Acar Mert, Tatini Duccio, Ninham Barry W, Lo Nostro Pierandrea
Department of Chemistry "Ugo Schiff" and CSGI, University of Florence, 50019 Sesto Fiorentino, Italy.
Department of Biotechnologies, Chemistry and Pharmacy, University of Siena, 53100 Siena, Italy.
Molecules. 2025 Jan 15;30(2):323. doi: 10.3390/molecules30020323.
Specific ion effects are widespread and have been studied for over a century, yet they remain poorly understood. Terms like "kosmotropes" and "chaotropes" are convenient rules of thumb but the frequent reversal of the Hofmeister series implies their limitations. Polarizability is often used to classify ions, with kosmotropes considered low in polarizability and chaotropes high. However, for polyatomic ions, this framework becomes misleading. The anisotropic nature of polarizability in polyatomic ions plays a decisive role in shaping their behavior. In this work, we study pseudohalides (KOCN, KSCN, and KSeCN) aqueous solutions to explore these effects. We evaluate properties of these anions through experimental measurements of conductivity, density, viscosity, infrared spectra, and polarizability. Our results demonstrate that, even for linear isoelectronic polyatomic ions, the anisotropy of polarizability governs their hydration behavior.
特定离子效应广泛存在，且已被研究了一个多世纪，但人们对它们的理解仍然很有限。“促溶剂”和“离液剂”等术语是方便的经验法则，但霍夫迈斯特序列的频繁反转表明了它们的局限性。极化率常被用于对离子进行分类，促溶剂被认为极化率低，离液剂极化率高。然而，对于多原子离子，这个框架会产生误导。多原子离子极化率的各向异性在塑造其行为方面起着决定性作用。在这项工作中，我们研究了拟卤化物（氰酸钾、硫氰酸钾和硒氰酸钾）水溶液以探究这些效应。我们通过对电导率、密度、粘度、红外光谱和极化率的实验测量来评估这些阴离子的性质。我们的结果表明，即使对于线性等电子多原子离子，极化率的各向异性也决定了它们的水合行为。
