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 iridium(III) complexes with substituted 1,10-phenanthrolines: a new class of highly active organometallic second order NLO-phores with excellent transparency with respect to second harmonic emission

[Ir(ppy)(2)(5-R-1,10-phen)][PF(6)] (ppy = cyclometallated 2-phenylpyridine, phen = phenanthroline, R = H, Me, NMe(2), NO(2)) and [Ir(ppy)(2)(4-R',7-R'-1,10-phen)][PF(6)] (R' = Me, Ph) complexes are characterized by one of the highest second order NLO response (measured by the EFISH technique) reported for a metal complex, mainly due (as suggested by a theoretical SOS-TDDFT investigation) to MLCT processes from the ppy-Ir based moiety acting as donor push system to pi* orbitals of phen, acting as an acceptor pull system; the good transparency to the second harmonic emission renders these NLO-phores appealing as building blocks for molecular materials with second harmonic generation.     

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.     

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.     

Long-lived palladium catalysts for CO/vinyl arene polyketones synthesis: a solution to deactivation problems

A series of cationic palladium complexes of general formula [Pd(Me)(MeCN)(N-N)][PF(6)] (N-N = (phen) 1 a, 4,7-dichloro-1,10-phenanthroline (4,7-Cl(2)-phen) 2 a, 4,7-diphenyl-1,10-phenanthroline (4,7-Ph(2)-phen) 3 a, 4-methyl-1,10-phenanthroline (4-Me-phen) 4 a, 4,7-dimethyl-1,10-phenanthroline (4,7-Me(2)-phen) 5 a, 5,5,6,6-tetrafluoro-5,6-dihydro-1,10-phenanthroline (F(4)-phen) 6 a, containing different substituted phenanthroline ligands, have been prepared from the corresponding neutral chloro derivatives [Pd(Me)(Cl)(N-N)], (1 b-6 b). The X-ray crystal structure of [Pd(Cl)(2)(4,7-Cl(2)-phen)] (2 b') was determined. DFT calculations show that the electron density on the metal is tuned by the substituents on the ligands. The catalytic behavior of complexes 1 a-6 a in the CO/styrene and CO/p-Me-styrene copolymerizations was studied in detail, showing that the generated catalysts are active for at least 90 h, yielding copolymers of high molecular weight. A firm correlation between the electron density on palladium on the one hand and the catalytic activity of the complexes and the molecular weight and the stereochemistry of the polyketones synthesized on the other hand has been established: the catalyst containing the F(4)-phen is thus far the most active among those tested, yielding the syndiotactic CO/styrene copolymer with a stereoregularity of 96 % (uu triad) and with an M(w) value of 1 000 000.     

Luminescent iridium complexes for detection of molybdate

Reactions of [Ir(C^N)(2)Cl](2) [HC^N = 2-(3-R-phenyl)pyridine, 2-(3-R-phenylpyrazole) R = H, Me] with Me(2)-phencat give luminescent complexes [Ir(C^N)(2)(Me(2)-phencat)][PF(6)] (Me(2)-2a, b, c)[PF(6)]. Deprotection of the methoxy groups with BBr(3) is problematic as simultaneous bromination of the cyclometallated phenyl groups occurs. However, deprotection of Me(2)-phencat with BBr(3) followed by complexation with [Ir(C^N)(2)Cl](2) gives luminescent complexes [Ir(C^N)(2)(H(2)-phencat)][PF(6)] (H(2)-3a, c)[PF(6)], which are luminescent sensors for molybdate.     

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.     

