UV/Vis absorption data of (E)-4-(2-[5-{4,4,5,5-tetramethyl-1,3,2-dioxaborolane-2-yl}thiene-2-yl]vinyl)-2-(dicyano-methylene)-3-cyano-5,5-dimethyl-2,5-dihydrofuran (ThTCF) as a solvatochromic probe is applied to examine the anion coordination strength (e.g. of N(CN)₂, BF₄, PF₆, N(Tf)₂, CF₃COO) as a function of the cation structure of ionic liquids. Several 1-n-alky-3-methylimidazolium- and tetraalkylammonium CH₃-NR₃⁺-based ILs with different n-alkyl chain lengths (R = –C₄H₉, –C₆H₁₁, –C₈H₁₇, –C₁₀H₂₁) are considered. UV/Vis absorption data of ThTCF show subtle correlations with hydrogen bond accepting (HBA) ability-related measurands such as Kamlet–Taft β, Freire's E_HB, and Laurence β₁ parameter as a function of anion and cation structure. The different influence of the n-alkyl chain length of imidazolium- and tetraalkylammonium-based ILs on the dipolarity and HBA strength is confirmed by comparison with the ¹⁴N isotropic hyperfine coupling constants (A_iso) of a positively (CATI) and negatively charged spin probe (TSKCr) of TEMPO-type [(2,2,6,6-tetramethylpiperidin-1-yl)oxyl] and quantum chemically derived dipoles of the cations. The A_iso values correlate with the absorption energy of ThTCF and E_HB, but in different ways depending on the anion or charge of the spin probe. In a final discussion of the β, E_HB, and β₁ scales in relation to ThTCF, the importance of the molar concentration N of ionic liquids for the physical significance of the respective parameters is discussed.

中文翻译：

---

阳离子结构对离子液体碱性极性的影响

( E )-4-(2-[5-{4,4,5,5-tetramethyl-1,3,2-dioxaborolane-2-yl}thiene-2-yl]vinyl)-的UV/Vis吸收数据2-(二氰基-亚甲基)-3-氰基-5,5-二甲基-2,5-二氢呋喃 ( ThTCF ) 作为溶剂致变色探针用于检测阴离子配位强度 (例如N(CN) ₂ , BF ₄ , PF ₆、N(Tf) ₂、CF ₃ COO) 作为离子液体的阳离子结构的函数。几个1- Ñ -alky -3- methylimidazolium-和四烷基铵CH ₃ -NR ₃ ⁺基离子液体具有不同ñ -烷基链长度（R = -C ₄ H ^ ₉, –C ₆ H ₁₁ , –C ₈ H ₁₇ , –C ₁₀ H ₂₁ ) 被考虑。ThTCF 的UV/Vis 吸收数据显示与氢键接受 (HBA) 能力相关的测量值（如 Kamlet-Taft β、Freire 的E _HB和 Laurence β ₁参数作为阴离子和阳离子结构的函数）之间存在微妙的相关性。所述的不同的影响Ñ imidazolium-的烷基链长和基于四烷基铵，离子液体在偶极性和HBA强度通过与比较确认^14个Ñ各向同性超精细耦合常数（甲_iso ) 正 ( CATI ) 和带负电的 TEMPO 型 [(2,2,6,6-四甲基哌啶-1-基)氧基] 的自旋探针 ( TSKCr ) 和阳离子的量子化学衍生偶极子。的甲_异值与吸收能量相关ThTCF和ë _HB，但以不同的方式取决于自旋探头的阴离子或电荷。在与ThTCF相关的β、 E _HB和β ₁尺度的最后讨论中，摩尔浓度N的重要性 离子液体对于各个参数的物理意义进行了讨论。