Multiple phenyl ring appended Re-based complexes for strong visible light absorption and DNA binding.

A series of facial-Re(CO)3-based acyclic complexes (1-3) possessing N∩O bis-chelating ligands and a triphenylphosphine oxide donor was synthesized and characterized. The most interesting structural feature of these complexes is that both the coordinated ligands are functionalized with external phenyl rings. Single crystal X-ray diffraction analysis confirms that each molecule demonstrates a variety of intermolecular supramolecular interactions via the external phenyl rings. All the complexes displayed strong absorption (ε = 14 000-40 000 M-1 cm-1) over wide visible region (400-600 nm). Due to the interesting structural and photophysical properties of the complexes, a satisfactory DNA binding ability was observed. The binding of the complexes with DNA grooves was confirmed by a significant increase in the absorption intensities of the complexes in the visible region, absorption enhancement of DNA and circular dichroism.