Transcript Document

The Coordination Chemistry of Bismuth(III)
Complexes and Other Heavy Metals with Biorelevant
Ligands
March 27, 2005
Melanie Eelman
Overview
• Medicinal relevance of bismuth chemistry
• Pepto-Bismol
• De-Nol
• Use of thiolate anchors on hetero-bifunctional
ligands
• Study interactions of bismuth with “weak”
donors
• Use of electrospray ionization mass
spectrometry (ESI-MS)
• Identify metal-ligand complexes
• Characterization of interactions between
bismuth and other heavy metals (e.g. lead,
arsenic) and key biomolecules
Bismuth: 250 Years of Medicinal Use
Bismuth(III) Salts:
• nitrate
• oxide
• salicylate
• citrate
• tartrate
• malate
• oxalate
• lactate
Treatments for:
• syphilis
• bacterial infections
• colitis
• cancer
• hypertension
• diarrhea
• dyspepsia
• gastric/duodenal ulcers
P.J. Sadler, H. Li, H. Sun, Coord. Chem. Rev., 1999, 185-186, 689
G.G. Briand, N. Burford, Chem. Rev., 1999, 99, 2601.
Bismuth Pharmaceutical Agents
Colloidal Bismuth Subcitrate
(CBS)
O
O
O
K
O
O
O
Bi
Bi
O
O
O
Active Ingredient of
De-Nol
O
O
K
O
O
O
Herrmann, Inorg. Chem., 1991, 30, 2579; Asato, Inorg. Chem., 1991, 30, 4210; Herrmann, Z. Kristallogr.,
1992, 198, 25; Asato, Chem. Lett, 1992, 1967; Asato, Inorg. Chem., 1993, 32, 5322; Asato, Inorg. Chem.,
1995, 34, 2447; Sadler, Dalton Trans., 1996, 2417
Bismuth Subsalicylate
(BSS)
O
O
N
OH
Bi
O
Active Ingredient of
Pepto-Bismol
O
N
O
Bi
O O
O O
O
O
O
Bi
O
N
OH
N
OH
Dimeric in the solid state
J.H. Thurston, E.M. Marlier, K.H. Whitmire, Chem. Commun.,
2002, 2834.
Developing the Coordination
Chemistry of Bismuth
• Mechanisms of bioactivity of bismuth is
unknown
• Chemistry of bismuth is ill-defined
• Low solubility (i.e. BSS)
• Facile hydrolysis of Bi-element bonds
Objective:
Development of synthetic approaches to
systematic series of bismuth compounds and
definitive characterisation
Bismuth is thiophilic
 Use of ligands containing sulfur
Thiophilicity
Preference for certain atoms (heavy metals) to form
strong bonds with sulfur
Explained by: hard-soft acid-base theory
LUMO
LUMO
HOMO
HOMO
A
A-B
B
Cl
Na
Hard
R. G. Pearson, J.Am.Chem.Soc. 1963, 85 , 3533
A
A-B
Bi3
B
-SR
Soft
Dithiolate Ligands
Comprehensive characterization of a series of bismuth-dithiolate compounds:
Cl
HS
n
Bi
Cl
SH
Cl
Cl
Cl
Bi
Bi
Bi
S
S
S
S
S
Cl
Cl
S
Bi
S
Cl
S
S
Bi S
O
S
S
X
2
3 HS
S
X
Bi
S
Bi
Bi
X
SH
S
S
S
X
S
2
Bi
S
+
S
S
HS
S
Bi
S
S
S
SH
S
S
S
S
Bi
S
P. Powell, J.Chem.Soc.(A) 1968, 2587.
L. Agocs, N. Burford, T. S. Cameron, J. M. Curtis,
J. F. Richardson, K. N. Robertson, G.B. Yhard
JACS 1996, 126, 895.
