Details

Autor(en) / Beteiligte

• Mognon, Lorenzo
• Mandal, Sukanta
• Castillo, Carmen E
• Fortage, Jérôme
• Molton, Florian
• Aromí, Guillem
• Benet-Buchhlolz, Jordi
• Collomb, Marie-Noëlle
• Llobet, Antoni

Titel

Synthesis, structure, spectroscopy and reactivity of new heterotrinuclear water oxidation catalysts

Ist Teil von

• Chemical science (Cambridge), 2016-01, Vol.7 (5), p.334-3312

Ort / Verlag

England: The Royal Society of Chemistry

Erscheinungsjahr

2016

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Four heterotrinuclear complexes containing the ligands 3,5-bis(2-pyridyl)pyrazolate (bpp − ) and 2,2′:6′,2′′-terpyridine (trpy) of the general formula {[Ru II (trpy)] 2 (μ-[M(X) 2 (bpp) 2 ])}(PF 6 ) 2 , where M = Co II , Mn II and X = Cl − , AcO − (M = Co II , X = Cl − : Ru 2 Co-Cl 2 ; M = Mn II , X = Cl − : Ru 2 Mn-Cl 2 ; M = Co II , X = AcO − : Ru 2 Co-OAc 2 ; M = Mn II , X = AcO − : Ru 2 Mn-OAc 2 ), have been prepared for the first time. The complexes have been characterized using different spectroscopic techniques such as UV-vis, IR, and mass spectrometry. X-Ray diffraction analyses have been used to characterize the Ru 2 Mn-Cl 2 and Ru 2 Mn-OAc 2 complexes. The cyclic voltammograms (CV) for all four complexes in organic solvent (CH 3 CN or CH 2 Cl 2 ) display three successive reversible oxidative waves corresponding to one-electron oxidations of each of the three metal centers. The oxidized forms of the complexes Ru 2 Co-OAc 2 and Ru 2 Mn-OAc 2 are further characterized by EPR and UV-vis spectroscopy. The magnetic susceptibility measurements of all complexes in the temperature range of 2-300 K reveal paramagnetic properties due to the presence of high spin Co( ii ) and Mn( ii ) centers. The complexes Ru 2 Co-OAc 2 and Ru 2 Mn-OAc 2 act as precatalysts for the water oxidation reaction, since the acetato groups are easily replaced by water at pH = 7 generating the active catalysts, {[Ru(H 2 O)(trpy)] 2 (μ-[M(H 2 O) 2 (bpp) 2 ])} 4+ (M = Co II : Ru 2 Co-(H 2 O) 4 ; M = Mn II : Ru 2 Mn-(H 2 O) 4 ). The photochemical water oxidation reaction is studied using [Ru(bpy) 3 ] 2+ as the photosensitizer and Na 2 S 2 O 8 as a sacrificial electron acceptor at pH = 7. The Co containing complex generates a TON of 50 in about 10 minutes (TOF i = 0.21 s −1 ), whereas the Mn containing complex only generates a TON of 8. The water oxidation reaction of Ru 2 Co-(H 2 O) 4 is further investigated using oxone as a sacrificial chemical oxidant at pH = 7. Labelled water oxidation experiments suggest that a nucleophilic attack mechanism is occurring at the Co site of the trinuclear complex with cooperative involvement of the two Ru sites, via electronic coupling through the bpp − bridging ligand and via neighboring hydrogen bonding. Four heterotrinuclear complexes containing the ligands 3,5-bis(2-pyridyl)pyrazolate (bpp − ) and 2,2′:6′,2′′-terpyridine (trpy) of the general formula {[Ru II (trpy)] 2 (μ-[M(X) 2 (bpp) 2 ])}(PF 6 ) 2 have been prepared for the first time.