1481719-36-1Relevant articles and documents
Electrochromic platinum(II) complexes derived from azobenzene and zwitterionic quinonoid ligands: Electronic and geometric structures
Deibel, Naina,Hohloch, Stephan,Sommer, Michael G.,Schweinfurth, David,Ehret, Fabian,Braunstein, Pierre,Sarkar, Biprajit
, p. 7366 - 7375 (2013)
The ligands azobenzene (az) and the zwitterionic 4-(isopropylamino)-6- (isopropyliminio)-3-oxocyclohexa-1,4-dien-1-olate (Q) were used to synthesize the mononuclear complex [(Q-H)Pt(az-H)] (1), and the dinuclear complex [(Q-H)Pt(μ-az-2H)Pt(Q-H)] (2). Structural characterization of the complexes shows a distorted-square- planar environment around the Pt(II) centers and localization of the double bonds within the Q-H ligand on metal coordination. Furthermore, the N=N azo bond is elongated in the metal complexes in comparison to free az, owing to π back-bonding from Pt(II) to az. Complexes 1 and 2 display multiple reversible reduction steps in their cyclic voltammograms. The complexes also exhibit strong absorptions in the visible region, the position and intensity of which can be influenced by the chromophore [(Q-H)Pt]. UV-vis-near-IR spectroelectrochemical studies show that the absorption of these complexes in the visible as well as the near-IR region can be controlled by electron transfer steps. Depending on the charge state of the complexes, they are found to be either transparent in the near-IR region but strongly absorbing in the visible or vice versa, thus displaying strong electrochromic behavior. EPR spectroelectrochemical studies together with DFT calculations and comparison with the complex [(Q-H)Pd(az-H)] (3) are used to locate the site of electron transfer in these complexes and to elucidate their electronic properties in the various redox states. Complex 2 is a rare example where doubly deprotonated azobenzene acts as a bridging ligand.
