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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >[CuCl_3]~- and [CuCl_4]~(2-) hydrates in concentrated aqueous solution: A density functional theory and ab initio study
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[CuCl_3]~- and [CuCl_4]~(2-) hydrates in concentrated aqueous solution: A density functional theory and ab initio study

机译：[CuCl_3]〜-和[CuCl_4]〜（2-）在浓水溶液中水合：密度泛函理论和从头算

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摘要

In this work, structures and thermodynamic properties of [CuCl _3]~- and [CuCl_4]~(2-) hydrates in aqueous solution were investigated using density functional theory and ab initio methods. Contact ion pair (CIP) and solvent-shared ion pair (SSIP) structures were both taken into account. Our calculations suggest that [CuCl _3(H_2O)-n]~- clusters might favor a four-coordinated CIP structure with a water molecule coordinating with the copper atom in the equatorial position for n = 3 and 4 in aqueous solution, whereas the four-coordinated SSIP structure with one chloride atom dissociated becomes more stable as n increases to 5. For the [CuCl_4]~(2-) cluster, the four-coordinated tetrahedron structure is more stable than the square-planar one, whereas for [CuCl_4(H_2O) _n]~(2-) (n ≥ 1) clusters, it seems that four-coordinated SSIP structures are slightly more favorable than CIP structures. Our calculations suggest that Cu~(2+) perhaps prefers a coordination number of 4 in CuCl_2 aqueous solution with high Cl~- concentrations. In addition, natural bond orbital (NBO) calculations suggest that there is obvious charge transfer (CT) between copper and chloride atoms in [CuCl_x]~(2-x) (x = 1-4) clusters. However, compared with that in the [CuCl_2]~0 cluster, the CT between the copper and chloride atoms in [CuCl_3]~- and [CuCl_4] ~(2-) clusters becomes negligible as the number of attached redundant Cl- ions increases. This implies that the coordination ability of Cl- is greatly weakened for [CuCl_3]~- and [CuCl_4]~(2-) clusters. Electronic absorption spectra of these different hydrates were obtained using long-range-corrected time-dependent density functional theory. The calculated electronic transition bands of the four-coordinated CIP conformer of [CuCl_3(H_2O) _n]~- for n = 3 and 4 are coincident with the absorption of [CuCl_3]~-(aq) species (～284 and 384 nm) resolved from UV spectra obtained in CuCl_2 (ca. 10~(-4) mol·kg ~(-1)) + LiCl (>10 mol·kg~1) solutions, whereas the calculated bands of [CuCl_3(H_2O)_n]~- in their most stable configurations are not when n = 0 - 2 or n > 4, which means that the species [CuCl_3]~-(aq) exists in those CuCl_2 aqueous solutions in which the water activity is neither too low nor too high. The calculated bands of [CuCl_4(H_2O) _n]~(2-) clusters correspond to the absorption spectra (～270 and 370 nm) derived from UV measurements only when n = 0, which suggests that [CuCl_4]~(2-)(aq) species probably exist in environments in which the water activity is quite low.
机译：在这项工作中，使用密度泛函理论和从头算方法研究了[CuCl_3]〜-和[CuCl_4]〜（2-）水合物的结构和热力学性质。都考虑了接触离子对（CIP）和溶剂共享离子对（SSIP）结构。我们的计算表明，[CuCl _3（H_2O）-n]〜-团簇可能更倾向于四配位的CIP结构，其中水分子与赤道位置的铜原子配位，水溶液中n = 3和4，而四n增至5时，具有一个离解的氯原子的四配位SSIP结构变得更稳定。对于[CuCl_4]〜（2-）团簇，四配位四面体结构比方平面四面体更稳定，而对于[CuCl_4] （H_2O）_n]〜（2-）（n≥1）簇，似乎四配位的SSIP结构比CIP结构更有利。我们的计算表明，在高Cl〜-浓度的CuCl_2水溶液中，Cu〜（2+）的配位数为4。此外，自然键轨道（NBO）计算表明，[CuCl_x]〜（2-x）（x = 1-4）簇中的铜和氯原子之间存在明显的电荷转移（CT）。然而，与[CuCl_2]〜0团簇相比，[CuCl_3]〜-和[CuCl_4]〜（2-）团簇中铜和氯原子之间的CT随着可连接的多余Cl-离子数量的增加而变得可忽略不计。 。这意味着对于[CuCl_3]〜-和[CuCl_4]〜（2-）团簇，Cl-的配位能力大大减弱。使用远程校正的随时间变化的密度泛函理论获得了这些不同水合物的电子吸收光谱。对于n = 3和4，计算出的[CuCl_3（H_2O）_n]〜-的四配位CIP构象异构体的电子跃迁带与[CuCl_3]〜-（aq）物种的吸收（〜284和384 nm）一致。从在CuCl_2（约10〜（-4）mol·kg〜（-1））+ LiCl（> 10 mol·kg〜1）溶液中获得的紫外光谱解析，而[CuCl_3（H_2O）_n]的计算谱带当n = 0-2或n> 4时，〜-不是最稳定的构型，这意味着[CuCl_3]〜-（aq）物种存在于水分活度既不太低也不不太高的CuCl_2水溶液中高。仅在n = 0时，[CuCl_4（H_2O）_n]〜（2-）团簇的计算谱带对应于从UV测量得出的吸收光谱（〜270和370 nm），这表明[CuCl_4]〜（2-） （aq）物种可能存在于水分活度相当低的环境中。

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