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Synthesis, Spectral Characterization, and Nucleic Acids Interactions of
Nickel (II)-Salen complex
Olivia F. Hurst, Dana Warwick, Dr. Roslyn Theisen , and Dr. Sanchita Hati ❖
Department of Chemistry ❖University of Wisconsin-Eau Claire ❖Eau Claire, WI 54701❖Spring 2015
Abstract
Around the world, cancer is one of the leading causes of death. DNA is the primary target molecule for most anticancer therapy. Transition metal complexes are known to have DNA binding and cleavage
properties under physiological conditions. Currently, we are investigating the interactions between a number of nickel (II) complexes and nucleic acids (DNA/RNA) in an attempt to design and develop
metal complexes that can have more efficiency in nucleic acids binding and cleavage and therefore, could be used in cancer chemotherapy. We have synthesized Nickel (II)-Salen complex and the
synthesized product was characterized by UV-Vis spectroscopy and FT-IR. We are currently studying the interactions between the Nickel (II)-Salen complex and nucleic acids using UV-Vis spectroscopy
and gel electrophoresis. We will present the preliminary results of our study. Our overall goal is to synthesize transition metal complexes that could bind or cleave the target DNA/RNA molecules and
effective in the cancer treatment. This study could have major implications on the drug and health industry and potentially be a cure for cancer.
Introduction
Transition metal complexes are widely used in the medicine
industry as an anti-cancer drug. In 1964, a cis-Platinum
[Pt(NH3)2Cl2] was first reported to have the ability to suppress cell
division. This showed promise for transition metal-based drugs to
cure cancer cell growth. Many metal complexes show affinity for
binding to the target DNA. The metal-DNA interaction can occur
in two ways: diffuse and site binding. Diffuse binding is a long
range interaction in which the metal ions interact with the nucleic
acid through water interactions [1]. In site binding, the nucleic
acids bind/interact directly to the ligands surrounding the metal
ion or with the metal ion itself [1].
Complex Synthesis
The [N,N’-Ethylene-bis(salicylideneiminato)]-nickel(II), [Ni(II)(salen)] complex was
synthesized via a previously reported method, which involves a two-step reaction:

Synthesis of [Ni(II)(salen)]
Ni
Figure 3. UV-Vis Spectrum of 1.0 mM [Ni(II)(salen)] complex with
varying concentrations of DNA. The buffer used was Tris (5 mM,
pH 8.0) and NaCl (O.5 mM), 30 uL; acetonitrile, 80 uL; and
differing amounts of H2O.
 The objective of this project is to synthesize transition metalbased complexes that will be more efficient in binding or
cleaving target DNA/RNA and therefore, could be used in
cancer treatment.
 In our current studies, we aim to synthesize Ni (II) and other
transition metal complexes and characterize them through IR
and UV-spectroscopy. After these complexes are being
successfully synthesized and characterized, we will study their
interactions with DNA/tRNA using UV-Vis spectroscopy. We
will monitor the extent of cleavage of DNA/tRNA through gel
electrophoresis.
% Transmittance

The Spectroscopic properties of the [Ni(II)(salen)]
complex bound with DNA were studied by UV-Vis.
*C=N =
1618.70 cm-1
Figure 1. Infrared graph of the [Ni(salen)] complex.
Wavenumber (cm-1)
Figure 4. UV-Vis Spectrum of 0.1 mM [Ni(II)(salen)] complex with
varying concentrations of tRNA. The buffer used was Tris (5 mM,
pH 8.0) and NaCl (O.5 mM), 30 uL; acetonitrile, 80 uL; and
differing amounts of H2O.
 This peak at 1618.70 cm-1represents the C=N imine bond and confirmed that the
synthesized complex is indeed [Ni(II)(salen)] complex.
Conclusions

 = 330 nm
Absorbance
Objectives
The interatcions betweem [Ni(II)(salen)] complex and
tRNA were studied by UV-Vis spectroscopy.
Synthesis of [Sal2Ni(H2O)2]
Characterization of [Ni(II)(salen)] complex
Many transition metal complexes have also attracted a lot of
attention due to their DNA binding and cleavage properties. For
example, salen-Ni (II) complexes can be used for the cleavage of
guanine structures in DNA and RNA[2]. The salen complexes
have flexible conformations and can have a variety of geometries
[3]. Also, the flat, electron-rich aromatic surfaces of salen metal
complexes may assist in their interactions with nucleic acids [3].
Hydroxyl groups in the salen complexes cooperate to form free
radicals responsible for DNA cleavage [4].

Interaction between [Ni(II)(salen)] and
DNA/RNA
 = 420 nm

Wavenumber (nm)
Figure 2. UV-Vis Spectrum of 0.1 mM [Ni(II)(salen)] complex.
References
[1] Johnson, Arish; Sivasankaran, Nair. Synthesis, characterization and biological studies on some metal complexes with Schiff
base ligand containing pyrazolone moiety. Journal of Saudi Chemical Society. 2013, 1-8.
[2] Burrows, C.J., Rokita, S.E. Acc. Chem. Res. 1994, 27, 295-301
[3] Journal of Bimolecular Screening. 2011, 16, 26-35.
[4] S. Routier, H. Vezin, E. Lamour, J.-L. Bernier, J.-P. Catteau, and C. Bailly. DNA cleavage by hydroxy-salicylideneethylendiamine-iron complexes. Nucleic Acids Research. 1999, 27:21. 4160-4166.

We were successful in synthesizing the [Ni(II)(salen)]
complex. This is evident from the presence of imine
(C=N) band at 1618.70 cm-1 in the IR spectra and a
presence of absorption maxima at 330 and 420 nm in
the UV-Vis spectra.
The binding of [Ni(II)(salen)] complex to the target DNA
(puc 19) was evident from the change in the absorption
spectra in the presence of variable concentrations of
DNA molecule.
The interatcion between [Ni(II)(salen)] complex and
tRNA is revealed from the decrease in absortion at 330
and 420 nm.
Future Work
Current work is focused on the binding of the [Ni(II)(salen)]
complex with tRNA and DNA. In the future, we will
continue testing the [Ni(II)(salen)] complex binding
capabilities to nucleci acids through gel electrophoresis.
We will also synthesize other metal complexes and will test
their ability to bind or cleave the target tRNA and DNA
molecules through UV-Vis spectroscopy and gel
electrophoresis.