Mandapati, Pavan and Braun, Jason D. and Killeen, Charles and Davis, Rebecca L. and Williams, J. A. Gareth and Herbert, David E. (2019) 'Luminescent platinum(II) complexes of N^N–^N amido ligands with benzannulated n-heterocyclic donor arms : quinolines offer unexpectedly deeper red phosphorescence than phenanthridines.', Inorganic chemistry., 58 (21). pp. 14808-14817.
A platform for investigating the impact of π-extension in benzannulated, anionic pincer-type N^N–^N-coordinating amido ligands and their Pt(II) complexes is presented. Based on bis(8-quinolinyl)amine, symmetric and asymmetric proligands bearing quinoline or π-extended phenanthridine (3,4-benzoquinoline) units are reported, along with their red-emitting, phosphorescent Pt(II) complexes of the form (N^N–^N)PtCl. Comparing the photophysical properties of complexes of (quinolinyl)amido ligands with those of π-extended (phenanthridinyl)amido analogues revealed a counterintuitive impact of site-selective benzannulation. Contrary to conventional assumptions regarding π-extension, and in contrast to isoenergetic lowest energy absorption bands and a red shift in fluorescence from the organic proligands, a blue shift of nearly 40 nm in the emission wavelength is observed for Pt(II) complexes with more extended bis(phenanthridinyl) ligand π-systems. Comparing the ground state and triplet excited state structures optimized from density functional theory (DFT) and time-dependent-DFT calculations, we trace this effect to a greater rigidity of the benzannulated complexes, resulting in a higher energy emissive triplet state, rather than to a significant perturbation of orbital energies caused by π-extension.
|Full text:||(AM) Accepted Manuscript|
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|Publisher Web site:||https://doi.org/10.1021/acs.inorgchem.9b02480|
|Publisher statement:||This document is the Accepted Manuscript version of a Published Work that appeared in final form in Inorganic chemistry copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.inorgchem.9b02480|
|Date accepted:||09 October 2019|
|Date deposited:||24 October 2019|
|Date of first online publication:||22 October 2019|
|Date first made open access:||22 October 2020|
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