Synthesis, Structure, Biological Evaluation, and Catalysis of Two Pyrazole-Functionalized NHC-RuII Complexes

Two ruthenium complexes, 3a and 3b, bearing pyrazole-functionalized N-heterocyclic carbenes (NHCs) were prepared, and their structures were characterized by X-ray diffraction analysis. Given their promising anticancer potential, we evaluated the cytotoxicity of both complexes against a panel of human cancer cell lines, including breast cancer Bcap-37, colorectal cancer LoVo, gastric cancer SCG7901, and cisplatin-resistant SCG7901-R cells. In vitro results showed that complex 3a inhibited cancer cell proliferation, which exhibited comparable cytotoxicity to that of clinically approved cisplatin. More impressively, complex 3a evoked significant rates of death of cisplatin-resistant gastric cancer SCG7901-R cells, displaying an approximately 13-fold lower IC50 value in this type of cell than cisplatin (i.e., 5.8 +/- 0.4 mu M vs. 83.1 +/- 14.5 mu M). In addition, both ruthenium-NHC complexes were demonstrated to be efficient catalysts for the oxidation of various alcohols. By exploiting them as catalysts, a variety of carbonyl products were obtained in excellent yields. Collectively, these results highlighted the potential of using ruthenium-NHC complexes as highly efficient catalysts as well as promising candidates for treating cancers that are resistant to platinum-based therapy.