Chemistry Reference
In-Depth Information
Figure 10.2
Dinuclear rhodium complexes for photodynamic therapy
of the interactions between dirhodium species and DNA, novel complexes have
been designed to bind DNA through both coordinative and intercalative interac-
tions. Dimeric rhodium complexes have often demonstrated antitumour activity in
the same order of magnitude as cisplatin, while potentially circumventing the toxic-
ity issues associated with the successful drug. Furthermore, research into the poten-
tial of dirhodium complexes in photodynamic therapy may result in replacements
for cisplatin derivatives in the foreseeable future.
17 - 38, 40 - 46
10.3.4 Rhodium( III ) Complexes
The kinetic inertness of rhodium(III) complexes may be believed to preclude the
ability of such species to modify or probe DNA and RNA function through covalent
interactions. Indeed, divalent Pt, divalent (and trivalent) Ru species have received
considerable attention in this fi eld, directly owing to the lability and substitution
chemistry of their ligands. Rhodium(III) complexes are low in the list of potential
DNA interacting agents, owing to their inability to undergo substitution reactions
on a physiologically relevant timescale.
47
Further application is also limited by the
inability of Rh(III), in contrast to Ru(III), to undergo activation through reduction
to the divalent species. As a consequence, few cytotoxic Rh(III) complexes have
been developed.
8,10,48
A number of Rh(III) analogues of known antitumour active
Ru(III) species have also been investigated. Like
fac
- [RuCl
3
(NH
3
)
3
],
mer
-
[RhCl
3
(NH
3
)
3
] is active, but insoluble.
8
Rh(III) analogues of the active Ru(III)
species, Na[
trans
- [RhCl
4
(Me
2
SO)(Im)] and (HIm)
trans
- [RhCl
4
(Im)
2
] were essen-
tially inactive, exhibiting modest inhibition on the growth of the primary MCa
mammary tumours.
49
The limited activity in each case has been attributed to the
kinetic stability of the Rh(III) relative to the Ru(III) systems towards ligand
substitution.
