Inner and outer sphere ligand effects on palladium pincer complexes as electrocatalysts for CO₂ reduction
department or school: Science, Faculty of
department or school: Chemistry, Department of
data provider: DSpace
degree campus: UBCV
creator: DeLuca, Emile Ettore
issued: 2018-09-06T15:29:01Z
issued: 2018
related degree: Master of Science - MSc
degree grantor: University of British Columbia
description: A series of novel palladium pincer complexes have been investigated for activity towards the electrochemical conversion of CO₂ to CO. Controlled variation of the inner and outer ligand sphere has provided mechanistic insight and valuable information towards rational ligand design for this variety of catalyst. Stabilizing interactions between charged electrocatalytic intermediates and a host of cationic residues were explored through the synthesis and characterization of six isoelectronic palladium bis(N-heterocyclic carbene) (NHC) complexes bearing unique onium functionalities. The presence of a positively charged, pendant substituent was found to mediate electrode kinetics and facilitate CO₂ coordination to the catalytic center in a systematic fashion. Ultimately, the introduction of cationic moieties onto this system was shown to enhance catalytic selectivity for the conversion of CO₂ to CO by as much as 5 times that of an alkyl-bearing analog. A combination of electrochemical experiments and computational analysis demonstrate that catalyst performance is most benefited by a bulky onium unit tethered to the catalyst through a flexible linker. This behavior was interpreted as the preference for a wide, hydrophobic reaction pocket that allows for the unhindered formation of catalytic intermediates and mediated interaction with the solution. With the aim of gaining better insight towards the influence of inner-sphere ligands on selectivity in palladium bis(N-heterocyclic carbene) CO₂ reduction catalysts, a novel, mixed phosphine-NHC complex was synthesized with variation in the fourth coordinate ligand and screened for activity towards the transformation of CO₂ to CO. The newly created structures were demonstrated to catalyze the reduction of CO₂ to CO in the presence of acetic acid with no deactivation detected after several hours of electrolysis. In addition to exhibiting versatility in the palladium bis-(NHC) pincer motif, this marks the first report of a palladiu…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/67124
note: Inner and Outer Sphere Ligand Effects on Palladium Pincer Complexes as Electrocatalysts for CO2 Reduction by Emile Ettore DeLuca B.Sc. Chemistry, The University of Montana, 2015 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Chemistry) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) August 2018 © Emile Ettore DeLuca, 2018 ii The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, a thesis/dissertation entitled: Inner and Outer Sphere Ligand Effects on Palladium Pincer Complexes as Electrocatalysts for CO2 Reduction submitted by Emile DeLuca in partial fulfillment of the requirements for the degree of Master of Science in Chemistry Examining Committee: Professor Michael O. Wolf Supervisor Professor Jennifer Love Supervisory Committee Member Professor Chris Orvig Supervisory Committee Member Professor R. Brian Additional Examiner iii Abstract A series of novel palladium pincer complexes have been investigated for activity towards the electrochemical conversion of CO2 to CO. Controlled variation of the inner and outer ligand sphere has provided mechanistic insight and valuable information towards rational ligand design for this variety of catalyst. Stabilizing interactions between charged electrocatalytic intermediates and a host of cationic residues were explored through the synthesis and characterization of six isoelectronic palladium bis(N-heterocyclic carbene) (NHC) complexes bearing unique onium functionalities. The presence of a positively charged, pendant substituent was found to mediate electrode kinetics and facilitate CO2 coordination to the catalytic center in a systematic fashion. Ultimately, the introduction of cationic moieties onto this system was shown to enhance catalytic selectivity for the conversion of CO2 to CO by as much as 5 times that of an alkyl-bearing analog. A …
has type: Thesis/Dissertation
date issued: 2018-11
is shown at: 10.14288/1.0371938
language: eng
degree discipline: Chemistry
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
type: Text
identifier URI: http://hdl.handle.net/2429/67124