Deprotonation/protonation of coordinated secondary thioamide units of pincer ruthenium complexes: Modulation of voltammetric and spectroscopic characterization of the pincer complexes
作者:Takuya Teratani、Take-aki Koizumi、Takakazu Yamamoto、Koji Tanaka、Takaki Kanbara
DOI:10.1039/c0dt01283a
日期:——
New pincer ruthenium complexes, [Ru(SCS)(tpy)]PF6 (1) (SCS = 2,6-bis(benzylaminothiocarbonyl)phenyl), tpy = 2,2′:6′,2′'-terpyridyl) and [Ru(SNS)(tpy)]PF6 (2) (SNS = 2,5-bis(benzylaminothiocarbonyl)pyrrolyl), having κ3SCS and κ3SNS pincer ligands with two secondary thioamide units were synthesized by the reactions of [RuCl3(tpy)] with N,N'-dibenzyl-1,3-benzenedicarbothioamide (L1) and N,N'-dibenzyl-2,5-1H-pyrroledicarbothioamide (L2), respectively, and their chemical and electrochemical properties were elucidated. The structure of 1 was determined by X-ray crystallography. The complexes 1 and 2 showed a two-step deprotonation reaction by treatment with 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU), and the addition of DBU led to a shift of the metal-centered redox couples to a lower potential by 720 and 550 mV, respectively. The di-deprotonated complexes were also studied by 1H-NMR and UV-vis spectroscopy. The addition of methanesulfonic acid (MSA) to the di-deprotonated complexes enabled the recovery of 1 and 2, indicating that the thioamide moiety underwent a reversible deprotonation-protonation process, which resulted in regulating the redox potentials of the metal center. The Pourbaix diagram of 1 revealed that 1 underwent a one-proton/one-electron transfer process in the pH range of 5.83–10.35, and a two-proton/one-electron process at a pH of over 10.35, indicating that the deprotonation/protonation process of the complexes is related to proton-coupled electron transfer (PCET).
新的钳形钌配合物[Ru(SCS)(tyy)]PF6 (1)(SCS = 2,6-双(苄氨基硫代羰基)苯基,tyy = 2,2′:通过[RuCl3(typy)]与 N、N'-二苄基-1,3-苯二硫代甲酰胺(L1)和 N,N'-二苄基-2,5-1H-吡咯烷二硫代甲酰胺(L2)反应合成了[RuCl3(tpy)],并阐明了它们的化学和电化学性质。通过 X 射线晶体学确定了 1 的结构。配合物 1 和 2 经 1,8-二氮杂双环[5,4,0]十一-7-烯(DBU)处理后发生了两步去质子化反应,DBU 的加入导致以金属为中心的氧化还原偶分别向低电位移动了 720 mV 和 550 mV。二去质子化配合物还通过 1H-NMR 和 UV-vis 光谱进行了研究。在二去质子化的配合物中加入甲磺酸(MSA)后,1 和 2 得以恢复,这表明硫酰胺分子经历了可逆的去质子化-质子化过程,从而调节了金属中心的氧化还原电位。1 的 Pourbaix 图显示,1 在 pH 值为 5.83-10.35 的范围内经历了一个质子/一个电子转移过程,而在 pH 值超过 10.35 时则经历了一个双质子/一个电子转移过程,这表明配合物的去质子化/质子化过程与质子耦合电子转移(PCET)有关。