Electronic Transitions in Different Redox States of Trinuclear 5,6,11,12,17,18-Hexaazatrinaphthylene-Bridged Titanium Complexes: Spectroelectrochemistry and Quantum Chemistry.

ABSTRACT: Multinuclear transition metal complexes bridged by ligands with extended ?-electronic systems show a variety of complex electronic transitions and electron transfer reactions. While a systematic understanding of the photochemistry and electrochemistry has been attained for binuclear complexes, much less is known about trinuclear complexes such as hexaphenyl-5,6,11,12,17,18-hexaazatrinaphthylene-tristitanocene [(Cp₂ Ti)₃ HATN(Ph)₆ ]. The voltammogram of [(Cp₂ Ti)₃ HATN(Ph)₆ ] shows six oxidation and three reduction waves. Solution spectra of [(Cp₂ Ti)₃ HATN(Ph)₆ ] and of the electrochemically formed oxidation products show electronic transitions in the UV, visible and the NIR ranges. Density functional theory (DFT) and linear response time-dependent DFT show that the three formally titanium(II) centers transfer an electron to the HATN ligand in the ground state. The optically excited transitions occur exclusively between ligand-centered orbitals. The charged titanium centers only provide an electrostatic frame to the extended ?-electronic system. Complete active self-consistent field (CASSCF) calculation on a structurally simplified model compound, which considers the multi-reference character imposed by the three titanium centers, can provide an interpretation of the experimentally observed temperature-dependent magnetic behavior of the different redox states of the title compound in full consistency with the interpretation of the electronic spectra.

SUBMITTER: Markovic A 

PROVIDER: S-EPMC7756296 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature