In aqueous solution, the energy content of the triplet metal-to-ligand charge transfer _3MLCT. state, as deter- mined by laser-induced optoacoustic spectroscopy, for both 1:1 supercomplexes _wRu_bpy._CN.4 xPw24xane-wN6H6 x44q and wRu_bpy._CN.4xPw32xane-wN8H8x46q are similar to that for free Ru_bpy._CN.42y _223"8 kJrmol.. The reduction of the structural volume change upon formation of the 3MLCT state in the order Ru_bpy._CN.2y _14.9 mlrmol., _wRu_bpy._CN. x 4 4 Pw32xane-wN8H8x46q _5.2 mlrmol. and _wRu_bpy._CN.4 xPw24xane-wN6H6 x44q _2.5 mlrmol. is attributed to the rigidity of the macrocycle cavity. The 3MLCT state lifetime increase from 104 ns for Ru_bpy._CN.2y to 150 ns for _wRu_bpy._CN. xP 4 4 w24xane-wN6H6x44q and 182 ns for _wRu_bpy._CN.4 xPw32xane-wN8H8x46q is due to the decrease in the number of CN groups free to form hydrogen bonds with water: four, one, and none, respectively
