Control of intramolecular π-π stacking interaction in cationic iridium complexes via fluorination of pendant phenyl rings

Intramolecular π-π stacking interaction in one kind of phosphorescent cationic iridium complexes has been controlled through fluorination of the pendant phenyl rings on the ancillary ligands. Two blue-green-emitting cationic iridium complexes, [Ir(ppy)(2)(F2phpzpy)]PF(6) (2) and [Ir(ppy)(2)(F5phpzpy)]PF(6) (3), with the pendant phenyl rings on the ancillary ligands substituted with two and five fluorine atoms, respectively, have been synthesized and compared to the parent complex, [Ir(ppy)(2)(phpzpy)]PF(6) (1). Here Hppy is 2-phenylpyridine, F2phpzpy is 2-(1-(3,5-difluorophenyl)-1H-pyrazol-3-yl)pyridine, F5phpzpy is 2-(1-pentafluorophenyl-1H-pyrazol-3-yl)-pyridine, and phpzpy is 2-(1-phenyl-1H-pyrazol-3-yl)pyridine. Single crystal structures reveal that the pendant phenyl rings on the ancillary ligands stack to the phenyl rings of the ppy ligands, with dihedral angles of 21°, 18°, and 5.0° between least-squares planes for complexes 1, 2, and 3, respectively, and centroid-centroid distances of 3.75, 3.65, and 3.52 ? for complexes 1, 2, and 3, respectively, indicating progressively reinforced intramolecular π-π stacking interactions from complexes 1 to 2 and 3. Compared to complex 1, complex 3 with a significantly reinforced intramolecular face-to-face π-π stacking interaction exhibits a significantly enhanced (by 1 order of magnitude) photoluminescent efficiency in solution. Theoretical calculations reveal that in complex 3 it is unfavorable in energy for the pentafluorophenyl ring to swing by a large degree and the intramolecular π-π stacking interaction remains on the lowest triplet state.     

Synthesis, characterisation and application of iridium(III) photosensitisers for catalytic water reduction

The synthesis of novel, monocationic iridium(III) photosensitisers (Ir-PSs) with the general formula [Ir(III)(C^N)(2)(N^N)](+) (C^N: cyclometallating phenylpyridine ligand, N^N: neutral bidentate ligand) is described. The structures obtained were examined by cyclic voltammetry, UV/Vis and photoluminescence spectroscopy and X-ray analysis. All iridium complexes were tested for their ability as photosensitisers to promote homogeneously catalysed hydrogen generation from water. In the presence of [HNEt(3)][HFe(3)(CO)(11)] as a water-reduction catalyst (WRC) and triethylamine as a sacrificial reductant (SR), seven of the new iridium complexes showed activity. [Ir(6-iPr-bpy)(ppy)(2)]PF(6) (bpy: 2,2'-bipyridine, ppy: 2-phenylpyridine) turned out to be the most efficient photosensitiser. This complex was also tested in combination with other WRCs based on rhodium, platinum, cobalt and manganese. In all cases, significant hydrogen evolution took place. Maximum turnover numbers of 4550 for this Ir-PS and 2770 for the Fe WRC generated in situ from [HNEt(3)][HFe(3)(CO)(11)] and tris[3,5-bis(trifluoromethyl)phenyl]phosphine was obtained. These are the highest overall efficiencies for any Ir/Fe water-reduction system reported to date. The incident photon to hydrogen yield reaches 16.4% with the best system.     

Synthesis, characteristics and photoluminescent properties of novel Ir-Eu heteronuclear complexes containing 2-carboxyl-pyrimidine as a bridging ligand

Two novel iridium(III) complexes, [Ir(dfppy)(2)(pmc)] and [Ir(ppy)(2)(pmc)] (dfppy = 2-(4',6'-difluoro-phenyl)pyridine, ppy = 1-phenyl-pyridine), were designed and synthesized using 2-carboxyl-pyrimidine (Hpmc) as an ancillary ligand. Single crystals were obtained and characterized by single crystal X-ray diffraction. The tetrametallic complexes {[(C^N)(2)Ir(μ-pmc)](3)EuCl(3)} (C^N = dfppy, ppy) were synthesized using the iridium(III) complexes as "ligands". Photophysical and theoretical studies indicate that [Ir(dfppy)(2)(pmc)] is more suitable for sensitizing the emission of Eu(III) ions than [Ir(ppy)(2)(pmc)].     

