A Luminescent 1D Silver Polymer Containing [2.2]Paracyclophane Ligands

Room-temperature synthesis of nanometric and luminescent silver-MOFs

Three silver-MOFs were prepared using an optimized, room-temperature methodology starting from AgNO₃ and dicarboxylate ligands in water/ethanol yielding Ag ₂ BDC, Ag ₂ NDC (UAM-1), and Ag ₂ TDC (UAM-2) at 38%-48% (BDC, benzenedicarboxylate; NDC, 1,8-naphthalene-dicarboxylate; TDC, p-terphenyl-4,4″-dicarboxylate). They were characterized by PXRD/FT-IR/TGA/photoluminescence spectroscopy, and the former two by SEM. These materials started decomposing at 330°C, while showing stability. The crystal structure of UAM-1 was determined by PXRD, DFT calculations, and Rietveld refinement. In general, the structure was 3D, with the largest Ag-O bond interlinking 2D layers. The FT-IR spectra revealed 1450 and 1680 bands (cm^-1) of asymmetrically stretching aniso-/iso-bidentate -COO in coordination with 2/3-Ag atoms, accompanied by Ag-O bands at 780-740 cm^-1, all demonstrating the network formation. XRD and SEM showed nanometric-scale crystals in Ag₂BDC, and UAM-1 developed micrometric single-stranded/agglomerated fibrillar particles of varying nanometric widths. Luminescence spectroscopy showed emission by Ag₂BDC, which was attributed to ligand-to-metal or ligand-to-metal-metal transitions, suggesting energy transfer due to the short distance between adjacent BDC molecules. UAM-1 and UAM-2 did not show luminescence emission attributable to ligand-to-metal transition; rather, they presented only UV emission. The stabilities of Ag₂BDC and UAM-1 were evaluated in PBS/DMEM/DMEM+FBS media by XRD, which showed that they lost their crystallinity, resulting in AgCl due to soft-soft (Pearson's principle) affinity.

Metal-to-Metal Distance Modulation by Ligand Design: A Case Study of Structure-Property Correlation in Planar Chiral Cyclophanyl Metal Complexes

Multinuclear metal complexes have seen tremendous progress in synthetic advances, their versatile structural features, and emerging applications. Here, we conceptualize Metal-to-Metal distance modulation in cyclophanyl metal complexes by bridging ligand design employing the co-facially stacked cyclophanyl-derived pseudo-geminal, -ortho, -meta, and -para constitutional isomers grafted with N-, O-, and P- containing chelates that allow the installation of diverse (hetero)metallic moieties in a distance-defined and spatially-oriented relation to one another. Metal-to-Metal distance modulation and innate transannular "through-space" π-π electronic interactions via the co-facially stacked benzene rings in cyclophanyl-derived complexes as well as their specific stereochemical structural features (element of planar chirality) are crucial factors that contribute to the tuning of structure-property relationships, which stand at the very center from the perspective of cooperative effects in catalysis as well as emerging material applications.