Professional Education

  • Doctor of Philosophy, University of Oxford (2021)
  • Master of Science, University of Saint Andrews (2016)
  • MChem, University of St Andrews (2016)
  • DPhil, University of Oxford (2020)

Stanford Advisors

All Publications

  • The impact of optical excitation on the binding in complexes of the cationic gold dimer: Au<sub>2</sub><SUP>+</SUP> N<sub>2</sub> and Au<sub>2</sub><SUP>+</SUP> N<sub>2</sub>O NATURAL SCIENCES Foerstel, M., Nahvi, N., Pollow, K., Studemund, T., Green, A. E., Fielicke, A., Mackenzie, S. R., Dopfer, O. 2023; 3 (1)
  • An Infrared Study of Gas-Phase Metal Nitrosyl Ion-Molecule Complexes. The journal of physical chemistry. A Meizyte, G., Pearcy, P. A., Watson, P. D., Brewer, E. I., Green, A. E., Doll, M., Duda, O. A., Mackenzie, S. R. 2022


    We present a combined experimental and quantum chemical study of gas-phase group 9 metal nitrosyl complexes, M(NO)n+ (M = Co, Rh, Ir). Experimental infrared photodissociation spectra of mass-selected ion-molecule complexes are presented in the region 1600 cm-1 to 2000 cm-1 which includes the NO stretch. These are interpreted by comparison with the simulated spectra of energetically low-lying structures calculated using density functional theory. A mix of linear and nonlinear ligand binding is observed, often within the same complex, and clear evidence of coordination shell closing is observed at n = 4 for Co(NO)n+ and Ir(NO)n+. Calculations of Rh(NO)n+ complexes suggest additional low-lying five-coordinate structures. In all cases, once a second coordination shell is occupied, new spectral features appear which are assigned to (NO)2 dimer moieties. Further evidence of such motifs comes from differences in the spectra recorded in the dissociation channels corresponding to single and double ligand loss.

    View details for DOI 10.1021/acs.jpca.2c07228

    View details for PubMedID 36480929

  • An infrared study of CO2 activation by holmium ions, Ho+ and HoO. Physical chemistry chemical physics : PCCP Brewer, E. I., Green, A. E., Gentleman, A. S., Beardsmore, P. W., Pearcy, P. A., Meizyte, G., Pickering, J., Mackenzie, S. R. 2022


    We report a combined experimental and computational study of carbon dioxide activation at gas-phase Ho+ and HoO+ centres. Infrared action spectra of Ho(CO2)n+ and [HoO(CO2)n]+ ion-molecule complexes have been recorded in the spectral region 1700-2400 cm-1 and assigned by comparison with simulated spectra of energetically low-lying structures determined by density functional theory. Little by way of activation is observed in Ho(CO2)n+ complexes with CO2 binding end-on to the Ho+ ion. By contrast, all [HoO(CO2)n]+ complexes n ≥ 3 show unambiguous evidence for formation of a carbonate radical anion moiety, . The signature of this structure, a new vibrational band observed around 1840 cm-1 for n = 3, continues to red-shift monotonically with each successive CO2 ligand binding with net charge transfer from the ligand rather than the metal centre.

    View details for DOI 10.1039/d2cp02862j

    View details for PubMedID 36106954

  • Spectroscopy and Infrared Photofragmentation Dynamics of Mixed Ligand Ion-Molecule Complexes: Au(CO)(x)(N2O)(y)(+) JOURNAL OF PHYSICAL CHEMISTRY A Green, A. E., Brown, R. H., Meizyte, G., Mackenzie, S. R. 2021; 125 (33): 7266-7277


    We report a combined experimental and computational study of the structure and fragmentation dynamics of mixed ligand gas-phase ion-molecule complexes. Specifically, we have studied the infrared spectroscopy and vibrationally induced photofragmentation dynamics of mass-selected Au(CO)x(N2O)y+ complexes. The structures can be understood on the basis of local CO and N2O chromophores in different solvation shells with CO found preferentially in the core. Rich fragmentation dynamics are observed as a function of complex composition and the vibrational mode excited. The dynamics are characterized in terms of branching ratios for different ligand loss channels in light of calculated internal energy distributions. Intramolecular vibrational redistribution appears to be rapid, and dissociation is observed into all energetically accessible channels with little or no evidence for preferential breaking of the weakest intermolecular interactions.