The role of substituents on functionalized 1,10-phenanthroline in controlling the emission properties of cationic iridium(III) complexes of interest for electroluminescent devices

The photophysical and electrochemical properties of the novel complexes [Ir(ppy)(2)(5-X-1,10-phen)][PF(6)] (ppy = 2-phenylpyridine, phen = phenanthroline, X = NMe(2), NO(2)), [Ir(pq)(2)(5-X-1,10-phen)][PF(6)] (pq = 2-phenylquinoline, X = H, Me, NMe(2), NO(2)), [Ir(ppy)2(4-Me,7-Me-1,10-phen)][PF(6)], [Ir(ppy)2(5-Me,6-Me-1,10-phen)][PF(6)], [Ir(ppy)(2)(2-Me,9-Me-1,10-phen)][PF(6)], and [Ir(pq)2(4-Ph,7-Ph-1,10-phen)][PF(6)] have been investigated and compared with those of the known reference complexes [Ir(ppy)(2)(4-Me or 5-H or 5-Me-1,10-phen)][PF(6)] and [Ir(ppy)(2)(4-Ph,7-Ph-1,10-phen)][PF(6)], showing how the nature and number of the phenanthroline substituents tune the color of the emission, its quantum yield, and the emission lifetime. It turns out that the quantum yield is strongly dependent on the nonradiative decay. The geometry, ground state, electronic structure, and excited electronic states of the investigated complexes have been calculated on the basis of density functional theory (DFT) and time-dependent DFT approaches, thus substantiating the electrochemical measurements and providing insight into the electronic origin of the absorption spectra and of the lowest excited states involved in the light emission process. These results provide useful guidelines for further tailoring of the photophysical properties of ionic Ir(III) complexes.     

Cyclometallated Pt(II) and Pd(II) complexes with a trithiacrown ligand

We report the synthesis and full characterization for a series of cyclometallated complexes of Pt(II) and Pd(II) incorporating the fluxional trithiacrown ligand 1,4,7-trithiacyclononane ([9]aneS3). Reaction of [M(C insertion mark N)(micro-Cl)]2 (M = Pt(II), Pd(II); C insertion mark N = 2-phenylpyridinate (ppy) or 7,8-benzoquinolinate (bzq)) with [9]aneS3 followed by metathesis with NH4PF6 yields [M(C insertion mark N)([9]aneS3)](PF6). The complexes [M(C insertion mark P)([9]aneS3)](PF6) (M = Pt(II), Pd(II); Cinsertion markP = [CH2C6H4P(o-tolyl)2-C,P]-) were synthesized from their respective [Pt(C insertion mark P)(micro-Cl)]2 or [Pd(C insertion mark P)(micro-O2CCH3)]2 (C insertion mark P) starting materials. All five new complexes have been fully characterized by multinuclear NMR, IR and UV-Vis spectroscopies in addition to elemental analysis, cyclic voltammetry, and single-crystal structural determinations. As expected, the coordinated [9]aneS3 ligand shows fluxional behavior in its NMR spectra, resulting in a single 13C NMR resonance despite the asymmetric coordination environment of the cyclometallating ligand. Electrochemical studies reveal irreversible one-electron metal-centered oxidations for all Pt(II) complexes, but unusual two-electron reversible oxidations for the Pd(II) complexes of ppy and bzq. The X-ray crystal structures of each complex indicate an axial M-S interaction formed by the endodentate conformation of the [9]aneS3 ligand. The structure of [Pd(bzq)([9]aneS3)](PF6) exhibits disorder in the [9]aneS3 conformation indicating a rare exodentate conformation as the major contributor in the solid-state structure. DFT calculations on [Pt([9]aneS3)(ppy)](PF6) and [Pd([9]aneS3)(ppy)](PF6) indicate the HOMO for both complexes is primarily dz2 in character with a significant contribution from the phenyl ring of the ppy ligand and p orbital of the axial sulfur donor. In contrast, the calculated LUMO is primarily ppy pi* in character for [Pt([9]aneS3)(ppy)](PF6), but dx2-y2 in character for [Pd([9]aneS3)(ppy)](PF6).     

