Transcript Porphyrins - The Evergreen State College

Porphyrin Research at the
Evergreen State College:
The Synthesis, Separation, Isolation and
Characterization of Di-functional
meso-substituted Porphyrins
(An Advancement toward
Solar Energy Harvesting
Technologies)
Introduction

The process of photosynthesis has interested humanity
for eons. It is arguably the most important biological
process on earth and is responsible for a large portion
of our current energy needs.
Structural Formulas:
.
Chlorophyll:

In plants, the green pigment chlorophyll absorbs light
energy. Chlorophyll is a porphyrin molecule that
resides in the thylakoid membrane of the chloroplast.
And
Porphyrins:

Natural pigments containing a fundamental skeleton of
four pyrrole nuclei united through the alpha positions
by four methine groups to form a macrocylic structure
( IUPAC Compendium of Chemical Terminology 2nd Edition)
Photovoltaic cell:

When sunlight strikes the surface of these cells an
electrical field provides both momentum and direction
to electrons that results in a flow of current.
Image: {WWW.Altenergy.com}
Photovoltaic cell:

These cells can be connected electrically in series
and/or parallel circuits to produce higher, currents,
voltage and power levels.
Image: {WWW.Altenergy.com}
Gratzell cell:
A proposed design
for a solar cell which
utillizes porphyrins.

Image: {WWW.Chem.pdx.edu}
Synthesis:

For the initial synthesis of these porphyrins, the
Rothemund Method was utilized. This technique was
first developed during the 1930’s and later improved
upon in the 70’s by the Adler research group at the
University of Pennsylvania.
Synthesis:

For the initial synthesis of these porphyrins, the
Rothemund Method was utilized. This technique was
first developed during the 1930’s and later improved
upon in the 70’s by the Adler research group at the
University of Pennsylvania.
The synthesis of meso-Tri(Tolyl)
Mono(4-carboxyphenyl) Porohyrin
Isolation:

When two types of aldehydes are used, this reaction
mechanism will produce five different structural
isomers.
Column Chromatography:

The technique of column chromatography was
developed in 1906 by the Italian-born Russian botanist
Mikhail Tswett. During the process, a mixture of
compounds is dissolved into a liquid phase and
allowed to flow through a column of powdered calcium
carbonate in a vertical glass tube.
Isolation:

The roto-vap, or rotary evaporator, is a device
that allows a liquid to be evaporated in a
controlled manner
NMR Spectroscopy:

NMR is a technique that was developed in
1945 by American physicists Felix Bloch and
Edward Mills Purcell.

This technique is based on the principle that a
spinning photon generates a magnetic field.

During NMR, a substance is placed in a strong
magnetic field causing the protons to align with
the stronger field in a lower energy state

A radio wave is passed through the substance
supplies the resonance frequency needed to
excite the protons to the higher energy state

The use of NMR spectroscopy for structural
determination arises because protons in a
substance experience slightly different
magnetic fields.
Example of a NMR Spectrum:

meso-Tetra (Tolyl) Porphyrin NMR spectrum
UV-Vis Spectroscopy:

When a sample is irradiated with UV light, it causes the promotion
of an electron from a ground electronic state to an excited
electronic state
Image: {WWW.sci/lib/Upenn.edu}

Absorption is described by the log of radiant power
entering the sample, P0, divided by the radiant power
leaving the sample, P, and is directly proportional to the
path length, l, and the concentration, c, of the
absorbing species multiplied by, e, a constant of
proportionality, called the absorbtivity or epsilon value.

Because of the way absorption is defined, The total
power absorbed by a molecule in the Uv-Vis region of
the EM spectrum can be calculated by tacking the
integral of the derivative of the power absorbed with
respect to the change in wavelength and multiplying it
by the change in wavelength.
Example of a UV-Vis Spectrum:

meso-Tetra (Tolyl) Porphyrin Uv-Vis spectrum
Other Applications of Porphyrins

1. Current electronics research is focused on producing computers
that are faster and more compact (The intriguing possibility of making
electronic components from single molecules or small groups of
molecules is becoming a large area of research. Another very active area
of research is computers that use light, rather than electrons, as the
medium for carrying information. In principle, light-based computers have
several advantages over traditional designs) Proffesor Deven Gust of ASU
Image: {WWW.ArmyTechnology.com}
Other Applications of Porphyrins

2. Light has a very high energy content, and cause serious
damage to living organisms. For example, sunlight absorbed by
photosynthetic chlorophyll will sometimes cause tissue damage in
plants. Furthermore, It has been shown that certain porphyrins will
localize in cancerous tumor tissue. Illumination of this area results
in photochemical damage which destroys the tumor while leaving
surrounding tissue undamaged.
Image: {WWW.Cancerresearch.com}
Thanks: