Abstract
Theoretical study of the molecular geometries, electronic and thermodynamic properties of dipyrido-(3,2-a:,-c)-phenazine (dppz) was carried out in the gas phase under standard conditions using PM6 Hamiltonian in semiempirical model. Effects of chlorine substituents on these properties were also investigated. The results showed that all the electronic and thermodynamic properties investigated were affected by the number and relative position of chlorine substituents. Variations in some properties are not significant for some isomeric congeners, having the same number of chlorine substituents, while a number of properties showed general variation with both the number and position of chlorine substituents. Successive addition of one chlorine atom after the other at adjacent position to the last chlorine substituent increases the total energy by 241 eV and decreases the LUMO-HOMO gap by an average value of 0.124 eV. Geometry and energy optimization show that all the molecules considered are planar.
Highlights
Previous researches have shown that the number and position of electron-withdrawing groups like chlorine, bromine, and uorine substituents signi cantly affect the structural properties and thermodynamic stabilities of heteroaromatic polycondensed rings such as phenazine and Phenoxathiin [1,2,3].Dipyrido-(3,2-a:2′,3′-c)-phenazine (Figure 1) is a derivative of phenazine with two pyridine rings on the phenazine
Special attention has been given to dipyrido-(3,2-a:2′,3′-c)-phenazine, its derivatives and metal complexes partly because of the interesting characteristics of its ruthenium complexes; [Ru2(dppz)]2+ both in water and when bound to DNA [4, 7, 8]. e DNA-binding of dppz complexes of other transition metals, such as platinum, iridium, rhodium, rhenium, and chromium have been investigated, and the chromium (III) complexes of dppz have been studied because of their special photophysical properties [4]
In order to investigate the effect of chlorine substituents on dppz, the geometries of polychlorodipyrido-(3,2-a:2′,3′-c)-phenazines were compared with that of the unsubstituted dppz. e effects of the positions of chlorine substituents on the geometries were investigated by comparing the geometries of the various pcdppzs
Summary
Previous researches have shown that the number and position of electron-withdrawing groups like chlorine, bromine, and uorine substituents signi cantly affect the structural properties and thermodynamic stabilities of heteroaromatic polycondensed rings such as phenazine and Phenoxathiin [1,2,3]. Dppz is a polypyridine compound, and polypyridines have been severally reported [4,5,6] to have excellent ability to bind metal ions in solutions, and various derivatives of the ligands have been studied in order to explore their binding abilities, biological and electrochemical behavior, as well as excited state behaviour. In these reports, their metal complexes are known to bind DNA and their spectroscopic and electrochemical properties can be tuned. Future researches promise to consider other halosubstituted dppzs and possible reduction of the LUMO-HOMO energy gap of the ruthenium (II) complexes chlorosubstituted dppzs
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