Acid-induced degradation of phosphorescent dopants for OLEDs and its application to the synthesis of tris-heteroleptic iridium(III) bis-cyclometalated complexes

Investigations of blue phosphorescent organic light emitting diodes (OLEDs) based on [Ir(2-(2,4-difluorophenyl)pyridine)(2)(picolinate)] (FIrPic) have pointed to the cleavage of the picolinate as a possible reason for device instability. We reproduced the loss of picolinate and acetylacetonate ancillary ligands in solution by the addition of Br?nsted or Lewis acids. When hydrochloric acid is added to a solution of a [Ir(C^N)(2)(X^O)] complex (C^N = 2-phenylpyridine (ppy) or 2-(2,4-difluorophenyl)pyridine (diFppy) and X^O = picolinate (pic) or acetylacetonate (acac)), the cleavage of the ancillary ligand results in the direct formation of the chloro-bridged iridium(III) dimer [{Ir(C^N)(2)(μ-Cl)}(2)]. When triflic acid or boron trifluoride are used, a source of chloride (here tetrabutylammonium chloride) is added to obtain the same chloro-bridged iridium(III) dimer. Then, we advantageously used this degradation reaction for the efficient synthesis of tris-heteroleptic cyclometalated iridium(III) complexes [Ir(C^N(1))(C^N(2))(L)], a family of cyclometalated complexes otherwise challenging to prepare. We used an iridium(I) complex, [{Ir(COD)(μ-Cl)}(2)], and a stoichiometric amount of two different C^N ligands (C^N(1) = ppy; C^N(2) = diFppy) as starting materials for the swift preparation of the chloro-bridged iridium(III) dimers. After reacting the mixture with acetylacetonate and subsequent purification, the tris-heteroleptic complex [Ir(ppy)(diFppy)(acac)] could be isolated with good yield from the crude containing as well the bis-heteroleptic complexes [Ir(ppy)(2)(acac)] and [Ir(diFppy)(2)(acac)]. Reaction of the tris-heteroleptic acac complex with hydrochloric acid gives pure heteroleptic chloro-bridged iridium dimer [{Ir(ppy)(diFppy)(μ-Cl)}(2)], which can be used as starting material for the preparation of a new tris-heteroleptic iridium(III) complex based on these two C^N ligands. Finally, we use DFT/LR-TDDFT to rationalize the impact of the two different C^N ligands on the observed photophysical and electrochemical properties.     

Study on a set of bis-cyclometalated Ir(III) complexes with a common ancillary ligand

Bis-cyclometalated iridium(iii) complexes [Ir(F(2)ppy)(2)] (), [Ir(F(2)CNppy)(2)] (), [Ir(DMAF(2)ppy)(2)] () and [Ir(MeOF(2)ppy)(2)] () (F(2)ppy = 4',6'-difluoro-2-phenylpyridinate, F(2)CNppy = 5'-cyano-4',6'-difluoro-2-phenylpyridinate, DMAF(2)ppy = 4',6'-difluoro-4-dimethylamino-2-phenylpyridinate, MeOF(2)ppy = 4',6'-difluoro-4-methyl-2-phenylpyridinate and = 3,5-dimethylpyrazole-N-carboxamide) emitting in the sky blue region were synthesized. We studied the effect of the ancillary ligand and the substituents on the cyclometalating ligands on the crystal structures, photophysical and electrochemical properties and the frontier orbitals. Density functional theory (DFT) calculation results indicate that in and the cyclometalating ligands show negligible participation in the HOMO, the ancillary ligand being the main participant along with the Ir(iii) d-orbitals. exhibits the maximum photoluminescence quantum efficiency and radiative emission rates along with the dominant low frequency metal-ligand vibrations and maximum reorganization energy in the excited state. All the substituted complexes show more polar characteristics than , possessing the highest dipole moment among the complexes. The performances of the solution-synthesised organic light emitting devices (OLEDs) of , and doped in a blend of mCP (m-bis(N-carbazolylbenzene)) and polystyrene are studied.     

