Multifunctional White-Light-Emitting Metal–Organic Gels with a Sensing Ability of Nitrobenzene

In this study, three novel luminescent nanofibrous metal-organic gels (MOGs) have been synthesized by the reaction of 1,3,5-tris(3-pyridylmethoxyl)benzene (L) with chloride salts of Cd(II), Hg(II), and Cu(II). The metal-ligand coordination, intermolecular π-π stacking and several other weak interactions found to play an important role in the formation of nanofibrous materials. The gel materials are characterized by rheology, diffuse reflectance spectra and various microscopic techniques such as TEM, FESEM, and AFM. The gels MOG-1 and MOG-2 were found to exhibit significant white photoluminescence, whereas the MOG-3 exhbits green emission upon excitation at 325 nm. Furthermore, the MOG-1 has shown its application as a chemosensor for the remarkable detection of nitroaromatics such as nitrobenzene (NB), 2,4-dinitrophenol (DNP). The significant quenching response for NB and DNP is attributed to the strong charge-transfer interactions between the electron-deficient aromatic ring of NB and the electron rich aromatic group of L in MOG-1. The crystal structure of Cd(II) complex of L reveals the formation one-dimensional network which contains strong π-π interactions within and between the networks and these strong π-π interactions generate the free charge carrier in all these nanofibrous gels.