Thiolate Anchored Hetero-Bifunctional Ligands
Investigate interactions of “weak” donors (E) with bismuth
Cl
S
KS
Bi
S
S
E
Bi
S
E
E = OH
S
E = NMe2
E = OH, NMe2
E = C(O)OMe
E = NH2
Cl
S
Bi
S
S
S
KS
E
S
E
Bi
S
S
E = NH2, C(O)OR
L. Agocs, G.G. Briand, N. Burford, M.D. Eelman, N. Aumeerally, D. MacKay, K.N. Robertson, T.S. Cameron, Can.
J. Chem., 2003, 81, 632.
Hetero-Bifunctional Thiolate Ligands
S
S
E
Bi
Cl
Cl
E
Cl
Bi
S
E
S
E
E
Bi
S
S
E
E = NR2
E = OH
E is a "weak" donor
OR
S
O
Bi
Cl
Can correlate isolated
complexes to those identified
using ESI-MS
Cl
OR
O
Cl
OR
RO
S
Bi
S
O
RO
S
O
O
Bi
S
S
O
RO
E = C(O)OR; ester functional group
R = Me, Et
L. Agocs, G.G. Briand, N. Burford, T.S. Cameron, W. Kwiatkowski, K.N. Robertson Inorg. Chem. 1997, 36, 2855.
G.G. Briand, N. Burford, T.S. Cameron, W. Kwiatkowski, J.Am.Chem.Soc. 1998, 120, 11374.
G.G. Briand, N. Burford, M.D. Eelman, T.S. Cameron, K.N. Robertson Inorg. Chem. 2003, 42, 3136.
The Importance of Electrospray Ionization
Mass Spectrometry ‘ESI-MS’
• Bismuth compounds hard to characterize
• NMR
• EI-MS
• Advantages of ESI-MS
• Dilute solutions
• Can handle ill-defined reaction mixtures: “in situ ESI-MS”
• Intact metal-ligand complexes
Electrospray Ionization (ESI)
Desolvation
Produces gaseous ionized
molecules from a liquid
solution by creating a spray of
droplets in the presence of a
strong electric field
Needle
Liquid
Flow
+ ++- - + - - + -+
+++
Taylor Cone
-+
-++ - +
-+
-++ - +
Coulombic
Explosion
Spray Shield
+ +
+
- +
-
- +
-
-
+
Capillary
+
+ Desolvated
Ions
End Plate
Synthesis of the Mono(Ester-Thiolate)
Complex of Bismuth
OEt
OMe
BiCl3 +
S
Absolute EtOH
HS
O
+ HCl
Bi
O
Cl
methyl thioglycolate (MTG)
Cl
25% Yield
Transesterification occurring:
OEt
OMe
S
O
S
+ EtOH
Bi
Cl
Cl
O
+ MeOH
Bi
Cl
Cl
Acid catalyzed and driven to completion by
the use of excess ethanol
G.G. Briand, N. Burford, M.D. Eelman, T.S. Cameron, K.N. Robertson Inorg. Chem. 2003, 42, 3136.
ESI-MS of BiCl3 and MTG in Absolute Ethanol
OR
O
S
S
OR
Bi
O
OR
OR
R = Et
R = Et
R = Et
O
S
O
Na
S
S
RO
Bi
Na
S
Bi
O
O
S
O
Cl
OR
OR
RO
OR
O
OR
S
O
S
S
Bi
O
O
Bi
S
Cl
R = Et
OR
Peak assignments confirmed by MS/MS
G.G. Briand, N. Burford, M.D. Eelman, T.S. Cameron, K.N. Robertson Inorg. Chem. 2003, 42, 3136.
Bis(Methylester-Thiolato) Bismuth Complex
OMe
OMe
BiCl3 + 2
HS
95% EtOH
O
O
S
Bi
methyl thioglycolate (MTG)
O
Cl
OR
+ 2HCl
S
OMe
47% Yield
Polymeric in
solid state
OR
S
OR
O
O
Bi
S
S
OR
OR
S
Bi
O
O
S
O
O
O
S
Na
RO
O
O
Bi
S
RO
OR
S
OR
S
Bi
O
S
OR
G.G. Briand, N. Burford, M.D. Eelman, T.S. Cameron, K.N. Robertson Inorg. Chem. 2003, 42, 3136.
