Synthesis and Photophysical Characterization of pi-Conjugated Nonlinear Absorbing ...

182 Pages·2011·2.34 MB·English

SYNTHESIS AND PHOTOPHYSICAL CHARACTERIZATION OF -CONJUGATED
NONLINEAR ABSORBING ORGANOMETALLIC PLATINUM COMPLEXES

By

ABIGAIL HOBBS SHELTON

A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA

2011
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© 2011 Abigail Hobbs Shelton

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To Phillip, my sweetheart and sunshine

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ACKNOWLEDGMENTS
I must first acknowledge my advisor, Dr. Kirk Schanze. His support, advice, and
knowledge have provided me the opportunity to work in an environment where I could
tinker with instrumentation and explore physical inorganic chemistry. I would also like to
thank my committee members, Dr. Stephen Hagen, Dr. Lisa McElwee-White, Dr.
Michael Scott, and Dr. Dan Talham, for their time and support.
Large portions of my projects could not have been completed without the NMR
help of Dr. Ion Ghiviriga, the X-Ray crystallographic guidance of Dr. Khalil Abboud and
his team, the instrumentation help of Dr. Ben Smith, and the creative skills of Joe
Shalosky, Brian Smith, and Todd Prox in the machine shop and Steve Miles and Larry
Hartley in the electronic shop. I would also like to thank Dr. Schanze and the United
States Air Force for project funding during my graduate career. Additionally, I am
grateful for funding provided by the CLAS dissertation fellowship.
My family has provided a stable and supportive network for me. Though I travelled
a bit far from home to attend graduate school, they have constantly been here for me
with encouragement, advice, and faith. I thank them for their moral support and
prayers. I am eternally grateful for Phillip, for his unceasing love and support.
I am also grateful for the many friendships I made while here – for Seth and Molly
Dumbris, Sarah Stefans, Brad House, Julia and Jonathan Keller, David Snead and
Stephanie Elder, for keeping the friendships going even when we all became stressed
with work. Special thanks go to Jenny Johns for literally helping me survive the last
several months, and for tolerating the many adventures I subjected her to. I also thank
the McElwee-White group members, for adopting me as an honorary member and
letting me invade their space. I am also grateful for Ann Moore for working her magic.
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I am much indebted to the numerous past and present Schanze group researchers
who helped pave the way for me. I would like to thank Julia Keller, Emine Demir, and
Anand Parthasarthy for the many, many conversations on synthetic options and
additionally for Randi Price, Rett Vella, Dongping Xie, and Yongjun Li for also letting me
make messes and take up their space. I am especially grateful for my lab mates who
selflessly gave of their time to introduce me to the laboratory and teach me instruments,
specifically Richard Farley, John Peak, and Kye-Young Kim for teaching me the
wonders that are the laser lab. Special thanks go to Randi Price for not only teaching
me instruments, but designing and fabricating instruments and software programs that I
needed! Additionally, thanks go to Luisa Brokmann and Barbara Dettlaff, who
synthesized portions of the chromophores used in many of my projects.
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TABLE OF CONTENTS

page
ACKNOWLEDGMENTS .................................................................................................. 4
LIST OF TABLES ............................................................................................................ 9
LIST OF FIGURES ........................................................................................................ 10
ABSTRACT ................................................................................................................... 13
CHAPTER
1 INTRODUCTION .................................................................................................... 15
Basic Principles of Photophysics ............................................................................ 15
Linear Absorption of Light ................................................................................. 16
Emission of Light .............................................................................................. 19
Nonlinear Absorption ........................................................................................ 23
Two-photon absorption .............................................................................. 23
Excited state absorption ............................................................................. 24
Combined two-photon absorption and excited state absorption................. 24
Platinum Acetylide Materials ................................................................................... 28
Synthesis of Platinum Acetylides ...................................................................... 29
Photophysics .................................................................................................... 30
Design Paradigms ............................................................................................ 26
Linear Optical Properties .................................................................................. 33
Nonlinear Optical Properties ............................................................................. 34
Phenylethynyl-based platinum acetylides .................................................. 34
Platinum acetylides with heteroatomic ligands ........................................... 37
Platinum acetylides with TPA chromophores ............................................. 39
Objective of Present Study ..................................................................................... 41
2 OPEN APERTURE Z-SCAN APPERATUS AND RESPONSE ............................... 44
Background ............................................................................................................. 44
Techniques ............................................................................................................. 45
Open Aperture Z-Scan Apparatus .......................................................................... 49
Hardware .......................................................................................................... 49
Software and Data Collection ........................................................................... 51
NLA Test Series ...................................................................................................... 53
Platinum and Iridium Cyclometalated Complexes ............................................ 53
Design ........................................................................................................ 54
Characterization ......................................................................................... 55
Platinum End-Capped Phenylene Ethynylene Oligomers ................................ 58
Introduction ................................................................................................ 58
Characterization ......................................................................................... 59
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Results and Discussion ........................................................................................... 60
NLA Response ................................................................................................. 60
Limitations of Current System .......................................................................... 64
Experimental ........................................................................................................... 66
Materials and Instrumentation .......................................................................... 66
Synthesis .......................................................................................................... 68
3 STEREOCHEMICAL EFFECTS OF PLATINUM ACETYLIDES ............................. 72
Introduction ............................................................................................................. 72
Synthesis ................................................................................................................ 78
Results and Discussion ........................................................................................... 79
NMR Characterization ...................................................................................... 79
1H NMR characterization. ........................................................................... 79
31P NMR characterization. ......................................................................... 80
X-Ray Crystallography...................................................................................... 81
cis-PE2 ...................................................................................................... 81
cis-BTF ...................................................................................................... 85
Ground State Absorption Spectroscopy ........................................................... 89
Steady-State Photoluminescence Spectroscopy .............................................. 92
Transient Absorption Spectroscopy and Triplet Excited State Lifetimes .......... 96
Nonlinear Absorption ........................................................................................ 98
Conclusions .......................................................................................................... 100
Experimental ......................................................................................................... 103
Instrumentation ............................................................................................... 103
Materials and Synthesis ................................................................................. 106
4 PLATINUM ACETYLIDE MONOMERS AND POLYMERS ................................... 119
Introduction ........................................................................................................... 119
Synthesis .............................................................................................................. 122
Platinum Acetylides ........................................................................................ 122
Polymerization ................................................................................................ 123
Film Preparation ............................................................................................. 125
Results and Discussion ......................................................................................... 125
Ground State Absorption Spectroscopy ......................................................... 127
Steady State Photoluminescence Spectroscopy ............................................ 129
Triplet-Triplet Transient Absorption ................................................................ 132
Nonlinear Absorption Response ..................................................................... 136
Conclusions .......................................................................................................... 139
Experimental ......................................................................................................... 141
Instrumentation ............................................................................................... 141
Materials and Synthesis ................................................................................. 144