    View details for DOI 10.1021/acs.jpca.1c05800

    View details for Web of Science ID 000692015300015

    View details for PubMedID 34433267

  • Atomic Cluster Au-10(+) Is a Strong Broadband Midinfrared Chromophore PHYSICAL REVIEW LETTERS Green, A. E., Gentleman, A. S., Schoellkopf, W., Fielicke, A., Mackenzie, S. R. 2021; 127 (3): 033002


    We report an intense broadband midinfrared absorption band in the Au_{10}^{+} cluster in a region in which only molecular vibrations would normally be expected. Observed in the infrared multiple photon dissociation spectra of Au_{10}Ar^{+}, Au_{10}(N_{2}O)^{+}, and Au_{10}(OCS)^{+}, the smooth feature stretches 700-3400  cm^{-1} (λ=14-2.9  μm). Calculations confirm unusually low-energy allowed electronic excitations consistent with the observed spectra. In Au_{10}(OCS)^{+}, IR absorption throughout the band drives OCS decomposition resulting in CO loss, providing an alternative method of bond activation or breaking.

    View details for DOI 10.1103/PhysRevLett.127.033002

    View details for Web of Science ID 000674614700006

    View details for PubMedID 34328766

  • Infrared action spectroscopy of nitrous oxide on cationic gold and cobalt clusters PHYSICAL CHEMISTRY CHEMICAL PHYSICS Cunningham, E. M., Green, A. E., Meizyte, G., Gentleman, A. S., Beardsmore, P. W., Schaller, S., Pollow, K. M., Saroukh, K., Forstel, M., Dopfer, O., Schollkopf, W., Fielicke, A., Mackenzie, S. R. 2021; 23 (1): 329-338


    Understanding the catalytic decomposition of nitrous oxide on finely divided transition metals is an important environmental issue. In this study, we present the results of a combined infrared action spectroscopy and quantum chemical investigation of molecular N2O binding to isolated Aun+ (n ≤ 7) and Con+ (n ≤ 5) clusters. Infrared multiple-photon dissociation spectra have been recorded in the regions of both the N[double bond, length as m-dash]O (1000-1400 cm-1) and N[double bond, length as m-dash]N (2100-2450 cm-1) stretching modes of nitrous oxide. In the case of Aun+ clusters only the ground electronic state plays a role, while the involvement of energetically low-lying excited states in binding to the Con+ clusters cannot be ruled out. There is a clear preference for N-binding to clusters of both metals but some O-bound isomers are observed in the case of smaller Con(N2O)+ clusters.

    View details for DOI 10.1039/d0cp05195k

    View details for Web of Science ID 000625340900001

    View details for PubMedID 33346764

  • Free electron laser infrared action spectroscopy of nitrous oxide binding to platinum clusters, Pt-n(N2O)(+) PHYSICAL CHEMISTRY CHEMICAL PHYSICS Meizyte, G., Green, A. E., Gentleman, A. S., Schaller, S., Schoellkopf, W., Fielicke, A., Mackenzie, S. R. 2020; 22 (33): 18606-18613


    Infrared multiple-photon dissociation spectroscopy has been applied to study Ptn(N2O)+ (n = 1-8) clusters which represent entrance-channel complexes on the reactive potential energy surface for nitrous oxide decomposition on platinum. Comparison of spectra recorded in the spectral region 950 cm-1 to 2400 cm-1 with those simulated for energetically low-lying structures from density functional theory shows a clear preference for molecular binding via the terminal N atom, though evidence of O-binding is observed for some cluster sizes. Enhanced reactivity of Ptn+n≥ 6 clusters towards N2O is reflected in the calculated reactive potential energy surfaces and, uniquely in the size range studied, Pt6(N2O)+ proved impossible to form in significant number density even with cryogenic cooling of the cluster source. Infrared-driven N2O decomposition, resulting in the formation of cluster oxides, PtnO+, is observed following vibrational excitation of several Ptn(N2O)+ complexes.

