Tuning the Properties of Metal-Ligand Complexes to Modify the Properties of Supramolecular ...

213 Pages·2014·1.88 MB·English

by  Ian Henderson

UUnniivveerrssiittyy ooff MMaassssaacchhuusseettttss AAmmhheerrsstt
SScchhoollaarrWWoorrkkss@@UUMMaassss AAmmhheerrsstt
Open Access Dissertations
5-2012
TTuunniinngg tthhee PPrrooppeerrttiieess ooff MMeettaall--LLiiggaanndd CCoommpplleexxeess ttoo MMooddiiffyy tthhee
PPrrooppeerrttiieess ooff SSuupprraammoolleeccuullaarr MMaatteerriiaallss
Ian Henderson
University of Massachusetts Amherst
Follow this and additional works at: https://scholarworks.umass.edu/open_access_dissertations
Part of the Polymer and Organic Materials Commons
RReeccoommmmeennddeedd CCiittaattiioonn
Henderson, Ian, "Tuning the Properties of Metal-Ligand Complexes to Modify the Properties of
Supramolecular Materials" (2012). Open Access Dissertations. 555.
https://doi.org/10.7275/w9wa-k694 https://scholarworks.umass.edu/open_access_dissertations/555
This Open Access Dissertation is brought to you for free and open access by ScholarWorks@UMass Amherst. It
has been accepted for inclusion in Open Access Dissertations by an authorized administrator of
ScholarWorks@UMass Amherst. For more information, please contact [email protected].
TUNING THE PROPERTIES OF METAL-LIGAND COMPLEXES
TO MODIFY PROPERTIES OF SUPRAMOLECULAR MATERIALS

A Dissertation Presented

BY

IAN M. HENDERSON

Submitted to the Graduate School of the
University of Massachusetts Amherst in partial fulfillment
of the requirements for the degree of

DOCTOR OF PHILOSOPHY

May 2012

Polymer Science and Engineering
 Copyright Ian M. Henderson 2012

All Rights Reserved
TUNING THE PROPERTIES OF METAL-LIGAND COMPLEXES
TO MODIFY PROPERTIES OF SUPRAMOLECULAR MATERIALS

A Dissertation Presented

BY

IAN M. HENDERSON

Approved as to style and content by:

________________________________
Ryan C. Hayward, Chair

________________________________
E. Bryan Coughlin, Member

________________________________
Dhandapani Venkataraman, Member

___________________________
David A. Hoagland,
Department Head
Polymer Science and
Engineering
Dedicated it to whoever makes it past this page
ACKNOWLEDGMENTS

Firstly, I would like to extend my appreciation to my advisor Prof. Ryan C.
Hayward for his guidance and assistance throughout my years at UMass. I am thankful
for the knowledgeable guidance he has given, as well as the opportunities he has given
me to disseminate my research at conferences and in scientific journals. I would also like
to thank the members of my committee Prof. E. Bryan Coughlin and Prof. D.
Venkataraman for their guidance throughout my Ph.D. career. Without their input, it is
doubtful that I would have become the scientist that I am today.
I would like to thank my friends from UMass for their friendship and support. I
would especially like to thank, in no particular order, Scott and Jess, Sami, Marcos,
Sandy, Erik, Joe, Emily, and C.J. While the list could go on, these individuals have made
my time in Massachusetts more enjoyable. I would also like to thank the staff members
at PSE, Jack, Vivien, Lisa, and Steve for their help in my graduate research.
I would also like to thank my family members, my mother, father, and my sister,
for their love and support. Without you, none of this would have been possible.
v
ABSTRACT
TUNING THE PROPERTIES OF METAL-LIGAND COMPLEXES TO MODIFY
PROPERTIES OF SUPRAMOLECULAR MATERIALS

