Dinuclear Radical Tin(IV) Complex Bearing Differently Charged o-Iminoquinone Ligands and Stabilized by a Dianionic Tetrazine Bridge

A dinuclear radical complex of tin(IV) based on differently charged o-iminoquinone ligands and 2-bipyridyl-tetrazine is prepared and characterized. It is shown that the tetrazine bridge in the [(dippimSQ) Sn(dippAP)]2bptz complex is stabilized in the dianionic state, and this is confirmed by XRD. The diradical nature of the complex is determined by EPR and XRD data. Particular attention is paid to the analysis of redox states in the system containing two types of redox-active ligands in different oxidation states. The electronic absorption spectrum demonstrates a series of electronic transitions in the 700-1050 nm region due to the charge transfer between organic ligands. The obtained experimental data agree well with the results of density functional theory (DFT) quantum chemical calculations.