Dimethylsulfoxide as a ligand for RhI and IrI complexes--isolation, structure, and reactivity towards X-H bonds (X=H, OH, OCH3)

Novel neutral and cationic Rh(I) and Ir(I) complexes that contain only DMSO molecules as dative ligands with S-, O-, and bridging S,O-binding modes were isolated and characterized. The neutral derivatives [RhCl(DMSO)(3)] (1) and [IrCl(DMSO)(3)] (2) were synthesized from the dimeric precursors [M(2)Cl(2)(coe)(4)] (M=Rh, Ir; COE=cyclooctene). The dimeric Ir(I) compound [Ir(2)Cl(2)(DMSO)(4)] (3) was obtained from 2. The first example of a square-planar complex with a bidentate S,O-bridging DMSO ligand, [(coe)(DMSO)Rh(micro-Cl)(micro-DMSO)RhCl(DMSO)] (4), was obtained by treating [Rh(2)Cl(2)(coe)(4)] with three equivalents of DMSO. The mixed DMSO-olefin complex [IrCl(cod)(DMSO)] (5, COD=cyclooctadiene) was generated from [Ir(2)Cl(2)(cod)(2)]. Substitution reactions of these neutral systems afforded the complexes [RhCl(py)(DMSO)(2)] (6), [IrCl(py)(DMSO)(2)] (7), [IrCl(iPr(3)P)(DMSO)(2)] (8), [RhCl(dmbpy)(DMSO)] (9, dmbpy=4,4'-dimethyl-2,2'-bipyridine), and [IrCl(dmbpy)(DMSO)] (10). The cationic O-bound complex [Rh(cod)(DMSO)(2)]BF(4) (11) was synthesized from [Rh(cod)(2)]BF(4). Treatment of the cationic complexes [M(coe)(2)(O=CMe(2))(2)]PF(6) (M=Rh, Ir) with DMSO gave the mixed S- and O-bound DMSO complexes [M(DMSO)(2)(DMSO)(2)]PF(6) (Rh=12; Ir=in situ characterization). Substitution of the O-bound DMSO ligands with dmbpy or pyridine resulted in the isolation of [Rh(dmbpy)(DMSO)(2)]PF(6) (13) and [Ir(py)(2)(DMSO)(2)]PF(6) (14). Oxidative addition of hydrogen to [IrCl(DMSO)(3)] (2) gave the kinetic product fac-[Ir(H)(2)Cl(DMSO)(3)] (15) which was then easily converted to the more thermodynamically stable product mer-[Ir(H)(2)Cl(DMSO)(3)] (16). Oxidative addition of water to both neutral and cationic Ir(I) DMSO complexes gave the corresponding hydrido-hydroxo addition products syn-[(DMSO)(2)HIr(micro-OH)(2)(micro-Cl)IrH(DMSO)(2)][IrCl(2)(DMSO)(2)] (17) and anti-[(DMSO)(2)(DMSO)HIr(micro-OH)(2)IrH(DMSO)(2)(DMSO)][PF(6)](2) (18). The cationic [Ir(DMSO)(2)(DMSO)(2)]PF(6) complex (formed in situ from [Ir(coe)(2)(O=CMe(2))(2)]PF(6)) also reacts with methanol to give the hydrido-alkoxo complex syn-[(DMSO)(2)HIr(micro-OCH(3))(3)IrH(DMSO)(2)]PF(6) (19). Complexes 1, 2, 4, 5, 11, 12, 14, 17, 18, and 19 were characterized by crystallography.     

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.     

A series of dinuclear homo- and heterometallic complexes with two or three bridging sulfido ligands derived from the tungsten tris(sulfido) complex [Et(4)N][(Me(2)Tp)WS(3)] (Me(2)Tp = hydridotris(3,5-dimethylpyrazol-1-yl)borate)

