A comprehensive investigation of the partitioning and hydrogen bonding behavior of indole containing derivatives of 1,3,4-thiadiazole and 1,2,4-triazole by means of experimental and calculative approaches

The lipophilicity and hydrogen bonding capability of the title compounds was investigated. HPLC lipophilicity indices proved to be appropriate substitutes of directly measured octanol-water partition coefficients and were used to evaluate the predictive power of 7 different calculative approaches. Conformation effects as well as particularities in the way the triazole and thiadiazolyl-amine moieties are treated by the different calculation systems need to be taken into account in order to establish sound correlations with experimental data. Cyclohexane-water partition coefficients were determined and used to derive Delta logP values as a measure of hydrogen bonding ability. Exploration of the Delta logP parameter unraveled particular features of the hydrogen bond capability pattern of the compounds. Thermodynamically derived hydrogen bonding parameters Sigma c(a) and Sigma c(d) were used for the analysis of all lipophilicity data. A negative contribution of the hydrogen bond acceptor capability, much stronger in the case of the cyclohexane-water partition coefficients, was found while the hydrogen bond donor factor proved not essential. Similar analysis of the Delta logP values revealed a more complex nature of that parameter than being a pure hydrogen bond measure.