Rhenium(I)-Based Tetranuclear Metallorectangles from Linear BODIPY and Bischelating Aminoquinonato Ligands:...

Supramolecular metallorectangles 1-4 were successfully synthesized via a multicomponent coordination-driven self-assembly approach, combining Re₂(CO)₁₀ with a boron dipyrromethene (BODIPY)-based ligand as a linear, ditopic linker, and an aminoquinonato ligand as a bischelating, tetratopic ligand in a single step. The metallorectangles were meticulously characterized through IR, NMR, UV-vis absorption and emission spectroscopy, elemental analyses, FESEM, and electrospray ionization mass spectrometry. The rectangular structural feature of metallacyclophane 3 was theoretically rationalized using DFT calculations, and its theoretical and experimental IR spectra were coherent. Furthermore, the metallacyclophanes exhibited modest anticancer activities against breast cancer (MDA-MB-231) and lung cancer (A549) cells. Additionally, the binding studies of metallorectangle 1 with triphenylene and pyrene as organic guests were performed using UV-vis absorption and emission spectroscopy, indicating substantial binding with binding constants of 7.23 × 10⁵ M^-1 and 8.43 × 10⁵ M^-1, respectively. The host-guest binding was also confirmed using a ¹H NMR titration experiment. Moreover, in silico molecular docking studies of 1 with human serum albumin (HSA) protein showed strong hydrogen bonding interactions with six different amino acid residues.