The generation of heterobimetallic complexes with two or three bridging sulfido ligands from mononuclear tris(sulfido) complex of tungsten [Et(4)N][(Me(2)Tp)WS(3)] (1; Me(2)Tp = hydridotris(3,5-dimethylpyrazol-1-yl)borate) and organometallic precursors is reported. Treatment of 1 with stoichiometric amounts of metal complexes such as [M(PPh(3))(4)] (M = Pt, Pd), [(PtMe(3))(4)(micro(3)-I)(4)], [M(cod)(PPh(3))(2)][PF(6)] (M = Ir, Rh; cod = 1,5-cyclooctadiene), [Rh(cod)(dppe)][PF(6)] (dppe = Ph(2)PCH(2)CH(2)PPh(2)), [CpIr(MeCN)(3)][PF(6)](2) (Cp = eta(5)-C(5)Me(5)), [CpRu(MeCN)(3)][PF(6)], and [M(CO)(3)(MeCN)(3)] (M = Mo, W) in MeCN or MeCN-THF at room temperature afforded either the doubly bridged complexes [Et(4)N][(Me(2)Tp)W(=S)(micro-S)(2)M(PPh(3))] (M = Pt (3), Pd (4)), [(Me(2)Tp)W(=S)(micro-S)(2)M(cod)] (M = Ir, Rh (7)), [(Me(2)Tp)W(=S)(micro-S)(2)Rh(dppe)], [(Me(2)Tp)W(=S)(micro-S)(2)RuCp] (10), and [Et(4)N][(Me(2)Tp)W(=S)(micro-S)(2)W(CO)(3)] (12) or the triply bridged complexes including [(Me(2)Tp)W(micro-S)(3)PtMe(3)] (5), [(Me(2)Tp)W(micro-S)(3)IrCp][PF(6)] (9), and [Et(4)N][(Me(2)Tp)W(micro-S)(3)Mo(CO)(3)] (11), depending on the nature of the incorporated metal fragment. The X-ray analyses have been undertaken to clarify the detailed structures of 3-5, 7, and 9-12.     

Structural Diversity and Thermochromic Properties of Iodobismuthate Materials Containing d-Metal Coordination Cations: Observation of a High Symmetry [Bi(3)I(11)](2-) Anion and of Isolated I(-) Anions

Six new inorganic-organic salts, all containing iodobismuthate anions and d-metal coordination cations, were synthesized solvothermally from reactions of bismuth iodide, a transition metal (M) nitrate salt (M = Co, Fe or Zn), and a heterocyclic, chelating organic ligand: 1,10-phenanthroline (1,10-phen), 3,4,7,8-tetramethyl-1,10-phenanthroline (TMphen), or 2,2':6',2'-terpyridine (tpy). All six compounds were structurally analyzed by single crystal X-ray diffraction, including variable temperature crystallographic analysis to monitor for structural changes. Furthermore, those containing novel anions and achieved in high yield were additionally characterized by solid-state UV visible spectroscopy at room temperature. [Co(1,10-phen)(3)][Bi(3)I(11)] (1), [Fe(1,10-phen)(3)][Bi(3)I(11)] (2), and [Zn(1,10-phen)(3)][Bi(3)I(11)] (3) are isostructural. They crystallize in the monoclinic space group P2(1)/n and contain the unprecedented iodobismuthate anion, [Bi(3)I(11)](2-), which exhibits near D(3h) symmetry and has an unusual arrangement of three cis face-sharing BiI(6) octahedra. [Co(TMPhen)(3)](2)[Bi(2)I(9)][I] (4), which crystallizes in the trigonal space group P-31c, and [Co(tpy)(2)](2)[Bi(2)I(9)][I] (5) and [Zn(tpy)(2)](2)[Bi(2)I(9)][I] (6), which are isostructural and crystallize in the monoclinic space group C2/c, contain the discrete binuclear [Bi(2)I(9)](3-) anion, common in previously reported iodobismuthate compounds. In addition they contain unusual isolated I(-) anions, which are rarely encountered in iodobismuthate phases. Compounds 1-6 show constitutional similarities while utilizing different organic ligands and illustrate the sensitive dependence of reaction conditions on the identity of the halometalate anion formed. Additionally, all six compounds and the starting material BiI(3) are thermochromic; the origin of this behavior is spectroscopically and crystallographically investigated.     