A cyclometalated iridium(III) complex with enhanced phosphorescence emission in the solid state (EPESS): synthesis, characterization and its application in bioimaging

Iridium(III) complexes with intense phosphorescence in solution have been widely applied in organic light-emitting diodes, chemosensors and bioimaging. However, little attention has been paid to iridium(III) complexes showing weak phosphorescence in solution and enhanced phosphorescence emission in the solid state (EPESS). In the present study, two β-diketonate ligands with different degrees of conjugation, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HL1) and 1-phenyl-3-methyl-4-phenylacetyl-5-pyrazolone (HL2), have been synthesized to be used as ancillary ligands for two iridium(III) complexes, Ir(ppy)(2)(L1) and Ir(ppy)(2)(L2) (Hppy = 2-phenylpyridine). The two complexes have been characterized by single-crystal X-ray crystallography, (1)H NMR and elemental analysis. Interestingly, Ir(ppy)(2)(L1) is EPESS-active whereas Ir(ppy)(2)(L2) exhibits moderately intense emission both in solution and as a neat film, indicating that the degree of conjugation of the β-diketone ligands determines the EPESS-activity. The single-crystal X-ray analysis has indicated that there are π-π interactions between the adjacent ppy ligands in Ir(ppy)(2)(L1) but not in Ir(ppy)(2)(L2). Finally, EPESS-active Ir(ppy)(2)(L1) has been successfully embedded in polymer nanoparticles and used as a luminescent label in bioimaging.     

Design and synthesis of iridium bis(carbene) complexes for efficient blue electrophosphorescence

Five iridium bis(carbene) complexes, [Ir(pmi)(2)(pypz)] (1), [Ir(mpmi)(2)(pypz)] (2), [Ir(fpmi)(2)(pypz)] (3), [Ir(fpmi)(2)(pyim)] (4), and [Ir(fpmi)(2)(tfpypz)] (5) (pmi=1-phenyl-3-methylimdazolin-2-ylidene-C,C(2'); fpmi=1-(4-fluorophenyl)-3-methylimdazolin-2-ylidene-C,C(2'); mpmi=1-(4-methyl-phenyl)-3-methylimdazolin-2-ylidene-C,C(2'); pypz=2-(1H-pyrazol-5-yl)pyridinato; pyim=2-(1H-imidazol-2-yl)pyridinato; and tfpypz=2-(3-(trifluoromethyl)-1H-pyrazol-5-yl)pyridinato), were synthesized and their structures were characterized by NMR spectroscopy, mass spectroscopy and X-ray diffraction. These complexes showed phosphorescent emission with the emission maxima between 453 and 490 nm. Various spectrophotometric measurements, cyclic voltammetric studies, and density functional theory (DFT) calculations show that, unlike most of the phosphorescent cyclometalated iridium complexes, the lowest unoccupied molecular orbital (LUMO) energy and the emissive state of these iridium complexes are mainly controlled by the N,N'-heteroaromatic (N^N) ligand. Despite the fact that the LUMO levels of these complexes are mainly on the N^N ligands, the efficiencies of the electroluminescent (EL) devices are very high. For example, the EL devices using [Ir(mpmi)(2)(pypz)], [Ir(fpmi)(2)(pypz)], and [Ir(fpmi)(2)(tfpypz)] as the dopant emitters exhibited light- to deep-blue electrophosphorescence with external quantum efficiencies of 15.2, 14.1, and 7.6% and Commission Internationale d'énclairage (x,y) coordinates (CIE(x,y)) of (0.14, 0.27), (0.14, 0.18) and (0.14, 0.10), respectively.     

