ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P63. Synthesis and Structure af a Thiosemicarbazonecopper(II) Complex
with Cytosine
R. Gil-Garcia, a B. Donnadieu, b J. Garcia-Tojal a
a
Department of Chemistry, University of Burgos, Pza. Misael BaĂąuelos s/n, 9001 Burgos, Spain
e-mail: rgil@beca.ubu.es
b
Department of Chemistry, University of California, Riverside, CA 92521, USA
Thiosemicarbazones and their metal complexes raise a great interest due to their ability of inhibit the DNA
synthesis. Although these compounds have been widely investigated, as far as we are aware, there is no evidence
of structures with thiosemicarbazonemetal entities and nucleobases.
Here we present a new thiosemicarbazonecopper(II) complex with cytosine [CuL(Hcyt)](ClO4) that contains
[CuL(Hcyt)] + monomeric units and perchlorate counterions. The two crystallographically independent cationic
entities present in the asymmetric unit are related through a pseudo center of inversion, as it is shown in
Figure 1. The coordination around the metal center shapes a distorted square–planar topology. The
thiosemicarbazone ligand exhibits the usual NNS tridentate behavior, while the cytosine links to the copper(II)
ion by the N13 atom. Notwithstanding, there is a pseudocoordination (4+1) between the metal centre and the
oxygen of the cytosine.
The title structure proves the affinity of the [CuL] + cations for cytosine nucleobases. On the other hand, the
existence of multiple non-covalent interactions spreads the possibilities for the interaction of
pyridine-2-carbaldehyde thiosemicarbazonatocopper(II) entities with nucleotides and DNA, including mono- or
polynuclear π-stacking and anion-π interactions with phosphate groups. In addition, other modes of action
cannot be discarded, e. g. coordination to other nucleobases or even phosphates.
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