Novel N^C^N-cyclometallated platinum complexes with acetylide co-ligands as efficient phosphors for OLEDs

Two new cyclometallated platinum(II) complexes have been prepared that incorporate a terdentate N^C^N-coordinating ligand and a monodentate acetylide co-ligand. The complexes, namely [PtL3–CC–C6H3F2] and [PtL6–CC–C6H3F2] (where HL3 = 5-methyl-1,3-di(2-pyridyl)benzene; HL6 = 5-mesityl-1,3-di(2-pyridyl)benzene; H–CC–C6H3F2 = 3,5-difluorophenylacetylene), were prepared by ligand metathesis from the corresponding chloro complex PtLnCl. Both of the new complexes are intensely luminescent in solution, displaying quantum yields superior to PtLnCl. OLEDs have been prepared using the new compounds as phosphorescent emitters. Although both lead to efficient devices, the best electroluminescence quantum efficiencies are obtained with the derivative of HL6, having the mesityl group on the cyclometallated phenyl ring. The superior performance with this complex can be rationalised in terms of the greater steric hindrance that serves to reduce aggregate-induced quenching.

[1]  V. Fattori,et al.  N∧C∧N‐Coordinated Platinum(II) Complexes as Phosphorescent Emitters in High‐Performance Organic Light‐Emitting Devices , 2007 .

[2]  Soma Chakraborty,et al.  Synthesis, structure, characterization, and photophysical studies of a new platinum terpyridyl-based triad with covalently linked donor and acceptor groups. , 2005, Inorganic chemistry.

[3]  V. Guerchais,et al.  Sensory luminescent iridium(III) and platinum(II) complexes for cation recognition , 2011 .

[4]  R. Friend,et al.  Synthesis, Electrochemistry, and Spectroscopy of Blue Platinum(II) Polyynes and Diynes. , 1998, Angewandte Chemie.

[5]  Chul Baik,et al.  Synthesis and photophysical properties of luminescent platinum(II) complexes with terdentate polypyridine ligands: [Pt(bpqb)X] and [Pt(tbbpqpy)X](PF6) (bpqb-H = 1,3-bis(4′-phenyl-2′-quinolinyl) benzene; tbbpqpy = 4-tert-butyl-1,3-bis(4′-phenyl-2′-quinolinyl) pyridine; X = Cl, CCC6H5, CCC6H4NMe2, CCC , 2006 .

[6]  P. Douglas,et al.  Coordination complexes exhibiting room-temperature phosphorescence: Evaluation of their suitability as triplet emitters in organic light emitting diodes , 2006 .

[7]  J. Williams,et al.  Localised to intraligand charge-transfer states in cyclometalated platinum complexes: an experimental and theoretical study into the influence of electron-rich pendants and modulation of excited states by ion binding. , 2009, Dalton transactions.

[8]  J. Kalinowski,et al.  Light-emitting devices based on organometallic platinum complexes as emitters , 2011 .

[9]  F. Castellano,et al.  Room temperature phosphorescence from a platinum(II) diimine bis(pyrenylacetylide) complex. , 2003, Inorganic chemistry.

[10]  M. W. George,et al.  Photophysics of diimine platinum(II) bis-acetylide complexes. , 2001, Inorganic chemistry.

[11]  C. Che,et al.  Luminescent cyclometalated diimine platinum(II) complexes: Photophysical studies and applications , 2004 .

[12]  D. McMillin,et al.  Luminescence that lasts from Pt(trpy)Cl+ derivatives (trpy=2,2′;6′,2″-terpyridine) , 2002 .

[13]  S. Forrest,et al.  Measurement of the lowest unoccupied molecular orbital energies of molecular organic semiconductors , 2009 .

[14]  C. Botta,et al.  Cyclometallated platinum(II) complexes of 1,3-di(2-pyridyl)benzenes for solution-processable WOLEDs exploiting monomer and excimer phosphorescence , 2011 .

[15]  C. Che,et al.  Probing d8−d8 Interactions in Luminescent Mono- and Binuclear Cyclometalated Platinum(II) Complexes of 6-Phenyl-2,2‘-bipyridines , 1999 .

[16]  Zhang Liping,et al.  Synthesis and ion-binding studies of platinum(II) phenanthroline complexes containing crown ether moiety , 2006 .

[17]  Wei Lu,et al.  Light-emitting tridentate cyclometalated platinum(II) complexes containing sigma-alkynyl auxiliaries: tuning of photo- and electrophosphorescence. , 2004, Journal of the American Chemical Society.

[18]  V. Yam,et al.  Branched Carbon-Rich Luminescent Multinuclear Platinum(II) and Palladium(II) Alkynyl Complexes with Phosphine Ligands , 2009 .

[19]  R. P. Tang,et al.  Synthesis, Luminescence, Electrochemistry, and Ion-Binding Studies of Platinum(II) Terpyridyl Acetylide Complexes , 2001 .

[20]  Biwu Ma,et al.  Excimer and electron transfer quenching studies of a cyclometalated platinum complex , 2005 .

[21]  Andreas F. Rausch,et al.  Organometallic Pt(II) and Ir(III) Triplet Emitters for OLED Applications and the Role of Spin–Orbit Coupling: A Study Based on High-Resolution Optical Spectroscopy , 2010 .

