Theoretical studies on the ground states in image (M = Fe, Ru, Os) and excited states in image using density functional theory

We present a comparative study using density functional theory on the molecular structure, electronic structure and relative properties of View the MathML sourceM(terpyridine)22+(M(tpy)22+)andM(n-butyl-phenylterpyridine)22+View the MathML source(M(B-ptpy)22+) (M = Fe, Ru, Os). The trends of the center ionic effects and the introduction of electron-donating groups on the electronic structure and chemical stabilities have been investigated in detail. The results show that, for View the MathML sourceRu(tpy)22+andOs(tpy)22+, the lowest energy transition are assigned as the singlet metal-to-ligand charge transfer (MLCT). For View the MathML sourceFe(tpy)22+, the lowest energy transition corresponds to the intraligand π–π* character. As the case of View the MathML sourceM(B-ptpy)22+ (M = Fe, Ru, Os), the lowest energy transitions can be assigned as mixed metal/ligand-to-ligand charge transfer. The time dependent density functional (TDDFT) method is applied to calculate the singlet and triplet electronic states of View the MathML sourceM(tpy)22+ (M = Fe, Ru, Os) based on the ground-state geometry. The three absorption bands observed experimentally for View the MathML sourceRu(tpy)22+ are well reproduced by the TDDFT technique. Some insights on the difference observed for these complexes in changing the central metal atom are given. The luminescence for View the MathML sourceRu(tpy)22+ originates from the lowest triplet excited states and is assigned to the MLCT character.