Synthesis, crystal structure, and DNA-binding studies of different coordinate binuclear silver(i) complexes with benzimidazole open-chain ether ligandsCCDC 721072, 721073 and 1408501. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c5nj01684c

Three new binuclear silver( i ) complexes, namely, [Ag 2 (Meobb) 2 ](pic) 2 ·2H 2 O ( 1 ), [Ag 2 (Etobb) 2 (pic)](pic)·(CH 3 CN) ( 2 ) and [Ag 2 (Bobb) 2 (pic) 2 ] ( 3 ) (Meobb = 1,3-bis(1-methylbenzimidazol-2-yl)-2-oxapropane, Etobb = 1,3-bis(1-ethylbenzimidazol-2-yl)-2-oxapropane, Bobb = 1,3-bis(1-benzylbenzimidazol-2-yl)-2-oxapropane, pic = picrate), have been synthesized and characterized by elemental analyses, IR spectroscopy and X-ray single crystal diffraction. Complex 1 displays an Ag 2 (Etobb) 2 dimeric structure. Each silver( i ) ion is coordinated to two nitrogen atoms that adopt a distorted linear configuration. In complex 2 , the coordination environment of silver( i ) atoms is different. The Ag1 ion is coordinated in a T-shaped tri-coordinated geometry and the Ag2 is best described to be in a distorted tetrahedron. Complex 3 exhibits a discrete di-silver metallacyclic framework. One silver atom (Ag1) is present in a distorted tetrahedral geometry, whereas the other silver atom (Ag2) is five-coordinated with two nitrogen atoms, oxygen atoms and the Ag1 to form a distorted square-based pyramidal configuration. The interactions of the three complexes with calf thymus DNA (CT-DNA) has been investigated by electronic absorption titration, fluorescence spectroscopy and viscosity measurements, and the modes of CT-DNA binding to the complexes have been proposed. Experimental results suggest that the silver( i ) complexes bind to DNA in an intercalation mode, and their binding affinity for DNA follows the order 1 > 2 > 3. The DNA-binding studies demonstrate that steric hindrance has a large influence on the binding ability to DNA. The complex that has smaller steric hindrance binds more strongly to DNA. Three new binuclear silver( i ) complexes with bis-benzimidazole ligands have been developed and they bind to CT-DNA in an intercalation mode.