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  • MOLECULAR REACTIONS ON SURFACES: TOWARDS THE GROWTH OF SURFACE-

    CONFINED POLYMERS

    Maryam Abyazisani

    B.Sc. and M.Sc.

    Submitted in fulfilment of the requirements for the degree of

    Doctor of Philosophy

    School of Chemistry, Physics and Mechanical Engineering

    Science and Engineering Faculty

    Queensland University of Technology

    2019

  • To love of my life

  • Molecular reactions on surfaces: towards the growth of surface-confined polymers i

    Abstract

    The development of surface-confined nanostructures is a promising approach

    towards developing new electronic and optoelectronic devices. Molecular assembly

    under ultra-high vacuum (UHV) conditions offers precise control over the reaction

    conditions. Despite all the control provided by the UHV, achieving high quality and

    well-ordered nanostructures in both one and two dimensions is still a challenging

    problem. A detailed understanding of the reaction of a range of molecules on surfaces

    will be the key to developing targeted strategies for on-surface synthesis.

    In this regard, the Ullmann reaction is very well-studied and constitutes an aryl-

    aryl coupling of halogenated moieties. This reaction produces chemisorbed metal

    halides as a byproduct and has consequently been a hotly-debated issue owing to the

    presumed detrimental effects on the quality of the products. To find a solution for this

    challenge, this thesis aims to contribute to the understanding of the absence of metal

    halide byproducts in two ways. Firstly, employing the decarboxylative coupling

    known as a “clean” reaction which produces volatile byproducts, and secondly in

    removing the metal halide byproducts resultant from the Ullman reaction by using

    hydrogen etching following the polymerisation step.

    To investigate the decarboxylative reaction, the adsorption and reaction of 3,5-

    pyridinedicarboxylic acid (PDC) and isophthalic acid (IPA) have been studied using

    photoemission spectroscopy (PES) and near edge x-ray absorption fine structure

    (NEXAFS) at the Australian Synchrotron facility. PE spectra of PDC reveal the

    presence of nitrogen on the central group of the precursor result in different adsorption

    configurations of the molecule on the surface: (a) via the nitrogen, and (b) via the

    deprotonated carboxyl group. The result from NEXAFS supports that molecules are

    adsorbed tilted with respect to the surface. The extracted activation energy for PDC

    decarboxylation is (1.93 ± 0.17) eV which is large compared to the activation energy

    for decarboxylation of a planar aromatic molecule, suggesting the tilted adsorption

    configuration may change the activation energy. These results reveal a competition

    between decarboxylation and molecular fragmentation at temperatures near

    decarboxylation temperature.

  • ii Molecular reactions on surfaces: towards the growth of surface-confined polymers

    Photoemission spectra of IPA reveal that the molecule partially deprotonated

    upon adsorption on Cu(111). In addition, the beam energy dependence and angular

    dependence spectroscopy of the IPA illustrates the relative geometry of the carboxyl

    group, deprotonated carboxyl group and phenyl ring. The deprotonated carboxyl group

    is buried beneath the phenyl ring, suggesting the molecule is anchored to the surface

    via the deprotonated carboxyl group, and the NEXAFS data support the PES result.

    Furthermore, STM illustrates that decarboxylative coupling of IPA successfully

    proceeds on Cu(111). The IPA and PDC studies represent a step forward in

    understanding the decarboxylation reaction and highlight the importance of the

    chemistry of the building block in the adsorption geometry of the molecule and

    therefore in the polymerization reaction.

    To study the removal of by-product halogens from the surface, 1,4

    dibromobenzene was deposited on Cu(111) and Cu(110). Atomic hydrogen was dosed

    to the surface after the polymerization reaction completed. STM and XPS data

    confirmed that halogens have been removed from the surface. This characteristic opens

    up the possibility of employing the Ullmann reaction while a flux of atomic hydrogen

    may offer effective way for removing unwanted halide by-products and a possibility

    for improving the network qualities as well as polymer’s coverage on the surface.

  • Molecular reactions on surfaces: towards the growth of surface-confined polymers iii

    Table of Contents

    Abstract ..................................................................................................................................... i

    Table of Contents .................................................................................................................... iii

    List of Publication .....................................................................................................................v

    List of Figures ....................................................................................................................... viii

    List of Tables ..........................................................................................................................xv

    List of Abbreviations ............................................................................................................ xvi

    Statement of Original Authorship ........................................................................................ xvii

    Acknowledgements ............................................................................................................. xviii

    Chapter 1: Introduction ...................................................................................... 1

    1.1 Background .....................................................................................................................1

    1.2 Context ............................................................................................................................2

    1.3 Purposes ..........................................................................................................................3

    1.4 Thesis Outline .................................................................................................................4

    1.5 References ......................................................................................................................5

    Chapter 2: Literature Review ............................................................................. 7

    2.1 Historical Background ....................................................................................................7

    2.2 Ullmann Reaction ...........................................................................................................9

    2.3 Decarboxylation Reaction ............................................................................................23

    2.4 Pyridine-Based Polymer ...............................................................................................25

    2.5 Summary and Implications ...........................................................................................29

    2.6 References ....................................................................................................................32

    Chapter 3: Research Design .............................................................................. 39

    3.1 Important Parameters In Surface-Confined Reactions .................................................39

    3.2 Surface Sensitive Analysis Techniques ........................................................................45

    3.3 References ....................................................................................................................52

    Chapter 4: Adsorption and Reactivity of Pyridine Dicarboxylic Acid on Cu(111) .......................................................................................................... 55

    4.1 Abstract .........................................................................................................................57

    4.2 Introduction ..................................................................................................................58

    4.3 Experimental Methods ..................................................................................................59

    4.4 Results ..........................................................................................................................62

    4.5 Discussion .....................................................................................................................73

    4.6 Conclusions ..................................................................................................................75

    4.7 References ....................................................................................................................77

  • iv Molecular reactions on surfaces: towards the growth of surface-confined polymers

    4.8 Supporting Information ................................................................................................ 82

    Chapter 5: Adsorption, deprotonation and decarboxylation of isophthalic

    acid on Cu(111) ............