On the electronic spectra and optical properties of [(η5-C5H5)(L)2M(GaMe2)] complexes (M = Fe, Ru, Os; L = CO, PMe3): A theoretical approach

A quantum chemical investigation on the structural, electronic, and optical properties of the terminal dimethylgallyl complexes of iron, ruthenium, and osmium [(η5-C5H5)(L)2M(GaMe2)] (M = Fe, Ru, Os; L = CO, PMe3) at the DFT-BP86/def2-TZVPP level is presented. In particular, geometrical parameters, electronic excitation energies, static dipole polarizabilities, anisotropy of the polarizabilities, and ground state dipole moments have been computed for considered complexes. Our computed geometry for the [(η5-C5H5)(CO)2Fe(GaMe2)] complex is in excellent agreement with the available X-ray structure data of [(η5-C5H5)(CO)2Fe(Ga(t-Bu)2)] complex. The excitation energies calculated in the time-dependent density functional theory (TD-DFT) formalism are larger for [(η5-C5H5)(CO)2M(GaMe2)] complexes as compared to PMe3 containing counterparts, with the excitation energies lying close to the visible spectrum. We found that besides the role of transition metal, the nature of ligands also affects the electronic excitation spectra of complexes under study. Moreover, based on molecular orbital analysis it is observed that depending on the nature of transition metal and ligands, different kinds of charge transfer (CT) such as MLCT, LMCT, and LLCT occur in these complexes. The difference between Kohn-Sham eigenvalues of the orbitals involved in the electronic excitations studied has also been compared with the TD-DFT data of the corresponding excitations and the remarkable results (the differences in the range of 0.05–0.22 eV) are achieved. Our results for linear optical properties reveal that upon going from M = Fe to M = Os the computed values of the mean static dipole polarizabilities and dipole moments increase and complexes become more polarized while the anisotropy of the polarizabilities shows a different pattern. Finally, for all complexes the values of electronic spatial extent, as a measure of electron density volume around the complex, have been computed and their relationship with the optical properties is discussed.