In this work, we demonstrate the fundamental relationships between stability constants and periodic, acid–base, and structural parameters for complexes of some 1,3-diketones. The four analogues of hexafluoroacetylacetone—2-thenoyltrifluoroacetone, 2-furoyltrifluoroacetone, benzoyltrifluoroacetone, and 2-naphthyltrifluoroacetone—have been studied as chelating ligands for 16 rare-earth metals (Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) in aqueous solutions. Systems have been investigated spectrophotometrically using a multiwave nonlinear least-squares regression algorithm for data processing. Conditional stability constants were obtained for a wide pH region (2.0–5.4) at constant ionic strength (I = 0.5 M, NaCl). To receive the apparent (“true”) equilibrium parameters, acid–base and keto–enol characteristics of the studied ligands have been described and revised for specific conditions. Dissociation constants were obtained in citrate–phosphate buffer media and protonation parameters were received in concentrated hydrochloric acid by the Cox–Yates method. The apparent formation constants for monocomplex species were obtained as thermodynamic invariants (depend only on the temperature) for each ligand and lie from 4.2 to 12.7 logarithmic units. Although the studied ligands have similar values of pK_a, the stabilities of their complexes vary considerably. Systematic analysis of 64 apparent stability constants demonstrates that the force of interaction between the metals and nonsymmetric β-diketones increases as 2-furoyltrifluoroacetone < 2-thenoyltrifluoroacetone < benzoyltrifluoroacetone < 2-naphthyltrifluoroacetone. The studied ligands display varying degrees of the correlation between the periodic parameters and formation constants. Naphthyltrifluoroacetone and its complexes with heavy lanthanides exhibit a clear trend in properties with increasing ionic potential. In general, the received set of data can be described from purely electrostatic grounds within the framework of the periodic law. Spectral, keto–enol, acid–base, and complexing properties were reproduced using density functional theory modeling and explain some of the regularities discovered.

中文翻译：

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稀土金属与一些全氟β-二酮的相互作用

在这项工作中，我们证明了稳定常数与某些1,3-二酮配合物的周期性，酸碱和结构参数之间的基本关系。已经研究了六氟乙酰丙酮的四个类似物-2-壬基三氟丙酮，2-呋喃基三氟丙酮，苯甲酰基三氟丙酮和2-萘基三氟丙酮-作为16种稀土金属（Sc，Y，La，Ce，Pr，Nd，Sm，Eu， Gd，Tb，Dy，Ho，Er，Tm，Yb和Lu）在水溶液中。使用多波非线性最小二乘回归算法进行分光光度法研究系统进行数据处理。在恒定的离子强度下，在宽pH范围（2.0–5.4）下获得了条件稳定性常数（I＝ 0.5M，NaCl）。为了获得表观（“真实”）平衡参数，已对所研究的配体的酸碱和酮-烯醇特性进行了描述并针对特定条件进行了修改。在柠檬酸-磷酸盐缓冲液中获得了解离常数，并通过考克斯-耶茨方法在浓盐酸中获得了质子化参数。对于每个配体，获得了单络合物物种的表观形成常数，作为热力学不变量（仅取决于温度），其对数单位为4.2至12.7。尽管研究的配体具有相似的p K _a值，其配合物的稳定性差异很大。对64个表观稳定常数的系统分析表明，金属与非对称β-二酮之间的相互作用力随着2-呋喃基三氟丙酮<2-壬基三氟丙酮<苯甲酰基三氟丙酮<2-萘基三氟丙酮的增加而增加。所研究的配体显示出周期性参数和形成常数之间不同程度的相关性。萘基三氟丙酮及其与重镧系元素的配合物表现出明显的趋势，即离子电势增加。通常，可以在周期定律的框架内从纯静电基础描述接收到的数据集。光谱，酮-烯醇，酸碱，