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Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of Chalcogenidoplumbates(II or IV)
Published on: December 29, 2016
An unprecedented structural interconversion in solution of aggregate zinc(II) salen Schiff-base complexes.
Giuseppe Consiglio1, Salvatore Failla, Paolo Finocchiaro
1Dipartimento di Ingegneria Industriale, Università di Catania, I-95125 Catania, Italy.
Inorganic Chemistry
|July 18, 2012
Summary
Amphiphilic Zn(salen) derivatives exhibit unique structural changes in solution. Water concentration drives interconversion between two defined dimers (A and B) in noncoordinating solvents like chloroform.
Area of Science:
- Coordination Chemistry
- Supramolecular Chemistry
- Solution-State Dynamics
Background:
- Amphiphilic Zn(salen) derivatives are versatile coordination compounds.
- Understanding their aggregation behavior in solution is crucial for designing functional materials.
- Solvent properties significantly influence the self-assembly of coordination complexes.
Purpose of the Study:
- To investigate the solution aggregation properties of amphiphilic Zn(salen) derivatives in noncoordinating solvents.
- To elucidate the structural interconversion of aggregate species driven by water concentration.
- To explore the role of solvent polarity and molecular flexibility in aggregation.
Main Methods:
- Detailed spectroscopic studies including proton nuclear magnetic resonance ((1)H NMR), diffusion ordered spectroscopy (DOSY NMR), and optical absorption spectroscopy.
- Variable-temperature (1)H NMR studies to probe dynamic processes.
- Analysis of aggregation behavior as a function of water concentration in chloroform.
Main Results:
- Two distinct dimeric species, A and B, were identified in equilibrium.
- Species A, observed at lower concentrations, features Zn(II) atoms interacting via axial coordination, likely forming square-based pyramidal structures.
- Species B, prevalent at higher concentrations, involves a coordination mode interconversion, suggesting a transition from square-pyramidal to trigonal bipyramidal structures.
- A fluxional equilibrium between species B and a nonequivalent species B' was observed via variable-temperature NMR.
Conclusions:
- The aggregation of amphiphilic Zn(salen) derivatives is concentration-dependent and sensitive to water content in noncoordinating solvents.
- A unique structural interconversion between two dimeric species is driven by water concentration, involving changes in Zn(II) coordination geometry.
- The conformational flexibility of the Schiff base ligand and solvent polarity play significant roles in mediating these aggregation phenomena.
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