We present a new method to study position- dependent, anisotropic diffusion tensors inside spherically confined systems—a geometry that is common to many chemical nanoreactors. We use this method to elucidate the surprisingly rich solvent dynamics of confined water. The spatial variation of the strongly anisotropic diffusion predicted by the model agrees with the results of explicit molecular dynamics simulations. The same approach can be directly transferred to the transport of solutes to and from reaction sites located at nanoreactor interfaces. We com- plement our study by a detailed analysis of wa- ter hydrogen bond kinetics, which is intimately coupled to diffusion. Despite the inhomogene- ity in structure and translational dynamics in- side our nanocages, a single set of well-defined rate constants is sufficient to accurately describe the kinetics of hydrogen bond breaking and for- mation. We find that once system size effects have been eliminated, the residence times of wa- ter molecules inside the coordination shell of a hydrogen bond partner are well correlated to average diffusion constants obtained from the procedure above