MAY 2012

IAN M. HENDERSON

B.SC., CASE WESTERN RESERVE UNIVERSITY

M.SC., UNIVERSITY OF MASSACHUSETTS AMHERST

PH.D., UNIVERSITY OF MASSACHUSETTS AMHERST

Directed by: Professor Ryan C. Hayward

Supramolecular chemistry is the study of discreet molecules assembled into more
complex structures though non-covalent interactions such as host-guest effects, pi-pi
stacking, electrostatic effects, hydrogen bonding, and metal-ligand interactions. Using
these interactions, complex hierarchical assembles can be created from relatively simple
precursors.
Of the supramolecular interactions listed above, metal-ligand interactions are of
particular interest due to the wide possible properties which they present. Factors such as
the denticity, polarizability, steric hindrance, ligand structure, and the metal used (among
others) contribute to a dramatic range in the physical properties of the metal-ligand
complexes. Particularly affected by these factors are the kinetic and thermodynamic
properties of the complexes. As a result metal-ligand interactions can vary from inert to
extremely transient.
vi
Of the vast number of ligands available for study, this dissertation will center on
substituted terpyridine ligands, with a particular focus on terpyridine-functionalized
polymers. While polymer-functionalized terpyridine ligands and their complexes with
transition metals have been heavily studied, the physical properties, particularly the
effects of polymer functionalization on the stability of bis complexes of terpyridines,
remain unexplored.
In the course of investigating the kinetic stability of these complexes, polymer
functionalization techniques were developed which were found to increase the stability of
the metal-ligand interactions compared to conventional techniques. In addition to
studying the effect of terpyridine substituents, the effects of solvent on the stability of the
complexes was studied as well. As polymer-bound terpyridine complexes are often
studied in solvents other than water, knowledge of the stability of the complexes in
organic solvents is important to create supramolecular structures with more precisely
controlled properties. It was found that, for unsubstituted terpyridyl complexes, the
stability of the complexes varied by as many as five orders of magnitude in common
solvents. It is believed that this decrease in stability is the result of the ability of the
solvent to facilitate the movement of the ligands from the first and second coordination
spheres.
Although a large part of this dissertation is dedicated to the study of the kinetic
stability of terpyridine complexes, synthetic techniques involving terpyridine and its
complexes were investigated as well. It was found that terpyridine functionalized
polystyrene could be produced by direction functionalization of terpyridine with
polystyryllithium. Additionally heterloleptic terpyridine-based iron complexes were
vii
produced with high purity by reduction of the mono terpyridine complex of iron(III) in
the presence of a second, functionalized terpyridine ligand. The culmination of these
studies was the synthesis of supramolecular organogels, which were crosslinked using
metal-terpyridine complexes, yielding dynamic mechanical properties could be broadly
tuned by varying the metal used to form the crosslinks.
.

viii
TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS ............................................................................................................... v
ABSTRACT .................................................................................................................................... vi
LIST OF TABLES ......................................................................................................................... xii
LIST OF FIGURES ...................................................................................................................... xiv
LIST OF SCHEMES..................................................................................................................... xvi
LIST OF SYMBOLS ................................................................................................................... xvii
LIST OF ABBREVIATIONS ..................................................................................................... xviii

CHAPTER

1. INTRODUCTION ....................................................................................................................... 1

1.1 Overview ....................................................................................................................... 1
1.2 Background .................................................................................................................... 3

1.2.1 A Brief Introduction to Metal-Ligand Chemistry .......................................................... 3
1.2.2 The Chelate Effect .......................................................................................................... 5
1.2.3. Origins of the Terpyridine Ligand ................................................................................ 7
1.2.4 Terpyridine Ligands Bearing Functional Groups ......................................................... 10
1.2.5 Terpyridine-Functionalized Polymers .......................................................................... 13
1.2.6 Properties of Selected Terpyridine Complexes ............................................................ 16
1.2.7 Terpyridne Kinetics ...................................................................................................... 20

1.3 References ................................................................................................................... 21

2. SYNTHESIS OF END-FUNCTIONALIZED POLYSTYRENE BY DIRECT
NUCLEOPHILIC ADDITION OF POLYSTYRYLLITHIUM TO BIPYRIDINE OR
TERPYRIDINE ............................................................................................................................. 27

2.1 Chapter Overview ......................................................................................................... 27
2.2 Introduction ................................................................................................................. 28
2.3 Experimental ................................................................................................................ 32
2.4 Results and Discussion .................................................................................................. 38
2.5 Conclusions ................................................................................................................. 48
2.6 Appendix 2A: Side Product Characterization, Detailed Synthetic Procedures, and Equal
Reactivity Model .......................................................................................................................... 50
2.7 Appendix 2B: Synthesis of Mid-Functionalized Block Copolymers ................................. 56
2.8 References ................................................................................................................... 60

3. SUBSTITUENT EFFECTS ON THE STABILITIES OF POLYMERIC AND SMALL
MOLECULE BIS-TERPYRIDINE COMPLEXES ....................................................................... 62

ix