Oligo(p-phenyleneethynylene)-Derived Porous Luminescent Nanoscale Coordination Polymer of Gd-III: Bimodal Imaging and Nitroaromatic Sensing

Abstract

Self-assembled highly luminescent nanoscale coordination polymer of {[Gd(OPE)(NO3)(H2O)2]center dot H2O} (NCP-1), (oligo-(p-phenyleneethynylene)dicarboxylate) was synthesized by coordination-driven self-assembly of oligo-(p-phenyleneethynylene)dicarboxylic acid and Gel in polar solvent under refluxing conditions. This nanostructure has been characterized by FESEM, TEM, powder X-ray diffraction, and adsorption study. Interdigitation between ID coordination polymers through alkyl chains results in a porous supramolecular 3D extended structure. NCP-1 shows permanent microporosity as revealed by type-I CO2 uptake profile. FESEM and TEM studies of NCP-1 reveal nanorod-like morphology with square-type cross section having dimensions of 50-100 nm diameter and 0.5-0.8 pm length. High-magnification TEM images show long-range structural ordering present in NCP-1 with uniform dark lines having an interspacing distance of 0.9-1.1 nm. Physiological stability and strong luminescence features of NCP-1 have been exploited for bioimaging based on internalization into mammalian cultured cell lines HEK 293T and H1299. Magnetic resonance imaging studies suggest that NCP-1 could act as a potential negative (T2) contrast agent. Furthermore, this porous luminescent NCP-1 shows efficient nitroaromatic sensing as realized by the fluorescence quenching in solution as well as in vapor phase of the analyte like 2,4-dinitrotoluene (2,4-DNT). These results demonstrate that hybridization of a paramagnetic metal center and luminescent linker in a nanoscale porous coordination polymer culminates in a functional hybrid material with potential bimodal imaging and sensing applications.