Design, synthesis and characterization of novel rhenium(V) and technetium(V) complexes as potential radiopharmaceuticals

Hlabela, Patrick Simon (2001) Design, synthesis and characterization of novel rhenium(V) and technetium(V) complexes as potential radiopharmaceuticals. Masters thesis, Rhodes University.




A number of bid en tate N, N-diethyl-N' -(R ')benzoylthiourea ligands (where R' = H, CH 3' CI, OCH3 and N02) have been synthesized, as well as the three Re(V) precursor complexes, ReOCliPPh3)2' [ReOlpY)4]CI and [n-Bu4N] [ReOCI4J. The reaction ofN,N-diethyl-'-benzoylthiourea (LH) with these three metal precursor complexes in methanol in the presence of a base gave a novel mixedligand complex bis(N,N-diethyl-N '-benzoylthioureato )methoxyoxorhenium(V), [ReO(L)2(OMe)] (1). In the absence of a base and under an inert atmosphere, the reaction between [nBu4N][ReOCI4] and LH yielded bis(N,N-diethyl-N'-benzoylthioureato)chlorooxorhenium(V), [ReO(L)2CI] (lb). The reaction ofLH with [ReOlpY)4]CI in ethanol and iso-propanol in the presence of sodium acetate gave the novel mixed ligand complexes bis(N,N-diethyl-N'benzoylthioureato) ethoxyoxorhenium(V), [ReO(L)lOEt)] (6) and bis(N,N-diethyl-N'benzoylthioureato)iso-propoxy)oxorhenium(V), [ReO(L)l OiPr)] (7), respectively. An oxygen bridged dirhenium complex, [(L)20Re-O-ReO(L)2] (15) was obtained when the reaction was carried out in acetonitrile. A series of mixed ligand Re(V)-oxo complexes using N, N-diethyl-N -(R' )benzoylthiourea (LR'),N,N-morpholino-N' -(R')benzoylthiourea (morph-LR') and 8-(N-(R')benzoylthiocarbamoyl)-1,4-ioxa-8-aspiro[4.5]decane ligands (spiro-LR') (where R' = H, CH3, CI, OCH3 and N02) «1)(14) have been prepared by the reaction of [ReOipY)4]CI and the ligand in the presence of sodium acetate in methanol. The solution state chemistry of these complexes has shown that complexes(1 )-(14) (with the exception of (1 b» undergo dimerization in solution to give complex (15) in the presence of water. Preliminary IH NMR kinetics studies of the dimerization of (1), (6) and (7) to (15) have shown that the rate of dimerization decreases in the order (7) > (6) > (1). The rate of dimerization has also been compared for complexes (1), [ReO(morph-L)z(OMe)] (8) and [ReO(spiro-L)2(OMe)] (13) and the rate of dimerization was found to be fastest for (13). The crystal structures of (1), [ReO(LN02)2(OMe)] (4), (6) and (15) have been determined. The Re(V)-oxo complexes (1), (4) and (6) have a slightly distorted octahedral geometry with the two acylthiourea ligands binding in a cis arrangement in the equatorial plane of the octahedron. The alkoxy and oxo ligands occupy the axial positions and are situated trans to each other. The crystal and molecular structure of complex (15), consist of two slightly distorted octahedral [ReO(L)2] moieties bridged by an oxygen atom with a Re-O-Re bond angle of 175.2(2)°. The preliminary studies done in the present study have indicated that the complexation chemistry oftechnetium(V)withtheN,N-diethyl-benzoylthioureaisdifferentto that of rhenium (V). The reaction between [n-Bu4N][TcOCl4] and N,N-diethyl-N'-benzoylthiourea yielded the square pyramidal cationic complex [TcO(L)2]Cl. By contrast the octahedral methoxy complex [ReO(L )2( OMe)] was obtained when the analogous Re(V)-oxo precursor, [n-Bu4N] [ReOCI4], was reacted with N,N-diethyl-N'-benzoylthiourea under the same reaction conditions.

Item Type:Thesis (Masters)
Uncontrolled Keywords:Radiopharmaceuticals, Technetium, Rhenium
Subjects:Q Science > QD Chemistry
Divisions:Faculty > Faculty of Science > Chemistry
Supervisors:Sacht, Cheryl
ID Code:2941
Deposited By: Mrs Carol Perold
Deposited On:05 Jun 2012 07:36
Last Modified:05 Jun 2012 07:36
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