Solution, structural and photophysical aspects of substituent effects in the N^N ligand in [Ir(C^N)2(N^N)]+ complexes

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Solution, structural and photophysical aspects of

substituent eﬀects in the N^N ligand in

[Ir(C^N)₂(N^N)]⁺complexes†

Cite this: Dalton Trans., 2013, 42, 8086

Edwin C. Constable,^aCatherine E. Housecroft,*^aPeter Kopecky,^aColin J. Martin,^a

Iain A. Wright,^aJennifer A. Zampese,^aHenk J. Bolink^band Antonio Pertegas^b

The syntheses and properties of a series of eleven new [Ir(ppy)₂(N^N)][PF₆] complexes (Hppy = 2-phenyl-

pyridine) are reported. The N^N ligands are based on 2,2-bipyridine (bpy), substituted in the 6- or 5-posi-

tions with groups that are structurally and electronically diverse. All but two of the N^N ligands

incorporate an aromatic ring, designed to facilitate intra-cation face-to-face π-interactions between the

N^N and one [ppy]⁻ligand. Within the set of ligands, 6-(3-tolyl)-2,2’-bipyridine (5), 4,6-bis(4-nitro-

phenyl)-2,2’-bipyridine (9), and 4,6-bis(3,4,5-trimethoxyphenyl)-2,2’-bipyridine (10) are new and their

characterization includes single crystal structures of 9, and two polymorphs of 10. A representative

[Ir(ppy)₂(N^O)]⁺complex is also described. We report solution NMR spectroscopic, photophysical and

electrochemical properties of the complexes, as well as representative solid-state structural data. The solu-

tion ¹H NMR spectroscopic data illustrate diﬀerent dynamic processes involving the substituents attached

Received 22nd February 2013,

Accepted 1st April 2013

to the bpy domain in the ligands. In degassed MeCN and at room temperature, the [Ir(ppy)₂(N^N)][PF₆]

em

max

complexes are orange emitters with λ

in the range 575 to 608 nm; however, quantum yields are very

DOI: 10.1039/c3dt50492a

low. The most promising complexes were evaluated in light-emitting electrochemical cells leading to

www.rsc.org/dalton

bright and stable devices with rather good external quantum eﬃciencies.

on the photophysical properties of the complex¹¹and improves

LEC device lifetimes.^12–17

Introduction

Solid-state light-emitting electrochemical cells (LECs) which

In this paper, we describe the preparation and properties of

incorporate octahedral iridium(^III) complexes [Ir(C^N)₂(N^N)]⁺a series of eleven new [Ir(ppy)₂(N^N)]⁺complexes (Hppy =

(C^N = a cyclometallated ligand, and N^N = 2,2′-bipyridine 2-phenylpyridine) in which the N^N ligands 1–11 (Scheme 1)

(bpy), 1,10-phenanthroline or related chelating ligand) in the have been selected to encompass a range of electron-withdraw-

emissive layer¹are currently the focus of considerable ing and electron-releasing substituents.

A representative

attention.^2–5Manipulation of the electronic properties of the [Ir(ppy)₂(N^O)]⁺complex (N^O = 12, Scheme 1) is also

ligands by judicious choice of functionalities can lead to described. We report their solution NMR spectroscopic, photo-

enhanced emission and tuning of the emission energy.^6–9An physical and electrochemical properties as well as representa-

interplay of experimental and computational results is proving tive solid-state structural data.

to be an important approach to the development of

[Ir(C^N)₂(N^N)]⁺emitters.¹⁰Incorporation of a pendant phenyl

ring adjacent to one N-donor of the N^N ligand results in

intra-cation face-to-face π-stacking with one of the coordinated

Experimental

C^N ligands, and this structural feature has a strong influence

General

Bruker Avance III-500 or Avance III-600 NMR spectrometers

1

were used to record H and ¹³C NMR spectra; chemical shifts

were referenced to residual solvent peaks with respect to

δ(TMS) = 0 ppm. Solution electronic absorption and emission

spectra were recorded on an Agilent 8453 spectrophotometer

and Shimadzu RF-5301 PC spectrofluorometer, respectively,

and FT-IR spectra on a Shimadzu 8400S instrument with

Golden Gate accessory for solid samples. Quantum yields were

^aDepartment of Chemistry, University of Basel, Spitalstrasse 51, CH-4056 Basel,

Switzerland. E-mail: catherine.housecroft@unibas.ch

^bInstituto de Ciencia Molecular, Universidad de Valencia, C/Catedrático J. Beltrán 2,

ES-46980 Paterna (Valencia), Spain

†CCDC 910293, 910295, 910297, 925640–925643. For crystallographic data in

CIF or other electronic format see DOI: 10.1039/c3dt50492a

8086 | Dalton Trans., 2013, 42, 8086–8103

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bipyridine.²¹[Ir(ppy)₂(μ-Cl)]₂was prepared by the reported

method.^22,23

Device preparation

The solvents were supplied by Aldrich. The thickness of films

was determined with an Ambios XP-1 profilometer. ITO-coated

glass plates (15 Ω ⁻¹) were patterned by conventional photo-

□

lithography (http://www.naranjosubstrates.com) and substrates

were cleaned by sonication in water-soap, water, and 2-propa-

nol baths, in that order. After drying, the substrates were

placed in a UV-ozone cleaner (Jelight 42-220) for 20 min.

To prepare the electroluminescence devices, a 90 nm layer

of PEDOT:PSS (CLEVIOS™ P VP AI 4083, aqueous dispersion,

1.3–1.7% solid content, Heraeus) was first spin-coated onto

the ITO glass substrate to improve device reproducibility and

to prevent the formation of pinholes. Transparent films

(90 nm thick) of the complexes [Ir(ppy)₂(N^N)][PF₆] with N^N

= 1, 2, 3, 8 and 10 and the ionic liquid 1-butyl-3-methylimid-

azolium hexafluoridophosphate ([BMIM][PF₆], >98.5%, Sigma-

Aldrich) in a 4 to 1 molar ratio were spin-coated from 20 mg

cm⁻³MeCN solution at 1000 rpm for 20 s. The devices were

transferred in an inert atmosphere glovebox (<0.1 ppm O₂and

H₂O, MBraun) and were annealed at 100 °C for 1 h. The Al

electrode (70 nm) was thermally evaporated using a shadow

mask under a vacuum (<1 × 10⁻⁶mbar) with an Edwards

Auto500 evaporator integrated in the glovebox. The area of the

device was 6.534 mm². The devices were not encapsulated and

were characterized inside the glovebox at room temperature.

LEC characterization

An Avantes luminance spectrometer was used to measure the

electroluminescence (EL) spectrum. Device lifetimes were

measured by applying a pulsed current/DC constant voltage

and monitoring voltage/current and luminance by a True

Colour Sensor MAZeT (MTCSiCT Sensor) with a Botest OLT

OLED Lifetime-Test System (for pulsed current mode) and

Keithley 2400 source meter and a photodiode coupled to a

Keithley 6485 picometer using a Minolta LS100 to calibrate the

photocurrent (for constant voltage mode).

Scheme 1 Structures of ligands 1–12 and numbering schemes for NMR

spectroscopic assignments.

measured with an absolute PL quantum yield spectrometer

C11347 Quantaurus_QY from Hamamatsu. Thin film photo-

luminescence spectra and quantum yields were measured with

a Hamamatsu C9920-02 Absolute PL Quantum Yield Measure-

ment System (λ_exc= 314 nm). The system is made up of an exci-

tation light source, consisting of a xenon lamp linked to a

monochromator, an integration sphere, and a multi-channel

spectrometer. Electrospray ionization (ESI) mass spectra were

recorded on a Bruker esquire 3000^plusinstrument. Electro-

chemical measurements were taken on a CH Instruments 900B

potentiostat and performed using glassy carbon, platinum

wire and silver wire as the working, counter, and reference

electrodes, respectively. Substrates were dissolved in HPLC

grade MeCN (ca. 10⁻⁴mol dm⁻³) containing 0.1 mol dm⁻³

[ⁿBu₄N][PF₆] as the supporting electrolyte; all solutions were

degassed with argon. Cp₂Fe was used as internal reference.

Ligands 1–4,¹⁸11¹⁹and 12²⁰were prepared as previously

described. Compound 6 was synthesized by butylation of 2,2′-

Compound 5. Fresh KO^tBu (2.24 g, 20.0 mmol) was dis-

solved in dry THF (40 ml) at room temperature and 3-methyl-

acetophenone (1.34 g, 10.0 mmol) was added. The solution

turned yellow and over a period of 30 min, a precipitate

formed. A solution of (E)-3-dimethylamino-1-(pyridin-2-yl)-

prop-2-en-1-one (1.76 g, 10.0 mmol) in THF (5 ml) was added

and the suspension turned red immediately. The mixture was

stirred for 30 min and was then left to stand overnight

(ca. 10 h) at room temperature. Then, a solution of NH₄OAc (10 g)

in AcOH (20 ml) was added and the dark solution was stirred

for 2 h at reflux. Solvents were reduced on a rotary evaporator

and the black residue was suspended in H₂O. Solid K₂CO₃was

added until CO₂evolution stopped. The aqueous phase was

extracted several times into CH₂Cl₂, the combined organic

phases were dried over MgSO₄and the solvent was evaporated.

The product was purified by column chromatography

(SiO₂, pentane–Et₂O 9 : 1 changing to 2 : 3). Compound 5 was

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collected as the first major fraction and was isolated as an oﬀ- adjusted to ∼8. The aqueous phase was extracted into CH₂Cl₂

white powder (1.10 g, 4.5 mmol, 45%). ¹H NMR (500 MHz, (∼3 × 30 ml) and the combined organic layers were washed

CDCl₃) δ/ppm 8.68 (ddd, J = 4.7, 1.9, 0.9 Hz, 1H, H^E6), 8.62 (dt, with aqueous NaOH (1 M) and H₂O, and dried over MgSO₄.

J = 7.8, 1.1 Hz, 1H, H^E3), 8.34 (dd, J = 7.8, 1.0 Hz, 1H, H^F3), 7.95 The solid was separated by filtration and the filtrate was evap-

(m, 1H, H^G2), 7.91 (dm, J = 7.8 Hz 1H, H^G6), 7.87 (t, J = 7.8 Hz, orated to give a brown residue. The crude product was purified

1H, H^F4), 7.83 (dt, J = 7.8, 1.8 Hz, 1H, H^E4), 7.75 (dd, J = 7.8, using column chromatography (SiO₂, pentane–Et₂O 2 : 1–1 : 4,

1.8 Hz, 1H, H^F5), 7.38 (t, J = 7.6 Hz, 1H, H^G5), 7.31 (ddd, J = 7.4, then CH₂Cl₂–MeOH 1 : 0–96 : 4). Compound 9 was obtained as

4.8, 1.2 Hz, 1H, H^E5), 7.24 (dm, J = 7.7 Hz, 1H, H^G4) 2.46 (s, the first major fraction from the chromatography column and

1

3H, H^Me). ¹³C NMR (126 MHz, CDCl₃) δ/ppm 156.6 (C^F6), 156.1 was isolated as a yellow solid (702.0 mg, 1.76 mmol, 65%). H

(C^E2), 154.7 (C^F2), 149.1 (C^E6), 139.3 (C^G1), 138.0 (C^G3), 137.6 NMR (500 MHz, DMSO-d₆) δ/ppm 8.76 (ddd, J = 4.7, 1.8,

(C^F4), 137.0 (C^E4), 129.8 (C^G4), 128.7 (C^G5), 127.7 (C^G2), 124.1 0.9 Hz, 1H, H^E6), 8.75 (d, J = 1.6 Hz, 1H, H^F3), 8.66 (m, 2H,

(C^G6), 123.8 (C^E5), 121.4 (C^E3), 120.5 (C^F5), 119.3 (C^F3), 21.6 H^G2), 8.63 (dt, J = 8.0, 1.1 Hz, 1H, H^E3), 8.57 (d, J = 1.6 Hz, 1H,

(C^Me). IR (solid, ν/cm⁻¹) 3051 w, 3018 w, 3012 w, 3002 w, H^F5), 8.38 (m, 4H, H^H3+G3), 8.30 (m, 2H, H^H2), 8.04 (td, J = 7.7,

2955 w, 2919 w, 2857 w, 2360 m, 2321 w, 2313 w, 1700 m, 1.8 Hz, 1H, H^E4), 7.54 (ddd, J = 7.4, 4.8, 1.2 Hz, 1H, H^E5). ¹³C

1653 m, 1607 w, 1580 s, 1560 s, 1555 m, 1506 w, 1490 w, NMR (126 MHz, DMSO-d₆) δ/ppm 155.7 (C^E2/F2), 155.6 (C^E2/F2),

1472 m, 1456 m, 1447 m, 1427 s, 1420 m, 1319 w, 1287 w, 150.7 (C^E6), 149.3 (C^G4+H4), 145.4 (C^G1/H1), 144.7 (C^G1/H1), 139.0

