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首页> 外文期刊>Chemistry: A European journal >Molecular Switch Triggered by Solvent Polarity: Synthesis, Acid-Base Behavior, Alkali Metal Ion Complexation, and Crystal Structure
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Molecular Switch Triggered by Solvent Polarity: Synthesis, Acid-Base Behavior, Alkali Metal Ion Complexation, and Crystal Structure

机译：溶剂极性触发的分子开关：合成，酸碱行为，碱金属离子络合和晶体结构

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摘要

The synthesis and characterization of the new tetraazamacrocycle L, bearing two 1,1'-bis(2-phenol) groups as side-arms, is reported. The basicity behavior and the binding properties of L toward alkali metal ions were determined by means of potentiometric measurements in ethanol/wate 50:50 (v/v) solution (298.1 (+-) 0.1 K, I = 0.15 mol dm~(-3)). The anionic H_(-1)L~- species can be obtained in strong alkaline solution, indicating that not all of the acidic protons of L can be removed under the experimental conditions used. This specific behaves as a tetraprotic base (log K_1 = 11.22, log K_2 = 9.45, log K_3 = 7.07, log K_4 = 5.08), and binds alkali metal ions to form netural [MH_(-1)L] complexes with the following stability constants: log K_Li = 3.92, log K_Na = 3.54, log K_K = 3.29, log K_Cs = 3.53. The arrangement of the acidic protons in the H_(-1)L~- species depends on the polarity of the solvents used, and at least one proton switches from the amine moiety to the aromatic part upon decreasing the polarity of the solvent. In this way two different binding areas, modulated by the polarity of solvents, are possible in L. One area is preferred by alkali metal ions in polar solvents, the second one is preferred in solvents with low polarity. Thus, the metal ion can switch from one location to the otherin the ligand, modulated by the polarity of the environment. A strong hydrogen-bonding network should preorganize the ligand for coordination, as confirmed by MD simulation. The crystal structure of the [Na(H_(-1)L)]·CH_3CN complex (space group P2_1/c, a = 12.805(1), b = 20.205(3), c = 14.170(2)A, beta = 100.77(1)°, V = 3601.6(8)A~3, Z = 4, R = 0.0430, wR2 = 0.1181), obtained using CH_2Cl_2/CH_3CN as mixed solvent, supports this last aspect and shows one of the proposed binding areas.
机译：报道了带有两个1,1'-双（2-苯酚）基团作为侧臂的新四氮杂大环L的合成和表征。通过在乙醇/水50:50（v / v）溶液（298.1（+-）0.1 K，I = 0.15 mol dm〜（-）中的电位计测量来确定L对碱金属离子的碱性行为和结合特性。 3））。可以在强碱性溶液中获得阴离子H _（-1）L〜-物种，这表明在所使用的实验条件下，并非可以去除L的所有酸性质子。该特定分子表现为四性质子碱（log K_1 = 11.22，log K_2 = 9.45，log K_3 = 7.07，log K_4 = 5.08），并与碱金属离子结合形成具有以下稳定性的网状[MH _（-1）L]络合物常数：log K_Li = 3.92，log K_Na = 3.54，log K_K = 3.29，log K_Cs = 3.53。 H _（-1）L-物种中酸性质子的排列取决于所用溶剂的极性，并且在降低溶剂的极性时，至少一个质子从胺部分切换为芳族部分。这样，在L中可能会出现两个受溶剂极性调节的不同结合区域。在极性溶剂中，一个区域最好是碱金属离子，在极性低的溶剂中，另一个区域是优选的。因此，金属离子可以在配体中从一个位置切换到另一个位置，该位置受环境极性的调节。如MD模拟所证实的，强大的氢键网络应使配体预先组织成配位基。 [Na（H _（-1）L）]·CH_3CN配合物的晶体结构（空间群P2_1 / c，a = 12.805（1），b = 20.205（3），c = 14.170（2）A，β=使用CH_2Cl_2 / CH_3CN作为混合溶剂获得的100.77（1）°，V = 3601.6（8）A〜3，Z = 4，R = 0.0430，wR2 = 0.1181）支持这一最后方面并显示了拟议的结合区域之一。

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