Theoretical studies on the electronic structures and related properties of [Ru(L)3]2+ (L=bpy, bpm, bpz) with DFT method

Abstract

Theoretical studies on the complexes [Ru(L)3]2+ (L=bpy, bpm, bpz) are carried out using the density functional theory (DFT) method and the B3LYP/LanL2DZ level of theory. The effects of the ligands on the electronic structures and related properties, e.g. the components and the energies of some frontier molecular orbitals, the spectral characteristics, and the net charge populations of some main atoms of the complexes, and the effect of N atom position on total energy of different isomer, etc. have been investigated. The results show that the different ligands (bpy, bpm, bpz) have some interesting effects on the electronic structures and related properties of complexes [Ru(L)3]2+. First, the energies of corresponding frontier molecular orbitals of the three complexes all greatly reduce in the order of εi(I)>εi(II)>εi(III). The energy intervals (ΔεL–H) between LUMO and HOMO for the three complexes are in the order of ΔεL–H(I)<ΔεL–H(II)<ΔεL–H(III). Second, the HOMOS of Ru(L)32+ can be characterized by d orbitals of Ru2+, whereas for the LUMOS, although their components may be characterized by p orbitals of the ligands, the contributions of N atomic orbitals in different complexes are greatly different. Third, the most negative charges are all populated on N1 for each of the three complexes, and among them that on N1 (−0.5015) of II is the most. On the other hand, as for C atoms of the main ligand, the most negative charges are populated on C5 of complex II. Fourth, the iso-complexes II and III with identical types of bonds have different total energies. The characteristics of atomic charge populations in the poly-heteroatomic systems as well as the effects of N atom positions on total energies of different isomers can be simply and satisfactorily interpreted applying the schematic map based on the law of polarity alternation and the idea of polarity interference. Final, the different ligand has a little effect on the coordination bond length, and the trend agrees with references. The above theoretical results should be very useful in the analysis of DNA-binding mechanism of complexes and the designs of binding agents to DNA, etc.