Toward the Synthesis of a Stable Water-Soluble Manganese(II) Porphyrin

.
TOWARD THE SYNTHESIS OF A STABLE WATER-SOLUBLE
MANGANESE(II) PORPHYRIN
RESEARCH CONDUCTED & REPORT PREPARED BY:
Nicholas O. Gober
Undergraduate Student (B.S., Biochemistry, 2016)
Georgia Institute of Technology
College of Sciences, School of Chemistry & Biochemistry
901 Atlantic Drive NW, Atlanta, GA 30318, USA
P: (404) 894-4002 | F: (404) 894-7452
PRINCIPAL INVESTIGATOR: SPONSORING INSTITUTIONS:
Rosalie A. Richards, Ph.D.
Associate Provost for Faculty Development
& Professor of Chemistry and Education
Stetson University, Office of the Provost and
Academic Affairs
421 N. Woodland Blvd., Unit 8358
DeLand, FL 32723, USA
rrichar1@stetson.edu | (386)-822-7906
Project Funding:
ACS Project SEED Program
American Chemical Society
1155 Sixteenth Street NW, Room 833
Washington, DC 20036, USA
projectseed@acs.org | (800)-227-5558 ext. 4380
Laboratory Facilities:
Georgia College and State University
Dept. of Chemistry, Physics, & Astronomy
301 Herty Hall, Campus Box 82
Milledgeville, GA 31061, USA
(478)-445-5769 | darlene.hubbard@gcsu.edu

Toward the Synthesis of a Stable Water-Soluble Manganese(II) Porphyrin Gober, N. O.
2
TABLE OF CONTENTS
Abstract........................................................................................................................................................................3
Introduction..............................................................................................................................................................4
Porphyrin Chemistry & Problem...................................................................................................................6
Literature Overview & Hypothesis...............................................................................................................7
Reagents & Instrumentation............................................................................................................................8
Synthetic & Proposed Methods.......................................................................................................................9
1. Synthesis of Cu(II)TMPyP4+ from H2TMPyP4+........................................................................................................................9
2. β-Chlorination of CuTMPyP4+ to yield CuTMPyPCl84+......................................................................................................10
3. Synthesis of NiTMPyP4+ from H2TMPyP4+............................................................................................................................13
4. Metathesis I: Synthesis of NiTMPyP4+ as Cl- salt.................................................................................................................14
5. β-Chlorination of NiTMPyP4+ as Cl- salt to yield NiTMPyPCl84+ using NCS...............................................................15
6. Metathesis II: Synthesis of NiTMPyP4+ as PF6- salt............................................................................................................16
7. β-Chlorination of NiTMPyP4+ as PF6- salt to yield NiTMPyPCl84+ using SOCl2.........................................................17
Results: Spectroscopic Observations........................................................................................................19
Discussion & Future Outlook.........................................................................................................................20
Acknowledgements............................................................................................................................................21
References...............................................................................................................................................................21

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ABSTRACT
Recent research conducted on manganese porphyrins (MnPs) has shown that these complexes have
a wide array of prospective medicinal applications that extend far beyond original assertions. To date,
however, only water-insoluble (i.e., non-employable in vivo) MnP derivatives have been synthesized. The
central challenge with synthesizing a stable water-soluble MnP derivative like MnTMPyPCl8
5+
, our target
molecule1
, is halogenation of the porphyrin’s eight β-carbons—full β-chlorination must occur before
insertion of the Mn2+
ion. Here, we describe attempts at β-chlorination of two pre-cursor metalloporphyrins,
Cu(II) and Ni(II) complexes, using three separate chlorinating agents—NCS, SOCl2, and Cl2 (g)—by
widely varying reaction conditions, with close monitoring of structural changes via ultraviolet-visible (UV-
Vis) absorption spectroscopy. The largest Soret-band (λmax) shifts were exhibited by the Ni(II) complex,
the most drastic of which occurred after refluxing NiTMPyP4+
(as PF6
-
salt) with SOCl2 (Δλmax = 26.5 nm)2
.
This result suggests that complete halogenation (i.e., λmax ≈ 456 nm) is likely feasible after few minor
reaction-system modifications. The Cu(II) complex, nor either metallo-complex when Cl2 and NCS were
employed as chlorinating agents, showed no significant Δλmax. Elemental analysis will be performed on the
Ni(II) compound to determine its actual degree of chlorination; accordingly, to elucidate the optimum
conditions under which full β-halogenation may be successfully achieved, future work will place concerted
efforts on experimental designs in which the Ni(II) complex is allowed to react with SOCl2 under several
varying conditions.
1 Structure of MnTMPyPCl85+ complex shown directly above and in Fig. 1 on page 6.
2 See Fig. 17 on page 18, Fig. 18-B on page 19, and Table 1 (Sample 21) on page 19.
MnTMPyPCl85+

