Thermodynamics of Formation of Host−Guest Supramolecular Polymers

• Published in: Journal of the American Chemical Society Vol. 128; no. 17; pp. 5728 - 5734
• Main Authors: Soto Tellini, Victor Hugo, Jover, Aida, García, Jorge Carrazana, Galantini, Luciano, Meijide, Francisco, Tato, José Vázquez
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 03.05.2006
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Thermal and thermodynamic properties; Gibbs free energy; Branched polymer; Enthalpy; Supramolecular structure; Oligoholoside; Inclusion compound; Tricyclic compound; Thermodynamic properties; Heat of formation; Macrocycle
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0572809

The interactions between three β-cyclodextrin hosts (having 1−3 binding sites) and two adamantyl guests (having 1−2 binding sites) have been studied by ITC, ROESY, static and dynamic light scattering (SLS and DLS), and AFM and TEM techniques. The enthalpy and free energy values (determined from ITC experiments) evidence that the single interaction between one binding site of the guest and one binding site of the host is independent of the number of binding sites of the interacting species. The average values are ΔH° = −26.6 ± 2.3 kJ mol-1 and ΔG° = −30.4 ± 3.2 kJ mol-1, indicating that the process is mainly enthalpy driven. In all cases, the experimental molar ratio (from ITC experiments) agrees with the expected one from the number of binding sites of both the host and guest. The formation of polymer-like entities was demonstrated by SLS, DLS, AFM, and TEM measurements. The structure of polymers is linear when both the host and the guest are ditopic entities and dendritic (or Cayley tree type) when the host and the guest have three and two binding sites, respectively.