1280 w, 1258 w, 1191 w, 1156 w, 1102 w, 1084 w, 1041 w, (C^E4), 130.2 (C^H2), 129.7 (C^G2), 126.0 (C^E5), 125.5 (C^G3+H3),

990 w, 826 w, 770 s, 745 w, 697 w, 668 m, 643 m, 618 m, 122.4 (C^E3), 121.1 (C^F5), 119.5 (C^F3), (C^F4and C^F6not un-

602 m. UV/VIS (MeCN, degassed) λ_max/nm 236 (ε/dm³mol⁻¹ambiguously assigned). IR (solid, ν/cm⁻¹) 3113 w, 3088 w, 3064 w,

cm⁻¹20 700), 262 (16 500), 284 (12 700), 309sh (10 700); emis- 2947 w, 2850 w, 2451 w, 2361 w, 1593 s, 1581 s, 1567 m, 1548

sion (λ_exc= 260 nm) λ_max= 342 nm. ESI-MS m/z 246.1 [M]⁺s, 1505 s, 1496 s, 1488 s, 1471 m, 1432 m, 1419 m, 1393 m,

(base peak, calc. 246.1). Found C 82.11, H 5.79, N 11.76%; 1384 m, 1342 s, 1286 m, 1264 m, 1248 m, 1223 w, 1150 w, 1125

C₁₇H₁₄N₂requires C 81.90, H 5.73, N 11.37%.

w, 1105 s, 1091 m, 1081 m, 1051 w, 1036 w, 1008 m, 991 m,

Compound 7. The preparation of 7 has been reported,²⁴but 973 w, 958 w, 906 w, 858 s, 848 s, 836 s, 825 s, 811 s, 793 s, 753

an alternative method is as follows. The procedure was as for 5 s, 746 s, 737 s, 711 s, 691 s, 660 s, 640 s, 613 s. UV/VIS

using 2-acetylpyridine (1.21 g, 5.0 mmol) and (E)-1-(pyrid-4-yl)-3- (degassed MeCN) λ_max/nm 223sh (ε /dm³mol⁻¹cm⁻¹17 600),

N,N-dimethylaminoprop-2-en-1-one (1.76 g, 5.0 mmol). Com- 289 (25 200), 331sh (11 800); emission (λ_exc= 286 nm) λ_em

=

pound 7 was collected as the second fraction (627.0 mg, 458 nm; ESI-MS m/z: 398.1 [M]⁺(base peak, calc. 398.1. Found

2.7 mmol, 54%). Spectroscopic data agreed with literature C 65.87, H 3.65, N 14.08; C₂₂H₁₄N₄O₄requires C 66.33, H 3.54,

data.²⁴

N 14.06%.

Compound 8. The synthesis of 8 has previously been

Compound 10. 1-(2-Oxo-2-(pyridin-2-yl)ethyl)pyridin-1-ium

described;²⁵we find the following method convenient. 1-(2- iodide (0.98 g, 3.0 mmol), 1,3-di(3,4,5-trimethoxyphenyl)prop-

Oxo-2-(pyridin-2-yl)ethyl)pyridin-1-ium

iodide

(0.82

g, 2-en-1-one (1.17 g, 3.0 mmol) and NH₄OAc (4.00 g, 51.9 mmol)

2.5 mmol), 1,3-diphenylprop-2-en-1-one (0.52 g, 2.5 mmol) were suspended in EtOH (25 ml) and the mixture was stirred

and NH₄OAc (5.78 g, 75.0 mmol) were suspended in EtOH under reflux for 3 h. The yellow suspension turned black; TLC

(50 ml) and the mixture was stirred under reflux for 3 h during was used to monitor the reaction. The work-up was as for 9.

which time the yellow/orange colour darkened. The reaction Compound 10 was the first fraction and was isolated as a

was monitored by TLC. Solvent was evaporated to give a black yellow solid (814 mg, 1.67 mmol, 56%). ¹H NMR (500 MHz,

residue which was suspended in H₂O and the pH was adjusted CDCl₃) δ (ppm) 8.73 (ddd, J = 4.8, 1.8, 0.9 Hz, 1H, H^E6), 8.63

to ∼8. The aqueous phase was extracted into CH₂Cl₂(3 × (dt, J = 8.0, 1.1 Hz, 1H, H^E3), 8.56 (d, J = 1.6 Hz, 1H, H^F3), 7.88

30 ml) and the combined organic layers were washed with (td, J = 8.0, 1.8 Hz, 1H, H^E4), 7.82 (d, J = 1.6 Hz, 1H, H^F5), 7.40

aqueous NaOH (∼1 M) and water, and dried over MgSO₄. The (s, 2H, H^G2), 7.36 (ddd, J = 7.5, 4.8, 1.2 Hz, 1H, H^E5), 6.97 (s,

solid was removed by filtration and the filtrate was evaporated 2H, H^H2), 4.01 (s, 6H, H^{3,5-OMe ring G}), 3.98 (s, 6H, H^{3,5-OMe ring H}),

ring

to give a brown residue. The crude product was purified by 3.933 (s, 3H, H^4-OMe

^G), 3.927 (s, 3H, H^4-OMe

^H). ¹³C

column chromatography (SiO₂, pentane–Et₂O 2 : 1 changing to NMR (126 MHz, CDCl₃) δ/ppm 157.1 (C^F6), 156.2 (C^E2+F2),

1 : 4), and 8 was collected as the first fraction and isolated as a 153.7 (C^G3/H3), 153.6 (C^G3/H3), 150.6 (C^F4), 149.1 (C^E6), 139.1

yellow solid (290 mg, 0.94 mmol, 38%). The spectroscopic data (C^G4+H4), 136.9 (C^E4), 134.7 (C^G1+H1), 123.8 (C^E5), 121.4 (C^E3),

matched those reported.²⁵UV/VIS (MeCN, degassed) λ_max/nm 118.6 (C^F5), 117.4 (C^F3), 104.6 (C^G2+H2), 60.8 (C^{4-OMe rings G+H}),

255 (ε/dm³mol⁻¹cm⁻¹24 100), 316sh (4900); emission (λ_exc

265 nm) λ_em= 358 nm.

=

56.4 (C^{3,5-OMe ring G/H}), 56.3 (C^{3,5-OMe ring G/H}). IR (solid, ν/cm⁻¹

3000 m, 2939 m, 2843 w, 2825 w, 2362 m, 2333 m, 1700 m,

)

Compound

9. 1-(2-(4-Nitrophenyl)-2-oxoethyl)pyridinium 1653 m, 1583 s, 1545 s, 1505 s, 1456 s, 1398 m, 1383 s, 1326 s,

iodide (0.82 g, 2.5 mmol), (E)-1-(4-nitrophenyl)-3-(pyrid-2-yl)- 1245 s, 1233 s, 1201 m, 1186 m, 1167 m, 1121 s, 1092 s,

prop-2-ene-1-one (0.52 g, 2.5 mmol) and NH₄OAc (6.24 g, 1032 m, 998 s, 962 m, 919 w, 900 w, 888 m, 851 m, 827 s, 799

81.0 mmol) were suspended in EtOH (50 ml) and the mixture s, 761 m, 729 m, 683 s, 668 s, 657 s, 625 m, 618 s. UV/VIS

was stirred under reflux for 3 h. Solvent was removed in vacuo (degassed MeCN) λ_max/nm 283 (ε /dm³mol⁻¹cm⁻¹49 500);

and the black residue was suspended in H₂O and the pH emission (λ_exc= 283 nm) λ_em= 461 nm. ESI-MS m/z 488.2 [M]⁺

8088 | Dalton Trans., 2013, 42, 8086–8103

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(base peak, calc. 488.2). Found C 68.13, H 5.60, N 5.79; Hz, 1H, H^A6/C6), 5.90 (d, J = 7.6 Hz, 1H, H^A6/C6), 5.87 (d, J = 3.4

C₂₈H₂₈N₂O₆requires C 68.84, H 5.78, N 5.73%.

Hz, 1H, H^G4). ¹³C NMR (126 MHz, 295 K, CD₂Cl₂) δ/ppm 168.9

(C^D2), 167.3 (C^B2), 158.0 (C^F2/E2), 157.6 (C^F2/E2), 153.9 (C^F6),

152.1 (C^B6), 150.7 (C^G2+E6), 149.2 (C^A1/C1), 148.2 (C^D6), 146.4

(C^A1/C1), 144.6 (C^G5/G3), 143.7 (C^A2/C2), 143.3 (C^A2/C2), 140.3

[Ir(ppy)₂L][PF₆]: general procedure

Unless otherwise stated, each synthesis was carried out on a (C^F4), 139.9 (C^E4), 138.7 (C^B4/D4), 138.6 (C^B4/D4), 132.9 (C^A6/C6),

50.0 μmol scale with respect to [Ir(ppy)₂(μ-Cl)]₂. In a typical 131.4 (C^A6/C6), 131.0 (C^A5/C5), 130.2 (C^A5/C5), 129.6 (C^F5), 128.2

reaction, [Ir(ppy)₂(μ-Cl)]₂(50.3 mg, 50.0 µmol) was suspended (C^E5), 125.9 (C^E3), 125.4 (C^A3/C3), 124.6 (C^F3), 124.2 (C^A3/C3),

in MeOH and ligand, L, (100.0 µmol) was added. The solution 123.4 (C^B5), 123.3 (C^A4/C4), 122.9 (C^D5), 121.7 (C^A4/C4), 120.2

was heated for 2 h at 120 °C in a microwave reactor. Solvent (C^B3), 119.8 (C^D3), 112.6 (C^G3/G5), 112.1 (C^G4). IR (solid, ν/cm⁻¹

)

was reduced and the product precipitated by addition of solid 3124 w, 3049 w, 2335 w, 1607 m, 1582 m, 1476 m, 1437 m,

NH₄PF₆(130.0 mg, 0.80 mmol). Solvent was removed and the 1420 m, 1317 w, 1270 w, 1226 w, 1164 m, 1125 w, 1065 m,

crude product was purified by column chromatography (short 1031 m, 1014 m, 920 w, 885 w, 831 s, 821 s, 796 m, 754 s, 728

column, SiO₂, CH₂Cl₂changing to CH₂Cl₂–MeOH 98 : 2).

s. ESI-MS m/z: 723.1 [M − PF₆]⁺(base peak calc. 723.1). Found

[Ir(ppy)₂(1)][PF₆]. Reactants were [Ir(ppy)₂(μ-Cl)]₂(205.0 mg, C 49.23, H 3.10, N 6.12; C₃₆H₂₆F₆IrN₄OP·0.5H₂O requires C

191.0 μmol) and 1 (94.5 mg, 402.0 μmol). [Ir(ppy)₂(1)][PF₆] was 49.31, H 3.10, N 6.39%.

1

isolated as an orange powder (320.0 mg, 363.7 μmol, 95%). H

[Ir(ppy)₂(3)][PF₆]. Reactants were 3 (60.0 mg, 250.0 μmol)

NMR (500 MHz, 295 K, CD₂Cl₂) δ/ppm 8.46 (overlapping d, J ≈ and [Ir(ppy)₂(μ-Cl)]₂(139.0 mg, 125.0 μmol) with a reaction

8.0 Hz, 2H, H^F3+E3), 8.18 (t, J = 7.9 Hz, 1H, H^F4), 8.10 (t, J = 7.9 time of 30 min. [Ir(ppy)₂(3)][PF₆] was isolated as an orange

Hz, 1H, H^E4), 7.92 (d, J = 8.2 Hz, 2H, H^B6+E6), 7.85 (m, 2H, powder (224.0 mg, 250.0 μmol, 100%). ¹H NMR (500 MHz,

H^B3+B4), ≈7.8 (v br, H^D3/D6, see text), 7.77 (br t, J = 7.4 Hz, 1H, 295 K, CD₂Cl₂) δ/ppm 8.51 (overlapping d, J ≈ 8.0 Hz, 2H,

H^D4), 7.71 (br, H^D3/D6), 7.56 (d, J = 7.7 Hz, 1H, H^A3/C3), 7.45 (m, H^E3+F3), 8.15 (m, 2H, H^E4+F4), 7.88 (m, 2H, H^B3+D3), 7.85 (d, J =

2H, H^A3/C3+F5), 7.38 (m, 1H, H^E5), 7.08 (m, 1H, H^D5), 7.03 (m, 5.5 Hz, 1H, H^E6), 7.80 (m, 3H, H^B4+D4+B6/D6), 7.58 (m, 2H,

1H, H^B5), 6.96 (t, J = 7.5 Hz, 1H, H^A4/C4), 6.84 (t, J = 7.5 Hz, 1H, H^A3/C3+F5), 7.55 (d, J = 5.9 Hz, 1H, H^B6/D6), 7.38 (m, 2H, H^A3/C3+E5),

