Recent experimental results on negatively charged formic acid clusters generated by the impact of Cf-252 fission fragments on icy formic acid target are compared to quantum mechanical calculations. Structures for the clusters series, (HCOOH)nOH(-), where 2 <= n <= 4, are proposed based on ab initio electronic structure methods. The results show that cluster growth does not have a regular pattern of nucleation. A stability analysis was performed considering the commonly defined stability function. Temporal behavior of the clusters was evaluated by Born-Oppenheimer molecular dynamics to check the mechanism that provides cluster stability. The evaluated temporal profiles indicate the importance of hydrogen atom migration between the formic acid moieties in maintaining the stability of the structures and the water formation due to hydrogen abstraction by the hydroxyl approach.