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APPENDIX
A USER MANUAL FOR OPEN-APERTURE Z-SCAN APPARATUS ....................... 154
B X-RAY CRYSTAL STRUCTURE PARAMETERS ................................................. 162
LIST OF REFERENCES ............................................................................................. 172
BIOGRAPHICAL SKETCH .......................................................................................... 182

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LIST OF TABLES
Table page

2-1 Linear optical properties of Pt(II) and Ir(III) complexes in THF. .......................... 56
2-2 Summary of photophysical properties of Ph Pt series in THF. .......................... 59
n 2
3-1 31P NMR signals of the cis and trans platinum acetylide complexes .................. 81
3-2 Selected bond distances (Å) and bond angles (degrees) observed in cis-PE2
and trans-PE2. .................................................................................................... 82
3-3 Selected bond distances (Å) observed in trans-BTF and cis-BTF. ..................... 87
3-4 Selected bond angles (degrees) observed in trans-BTF and cis-BTF. ............... 87
3-5 One-photon photophysical properties of the cis and trans platinum acetylide
series in THF. ..................................................................................................... 92
3-6 Triplet excited state properties of cis and trans platinum acetylide series in
THF. ................................................................................................................... 95
4-1 Polymer molecular weights and PDIs ............................................................... 126
4-2 Summary of photophysical properties of the polymer series in THF ................. 129

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LIST OF FIGURES
Figure page

1-1 Franck-Condon principle. ................................................................................... 18
1-2 Electrons of ground and excited states. .............................................................. 19
1-3 Jablonski diagram illustrating radiative and nonradiative transitions. ................. 20
1-4 A simplified Jablonski diagram of a molecule that exhibits NLA via TPA and
triplet-triplet ESA. ................................................................................................ 26
1-5 Cartoons illustrating the design principles behind organometallic TPA/ESA
complexes. ......................................................................................................... 27
1-6 Structure units of a platinum acetylide oligomer and polymer. ........................... 28
1-7 Synthetic routes for generation of platinum acetylides ....................................... 29
1-8 Ligand field splitting diagram for metal d orbitals in a square planar complex. ... 30
1-9 Potential energy surface for the d-d excited state in a square planar d8
complex, formed by population of the d orbital. ............................................. 31
x2-y2
1-10 Potential energy surface and ligand field splitting diagram of square planar
Pt(II) complexes with ligand excited states and metal d8 states. ........................ 32
1-11 Structure of trans-PE2. ....................................................................................... 35
1-12 Butadiyne platinum acetylide oligomers structures. ............................................ 36
1-13 Platinum acetylide polymers examined by Wilson .............................................. 38
1-14 Thiophene-containing platinum acetylides, as examined by Glimsdal. ............... 38
1-15 Platinum acetylides with TPA chromophores ..................................................... 39
1-16 DPAF-endcapped di-platinum acetylides with various core aryl units. ................ 40
2-1 Linear and nonlinear absorption response as a function of transmittance
versus input energy. ........................................................................................... 45
2-2 Components of the z-scan apparatus ................................................................. 46
2-3 Z-scan plots of C60 in toluene at an excitation wavelength of 1064 nm ............. 48
2-4 Nanosecond open aperture z-scan apparatus instrument schematic. ................ 50
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