H^A5/C5), 6.66 (t, J = 7.8 Hz, 1H, H^A4/C4), 6.56 (t, J = 7.4 Hz, 1H, 7.10 (m, 1H, H^B5/D5), 6.99 (m, 2H, H^B5/D5+A4/C4), 6.90 (dd, J =

H^A5/C5), 6.01 (br d, J ≈ 6 Hz, 1H, H^A6/C6), 5.88 (br, 1H, H^G3/G4), 4.8, 1.3 Hz, 1H, H^G3/G5), 6.81 (t, J = 7.5 Hz, 1H, H^A5/C5), 6.67 (t,

5.82 (d, J = 7.5 Hz, 1H, H^A6/C6), 5.49 (br, 1H, H^G3/G4), 5.07 (v br, J = 7.5 Hz, 1H, H^A4/C4), 6.47 (t, J = 7.5 Hz, 1H, H^A5/C5), 6.31 (t,

H^G5), 3.01 (br, 3H, H^NMe). ¹³C NMR (126 MHz, 295 K, CD₂Cl₂) J = 4.4 Hz, 1H, H^G4), 6.22 (m, 1H, H^G3/G5), 5.96 (d, J = 7.6 Hz,

δ/ppm 169.7 (C^D2/B2), 167.8 (C^D2/B2), 158.0 (C^F6), 157.6 (C^E2/F2), 1H, H^A6/C6), 5.72 (d, J = 7.6 Hz, 1H, H^A6/C6).¹³C NMR (126 MHz,

157.55 (C^E2/F2), 150.8 (C^B6+E6), 150.1 (C^A1/C1), 149.3 (C^A1/C1), 295 K, CD₂Cl₂) δ/ppm 169.3 (C^D2/B2), 167.5 (C^B2/D2), 159.0 (C^E2/F2),

147.4 (C^A2/C2) 143.6 (C^A2/C2), 139.8 (C^E4), 139.6 (C^F4), 138.8 157.6 (C^E2/F2), 157.4 (C^F6), 150.9 (C^A1/C1), 150.8 (C^B6/D6), 150.4

(C^D4), 138.5 (C^B4), 131.5 (C^A6/C6), 131.3 (C^{A3/C3 or F5}), 131.2 (C^A5/C5), (C^E6), 148.9 (C^B6/D6), 146.6 (C^A1/C1), 143.5 (C^A2/C2), 143.2 (C^A2/C2),

130.9 (C^A6/C6), 129.9 (C^A5/C5), 128.2 (C^E5), 125.5 (C^E3/F3), 140.0 (C^E4/F4), 139.9 (C^E4/F4), 138.8 (C^B4/D4), 138.7 (C^B4/D4),

125.2 (C^A3/C3), 124.9 (C^G3/G4), 124.0 (C^E3/F3), 123.8 (C^D5), 123.2 138.6 (C^G2), 132.6 (C^A6/C6), 131.5 (C^F5), 131.2 (C^A5/C5), 130.9

(C^A4/C4), 122.8 (C^B5), 121.2 (C^A4/C4), 120.5 (br C^D3), 120.3 (C^A6/C6), 130.1 (C^A5/C5), 129.8 (C^G3/G5), 128.3 (C^E5), 128.1 (C^G3/G5/G4),

(C^{B3+(A3/C3 or F5)}), 112.6 (C^G2), 108.7 (C^G3/G4), 34.8 (C^Me), signals 128.0 (C^G3/G5/G4), 125.8 (C^E3/F3), 125.2 (C^E3/F3), 124.7 (C^A3/C3),

for C^G5and C^D6not observed. IR (solid, ν/cm⁻¹) 3130 w, 3063 124.5 (C^A3/C3), 123.8 (C^B5/D5), 123.3 (C^B5/D5), 122.9 (C^A4/C4),

w, 3042 w, 2350 w, 2320 w, 1607 m, 1582 m, 1562 w, 1477 s, 121.3 (C^A4/C4), 120.3 (C^B3/D3), 120.2 (C^B3/D3). IR (solid, ν/cm⁻¹

)

1447 m, 1438 w, 1417 m, 1364 w, 1327 w, 1316 w, 1310 w, 1304 3112 w, 3049 w, 2628 w, 2326 w, 2057 w, 1982 w, 1734 w,

w, 1269 w, 1064 w, 1029 w, 840 s, 775 w, 757 m, 729 m, 709 m, 1717 w, 1684 m, 1653 w, 1607 s, 1583 s, 1558 s, 1477 s, 1456 s,

690 m. ESI-MS m/z 735.9 [M − PF₆]⁺(base peak calc. 736.2). 1439 s, 1423 s, 1419 s, 1356 w, 1318 m, 1268 m, 1263 m,

Found C 50.12, H 3.46, N 7.81; C₃₇H₂₉F₆IrN₅P requires C 1228 m, 1164 m, 1126 w, 1063 m, 1030 m, 1010 w, 987 w,

50.45, H 3.32, N 7.95%.

879 w, 828 s, 798 s, 754 s, 727 s, 696 s. ESI-MS m/z: 739.1 [M −

[Ir(ppy)₂(2)][PF₆]. Reactants were [Ir(ppy)₂(μ-Cl)]₂(120.5 mg, PF₆]⁺(base peak calc. 739.1). Found C 47.87, H 3.04, N 5.89;

112.5 μmol) and 2 (50.0 mg, 225.0 μmol) with a reaction time C₃₆H₂₆F₆IrN₄PS·H₂O requires C 47.94, H 3.13, N 6.21%.

of 45 min. [Ir(ppy)₂(2)][PF₆] was isolated as an orange powder

[Ir(ppy)₂(4)][PF₆]. Reactants were [Ir(ppy)₂(μ-Cl)]₂(37.4 mg,

(200.0 mg, 225.0 μmol, 100%). ¹H NMR (500 MHz, 295 K, 34.9 μmol) and 4 (20.0 mg, 69.9 μmol); reaction time was

CD₂Cl₂) δ/ppm 8.48 (d, J = 5.9 Hz, 1H, H^B6), 8.46 (d, J = 8.3 Hz, 45 min. [Ir(ppy)₂(4)][PF₆] was isolated as an orange powder

1H, H^E3), 8.39 (d, J = 8.0 Hz, 1H, H^F3), 8.15 (t, J = 7.9 Hz, 1H, (62.0 mg, 66.6 μmol, 95%). H NMR (500 MHz, 295 K, CD₂Cl₂)

1

H^E4), 8.08 (t, J = 7.9 Hz, 1H, H^F4), 7.99 (d, J = 8.1 Hz, 1H, H^B3), δ/ppm 8.50 (overlapping d, J ≈ 8.0 Hz, 2H, H^E3+F3), 8.13 (m,

7.87 (t, J = 8.0 Hz, 1H, H^B4), 7.81 (m, 2H, H^E6+D3), 7.73 (d, J = 2H, H^E4+F4), 7.87 (m, 3H, H^B3+D3+E6), 7.81 (m, 2H, H^B4+D4), 7.71

7.8 Hz, 1H, H^D4), 7.70 (d, J = 7.9 Hz, 1H, H^A3/C3), 7.52 (d, J = 7.8 (d, J = 5.8 Hz, 1H, H^B6/D6), 7.64 (d, J = 5.5 Hz, 1H, H^G3/G5), 7.59

Hz, 1H, H^F5), 7.40 (m, 3H, H^D6+E5+A3/C3), 7.12 (m, 1H, H^B5), (m, 3H, H^{A3/C3+E5+B6/D6}), 7.37 (m, 2H, H^F5+A3/C3), 7.09 (m, 1H,

7.01 (m, 2H, H^A4/C4+G3/G5), 6.91 (m, 1H, H^D5), 6.78 (t, J = 7.6 H^B5/D5), 6.98 (m, 2H, H^B5/D5+A4/C4), 6.82 (t, J = 7.5 Hz, 1H,

Hz, 1H, H^A5/C5), 6.69 (t, J = 7.8 Hz, 1H, H^A4/C4), 6.55 (t, J = 7.5 H^A5/C5), 6.68 (t, J = 7.5 Hz, 1H, H^A4/C4), 6.51 (m, 1H, H^G4), 6.48

Hz, 1H, H^A5/C5), 6.09 (d, J = 3.4 Hz, 1H, H^G3/G5), 5.98 (d, J = 7.7 (t, J = 7.5 Hz, 1H, H^A5/C5), 6.31 (d, J = 3.7 Hz, 1H, H^G3/G5), 5.97

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Dalton Transactions

(d, J = 7.7 Hz, 1H, H^A6/C6), 5.74 (d, J = 7.7 Hz, 1H, H^A6/C6). ¹³C (500 MHz, 295 K, CD₂Cl₂) δ/ppm 8.46 (d, J = 8.3 Hz, 1H, H^E3),

NMR (126 MHz, 295 K, CD₂Cl₂) δ/ppm 169.4 (C^B2/D2), 167.6 8.38 (dd, J = 8.0, 1.0 Hz, 1H, H^F3), 8.09 (m, 2H, H^E4+F4), 7.99 (d,

(C^B2/D2), 161.1 (C^E2/F2/F6), 157.5 (C^E2/F2/F6), 157.4 (C^E2/F2/F6), J = 8.0 Hz, 1H, H^B3/D3), 7.95 (d, J = 8.2 Hz, 1H, H^B3/D3), 7.85

151.3 (C^A1/C1), 150.8 (C^B6/D6), 150.2 (C^E6), 149.0 (C^B6/D6), 146.7 (ddd, J = 5.5, 1.6, 0.7 Hz, 1H, H^E6), 7.80 (m, 2H, H^B4+D4), 7.71

(C^A1/C1), 144.2 (C^G2), 143.5 (C^A2/C2), 143.2 (C^A2/C2), 139.8 (dd, J = 7.7, 1.3 Hz, 1H, H^A3/C3), 7.67 (m, 2H, H^A3/C3+B6/D6), 7.47

(C^E4+F4), 138.8 (C^B4/D4), 138.7 (C^B4/D4), 134.3 (C^G3/G5), 132.6 (dd, J = 7.9, 1.2 Hz, 1H, H^F5), 7.44 (ddd, J = 5.9, 1.5, 0.8 Hz, 1H,

(C^A6/C6), 132.3 (C^G3/G5), 131.4 (C^E5), 131.3 (C^A5/C5), 130.9 H^B6/D6), 7.35 (m, 1H, H^E5), 7.04 (m, 2H, H^A4/C4+B5/D5), 6.97 (m,

(C^A6/C6), 130.2 (C^A5/C5+G4), 128.3 (C^F5), 125.7 (C^E3/F3), 125.2 2H, H^A4/C4+B5/D5), 6.89 (td, J = 7.6, 1.4 Hz, 1H, H^A5/C5), 6.84 (td,

(C^A3/C3), 124.7 (C^E3/F3), 124.4 (C^A3/C3), 123.8 (C^B5/D5), 123.3 J = 7.5, 1.3 Hz, 1H, H^A5/C5), 6.23 (dd, J = 7.7, 0.8 Hz, 1H,

(C^B5/D5), 122.9 (C^A4/C4), 121.4 (C^A4/C4), 120.3 (C^B3/D3), 120.3 H^A6/C6), 6.05 (dd, J = 7.7, 0.8 Hz, 1H, H^A6/C6), 2.62 (m, 1H, H^d1/d2),

(C^B3/D3). IR (solid, ν/cm⁻¹) 3118 w, 3043 w, 2924 w, 2855 w, 2.44 (m, 1H, H^d1/d2), 1.21 (m, 1H, H^c1/c2), 0.95 (m, 1H, H^c1/c2),

2358 m, 2340 m, 2323 m, 1717 m, 1684 m, 1653 m, 1636 w, 0.73 (m, 1H, H^b1/b2), 0.63 (m, 4H, H^a+b1/b2). ¹³C NMR

1607 m, 1582 m, 1558 m, 1539 m, 1521 w, 1506 m, 1476 s, (126 MHz, 295 K, CD₂Cl₂) δ/ppm 168.2 (C^B2/D2), 168.0 (C^F6),

1457 m, 1436 m, 1420 m, 1405 m, 1316 m, 1306 m, 1297 w, 167.1 (C^B2/D2), 157.3 (C^E2/F2), 155.8 (C^E2/F2), 151.3 (C^A1/C1),

1269 m, 1260 m, 1227 m, 1213 m, 1165 m, 1127 w, 1113 w, 150.7 (C^E6), 149.9 (C^B6/D6), 148.7 (C^B6/D6), 147.0 (C^A1/C1), 143.1

1063 m, 1030 m, 1006 w, 971 w, 878 w, 831 s, 755 m, 728 s, (C^A2/C2), 142.9 (C^A2/C2), 140.1 (C^E4/F4), 139.8 (C^E4/F4), 138.6

720 m, 692 s, 685 s, 677 s, 668 s, 652 m, 641 m. ESI-MS m/z: (C^B4+D4), 132.2 (C^A6/C6), 131.3 (C^A5/C5), 130.9 (C^A5/C5), 130.6

785.1 [M − PF₆]⁺(base peak calc. 785.1). Found C 46.40, H (C^A6/C6), 128.0 (C^E5), 127.5 (C^F5), 125.3 (C^A3/C3), 125.2

2.97, N 5.82; C₃₆H₂₆F₆IrN₄PSe requires C 46.46 H 2.82 N (C^A3/C3+E3), 123.7 (C^A4/C4/B5/D5), 123.5 (C^A4/C4/B5/D5), 123.0

6.02%.

