Enhancing the photoluminescence quantum yields of blue-emitting cationic iridium(III) complexes bearing bisphosphine ligands
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Herein we present a structure-property relationship study of thirteen cationic iridium (III) complexes of the form of [Ir(C^N)2(P^P)]PF6 in both solution and the solid state through systematic evaluation of six bisphosphine (P^P) ligands (xantphos, dpephos, dppe, Dppe, nixantphos and isopropxantphos). All of the complexes are sky-blue emissive, but their photoluminescence quantum yield (ΦPL) are generally low. However, strong and long-lived blue luminescence (λem: 471 nm; ΦPL = 52%; τe, of 13.5 μs) can be obtained by combining the reduced bite angle of the 1,2-bis-diphenylphosphinoethene (dppe) chelate with the bulky 2-(4,6-difluorophenyl)-4-mesitylpyridinato (dFmesppy) cyclometalating ligand. To the best of our knowledge this is the highest ΦPL and the longest τe reported for cyclometalated iridium(III) complexes bearing bisphosphine ligands. Light-emitting electrochemical cells (LEECs) were fabricated using lead complexes from this study, however due in part to the irreversible electrochemistry, no functional LEEC was achieved. Organic light-emitting diodes were successfully fabricated but only attained maximum external quantum efficiencies of 0.25%.
Rota Martir , D , Bansal , A K , Di Mascio , V , Cordes , D B , Henwood , A F , Slawin , A M Z , Kamer , P C J , Martínez-Sarti , L , Pertegás , A , Bolink , H J , Samuel , I D W & Zysman-Colman , E 2016 , ' Enhancing the photoluminescence quantum yields of blue-emitting cationic iridium(III) complexes bearing bisphosphine ligands ' Inorganic Chemistry Frontiers , vol 3 , no. 2 , pp. 218-235 . DOI: 10.1039/C5QI00177C
Inorganic Chemistry Frontiers
Copyright 2015 the Authors. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (http://creativecommons.org/licenses/by/3.0/).
EZ-C acknowledges the University of St Andrews for financial support. We thank Johnson Matthey and Umicore AG for the gift of materials and Cihang Yu for the preparation of isopropxantphos. We thank Dr. Nail Shaveleev for the synthesis of NMS25. IDWS and AKB acknowledge support from EPSRC (EP/J01771X). This work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO) MAT2014-55200.