The H2S+ ligand was used to study the first proton-transfer (PT1) process in microsolvation and aqueous environments. The average time scale of PT1 of (H2O)(3)(+) clusters (Delta t(PT1) = 22.8 fs) was notably shorter than that of (H2O)(2)H2S+ clusters at 79.5 fs. Compared with cationic-water clusters, the smaller potential energy gain observed in the H2S-containing clusters was considered the dominant factor for such slow PT1 dynamics. Delta t(PT1) of the [H2S](+)(aq) at 106.5 fs was significantly longer than the (H2O)(2)H2S+ clusters. The stabilization effect resulting from the solvent reorientation and formation of H2S+ center dot center dot center dot OH2 hemibond interactions was responsible for this delay. (C) 2015 Elsevier B.V. All rights reserved.