Doctoral defense in Chemistry - Angel Andrés Castro Ruiz

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Ph.D. candidate: Angel Andrés Castro Ruiz

Dissertation title: Bioinspired cobalt amino acid complexes for
oxygenated high value-added materials.

Opponents: Dr. Anna Trzeciak, Professor at the Faculty of Chemistry, University of Wrocław, Poland and Dr. Erwan LeRoux, Associate Professor at the Chemistry Department, University of Bergen, Norway.

Advisor: Dr. Sigríður Guðrún Suman, Professor at the Faculty of Physical Sciences, University of Iceland.

Doctoral committee: Dr. Sigríður Jónsdóttir, Research Scholar at the Faculty of Physical Sciences, University of Iceland and Dr. Már Másson, Professor at the Faculty of Pharmaceutical Sciences, University of Iceland.

Chair of Ceremony: Dr. Einar Örn Sveinbjörnsson, Professor and the Head of the Faculty of Physical Sciences, University of Iceland.

Abstract

Today, society is reliant on nonrenewable fossil fuels and petrochemical derivatives. As the global population increases, energy and materials are rapidly diminishing, and a drastic, responsive change is needed to achieve a more sustainable world. It is essential to incorporate circular economy principles into the chemical industry and academia to meet United Nations Global Sustainable Development Goals. To address global challenges such as climate change and the reduction of anthropogenic activities on the planet, multidisciplinary research in contemporary chemistry areas is fundamental to ensure a paradigm shift. CO2 pollution is one of the most striking manifestations of climate change and, therefore, a very apt subject to tackle across disciplines. In this sense, researchers must prioritize carbon dioxide (CO2) transformation and the development of alternative polymers to the current hydrocarbons. In this work, a bio-inspired catalytic platform for CO2 fixation and oxygenated polymer synthesis was designed. The synthesis and characterization of three series of cobalt(II/III) complexes coordinated by either 2,2’- bipyridine (bipy), or 4,4’-di-tert-butylbipyridine (dtbbpy) and amino acid as ligands was achieved. Their application as catalysts for the ring opening polymerization of rac-lactide to form the alternative biopolymer poly(lactic acid) (PLA), the coupling reaction of epoxide/CO2, or epoxide/cyclic anhydride to produce oxygenated high value-added materials was investigated. Cobalt(II) amino acid complexes successfully homopolymerized rac-lactide. An oxidated version of the cobalt amino acid complexes Co(III) in a binary catalytic system showed outstanding activity in CO2-based cyclic carbonate synthesis. Modification of these complexes by using dtbbpy ligand and same set of amino acid ligands resulted in increased solubility and ability to convert epoxides and anhydride into polyesters with a turnover frequency of (TOF of 1151 h-1), which is comparable to the currently leading catalysts in the literature. Overall, this thesis work provides insight into catalyst mechanisms and future design options for bioinspired catalytic platforms.

About the candidate

Originally from Cabruta, Guárico-Venezuela, Andrés completed his BS degree in Chemistry with Interdisciplinary Studies in Chemical Engineering at the University of Los Andes, Mérida-Venezuela. In 2018 he received his MS in Polymer Technology at the Research Center of Applied Chemistry located in Coahuila-Mexico under the supervision of Dr. Graciela Morales. His final year work aimed at the development of fibrous polymeric scaffolds by electrodynamic techniques for water purification. Andrés joined Prof. Sigríður Suman's research group at the University of Iceland in May 2019 as a Ph.D. student. His work focuses on the synthesis of bioinspired coordination complexes and their application as homogeneous catalysts in the production of high-value-added oxygenated materials from renewable resources.