Scrutinizing low-spin Cr(II) complexes

The oxidation state of the chromium center in the following compounds has been probed using a combination of chromium K-edge X-ray absorption spectroscopy and density functional theory: [Cr(phen)(3)][PF(6)](2) (1), [Cr(phen)(3)][PF(6)](3) (2), [CrCl(2)((t)bpy)(2)] (3), [CrCl(2)(bpy)(2)]Cl(0.38)[PF(6)](0.62) (4), [Cr(TPP)(py)(2)] (5), [Cr((t)BuNC)(6)][PF(6)](2) (6), [CrCl(2)(dmpe)(2)] (7), and [Cr(Cp)(2)] (8), where phen is 1,10-phenanthroline, (t)bpy is 4,4'-di-tert-butyl-2,2'-bipyridine, and TPP(2-) is doubly deprotonated 5,10,15,20-tetraphenylporphyrin. The X-ray crystal structures of complexes 1, [Cr(phen)(3)][OTf](2) (1'), and 3 are reported. The X-ray absorption and computational data reveal that complexes 1-5 all contain a central Cr(III) ion (S(Cr) = (3)/(2)), whereas complexes 6-8 contain a central low-spin (S = 1) Cr(II) ion. Therefore, the electronic structures of 1-8 are best described as [Cr(III)(phen(?))(phen(0))(2)][PF(6)](2), [Cr(III)(phen(0))(3)][PF(6)](3), [Cr(III)Cl(2)((t)bpy(?))((t)bpy(0))], [Cr(III)Cl(2)(bpy(0))(2)]Cl(0.38)[PF(6)](0.62), [Cr(III)(TPP(3?-))(py)(2)], [Cr(II)((t)BuNC)(6)][PF(6)](2), [Cr(II)Cl(2)(dmpe)(2)], and [Cr(II)(Cp)(2)], respectively, where (L(0)) and (L(?))(-) (L = phen, (t)bpy, or bpy) are the diamagnetic neutral and one-electron-reduced radical monoanionic forms of L, and TPP(3?-) is the one-electron-reduced doublet form of diamagnetic TPP(2-). Following our previous results that have shown [Cr((t)bpy)(3)](2+) and [Cr(tpy)(2)](2+) (tpy = 2,2':6',2"-terpyridine) to contain a central Cr(III) ion, the current results further refine the scope of compounds that may be described as low-spin Cr(II) and reveal that this is a very rare oxidation state accessible only with ligands in the strong-field extreme of the spectrochemical series.     

The intramolecular aryl embrace: from light emission to light absorption

6-(1-Methylpyrrol-2-yl)-2,2'-bipyridine, 3, and 6-(selenophene-2-yl)-2,2'-bipyridine, 4, have been prepared and characterized in solution and by structural determinations. Copper(I) complexes [CuL(2)][PF(6)] in which L is 2,2'-bipyridine substituted in the 6-position by furyl, thienyl, N-methylpyrrolyl, selenopheneyl, methyl or phenyl, (L = 1-6) have been synthesized. The complexes have been characterized by electrospray mass spectrometry, and solution NMR and UV-VIS spectroscopies. The single crystal structures of [Cu(1)(2)][PF(6)], [Cu(2)(2)][PF(6)], [Cu(3)(2)][PF(6)], [Cu(5)(2)][PF(6)] and [Cu(6)(2)][PF(6)] have been determined. In those compounds containing an aromatic substituent attached to the bpy unit, the substituent is twisted with respect to the latter. In [Cu(3)(2)][PF(6)] and [Cu(5)(2)][PF(6)], this results in intra-cation π-stacking between ligands which is very efficient in [Cu(3)(2)](+) despite the steric requirements of the N-methyl substituents. Face-to-face stacking between the ligands in the [Cu(2)(2)](+) ion is achieved by complementary substituent twisting and elongation of one Cu-N bond, but there is no analogous intra-cation π-stacking in [Cu(1)(2)](+). Ligand exchange reactions between [CuL(2)][PF(6)] (L = 1-6) and TiO(2)-anchored ligands 7-10 (L' = 2,2'-bipyridine-based ligands with CO(2)H or PO(OH)(2) anchoring groups) have been applied to produce 24 surface-anchored heteroleptic copper(i) complexes, the formation of which has been evidenced by using MALDI-TOF mass spectrometry and thin layer solid state diffuse reflectance electronic absorption spectroscopy. The efficiencies of the complexes as dyes in DSCs have been measured, and the best efficiencies are observed for [CuLL'] with L' = 10 which contains phosphonate anchoring groups.     

