We have studied the photodissociation and recombination dynamics of diatomic anions in size-selected clusters by using simple model systems. The main purpose of the study is to provide a theoretical background for a better understanding of the salient features of the charge transfer and nonadiabatic transitions involved in the dynamics of solvated molecular ions. Calculations have been performed on the photodissociation and recombination of the model diatomic anion X-2(-) embedded in N2O and CO2 clusters. The homonuclear diatomic anion is modeled as one-electron system consisting of two identical nuclei and an extra electron. The nuclear and electronic dynamics of X-2(-) are treated quantum mechanically, while the motions of the solvent molecules are described by classical dynamics. Nonadiabatic theoretical calculations, in which the electronic and the nuclear dynamics are treated simultaneously, can reveal the importance of nonadiabatic effects by including intrinsically all electronic states. It is found that extensive nonadiabatic transitions between ground and excited electronic states are involved in the dynamics of X-2(-) in molecular clusters. It is suggested that changes in anion electronic structures and corresponding charge switching can lead to a multitude of pathways for dissociation-recombination dynamics. The results of the present study illustrate the microscopic details of the electronically nonadiabatic processes which control the photodissociation dynamics of molecular ions in clusters.