Creation of cationic iridium(III) complexes with aggregation-induced phosphorescent emission (AIPE) properties by increasing rotation groups on carbazole peripheries

Three cationic iridium complexes containing 4,7-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)-1,10-phenanthroline (L(1)) and 4,7-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 (L(2)) as the ancillary ligands, namely, [Ir(ppy)(2)(L(1))]PF(6) (1), [Ir(ppy)(2)(L(2))]PF(6) (2) and [Ir(oxd)(2)(L(2))]PF(6) (3) (ppy is 2-phenylpyridine, oxd is 2,5-diphenyl-1,3,4-oxadiazole), have been designed and prepared. With more intramolecular rotational units on the ancillary ligand (L(2)), 2 and 3 possess a unique aggregation-induced phosphorescent emission (AIPE) property. This phenomenon was unprecedentedly observed in the cationic iridium(III) complexes. In order to investigate the underlying mechanism of this AIPE behavior, their photophysical, temperature-dependent aggregation properties as well as theoretical calculations, were performed. The results suggest that restricted intramolecular rotation is responsible for the AIPE of cationic complexes. Moreover, photoluminescent quantum yields in the neat film, thermal stabilities and off/on luminescence switching of 2 were investigated, revealing its potential application as a candidate for LECs and organic vapor sensing.     

Phosphorescent iridium(III) complex with an N^O ligand as a Hg(2+)-selective chemodosimeter and logic gate

Phosphorescent iridium(III) complexes have been attracting increasing attention in applications as luminescent chemosensors. However, no instance of an iridium(III) complex being used as a molecular logic gate has hitherto been reported. In the present study, two iridium(III) complexes, [Ir(ppy)(2)(PBT)] and [Ir(ppy)(2)(PBO)], have been synthesized (PBT, 2-(2-Hydroxyphenyl)-benzothiazole; PBO, 2-(2-hydroxyphenyl)-benzoxazole), and their chemical structures have been characterized by single-crystal X-ray analysis. Theoretical calculations and detailed studies of the photophysical and electrochemical properties of these two complexes have shown that the N^O ligands dominate their luminescence emission properties. Moreover, [Ir(ppy)(2)(PBT)], containing a sulfur atom in the N^O ligand, can serve as a highly selective chemodosimeter for Hg(2+) with ratiometric and naked-eye detection, which is associated with the dissociation of the N^O ligand PBT from the complex. Furthermore, complex [Ir(ppy)(2)(PBT)] has been further developed as an AND and INHIBIT logic gate with Hg(2+) and histidine as inputs.     

Stereochemistry controlled by an asymmetric sulfur atom, and a rare example of a kryptoracemate

The ligands 4-methylthio-6-phenyl-2,2'-bipyridine (1) and the corresponding sulfoxide (2) and sulfone (3) have been synthesized and characterized in solution, and in the solid state by single crystal X-ray diffraction. Compounds 2 and 3 crystallize in the same space group (C2/c) with similar unit cell parameters; a small increase in the unit cell volume allows for the presence of the extra oxygen atom in 3. The sulfoxide and sulfone groups adopt conformations that permit intramolecular OHC(aryl) hydrogen bonds. The complexes [Ir(ppy)(2)L][PF(6)] with L = 1, 2 or 3 have been prepared and characterized. The asymmetric sulfur atom in ligand 2 gives rise to pairs of diastereoisomers of the complex which can be distinguished in the (1)H and (13)C NMR spectra. In solution, exchange of [PF(6)](-) by [Δ-TRISPHAT](-) gives rise to four diastereoisomers and we observed good dispersion of (1)H NMR resonances, especially for those assigned to protons close to the asymmetric sulfur atom. A single crystal X-ray diffraction study of 2{[Ir(ppy)(2)(3)][PF(6)]}·CHCl(3)·3H(2)O reveals that the complex crystallizes in the chiral space group P2(1)2(1)2(1), the asymmetric unit containing crystallographically independent Δ- and Λ-[Ir(ppy)(2)(3)](+) cations. This provides a rare example of a so-called kryptoracemate in the solid state. In MeCN solution, [Ir(ppy)(2)(1)][PF(6)], [Ir(ppy)(2)(2)][PF(6)] and [Ir(ppy)(2)(3)][PF(6)] are weakly emissive (λ(em) = 600, 647 and 672 nm, respectively) and preliminary studies of the electroluminescent properties of [Ir(ppy)(2)(2)][PF(6)] indicate that the complexes are not suitable candidates for LECs.     

