Electrochemical and DFT study of the reduction of substituted phenanthrolines

详细信息    查看全文

• 作者：Hendrik Ferreira ; Marrigje M. Conradie ; Karel G. von Eschwege ; Jeanet Conradie ; ^{conradj@ufs.ac.za}
• 关键词：Phenanthroline ; Reduction potential ; Cyclic voltammetry ; DFT ; Exp-DFT relationships
• 刊名：Polyhedron
• 出版年：2017
• 出版时间：28 January 2017
• 年：2017
• 卷：122
• 期：Complete
• 页码：147-154
• 全文大小：2474 K
• 卷排序：122

文摘

The irreversible electrochemical reduction data of a series of free uncoordinated differently substituted phenanthrolines is presented. Electron withdrawing chloride substituents in the 4,7 ring positions increase the reduction potential by 0.3 V, while electron donating methyl substituents lead to a lowering of reduction potential relative to unsubstituted 1,10-phenanthroline. Linear relationships are obtained between the reduction potential of free uncoordinated differently substituted phenanthrolines and density functional theory (DFT) calculated LUMO (lowest unoccupied molecular orbital) energies, electron affinities, global electrophilicity indexes and Mulliken electronegativities. The reduction potential of 4,7-diphenyl-1,10-phenanthroline deviates slightly from the linear trend, since the phenyl groups donate electron density to the phenanthroline ring system through both π-resonance and σ-inductive effects. This enables the phenanthroline ring system to more readily accept an electron at a higher, less negative potential than is otherwise the case. On the contrary, the non-aromatic substituents (e.g. Me, NH2 and Cl) withdraw/donate electron density from/to the phenanthroline ring system through σ-inductive effects only. Linear relationships are also obtained between the reduction potential of the series of phenanthroline free ligands and the formal reduction potential of corresponding metal-phenanthroline complexes.