A Time Dependent Density Functional Theoretical Studies Of The Ruthenium(Ⅱ) Complexes

The studies on molecular-scale electronic devices have been developed very rapidly. Linear conjugated metallic complexes are one of the models for the studies of molecular wires and molecular switches. The electronic absorption spectroscopy of the model complexes [RuCl(CO)(PH₃)₃]2(μ-CH=CH-CH=CH)-(CH=CH)_n(n=1, 2, 3, 5) have been investigated by using time-dependent density functional theory (TDDFT). When the hybrid basis sets method (Lanl2DZ(d) basis sets for Ru, and 6-31G(d) basis sets for other atoms) were adopted, the satisfactory assignments of the experimental absorption spectra have been achieved in this work.The present calculation results show that the electronic absorption spectra of Ru (n=l) is mainly characterized as the electron transfer of p(C=C)/d(Ru)→p^*(C=C) and p(C=C)/d(Ru)→p^*(C=O). As for (n=2, 3), the first experimental absorption peak is attributed to the electron transfer from p(C=C)/d(Ru) to p^*(P), while the second peak is attributed to the electron excitation of p(C=C)/d(Ru)→p^*(C=C)/d(Ru), and the third one is attributed to the electron transfer of p(C=C)/d(Ru)→p^*(C=O). As for (n=5), the first absorption peak of Ru(n=5) was attributed to the electron transfer of p(C=C)/d(Ru) →p^*(C=C)/d(Ru);while the second and third one are attributed to the electron transfer from p(C=C)/d(Ru) to p^*(P). It is concluded from above assignments that the experimental absorption peak for (n=1, 2, 3, 5) are characterized as the charge transfer from metal to ligands (MLCT), Moreover, the conjugated p(C=C) bond have significant contribution to it, thus the increase of the number of C=C bond lead to the delocalization of p electron and make the electronic absorption spectra red-shift, which is well agreed with the experimental founding by Gladysz and Bruce.To examine the effect on the excited spectrum of the solvent, the calculation also performed in CH₂Cl₂ solvent. The excitation energy blue-shifted about 8nm, when the solvent effect was taken into account. Thus, it is important for the solvent effect to such Ruthenium(II) Complexes.