Ethidium bromide Eth Br Scheme is a cationic dye

Ethidium bromide (Eth Br) (Scheme 1) is a cationic dye and antiviral drug that interacts with both double stranded DNA and RNA by intercalation between the abscisic acid pairs. The fluorescent complex between Eth Br and polynucleic acids was first reported by Le-Pecq and Paoletti in 1967 [15]. When the phenanthridium moiety of Eth Br intercalates DNA, a large increase in fluorescence is observed and it is a useful probe to measure drug–DNA interactions. In general, it is known that intercalation of the dye into strings of the nucleic acid, because of electrostatic binding, creates strong fluorescence enhancement but with additional nonintercalative, less fluorescence-enhanced is observed [16]. There are two binding types: the first type is intercalation between base pairs and the secondary type, is electrostatic binding between the cationic Eth Br and the anionic phosphate groups of the DNA surface. The secondary mode of binding is most obvious at low salt and high dye concentrations. Binding of dye is saturated when one dye molecule is bound for every four or five base pairs [17].
Transition-metal oxides are highly regarded because they can provide strong LSPRs in the NIR region which it is due to the special character of their outer-d valence electrons, and have great potential in various fields [18]. Nano-structure ruthenium species, with high surface area-to-mass ratios [19], have application in many organic transformations in recent years [20–23]. Among transition metal oxides, RuO2 is one of the most important compounds of the application. It is used in supercapacitors because of its potential in reversible redox reactions, long life cycle and metallic type conductivity. RuO2 exhibits interesting properties such as high stability, low overpotentials for O2 and Cl2 production, low resistivity, high chemical and thermodynamic stability under electrochemical environment. Also it can be used in catalytic activity due to coordinatively unsaturated Ru centers [24,25].
So far, many methods for the synthesis of RuO2 have been developed, such as thermal synthesis, combustion synthesis, precipitation [26], sol–gel method [27], pulse-laser deposition [28], colloidal method [29], etc. In recent years many kinds of nanomaterial have been prepared by sonochemical method [30–32]. This method has advantages such as homogeneous nucleation and short crystallization time compared with the other methods to produce nanomaterials also it is efficient, green and inexpensive approach. Due to these advantages, this method is considered for chemists [33–36]. The power of ultrasound includes a kind of energy that can drive chemical reactions, which is different from that prevalent energies. This power is due to cavitation bubbles. These bubbles are produced into the liquid structure and tiny voids are generated via increasing the distances between molecules. These voids grow by using the energy of the ultrasound generator and reach a maximum size then they collapse. During the collapse, is produced high temperature (≥5000K) and pressure (≥20MPa). As a result, nanomaterials can be made by this method. The ultrasound irradiation can influence on the properties of the nanoparticles such as sizes and morphologies that it may be crucial to the different types of the technological applications [35,37–38].
In this paper, we report the synthesis and crystal structure of two new Ru(II) complexes, [(η6-p-cymene)RuCl(L2)]PF6 (R2) and [(η6-C6H6)RuCl(L2)]PF6 (R4), with ligand (E)-N-((6-bromopyridin-2-yl)methylene)-4-(methylthio)aniline (L2) (Scheme 2). Their binding with calf thymus DNA, was investigated using electronic absorption spectra, fluorescence and redox behavior studies. Also, nanoparticles of RuO2 were obtained via calcination of ultrasonic treated R2 and R4.


Results and discussion

Two new Ru(II) complexes of [(η6-p-cymene)RuCl(L2)]PF6 (R2) and [(η6-C6H6)RuCl(L2)]PF6(R4) (E)-N-((6-bromopyridin-2-yl)methylene)-4-(methylthio)aniline (L2) were synthesized and characterized. The crystal structure of complexes were determined by X-ray crystallography. The Ruthenium(II) atom of compound R2 is six coordinated to a p-cymene ring, two N atoms of L2 and Cl. Also in compound R4 Ruthenium(II) atom is six coordination it have been coordinated by C6H6 ring, two N atoms of L2 and Cl.