Tris(Methylester-Thiolato) Bismuth Complex
OMe
MeO
OMe
BiCl3 +3 HS
+ 3KOH
S
O
95% EtOH
O
Bi
S
O
+ 3H2O
S
O
methyl thioglycolate (MTG)
MeO
26% Yield
OMe
OMe
OMe
O
S
S
Bi
O
Bi
O
S
S
O
S
MeO
O
Model of CBS!
S
O
OMe
OMe
O
O
O
K
O
O
O
Bi
Bi
O
O
O
O
CBS
O
K
O
O
O
G.G. Briand, N. Burford, M.D. Eelman, T.S. Cameron, K.N. Robertson Inorg. Chem. 2003, 42, 3136.
E. Asato, K. Katsura, M. Mikuriya, T. Fujii, J. Reedijk, Inorg.Chem. 1993, 32 5322-5329.
ESI-MS ofBiCl3 and 3 (MTG + KOH) in 95% Ethanol
OR
O
S
A
O
OR
S
R = Me
Bi
O
RO
S
O
OR
RO
S
S
A = K; R = Me
A =Na; R = Me
K
O
Bi
O
OR
S
OR
S
O
Bi
O
S
S
O
RO
OR
O R = Me
S
S
Bi
O
RO
OR
Peak assignments confirmed by ESI-MS/MS
G.G. Briand, N. Burford, M.D. Eelman, T.S. Cameron, K.N. Robertson Inorg. Chem. 2003, 42, 3136.
Tris(Methylthiosalicylato) Bismuth(III) Complex
O
MeO
OMe
BiCl3 + 3
95% EtOH
+ 3KOH
Bi
S
SH
OMe
S
O
O
S
+ 3H2O
O
methylthiosalicylate (MTS)
MeO
66% Yield
542.9
MeO
MeO
O
O
S
Bi
S
Bi
S
O
S
O
MeO
OMe
S
O
356.9
MeO
732.9
A = Na
212.0
372.9
407.1
N. Burford, M.D. Eelman, T.S. Cameron, Chem.Commun. 2002, 1402
749.1
616.9
A=K
A
Model of ‘BSS’
O
O
OMe
MeO
Bi
O
O
OMe
S
O
Bi
S
OH
Bi
S
O
MeO
O
‘BSS’
S
S
O
O
S
OMe
MeO
c.f.
OH
HO
N
OH
OH
N
HO
N
O
O Bi
O
O OO
N
OH
OO O
O
Bi O
O
N
O
N
O
Bi
O O
HO
N. Burford, M.D. Eelman, T.S. Cameron, Chem.Commun. 2002, 1402
J.H. Thurston, E.M. Marlier, K.H. Whitmire, Chem. Commun., 2002, 2834.
O O
O
O
Bi
O
N
O
N
OH
ESI-MS Identification of Bismuth Complexes
Containing L-Cysteine and Glutathione
NH2
O
L-cysteine =
OH
SH
SH
Tripeptide:
O
O
O
H
N
Glutathione =
HO
N
H
NH2
BSS
BiCl3
Bi(NO3)3
OH
O
L-cysteine
+ n
glutathione
n = 1-3
Cys
50% EtOH or
H2O
ESI-MS of BSS and L-Cysteine in Aqueous Solution
O
O
O
1:1
NH2 Bi
S
H3N
O
Bi
O
S
NH3
S
O
Peak assignments confirmed by MS/MS
Burford, N.; Eelman, M.D.; Mahony, D.; Morash, M. Chem. Commun. 2003, 146-147.
1:2
ESI-MS of Bi(NO3)3 and Glutathione in Aqueous Solution
O
OH
1:1
O
H2N
O
Bi
NH
O
O
NH
S
O
O
Bi
H2N
NH
S
HO
O
NH2
HO
O
O
O
S
NH
O
NH
O
1:2
NH
Bi
O
NH
S
OH
O
O
Peak assignments confirmed by ESI-MS/MS
Burford, N.; Eelman, M.D.; Mahony, D.; Morash, M. Chem. Commun. 2003, 146-147.
