, Angew. Chem., 2017, 56, 582-586.

Experimental and Theoretical Mossbauer Study of an Extended Family of Fe8(μ-O)4(μ-4-R-px)12X4 Clusters. E. M. Zueva, W. M. C. Sameera, D. M. Pinero, I Chakraborty, E. Devlin, P. Baran, K. Lubruskova, Y. Sanakis, J. E. McGrady and R. G. Raptis, Inorg. Chem., 2011, 50, 1021.

 

Electronic structure of low-dimensional metal oxides

Oxide lattices typically stable the highest accessible oxidation states of transition metal ions, but the reduction of perovskite and Ruddlesden-Popper phases by sources of hydride, developed by Hayward and co-workers, has provided access to a wide range of new compounds with the transition metal in unprecedented low oxidation states. This includes cases where the hydride replaces the oxide in the lattice and other where the hydride removes layers of oxide ions as H2O. These compounds are kinetically but not thermodynamically stable, but nevertheless they offer the opportunity to study transition metal ions in previously unprecedented electronic environments.

                                               

The role of π-blocking hydride ligands in a pressure-induced insulator-to-metal phase transition in SrVO2H, T. Yamamoto, D. Zeng, T. Kawakami, V. Arcisauskaite, K. Yata, M. Amano Patino, N. Izumo, J. E. McGrady, M. A. Hayward and H. Kageyama, Nature Comm.2017, 8, 1217.

LaSr3NiRuO4H4: A 4d Transition-Metal Oxide-Hydride Containing Metal Hydride Sheets, L. Jin, M. Lane, D. Zeng, F.K.K. Kirschner, F. Lang, P. Manual, S. J. Blundell, J. E. McGrady and M. A. Hayward, Angewandte Chemie2018, 57, 5025.

 

Coherent transport through metal-metal bonded molecular wires

Another main interest of the group is to understand the link between electronic structure and electron transport properties of extended metal atom chain (EMAC) complexes, where hlical array of oligo-α-pyridyl ligands is used to support a chain of metal centres. These systems have been the subject of a protracted debate in the inorganic chemistry community due to their polymorphism – they exist is symmetric and unsymmetic forms. Our current objective is to relate the fundamental electronic structure of these EMAC complexes to their conductance as measured, for example, by STM. Ultimately, an understanding of these phenomena will be essential to the development of new computer architectures based on molecular-scale components.

 

 

In search of structure-​function relationships in transition-​metal based rectifiers, T. Weng, D. DeBrincat, V. Arcisauskaite and J. E. McGrady, Inorganic Chemistry Frontiers2014, 1, 468.

Low-symmetry distortions in extended metal atom chains: origins and consequences for electron transport, V. P. Georgiev, P. J. Mohan, D. DeBrincat and J. E. McGrady, Coord. Chem. Rev., 2013, 290.

Attenuation of conductance in cobalt extended metal atom chains, V. P. Georgiev. W.M.C. Sameera and J. E. McGrady, J. Phys. Chem. C, 2012, 20163.

Influence of Low-Symmetry Distortions on Electron Transport through Metal Atom Chains: When Is a Molecular Wire Really "Broken"?, V. P. Georgiev and J. E. McGrady, J. Am. Chem. Soc., 2011, 132, 12590.

 

Redox-active ligands

                                                                               

We also have a strong interest in exploring the ways in which electrons are transferred between transition metals (and metal clusters) and redox-active coordinated ligands. Recent highlights include the study of redox-noninnocent complexes of bipyridyl (with Dr Jose Goicoechea, Oxford and Prof Sreebrata Goswami, IACS, Kolkata) . Our studies have illustrated that the open-shell character plays a defining role in controlling the direction of electron transfer processes.

A Homologous Series of First-Row Transition-Metal Complexes of 2,2 '-Bipyridine and their Ligand Radical Derivatives: Trends in Structure, Magnetism, and Bonding, M. Irwin, L.R. Doyle, T. Kramer, R. Herchel, J.E. McGrady and J.M. Goicoechea, Inorg. Chem., 2012, 51, 12301.

