The electronic effects resulting from noncovalent host-guest interactions between calixarene and a ruthenium dimer, [Ru3O(OAc) 6(CO)(ppy)2-μ-pz (ppy = 4-phenyl pyridine, pz = pyrazine), are presented. The noncovalent interaction is between the calixarene and the ppy ligands of the dimer. The dimer can bind 2 equiv of calixarene. The complex [Ru3O(OAc)6(CO)(ppy)] 2-μ-pz forms a highly stable mixed valence ion with strong electronic coupling between the two Ru3 clusters. The strength of the electronic interaction is found to be moderated by calixarene binding. Addition of calixarene to the mixed valence ion causes the electronic coupling to decrease. The binding of calixarene is found to be cooperative. The origins of cooperative binding are developed in terms of the potential energy surfaces associated with the symmetric and asymmetric mixed valence ion. In particular, it is found that symmetry breaking (through the binding of a single calixarene) destabilizes the mixed valence state. Restoration of symmetry (through the binding of a second calixarene) increases the stability of the mixed valence ion and provides an additional driving force for the binding of the second calixarene.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry