A cationic iridium(III) complex showing aggregation-induced phosphorescent emission (AIPE) in the solid state: synthesis, characterization and properties.

We report the synthesis and characterization of two cationic iridium(III) complexes with dendritic carbazole ligands as ancillary ligands, namely, [Ir(ppy)(2)L3]PF(6) (1) and [Ir(ppy)(2)L4]PF(6) (2), where L3 and L4 represent 3,8-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)-1,10-phenanthroline and 3,8-bis(3',6'-di-tert-butyl-6-(3,6-di-tert-butyl-9H-carbazol-9-yl)-3,9'-bi(9H-carbazol)-9-yl)-1,10-phenanthroline, respectively. Their photophysical properties have been investigated and compared. The results have shown that complex 2 is aggregation-induced phosphorescent emission (AIPE) active and exhibits the highest photoluminescent quantum yield (PLQY) of 16.2% in neat film among the reported cationic Ir(III) complexes with AIPE activity. In addition, it also enjoys redox reversibility, good film-forming ability, excellent thermal stability as well as off/on luminescence switching properties, revealing its potential application as a candidate for light-emitting electrochemical cells and organic vapor sensing. To explore applications in biology, 2 was used to image cells.

[1]  Yu Liu,et al.  A phosphorescent material with high and balanced carrier mobility for efficient OLEDs. , 2011, Chemical communications.

[2]  J. Qin,et al.  Synthesis, structure, electrochemistry, photophysics and electroluminescence of 1,3,4-oxadiazole-based ortho -metalated iridium(III) complexes , 2006 .

[3]  Henk J. Bolink,et al.  Efficient and Long‐Living Light‐Emitting Electrochemical Cells , 2010 .

[4]  M. Grätzel,et al.  Stable single-layer light-emitting electrochemical cell using 4,7-diphenyl-1,10-phenanthroline-bis(2-phenylpyridine)iridium(III) hexafluorophosphate. , 2006, Journal of the American Chemical Society.

[5]  P. Li,et al.  Creation of cationic iridium(III) complexes with aggregation-induced phosphorescent emission (AIPE) properties by increasing rotation groups on carbazole peripheries. , 2011, Dalton transactions.

[6]  Fuyou Li,et al.  Aggregation-induced phosphorescent emission (AIPE) of iridium(III) complexes. , 2008, Chemical communications.

[7]  K. Ryder,et al.  Tuning emission wavelength and redox properties through position of the substituent in iridium(III) cyclometallated complexes. , 2011, Dalton transactions.

[8]  Fuyou Li,et al.  A cyclometalated iridium(III) complex with enhanced phosphorescence emission in the solid state (EPESS): synthesis, characterization and its application in bioimaging. , 2011, Dalton transactions.

[9]  Qiang Zhao,et al.  Cationic iridium(III) complex containing both triarylboron and carbazole moieties as a ratiometric fluoride probe that utilizes a switchable triplet-singlet emission. , 2010, Chemistry.

[10]  Soo Young Park,et al.  Comment on 'aggregation-induced phosphorescent emission (AIPE) of iridium(III) complexes': origin of the enhanced phosphorescence. , 2008, Chemical communications.

[11]  V. Yam,et al.  Functionalized platinum(II) terpyridyl alkynyl complexes as colorimetric and luminescence pH sensors. , 2005, Inorganic chemistry.

[12]  Wai-Yeung Wong,et al.  A Multifunctional Iridium‐Carbazolyl Orange Phosphor for High‐Performance Two‐Element WOLED Exploiting Exciton‐Managed Fluorescence/Phosphorescence , 2008 .

[13]  Muhammed Yousufuddin,et al.  Synthetic control of excited-state properties in cyclometalated Ir(III) complexes using ancillary ligands. , 2005, Inorganic chemistry.

[14]  Sang-Don Jung,et al.  Enhanced emission and its switching in fluorescent organic nanoparticles. , 2002, Journal of the American Chemical Society.

[15]  K. Y. Zhang,et al.  Exploitation of the dual-emissive properties of cyclometalated iridium(III)-polypyridine complexes in the development of luminescent biological probes. , 2008, Angewandte Chemie.

[16]  G. Schmid,et al.  Positively Charged Iridium(III) Triazole Derivatives as Blue Emitters for Light‐Emitting Electrochemical Cells , 2010 .

[17]  Liduo Wang,et al.  Highly efficient solution-processed blue-green to red and white light-emitting diodes using cationic iridium complexes as dopants , 2010 .

[18]  Yongqiang Dong,et al.  Fluorescence enhancements of benzene-cored luminophors by restricted intramolecular rotations: AIE and AIEE effects. , 2007, Chemical communications.

[19]  C. Pearson,et al.  Efficient Deep-Blue Electroluminescence from an Ambipolar Fluorescent Emitter in a Single-Active-Layer Device , 2011 .

[20]  Shi Yuan Tang,et al.  A Molecular Glass for Deep‐Blue Organic Light‐Emitting Diodes Comprising a 9,9′‐Spirobifluorene Core and Peripheral Carbazole Groups , 2007 .

[21]  P. Chou,et al.  Bis(diphenylamino)-9,9′-spirobifluorene functionalized Ir(III) complex: a conceptual design en route to a three-in-one system possessing emitting core and electron and hole transport peripherals , 2011 .

[22]  Chunhui Huang,et al.  Polymer nanoparticles with an embedded phosphorescent osmium(II) complex for cell imaging , 2011 .

[23]  William A Goddard,et al.  Temperature dependence of blue phosphorescent cyclometalated Ir(III) complexes. , 2009, Journal of the American Chemical Society.

[24]  Liduo Wang,et al.  Blue‐Emitting Cationic Iridium Complexes with 2‐(1H‐Pyrazol‐1‐yl)pyridine as the Ancillary Ligand for Efficient Light‐Emitting Electrochemical Cells , 2008 .

[25]  C.‐c. Wu,et al.  Highly Efficient Orange and Green Solid‐State Light‐Emitting Electrochemical Cells Based on Cationic IrIII Complexes with Enhanced Steric Hindrance , 2007 .

[26]  H. Schmidt,et al.  Synthesis and Application of Dimeric 1,3,5-Triazine Ethers as Hole-Blocking Materials in Electroluminescent Devices , 1998 .

[27]  E. Ortí,et al.  Light-emitting electrochemical cells based on a supramolecularly-caged phenanthroline-based iridium complex. , 2011, Chemical communications.

[28]  S. Baek,et al.  Dinuclear Iridium(III) Complexes Linked by a Bis(β‐diketonato) Bridging Ligand: Energy Convergence versus Aggregation‐Induced Emission , 2010 .

[29]  Mei Han,et al.  Ruthenium(II) complexes of 6-hydroxydipyrido[3,2-a:2′,3′-c]phenazine: self-association, and concentration-dependent acid–base and DNA-binding properties , 2008 .

[30]  X. Jing,et al.  Bifunctional green iridium dendrimers with a "self-host" feature for highly efficient nondoped electrophosphorescent devices. , 2009, Angewandte Chemie.

[31]  Fuyou Li,et al.  π‐Conjugated Chelating Polymers with Charged Iridium Complexes in the Backbones: Synthesis, Characterization, Energy Transfer, and Electrochemical Properties , 2006 .

[32]  S. Bernhard,et al.  Homogeneous catalytic system for photoinduced hydrogen production utilizing iridium and rhodium complexes. , 2008, Inorganic chemistry.

[33]  N. McClenaghan,et al.  Ruthenium(II) dendrimers containing carbazole-based chromophores as branches. , 2003, Journal of the American Chemical Society.

[34]  Liduo Wang,et al.  Toward Highly Efficient Solid‐State White Light‐Emitting Electrochemical Cells: Blue‐Green to Red Emitting Cationic Iridium Complexes with Imidazole‐Type Ancillary Ligands , 2009 .

[35]  E. Ortí,et al.  Intramolecular pi-stacking in a phenylpyrazole-based iridium complex and its use in light-emitting electrochemical cells. , 2010, Journal of the American Chemical Society.

[36]  C. Stephenson,et al.  Visible-light photoredox catalysis: aza-Henry reactions via C-H functionalization. , 2010, Journal of the American Chemical Society.

[37]  C. Garino,et al.  Cationic heteroleptic cyclometalated iridium complexes with 1-pyridylimidazo[1,5-alpha]pyridine ligands: exploitation of an efficient intersystem crossing. , 2009, Chemistry.

[38]  Tao Yu,et al.  Triphenylethylene carbazole derivatives as a new class of AIE materials with strong blue light emission and high glass transition temperature , 2009 .

[39]  Fuyou Li,et al.  Phosphorescent chemosensors based on heavy-metal complexes. , 2010, Chemical Society reviews.

[40]  Liduo Wang,et al.  Enhanced stability of blue-green light-emitting electrochemical cells based on a cationic iridium complex with 2-(1-phenyl-1H-pyrazol-3-yl)pyridine as the ancillary ligand. , 2011, Chemical Communications.

[41]  Yanhu Li,et al.  Efficient sky-blue and blue-green light-emitting electrochemical cells based on cationic iridium complexes using 1,2,4-triazole-pyridine as the ancillary ligand with cyanogen group in alkyl chain , 2011 .

[42]  Jamshidi,et al.  Conjugated 1,10-Phenanthrolines as Tunable Fluorophores. , 1999, Angewandte Chemie.

[43]  Fuyou Li,et al.  Phosphorescence imaging of homocysteine and cysteine in living cells based on a cationic iridium(III) complex. , 2010, Inorganic chemistry.

[44]  Yun Chi,et al.  Color tuning associated with heteroleptic cyclometalated Ir(III) complexes: influence of the ancillary ligand. , 2007, Dalton transactions.

[45]  Efficient deep-blue emitters comprised of an anthracene core and terminal bifunctional groups for nondoped electroluminescence , 2011 .

[46]  Liduo Wang,et al.  Highly Efficient Blue-Green and White Light-Emitting Electrochemical Cells Based on a Cationic Iridium Complex with a Bulky Side Group , 2010 .

[47]  Yi‐Hung Liu,et al.  Solid-state white light-emitting electrochemical cells using iridium-based cationic transition metal complexes. , 2008, Journal of the American Chemical Society.

[48]  Simona Garon,et al.  Cationic bis-cyclometalated iridium(III) diimine complexes and their use in efficient blue, green, and red electroluminescent devices. , 2005, Inorganic chemistry.

[49]  Parr,et al.  Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. , 1988, Physical review. B, Condensed matter.

[50]  H. Kwok,et al.  Efficient Organic Light‐Emitting Diodes based on Sublimable Charged Iridium Phosphorescent Emitters , 2007 .

[51]  M. Grätzel,et al.  Efficient green-blue-light-emitting cationic iridium complex for light-emitting electrochemical cells. , 2006, Inorganic chemistry.

[52]  Richard Eisenberg,et al.  Vapochromism and its structural basis in a luminescent Pt(II) terpyridine-nicotinamide complex. , 2004, Journal of the American Chemical Society.

[53]  Fuyou Li,et al.  Cationic iridium(III) complexes for phosphorescence staining in the cytoplasm of living cells. , 2008, Chemical communications.

[54]  Yue Wang,et al.  Carbazolyl-contained phenol-pyridyl boron complexes: syntheses, structures, photoluminescent and electroluminescent properties. , 2010, Dalton transactions.

[55]  J. Fernández-Hernández,et al.  Control of the mutual arrangement of cyclometalated ligands in cationic iridium(III) complexes. Synthesis, spectroscopy, and electroluminescence of the different isomers. , 2011, Journal of the American Chemical Society.

[56]  Xiabin Jing,et al.  Highly Efficient Green‐Emitting Phosphorescent Iridium Dendrimers Based on Carbazole Dendrons , 2006 .

