Spectrochimica Acta Part A 79 (2011) 1849–1855
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
j ourna l ho me page: www.elsevier.com/locate/saa
Synthesis and thermal studies of tetraaza macrocylic ligand and its transition
metal complexes. DNA binding affinity of copper complex
M. Saif
∗
, Mahmoud M. Mashaly, Mohamed F. Eid, R. Fouad
Department of Chemistry, Faculty of Education, Ain Shams University, Roxy 11711, Cairo, Egypt
a r t i c l e i n f o
Article history:
Received 3 February 2011
Received in revised form 13 May 2011
Accepted 24 May 2011
Keywords:
DNA binding
Tetraaza macrocyclic ligand
Transition metal ions
Anti-tumor
a b s t r a c t
A Tetraaza Macrocylic Ligand (H
2
L) and its complexes, [Cd(H
2
L)(OH
2
)
2
](NO
3
)
2
·1/2OH
2
(I),
[Co(H
2
L)(OH
2
)](NO
3
)
2
·1/2OH
2
(II), [Cu(H
2
L)(NO
3
)
2
]·3/2OH
2
(III) and [Ni(H
2
L)(NO
3
)(OH
2
)]NO
3
·OH
2
(IV), have been synthesized and characterized on the basis of elemental analysis, molar conductivity,
1
H
NMR, UV–vis, FT-IR and mass spectroscopy. All results confirm that the prepared compounds have 1:1
metal-to-ligand stoichiometry, octahedral configuration and the ligand behaves as a neutral tetraden-
date towards the metal ions. [CdL(OH
2
)
2
] (V), [CoL(OH
2
)
2
] (VI), [CuL(OH
2
)
2
] (VII) and [Ni(H
2
L)(NO
3
)
2
]
(VIII) were synthesized pyrolytically in solid state from corresponding compounds (I–IV). Analytical
results of complexes (V–VIII) show that the ligand behaves either as a neutral tetradendate or dianionic
tetradentate ligand towards the metal ions. The binding of H
2
L and its copper complex (III) to DNA has
been investigated by ultraviolet absorption spectroscopy. The experiments indicate that H
2
L and its
copper complex (III) can bind to DNA through an intercalative mode. The H
2
L and its copper complex (III)
exhibited anti-tumor activity against Ehrlich Acites Carcinoma (E.A.C) at the concentration of 100 g/ml.
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
Synthetic tetraaza macrocyclic ligands are a growing class of
compounds with varying chemistry [1–9]. The chemical proper-
ties of tetraaza macrocyclic complexes can be tuned to force metal
ions to adopt unusual coordination geometry. Transition metal
tetraaza macrocyclic complexes have received much attention as
an active part of metalloenzymes [10–12] as biomimic model com-
pounds [13–16] due to their resemblance with natural proteins like
hemerythrin and some other enzymes. In these macrocyclic com-
plexes, both the metal ion and the size of ring play an important
role. The aza crownethers have complexation properties that are
intermediate between those of all oxygen crowns and all nitrogen
cyclams [17].
Deoxyribonucleic acid (DNA) is a genetic material that acts as a
form of memory storage for genetic information [18]. DNA is the
target of some anti-tumor reagents, these reagents react with DNA
thereby stopping the replication of DNA and inhibiting the growth
of tumor cells [19].
Copper macrocyclic complexes have been reported to inter-
act with DNA in different binding modes and exhibited efficient
nuclease activity but unfortunately have received little attention.
∗
Corresponding author. Tel.: +020109542296; fax: +0222581243.
E-mail address: mona saif1@yahoo.com (M. Saif).
However, the exact mode and extent of binding and cleavage mech-
anism still have remained unknown leaving behind a scope for an
extensive study involving different structures of macrocycles to
evaluate and understand the features that determine the mode of
the binding interaction with DNA and mechanism [20].
Thereby, in this study, we have synthesis and structural
characterization of a diamidediimine macrocycle (H
2
L) and its
coordination behavior with transition metals (Cd
2+
, Co
2+
, Cu
2+
and
Ni
2+
). The thermal investigation explored the possibility of obtain-
ing new complexes pyrolytically in the solid state, which cannot be
synthesized from solutions. Moreover, DNA interaction and cyto-
toxic activity for copper complex is reported.
2. Experimental
2.1. Materials and physical methods
Ethylene diamine, ethylacetoacetate (chemical laboratory),
hydrated metal salts were obtained from Merck and used without
further purifications. Herring Sperm DNA (HS-DNA) (mallinckrodt)
and Tris(hydroxymethyl)-aminomethane–HCl (tris-HCl) were used
as received. All solvents used were of standard/spectroscopic grade.
Bi-distilled water was used.
Electronic spectra were recorded on a JASCO model V-550
UV–vis spectrophotometer. FT-IR spectra were measured by
Nicolet 20F-FT-IR spectrometer using polyethylene discs. Mag-
1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2011.05.071