(C^A4/C4/B5/D5), 122.8 (C^F3), 122.6 (C^A4/C4/B5/D5), 120.3 (C^B3/D3),

[Ir(ppy)₂(5)][PF₆]. [Ir(ppy)₂(5)][PF₆] was obtained as an 120.1 (C^B3/D3), 40.6 (C^d), 32.6 (C^c), 22.2 (C^b), 13.8 (C^a). IR

orange powder (89.0 mg, 100.0 µmol, 100%). ¹H NMR (solid, ν/cm⁻¹) 3118 w, 3108 w, 3043 w, 2955 w, 2927 w,

(500 MHz, 295 K, CD₂Cl₂) δ/ppm 8.50 (overlapping d, J ≈ 8.0 2869 w, 2858 w, 2356 s, 2340 s, 2323 s, 2311 m, 1945 w, 1923

Hz, 2H, H^E3+F3), 8.20 (t, J = 7.9 Hz, 1H, H^F4), 8.11 (td, J = 8.2, w, 1848 w, 1829 w, 1751 m, 1734 m, 1706 m, 1695 m, 1653 m,

1.6 Hz, 1H, H^E4), 7.89 (ddd, J = 5.5, 1.6, 0.7 Hz, 1H, H^E6), 7.86 1636 m, 1607 s, 1582 s, 1558 s, 1550 m, 1521 m, 1506 m,

(m, 2H, H^B3/D3+B4/D4), 7.82 (d, J = 8.0 Hz, 1H, H^B3/D3), 7.76 1477 s, 1456 s, 1450 s, 1439 s, 1419 s, 1405 m, 1394 m,

(ddd, J = 8.1, 7.4, 1.5 Hz, 1H, H^B4/D4), 7.70 (d, J = 5.9 Hz, 1H, 1374 m, 1317 m, 1303 m, 1297 w, 1269 m, 1252 w, 1228 w,

H^B6/D6), 7.52 (dd, J = 7.7, 1.2 Hz, 1H, H^A3/C3), 7.46 (dd, J = 7.7, 1186 w, 1165 m, 1125 w, 1099 w, 1063 m, 1030 m, 1004 w,

1.2 Hz, 1H, H^F5), 7.38 (m, 2H, H^B6/D6+E5), 7.25 (d, J = 7.5 Hz, 938 w, 878 m, 830 s, 793 s, 755 s, 736 s, 729 s, 711 m, 694 m,

1H, H^A3/C3), 7.08 (ddd, J = 7.4, 5.9, 1.5 Hz, 1H, H^B5/D5), 7.04 (m, 668 s, 655 w, 643 m, 626 m. ESI-MS m/z: 713.2 [M − PF₆]⁺(base

1H, H^B5/D5), 6.95 (td, J = 7.7, 1.2 Hz, 1H, H^A4/C4), 6.82 (td, J = peak calc. 713.2). Found C 49.13, H 3.84, N 6.57; C₃₆H₃₂F₆IrN₄-

7.5, 1.4 Hz, 1H, H^A5/C5), 6.72 (d, J = 7.7 Hz, 1H, H^G4), 6.64 (br t, P·H₂O requires C 49.37, H 3.91, N 6.40%.

1H, H^G5), 6.58 (td, J = 7.8, 1.2 Hz, 1H, H^A4/C4), 6.42 (t, J = 7.3

[Ir(ppy)₂(7)][PF₆]. [Ir(ppy)₂(7)][PF₆] was obtained as an

Hz, 1H, H^A5/C5), 6.32 (v br, H^G2/G6, see text), 5.94 (dd, J = 7.8, orange powder (87.0 mg, 100.0 µmol, 100%). ¹H NMR

0.9 Hz, 1H, H^A6/C6), 5.62 (dd, J = 7.8, 0.9 Hz, 1H, H^A6/C6), 2.00 (500 MHz, 295 K, CD₂Cl₂) δ/ppm 8.62 (dd, J = 8.2, 1.3 Hz, 1H,

(s, 3H, H^Me). ¹³C NMR (126 MHz, 295 K, CD₂Cl₂) δ/ppm 169.2 H^F3), 8.55 (d, J = 8.4 Hz, 1H, H^E3), 8.29 (t, J = 7.9 Hz, 1H, H^F4),

(C^B2/D2), 167.6 (C^B2/D2), 166.5 (C^E2/F2/F6), 157.3 (C^E2/F2/F6), 156.9 8.13 (dt, J = 8.0, 1.6 Hz, 1H, H^E4), 8.01 (br d, 2H, H^G2), 7.89 (m,

(C^E2/F2/F6), 151.3 (C^A1/C1), 150.5 (C^E6), 149.2 (C^B6/D6), 149.1 3H, H^{B3/D3+B4/D4+E6}), 7.84 (d, J = 8.3 Hz, 1H, H^B3/D3), 7.78 (ddd,

(C^B6/D6), 147.0 (C^A1/C1), 143.3 (C^A2/C2), 142.9 (C^A2/C2), 139.7 J = 8.2, 7.4, 1.5 Hz, 1H, H^B4/D4), 7.68 (dt, J = 5.8, 1.2 Hz, 1H,

(C^F4), 139.4 (C^E4), 138.4 (C^B4/D4), 138.2 (C^B4/D4), 137.3 (C^G3), H^B6/D6), 7.55 (dd, J = 7.8, 1.3 Hz, 1H, H^A3/C3), 7.45 (m, 2H,

131.5 (C^A6/C6), 131.0 (C^A5/C5), 130.5 (C^A6/C6), 130.3 (C^G4), 130.1 H^B6/D6+F5), 7.40 (ddd, J = 7.6, 5.5, 1.2 Hz, 1H, H^E5), 7.29 (dd, J =

(C^F5), 129.4 (C^A5/C5), 128.6 (C^G2), 128.3 (G^G5), 127.8 (C^E5), 125.2 7.9, 1.3 Hz, 1H, H^A3/C3), 7.11 (m, 1H, H^B5/D5), 7.06 (m, 1H, H^B5/D5),

(C^E3/F3), 124.9 (C^A3/C3+G6), 124.3 (C^A3/C3), 123.7 (C^E3/F3), 123.6 6.97 (td, J = 7.7, 1.2 Hz, 1H, H^A4/C4), 6.83 (td, J = 7.5, 1.4 Hz,

(C^B5/D5), 123.0 (C^A4/C4), 122.6 (C^B5/D5), 121.0 (C^A4/C4), 120.1 1H, H^A5/C5), 6.73 (dt, J = 7.7, 1.2 Hz, 1H, H^C4/C4), 6.46 (td, J =

(C^B3+D3), 21.3 (C^Me); signal for C^G1not resolved. ESI-MS m/z: 7.4, 1.3 Hz, 1H, H^A5/C5+ v br, H^G3, see text), 5.94 (dd, J = 7.7,

747.2 [M − PF₆]⁺(base peak calc. 747.2). IR (solid, ν/cm⁻¹

)

1.1 Hz, 1H, H^A6/C6), 5.62 (dd, J = 7.7, 1.1 Hz, 1 H, H^A6/C6). ¹³C

3735 m, 3679 w, 3634 w, 3112 w, 3045 w, 2930 w, 2861 w, NMR (126 MHz, 295 K, CD₂Cl₂) δ/ppm 168.8 (C^B2/D2), 167.5

2360 m, 2356 m, 2340 m, 2331 m, 2311 m, 1734 m, 1717 m, (C^B2/D2), 163.1 (C^F6), 157.6 (C^E2/F2), 153.7 (C^E2/F2), 151.1

1684 m, 1653 m, 1607 m, 1583 m, 1558 m, 1521 m, 1478 m, (C^A1/C1), 150.7 (C^E6), 149.3 (C^B6+D6), 149.2 (C^G2), 146.4 (C^A1/C1),

1447 m, 1436 m, 1419 m, 1339 w, 1316 w, 1297 w, 1270 m, 144.9 (C^G4), 143.3 (C^A2/C2), 143.1 (C^A2/C2), 140.7 (C^F4), 139.8

1228 m, 1165 m, 1125 w, 1107 w, 1064 m, 1030 m, 1001 m, 879 (C^E4), 138.8 (C^B4/D4), 138.7 (C^B4/D4), 131.9 (C^A6/C6), 131.2

w, 832 s, 793 m, 771 w, 755 m, 728 m, 710 m, 696 m, 677 m, (C^A5/C5), 130.6 (C^A6/C6), 130.4 (C^A5/C5), 129.9 (C^F5), 128.3 (C^E5),

668 s, 653 m, 643 m. Found C 52.66, H 3.46, N 6.51; 125.5 (C^E3), 125.1 (C^A3/C3), 125.0 (C^A3/C3), 124.7 (C^F3), 124.0

C₃₉H₃₀F₆IrN₄P requires C 52.52, H 3.39, N 6.28%.

[Ir(ppy)₂(6)][PF₆]. [Ir(ppy)₂(6)][PF₆] was isolated as an (C^A4/C4), 120.5 (C^B3/D3), 120.4 (C^B3/D3). IR (solid, ν/cm⁻¹

orange powder (173.6 mg, 100.0 µmol, 100%). ¹H NMR 3047 w, 2930 w, 2856 w, 2360 s, 2356 m, 2340 m, 2331 m,

(C^B5/D5), 123.3 (C^A4/C4), 123.2 (C^B5/D5), 122.6 (C^G3), 121.8

)

8090 | Dalton Trans., 2013, 42, 8086–8103

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2319 m, 2311 m, 1703 m, 1699 m, 1684 m, 1607 m, 1594 m, (C^E6), 150.0 (C^H4), 149.4 (C^H1), 149.3 (C^B6/D6), 149.2 (C^B6/D6),

1582 m, 1564 m, 1558 m, 1539 m, 1478 m, 1447 m, 1423 m, 146.1 (C^A1/C1), 143.0 (C^A2/C2), 142.9 (C^A2/C2), 139.7 (C^E4), 138.7

1419 m, 1405 m, 1394 m, 1363 m, 1316 w, 1268 m, 1229 m, (C^B4/D4), 138.5 (C^B4/D4), 132.2 (C^A6/C6), 131.0 (C^A5/C5), 130.3 (C^A6/C6),

1217 m, 1165 m, 1131 w, 1110 w, 1063 m, 1031 m, 1008 m, 129.9 (C^A5/C5), 129.1 (C^H2), 128.4 (C^E5), 127.2 (C^F5), 126.1

877 m, 832 s, 801 m, 755 m, 736 m, 729 m, 717 m, 692 m, 668 (C^E3), 124.9 (C^H3), 124.8 (C^A3/C3), 124.4 (C^A3/C3), 123.9 (C^B5/D5),

s, 653 m, 639 m. ESI-MS m/z: 734.2 [M − PF₆]⁺(base peak calc. 123.4 (C^G3+G5, see text), 123.2 (C^A4/C4), 123.1 (C^B5/D5), 122.6

734.2). Found C 50.03, H 3.34, N 7.88; C₃₇H₂₇F₆IrN₅P·0.5H₂O (C^F3), 120.8 (C^A4/C4), 120.2 (C^B3+D3), signal for C^F4not resolved;

requires C 50.05, H 3.18, N 7.89%.