NH2
OH
ESI-MS Data for Mixtures of Bi(NO3)3 and an Amino
Acid in 50% EtOH
Peak assignments confirmed by MS/MS
Amino
Acid
m/z
Rel. Int.
(%)
Assignment
Bi:Am
Amino
Acid
m/z
Rel. Int.
(%)
Assignment
Bi:Am
His
516.9
5
1:2
Cys
775.9
5
2:3
Thr
444.9
10
1:2
654.9
20
2:2
Met
881.7
20
2:3Na
449.0
45
1:2
859.7
40
2:3
328.0
100
1:1
710.7
10
2:2
818.0
5
2:3
526.9
30
1:2Na
682.8
10
2:2
504.9
65
1:2
477.0
100
1:2
355.9
35
1:1
342.0
55
1:1
471.1
5
1:2
498.9
10
1:2
Asn
Hcys
Gln
Burford, N.; Eelman, M.D.; LeBlanc, W.G. Can. J. Chem. 2004, 82, 1254-1259.
Briand, G.G.; Burford, N.; Eelman, M.D.; Aumeerally, N.; Chen, L.; Cameron, T.S.; Robertson, K.N. Inorg. Chem.
2004, 43, 6495.
Bi:Am Assignments: Structural Possibilities
Am = Conjugate base of the amino acid
O
O
NH2
NH2
O
O
R
R
Bi
Bi
1:2
O
R
1:1
O
O
H
N
H2N
H2N
Bi
O
R
O
R
R
Bi
H2N
O
Bi
R
O
NH2
O
O
R
O
2:2
O
O
N
H2
2:3
Bi
Facilitating Interactions of Other Amino Acids
With Bismuth
Hypothesis:
• L-cysteine kinetically will stabilize coordination of
amino acid conjugates to bismuth
General Procedure:
Bi(NO3)3 + Cys + Am
50% EtOH
Am = Conjugate base of the amino acid
Facilitating Interactions of Other Amino Acids With Bismuth
Using L-Cysteine
Peak assignments confirmed by MS/MS
Amino
Acid
m/z
Assignment
Bi:Cys:Am
Amino
Acid
m/z
Assignment
Bi:Cys:Am
His
482.9
1:1:1
HCys
803.8
2:1:2
362.0
1:0:1
790.1
2:2:1
859.1
2:2:1
462.9
1:1:1
532.2
1:1:1
786.7
2:2:1
Tyr
508.9
1:1:1
459.9
1:1:1
Ser
760.2
2:2:1
339.0
1:0:1
433.1
1:1:1
800.8
2:2:1
773.7
2:2:1
473.9
1:1:1
446.9
1:1:1
800.7
2:2:1
803.8
2:2:1
473.9
1:1:1
476.9
1:1:1
Arg
502.0
1:1:1
Pro
443.2
1:1:1
Trp
Thr
Met
Asn
Gln
Lys
Amino Acids That Do Not Interact
With Bismuth
General Structure:
O
H3N
H
C
R
C
O
Amino Acid
Gly
-R Group
-H
Ala
Val
Leu
Ile
Phe
Asp
Glu
-CH3
-CH(CH3)2
-CH2CH(CH3)2
-CH(CH3)CH(CH3)2
-CH2Ph
-CH2CO2H
-CH2CH2CO2H
ESI-MS of Bi(NO3)3 and Glutathione in Aqueous Solution
O
OH
1:1
O
H2N
O
Bi
NH
O
O
NH
S
O
O
Bi
H2N
NH
S
HO
O
NH2
HO
O
O
O
S
NH
O
NH
O
1:2
NH
Bi
O
NH
S
OH
O
O
-Glu
Burford, N.; Eelman, M.D.; Mahony, D.; Morash, M. Chem. Commun. 2003, 146-147.
