Hydrophobic vs. Hydrophilic: Ionic Competition in Remacemide Salt Structures

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• 作者：Gareth R. Lewis ; Gerry Steele ; Lorraine McBride ; Alastair J. Florence ; Alan R. Kennedy ; Norman Shankland ; William I. F. David ; Kenneth Shankland ; and Simon J. Teat
• 刊名：Crystal Growth & Design
• 出版年：2005
• 出版时间：March 2005
• 年：2005
• 卷：5
• 期：2
• 页码：427 - 438
• 全文大小：1096K
• 年卷期：v.5,no.2(March 2005)
• ISSN：1528-7505

文摘

Remacemide [2-amino-N-(1-methyl-1,2-diphenylethyl)-acetamide] was developed as a potentialantagonist for epilepsy, Parkinsonism, and Huntington's disease. This paper investigates hydrophilic and hydrophobicintermolecular interactions that occur within the series of crystal structures comprising remacemide 1 and six of itssalts [2 = chloride; 3 = nitrate; 4 = acetate (C₂H₃O₂^-); 5 = hydrogenfumarate (C₄H₃O₄^-); 6 = naphthalene-2-sulfonate(napsilate, C₁₀H₇O₃S^-); 7 = 1-hydroxynaphthalene-2-carboxylate (xinafoate, C₁₁H₇O₃^-)]. The hydrophilic interactionsare described through graph set analyses of the hydrogen bond motifs and networks. The lattice of 1 comprisesunidirectional, one-dimensional chains of molecules parallel to the c-axis. In 2, the cation-anion hydrogen bondingimposes a well-defined hydrophilic stratum structure on the lattice. As the cation itself is amphiphilic, a naturalconsequence of this is the creation of two-dimensional stacked layers with alternating hydrophilic and hydrophobiccharacter (lattice bilayers). This tendency to form bilayers within the lattice is also observed in structures 3-5(polar anions) and structures 6-7 (amphiphilic anions). Relatively few well-directed intermolecular interactionsare observed between aromatic rings, either in 1 or in the hydrophobic layers of 2-7. Therefore, it is concluded thatit is the hydrophilic hydrogen bond interactions that dominate the crystal packing and drive the segregation intolattice bilayers in the salt crystal structures.