Optical and magnetic properties of the complex bis(dicyclooctatetraenyl) diuranium. A theoretical view

A systematic study on bis(dicyclooctatetraenyl)diuranium (U ₂COT ₄) has been performed using relativistic density functional theory. The molecule was calculated in four different electronic configurations and the two symmetries C ₂ and D _2h. First we considered the high-spin quintuplet ( ⁵A) state, and from this state we built the broken-symmetry configuration following Noodleman's approach. Also, the triplet state was considered as a formal interaction of both uranocene fragments in triplet and singlet states simultaneously, and finally the low-spin singlet configuration was calculated. For both symmetries the ground state of the complex was the quintuplet, and on the basis of the broken-symmetry approach a significant ferromagnetic coupling between both metals was found. Time-dependent density functional theory (TDDFT) was used to calculate the excitation energies with the GGA SAOP functional. The obtained electronic transitions are in good correlation with reported experimental values, which are found between 600 and 720 nm: 633, 658, 664, 673, 685, and 717 nm.