Novel dinuclear luminescent compounds based on iridium(III) cyclometalated chromophores and containing bridging ligands with ester-linked chelating sites

The syntheses and study of the spectroscopic, redox, and photophysical properties of a new set of species based on Ir(III) cyclometalated building blocks are reported. This set includes three dinuclear complexes, that is, the symmetric (with respect to the bridging ligand) diiridium species [(ppy)(2)Ir(mu-L-OC(O)-C(O)O-L)Ir(ppy)(2)][PF(6)](2) (5; ppy = 2-phenylpyridine anion; L-OC(O)-C(O)O-L = bis[4-(6'-phenyl-2,2'-bipyridine-4'-yl)phenyl]-benzene-1,4-dicarboxylate), the asymmetric diiridium species [(ppy)(2)Ir(mu-L-OC(O)-L)Ir(ppy)(2)][PF(6)](2) (3; L-OC(O)-L = 4-([(6'-phenyl-2,2'-bipyridine-4'-yl)benzoyloxy]phenyl)-6'-phenyl-2,2'-bipyridine), and the mixed-metal Ir-Re species [(ppy)(2)Ir(mu-L-OC(O)-L)Re(CO)(3)Br][PF(6)] (4). Syntheses, characterization, and spectroscopic, photophysical, and redox properties of the model mononuclear compounds [Ir(ppy)(2)(L-OC(O)-L)][PF(6)] (2) and [Re(CO)(3)(L-COOH)Br] (6; L-COOH = 4'-(4-carboxyphenyl)-6'-phenyl-2,2'-bipyridine) are also reported, together with the syntheses of the new bridging ligands L-OC(O)-L and L-OC(O)-C(O)O-L. The absorption spectra of all the complexes are dominated by intense spin-allowed ligand-centered (LC) bands and by moderately intense spin-allowed metal-to-ligand charge-transfer (MLCT) bands. Spin-forbidden MLCT absorption bands are also visible as low-energy tails at around 470 nm for all the complexes. All the new species exhibit metal-based irreversible oxidation and bipyridine-based reversible reduction processes in the potential window investigated (between +1.80 and -1.70 V vs SCE). The redox behavior indicates that the metal-based orbitals are only weakly interacting in dinuclear systems, whereas the two chelating halves of the bridging ligands exhibit noticeable electronic interactions. All the complexes are luminescent both at 77 K and at room temperature, with emission originating from triplet MLCT states. The luminescence properties are temperature- and solvent-dependent, in accord with general theories: emission lifetimes and quantum yields increase on passing from acetonitrile to dichloromethane fluid solution and from room-temperature fluid solution to 77 K rigid matrix. In the dinuclear mixed-chromophore species 3 and 4, photoinduced energy transfer across the ester-linked bridging ligands seems to occur with low efficiency.     

Light-emitting electrochemical cells based on a supramolecularly-caged phenanthroline-based iridium complex

The complex [Ir(ppy)(2)(pphen)][PF(6)] (Hppy = 2-phenylpyridine, pphen = 2-phenyl-1,10-phenanthroline) has been prepared and evaluated as an electroluminescent component for light-emitting electrochemical cells (LECs). Like in analogous LECs using bpy-based iridium(III) complexes a significant enhancement of the device stability is observed.     

新型含吡咯亚胺基辅助配体的金属铱(III)配合物的 合成、表征及发光性质

合成了一系列含有吡咯亚胺基为辅助配体的2-苯基吡啶铱配合物[(ppy)2Ir(N^N)] (ppy＝2-苯基吡啶), 通过1H NMR, MS, HRMS和元素分析对配合物结构进行了表征, 并研究了合成配合物的反应条件、紫外吸收光谱、光致发光光谱及铱配合物荧光量子产率. 结果表明, 在无水乙酸钠、二氯甲烷溶液中, 室温反应12 h可获得较高的产率. 通过改变吡咯亚胺类配体中的取代基, 该类配合物在507～606 nm之间具有不同的发光波长, 实现了从绿光到红光的转变. 所有的铱配合物在二氯甲烷溶液(空气中)表现出较高的量子效率(0.25～0.95).     