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INTRODUCTION
Motivation. An extensive, diverse array of various porphyrin complexes have become increasingly
studied in recent years. One porphyrin class that has received a considerable amount of attention,
predominantly within the last decade, is the metalloporphyins—specifically, manganese porphyrins
(MnPs)—which are characterized by the presence of a metal ion bonded within their structural core.
Promising research has shown that MnPs likely have many medicinal applications, including: use in
treatments for certain diseases, such as diabetes[1]
and amyotrophic lateral sclerosis (ALS);[2]
use in
treatments for specific conditions, including hepatic ischemia;[3]
and as agents to improve the effectiveness
of some cancer treatments.[4]
Additionally, MnPs have been show to prolong the half-life of an ‘oxidation-
prone’ compound and have been patented for treating or preventing injury due to: exposure to a ‘reactive
species’, erectile dysfunction caused by surgery, lung disease, hyperoxia, myocardial damage during
cardioplegia, and cardiovascular disease.[5]
Moreover, a certain type of modified MnP, β-octa-brominated MnPs, that have been synthesized
in GCSU laboratories[6]
have been implicated in other research as mimics of superoxide dismutase[7]
, an
enzyme responsible for the removal of peroxide moieties (O2
2-
) from the body, thus preventing excessive
build-up of toxins. Although the properties of β-chlorinated MnPs appear to be similar to brominated
derivatives, the chloro- species has not been nearly as thoroughly investigated as potential treatments or
mimics;[8]
as such, we have initiated studies on both the synthesis and likely medicinal applications of β-
chlorinated MnPs.
Diabetes background. Diabetes, a disease associated with high levels of blood glucose resulting
from defects in insulin production, causes sugar to accumulate in the body excessively. It is the seventh
leading cause of death in the United States and can cause serious health complications, including: heart
disease, blindness, kidney failure, and lower-extremity amputations, among others. There are
approximately 24 million people in the U.S. alone, 8% of the current total population, who have been
diagnosed with diabetes at some point in their lives, an increase of more than 3 million individuals in
roughly only two years. Moreover, an estimated 57 million Americans have pre-diabetes, a condition in
which the earliest stages of diabetes have materialized.[9]
Diabetes medicinal implications. In an experiment conducted at Kuwait University in 2005,[1]
certain manganese porphyrin complexes were shown to decrease mortality rate and markedly extend the
life-span of diabetic rats. Specifically, the MnTMPyP5+
complex suppressed diabetes-induced oxidative
stress, which presumably accounts for its beneficial effect on the life-span of the diabetic rats. The results
seem to indicate that MnPs possess considerable potential to be used as potent therapeutic agents against
diabetes.

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ALS background. Although the recent increase in resources, funding, and time invested into
medicinal-related research and development has been quite substantial, a person diagnosed with ALS
(commonly referred to as Lou Gehrig’s disease) today essentially receives a death sentence. ALS is a
rapidly progressive, invariably fatal neurological disease that attacks the neurons responsible for controlling
voluntary muscles. The disease belongs to a group of disorders known as motor neuron diseases, which are
characterized by the steady degeneration and death of motor neurons. The disorder causes muscle weakness
and atrophy throughout the body as both the upper and lower motor neurons degenerate, gradually ceasing
to send messages to muscles. Unable to function, the muscles consistently weaken and develop contractions
because of denervation, leading to eventual atrophy; subsequently, the patient may, in due course, lose the
ability to initiate and control all voluntary movement, ultimately becoming permanently paralyzed.[10]
ALS medicinal implications. To date, no cure has been found for ALS. Indeed, the FDA approved
the first drug treatment, under the trade name Rilutek®
, for the disease in 1995.[11]
Yet, unfortunately,
Rilutek®
only prolongs the patient’s life-span for several months.[10]
During a 2005 study at the University
of Arkansas,[2]
certain MnPs were tested on mice that had a disease similar to that of ALS. These mice
underwent manganese porphyrin-therapy and lived three times longer than those in the control group—
thus, it is highly likely that these drugs will have some type of substantial effect on the human condition.
Hepatic ischemia background and medicinal implications. Hepatic ischemia is a condition in
which the liver does not receive enough blood or oxygen, causing injury to liver cells. It has been known
to cause liver failure, a critical, life-threatening condition, in many patients.[12]
In a 2007 study conducted
by Wu et al.,[3]
rats suffering from injuries leading to hepatic ischemia were treated with MnPs. The
researchers observed that, ultimately, the effects of the condition were lessened, allowing more oxygenated
blood to flow to the liver.
Cancer medicinal implications. During an experiment conducted at Duke University in 2005,[4]
rodents infected with tumors were exposed to MnTMPyP5+
in vitro and examined for viability and
radiosensitivity in a controlled environment. Additionally, tumors were exposed to simultaneous treatment
of both radiation and MnTMPyP5+
; the effects of tumor growth and vascularity were monitored, and the
two approaches were compared for overall effectiveness. In vitro, MnTMPyP5+
was not significantly
cytotoxic. However, combined treatment with radiation and in vivo injection of MnTMPyP5+
achieved
synergistic tumor devascularization, with a 78.7% reduction in vascular density observed within 72 hours
of radiotherapy. Moreover, co-treatment of tumors resulted in synergistic antitumor effects, extending the
delay of tumor growth by nine days. This study suggests that it is not unreasonable to investigate the
potential in vivo use of MnPs in humans as agents to enhance the responsiveness of cancerous tumors to
various radiation therapies.

