Clark Lecture Series, Elizabeth Young, Lehigh Univers
Associate Professor
Department of Chemistry
Solar light harvesting and interconversion of solar energy into either electricity
or drivingforce for small molecule activation reactions are critical to the production
of energy andother processes that our society requires to function. In this talk,
I will discuss three projectsunited by photochemistry, each with their own application.
In the first vignette, I will discussa porphyrinoid complex, called a Pd(II)biladiene,
This Pd(II)biladiene moiety was designedfor use as a photosensitizer drug for
photodynamic therapy. Up until this point, the excited-state dynamics of such
biladiene complexes have been virtually unexplored. During our workon this moiety,
we discovered that while excitation into the lowest-energy absorption featureof
the Pd(II)biladiene complexes produces expected photophysics, interestingly,
excitationinto higher-lying excited states resulted in an additional, unexpected
lifetime. I will discussour work to propose the cause of this unexpected behavior.
In the second vignette, I willdiscuss our recent work on a ubiquitous industrial
dye that is a major cause of pollution indeveloping countries. Azo dyes are a
class of organic molecules defined by an N=N doublebond connecting two aromatic
moieties. They are the single most common dyes used inindustrial processes, found
in everything from colorants and cosmetic additives to textilereagents, biologic
indicators, and organic synthons. They present a significant pollutionproblem
because untreated dyes released into waterways can be ingested and are toxic
tohumans and animals. Our recent studies shed light on their photophysics and
how we canmanipulate their photophysical evolution. In the third vignette, I
will discuss a Re-carbonylcomplex that we designed for use in excited-state proton-coupled
electron transfer (PCET)mechanistic investigations. PCET mechanisms can be employed
to improve energetic andkinetic favorability of chemical transformations or to
direct chemical reactivity, and we canseek additional energetic advantage by
using solar energy to drive such coupled reactions.This Re-carbonyl complex has
demonstrated an unexpected photophysical dependence onthe ligand protonation
state that we rationalize using density functional theory calculations.