On the Mechanism of Water Oxidation by a Bimetallic Manganese Catalyst: A Density Functional Study. W. M. C. Sameera, C. J. McKenzie and J. E. McGrady, Dalton Trans., 2011, 40, 3859.

 

Main group chemistry

Not all the work in the group is related to transition metal chemistry. In collaboration with Dr. Chris Russell at Bristol University, we have been exploring mechanism of bond activation by main group compounds (phosphabenzenes).

Hydrogen Activation by an Aromatic Triphosphabenzene, L. E. Longobardi, C. A. Russell, M. Green, N. S. Townsend, K. Wang, A. J. Holmes, S. B. Duckett, J. E. McGrady and D. W. Stephan, J. Am. Chem. Soc., 2014, 136, 13453.

 

Selected Publications

Low-valent oxides

1. The role of π-blocking hydride ligands in a pressure-induced insulator-to-metal phase transition in SrVO2H

Yamamoto, Takafumi; Zeng, Dihao; Kawakami, Takateru; Arcisauskaite, Vaida; Yata, Kanami; Patino, Midori Amano; Izumo, Nana; McGrady, John E.; Kageyama, Hiroshi; Hayward, Michael A., Nature Communications (2017), 8(1), 1-7

2. LaSr3NiRuO4H4: A 4d Transition-Metal Oxide-Hydride Containing Metal Hydride Sheets

Jin, Lun; Lane, Michael; Zeng, Dihao; Kirschner, Franziska K. K.; Lang, Franz; Manuel, Pascal; Blundell, Stephen J.; McGrady, John E.; Hayward, Michael A., Angewandte Chemie, International Edition (2018), 57(18), 5025-5028.

3. SrFe0.5Ru0.5O2: Square-Planar Ru2+ in an Extended Oxide

Denis Romero, Fabio; Burr, Steven J.; McGrady, John E.; Gianolio, Diego; Cibin, Giannantonio; Hayward, Michael A., Journal of the American Chemical Society (2013), 135(5), 1838-1844.

Metal-metal bonds

4. Introduction and general survey of metal-metal bonds

 McGrady, John E., Molecular Metal-Metal Bonds (2015), 1-22.

5. Redox-Dependent Metal-Metal Bonding in Trinuclear Metal Chains: Probing the Transition from Covalent Bonding to Exchange Coupling

Obies, Mohammed; Perkins, Nicholas R.; Arcisauskaite, Vaida; Heath, Graham A.; Edwards, Alison J.; McGrady, John E., Chemistry - A European Journal (2018), 24(20), 5309-5318.

6. A multiconfigurational approach to the electronic structure of trichromium extended metal atom chains

Spivak, M.; Arcisauskaite, V.; Lopez, X.; McGrady, J. E.; de Graaf, C., Dalton Transactions (2017), 46(19), 6202-6211.

7. A Redox-Induced Spin-State Cascade in a Mixed-Valent Fe33-O) Triangle

Govor, Evgen V.; Al-Ameed, Karrar; Chakraborty, Indranil; Coste, Carla S.; Govor, Olena; Sanakis, Yiannis; McGrady, John E.; Raptis, Raphael G., Angewandte Chemie, International Edition (2017), 56(2), 582-586

Endohedral clusters

8. Structural trends in ten-vertex endohedral clusters, M@E10 and the synthesis of a new member of the family, [FeSn10]3-

Kraemer, Tobias; Duckworth, Jack C. A.; Ingram, Matthew D.; Zhou, Binbin; McGrady, John E.; Goicoechea, Jose M., Dalton Transactions (2013), 42(34), 12120-12129.

