Synthesis of two-dimensional neutral supramolecular architecture via coordination-driven self-assembly.

摘要

Research conducted in the area of design and self-assembly of self-assembled supramolecular structures has made a lot of progress over the last three decades. In this broad area of research, construction of self-assembled metallasupramolecular structures based on transition metal-ligand interactions (coordination-driven self-assembly) has attracted considerable attention because of their potential applications as sensors, probes, photonic devices, catalysts and in basic host guest chemistry. The square-planar Pt(II) center has been one of the most favorite metals in the area of coordination-driven self-assembly. Yet, interestingly, all of the self-assembled macrocycles having Pt(II) center used neutral nitrogen-based linkers as the donor units in the self-assembly processes, thereby generating charged/ionic supramolecules. This dissertation presents a new approach in the directional bonding strategy that utilizes platinum-to-oxygen coordination for the synthesis of platinum(II) based neutral two-dimensional (2D) nanoscopic macrocycles.; Seventeen neutral metallasupramolecular macrocycles incorporating Pt(II)-O bonds have been synthesized in high yield via the self-assembly of rigid, dicarboxylate-based oxygen donor and platinum-containing acceptor ligands. Most of the macrocycles were characterized by X-ray single-crystal structure analysis, and, in all cases, nuclear magnetic resonance (NMR) spectra 31p{lcub}1H{rcub} and 1H] were consistent with the formation of single highly symmetrical species.; The newly developed strategy for the formation of neutral assemblies using anionic oxygen donor ligands was extended to self-assemble five neutral platinum-based macrocycles incorporating cyclic oxocarbondianions, squarate and croconate and their acyclic analogue oxalate. These neutral Pt(II)-based supramolecular ensembles were also synthesized in high yields (90-95%). The macrocycles were characterized by multinuclear NMR and FAB mass spectrometry or X-ray crystallography. The formation of these macrocyclic species also demonstrated that flexible linkers preferably change their coordination modes to yield entropically driven smaller macrocycles whenever possible.; Finally, self-recognition in the transition-metal-mediated self-assembly of some 2-D polygons has been presented. Prolonged heating of two or three organoplatinum reagents with 4,4'-dipyridyl in aqueous acetone results in the predominant formation of a rectangle, triangle, and/or square. All mixtures are characterized with NMR and electrospray ionization mass spectrometry (ESIMS). Despite the potential for ill-defined oligomeric products, these mixed ligand systems prefer to self-assemble into discrete species.