Self-Assembly of Selenium-Bridged Rhenium(I)-Based Metalla Rectangles: Synthesis, Characterization, and Molecular Recognition Studies

Self-assembly of the selenium-bridged novel metallacyclophanes [{(CO)(3)Re(mu-SeR)(2)Re(CO)(3)}(2)(mu-L)(2)] (1-3) has been accomplished by treating diaryl diselenide with low-valent transition-metal carbonyl and rigid bidentate azine ligands under one-pot reaction conditions. The oxidative addition of diphenyl/dibenzyl diselenides to S Re-2(CO)(10) with 4,4'-bipyridine, trans-1,2-bis(4-pyridyl)ethylene, and 1,4-bis[2-(4-pyridyl)ethenyl]benzene afforded tetranuclear metallacyclophanes. These compounds have been characterized by elemental analysis and IR, NMR, and UV-vis absorption spectroscopic techniques. The molecular structures of metallacylophanes 1a,b and 2 were determined by single-crystal X-ray diffraction methods, and the crystal structures showed that two selenium-bridged dirhenium metallacycles were linked by two bipyridyl spacers and attained a framework of molecular rectangles. In addition, the molecular recognition capabilities of the molecular rectangles la,b and 2 with aromatic compounds such as pyrene and triphenylene have been investigated by studying their binding properties, using UV-visible absorption and fluorescence emission spectrophotometric methods. The nature of the binding interactions were further supported by single-crystal X-ray diffraction methods, and the crystal structures of 1b center dot(pyrene) and 1b center dot(triphenylene) revealed that CH center dot center dot center dot pi interactions are mainly responsible for the binding of 1b with pyrene and triphenylene.