The series of azolato-bridged dinuclear platinum(II) complexes [{cis-Pt(NH3)2}2(μ-OH)(μ-azolato]2+ (azolato-bridged complexes) are known to be highly effective on cancers both in vitro and in vivo.[1,2] The purpose of our research is to develop next-generation platinum-based drugs and molecular tools that can control the higher-order structure of DNA by focusing on its unique DNA binding mode. More than twenty azolato-bridged complexes were synthesized, and some derivatives exhibited much higher in vivo antitumor efficacy than oxaliplatin against mouse homografted Colon-26 colorectal tumor. Especially, one of the derivatives exhibited markedly high and long-lasting therapeutic effect even against large-sized tumors, and experiments with immunodeficient tumor-bearing mice suggest that the complex has immunostimulatory activity. Apart from the development of anticancer drugs, microscopic observations revealed that these complexes significantly change the higher-order structure of double-stranded DNA[3,4] and induce liquid-liquid phase separation in single-stranded DNA solutions. Various application studies based on azolato-bridged complexes will be presented.