Study On Structure And Metal Multi - Bond Theory Of Macrocyclic Ruthenium Bimetallic Complexes

In this thesis, ruthenium-group porphyrazines including monomer, dimer and pyridine-solvated derivatives have been examined using hybrid density functional theory(DFT), the quasi-relativistic effective core potentials(ECPs) as well as explicit and implicit solvation. Regarding our investigated systems, we explored FeII, RuII and OsII(d6 electron configuration); porphyrazine(labeled as Pz) ligand was used, which also can approximately represent porphyrin(Por) and phthalocyanine(Pc) that are commonly used in experiment; Research system including multiple electronic spin states "isomer" such as(RuIIPz)2 in d6- d6 effects, can be formed five electronic states from singlet to nonet states; additionally, dimer and solvated derivative can adopt both eclipsed and staggered configurations.The structure optimization and energy calculation show that the dimer(RuPz)2 is more stable in energy than its monomer(RuPz), the staggered configuration between two Pz ligands relative to Ru-Ru axis direction is energetically favored. The staggered triplet-state(RuPz)2 was calculated as the global ground state, consistent with the experimental results. Complete active space self-consistent field(CASSCF) and n-electron valence state second-order perturbation theory(NEVPT2) supported the DFT results, and further confirmed the Ru2 double bond is composed of one dσ and one dπbonds. The Ru-Ru bonding energy was calculated to be 30.7 kcal/mol while considering the basis set superposition error(BSSE). The electronic absorption spectra in pyridine solution were calculated by the time-dependent density functional theory(TD-DFT) on the basis of the optimized structures of(RuPz)·py2 and(RuPz)2·py2. A pronounced red-shift of major absorption bands is found in the latter compared with the former.Experimental observation of the redshift of absorption spectra upon increasing the solution concentration was well reproduced by the present calculations. The complexes(MIIPz),(MIIPz)2 and(MIIPz)·py2(M = Fe and Os) were also explored in theory. It is shown that(OsPz)2 has the singlet global ground state. The Os-Os double bond,composed of one dσ and one dπ bonds, was assigned, which is similar to that of(RuPz)2.However, M-M bonding energy of(OsPz)2 is much larger than(RuPz)2, which is related to the stronger relativistic effects of the heavier Os metal. The quintuplet state structure of(Fe Pz)2 has the lowest energy in its all dimeric isomers. The calculated distance of Fe-Fe is 4.26 ?, longer than that of Ru-Ru(2.38 ?) and Os-Os(2.32 ?). This Fe-Fe distance is much longer than the sum of van de Waals radii of two iron atoms(2.64 ?),indicating no bonding between two iron atoms in(Fe Pz)2. So our calculated results demonstrate that the iron porphyrazine complex should exist in the form of monomer.This agrees with the various monomeric iron porphyrin and iron phthalocyanine complexes that are found in experimental synthesis and in the nature. TD-DFT calculations show that absorption spectra of(MPz)·py2 exhibit regular blue-shifting phenomenon along Fe, Ru to Os.