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1,5-Diarylbiguanides and their nickel(II) complexes
David A McMorran1, C John McAdam, Holly van der Salm
1Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand. davidm@chemistry.otago.ac.nz
Dalton Transactions (Cambridge, England : 2003)
|December 20, 2012
Summary
New diarylbiguanide ligands and their nickel complexes were synthesized and characterized. Ligand deprotonation enhances the aromaticity of the chelate ring, influencing electronic properties and supramolecular assembly potential.
Area of Science:
- Coordination Chemistry
- Supramolecular Chemistry
- Materials Science
Background:
- 1,5-Diarylbiguanides are a class of organic ligands with potential applications in coordination chemistry.
- Understanding the structural and electronic properties of biguanide ligands and their metal complexes is crucial for designing new materials.
- Hydrogen bonding plays a significant role in the self-assembly of supramolecular structures.
Purpose of the Study:
- To synthesize and characterize a series of 1,5-diarylbiguanide ligands and their nickel complexes.
- To investigate the effect of ligand deprotonation on the electronic and structural properties of the nickel complexes.
- To explore the potential of these complexes in the formation of hydrogen-bonded metallosupramolecular assemblies.
Main Methods:
- Synthesis and characterization of 1,5-diarylbiguanides (HL1-HL5) and their nickel complexes ([Ni(HL)2](BF4)2 and [Ni(L)2]).
- X-ray crystallography for structural determination of ligands and complexes.
- Spectroscopic techniques (IR, 1H NMR) and cyclic voltammetry for electronic property analysis.
- Density Functional Theory (DFT) calculations for structural and electronic validation.
Main Results:
- Structural characterization revealed extensive hydrogen bonding in diarylbiguanides.
- Nickel complexes ([Ni(HL)2](BF4)2 and [Ni(L)2]) were successfully synthesized and characterized.
- Ligand deprotonation facilitated increased aromatization of the biguanide chelate ring, evidenced by spectroscopic and crystallographic data.
- Cyclic voltammetry showed easier Ni(II)/Ni(III) oxidation upon deprotonation.
- The structure of a metallosupramolecular assembly between [Ni(L3)2] and 1,8-naphthalimide was determined.
Conclusions:
- Deprotonation of diarylbiguanide ligands leads to significant changes in the electronic structure and aromaticity of nickel complexes.
- These nickel complexes exhibit potential as building blocks (tectons) for constructing hydrogen-bonded metallosupramolecular architectures.
- The study provides insights into the structure-property relationships of biguanide-metal complexes and their supramolecular assembly capabilities.
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