1,12-Diazaperylene and 2,11-dialkylated-1,12-diazaperylene iridium(iii) complexes [Ir(C^N)(2)(N^N)]PF(6): new supramolecular assemblies

A series of new monocationic iridium(iii) complexes [Ir(C^N)(2)(N^N)]PF(6) with "large-surface"α,α'-diimin ligands N^N (dap = 1,12-diazaperylene, dmedap = 2,11-dimethyl-1,12-diazaperylene, dipdap = 2,11-diisopropyl-1,12-diazaperylene) and different cyclometalating ligands C^N (piq = 1-phenylisoquinoline, bzq = benzo[h]quinoline, ppz = 1-phenylpyrazole, thpy = 2-(2-thienyl)pyridine, ppy = 2-phenylpyridine, meppy = 2-(4-methylphenyl)pyridine, dfppy = 2-(2,4-difluorophenyl)pyridine) were synthesized. The solid structures of the complexes [Ir(piq)(2)(dap)]PF(6), [Ir(bzq)(2)(dap)]PF(6), [Ir(ppy)(2)(dipdap)]PF(6), [Ir(piq)(2)(dmedap)]PF(6), [Ir(ppy)(2)(dap)]PF(6) and [Ir(ppz)(2)(dap)]PF(6) are reported. In [Ir(piq)(2)(dap)]PF(6), the dap ligand and one of the piq ligands of each cationic complex are involved in π-π stacking interactions forming supramolecular channels running along the crystallographic c axis. In the crystalline [Ir(bzq)(2)(dap)]PF(6)π-π stacking interactions between the metal complexes lead to the formation of a 2D layer structure. In addition, CH-π interactions were found in all compounds, which are what stabilizes the solid structure. In particular, a significant number of them were found in [Ir(piq)(2)(dap)]PF(6) and [Ir(bzq)(2)(dap)]PF(6). The crystal structures of [Ir(ppy)(2)(dipdap)]PF(6) and [Ir(ppy)(2)(dmedap)]PF(6) are also presented, being the first examples of bis-cyclometalated iridium(iii) complexes with phenanthroline-type α,α'-diimin ligands bearing bulky alkyl groups in the neighbourhood of the N-donor atoms. These ligands implicate a distorted octahedral coordination geometry that in turn destabilized the Ir-N(N^N) bonds. The new iridium(iii) complexes are not luminescent. All compounds show an electrochemically irreversible anodic peak between 1.15 and 1.58 V, which is influenced by the different cyclometalated ligands. All of the new complexes show two reversible successive one-electron "large-surface" ligand-centred reductions around -0.70 V and -1.30 V. Electrospray ionisation mass spectrometry (ESI-MS) and collision induced decomposition (CID) measurements were used to investigate the stability of the new complexes. Thereby, the stability agreed well with the order of the Ir-N(N^N) bond lengths.     

Ruthenium(III) triazacyclononane dithiocarbamate,pyridinecarboxylate, or aminocarboxylate complexes as scavengers of nitric oxide

The preparation of a series of [Ru(III)(tacn)(eta(2)-dtc)(eta(1)-dtc)][PF(6)] (tacn = 1,4,7-triazacyclononane; dtc = dimethyldithiocarbamate, diethyldithiocarbamate, pyrrolidinedithiocarbamate, l-prolinedithiocarbamate, l-prolinemethyl ester dithiocarbamate, l-N-methylisoleucinedithiocarbamate) complexes, 5-11, is described. Complex 5 reacts with NO to form the ruthenium nitrosyl complex 12. A series of [Ru(III)(tacn)(pyc)Cl][PF(6)] (pyc = 2-pyridinecarboxylic acid, 2,4- and 2,6-pyridinecarboxylic acid) complexes, 14-16, were prepared along with [Ru(III)(tacn)(mida)][PF(6)] (mida = N-methyliminodiacetic acid), 13, and [Ru(III)(Hnota)Cl], 17, (Hnota = 1-acetic acid-4,7-bismethylcarboxylate-1,4,7-triazacyclononane). Complexes 5-17 were evaluated for use as NO scavengers in an in vitro assay using RAW264 murine macrophage cells. [Ru(III)(tacn)(eta(2)-dtc)(eta(1)-dtc)][PF(6)] complexes 5-11 are very efficient NO scavengers in this assay.     

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.     

