Page 1
N N
HC
HC
NCH HC N
CH
HC
Fe
N
HC
CH
N
CH
Fe
Fe
NHC
NCH
CH
N
N
NN
N
N
NN
O O
O
O
OO
O
O
Structural Characterization and Electronic Properties of a Cyclic
Non-heme-iron-dinitrosyl Complex: [Fe(NO)2Imidazole]4
Structural Characterization and Electronic Properties of a Cyclic
Non-heme-iron-dinitrosyl Complex: [Fe(NO)2Imidazole]4
Eric Sundberg and Lijuan Li
California State University, Long Beach
Eric Sundberg and Lijuan Li
California State University, Long Beach
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Nitric Oxide ChemistryNitric Oxide Chemistry• 30 Years ago:
– A major contributor to smog– An ingredient in cigarette smoke and automobile exhaust – A suspected carcinogen– An ozone depleting agent– Toxic, noxious chemical
Koshland, D. E., Jr. Science 1992, 258, 1861-1902
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Nitric Oxide ChemistryNitric Oxide Chemistry
• In 1992, it was named the “Molecule of the Year” by the journal Science in an article titled, “NO News is Good News”
• In 1998 three gentlemen were awarded the nobel prize in medicine and physiology for their work involving the biological aspects of nitric oxide
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Nitric Oxide ChemistryNitric Oxide Chemistry
Furchgott Ignarro MuradDiscovered that nitric oxide works as a signaling
molecule in the cardiovascular systemDiscovered that nitric oxide works as a signaling
molecule in the cardiovascular system
http://www.nobel.se/medicine/laureates/1998/index.html
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Nitric Oxide ChemistryNitric Oxide Chemistry
• Maintains blood Maintains blood pressure by dilating pressure by dilating blood vesselsblood vessels
• Kills foreign invadersKills foreign invaders• Involved in Involved in
neurotransmissionneurotransmission
• Maintains blood Maintains blood pressure by dilating pressure by dilating blood vesselsblood vessels
• Kills foreign invadersKills foreign invaders• Involved in Involved in
neurotransmissionneurotransmission
• Involved in learning Involved in learning and memory processesand memory processes
• Controls platelet Controls platelet aggregationaggregation
• Stimulates penile Stimulates penile erectionserections
• Involved in learning Involved in learning and memory processesand memory processes
• Controls platelet Controls platelet aggregationaggregation
• Stimulates penile Stimulates penile erectionserections
Numerous Physiological Functions
Feldman, P. L.; Griffith, O. W.; Stuehr, D. J. Chem Eng. News 1993, 71 (Dec), 26-38
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Heme Versus Non-hemeHeme Versus Non-heme• Nitrosyl (NO) on a
hemoglobin molecule• Nitrosyl attached to a
non-heme molecule• Nitrosyl attached to a
non-heme molecule
Fe
N
N
N
N
CH3
CH3CH3
CH3
COOH COOH
NO
Fe
NO
Fe
NO
NO
L
L
+ NO
Muller, B.; kleschyov, A. L.; Stoclet, J. C. Br. J. Pharm. 1996, 119, 1281-1285
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Density Functional Theory
Stability UV-vis
Electrochemistry
EPR and NMR
ClassificationSynthesis
OutlineOutlineNon-heme iron Dinitroyls
Characterization
FT-IR X-ray Crystallography
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SynthesisSynthesis
Fe(CO)2(NO)2 + C3H4N2
C
NN
C
O
Fe
O
O O
Starting Material:Dicarbonyldinitrosyliron(0)
N
NH
Ligand: Imidazole
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SynthesisSynthesis• After 2 Hours: • After 24 Hours:
N
HN
N N
O O
Fe
C
O
N N
HC
HC
NCH HC N
CH
HC
Fe
N
HC
CH
N
CH
Fe
Fe
NHC
NCH
CH
N
N
NN
N
N
NN
O O
O
O
OO
O
O
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1757.5
7
1806.8
3
2031.6
9
2088.0
1Fe(CO)2(NO)2
60
80
100
%T
1686.6
3
1731.0
1
1982.5
0
Fe(CO)(NO)2(Im)
20
40
60
80
%T
1725.9
5
1796.7
8
Fe(NO)2(Im)2
10
15
20
%T
1600 1800 2000 2200 2400 2600
Wavenumbers (cm-1)
CharacterizationCharacterization
N
HN
N N
O O
Fe
C
O
C
NN
C
O
Fe
O
O O
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CharacterizationCharacterization
• X-ray Crystallography shows a cyclic compound with an acetone molecule trapped inside
