Simultaneous presence of mono- and bi-cationic bipyridyls within a metal-organic supramolecular host: crystal structure, spectral and Hirshfeld surface analysis

A new supramolecular metal-organic complex, {[Fe(CN)6]3-(H2bipy)2+(Hbipy)+ 3H2O} (where bipy = 4,4'-bipyridyl) has been synthesized hydrothermally at 90°C and characterized by single crystal X-ray crystallographic study (SC-XRD), powder X-ray diffraction analysis (PXRD) and other spectroscopic analysis. Structural analysis reveals that the complex crystallizes in monoclinic space group P21/c and is a 3D supramolecular complex. Cyanide-water hydrogen bonding interactions between {Fe(CN)6}3- and guest water molecules form a wave-like 2D supramolecular layer structure parallel to the crystallographic ac-plane with the formation of rectangular cavities of dimension 10.6 x 9.8 Å. These 2D layers are further connected by O-H···O hydrogen bonding interactions to form 3D supramolecular structure with the creation of 1D supramolecular channels along the crystallographic a-axis. The bi-cationic (H2bipy)2+ form two N+-H···water hydrogen bonding interactions with two different water molecules and reside within the rectangular cavities. Monocationic (Hbipy)+ moieties form a 1D supramolecular chain structure through repetitive N···H-N+ hydrogen bonding interactions and are present within the 1D supramolecular channels. In addition, these two different types of bipy moieties are interconnected to each other through π···π interactions. Hirshfeld surface analysis and the corresponding 2D fingerprint plots clearly identify the presence of different types of supramolecular interactions between the two differently charged bipyridyl moieties and the host framework, and N-H/H-N contacts, corresponding to the hydrogen bonding interactions, has a significant contribution to the total surface. Both the absorption and emission spectra of the complex have also been studied.