| Autor: |
Nadurata VL; School of Chemistry, University of Melbourne, Melbourne, 3010 Victoria, Australia. c.boskovic@unimelb.edu.au., Hay MA; School of Chemistry, University of Melbourne, Melbourne, 3010 Victoria, Australia. c.boskovic@unimelb.edu.au., Janetzki JT; School of Chemistry, University of Melbourne, Melbourne, 3010 Victoria, Australia. c.boskovic@unimelb.edu.au., Gransbury GK; School of Chemistry, University of Melbourne, Melbourne, 3010 Victoria, Australia. c.boskovic@unimelb.edu.au., Boskovic C; School of Chemistry, University of Melbourne, Melbourne, 3010 Victoria, Australia. c.boskovic@unimelb.edu.au. |
| Abstrakt: |
The combination of redox-active metals with redox-active ligands can lead to interesting charge transfer behaviours, including valence tautomerism and solvatochromism. With the aim of investigating a relatively underexplored redox-active metal/redox-active ligand combination, complexes [Co II (acac) 2 (X-BIAN)] (acac - = acetylacetonate; X-BIAN = bis(4-X-phenyl)iminoacenaphthene; 1: X = -CF 3 , 2: X = -Cl, 3: X = -H, 4: X = -Me) and [Co III (acac) 2 (Me-BIAN)] + (5+) have been synthesised and characterised. At all temperatures investigated, and in both the solid and solution state, complexes 1-4 exist in a Co II -BIAN 0 charge distribution, while 5+ adopts a Co III -BIAN 0 charge distribution. In the case of 1-4, the potential Co III -BIAN˙ - valence tautomer is inaccesible; the energy ordering between the ground Co II -BIAN 0 state and the excited Co III -BIAN˙ - state must be reversed in order for an entropically driven interconversion to be possible. The energy gap between the states can be monitored via metal-to-ligand charge transfer bands in the visible region. We demonstrate tuning of this energy gap by varying the electronic properties of the BIAN ligand, as well as by controlling the molecular environment through solvent choice. Solvatochromic analysis, in combination with crystallographic evidence, allows elucidation of the specific solvent-solute interactions that govern the molecular behaviour of 1-4, affording insights that can inform potential future applications in sensing and switching. |
