包含N-己基乙二胺的质子离子液体中铜（II）离子的溶剂化结构

Solvation structure of a copper(II) ion in protic ionic liquids comprising N-hexylethylenediamine.

作者信息

Takemura Shinobu, Kawakami Sayaka, Harada Masafumi, Iida Masayasu

机构信息

Department of Chemistry, Faculty of Science, and ‡Department of Textile and Apparel Science, Faculty of Human Life and Environmental Sciences, Nara Women's University , Kita-uoya-nishi-machi, Nara 630-8506, Japan.

出版信息

Inorg Chem. 2014 Sep 15;53(18):9667-78. doi: 10.1021/ic501177t. Epub 2014 Sep 4.

DOI:10.1021/ic501177t

PMID:25188879

Abstract

The fine and dynamic structure of the copper(II) ion solvated in a protic ionic liquid (PIL) comprising monoprotonated N-hexylethylenediaminium (HHexen(+)) and bis(trifluoromethanesulfonyl)amide (Tf2N(-)) [or trifluoroacetate (TFA(-))] was determined using NMR, visible electronic, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The chelate-diamine group in the cationic unit facilitates advantageous dissolution of transition-metal salts in the present PIL. The interaction of the copper(II) ion with the chelate-diamine PIL was explored by the addition of copper(II) salts to the PIL, demonstrating competitive complexation between the ligand of the added copper(II) salt and the components of the ionic liquid to the copper(II) ion. The favorable mode of interaction of the present chelating PIL with the copper(II) ion was clarified based on a comparison of the interactions with analogous liquids, including the monoprotonated hexylaminium HHexam(Tf2N)-PIL, neat N-hexylethylenediamine (Hexen), and neat ethylenediamine (En). The coordination modes of the bis-Hexen and tris-Hexen copper(II) complexes in molecular liquids and in solids were also studied for comparison of the coordination structures around the copper(II) ion with those in the present PILs. The paramagnetic-induced relaxations derived from (13)C (ΔT(1p)(-1)) and (15)N (ΔT(2p)(-1)) NMR, the visible electronic spectra, and EXAFS analysis showed that the copper(II) ion tends to form a bis-Hexen complex in the HHexen-PIL despite the electrostatic repulsion and the fact that the counteranions are located at the axial sites, whereas in the HHexam(Tf2N)-PIL, the copper(II) ion exhibits affinity for the Tf2N anion over the protonated amines. The lifetime of the copper(II) complex formed in the PIL was determined to be ≈10(-4) s based on (13)C (ΔT(1p)(-1)) and (14)N (ΔT(2p)(-1)) NMR, which is appreciably longer than that in conventional molecular solvents.

摘要

使用核磁共振（NMR）、可见电子光谱和扩展X射线吸收精细结构（EXAFS）光谱，确定了在由单质子化的N-己基乙二胺鎓（HHexen(+)）和双（三氟甲磺酰）酰胺（Tf2N(-)）[或三氟乙酸盐（TFA(-)）]组成的质子离子液体（PIL）中溶剂化的铜（II）离子的精细动态结构。阳离子单元中的螯合二胺基团有助于过渡金属盐在当前的质子离子液体中有利地溶解。通过向质子离子液体中添加铜（II）盐，探索了铜（II）离子与螯合二胺质子离子液体的相互作用，证明了添加的铜（II）盐的配体与离子液体的成分对铜（II）离子的竞争络合作用。基于与类似液体（包括单质子化己基铵HHexam(Tf2N)-质子离子液体、纯N-己基乙二胺（Hexen）和纯乙二胺（En））相互作用的比较，阐明了当前螯合质子离子液体与铜（II）离子的有利相互作用模式。还研究了双-Hexen和三-Hexen铜（II）配合物在分子液体和固体中的配位模式，以便将铜（II）离子周围的配位结构与当前质子离子液体中的配位结构进行比较。由（13）C（ΔT(1p)(-1)）和（15）N（ΔT(2p)(-1)）核磁共振、可见电子光谱和EXAFS分析得出的顺磁诱导弛豫表明，尽管存在静电排斥且抗衡阴离子位于轴向位置，但铜（II）离子在HHexen-质子离子液体中倾向于形成双-Hexen配合物，而在HHexam(Tf2N)-质子离子液体中，铜（II）离子对Tf2N阴离子的亲和力高于质子化胺。基于（13）C（ΔT(1p)(-1)）和（14）N（ΔT(2p)(-1)）核磁共振，确定了在质子离子液体中形成的铜（II）配合物的寿命约为10^(-4) s，这明显长于传统分子溶剂中的寿命。