[Ir(ppy)₂(8)][PF₆]. [Ir(ppy)₂(8)][PF₆] was isolated as an 128.8 (C^G2/G6), 128.3 (C^G2/G6), 122.9 (C^G3+G5). IR (solid, ν/cm⁻¹

signals for C^G2/6, C^G1or C^G4not observed at 295 K; at 210 K:

)

orange powder (80.0 mg, 98.9 µmol, 98.9%). ¹H NMR 3120 w, 3108 w, 3055 w, 2965 w, 2937 w, 2879 w, 2860 w,

(500 MHz, 295 K, CD₂Cl₂) δ/ppm 8.69 (d, J = 1.9 Hz, 1H, H^F3), 2356 s, 2340 s, 2323 s, 2311 m, 1945 w, 1923 w, 1848 w,

8.62 (d, J = 8.2 Hz, 1H, H^E3), 8.14 (td, J = 8.1, 1.6 Hz, 1H, H^E4), 1829 w, 1751 m, 1734 m, 1700 m, 1607 m, 1583 m, 1544 w,

7.91 (dd, J = 5.5, 1.6 Hz, 1H, H^E6), 7.89 (m, 2H, H^H2/H3), 7.86 1512 m, 1506 m, 1477 m, 1453 w, 1438 w, 1422 m, 1419 m,

(m, 2H, H^B3/D3+B4/D4), 7.84 (d, J = 8.2 Hz, 1H, H^B3/D3), 7.76 (td, 1395 w, 1344 m, 1317 m, 1309 w, 1295 w, 1269 w, 1228 w, 1164

J = 8.2, 1.5 Hz, 1H, H^B4/D4), 7.70 (m, 2H, H^B6/D6+F5), 7.61 (m, w, 1126 w, 1108 w, 1064 w, 1030 m, 1014 w, 1006 w, 994 w, 828

4H, H^{B6/D6+H2/H3+H4}), 7.54 (dd, J = 7.8, 1.3 Hz, 1H, H^A3/C3), 7.41 s, 820 s, 801 m, 789 m, 752 s, 728 s, 721 m, 694 s, 687 m,

(m, 1H, H^E5), 7.25 (dd, J = 7.8, 1.1 Hz, 1 H, H^A3/C3), 7.08 (m, 675 m, 668 m, 652 m, 641 w. ESI-MS m/z: 899.3 [M − PF₆]⁺

1H, H^B5/D5), 7.04 (m, 1H, H^B5/D5), 6.97 (m, 2H, H^A4/C4+G4), 6.83 (base peak calc. 899.2). Found C 50.41, H 2.96, N 8.00;

(td, J = 7.5, 1.4 Hz, 1H, H^A5/C5), 6.76 (t, J = 7.7 Hz, 2H, H^G3), C₄₄H₃₀F₆IrN₆O₄P requires C 50.62, H 2.90, N 8.05%.

6.62 (dt, J = 7.6, 1.2 Hz, 1H, H^A4/C4), 6.58 (br, H^G2), 6.40 (td, J =

[Ir(ppy)₂(10)][PF₆]. [Ir(ppy)₂(10)][PF₆] was obtained as an

7.5, 1.3 Hz, 1H, H^A5/C5), 5.97 (dd, J = 7.8, 0.9 Hz, 1H, H^A6/C6), orange powder (112.0 mg, 98.8 µmol, 98.8%). ¹H NMR

5.60 (dd, J = 7.8, 0.9 Hz, 1H, H^A6/C6). ¹³C NMR (126 MHz, (500 MHz, 295 K, CD₂Cl₂) δ/ppm 8.69 (d, J = 8.3 Hz, 1H, H^E3),

295 K, CD₂Cl₂) δ/ppm 169.2 (C^B2/D2), 167.7 (C^B2/D2), 166.4 8.65 (d, J = 2.0 Hz, 1H, H^F3), 8.15 (td, J = 8.2, 1.6 Hz, 1H, H^E4),

(C^F2+F6) 157.3 (C^E2), 151.8 (C^F4), 151.7 (C^A1/C1), 150.8 (C^E6), 7.97 (m, 3H, H^E6+B3+D3), 7.85–7.76 (m, 3H, H^B4+D4+B6/D6), 7.72

149.4 (C^B6/D6), 149.3 (C^B6/D6), 147.2 (C^A1/C1), 143.3 (C^A2/C2), (ddd, J = 5.8, 1.6, 0.8 Hz, 1H, H^B6/D6), 7.60 (d, J = 2.0 Hz, 1H,

143.1 (C^A2/C2), 139.7 (C^E4), 138.6 (C^H1), 138.55 (C^B4/D4), 138.5 H^F5), 7.57 (d, J = 6.6 Hz, 1H, H^A3/C3), 7.38 (ddd, J = 7.6, 5.5, 1.1

(C^B4/D4), 138.0 (C^G1), 131.8 (C^A6/C6), 131.7 (C^H3/H4), 131.2 Hz, 1H, H^E5), 7.33 (dd, J = 7.3, 1.1 Hz, 1H, H^A3/C3), 7.12 (m, 1H,

(C^A5/C5), 130.7 (C^A6/C6), 130.2 (C^H2/H3/H4), 130.1 (C^A5/C5), 129.5 H^B5/D5), 7.06 (m overlapping s, 3H, H^B5/D5+H2), 6.97 (td, J = 7.4,

(C^G4), 128.3 (C^G3+E5), 128.0 (C^G2), 127.8 (C^H2/H3), 127.7 (C^F5), 1.6 Hz, 1H, H^A4/C4), 6.82 (td, J = 7.6, 1.4 Hz, 1H, H^A5/C5), 6.65

125.5 (C^E3), 125.1 (C^A3/C3), 125.0 (C^A3/C3), 123.7 (C^B5/D5), 123.2 (td, J = 7.8, 1.2 Hz, 1H, H^A4/C4), 6.50 (td, J = 7.5, 1.3 Hz, 1H,

(C^A4/C4), 122.9 (C^B5/D5), 121.3 (C^F3), 121.2 (C^A4/C4), 120.4 H^A5/C5), 6.34 (br, 1H, H^G2/G6), 5.92 (ddd, J = 7.7, 1.2, 0.5 Hz,

(C^B3+D3). IR (solid, ν/cm⁻¹) 3118 w, 3108 w, 3043 w, 2955 w, 1H, H^A6/C6), 5.74 (ddd, J = 7.6, 1.2, 0.5 Hz, 1H, H^A6/C6), 5.38 (br,

ring

2927 w, 2869 w, 2858 w, 2356 s, 2340 s, 2323 s, 2311 w, 1981 w, 1H, H^G2/G6), 3.95 (s, 6H, H^OMe3

^H), 3.86 (s, 3H,

^G/H), 3.63 (br, 3H,

ring

1607 m, 1582 m, 1541 m, 1533 w, 1477 s, 1451 w, 1439 m, H^OMe4

^G/H), 3.69 (s, 3H, H^OMe4

1423 m, 1412 m, 1397 m, 1368 w, 1364 w, 1316 w, 1307 w, H^OMe3/5

^G), 3.36 (br, 3H, H^OMe3/5

^G). ¹³C NMR

ring

1269 w, 1243 w, 1228 w, 1164 m, 1126 w, 1064 w, 1030 m, 1021 (126 MHz, 295 K, CD₂Cl₂) δ/ppm 168.7 (C^B2/D2), 167.3 (C^B2/D2),

w, 1006 w, 969 w, 877 w, 830 s, 790 m, 754 s, 745 s, 727 s, 692 165.4 (C^F6), 156.8 (C^E2+F2), 154.2 (C^H3), 152.2 (C^G3/G5), 152.0

s, 687 s, 675 m, 653 m. ESI-MS m/z: 809.2 [M − PF₆]⁺(base (C^F4), 151.6 (C^G3/G5), 150.8 (C^A1/C1), 150.7 (C^E6), 149.7 (C^B6/D6),

peak calc. 809.2). Found C 53.55, H 3.47, N 5.59; C₄₄H₃₂F₆IrN₄- 149.4 (C^B6/D6), 147.3 (C^A1/C1), 143.0 (C^A2/C2), 142.4 (C^A2/C2),

P·2H₂O requires C 53.38, H 3.67, N 5.66%.

140.7 (C^G4/H4), 139.7 (C^E4), 138.7 (C^B4/D4), 138.5 (C^B4/D4), 137.4

[Ir(ppy)₂(9)][PF₆]. [Ir(ppy)₂(9)][PF₆] was obtained as an (C^G4/H4), 131.3 (C^A5/C5), 131.6 (C^A6/C6), 130.7 (C^A6/C6), 130.6

orange powder (95.0 mg, 91.0 µmol, 91.0%). ¹H NMR (C^H1), 129.5 (C^A5/C5), 128.9 (C^G1), 128.2 (C^E5), 127.4 (C^F5), 125.9

(500 MHz, 295 K, CD₂Cl₂) δ/ppm 8.88 (d, J = 1.8 Hz, 1H, H^F3), (C^E3), 125.2 (C^A3/C3), 123.9 (C^A3/C3), 123.7 (C^B5/D5), 123.1 (C^A4/C4),

8.79 (d, J = 8.2 Hz, 1H, H^E3), 8.42 (d, J = 8.8 Hz, 2H, H^H3), 8.18 122.9 (C^B5/D5), 121.4 (C^A4/C4), 121.3 (C^F3), 120.1 (C^B3+D3), 106.2

(td, J = 8.1, 1.5 Hz, 1H, H^E4), 8.10 (d, J = 8.9 Hz, 2H, H^H2), 7.90 (C^G2/G6), 105.9 (C^G2/G6), 105.1 (C^H2), 61.1 (C^{OMe4 ring G/H}), 60.2

ring

(m, 3H, H^{B3/D3+B4/D4+E6}), 7.86 (dd, J = 8.2, 0.9 Hz, 1H, H^B3/D3), (C^OMe4

^G/H), 56.9 (C^OMe3

^H), 56.0 (C^{OMe3/5 ring G}), 55.9

7.80 (m, 1H, H^B4/D4), 7.77 (d, J = 5.8 Hz, 1H, H^B6/D6), 7.69 (m, (C^{OMe3/5 ring G}). IR (solid, ν/cm⁻¹) 3055 w, 2997 w, 2935 w, 2840

2H, H^B6/D6+F5), 7.60 (br, H^G3, see text), 7.56 (dd, J = 7.8, 1.2 Hz, w, 1702 w, 1606 m, 1583 m, 1568 w, 1564 w, 1538 w, 1504 m,

1H, H^A3/C3), 7.42 (m, 1H, H^E5), 7.30–6.35 (v br, H^G2+G6) 7.25 1477 m, 1453 m, 1440 w, 1393 m, 1330 m, 1318 w, 1306 w, 1268

(dd, J = 7.8, 1.1 Hz, 2H, H^A3/C3), 7.16 (m, 1H, H^B5/D5), 7.08 (m, w, 1238 m, 1164 w, 1122 m, 1108 m, 1101 m, 1059 w, 1030 w,

1H, H^B5/D5), 6.97 (td, J = 7.7, 1.2 Hz, 1H, H^A4/C4), 6.82 (td, J = 998 m, 968 w, 827 s, 804 m, 787 m, 756 m, 749 m, 728 m,

7.5, 1.4 Hz, 1H, H^A5/C5), 6.63 (td, J = 7.8, 1.1 Hz, 1H, H^A4/C4), 676 m, 669 m, 659 m, 653 m, 639 w. ESI-MS m/z: 989.4 [M −

6.39 (td, J = 7.4, 1.3 Hz, 1H, H^A5/C5), 5.92 (dd, J = 7.7, 0.9 Hz, PF₆]⁺(base peak calc. 989.3). Found C 52.36, H 3.92, N 4.83;

1H, H^A6/C6), 5.59 (dd, J = 7.7, 0.8 Hz, 1H, H^A6/C6). ¹³C NMR C₅₀H₄₄F₆IrN₄O₆P requires C 52.92, H 3.91, N 4.94%.