[57]  R. Pascal,et al.  Accelerated luminophore discovery through combinatorial synthesis. , 2004, Journal of the American Chemical Society.

[58]  S. Bernhard,et al.  Synthetically tailored excited states: phosphorescent, cyclometalated iridium(III) complexes and their applications. , 2006, Chemistry.

[59]  K. Y. Zhang,et al.  Synthesis, properties, and live-cell imaging studies of luminescent cyclometalated iridium(III) polypyridine complexes containing two or three biotin pendants. , 2009, Inorganic chemistry.

[60]  Qiang Zhao,et al.  Series of new cationic iridium(III) complexes with tunable emission wavelength and excited state properties: structures, theoretical calculations, and photophysical and electrochemical properties. , 2006, Inorganic chemistry.

[61]  A. Monkman,et al.  Cationic bis-cyclometallated iridium(III) phenanthroline complexes with pendant fluorenyl substituents: synthesis, redox, photophysical properties and light-emitting cells. , 2008, Chemistry.

[62]  Andreas Winter,et al.  Recent Developments in the Application of Phosphorescent Iridium(III) Complex Systems , 2009 .

[63]  E. Ortí,et al.  Origin of the large spectral shift in electroluminescence in a blue light emitting cationic iridium(III) complex , 2007 .

[64]  Tae‐Hyuk Kwon,et al.  New Approach Toward Fast Response Light‐Emitting Electrochemical Cells Based on Neutral Iridium Complexes via Cation Transport , 2009 .

[65]  C. Che,et al.  "Turn-on" FRET-based luminescent iridium(III) probes for the detection of cysteine and homocysteine. , 2011, Chemical communications.

[66]  K. K. Lo,et al.  Luminescent cyclometallated iridium(III) bis(quinolylbenzaldehyde) diimine complexes--synthesis, photophysics, electrochemistry, protein cross-linking properties, cytotoxicity and cellular uptake. , 2011, Dalton transactions.

[67]  A. Becke.  Density-functional thermochemistry. III. The role of exact exchange , 1993 .

[68]  V. Yam,et al.  Solvent-induced aggregation through metal...metal/pi...pi interactions: large solvatochromism of luminescent organoplatinum(II) terpyridyl complexes. , 2002, Journal of the American Chemical Society.

[69]  Yun Chi,et al.  En Route to High External Quantum Efficiency (∼12%), Organic True‐Blue‐Light‐Emitting Diodes Employing Novel Design of Iridium (III) Phosphors , 2009 .

[70]  Kimihisa Yamamoto,et al.  Synthesis of Asymmetrically Arranged Dendrimers with a Carbazole Dendron and a Phenylazomethine Dendron , 2004 .

[71]  Michele Muccini,et al.  The role of substituents on functionalized 1,10-phenanthroline in controlling the emission properties of cationic iridium(III) complexes of interest for electroluminescent devices. , 2007, Inorganic chemistry.

[72]  Alon A Gorodetsky,et al.  Efficient yellow electroluminescence from a single layer of a cyclometalated iridium complex. , 2004, Journal of the American Chemical Society.

[73]  Qiang Zhao,et al.  FRET-based probe for fluoride based on a phosphorescent iridium(III) complex containing triarylboron groups , 2011 .

[74]  Weiwen He,et al.  Water-Soluble and Biocompatible Cyclometalated Iridium(III) Complexes: Synthesis, Luminescence and Sensing Application , 2011 .

[75]  Guangming Li,et al.  Small molecular glasses based on multiposition encapsulated phenyl benzimidazole iridium(III) complexes: toward efficient solution-processable host-free electrophosphorescent diodes. , 2010, The journal of physical chemistry. B.

[76]  Dik‐Lung Ma,et al.  A highly selective luminescent switch-on probe for histidine/histidine-rich proteins and its application in protein staining. , 2008, Angewandte Chemie.

[77]  M. Rubner,et al.  Thin film light emitting devices from an electroluminescent ruthenium complex , 1996 .