Synthesis and electronic investigation of mono- and di-substituted 4-nitro- and 4-amino-pyrazol-1-yl bis(pyrazol-1-yl)pyridine-type ligands and luminescent Eu(iii) derivativesElectronic supplementary information (ESI) available. CCDC 1539452-1539454. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7dt01153a

• Main Authors: Strohecker, D. J, Lynch, V. M, Holliday, B. J, Jones, R. A
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c7dt01153a

Four new disubstituted and monosubstituted nitro- and amino- bis(pyrazol-1-yl)pyridine (bppy) ligands, substituted at the pyrazole 4-position ( 1 , 2 , 5 , 6 ) have been synthesized, along with two luminescent Eu( iii ) tris-β-diketonate derivatives of the amino substituted ligands ( 7 , 8 ). The compounds have been studied using UV-Vis absorbance spectroscopy and cyclic voltammetry which has allowed for characterization of the electronic environments of these ligands. The calculated HOMO-LUMO gap values ( 1 : 3.54 eV; 2 : 3.53 eV; 5 : 3.01 eV; 6 : 3.66 eV) differ from that of bppy (3.86 eV) and the range is indicative that tuning of the ligand electronic environment is possible. Additionally, fluorescence spectroscopy studies were employed to determine ligand T 1 energy levels of the amine-bearing ligands 2 and 6 , yielding values of T 1 of 25 381 cm −1 and 26 201 cm −1 , respectively. These ligands were employed in the synthesis of Eu( iii ) complexes 7 and 8 , for which the absolute and intrinsic quantum yields, lifetimes and ligand sensitization efficiencies were determined. The synthesis of nitro- and amino-bis(pyrazol-1-yl)pyridines was achieved, allowing for tuning of frontier orbital energies and Eu( iii ) complex spectroscopic investigations.