(126 MHz, 295 K, CD₂Cl₂) δ/ppm 168.4 (C^B2/D2), 167.0 (C^B2/D2),

163.6 (C^F6), 158.2 (C^E2/F2), 156.2 (C^E2/F2), 150.7 (C^A1/C1), 150.6 (102.5 mg, 95.7 µmol) and 11 (50.0 mg, 191.1 µmol) with a

[Ir(ppy)₂(11)][PF₆]. The reactants were [Ir(ppy)₂(μ-Cl)]₂

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Dalton Transactions

reaction time of 1 h. [Ir(ppy)₂(11)][PF₆] was isolated as a red 722 s, 712 m, 694 s, 682 s, 668 s, 655 m, 630 m. ESI-MS m/z:

1

solid (56.0 mg, 61.2 µmol, 32.0%). H NMR (500 MHz, 295 K, 677.2 [M − PF₆]⁺(base peak, calc. 677.2). Found C 46.96, H

CD₂Cl₂) δ/ppm 9.07 (d, J = 1.8 Hz, 1H, H^F6), 8.84 (dd, J = 8.4, 3.82, N 6.53; C₃₂H₂₈F₆IrN₄OP requires C 46.77, H 3.43, N

2.0 Hz, 1H, H^F4), 8.62 (m, 2H, H^E3+F3), 8.44 (d, J = 4.7 Hz, 1H, 6.82%.

H^G6), 8.19 (td, J = 8.0, 1.6 Hz, 1H, H^E4), 8.08 (m, 2H, H^E6+G3),

7.98 (m, 2H, H^B3+D3), 7.91 (td, J = 7.7, 1.7 Hz, 1H, H^G4), 7.80 (t,

Crystallography

J = 7.8 Hz, 2H, H^B4+D4), 7.76 (d, J = 7.9 Hz, 1H, H^A3/C3), 7.73 (d,

Data were collected on a Stoe IPDS diﬀractometer using Stoe

J = 7.8 Hz, 1H, H^A3/C3), 7.60 (d, J = 5.6 Hz, 1H, H^B6/D6), 7.52 (m,

3H, H^B6/D6+E5+G5), 7.09 (td, J = 7.7, 1.2 Hz, 1H, H^A4/C4), 7.03 (m,

3H, H^A4/C4+B5+D5), 6.96 (td, J = 7.4, 1.3 Hz, 1H, H^A5/C5), 6.91 (td,

J = 7.5, 1.3 Hz, 1H, H^A5/C5), 6.33 (overlapping d, J = 7.6 Hz, 2H,

H^A6+C6). ¹³C NMR (126 MHz, 295 K, CD₂Cl₂) δ/ppm 188.3

(C^CvO), 168.3 (C^B2/D2), 167.2 (C^B2/D2), 158.2 (C^E2/F2), 155.4

(C^E2/F2), 154.6 (C^F6), 153.1 (C^G2), 151.6 (C^E6), 150.1 (C^A1/C1),

150.0 (C^A1/C1), 149.2 (C^B6+D6), 149.1 (C^G6), 144.25 (C^A2/C2), 144.2

(C^A2/C2), 141.7 (C^F4), 140.1 (C^E4), 138.9 (C^B4/D4), 138.8 (C^B4/D4),

138.1 (C^G4), 136.0 (C^F5), 132.2 (C^A6/C6), 132.1 (C^A6/C6), 131.3

(C^A5/C5), 131.2 (C^A5/C5), 129.6 (C^E5/G5), 128.1 (C^E5/G5), 126.2

(C^E3/F3), 125.5 (C^A3/C3), 125.4 (C^A3/C3), 125.1 (C^G3), 124.4

(C^E3/F3), 124.0 (C^B5/D5), 123.9 (C^B5/D5), 123.4 (C^A4/C4), 123.35

(C^A4/C4), 120.5 (C^B3/D3), 120.4 (C^B3/D3). IR (solid, ν/cm⁻¹) 3059

IPDS²⁶software and the program SHELXL97,²⁷or on a Bruker-

Nonius KappaAPEX diﬀractometer with data reduction, solu-

tion and refinement using the programs APEX2,²⁸SIR92,²⁹

and CRYSTALS.³⁰ORTEP-type diagrams and structure analysis

used Mercury v. 3.0.^31,32Data are given in Table 1. In

2{[Ir(ppy)₂(9)][PF₆]}·CH₂Cl₂·2H₂O and 2{[Ir(ppy)₂(12)][PF₆]}·MeOH·

2H₂O, partial occupancy water solvates were modelled as

naked O atoms as data quality did not allow location of the H

atoms from the diﬀerence map.

Results and discussion

Ligand synthesis and characterization

w, 2920 m, 2850 m, 2361 w, 1717 m, 1674 m, 1668 m, 1662 m, Of the twelve ligands used in this investigation, compounds 5,

1607 s, 1582 s, 1563 m, 1558 m, 1553 m, 1478 s, 1468 m, 9 and 10 have not been previously reported. Ligands 8, 9 and

1464 m, 1436 m, 1419 m, 1379 m, 1360 m, 1308 m, 1284 m, 10 were prepared by standard Kröhnke methodology.³³We

1270 m, 1246 m, 1228 m, 1165 m, 1141 w, 1127 w, 1114 w, approached the synthesis of 5 using the strategy described by

1092 w, 1065 m, 1032 m, 996 m, 947 m, 878 m, 830 s, 801 s, Jahng et al.^34,35This involves a multistep and multicomponent

795 s, 750 s, 738 s, 730 s, 719 s, 698 s, 678 s, 662 m, 619 m. reaction consisting of the in situ preparation of an enolate

ESI-MS m/z: 762.2 [M − PF₆]⁺(base peak calc. 762.2). Found C which reacts then in a Michael condensation with an enam-

49.61 H 3.10 N 7.74; C₃₈H₂₇F₆IrN₅OP·MeOH requires C 49.89 inone followed by elimination of dimethylamine to give a 1,5-

H 3.33 N 7.46%.

bis(aryl)pentane-1,5-diketone. This reacts further upon

[Ir(ppy)₂(12)][PF₆]. Reactants were 12 (16.4 mg, 93.0 μmol) addition of NH₄OAc in cascade imine condensations leading

and [Ir(ppy)₂(μ-Cl)]₂(50.0 mg, 47.0 μmol) with a reaction time to ring closure to a dihydropyridine; subsequent oxidation

of 1 h. [Ir(ppy)₂(12)][PF₆] was isolated as a dark red powder yields a 2,6-bis(aryl)pyridine. Two approaches can be used,

(61.8 mg, 74.4 μmol, 80.0%). ¹H NMR (500 MHz, 295 K, and these are summarized in Scheme 2. A disadvantage of the

CD₂Cl₂) δ/ppm 8.41 (d, J = 8.0 Hz, 1H, H^E3), 8.26 (m, 2H, methodology is the reversibility of the Michael addition result-

H^B6/D6+c), 8.07 (t, J = 7.7 Hz, 1H, H^E4), 7.97 (m, 2H, H^B3/D3+E6), ing in scrambling of the substituents and competitive for-

7.92 (d, J = 8.1 Hz, 1H, H^B3/D3), 7.80 (m, 2H, H^B4+D4), 7.68 (m, mation of 6′-aryl-2,2′-bpy (I), 2,2′:6′,2″-terpyridine (tpy, II) and

2H, H^A3+C3), 7.47 (m, 1H, H^E5), 7.44 (d, J = 5.9 Hz, 1H, H^B6/D6), 2,6-bis-(aryl)-pyridine (III). In the synthesis of 5, the lower

7.18 (dd, J = 7.4, 5.8 Hz, 1H, H^B5/D5), 7.04 (m, 1H, H^B5/D5), 6.99 route in Scheme 2 was the most eﬀective with 5 and tpy (I and

(m, 2H, H^A4+C4), 6.84 (m, 2H, H^A5+C5), 6.27 (d, J = 7.6 Hz, 1H, II in Scheme 2) being isolated in 54 and 20% yields, respect-

H^A6/C6), 6.20 (m, 2H, H^A6/C6+d) 3.38 (s, 3H, H^Me), 3.26 (s. 3H, ively, and no 2,6-bis(3-tolyl)-pyridine (III in Scheme 2) being

H^Me). ¹³C NMR (126 MHz, 295 K, CD₂Cl₂) δ/ppm 186.9 (C^CvO), formed. The Jahng methodology was also found to be a con-

169.0 (C^B2/D2), 167.9 (C^B2/D2), 159.8 (C^c), 155.2 (C^E2), 150.6 venient route for compound 7 for which the more eﬃcient

(C^E6), 148.9 (C^B6/D6), 148.85 (C^B6/D6), 145.2 (C^A1+C1), 144.9 strategy was the upper one in Scheme 2, starting from 2-acetyl-

(C^A2/C2), 144.2 (C^A2/C2), 139.2 (C^E4), 138.6 (C^B4/D4), 138.4 pyridine and (E)-1-(pyrid-4-yl)-3-N,N-dimethylaminoprop-2-

(C^B4/D4), 133.0 (C^A6/C6), 132.1 (C^A6/C6), 130.4 (C^A5+C5), 130.0 ene-1-one; compound 7 was isolated in 45% yield with only

(C^E5), 127.5 (C^E3), 125.3 (C^A3/C3), 124.9 (C^A3/C3), 123.5 (C^B5/D5), 4% of 4,2′:6′,4″-terpyridine (product III in Scheme 2) as

123.4 (C^B5/D5), 122.8 (C^A4/C4), 122.4 (C^A4/C4), 120.0 (C^B3/D3), byproduct.

119.9 (C^B3/D3), 93.6 (C^d), 47.2 (C^Me), 39.3 (C^Me). IR (solid,

The EI mass spectra of 5, 9 and 10 each exhibited a parent

ν/cm⁻¹) 3125 w, 3056 w, 2931 w, 2862 w, 2358 w, 2329 w, 1630 ion. The ¹H and ¹³C NMR spectra of the new ligands were

s, 1607 s, 1600 m, 1582 m, 1565 m, 1517 s, 1496 s, 1490 s, assigned using COSY, NOESY, DEPT, HMQC and HMBC

1475 s, 1465 m, 1456 m, 1439 m, 1405 s, 1375 m, 1363 m, methods and were fully in accord with the structures drawn in

1299 m, 1259 s, 1252 s, 1245 s, 1227 m, 1161 m, 1141 m, Scheme 1 and with unhindered bond rotation on the NMR

1127 m, 1119 m, 1102 m, 1083 m, 1062 m, 1054 m, 1044 m, timescale. For example in 10, four signals at δ 4.01, 3.98, 3.933

1031 m, 1023 m, 1012 m, 984 m, 967 m, 958 w, 938 w, 906 m, and 3.927 ppm (integral ratio 2 : 2 : 1 : 1) were observed at

887 m, 882 m, 865 m, 832 s, 792 m, 771 m, 756 s, 735 s, 729 s, 295 K for the six methoxy groups.

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Table 1 Crystallographic data for ligands 9 and 10 (two polymorphs) and the complexes

Compound

9

10a

10b

Formula

C₂₂H₁₄N₄O₄

398.37

Yellow block

Monoclinic

C₂₈H₂₈N₂O₆

488.54

Colourless prism

Triclinic

ˉ

P1

C₂₈H₂₈N₂O₆

488.54

Colourless needle

Monoclinic

P2₁/c

Formula weight

Crystal colour and habit

Crystal system

Space group

a, b, c/Å

P2₁/c

20.196(8), 7.0193(16), 13.309(6)

10.5992(2), 11.0302(2), 12.2247(3)

13.0887(7), 17.9889(8), 10.9843(8)

α, β, γ/°

90, 106.79(3), 90

1806.3(11)

1.465

96.3390(10), 108.9380(10), 108.6850(10)

1243.40(5)

1.305

90, 108.615(3), 90

2451.0(3)

1.324

U/Å³

D_c/Mg m⁻³

Z

4

2

4

μ(Mo-Kα)/mm⁻¹

T/K

0.104

173

0.092

123

0.094

123

Refln. collected

Unique refln. (R_int

Refln. for refinement

Parameters

17 964

3189 (0.1149)

2573

43 182

11 963 (0.023)

9173

27 283

5624 (0.054)

3375

)

273

325

Threshold

I > 2σ(I)

0.1076 (0.1260)

0.3112 (0.3266)

1.070

I > 2σ(I)

0.0446 (0.0539)

0.0496 (0.0766)

1.0538

I > 2σ(I)

0.0397 (0.0842)

0.0398 (0.0879)

1.1104

R₁(R₁all data)

wR₂(wR₂all data)

Goodness of fit

CCDC deposition

910293

910297

910295

2{[Ir(ppy)₂(1)]-

[PF₆]}·C₆H₅Me

2{[Ir(ppy)₂(9)]-

[PF₆]}·CH₂Cl₂·2H₂O

2{[Ir(ppy)₂(12)]-

[PF₆]}·MeOH·2H₂O

Compound

[Ir(ppy)₂(10)][PF₆]

Formula

C

₈₁H₆₆F₁₂Ir₂N₁₀P₂

C₈₉H₆₆Cl₂F₁₂Ir₂N₁₂O₁₀P₂

2208.83

Orange plate

Triclinic

ˉ

P1

C₅₀H₄₄F₆IrN₄O₆P

1134.08

Orange block

Monoclinic

P2₁/n

C₆₅H₆₄F₁₂Ir₂N₈O₅P₂

1711.59

Red block

Monoclinic

P2₁/c

Formula weight

Crystal colour and habit

Crystal system

Space group

1853.78

Orange block

Orthorhombic

Pbcn

a, b, c/Å

20.941(4), 20.129(4),

16.916(3)

90, 90, 90

7130(2)

1.727

4

9.776(3), 14.684(5),

17.409(5)

74.15(2), 76.01(2), 72.54(2)

2258.2(12)

1.645

12.5203(8), 18.8096(10),

18.9682(13)

90, 95.328(5), 90

4447.7(5)

1.694

16.4951(12), 13.0662(11),

16.4258(11)

90, 113.986(5), 90

3234.5(4)

1.753

α, β, γ/°

U/Å³

D_c/Mg m⁻³

Z

1

4

2

μ(Mo-Kα)/mm⁻¹

T/K

3.860

173

3.130

173

3.120

173

4.251

173

Refln. collected

Unique refln. (R_int

Refln. for refinement

Parameters

123 452

7385 (0.0734)

6759

30 520

9370 (0.1209)

8294

77 004

10 213 (0.0874)

9844

22 644

7004 (0.0589)

6568

)

529

622

619

446

Threshold

I > 2σ(I)

0.0651 (0.0733)

0.1641 (0.1711)

1.081

I > 2σ(I)

0.0357 (0.0387)

0.0896 (0.0936)

1.161

R₁(R₁all data)

wR₂(wR₂all data)

Goodness of fit

CCDC deposition

0.0431 (0.0484)

0.0828 (0.0848)

1.239

0.0380 (0.0395)

0.0937 (0.0947)

1.095

925641

925643

925642

925640

The electronic absorption spectra of degassed MeCN solu-

tions of ligands 5, 9 and 10 exhibited intense absorptions in

the UV region arising from π*←π or π*←n transitions. Ligands

5, 9 and 10 are emissive at 298 K in degassed MeCN. Excitation

at ca. 280 nm leads to an emission at 342 nm for 5, 458 nm for

9 and 461 nm for 10.

