Tetraarylcyclobutadiene­cyclopentadienyl­cobalt Complexes: Synthesis, Electronic Spectra, Magnetic Circular Dichroism, Linear Dichroism, and TD DFT Calculations

The known (tetraphenyl-η<sup>4</sup>-cyclobutadiene)-η<sup>5</sup>-cyclopentadienylcobalt (<b>1</b>) and a series of its new substituted derivatives have been prepared. The electronic states of a few representatives have been characterized by absorption and magnetic circular dichroism. Time-dependent density functional theory has been used to arrive at spectral assignments for several prominent low-energy bands. The absorption spectra of the radical ions of <b>1</b> have also been recorded.