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Research goal. The overarching aim of this project is to synthesize the β-chlorinated water-soluble
manganese(II) porphyrin complex MnTMPyPCl8
5+
, shown in Fig. 1 below, and to harness its medicinal
applications as a potential life-saving drug.
FIGURE 1: Chemical structure of the fully octa-chlorinated water-soluble metallo-complex of 4-N-
methylpyridylporphyrin, MnTMPyPCl85+, the target molecule. All chlorine atoms are bonded to the β-carbons
of the porphyrin ring (one such β position is indicated here with an arrow).
PORPHYRIN CHEMISTRY & PROBLEM
Significance. Our interest is in MnPs since porphyrins and their derivatives are currently being
explored for applications as drugs which could treat, help prevent, or even cure many life-threatening
conditions and diseases. Porphyrins are particularly great candidates for medicinal application because they
are ubiquitous to nature, forming the structural basis of both heme and chlorophyll (Fig. 2-A).[13]
Structurally, porphyrins are derived from the parent molecule porphine and are comprised of four
alternating pyrrole rings joined by four methine bridges at their alpha-carbons (α-carbons), which include:
C1, C4, C6, C9, C11, C16, and C19 (see Fig. 2-B).[13]
Porphyrin is different to porphine when various
groups are substituted for hydrogens on the outer beta-carbons (β-carbons), a phenomenon that can occur
any time after the actual porphyrin is synthesized. In Fig. 2-B, the β-carbons include: C2-3, C7-8, C12-13,
and C17-18. Metal ions can be substituted for the hydrogen atoms found within the porphyrin’s core to
form metalloporphyrins (see Fig. 2-A), a class of heterocyclic macrocycles that are highly conjugated and,
therefore deeply colored, which allows them to exhibit optimal spectra with very intense transitions at ~400
nm (known as Soret-bands). Similarly, most porphyrins exhibit several less-intense Q-bands in the visible
region at ~500-700 nm.[15]
MnTMPyPCl8
5+

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Predominant challenge. MnPs have the propensity to be life-saving molecules—the primary hope
is that medicine capable of treating humans can be derived from these complexes; however, the feasibility
of this goal is very much dependent upon the synthesized complexes being water-soluble. To date,
unfortunately, only water-insoluble complexes have been successfully synthesized—if these insoluble
complexes were to be used by humans as drugs, there would be a significant risk of the body rejecting them,
which would, in turn, cause even more health complications for an already vulnerable, weakened body.
Conversely, a water-soluble porphyrin would most likely easily be both absorbed and excreted by the body.
Problem statement. β-octa-chlorination of water-insoluble porphyrins has been demonstrated in
prior studies, but, to date, β-octa-chlorination of water-soluble porphyrins has yet to be reported.
FIGURE 2: (A) Chemical structure of chlorophyll (left) and heme (right). Note the magnesium (Mg2+) and iron
(Fe2+) ions within the core of the chlorophyll and heme metallo-complexes, respectively. (B) Chemical structure
of porphine, the parent molecule of all porphyrin complexes.
LITERATURE OVERVIEW & HYPOTHESIS
Literature background. For the challenge of chlorinating the porphyrin, our method of attack is
based on three separate studies, and, therefore, three different chlorinating agents: thionyl chloride (SOCl2),
N-chlorosuccinimide (NCS), and chlorine gas (Cl2).
In one study conducted in 2000, SOCl2 was used as the chlorinating agent for Pd, Ni, and Cu
metalloporphyrins.[8]
In these experiments, octa-chlorination occurred at the β-carbons of each
metalloporphyrin after each complex was refluxed in SOCl2 for various amounts of time. However, all of
the porphyrins used by Mironov et al.[8]
were insoluble in water, while our main goal is to synthesize a
stable water-soluble porphyrin. Still, there is a possibility that SOCl2 will prove to be successful at β-
chlorination while maintaining the solubility of the porphyrin; thus, SOCl2 will be investigated as one
potential chlorinating agent in our study.
BA