Selective low-temperature syntheses of facial and meridional tris-cyclometalated iridium(III) complexes

We have developed a selective low-temperature synthesis of fac and mer tris-cyclometalated Ir(III) complexes. The chloro-bridged dimers [Ir(CwedgeN)2Cl]2 (CwedgeN = cyclometalating ligand) are cleaved in coordinating solvents like acetonitrile to give neutral Ir(CwedgeN)2(NCCH3)Cl species which in turn are reacted with AgPF6 to give hexafluorophosphate salts of the bis-acetonitrile species [Ir(CwedgeN)2(NCCH3)2]PF6 for CwedgeN = 2,2'-thienylpyridine (thpy) and 2-phenylpyridine (ppy). These bis-acetonitrile complexes are excellent starting materials for the synthesis of tris-Ir(III) complexes. The complexes of the general formula fac-Ir(CwedgeN)3 were synthesized with the ligands thpy and ppy at 100 degrees C in o-dichlorobenzene from the corresponding [Ir(CwedgeN)2(NCCH3)2]PF6 complexes. The reaction of [Ir(CwedgeN)2(NCCH3)2]PF6 with thpy at room temperature did not give the expected tris complex but instead gave [Ir(thpy)2(N,S-thpy)]PF6, with the third chelating ligand complexed through the sulfur atom of the thiophene ring. [Ir(thpy)2Cl]2, [Ir(ppy)2Cl]2, Ir(thpy)2(NCCH3)Cl, [Ir(thpy)2(NCCH3)2]PF6, [Ir(ppy)2(NCCH3)2]PF6, and [Ir(thpy)2(N,S-thpy)]PF6 were structurally characterized by X-ray crystallography. Additionally, hydroxy-bridged dimers, [Ir(CwedgeN)2(OH)]2, were synthesized as starting materials for the selective synthesis of mer-Ir(CwedgeN)3 complexes at 100 degrees C in o-dichlorobenzene. A mechanism is proposed that may account for the selectivity observed in the formation of the mer-Ir(CwedgeN)3 and fac-Ir(CwedgeN)3 isomers in previous studies and the studies presented here.     

Luminescent cyclometalated iridium(III) polypyridine di-2-picolylamine complexes: synthesis, photophysics, electrochemistry, cation binding, cellular internalization, and cytotoxic activity

A series of luminescent cyclometalated iridium(III) polypyridine complexes containing a di-2-picolylamine (DPA) moiety [Ir(N^C)(2)(phen-DPA)](PF(6)) (phen-DPA = 5-(di-2-picolylamino)-1,10-phenanthroline) (HN^C = 2-phenylpyridine, Hppy (1a), 2-(4-methylphenyl)pyridine, Hmppy (2a), 2-phenylquinoline, Hpq (3a), 4-(2-pyridyl)benzaldehyde, Hpba (4a)) and their DPA-free counterparts [Ir(N^C)(2)(phen-DMA)](PF(6)) (phen-DMA = 5-(dimethylamino)-1,10-phenanthroline) (HN^C = Hppy (1b), Hmppy (2b), Hpq (3b), Hpba (4b)) have been synthesized and characterized, and their photophysical and electrochemical properties investigated. Photoexcitation of the complexes in fluid solutions at 298 K and in alcohol glass at 77 K resulted in intense and long-lived luminescence. The emission of the complexes has been assigned to a triplet metal-to-ligand charge-transfer ((3)MLCT) (dπ(Ir) → π*(N^N)) or triplet intraligand ((3)IL) (π → π*) (N^C) excited state and with substantial mixing of triplet amine-to-ligand charge-transfer ((3)NLCT) (n → π*) (N^N) character, depending on the identity of the cyclometalating and diimine ligands. Electrochemical measurements revealed an irreversible amine oxidation wave at ca. +1.1 to +1.2 V vs saturated calomel electrode, a quasi-reversible iridium(IV/III) couple at ca. +1.2 to +1.6 V, and a reversible diimine reduction couple at ca. -1.4 to -1.5 V. The cation-binding properties of these complexes have been studied by emission spectroscopy. Upon binding of zinc ion, the iridium(III) DPA complexes displayed 1.2- to 5.4-fold emission enhancement, and the K(d) values determined were on the order of 10(-5) M. Job's plot analysis confirmed that the binding stoichiometry was 1:1. Additionally, selectivity studies showed that the iridium(III) DPA complexes were more sensitive toward zinc ion among various transition metal ions examined. Furthermore, the cytotoxicity of these complexes toward human cervix epithelioid carcinoma cells have been studied by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide assay and their cellular-uptake properties by inductively coupled plasma mass spectrometry and laser-scanning confocal microscopy.     

