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Exposing the Excited‐State Equilibrium in an Ir III Bichromophore: A Combined Time Resolved Spectroscopy and Computational Study
Author(s) -
Yarnell James E.,
McCusker Catherine E.,
Leeds Alexander J.,
Breaux Josué M.,
Castellano Felix N.
Publication year - 2016
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201600194
Subject(s) - chromophore , excited state , chemistry , photochemistry , spectroscopy , singlet state , photoluminescence , ultrafast laser spectroscopy , luminescence , atomic physics , optoelectronics , physics , quantum mechanics
The electronic structure and photophysical properties of a luminescent Ir III bis‐cyclometalated complex covalently attached to one 4‐piperidinyl‐1,8‐naphthalimide (PNI) chromophore through a coordinated 1,10‐phenanthroline, [Ir(ppy) 2 (phen‐PNI)](PF 6 ), is presented. This bichromophore represents a new class of visible light‐harvesting Ir III complexes that exhibit markedly enhanced room‐temperature excited‐state lifetimes ( τ = 8.8 ms) as a result of intervening ligand‐centered triplet states present on the pendant naphthalimide chromophore. In this Ir III complex, the intense singlet fluorescence of the pendant PNI chromophore is nearly quantitatively quenched and was found to sensitize the Ir III metal/ligand‐to‐ligand charge‐transfer (MLLCT) excited state. The excited state ultimately returns to the PNI chromophore as a long‐lived excited triplet that disposes of its energy by equilibrating with the photoluminescent Ir III MLLCT excited state. Evidence of the excited‐state equilibrium is provided through static and dynamic photoluminescence spectroscopy, transient absorption spectroscopy, and time‐dependent density functional theory calculations.