de Palo Alice, La Ganga Giuseppina, Nastasi Francesco, Guelfi Massimo, Bortoluzzi Marco, Pampaloni Guido, Puntoriero Fausto, Campagna Sebastiano, Marchetti Fabio
Università di Pisa, Dipartimento di Chimica e Chimica Industriale, Via G. Moruzzi 13, I-56124 Pisa, Italy.
Dalton Trans. 2020 Mar 14;49(10):3341-3352. doi: 10.1039/c9dt04815d. Epub 2020 Feb 27.
Two mononuclear Ru(ii) complexes, i.e. [RuCl(κN-terpy)(κN-dpp)]PF ([1]PF; terpy = 2,2':6',2''-terpyridine; dpp = 2,3-bis(2'-pyridyl-pyrazine) and [RuCl(κN-tpm)(κN-dpp)]Cl ([2]Cl; tpm = tris(1-pyrazolyl)methane), and one dinuclear complex, i.e. [RuCl(κN-tpm)(μ-κN:κN-dpp)Ru(κN-bpy)][PF] ([3][PF]; bpy = 2,2'-bipyridine), have been synthesized and their water oxidation catalytic properties have been investigated. A combined DFT and experimental (Cl NMR and conductivity measurements) study aimed to elucidate the nature of [1] and [2] in aqueous solution has also been performed, indicating that one water molecule is allowed to enter the first coordination sphere of [2] in the ground state, replacing one tpm nitrogen. Conversely, in the case of [1], water coordination, assumed to be needed for the water oxidation process, presumably occurs following the oxidation of the metal. For all complexes, a catalytic wave has been detected in acetonitrile/water 1 : 1 (v/v) solution in the range 1.4-1.7 V vs. SCE. In all cases, water oxidation (investigated at pH < 8) takes place initially via a proton-coupled two-electron, two-proton process with the formation of an Ru(iv)[double bond, length as m-dash]O moiety, followed by one electron oxidation and water nucleophilic attack. The TON and TOF values (within the range of 16-33 and 1.3-2.2 h, respectively) of the complexes are higher than those of the benchmark [Ru(LLL)(LL)(OH)]-type species (LLL and LL are tridentate and bidentate polypyridine ligands, respectively), which is [Ru(terpy)(bpm)(OH)].
已合成了两种单核钌（II）配合物，即[RuCl(κN - terpy)(κN - dpp)]PF（[1]PF；terpy = 2,2':6',2'' - 三联吡啶；dpp = 2,3 - 双（2'-吡啶基 - 吡嗪））和[RuCl(κN - tpm)(κN - dpp)]Cl（[2]Cl；tpm = 三（1 - 吡唑基）甲烷），以及一种双核配合物，即[RuCl(κN - tpm)(μ - κN:κN - dpp)Ru(κN - bpy)][PF]（[3][PF]；bpy = 2,2'-联吡啶），并研究了它们的水氧化催化性能。还进行了一项结合密度泛函理论（DFT）和实验（氯核磁共振和电导率测量）的研究，旨在阐明[1]和[2]在水溶液中的性质，结果表明在基态下一个水分子能够进入[2]的第一配位层，取代一个tpm氮原子。相反，对于[1]而言，水配位被认为是水氧化过程所必需的，大概是在金属氧化之后发生。对于所有配合物，在相对于饱和甘汞电极（SCE）为1.4 - 1.7 V的乙腈/水1∶1（v/v）溶液中检测到了催化波。在所有情况下，水氧化（在pH < 8时进行研究）最初通过质子耦合的双电子、双质子过程发生，形成一个Ru（IV）=O部分，随后是单电子氧化和水的亲核进攻。这些配合物的总氧化数（TON）和氧化数变化频率（TOF）值（分别在16 - 33和1.3 - 2.2 h范围内）高于基准的[Ru(LLL)(LL)(OH)]型物种（LLL和LL分别是三齿和双齿多吡啶配体），即[Ru(terpy)(bpm)(OH)]。
