Synthesis, structural characterization and spectroscopic properties of cobalt complexes with the 2,6-bis(8′-quinolinyl)pyridine ligand

Crystalline Non‐Equilibrium Phase of a Cobalt(II) Complex with Tridentate Ligands

“…An exception seems to be the dcpp ligand [dcpp, 2,6‐bis(2‐carboxypyridyl)pyridine], which has only shown meridional coordination in M(dcpp) 2 complexes so far 3h,5,6. With 3d transition metal ions such as low‐spin Fe II ,5,6 high‐spin Co II ,7,8 or Cu II ,9 ligand substitution is fast, and only the thermodynamically preferred meridional products can be observed (Scheme ). The [Cu(ddpd) 2 ] 2+ complex is fluxional at room temperature in the solid state, revealing a doubly degenerate Jahn–Teller distortion motion involving all terminal pyridine donors 9.…”

“… Meridionally coordinated [M(tridentate) 2 ] 2+ complexes with flexible six‐membered chelate rings 3,5–8…”

Dye‐Sensitized Solar‐Cell Performance of a Cobalt(III/II) Redox Mediator with the 2,6‐Bis(8‐quinolinyl)pyridine Ligand

“…The visible absorption properties of [Co(bqp) 2 ] n ( n = 2+ or 3+) are relatively weak, which favour very much their application as a redox mediator in a DSSC. A comprehensive analysis of their electronic assignments has recently been communicated 16. To summarize, both complexes [Co(bqp) 2 ] n ( n = 2+ or 3+) exhibit intense absorptions in the UV region assigned to ligand‐centered π–π* transitions.…”

“…While it is difficult to assign a molecular basis for this increased Pt→Co III charge‐transfer resistance, one possibility may be a greater reorganization energy for the [Co(bqp) 2 ] 3+/2+ redox couple relative to that of [Co(tpy) 2 ] 3+/2+ . This is likely a consequence of the ideal octahedral geometry observed for the d 6 [Co(bqp) 2 ] 3+ oxidation state, which disfavors the imposed Jahn–Teller distortion upon reduction to the d 7 [Co(bqp) 2 ] 2+ species 16…”

“…General Remarks: The MK‐2 dye was purchased from Sigma Aldrich and used as received. The complexes [Co(tpy) 2 ](PF 6 ) 2 , [Co(tpy) 2 ](PF 6 ) 3 , [Co(bqp) 2 ](PF 6 ) 2 , and [Co(bqp) 2 ](PF 6 ) 3 were prepared according to previous literature reports 16,21. All solvents were of spectroscopic grade and used as received.…”