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In a separate study undertaken in 1990, NCS was used as a chlorinating agent for H2TPP analogues
under certain refluxing conditions.[16]
Octa-chlorination occurred after these porphyrin complexes were
refluxed in chloroform for different durations of time. Based on the success at β -chlorination in this study,
it is probable that NCS will successfully β-chlorinate Cu(II) and/or Ni(II) metalloporphyrins, and that the
complexes will remain both stable and water-soluble. Because of this likelihood, NCS will be explored as
a prospective chlorinating agent.
Finally, during a third study performed in 1995, an Fe(III)TPP complex underwent facile
perchlorination of its porphyrin ring when treated with Cl2 (g).[17]
It is likely that this technique can also be
used to octa-chlorinate a Cu(II) complex because of the high level of similarity in the properties of both
metal-ion complexes—accordingly, Cl2 (g) will be investigated as a possible chlorinating agent for Cu(II)
complexes. Moreover, as reported in the same aforementioned study,[17]
a Ni(II)TPP complex reacted with
10-12 equivalents of NCS to give Ni(II)TPPCl8 in 75% yield—based on these observations, it is highly
possible that NCS can be used to β-chlorinate a water-soluble Ni(II) complex, so this approach will be
explored as well.
Hypothesis statement. It is hypothesized that the synthesis of the β-octa-chlorinated derivative of
the water-soluble 4-N-methyl-pyridylporphyrin manganese complex, MnTMPyPCl8
5+
, can be successfully
undertaken by modifying the solvent conditions to enable solubility of both the porphyrin and chlorinating
agent. Any potential structural transformation(s) of the porphyrin will be monitored via UV-Visible
absorption spectroscopy.
REAGENTS & INSTRUMENTATION
The octa-chlorinated water-soluble manganese porphyrin complex, MnTMPyPCl8
5+
(see Figure
1), will be prepared via the synthesis of metallo-derivatives of meso-tetrakis(N-methyl-4-pyridyl)porphyrin,
or H2TMPyP4+
(see Fig. 3). Reaction progress will be monitored with UV-Vis absorption spectroscopy via
a Shimadzu UV-2401PC Ultraviolet-Visible Spectrophotometer (Shimadzu Corporation; Nakagyō-ku,
Kyoto, Japan).
The meso-tetrakis(N-methyl-4-pyridyl)porphyrin starting complex (H2TMPyP4+
) was purchased
directly from Frontier Scientific, Inc. (Logan, UT 84321, USA) and used without further purification.
Thionyl chloride (SOCl2); N-chlorosuccinimide (C4H4ClNO2); cupric(II) acetate (Cu(CH3COO)2);
nickel(II) sulfate heptahydrate (NiSO4·7H2O); sodium acetate (CH3COONa); tetra-n-butylammonium
chloride (TBAC; NBu4Cl); ammonium hexafluorophosphate (NH4PF6); methanol (CH3OH); acetone
(CH3COCH3); sulfuric acid (H2SO4); N, N-dimethylformamide ((CH3)2HCON); hydrochloric acid (HCl);

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sodium hypochlorite (NaClO); and acetonitrile (CH3CN) were all purchased directly from Sigma-Aldrich
Co. LLC (St. Louis, MO 63103, USA) and used without any further purification.
SYNTHETIC & PROPOSED METHODS
The attempted synthesis of the MnTMPyPCl8
5+
complex was approached using several different
synthetic steps, all of which are identified and described below.
1. Synthesis of Cu(II)TMPyP4+
from H2TMPyP4+
. A Cu2+
ion was inserted into into the core
of the H2TMPyP4+
complex by refluxing porphyrin (100 mg) with cupric acetate (50 mg) in
methanol (20 mL) and DI water (5 mL) for 4 h (Fig. 3); the reaction was subsequently monitored
by UV-Visible spectroscopy (Fig. 4).
FIGURE 3: Reaction mechanism of Cu2+ ion insertion into core of H2TMPyP4+ complex (left) to yield CuTMPyP4+
metalloporphyrin complex (right).

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FIGURE 4: UV-Vis spectrum acquired of H2TMPyP4+ (purple line) starting material (λmax = 422 nm in CH3OH; 4
Q-bands observed) overlaid with spectrum acquired of the synthesized CuTMPyP4+ (red line) metallo-complex
(λmax = 425 nm in CH3OH; 2 Q-bands observed).
Formation of the Cu(II) metallo-complex was necessary so that the four nitrogen atoms
within the core of the H2TMPyP4+
complex, all of which bonded with the Cu2+
ion, would be
protected from ensuing chlorination. Metallation of H2TMPyP4+
was evidenced by the observed
decrease in lower-energy Q-bands from four to two (see Fig. 4). The solvent was removed via
distillation, and the purple solid was collected, vacuum-dried, and used in subsequent syntheses
without any further purification.
2. β-Chlorination of CuTMPyP4+
to yield CuTMPyPCl8
4+
. N-chlorosuccinimide (NCS) and
chlorine gas (Cl2) were used as chlorinating agents for the Cu(II) complex. Two different methods
using NCS were chosen in our attempts to octa-chlorinate the water-soluble porphyrin complex: in
separate approaches, the variables of 1) temperature and 2) form of combination were manipulated.
a. β-Chlorination of CuTMPyP4+
using NCS. CuTMPyP4+
(5 mg) was added to N,
N-dimethylformamide (20 mL; DMF) containing NCS (5 mg). Before the porphyrin was
added, the solution was heated for no more than five minutes at which point the desired
temperature was reached. The CuTMPyP4+
was then added to the DMF containing the NCS
at both 80° (Fig. 5) and 90°C. The samples were allowed to react for 15 minutes, during
which time the solutions changed from dark-red in color to a dark greenish-yellow. The
reaction was monitored with UV-Visible spectroscopy (spectrum acquired of 80°C sample
shown in Fig. 7-A).