9. Biradical character in the ground state of [Mn@Si12]+: a DFT and CASPT2 study

Arcisauskaite, Vaida; Fijan, Domagoj; Spivak, Mariano; Graaf, Coen de; McGrady, John E., Physical Chemistry Chemical Physics (2016), 18(34), 24006-24014

10. The structural landscape in 14-vertex clusters of silicon, M@Si14: when two bonding paradigms collide

Jin, Xiao; Arcisauskaite, Vaida; McGrady, John E., Dalton Transactions (2017), 46(35), 11636-11644.

11. On the structural landscape in endohedral silicon and germanium clusters, M@Si12 and M@Ge12

Goicoechea, Jose M.; McGrady, John E., Dalton Transactions (2015), 44(15), 6755-6766.

12. Synthesis and Characterization of [Ru@Ge12]3-: An Endohedral 3-Connected Cluster

Espinoza-Quintero, Gabriela; Duckworth, Jack C. A.; Myers, William K.; McGrady, John E.; Goicoechea, Jose M., Journal of the American Chemical Society (2014), 136(4), 1210-1213

Electron transport

13. Can heterometallic 1-dimensional chains support current rectification?

DeBrincat, Daniel; Keers, Oliver; McGrady, John E., Chemical Communications (2013), 49(80), 9116-9118.

14. Low-symmetry distortions in Extended Metal Atom Chains (EMACs): Origins and consequences for electron transport

Georgiev, Vihar P.; Mohan, P. J.; DeBrincat, Daniel; McGrady, John E., Coordination Chemistry Reviews (2013), 257(1), 290-298.

Redox non-innocent ligands

15. Redox Noninnocence in Coordinated 2-(Arylazo)pyridines: Steric Control of Ligand-Based Redox Processes in Cobalt Complexes Ghosh, Pradip; Samanta, Subhas; Roy, Suman K.; Joy, Sucheta; Kramer, Tobias; McGrady, John E.; Goswami, Sreebrata, Inorganic Chemistry (2013), 52(24), 14040-14049.

16. A Homologous Series of First-Row Transition-Metal Complexes of 2,2'-Bipyridine and their Ligand Radical Derivatives: Trends in Structure, Magnetism, and Bonding

Irwin, Mark; Doyle, Laurence R.; Kramer, Tobias; Herchel, Radovan; McGrady, John E.; Goicoechea, Jose M., Inorganic Chemistry (2012), 51(22), 12301-12312.

Reaction mechanisms

17. Oxidative Addition, Transmetalation, and Reductive Elimination at a 2,2'-Bipyridyl-Ligated Gold Center

Harper, Matthew J.; Arthur, Christopher J.; Crosby, John; Emmett, Edward J.; Falconer, Rosalyn L.; Fensham-Smith, Andrew J.; Gates, Paul J.; Leman, Thomas; McGrady, John E.; Bower, John F., Journal of the American Chemical Society (2018), 140(12), 4440-4445.

18. How formaldehyde inhibits hydrogen evolution by [FeFe]-hydrogenases: Determination by 13C ENDOR of direct Fe-C coordination and order of electron and proton transfers

Bachmeier, Andreas; Esselborn, Julian; Hexter, Suzannah V.; Kramer, Tobias; Klein, Kathrin; Happe, Thomas; McGrady, John E.; Myers, William K.; Armstrong, Fraser A., Journal of the American Chemical Society (2015), 137(16), 5381-5389

19. Hydrogen Activation by an Aromatic Triphosphabenzene

Longobardi, Lauren E.; Russell, Christopher A.; Green, Michael; Townsend, Nell S.; Wang, Kun; Holmes, Arthur J.; Duckett, Simon B.; McGrady, John E.; Stephan, Douglas W., Journal of the American Chemical Society (2014), 136(38), 13453-13457

 

Professor John E. McGrady

Inorganic Chemistry

john.mcgrady@chem.ox.ac.uk

Telephone: 44 (0) 1865 275 406

Research Group Website

http://research.chem.ox.ac.uk/john-mcgrady.aspx