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Materials and MethodsMaterials and Methods
• Recrystallized [Fe(NO)2Im]4
• Nuclear Magnetic Resonance– Dissolved 50mg of sample into 2 mls of deuterated
THF and transferred to a NMR tube
– AC200 Spectrometer
• Electron Paramagnetic Resonance– Dissolved 2 mg of sample into degassed 1 ml of THF
and transferred to EPR tube
– Brooker EMX Model EPR Spectrometer
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Materials and MethodsMaterials and Methods• Electrochemistry
– 3 electrode system with a gold working electrode
– THF was used as the solvent– Scan Rate of 100 mV sec-1
– 10mM [Fe(NO)2(Imidazole)]4 solution and a 0.1M electrolyte solution, (tetrabutylammonium perchlorate)
– Computer Controlled Electrochemical Analyzer
Autolab Electrochemical Insturments
http://www.ecochemie.nl/
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Materials and MethodsMaterials and Methods
• UV-vis Spectroscopy– Varian 300 Bio UV-vis spectrophotometer– Dilution Series in THF: 0.1-0.8 mM
Cary Uv-vis Spectrometer
www.varianinc.com
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Materials and MethodsMaterials and Methods
• Stability– FT-IR spectroscopy (Nicholet 380
Spectrometer) – 0.2mM in THF at 15 and 30 minutes
• Spin Density Functional Theory– Performed using X-ray crystallographic
coordinates– Dr. Fu-Ming Tao at Cal. State Univ. Fullerton
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Nuclear Magnetic ResonanceNuclear Magnetic Resonance
ppm9.0 01.02.03.04.05.06.07.08.0
1H NMR
(H1)
(H2&H3)
H2&H3
H1
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Nuclear Magnetic ResonanceNuclear Magnetic Resonance
306090120150180210240
ppm
13C NMR
C2&C3
C1
C1
C2&C3
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Electron Paramagnetic ResonanceElectron Paramagnetic ResonanceElectron Paramagnetic ResonanceElectron Paramagnetic Resonance
g=2.03
20G
Hyperfine Structure
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ElectrochemistryElectrochemistry
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UV-vis SpectroscopyUV-vis Spectroscopy
MLCT
d-d transitions
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Stability under Oxygen
1725.9
5
1796.7
8
Fe(NO)2(Im)2
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
%T
ransm
ittance
1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400
Wavenumbers (cm-1)
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Spin Density Functional Calculations
• Will provide wavefunction analysis of the molecule = a + b + c…– A diagram of the electron density on the
molecule
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1757.5
7
1806.8
3
2031.6
9
2088.0
1Fe(CO)2(NO)2
60
80
100
%T
1686.6
3
1731.0
1
1982.5
0
Fe(CO)(NO)2(Im)
20
40
60
80
%T
1725.9
5
1796.7
8
Fe(NO)2(Im)2
10
15
20
%T
1600 1800 2000 2200 2400 2600
Wavenumbers (cm-1)
Spin Density Functional Calculations
N
HN
N N
O O
Fe
C
O
C
NN
C
O
Fe
O
O O
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Spin Density Functional CalculationsSpin Density Functional Calculations
Fe ON:NNH
:
:NN
: N OFe +
Fe
Single- Substituted Product
Cyclic Product
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ConclusionConclusion• [Fe(NO)2Im]4 has been characterized by
– X-ray Crystallography and FT-IR Spectroscopy– NMR and EPR techniques
• Electrochemistry showed 2 chemically reversible reductions
• UV-vis spectroscopy showed MLCT and d-d orbital transitions
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ConclusionConclusion
• Low stability of compound in solution when exposed to oxygen
• Spin Density Functional Theory showed excess electronic density on the imidazole
• Potential Medicinal Applications
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Future StudiesFuture Studies
• Mass spectrometry
• Elemental analysis
• NMR studies of decomposed sample
• Laser flash photolysis
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AcknowledgementsAcknowledgements
• Dr. Lijuan Li
• Dr. Ximeng Wang
• The Beckman Scholars Foundation
• Howard Huges Medical Institute