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Additionally, two separate combination-based experimental approaches, both of
which involved the exact same reagent amounts aforementioned in the preceding
paragraph, were undertaken: 1) reflux of CuTMPyP4+
and NCS in DMF for a total of 4 h,
and 2) vigorous stirring (with no heating) of porphyrin and NCS in DMF for the same
amount of time (Fig. 6). During both experimental approaches, a change in color of the
reaction mixture from dark-red to light-brown was observed after ~3 h of reaction time.
Again, the transformation of the complex was closely monitored by UV-Visible
spectroscopy (spectrum acquired of sample subjected to stirring shown in Fig. 7-B).
FIGURE 5: Reaction mechanism showing theoretical octa-chlorination of the CuTMPyP4+ complex (left) to yield
the hypothetical CuTMPyPCl84+ complex (right) via heat-based manipulations (i.e., significant temperature
increases) to the system.
FIGURE 6: Reaction mechanism showing theoretical octa-chlorination of CuTMPyP4+ complex (left) to yield the
hypothetical CuTMPyPCl84+ complex (right) via manipulation of the amount (i.e., intensity) of induced
perturbation (i.e., forceful stirring at relatively high speed) to the system.

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FIGURE 7: (A) UV-Vis spectrum obtained after CuTMPyP4+ complex reacted with previously-heated (80°C) NCS
in DMF for 15 min (λmax = 435 nm in DMF; 2 Q-bands observed; dark green-yellow color observed post
reaction). (B) UV-Vis spectrum obtained after CuTMPyP4+ complex and NCS vigorously stirred in DMF for 4 h,
with no added heat (λmax = 431.5 nm in DMF; 1 Q-band observed; light-brown color observed post reaction).
b. β-Chlorination of CuTMPyP4+
using Cl2. Chlorine gas, which was generated by
reacting hydrochloric acid (HCl) with sodium hypochlorite (NaClO), was also employed
as a chlorinating agent for the Cu(II) complex (Fig. 8). Contact with Cl2 induced an
immediate color change in the CuTMPyP4+
solution (in CH3OH), which changed from a
light-red color to a dark blackish-brown color. The reaction was allowed to take place for
no more than 5 s, and it was monitored using UV-Visible spectroscopy (Fig. 9).
FIGURE 8: Reaction mechanism showing theoretical octa-chlorination of CuTMPyP4+ complex (left) to yield the
hypothetical CuTMPyPCl84+ complex (right) via subjection to Cl2 (g) for a duration of 5 s.
A B

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FIGURE 9: UV-Vis spectrum of the (theoretically) chlorinated CuTMPyPCl84+ complex acquired after 5 s contact
with Cl2 (g). Two Q-bands, labeled 1 and 2 (located at 543 and 629 nm, respectively) were observed (λmax = 428
nm in CH3OH).
3. Synthesis of NiTMPyP4+
from H2TMPyP4+
. After failed octa-chlorination of the
CuTMPyP4+
complex, a Ni(II) complex was synthesized using the same starting material and
methods. A Ni2+
ion was inserted into H2TMPyP4+
by reflux of porphyrin (200 mg) with nickel(II)
sulfate heptahydrate (100 mg) and sodium acetate (50 mg) in DMF (50 mL) for 3 h (see Fig. 10).
The reaction was subsequently monitored by UV-Vis absorption spectroscopy (Fig. 11).
FIGURE 10: Reaction mechanism of Ni2+ ion insertion into core of H2TMPyP4+ complex (left) to form NiTMPyP4+
metalloporphyrin complex (right).
2
1

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FIGURE 11: Overlaid UV-Vis spectra acquired of H2TMPyP4+ (red line) starting material (λmax = 422 nm in
CH3OH; 4 Q-bands observed) and the synthesized NiTMPyP4+ (black line) metallo-complex (λmax = 420.5 nm in
DMF; 2 Q-bands observed).
Formation of the Ni(II) complex was necessary to protect the nitrogen atoms in the core of
the porphyrin complex from ensuing chlorination. Metallation of H2TMPyP4+
was evidenced by
the replacement of four lower energy Q-bands by two. After cooling, the solvent was removed via
distillation. The black solid was then collected and vacuum-dried, and it used in subsequent
syntheses without any further purification.
4. Metathesis I: Synthesis of NiTMPyP4+
as Cl-
salt. Solubility testing of the Ni(II) complex
was performed using several different solvents, including: acetone, acetonitrile, methanol, and DI
water. Test results indicated that the Ni(II) porphyrin complex was completely insoluble in acetone
and acetonitrile while being moderately soluble in both methanol and DI water. Consequentially, a
metathesis on the NiTMPyP4+
complex was performed to increase its overall solubility, with the
goal of synthesizing a fully water-soluble, stable complex (Fig. 12). Tetra-n-butylammonium
chloride (30 mg), or TBAC, was added to DMF (20 mL) containing the Ni(II) complex (30 mg).
Upon addition of the TBAC, a black solid precipitated out of the solution, which was subsequently
collected via suction filtration and allowed to air dry.

