Delocalization tunable by ligand substitution in [L 2 Al] n - complexes highlights a mechanism for strong electronic coupling

Ligand-based mixed valent (MV) complexes of Al(iii) incorporating electron donating (ED) and electron withdrawing (EW) substituents on bis(imino)pyridine ligands (I P) have been prepared. The MV states containing EW groups are both assigned as Class II/III, and those with ED functional groups are Cl...

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Bibliographic Details
Published in:Chemical science (Cambridge) 2020-11, Vol.12 (2), p.675-682
Main Authors: Arnold, Amela, Sherbow, Tobias J, Bohanon, Amanda M, Sayler, Richard I, Britt, R David, Smith, Allison M, Fettinger, James C, Berben, Louise A
Format: Article
Language:English
Subjects:
Alkali metals
Banded structure
Charge transfer
Chemistry
Crystallography
Functional groups
Ions
Ligands
NMR
Nuclear magnetic resonance
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Summary:Ligand-based mixed valent (MV) complexes of Al(iii) incorporating electron donating (ED) and electron withdrawing (EW) substituents on bis(imino)pyridine ligands (I P) have been prepared. The MV states containing EW groups are both assigned as Class II/III, and those with ED functional groups are Class III and Class II/III in the (I P )(I P )Al and [(I P )(I P )Al] charge states, respectively. No abrupt changes in delocalization are observed with ED and EW groups and from this we infer that ligand and metal valence p-orbitals are well-matched in energy and the absence of LMCT and MLCT bands supports the delocalized electronic structures. The MV ligand charge states (I P )(I P )Al and [(I P )(I P )Al] show intervalence charge transfer (IVCT) transitions in the regions 6850-7740 and 7410-9780 cm , respectively. Alkali metal cations in solution had no effect on the IVCT bands of [(I P )(I P )Al] complexes containing -PhNMe or -PhF substituents. Minor localization of charge in [(I P )(I P )Al] was observed when -PhOMe substituents are included.
ISSN:2041-6520
2041-6539
DOI:10.1039/D0SC02812F