[22]  F. Castellano,et al.  Photophysics in bipyridyl and terpyridyl platinum(II) acetylides , 2006 .

[23]  T. Wadas,et al.  Synthesis and characterization of platinum diimine bis(acetylide) complexes containing easily derivatizable aryl acetylide ligands. , 2003, Inorganic chemistry.

[24]  J. Williams,et al.  Optimising the luminescence of platinum(II) complexes and their application in organic light emitting devices (OLEDs) , 2008 .

[25]  Soma Chakraborty,et al.  Platinum chromophore-based systems for photoinduced charge separation: a molecular design approach for artificial photosynthesis. , 2005, Inorganic chemistry.

[26]  S. Forrest,et al.  Highly efficient phosphorescent emission from organic electroluminescent devices , 1998, Nature.

[27]  Katsumi Nakamaru.  Synthesis, Luminescence Quantum Yields, and Lifetimes of Trischelated Ruthenium(II) Mixed-ligand Complexes Including 3,3′-Dimethyl-2,2′-bipyridyl , 1982 .

[28]  J. Williams,et al.  Luminescent Platinum Compounds: From Molecules to OLEDs , 2010 .

[29]  K. Clays,et al.  Preparation and characterization of second order non-linear optical properties of new "push-pull" platinum complexes. , 2009, Dalton transactions.

[30]  J. Field,et al.  Push-pull effects and emission from ternary complexes of platinum(II), substituted terpyridines, and the strong-field cyanide ion. , 2005, Dalton transactions.

[31]  C. Che,et al.  Luminescent donor-acceptor platinum(ii) complexes , 1994 .

[32]  Stephen R. Forrest,et al.  White Organic Light‐Emitting Devices for Solid‐State Lighting , 2004 .

[33]  D. Cárdenas,et al.  Divergent Behavior of Palladium(II) and Platinum(II) in the Metalation of 1,3-Di(2-pyridyl)benzene , 1999 .

[34]  S. J. Farley,et al.  Controlling emission energy, self-quenching, and excimer formation in highly luminescent N--C--N-coordinated platinum(II) complexes. , 2005, Inorganic chemistry.

[35]  J. A. Gareth Williams,et al.  Photochemistry and Photophysics of Coordination Compounds: Platinum , 2007 .

[36]  Wai-Yeung Wong,et al.  Recent Progress on the Photonic Properties of Conjugated Organometallic Polymers Built Upon the trans-Bis(para-ethynylbenzene)bis(phosphine)platinum(II) Chromophore and Related Derivatives. , 2010, Macromolecular rapid communications.

[37]  C. Che,et al.  [(O--N--N)PtX] complexes as a new class of light-emitting materials for electrophosphorescent devices. , 2005, Inorganic chemistry.

[38]  Shubhashish Datta,et al.  Relationship between the ionization and oxidation potentials of molecular organic semiconductors , 2005 .

[39]  P. Mussini,et al.  The solvent effect in the electrocatalytic reduction of organic bromides on silver , 2006 .

[40]  Philip A. Gale,et al.  The coordination chemistry of dipyridylbenzene: N-deficient terpyridine or panacea for brightly luminescent metal complexes? , 2009, Chemical Society reviews.

[41]  Wai-Yeung Wong,et al.  Heavy metal organometallic electrophosphors derived from multi-component chromophores , 2009 .

[42]  J. Williams,et al.  Improving the performance of Pt(II) complexes for blue light emission by enhancing the molecular rigidity. , 2012, Inorganic chemistry.

[43]  P. Chou,et al.  Transition-metal phosphors with cyclometalating ligands: fundamentals and applications. , 2010, Chemical Society reviews.

[44]  J. Kalinowski,et al.  Highly efficient near-infrared organic excimer electrophosphorescent diodes , 2007 .

[45]  C. Tung,et al.  Long-lived emission from platinum(II) terpyridyl acetylide complexes. , 2002, Inorganic chemistry.

[46]  M. Cocchi,et al.  Cyclometallated platinum(II) complexes of 1,3-di(2-pyridyl)benzenes: tuning excimer emission from red to near-infrared for NIR-OLEDs , 2011 .

[47]  Vivian Wing-Wah Yam,et al.  Luminescence platinum(II) terpyridyl complexes—From fundamental studies to sensory functions , 2007 .

[48]  D. Hertel,et al.  Switching on luminescence by the self-assembly of a platinum(II) complex into gelating nanofibers and electroluminescent films. , 2011, Angewandte Chemie.

[49]  J. Demas,et al.  Quantum efficiencies of transition-metal complexes. I. d-d Luminescence , 1970 .

[50]  A. Beeby,et al.  An alternative route to highly luminescent platinum(II) complexes: cyclometalation with N=C=N-coordinating dipyridylbenzene ligands. , 2003, Inorganic chemistry.

[51]  J. Kalinowski,et al.  Bi-molecular emissive excited states in platinum (II) complexes for high-performance organic light-emitting diodes , 2010 .

[52]  C. Che,et al.  Photoresponsive supramolecular organometallic nanosheets induced by Pt(II)...Pt(II) and C-H...pi interactions. , 2009, Angewandte Chemie.