15
FIGURE 12: Illustration of Cl- salt metathesis performed on NiTMPyP4+ complex using TBAC (Cl- salt addition
indicated in enlarged circle as ‘X’).
5. β-Chlorination of NiTMPyP4+
as Cl-
salt to yield NiTMPyPCl8
4+
using NCS. Two
different methods using NCS were chosen in our attempts to octa-chlorinate the Ni(II) porphyrin
complex. One approach involved manipulations with both stirring and heating, and the other
approach employed reflux techniques.
The Ni(II) complex as the chloride salt (5 mg; see Figure 12) and NCS (5 mg) were added
to methanol (10 mL), and the solution was simultaneously heated to a boil and stirred (Fig. 13). As
it boiled, the solution turned from a dark-brown to a dark greenish-yellow color. In less than 10
min, the solution had completely evaporated, leaving only a thin layer of a black jelly-like substance
that was stuck to the bottom of the vial. Methanol (10 mL) was poured onto the black substance,
and the liquid immediately turned brown. A sample was taken and monitored by UV-Visible
spectroscopy (Fig. 14-A).
Additionally, the Ni(II) complex (10 mg) as the chloride salt (see Fig. 12) and NCS (10
mg) were added to methanol (20 mL), and the solution was allowed to reflux for 1 h. The solution
changed from a dark-brown color to a deep yellow color. Structural transformation was monitored
by UV-Vis spectroscopy (Fig. 14-B).

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FIGURE 13: Reaction mechanism showing theoretical octa-chlorination (using NCS) of the NiTMPyP4+ complex
as the Cl- salt (left) to hypothetically yield the CuTMPyPCl84+ complex (right) via stirring/heating manipulations
(i.e., significant temperature increases) to the system.
FIGURE 14: (A) Spectrum obtained after NiTMPyP4+ complex as Cl- salt and NCS stirred/heated in CH3OH for
< 10 min until complete CH3OH evaporation (λmax = 441.5 nm in CH3OH; 3 Q-bands observed; brown color
observed post reaction). (B) Spectrum obtained after NiTMPyP4+ complex and NCS refluxed in CH3OH for 1 h
(λmax = 419 nm in CH3OH; no Q-bands observed; dark yellow color observed post reaction).
6. Metathesis II: Synthesis of NiTMPyP4+
as PF6
-
salt. A second metathesis was performed
because β-chlorination of the Ni(II) complex as the chloride salt was unsuccessful. Here, instead
of Cl-
(Fig. 15), the tosylate salt was replaced with PF6
-
via ammonium hexafluorophosphate
(NH4PF6). NH4PF6 (30 mg) was added to H2O (20 mL) containing the Ni(II) porphyrin (30 mg).
Upon addition of NH4PF6, a black solid precipitated out of the solution, which was later collected
via suction filtration and allowed to air dry.
A B

17
FIGURE 15: Illustration of PF6- salt metathesis performed on NiTMPyP4+ complex using NH4PF6 (PF6- salt
addition indicated in enlarged circle as ‘X’).
7. β-Chlorination of NiTMPyP4+
as PF6
-
salt to yield NiTMPyPCl8
4+
using SOCl2. Two
different methods using thionyl chloride (SOCl2) as the chlorinating agent were employed in
attempt to octa-chlorinate the Ni(II) complex. First, the Ni(II) complex as the PF6
-
salt (10 mg) was
added to stirring SOCl2 (20 mL), and heat was applied (Fig. 16)—almost instantaneously, the
solution turned dark brownish-green in color. The reaction was stopped when the temperature of
the system reached 75°C. Transformation was monitored by UV-Vis spectroscopy (Fig. 18-A).
Second, the Ni(II) complex as the PF6
-
salt (10 mg) was refluxed in SOCl2 (20 mL) for 2 h
before being stopped (Fig. 17); a color change from a light-brown color to a very deep greenish-
brown color was observed post reaction. The extent of the reaction was monitored using UV-
Visible spectroscopy (Fig. 18-B).

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FIGURE 16: Reaction mechanism showing theoretical octa-chlorination (using SOCl2) of the NiTMPyP4+
complex as the PF6- salt (left) to hypothetically yield the CuTMPyPCl84+ complex (right) via stirring/heating
manipulations (i.e., significant temperature increases) to the system.
FIGURE 17: Reaction mechanism showing theoretical octa-chlorination (using SOCl2) of the NiTMPyP4+
complex as the PF6- salt (left) to hypothetically yield the CuTMPyPCl84+ complex (right) by reflux.