Yellow blocks of 9 grew when an Et₂O solution of the com-

pound was left to evaporate slowly at room temperature. Fig. 1

shows the structure of 9. The bpy unit adopts the expected

trans-conformation. While the nitro group containing N4 lies

within 1° of the plane of the ring to which it is bonded, that

containing N3 is twisted 7.7° out of the corresponding ring

plane. Despite this, the bond parameters for the two NO₂

groups indicate similar degrees of π-delocalization across the

Scheme 2 Possible pathways used in the Jahng methodology and competing

products. Reagents: (i) KO^tBu; (ii) NH₄OAc, HOAc.

C_arene–NO₂units. The four rings in 9 are mutually twisted; the

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Fig. 1 Structure of 9 (ellipsoids plotted at 40% probability). Selected bond dis-

tances and angles: N1–C1 = 1.335(8), N1–C5 = 1.348(7), N2–C10 = 1.338(7),

N2–C6 = 1.339(7), C14–N3 = 1.464(8), C20–N4 = 1.477(8), N3–O2 = 1.226(8),

N3–O1 = 1.228(8), N4–O3 = 1.207(8), N4–O4 = 1.217(8) Å; C1–N1–C5 = 117.5(5),

C10–N2–C6 = 119.8(5), O2–N3–O1 = 122.5(6), O2–N3–C14 = 117.9(6), O1–N3–

C14 = 119.6(6), O3–N4–O4 = 125.1(6), O3–N4–C20 = 118.3(6), O4–N4–C20 =

116.6(6)°.

angles between the rings containing atoms N1/N2, N2/C14 and

N2/C20 are 12.8, 15.8 and 38.0°. The conformation of the

ligand is intimately associated with the molecular packing.

Pairs of pyridine and phenyl rings are slipped with respect to

one another and do not engage in eﬃcient face-to-face π-stack-

ing. Two types of interactions appear to compensate for this:

C–H⋯O_nitroand face-to-face NO₂⋯π contacts.

Polymorphic colourless prisms or needles of 10 grew when

an Et₂O or CH₂Cl₂–Et₂O solution, respectively, of the com-

pound was left to stand. Prisms of 10a and needles of 10b crys-

ˉ

tallize in the triclinic and monoclinic space groups P1 and

Fig. 2 (a) Structure of 10a (ellipsoids plotted at 40% probability). Selected

bond distances: N1–C1 = 1.3531(8), N1–C5 = 1.3473(8), N2–C6 = 1.3496(9), N2–

C10 = 1.3489(9), C13–O1 = 1.3645(8), C14–O2 = 1.3695(8), C15–O3 = 1.3620(8),

C17–O1 = 1.4260(9), C18–O2 = 1.4310(10), C19–O3 = 1.4272(10), C22–O4 =

1.3666(8), C23–O5 = 1.3711(8), C24–O6 = 1.3604(8), C26–O4 = 1.4209(10),

C27–O5 = 1.4249(9), C28–O6 = 1.4291(9) Å. (b) Overlay of the polymorphs 10a

(red) and 10b (green).

P2₁/c, respectively. Fig. 2a shows the structure of 10a, and an

overlay of the molecular structures of the two polymorphs is

shown in Fig. 2b; the same numbering scheme is used for

both polymorphs. In terms of bond distances and angles, the

structures diﬀer little. In both 10a and 10b, the C_arene–O bonds

are shorter than the C_methyl–O bonds, consistent with exten-

sion of the arene π-system onto the O atoms. The degree of

deviation from planarity of the bpy domain in the two poly-

morphs diﬀers (angle between ring planes = 14.8° in 10a and

6.0° in 10b). The most significant diﬀerence between 10a and

10b lies in the relative orientations of the 3,4,5-trimethoxy-

phenyl substituents. With respect to the pyridine ring contain-

ing atom N1, the phenyl rings are twisted 38.8 and 33.9° in

10a, and 31.5 and 14.6° in 10b. In each polymorph, the three

methoxy substituents are arranged with the 3- and 5-substi-

tuted OMe groups lying approximately in the plane of the

phenyl ring while the 4-OMe unit lies approximately ortho-

gonal to it.

envelope corresponding to the [M − PF₆]⁺ion with an isotope

pattern consistent with that calculated.

The ¹H and ¹³C NMR spectra of the complexes were

recorded in CD₂Cl₂and were assigned with the help of COSY,

DEPT, NOESY, HMBC and HMQC methods and representative

variable temperature experiments. The NMR spectroscopic sig-

natures of [Ir(ppy)₂(N^N)][PF₆] for L = 1–11 confirmed that

each ligand L acts as an N,N’-chelate; ligand 12 is an N,O-

donor. Structural data (see below) confirmed that the O-atom

of 12 lies trans to the C-donor of a [ppy]⁻ligand as shown in

Scheme 3. In the parent complex [Ir(ppy)₂(bpy)]⁺, the two

[ppy]⁻ligands are equivalent but in each of [Ir(ppy)₂(N^N)]⁺

for L = 1–11, the presence of the 6- or 4,6-substituents desym-

metrizes the complex and the two pyridine rings and the two

cyclometallated rings of the [ppy]⁻ligands are inequivalent.

The ¹H NMR spectrum of [Ir(ppy)₂(3)][PF₆] is shown in Fig. 3a.

Signals for protons in rings A and C are well separated in the

spectrum, but the distinction between resonances for protons

Synthesis, mass spectrometric and NMR spectroscopic

characterization of complexes

The complexes [Ir(ppy)₂(N^N)][PF₆] in which

L = 1–12

22,23

(Scheme 1) were synthesized by treating [Ir(ppy)₂(μ-Cl)]₂

with L followed by anion exchange (Scheme 3). The electro-

spray mass spectrum of each product exhibited a peak

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sphere. This has been confirmed in the single crystal structure

of [Ru(bpy)₂(11)][PF₆]₂.³⁸

The chirality of the tris-chelate [Ir(ppy)₂(N^N)]⁺cations has

1

an influence only on the H NMR spectrum of [Ir(ppy)₂(6)][PF₆],

in which the three CH₂groups of the butyl substituent in 6

are rendered diastereotopic. Signals for H^d(closest CH₂to

the chiral iridium(^III) centre) appear as two multiplets at δ 2.62

and 2.44 ppm, while for H^cand H^b, pairs of signals at δ 1.21

and 0.95 ppm, and at δ 0.73 and 0.63 ppm, respectively, are

observed.

1

In the H and ¹³C NMR spectra of [Ir(ppy)₂(N^N)][PF₆] with

L = 2, 3, 4, 6, 11 and 12, all signals are sharp and well resolved.

For the remaining complexes, dynamic behaviour causes

broadening of some signals. In the spectrum of [Ir(ppy)₂(1)][PF₆],

the signal at δ 3.01 ppm arising from the N-methyl group

is broad (FWHM = 110 Hz) at 295 K. Signals for H^D3and H^D6

are significantly broadened, while that assigned to H^G5has an

approximate line width (FWHM) of 650 Hz. The ring labels are

defined such that the pyrrole ring G lies over the [ppy]⁻ligand

containing rings C and D. Bearing in mind the solid-state

structure described below, the broadened signals in the solu-

Scheme 3 Synthesis of [Ir(ppy)₂(N^N)][PF₆]. Conditions: (i) 2 equivalents of L,

MeOH, 120 °C in a microwave reactor; (ii) NH₄PF₆. See Scheme 1 for L.

1

tion H NMR spectrum are consistent with hindered rotation

of the N-methyl group. Proton H^G5is adjacent to, and H^D6lies

below, the N-methyl substituent and both experience the

eﬀects of the changing proton environments as the methyl

group rotates.

In the room temperature ¹H NMR spectrum of [Ir(ppy)₂(5)][PF₆],

signals for the 3-tolyl group of 5 are broadened; the signals

for H^G4and H^G5appear as

a broadened doublet and

triplet, respectively, while a broad signal centred around δ

6.3 ppm (FWHM ≈ 100 Hz) is assigned to the coalescence of

H^G2and H^G6(Fig. 4a). The ¹³C NMR signals for C^G2and C^G6(δ

128.6 and 124.9 ppm) were assigned on the basis of HMBC

cross peaks to H^Meand H^G4, and to H^G4, respectively, as no

HMQC cross peaks to the broad proton signal shown in Fig. 4a

were observed. The dynamic behaviour of [Ir(ppy)₂(8)]⁺is

Fig. 3 500 MHz ¹H NMR spectra of (a) [Ir(ppy)₂(3)][PF₆] and (b) [Ir(ppy)₂(11)][PF₆].

See Schemes 1 and 3 for ring and atom labelling. Scales are in δ/ppm.

in pyridine rings B and D is less clear. This observation is

typical for ¹H spectra of all complexes [Ir(ppy)₂(N^N)][PF₆]

for L = 1–10 and in related iridium(^III) complexes.^36,37In

[Ir(ppy)₂(11)][PF₆], the environments of cyclometallated rings A

and C are more similar (Fig. 3b) than in [Ir(ppy)₂(N^N)][PF₆]

with L = 1–10. This can be rationalized in terms of the substi-

tution pattern in pyridine ring F. In [Ir(ppy)₂(N^N)][PF₆] with

L = 1–10, the 6-substituent lies over ring C (see structural dis-

cussions below), whereas in [Ir(ppy)₂(11)][PF₆], the 5-substitu-

ent is not so intimately associated with the coordination

Fig. 4 Parts of the room temperature 500 MHz ¹H NMR spectra of CD₂Cl₂solu-

tions of (a) [Ir(ppy)₂(5)][PF₆] and (b) [Ir(ppy)₂(10)][PF₆].

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similar to that of [Ir(ppy)₂(5)]⁺; signals for phenyl ring G current of phenyl ring C over which ring G is stacked in the

protons H^G4, H^G3and H^G2in [Ir(ppy)₂(8)][PF₆] appear as a static structure. The solid-state structure of [Ir(ppy)₂(9)][PF₆] is

triplet, broadened triplet and broad signal (FWHM ≈ 30 Hz), detailed below.

respectively at 295 K. In contrast to the hindered rotation of

ring G on the NMR timescale, the 4-substituted phenyl ring H

(Scheme 1) undergoes fast rotation. The fluxional behaviour

of [Ir(ppy)₂(8)]⁺is reminiscent of that reported for

[Ir(ppy)₂(N^N)]⁺where L = 4-(3,5-dibromophenyl)-6-phenyl-

2,2′-bipyridine.³⁶The pendant pyridyl ring in 7 also undergoes

hindered rotation at 295 K in a CD₂Cl₂solution of [Ir(ppy)₂(7)][PF₆].

A broadened doublet at δ 8.01 ppm with a reduced coup-

ling constant of ≈5 Hz is assigned to H^G2(Scheme 1). This

doublet shows a COSY cross peak to a broad signal centred at

δ 6.47 ppm and the latter is assigned to the coalescence of

signals for H^G3and H^G5. The proton signals at δ 8.01 and

6.47 ppm correlate (HMQC) with ¹³C NMR resonances at 149.2

and 122.6 ppm, consistent with the higher frequency signal

arising from the ¹³C nucleus adjacent to the nitrogen atom.

Fig. 4b shows part of the solution ¹H NMR spectrum of

[Ir(ppy)₂(10)][PF₆] at 295 K. The inequivalence and shielding of

H^G2and H^G6(Scheme 1) are consistent with the solid-state

structure described below. The broadening of the signals indi-

cates some degree of dynamic behaviour. In contrast, ring H

(Scheme 1) undergoes fast rotation on the NMR timescale with

the ortho-protons giving rise to a sharp singlet at δ 7.06 ppm.

