Department of Chemistry, University of Louisville, 2320 S. Brook St, Louisville, Kentucky 40292, United States.
Inorg Chem. 2023 Feb 13;62(6):2751-2759. doi: 10.1021/acs.inorgchem.2c03868. Epub 2023 Jan 30.
In this study, a series of thiosemicarbazonato-hydrazinatopyridine metal complexes were evaluated as CO capture agents. The complexes incorporate a non-coordinating, basic hydrazinatopyridine nitrogen in close proximity to a Lewis acidic metal ion allowing for metal-ligand cooperativity. The coordination of various metal ions with (diacetyl-2-(4-methyl-thiosemicarbazone)-3-(2-hydrazinopyridine) (HL) yielded ML (M = Ni(II), Pd(II)), ML(CHOH) (M = Cu(II), Zn(II)), and [ML(PPh)]BF (M = Co(III)) complexes. The ML(CHOH) complexes reversibly capture CO with equilibrium constants of 88 ± 9 and 6900 ± 180 for Cu(II) and Zn(II), respectively. Ligand effects were evaluated with Zn(II) through variation of the 4-methyl-thiosemicarbazone with 4-ethyl (HL), 4-phenethyl (HL), and 4-benzyl (HL) derivatives. The equilibrium constant for CO capture increased to 11,700 ± 300, 15,000 ± 400, and 35,000 ± 200 for ZnL(MeOH), ZnL(MeOH), and ZnL(MeOH), respectively. Quantification of ligand basicity and metal ion Lewis acidity shows that changes in CO capture affinity are largely associated with ligand basicity upon substitution of Cu(II) with Zn(II), while variation of the thiosemicarbazone ligand enhances CO affinity by tuning the metal ion Lewis acidity. Overall, the Zn(II) complexes effectively capture CO from dilute sources with up to 90%, 86%, and 65% CO capture efficiency from 400, 1000, and 2500 ppm CO streams.
在这项研究中，一系列硫代半卡巴腙-酰肼吡啶金属配合物被评估为 CO 捕获剂。这些配合物在靠近路易斯酸性金属离子的位置引入了一个非配位的碱性酰肼吡啶氮，从而允许金属-配体协同作用。各种金属离子与（二乙酰基-2-（4-甲基-硫代半卡巴腙）-3-（2-酰肼吡啶）（HL）配位，得到 ML（M=Ni(II)，Pd(II)）、ML(CHOH)（M=Cu(II)，Zn(II)）和[ML(PPh)]BF（M=Co(III)）配合物。ML(CHOH)配合物可逆地捕获 CO，其平衡常数分别为 88±9 和 6900±180，对于 Cu(II)和 Zn(II)。通过改变 4-甲基-硫代半卡巴腙，用 4-乙基（HL）、4-苯乙基（HL）和 4-苄基（HL）衍生物对 Zn(II)进行了配体效应评价。ZnL(MeOH)、ZnL(MeOH)和 ZnL(MeOH)的 CO 捕获平衡常数分别增加到 11700±300、15000±400 和 35000±200。配体碱性和金属离子路易斯酸性的定量表明，在 Cu(II)用 Zn(II)取代时，CO 捕获亲和力的变化主要与配体碱性有关，而硫代半卡巴腙配体的变化通过调节金属离子路易斯酸性来增强 CO 亲和力。总的来说，Zn(II)配合物能够有效地从稀释源中捕获 CO，在 400、1000 和 2500 ppm CO 气流中，CO 捕获效率分别高达 90%、86%和 65%。