19
FIGURE 18: (A) Spectrum obtained after NiTMPyP4+ complex as PF6- salt and SOCl2 stirred and heated to 75°C
(λmax = 446.5 nm in SOCl2; 3 Q-bands observed; brown color observed post reaction). (B) Spectrum obtained
after NiTMPyP4+ complex as PF6- salt refluxed in SOCl2 for 2 h (λmax = 447.5 nm in SOCl2; 2 Q-bands observed;
dark green-brown color observed post reaction).
RESULTS: SPECTROSCOPIC OBSERVATIONS
TABLE 1: Soret-band positions exhibited by significant spectra of various porphyrin complexes studied both
in this study and in previous experiments. All data obtained from previous work is in bolded rows (i.e., Samples
11-14, 22-23), and specific literature references are given in the λmax column. All spectroscopic data reported
here was acquired via ultraviolet-visible absorption spectroscopy.
Sample Solvent Porphyrin Species Reaction Conditions λmax (nm)
1 H2O H2TMPyP4+ -- 422
2 CH3OH
CuTMPyP4+
H2TMPyP4+ reflux w/ Cu(CH3COO)2, 4 h 425
3
DMF
Reflux w/ NCS, 4 h 422.5
4 Heated w/ NCS, 90°C, 15 min 423.5
5 Reflux w/ NCS, 2 h 425
6 Heated/stirred w/ NCS, 80°C, 1 h 425.5
7 Heated/stirred w/ NCS, 80°C, 2 h 426
8 CH3OH Contact w/ Cl2 (g), 5 s 428
9
DMF
Heated/stirred w/ NCS, 90°C, 1 h 431.5
10 Heated w/ NCS, 80°C, 15 min 435
11 C7H14 ZnTF5PPCl8 Cl2 (g) 442[10]
12 SOCl2 Cu(TPPs)Cl8 Reflux, 1 h 463-69[8]
13 CH2Cl2 CuTPPCl8 NCS 456[9]
14 CH3CN CuTMPyPBr8
4+ Contact w/ Br2 in DMF at RT 456[6]
15 DMF NiTMPyP4+ H2TMPyP4+ reflux w/ NiSO4, 4 h 420.5
16
CH3OH
NiTMPyP4+
(Cl- salt)
Heated/stirred w/ NCS, 140°C, 15 min 418.5
17 Reflux w/ NCS, 1 h 419
18 Heated/stirred w/ NCS to evap. 441.5
19
SOCl2
NiTMPyP4+
(PF6
- salt)
Heated/stirred, 55°C 439.5
20 Heated/stirred, 70°C 446.5
21 Reflux, 2 h 447.5
22 CH2Cl2 NiTPPCl8 Cl2 (g) 449[9]
23 DMF NiTMPyPBr84+ Contact w/ Br2 in DMF at RT 446[6]
A B

20
DISCUSSION & FUTURE OUTLOOK
The results of the initial experiments suggest that our attempts at β-chlorination using the Cu(II)
complex with NCS and Cl2 as chlorinating agents were not particularly successful. According to previous
studies[8], [15]
, when using NCS to octa-chlorinate a Cu(II) complex, the ideal position of the Soret-band is
in the range of 463-469 nm. The most successful experiment conducted using the Cu(II) complex was
heating the porphyrin with NCS to 80°C, resulting in an observed Soret-shift of 10 nm, from 425 to 435
nm (see Table 1, Sample 10); still, despite this approach yielding the most promising result, the Soret-band
was 28 nm away from the optimal position, a discrepancy considered to be too large to suggest that full
octa-chlorination of the Cu(II) complex was achieved.
Alternatively, the Ni(II) complex, with SOCl2 employed as its chlorinating agent, proved to be
much more successful at attaining β-chlorination of the porphyrin ring. When the NiTMPyP4+
complex (as
PF6
-
salt) was refluxed with SOCl2, a Soret-shift from 421 to 447.5 nm was observed (see Table 1, Sample
21). According to previous studies, Ni(II) complexes that have been fully octa-chlorinated via SOCl2 should
exhibit a Soret-band around 456 nm—our porphyrin sample demonstrated a Soret-band that was a mere 8.5
nm away from said optimum position. Still, however, our porphyrin must undergo further analysis to
determine its exact degree of chlorination. Nonetheless, indeed, although much more work is needed, these
preliminary results appear to support our hypothesis.
At the conclusion of our study, Ni(II)TMPyP4+
remains synthesized. The complex has been
partially chlorinated, but a full octa-chlorination has yet to take place; future work will focus on experiments
with Ni(II) water-soluble complexes. Investigations into alternate techniques that could potentially be
executed to achieve full β-chlorination of the porphyrin ring have been initiated. One such approach
involves the use of an insoluble porphyrin (i.e., H2TPyP) as the starting material, with subsequent solubility
modifications via a methylating agent, such as methyl triflate (C2H3F3O3S).
Regardless of the manner in which it is accomplished, successful octa-chlorination of the porphyrin
would be consequently followed with the replacement of the Ni2+
ion in the core of the NiTMPyP4+
complex
with a Mn2+
ion, a two-step procedure consisting of: 1) demetallation of the porphyrin via a strong acid
(i.e., H2SO4), yielding H2TMPyPCl8
5+
; and 2) insertion of the Mn2+
ion into the core of the complex via
reflux with manganese chloride (MnCl2), as per the methods laid out by Richards et al.[6]

