Chiroptical Properties of Mixed-Ligand Ruthenabenzene Complex

The theoretical study of reaction mechanism and relationship between chiral configuration and property of chiral ruthenium complexes is an important topic. In this work, the chiroptical properties of the mixed. ligand ruthenabenzene complex [RuBen(PPh3)(2)(Phen) (L - Cys)](2+) (Phen=phenanthroline, L-Cys=L - cysteine) have been explored using the hybrid density functional theory (DFT). The geometrical and electronic structures and subse. quent frequency verifications were calculated using the B3LYP method with the mixed basis set: the ECP28MWB pseudopotential with its (8s7p6d2f)/[6s5p3d2f] valence basis set for ruthenium, and 6. 311G(d) for other atoms. Based on these, the excited energies, rotational and oscillator strengths, as well as the electronic circular dichroism (ECD) spectra, were then calculated employing the time.dependent DFT method with the same functional and basis set. In all cases, solvent (water) effects were included using the polarized continuum model (PCM). Additionally, the intricate exciton. splitting pattern in the short wavelength region was analyzed using the exciton chirality method (ECM). The calculated ECD spectra were in good agreement with the observed ones as far as their band shape, signs, and relative intensities were concerned. The lambda/delta configurations at the octahedral core dominate the distribu. tion of the ECD curves, and the lambda/delta twists of the L-Cys rings only affect the relative intensities of the absorption bands, while the contributions of the R/S chiral carbon atoms are negligible. The absorption bands above 340 nm are characterized by the pi ->pi* transitions mixed with some metal. centered d -> d transitions. The two pairs of ECD bands below 340 nm with clearly different intensities could be assigned to the classical (the strong one) and nonclassical ( the weak one) exciton coupling, respectively. Both show a positive exciton. splitting pattern for the.. configuration, which could be used as a criterion to determine the absolute configurations of similar complexes. Additionally, comparing with mixed. ligand inorganic ruthenium complexes reveals the similarities and differences in their chiroptical properties.