Complexes of a hexa-nitrile dianion with neutral, chelating co-ligands: self-assembly, structure and magnetism

Several new first-row transition-metal complexes have been synthesised by combining the polynitrile dianion HCTMCP(2-) (hexacyanotrimethylenecyclopropandiide) with neutral, chelating co-ligands; 2,2'-bipyridine, 1,10-phenanthroline and 3-(2-pyridyl)pyrazole. The products cover a remarkable range of species including mononuclear complexes, dimers, charge-separated species and coordination polymers. Complexes containing 2,2'-bipyridine take the form [Mn(2,2'-bipy)(2)(HCTMCP)](2)·2MeOH (1) or [M(2,2'-bipy)(3)](HCTMCP) (2Fe and 2Co) which are dimeric and charge-separated products, respectively. The products obtained using 1,10-phenanthroline were the discrete complex [Co(HCTMCP)(1,10-phen)(2)(H(2)O)]·H(2)O·MeCN (3) and the 1D coordination polymer [Mn(HCTMCP)(1,10-phen)(H(2)O)(MeOH)] (4). Complexes using the 3-(2-pyridyl)pyrazole co-ligand (pypzH) form similar 1D complexes to 4, namely [Mn(pypzH)(HCTMCP)(MeOH)(H(2)O)] (5) and [M(pypzH)(HCTMCP)(MeOH)(2)] (6Co and 6Fe), albeit with different hydrogen-bonding motifs between the chains. The polymeric HCTMCP complexes show weak to zero antiferromagnetic coupling between metal centres and thus no long-range ordering.     

Efficient yellow electroluminescence from a single layer of a cyclometalated iridium complex

We report on the spectroscopic, electrochemical, and electroluminescent properties of [Ir(ppy)(2)(dtb-bpy)](+)(PF(6))(-) (ppy: 2-phenylpyridine, dtb-bpy: 4,4'-di-tert-butyl-2,2'-dipyridyl). Single-layer devices were fabricated and found to emit yellow light with a brightness that exceeds 300 cd/m(2) and a luminous power efficiency that exceeds 10 Lm/W at just 3 V. The PF(6)(-) space charge was found to dominate the device characteristics.     

Tuning emission wavelength and redox properties through position of the substituent in iridium(III) cyclometallated complexes

Cyclometallated phenyls with substituents para to the metal have a larger impact on the redox potentials and emission of complexes [Ir(R-ppz)(2)(bipy)][PF(6)] than substituents at the meta position and hence enable tuning of emission wavelength over a wider range using the same substituent.     

Bi- and poly-metallic cyanide-bridged complexes of the redox-active cyanomanganese nitrosyl unit [Mn(CN)(PR3)(NO)(eta-C5H4Me)

Cationic nitrile complexes and neutral halide and cyanide complexes, with the general formula [MnL1L2(NO)(eta-C5H4Me)]z, undergo one-electron oxidation at a Pt electrode in CH2Cl2. Linear plots of oxidation potential, Eo', vs. nu(NO) or the Lever parameters, EL, for L1 and L2, allow Eo' to be estimated for unknown analogues. In the presence of TlPF6, [MnIL'(NO)(eta-C5H4Me)] reacts with [Mn(CN)L(NO)(eta-C5H4Me)] to give [(eta5-C5H4Me)(ON)LMn(mu-CN)MnL'(NO)(eta5-C5H4Me)][PF6] which undergoes two reversible one-electron oxidations; DeltaE, the difference between the potentials for the two processes, differs significantly for stable cyanide-bridged linkage isomers. Novel pentametallic complexes such as [Mn[(mu-NC)Mn(CNBut)(NO)(eta5-C5H4Me)]4(OEt2)][PF6]2 and [Mn[(mu-NC)Mn(CNXyl)(NO)(eta5-C5H4Me)]4(NO3-O,O')][PF6], containing a trigonal bipyramidal and a distorted octahedral Mn(II) centre, respectively, result either from slow decomposition of the binuclear cyanide-bridged species or from the reaction of anhydrous MnI2 with four equivalents of [Mn(CN)L(NO)(eta5-C5H4Me)] in the presence of TlPF6.