Excited-state hydrogen-atom transfer (ESHAT) along a hydrogen-bonded solvent wire occurs for the Supersonically cooled n = 3 ammonia-wire Cluster attached to the scaffold molecule 7-hydroxyquinoline (7HQ) [Tanner, C.; et a]. Science 2003, 302, 1736]. Here, we study the analogous three-membered solvent-wire clusters 7HQ center dot(NH3)(n)center dot(H2O)(m), n + m = 3, using resonant two-photon ionization (R2PI) and UV-UV hole-burning spectroscopies. Substitution of H2O for NH3 has a dramatic effect on the excited-state H-atom transfer: The threshold for the ESHAT reaction is similar to 200 cm(-1) for 7HQ center dot(NH3)3, similar to 350 cm(-1) for both isomers of the 7HQ center dot(NH3)(2)center dot H2O cluster, and similar to 600 cm(-1) for 7HQ center dot NH(3)center dot(H2O)(2) but increases to similar to 2000 cm(-1) for the pure 7HQ center dot(H2O)(3) water-wire cluster. To understand the effect of the chemical composition of the solvent wire on the H-atom transfer, the reaction profiles of the low-lying electronic excited states of the n = 3 pure and mixed solvent-wire Clusters are calculated with the configuration interaction singles (CIS) method. For those solvent wires with an NH3 molecule at the first position, injection of the H atom into the wire can occur by tunneling. However, further H-atom transfer is blocked by a high barrier at the first (and second) H2O molecule along the solvent wire. H-atom transfer along the entire length of the solvent wire, leading to formation of the 7-ketoquinoline (7KQ*) tautomer, cannot Occur for any of the H2O-containing clusters, in agreement with experimentally observed absence of 7KQ* fluorescence.