NH2
OH
The First Bismuth Complex Containing a
Biomolecule
NH2
Bi(NO3)3.5H2O +
O
+
OH
Ligand Stabilisation
SH
N
N
50% EtOH
H3N
S
O
O
H2O
N
Bi
N
O
N
O
O
N
O
O
O
Yield: 31%
Briand, G.G.; Burford, N.; Eelman, M.D.; Aumeerally, N.; Chen, L.; Cameron, T.S.; Robertson, K.N. Inorg. Chem.
2004, 43, 6495.
Equilibria and Tautomerism for Cysteine
O
Dianionic
S
O
NH2
-H+ H+
Monoanionic
O
S
O
OH
HS
NH2
O
O
S
NH2
O
NH3
-H+ H+
Neutral
O
HS
O
OH
HS
NH2
Monocationic
O
O
S
NH3
OH
NH3
-H+ H+
O
H2S
O
OH
NH2
HS
O
OH
NH3
HS
OH2
NH2
Comparison with a Derivative of a
Bismuth-Amino Acid Complex
H3N
S
O
O
H2O
O
N
Bi
O
N
O
N
O
O
N
O
O
O
Bi(Cys)(Phen)(NO3)2H2O
c.f.
NH2 Bi
S
Cl
Herrmann, 1993
Bi(Cys)(Phen)(NO3)2H2O is more viable in acidic media and is a closer
model of the potential interaction of bismuth with cysteine in the gastric
environment!
Consider the Other Heavy Metals
How do the other heavy metals interact with the amino acids?
As
Cd
Sb
Hg Tl
Pb Bi
= bioactive
= toxic
Identification of Lead-Amino Acid Adducts
by ESI-MS
 Same ESI-MS method used for bismuthamino acid mixtures
 Pb forms kinetically stable complexes with all
of the essential amino acids
All amino acids: 1:1, 1:2, 2:2 and 2:3 Pb:Am ratios
Thr, Met, Asp: 3:2 Pb:Am ratios
Ala, Val, His, Glu, Arg, Pro: Form Pb:Am
complexes containing H2O or NO3
Arg: 1:1, 1:2, 1:4, 1:5, 1:6 and Pb:Am ratios
Burford, N.; Eelman, M.D.; LeBlanc, W.G.; Cameron, T.S.; Robertson, K.N. Chem. Commun. 2004, 332.
ESI-MS of Pb(NO3)2 and L-Threonine in 50% EtOH
974
216.9
973
972
326.0
1:1
975
976
971
977
973.7
972 .8
3:3
974.8
975.8
971.8
282.1
970.8
648.9
1:2
973.7
976.8
854.9
3:2
Peak assignments confirmed by MS/MS
3:3
Synthesis of the First Lead-Amino Acid
Complex
NH2
O
Pb(NO3)2 +
OH
50% EtOH
O
O
N
OH2
O
O
H3N
Pb
O
NO3
OH2
O
O
Yield: 55%
H3N
Zwitterionic valines
Identification of Interactions Between Heavy
Metals and Amino Acids Using ESI-MS
Metal
 As3+
 Sb3+
# amino acids
5: Ser, Thr, Cys, Asn, Gln
4: His, Cys, Glu, Gln
Bi3+
7: His, Thr, Met, Cys, Hcys, Asn, Gln
Pb2+
21
 Tl+
21
 Hg2+
21
 Cd2+
21
Summary
• ESI-MS offers a powerful new technique in
understanding heavy metal bio-incorporation
• Study interactions of other small and larger
biomolecules with all heavy metals by virtue of
their distinctive m/z values
• The solid state structures of a bismuthcysteine and lead-valine complexes are the
first examples involving amino acids for both
• Consistent with assignments of ESI-MS data
• Insight into the coordination mode for cysteine
in the acidic gastric environment
Acknowledgments
Dr. Neil Burford
Wes LeBlanc
The Burford Group
Dr. T.S. Cameron and Dr. K.N. Robertson (DALX)
Maritime Mass Spectrometry Laboratories
Canada Research Chairs Program
Nova Scotia Research and Innovation Trust Fund