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)3Re­(μ-SeR)2Re­(CO)3}2(μ-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 Re2(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 1a,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·(pyrene)
and 1b·(triphenylene) revealed that
CH···π interactions are mainly responsible for
the binding of 1b with pyrene and triphenylene.