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.     

Ruthenium(II) complexes of 1,12-diazaperylene and their interactions with DNA

Four complexes of the ligand 1,12-diazaperylene (DAP) have been prepared, [Ru(bpy)n(DAP)(3-n)]2+ where n = 0-2 and [Ru(DAP)3]2+. The [Ru(DAP)3]2+ complex was characterized by X-ray analysis and was found to exhibit the expected propeller-like structure with significant intermolecular pi-stacking interactions. The three Ru(II) complexes showed self-consistent optoelectronic properties with similar ligand-centered pi-pi* absorptions in the range of 333-468 nm and MLCT bands associated with the DAP which increased in intensity and decreased in energy as the number of DAP ligands varied from 1 to 3. Hypochromicity and viscosity changes were observed that were consistent with DAP intercalation into DNA, and binding constants were measured in the range of 1.4-1.6 x 10(6) M(-1) for the mixed ligand complexes. Furthermore, the complex [Ru(bpy)2(DAP)]2+ was found to photocleave plasmid DNA upon irradiation with visible light.     

Synthesis, structure, and reactivity of rhodium and iridium complexes of the chelating bis-sulfoxide tBuSOC2H4SOtBu. Selective O-H activation of 2-hydroxy-isopropyl-pyridine

The chloro-bridged rhodium and iridium complexes [M2(BTSE)2Cl2] (M = Rh 1, Ir 2) bearing the chelating bis-sulfoxide tBuSOC2H4SOtBu (BTSE) were prepared by the reaction of [M2(COE)4Cl2] (M = Rh, Ir; COE = cyclooctene) with an excess of a racemic mixture of the ligand. The cationic compounds [M(BTSE)2][PF6] (M = Rh 3, Ir 4), bearing one S- and one O-bonded sulfoxide, were also obtained in good yields. The chloro-bridges in 2 can be cleaved with 2-methyl-6-pyridinemethanol and 2-aminomethyl pyridine, resulting in the iridium(I) complexes [Ir(BTSE)(Py)(Cl)] (Py = 2-methyl-6-pyridinemethanol 5, 2-aminomethyl-pyridine 6). In case of the bulky 2-hydroxy- isopropyl-pyridine, selective OH oxidative addition took place, forming the Ir(III)-hydride [Ir(BTSE)(2-isopropoxy-pyridine)(H)(Cl)] 7, with no competition from the six properly oriented C-H bonds. The cationic rhodium(I) and iridium(I) compounds [M(BTSE)(2-aminomethyl-pyridine)][X] (M = Rh 8, Ir 10), [Rh(BTSE)(2-hydroxy- isopropyl-pyridine)][X] 9(stabilized by intramolecular hydrogen bonding), [Ir(BTSE)(pyridine)2][PF6] 12, [Ir(BTSE)(alpha-picoline)2][PF6] 13, and [Rh(BTSE)(1,10-phenanthroline)][PF6] 14 were prepared either by chloride abstraction from the dimeric precursors or by replacement of the labile oxygen bonded sulfoxide in 3 or 4. Complex 14 exhibits a dimeric structure in the solid state by pi-pi stacking of the phenanthroline ligands.