Book of Abstracts - Ruhr-Universität Bochum

P-36
ISBOMC `10 5.7 – 9.7. 2010 Ruhr-Universität Bochum
Novel Polypyrrole Substituted Carbon Monoxide Releasing Molecules
(CO-RMs); New Delivery System for Carbon Monoxide
Niall B. McGuinness, a Carmel B. Breslin, a and A. Denise Rooney a
a Environmental Technologies and Biomaterials Research Group, Department of Chemistry,
National University of Ireland, Maynooth, Co. Kildare, Ireland. Email: niall.b.mcguinness@nuim.ie
Research has shown that minute quantities of carbon monoxide (CO) molecules produced in the
human body are a fundamental component for life processes, but in larger doses the inherent toxic
nature of CO cannot be ignored. However, CO liberated from CO-RMs can be accurately controlled
and delivered at precise concentrations. Beneficial actions of CO include cardioprotection against
blood flow restriction, heart attack and cardiac graft rejection; prevention against the increase of
strength in muscle contraction of the heart; and suppression of the inflammatory response 1 . A problem
associated with several of the CO-RMs is the transition metal (T.M.) employed, which can be toxic
due to accumulation in the human body.
N
N
O
O
N
H
N
H
N N
4,4'-Bis-(N -propyl-3-pyrrole-carbamoyl)-2,2'-bipyridine
1
Figure 1: Novel substituted pyrrole monomer and metal complex synthesised.
OC
OC
94
CO
Mo
CO
N
N
O
O
N
H
N
H
N N
Tetracarbonyl (4,4'-bis-(N-propyl-3-pyrrole-carbamoyl)-2,2'-bipyridine)
molybdenum (0)
We have set out to bind T.M. carbonyl complexes to polypyrrole, a biocompatible conducting
polymer. The carbonyl complex is trapped in the polymer so that after CO is released into the tissue
the complex can then be removed. The monomer unit 1 has been synthesised and successfully
undergoes electrochemical polymerization. Mo(CO)4 has been complexed to this monomer at high
yield using a microwave-assisted method. Before investigating the electrochemical response of the
polymer formed from complex 2, studies were carried out on 2 in solution. Electrochemical studies
indicate that upon 1-electron oxidation, Mo(CO)4(bipy-pyr) undergoes CO subsitution in a
coordinating solvent (Figure 2). Direct evidence that the oxidation results in CO release was provided
by studies performed using an Optically Transparent Thin-Layer Electrochemical (OTTLE) cell with
IR detection. Our results indicate that this is a promising approach for the controlled release of CO
from a polymer.
0.0002
0.0001
I (Amps/cm 2 )
0
Black: redox couple of Mo(CO) 4(bpy‐pyr)
in DCM
Grey: redox couple of Mo(CO) 4(bpy‐pyr)
in DCM with 3 eq. of MeCN present
*1‐electron oxidation and reduction
of Mo(CO) 4(bpy‐pyr)
Loss of reduction peak
caused by rapid CO
substitution due to
-0.0001
* presence of MeCN
0 0.25 0.50 0.75 1.00 1.25
Figure 2: Cyclic voltammograms of Mo(CO)4(bipy-pyr) in DCM and MeCN.
References
E (Volts)
1. R. Foresti, M. G. Bani-Hani, R. Motterlini Intensive Care Med. 2008, 34, 649-658.
*
2