Studies on 6,6-disubstitution effects of the dpq in [Ru(bpy)(2)(dpq)](2+) with DFT method

Theoretical studies on 6,6'-disubstitution effects of the dpq in [Ru(bpy)(2 )(dpq)](2+) are carried out by using DFT method at the B3LYP/LanL2DZ level. The substituent effects caused by the electron-pushing group (OH) and the electron-withdrawing group (F) on the electronic structures and the related properties, the energies and the components of some frontier molecular orb itals, the spectral properties, and the net charge populations of some main atoms of the complexes, etc., have been investigated. The computational re sults show that the substituents have some interesting effects on the elect ronic structures and related properties of the complexes. First, on the bas is of the analysis of the frontier molecular orbitals, the substituents inf luence the first excited-state properties of the substitutive derivates. Th e electron-withdrawing group (F) can activate the main ligand and passivate the co-ligands in the first excited state of [Ru(bpy)(2)(2F-dpq)](2+), whe reas the Z= C electron-pushing group (OH) does not have this effect in this system. Second, the ground band wavelength of electronic spectra of each o f complexes [Ru(bpy)(2)(2R-dpq)](2+) (R = OH, H, or F) is shorter slightly than that of well-known complex Ru(bpy)(3)(2+). The substitution of electro n-pushing group (OH) or electron-can cause a slight red shift in the ground withdrawing group (F) on 6,6' sites of dpq in [Ru(bpy)(2)(dpq)](2+) band o f the complex. Third, some interesting characteristics of atomic net charge populations on the main ligands of the three complexes occur, and they can be simply and satisfactorily interpreted applying the schematic map expres sed by several series of arrowheads, based on the law of polarity alternati on and the idea of polarity interference. The above theoretical results sho uld be important to further inquiry into the interaction mechanism of the c omplexes with DNA active units from both the molecular orbital interactions and the atomic charge interactions.