Curcumin is a biologically active polyphenol and a yellow pigment extracted from turmeric. Our previous study has shown effective encapsulation of curcumin using diamide linked gamma-cyclodextrin dimers, namely 66 gamma CD(2)su and 66 gamma CD(2)ur, through cooperative 1:1 host-guest complexation. In this study, the excited-state dynamics of curcumin complexed with either 66 gamma CD(2)su or 66 gamma CD(2)ur in water are investigated using femtosecond transient absorption spectroscopy. Both 66 gamma CD(2)su-curcumin and 66 gamma CD(2)ur-curcumin complexes in water show only an excited-state absorption (ESA) band at 530 nm without any stimulated emission (SE) signals, indicating non-radiative decays as the major relaxation pathways. The ESA dynamics of 66 gamma CD(2)su-curcumin are similar to those of 66 gamma CD(2)ur-curcumin, consisting of a rapid growth component and three decay components. The growth component, which has a time constant of 0.25-0.41 ps, is assigned to solvent reorganization. The relatively fast decay components with time constants of 9.3-21.8 ps show significant deuterium isotope effect, consistent with the presence of excited-state intramolecular hydrogen atom transfer (ESIHT) of curcumin. The small-amplitude and slow decay components may be attributed to the dynamics of complexed curcumin and molecular motions due to flexibility of 66 gamma CD(2)su and 66 gamma CD(2)ur. In addition, transient absorption anisotropy measurements reveal slow rotational motions of 66 gamma CD(2)su-curcumin and 66 gamma CD(2)ur-curcumin complexes. The overall results show that complexation in 66?CD2su and 66 gamma CD(2)ur has pronounced effects on the photophysics of curcumin.