21
ACKNOWLEDGEMENTS
First and foremost, I thank the American Chemical Society for giving me the opportunity and
privilege to participate in its Project SEED Program, which, ultimately, was an invaluable, life-changing
experience, not just intellectually and professionally, but also emotionally and personally, as an individual.
I also thank my family, namely my mother, Shannon, and friends for their endless, unwavering support
throughout the entirety of this project; I send an abundance of my love and sincere wishes of well-being to
each and every one of you—may you each experience the best possible outcome in each and every one of
your future endeavors.
I also thank two of my collaborators and fellow Project SEED participants, Mr. Jah-Wann M.
Galimore and Mr. Alvin P. Huff, for their countless contributions to this project, all of which are highly
valued and held to the highest esteem. I have the utmost respect for each of you, both as professional
colleagues and personal friends—with the high-quality character that you each possess, I am certain that
both of you will find much happiness and success in life, of which you deserve nothing less.
Additionally, I extend much gratitude not only to the GCSU Dept. of Chemistry, Physics, &
Astronomy for allowing me to use its facilities and supplies located in Herty Hall, but to the entire team of
faculty and staff members who comprise the department and make its existence possible.
And, finally, I express legitimately endless gratitude to my mentor and genuine friend, Dr. Rosalie
A. Richards, for her guidance, instruction, understanding, support, and for being there for me every step of
the way, in both professional and personal purposes alike, as I continue to navigate what is simply referred
to as life.
REFERENCES
[1] Benov, L.; Batinic-Haberle, I. A Manganese Porphyrin Suppresses Oxidative Stress and
Extends the Life Span of Streptozotocin-Diabetic Rats. Free Radic. Res. 2005, 39, 81-88.
[2] Crow, J. P.; Calingasan, N. Y.; Chen, J.; Hill, J. L.; Beal, M. F. Manganese Porphyrin Given at
Symptom Onset Markedly Extends Survival of ALS Mice. Ann. Neurol. 2005, 58, 258-265.
[3] Wu, T. J.; Khoo, N. H.; Zhou, F.; Day, B. J.; Parks, D. A. Decreased Hepatic Ischemia-
Reperfusion Injury by Manganese-Porphyrin Complexes. Free Radic. Res. 2007, 41, 127-134.
[4] Moeller, B. J.; Batinic-Haberle, I.; Spasojevic, I.; Rabbani, Z. N.; Anscher, M. S.; Vujaskovic,
Z.; Dewhirst, M. W. A Manganese Porphyrin Superoxide Dismutase Mimetic Enhances Tumor
Radioresponsiveness. Int. J. Radiat. Oncol. Biol. Phys. 2005, 63, 545-552.

22
[5] Williams, W.; Southan, G.; Szabo, C. Pyridyl-substituted porphyrin compounds and methods of
use thereof. U.S. Patent 7,432,369, October 7, 2008. Unites States Patent and Trademark Office
Website. http://patft.uspto.gov/netacgi/nph-
Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=/netahtml/PTO/search-
bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN/7432369 (accessed 5 July
2009).
[6] Richards, R. A.; Hammons, K.; Joe, M.; Miskelly, G. M. Observation of a Stable Water-
Soluble Lithium Porphyrin. J. Inorg. Chem. 1996, 35, 1940-1944.
[7] Batinic-Haberle, I.; Liochev, S. I.; Spasojevic, I.; Fridovich, I. A Potent Superoxide Dismutase
Mimic: Manganese β-Octabromo-meso-tetrakis-(N-methylpyridinium- 4-yl) Porphyrin. Arch.
Biochem. Biophys. 1997, 343, 225-333.
[8] Rumyantseva, V. D.; Aksenova, E. A.; Ponamoreva, O. N.; Mironov, A. F. Halogenation of
Metalloporphyrins. Russ. J. Bioorg. Chem. 2000, 26, 423-428.
[9] Centers for Disease Control and Prevention. Number of People with Diabetes Increases to 24
Million. http://www.cdc.gov/media/pressrel/2008/r080624.htm (accessed 5 July 2009).
[10] The ALS Association. About ALS. http://www.alsa.org/als/default.cfm (accessed 4 July 2009).
[11] ALS Worldwide. Rilutek (riluzole). http://alsworldwide.org/research-and-trials/article/rilutek-
riluzole (accessed 24 March 2016).
[12] Lehrer, J. K. Hepatic Ischemia. http://www.nlm.nih.gov/medlineplus/ency/article/000214.htm
(accessed 6 July 2009), Medline Plus via the U.S. National Library of Medicine.
[13] Adler, A. D.; Longo, F. R.; Shergalis, W. Mechanistic Investigations of Porphyrin Syntheses. I.
Preliminary Studies on meso-Tetraphenylporphin. J. Am. Chem. Soc. 1964, 86, 3145-3149.
[14] Blusch, L. K. The Siamese-Twin Porphyrin and Its Copper and Nickel Complexes: A Non-
Innocent Twist; Springer International: Cham, Switzerland, 2013; pp 1-22.
[15] Corwin, A. H.; Chivvis, A. B.; Poor, R. W.; Whitten, D. G.; Baker, E. W. The Interpretation of
Porphyrin and Metalloporphyrin Spectra. J. Am. Chem. Soc. 1968, 90, 6577-6583.
[16] Wijesekera, T.; Matsumoto, A.; Dolphin, D.; Lexa, D. Perchlorinated and Highly Chlorinated
meso-Tetraphenylporphyrins. Angew. Chem. Int. Ed. Engl. 1990, 102, 1073.
[17] Birnbaum, E. R.; Schaefer, W. P.; Labinger, J. A.; Bercaw, J. E.; Gray, H. B. Electronic
Structures of Halogentated Ruthenium Porphyrins. Crystal Structure of RuTFPPCl8(CO)H2O
(TFPPCl8 = Octa-β-chlorotetrakis(pentafluorophenyl)porphyrin). J. Inorg. Chem. 1995, 34,
1751-1755.

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