Abstract
The present article reports the application of vibrational circular dichroism (VCD) and temperature-dependent electronic circular dichroism (ECD) methods to reveal the dynamical aspects of a star-burst tetranuclear metal complex with a labile central core in a solution. One-handed chiral inert tecton, ∆- or Λ-[Ru(III)(acac)2(taetH)] (acacH = acetylacetone, taetH2 = tetraacetylethane), was prepared by reacting [Ru(acac)3] with taetH2 in solid at 120 °C. The ∆Λ-pair of pure enantiomers was obtained chromatographically. On adding Al(ClO4)3 to its enantiopure solution, three units of one-handed tecton were assembled spontaneously around an aluminum(III) ion to form a star-burst tetranuclear complex, [{∆- or Λ-Ru(acac)2(taet)}3Al(III)]. The VCD spectrum recorded on the CDCl3 solution of the complex showed that the central chirality around an Al(III) ion took dominantly the absolute configuration antipodal to those of peripheral Ru(III) units at the temperature lower than −10 °C. The complex underwent interconversion between the ∆- and Λ-configurations around a central Al(III) core (or epimerization) in solution. The activation energy barrier was determined from the time courses of ECD spectra in CHCl3 and CH3OH.
Highlights
Tris(chelated) metal complexes with β-diketonato ligands have demonstrated a wide application in the fields of asymmetric catalysis, electrochemical mediators, metal oxide frameworks (MOF), and so on [1,2,3,4,5,6,7,8]
The vibrational circular dichroism (VCD) method was proved to be an effective tool to determine the absolute configuration of even a labile molecule in a solution
This was accomplished that the observed VCD peaks were high and that the measurements were performed within a short period of time
Summary
Tris(chelated) metal complexes with β-diketonato ligands have demonstrated a wide application in the fields of asymmetric catalysis, electrochemical mediators, metal oxide frameworks (MOF), and so on [1,2,3,4,5,6,7,8]. In addition to the unique properties as a mononuclear complex, novel stereochemical aspects immerge when a labile metal ion is incorporated into these units. The dynamical control of such chiral properties is an attractive issue in constructing the supramolecular architectures of metal complexes. One approach taken in this area is so-called molecular tectonics [8]. One-, two-, or three-handed units (or tectons) are connected to construct molecular frameworks systematically [9]. We have employed the ∆Λ isomerism of a tris(chelated) complex as a chiral motif with D3 symmetry in the tectonics approach [5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