    View details for DOI 10.1039/d0cp02800b

    View details for Web of Science ID 000565157900032

    View details for PubMedID 32785404

  • Infrared Study of OCS Binding and Size-Selective Reactivity with Gold Clusters, Au-n(+) (n=1-10) JOURNAL OF PHYSICAL CHEMISTRY A Green, A. E., Schaller, S., Meizyte, G., Rhodes, B. J., Kealy, S. P., Gentleman, A. S., Schoellkopf, W., Fielicke, A., Mackenzie, S. R. 2020; 124 (26): 5389-5401


    OCS binding to and reactivity with isolated gold cluster cations, Aun+ (n = 1-10), has been studied by infrared multiple photon dissociation (IR-MPD) spectroscopy in conjunction with quantum chemical calculations. The distribution of complexes AunSx(OCS)m+ formed reflects the relative reactivity of different cluster sizes with OCS, under the multiple collision conditions of our ablation source. The IR-MPD spectra of Aun(OCS)+ (n = 3-10) clusters are interpreted in terms of either μ1 or μ2 S binding motifs. Analysis of the fragmentation products following infrared excitation of parent Aun(OCS)+ clusters reveals strongly size-selective (odd-even) branching ratios for OCS and CO loss, respectively. CO loss signifies infrared-driven OCS decomposition on the cluster surface and is observed to occur predominantly on even n clusters (i.e., those with odd electron counts). The experimental data, including fragmentation branching ratios, are consistent with calculated potential energy landscapes, in which the initial species trapped are molecularly bound entrance channel complexes, rather than global minimum inserted structures. Attempts to generate Rhn(OCS)+ and Ptn(OCS)+ equivalents failed; only sulfide reaction products were observed in the mass spectrum, even after cooling the cluster source to -100 °C.

    View details for DOI 10.1021/acs.jpca.0c03813

    View details for Web of Science ID 000547461000015

    View details for PubMedID 32491870

  • IR Signature of Size-Selective CO2 Activation on Small Platinum Cluster Anions, Pt-n(-) (n=4-7) ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Green, A. E., Justen, J., Schoellkopf, W., Gentleman, A. S., Fielicke, A., Mackenzie, S. R. 2018; 57 (45): 14822-14826


    Infrared multiple photon dissociation spectroscopy (IR-MPD) has been employed to determine the nature of CO2 binding to size-selected platinum cluster anions, Ptn - (n=4-7). Interpreted in conjunction with density functional theory simulations, the results illustrate that the degree of CO2 activation can be controlled by the size of the metal cluster, with dissociative activation observed on all clusters n≥5. Of potential practical significance, in terms of the use of CO2 as a useful C1 feedstock, CO2 is observed molecularly-bound, but highly activated, on the Pt4 - cluster. It is trapped behind a barrier on the reactive potential energy surface which prevents dissociation.

    View details for DOI 10.1002/anie.201809099

    View details for Web of Science ID 000452234400023

    View details for PubMedID 30207020

  • Infrared Spectroscopy of Au+(CH4)(n) Complexes and Vibrationally-Enhanced C-H Activation Reactions TOPICS IN CATALYSIS Gentleman, A. S., Green, A. E., Price, D. R., Cunningham, E. M., Iskra, A., Mackenzie, S. R. 2018; 61 (1-2): 81-91


    A combined spectroscopic and computational study of gas-phase Au+(CH4) n (n = 3-8) complexes reveals a strongly-bound linear Au+(CH4)2 core structure to which up to four additional ligands bind in a secondary coordination shell. Infrared resonance-enhanced photodissociation spectroscopy in the region of the CH4 a 1 and t 2 fundamental transitions reveals essentially free internal rotation of the core ligands about the H4C-Au+-CH4 axis, with sharp spectral features assigned by comparison with spectral simulations based on density functional theory. In separate experiments, vibrationally-enhanced dehydrogenation is observed when the t 2 vibrational normal mode in methane is excited prior to complexation. Clear infrared-induced enhancement is observed in the mass spectrum for peaks corresponding 4u below the mass of the Au+(CH4) n=2,3 complexes corresponding, presumably, to the loss of two H2 molecules.

    View details for DOI 10.1007/s11244-017-0868-z

    View details for Web of Science ID 000428065700010

    View details for PubMedID 31258301

    View details for PubMedCentralID PMC6560929

  • Growth Mechanism of Dendritic Hematite via Hydrolysis of Ferricyanide CRYSTAL GROWTH & DESIGN Green, A. E., Chiang, C., Greer, H. F., Waller, A., Ruszin, A., Webster, J., Niu, Z., Self, K., Zhou, W. 2017; 17 (2): 800-808
  • Cesium carbonate mediated aryl triflate esters' deprotection TETRAHEDRON LETTERS Green, A. E., Agouridas, V., Deniau, E. 2013; 54 (51): 7078-7079