External and internal guest binding of a highly charged supramolecular host in water: deconvoluting the very different thermodynamics.
NMR, UV-vis, and isothermal titration calorimetry (ITC) measurements probe different aspects of competing host-guest equilibria as simple alkylammonium guest molecules interact with both the exterior (ion-association) and interior (encapsulation) of the [Ga(4)L(6)](12-) supramolecular assembly in water. Data obtained by each independent technique measure different components of the host-guest equilibria and only when analyzed together does a complete picture of the solution thermodynamics emerge. Striking differences between the internal and external guest binding are found. External binding is enthalpy driven and mainly due to attractive interactions between the guests and the exterior surface of the assembly while encapsulation is entropy driven as a result of desolvation and release of solvent molecules from the host cavity.
Sgarlata
Carmelo
C
Department of Chemistry, University of California, Berkeley and Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460, USA.
Mugridge
Jeffrey S
JS
Pluth
Michael D
MD
Tiedemann
Bryan E F
BE
Zito
Valeria
V
Arena
Giuseppe
G
Raymond
Kenneth N
KN
D001665:Binding Sites; D005708:Gallium / Q000737:chemistry*; D008024:Ligands; D046911:Macromolecular Substances / Q000737:chemistry; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
D008024:Ligands; D046911:Macromolecular Substances; D009942:Organometallic Compounds; D000644:Quaternary Ammonium Compounds; D014867:Water; D005708:Gallium