As a representative study, we recorded the ¹H NMR spec-

trum of [Ir(ppy)₂(9)][PF₆] at temperatures over the range 295 to

210 K. Most signals are essentially independent of temp-

erature, but Fig. 5 illustrates that a broad signal (δ 7.60 ppm)

assigned to H^G3at 295 K collapses on cooling and gives rise to

two signals at δ 7.42 and 7.74 ppm. In the 295 K spectrum, a

very broad signal (FWHM ≈ 150 Hz) centred ca. δ 6.8 ppm can

be discerned. On cooling, this sharpens to give a doublet (δ

6.22 ppm) at 210 K (Fig. 5); its partner appears at δ 7.37 ppm

at 210 K. These signals are assigned to H^G2and H^G6, and the

significant diﬀerence in their chemical shifts is consistent

with the two protons facing into and away from the ring

Single crystal structures

Single crystals of 2{[Ir(ppy)₂(1)][PF₆]}·C₆H₅Me were grown by

layering

a chloroform solution of [Ir(ppy)₂(1)][PF₆] with

toluene. Fig. 6 shows the structure of the [Ir(ppy)₂(1)]⁺cation

in the asymmetric unit. The iridium(^III) ion is octahedrally

sited with the pyridine rings of the two [ppy]⁻ligands in the

anticipated trans-arrangement. The cation is chiral and since

the compound crystallizes in the orthorhombic Pbcn space

group, both the Δ- (Fig. 6a) and Λ-enantiomers are present in

Fig. 6 (a) Structure of the Δ-[Ir(ppy)₂(1)]⁺cation in 2{[Ir(ppy)₂(1)]-

[PF₆]}·C₆H₅Me (H atoms omitted; ellipsoids plotted at 30% probability). Selected

bond parameters: Ir1–N1 = 2.144(4), Ir1–N2 = 2.193(4), Ir1–N4 = 2.037(5), Ir1–

N5 = 2.034(4), Ir1–C16 = 1.990(5), Ir1–C27 = 2.012(5), N3–C15 = 1.442(11) Å;

N1–Ir1–N2 = 75.55(16), N5–Ir1–C27 = 80.4(2), N4–Ir1–C16 = 80.6(2), N4–Ir1–N5

= 170.13(17), C27–Ir1–N1 = 178.17(17), C16–Ir1–N2 = 167.6(2), C27–Ir1–N2 =

102.64(17)^o. (b) Projection of the cation to illustrate the twisting of ligand 1.

(c) Stacking of the N-pyrrole ring over one of the two [ppy]⁻ligands.

Fig. 5 Part of the variable temperature 500 MHz ¹H NMR spectrum of a

CD₂Cl₂solution of [Ir(ppy)₂(9)][PF₆] showing coalescence of pairs of ortho- and

meta-protons in 4-nitrophenyl ring G.

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the unit cell. The presence of the N-methyl pyrrole ring causes

distortion as can be seen from the four obtuse bond angles

listed in the caption to Fig. 6a. Whereas the two [ppy]⁻ligands

are essentially planar, the backbone of 1 is noticeably twisted

(Fig. 6b); the angles between the least squares planes of the

rings containing N1/N2 and N2/N3 are 21.7 and 53.4°. The

latter allows the pyrrole ring to stack over one [ppy]⁻ligand

(Fig. 6c, distance from centroid of pyrrole ring to plane of

[ppy]⁻= 3.4 Å), but the angle between the planes of aromatic

domains is 19.3°. The N-methyl substituent appears to steri-

cally hinder the face-to-face π-interaction, and is responsible

for the distorted octahedral geometry of atom Ir1. However, we

note that in [Cu(1)₂][PF₆] (pseudo-tetrahedral copper(I) ion),

the two ligands in the cation achieve an eﬃcient intramole-

cular aryl embrace with a face-to-face π-interaction between the

pyrrolyl unit of one ligand and the central pyridine ring of the

other.¹⁸It is not, therefore, the presence of the N-methyl group

per se that prevents the interaction in [Ir(ppy)₂(1)]⁺being more

eﬃcient, rather a combination of this and the angular restric-

tion that the octahedral coordination sphere imposes. The

toluene molecule is disordered over a special position, as is

one of the two half [PF₆]⁻anions present in the asymmetric

unit. Pairs of cations embrace one another through a face-to-

face interaction between the [ppy]⁻ligands containing N1 and

N4ⁱ(symmetry code i = x, 1 − y, −¹/₂+ z) but the relative orien-

tations of the rings does not allow for the most eﬃcient of

packing interactions. CH⋯F contacts make a major contri-

bution to the overall packing interactions.

Fig. 7 Structure

of

the

Δ-[Ir(ppy)₂(9)]⁺

cation

in

racemic

2{[Ir(ppy)₂(9)][PF₆]}·CH₂Cl₂·2H₂O (H atoms omitted; ellipsoids plotted at 30%

probability). Selected bond parameters: Ir1–N1 = 2.144(4), Ir1–N2 = 2.201(4),

Ir1–N5 = 2.046(5), Ir1–N6 = 2.055(5), Ir1–C23 = 2.014(5), Ir1–C34 = 1.993(4),

C14–N3 = 1.465(7), N3–O1 = 1.196(9), N3–O2 = 1.240(10), C20–N4 = 1.469(6),

N4–O3 = 1.226(7), N4–O4 = 1.235(7) Å; N1–Ir1–N2 = 75.98(14), C34–Ir1–N6 =

80.6(2), C23–Ir1–N5 = 80.2(2), N5–Ir1–N6 = 174.53(15), O1–N3–O2 = 123.1(6),

O3–N4–O4 = 124.0(5)^o.

Slow evaporation of CH₂Cl₂solutions of [Ir(ppy)₂(9)][PF₆] or

[Ir(ppy)₂(10)][PF₆] produced single crystals of X-ray quality. The

former crystallized as 2{[Ir(ppy)₂(9)][PF₆]}·CH₂Cl₂·2H₂O and

structural determination confirmed the expected octahedral

coordination environment of the iridium(^III) ion. The racemic

ˉ

complex crystallizes in the centrosymmetric P1 space group;

the structure of the Δ-enantiomer is shown in Fig. 7.

[Ir(ppy)₂(10)][PF₆] crystallizes in the centrosymmetric P2₁/n space

group and enantiomers of the octahedral cation are present in

the lattice; the structure of the Λ-[Ir(ppy)₂(10)]⁺cation is

depicted in Fig. 8. Bond lengths and angles in both complexes

are unexceptional and selected data are given in the captions

to Fig. 7 and 8. In [Ir(ppy)₂(9)]⁺, each nitro group lies in the

plane of the phenyl ring to which it is bonded consistent with

electron delocalization. The plane of the phenyl ring contain-

ing C17 is twisted 32.0° with respect to the pyridine ring with

N2; the plane of 6-substituted ring (containing C11) deviates

from the plane of the pyridine ring containing N2 by 63.4°. In

[Ir(ppy)₂(10)]⁺, the corresponding twist angles are 28.3 and

70.5°. The greater twisting of the 6-substituent is consistent

with it lying over one of [ppy]⁻ligands – that containing N5 in

[Ir(ppy)₂(9)]⁺or N4 in [Ir(ppy)₂(10)]⁺. The face-to-face π-inter-

action that results is more eﬃcient in [Ir(ppy)₂(10)]⁺than in

Fig. 8 Structure of the Λ-[Ir(ppy)₂(10)]⁺cation in racemic [Ir(ppy)₂(10)][PF₆]

(H atoms omitted; ellipsoids plotted at 30% probability). Selected bond par-

ameters: Ir1–N1 = 2.134(3), Ir1–N2 = 2.204(3), Ir1–N3 = 2.053(3), Ir1–N4 =

2.047(3), Ir1–C35 = 2.012(4), Ir1–C46 = 2.012(4), C13–O1 = 1.361(5), C17–O1 =

1.424(6), C14–O2 = 1.371(5), C18–O2 = 1.412(6), C15–O3 = 1.363(5), C19–O3 =

1.427(6), C22–O4 = 1.355(5), C26–O4 = 1.422(6), C2–O5 = 1.373(4), C27–O5 =

1.420(5), C24–O6 = 1.367(5), C28–O6 = 1.426(6) Å; N1 Ir1 N2 75.04(11), C35–

Ir1–N3 = 81.01(16), C46–Ir1–N4 = 80.21(16), N4–Ir1–N3 = 171.26(13)^o.

[Ir(ppy)₂(9)]⁺(Fig. 9), the angle between the least squares addition to face-to-face π-stacking between symmetry related

planes of the phenyl and [ppy]⁻unit being 5.5 and 18.2°, pairs of trimethoxyphenyl domains (interplane distance =

respectively.

3.55 Å and inter-centroid separation = 3.75 Å between rings

In [Ir(ppy)₂(10)][PF₆], the [PF₆]⁻anion is ordered. Packing containing C20 and C20ⁱ, symmetry code i = 1 − x, −y, −z). The

interactions involve extensive CH⋯F and CH⋯O contacts, in [PF₆]⁻anion in 2{[Ir(ppy)₂(9)][PF₆]}·CH₂Cl₂·2H₂O is ordered;

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Fig. 9 Intra-cation face-to-face π-stacking in (a) [Ir(ppy)₂(9)]⁺and (b) [Ir(ppy)₂(10)]⁺.

Fig. 10 Stacking interactions between centrosymmetric pairs of 4-nitrophenyl

substituents in 2{[Ir(ppy)₂(9)][PF₆]}·CH₂Cl₂·2H₂O.

Fig. 11 (a) Structure of the Δ-[Ir(ppy)₂(12)]⁺cation in racemic

2{[Ir(ppy)₂(12)][PF₆]}·MeOH·2H₂O (H atoms omitted; ellipsoids plotted at 30%

probability). Selected bond parameters: Ir1–N1 = 2.137(4), Ir1–O1 = 2.173(3),

Ir1–N3 = 2.021(4), Ir1–N4 = 2.033(4), Ir1–C11 = 1.987(5), Ir1–C22 = 2.002(5),

C7–C8 = 1.385(7), N2–C8 = 1.314(6), N2–C9 = 1.449(7), N2–C10 = 1.463(7),

O1–C6 = 1.253(6) Å; N1–Ir1–O1 = 75.40(13), C22–Ir1–N4 = 80.92(18), C11–Ir1–

N3 = 80.72(19), N3–Ir1–N4 = 173.92(16), C8–N2–C9 = 122.3(4), C8–N2–C10 =

the structure contains disordered solvates modelled as half-

occupancy CH₂Cl₂and four half occupancy water molecules.

Packing interactions between cations and anions involve short

CH⋯F and CH⋯O contacts. Intermolecular interactions

between nitro-substituents have been studied in detail and a

variety of modes are present in organic nitro-derivatives; where

hydrogen bonds are absent, zig-zag NO⋯N or O⋯O contacts

have been observed.³⁹In 2{[Ir(ppy)₂(9)][PF₆]}·CH₂Cl₂·2H₂O,

120.2(5), C9–N2–C10

=

117.5(4)^o. (b) Packing of pairs of centrosymmetric

cations through NMe₂⋯alkene contacts.

the 4-nitrophenyl group (containing N4) engages in

a

and C10 from a least squares plane being 0.03 Å. The [PF₆]⁻

anion is ordered, but solvent molecules are disordered and

have been modelled as a half-occupancy MeOH molecule and

two half-occupancy water molecules. Ignoring the disordered

solvent molecules, packing interactions involve CH⋯F and

CH⋯O contacts. Pairs of cations related by an inversion centre

embrace one another through NMe₂⋯alkene interactions

(Fig. 11b). The shortest H⋯C_alkeneseparations are 2.88 Å.

stacked interaction with a symmetry related substituent (con-

taining N4ⁱ, i = 2 − x, −1 − y, 1 − z) in an adjacent cation

(Fig. 10); the interplane separation is 2.90 Å, and N4⋯O3ⁱ=

2.97(1) Å.

The chelation of ligand 12 through an N,O-donor set was

confirmed with a single crystal structure determination of

2{[Ir(ppy)₂(12)][PF₆]}·MeOH·2H₂O. The complex crystallizes in

the centrosymmetric space group P2₁/c with both enantiomers

of the octahedral tris(chelate) in the unit cell. Fig. 11a shows

the structure of the Δ-[Ir(ppy)₂(12)]⁺cation. The trans-arrange-

ment of the N-donors of the two [ppy]⁻ligands is expected

and consistent with the other structures reported in this work.

Bond parameters for the coordination environment are typical.

The O1–C6 bond distance of 1.253(6) Å indicates retention of

C–O π-character upon coordination of the ketone unit; conju-

gation extends along the alkene and dimethyl amino backbone

with the greatest deviation of any of atoms C6, C7, C8, N2, C9

Electrochemistry

The complexes are all redox active. Oxidation and reduction

potentials measured using cyclic voltammetry are summarized

in Table 2. The reversible oxidation wave is assigned to an

iridium-centred process, in keeping with theoretical calcu-

ox

lations carried out on related complexes.⁴⁰Values of E in Table 2

1/2

compare to 0.81 V for the complex [Ir(ppy)₂(6-Phbpy)][PF₆] where

6-Phbpy = 6-phenyl-2,2′-bipyridine.⁴¹The structural influence

8098 | Dalton Trans., 2013, 42, 8086–8103

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Table 2 Cyclic voltammetric data for [Ir(ppy)₂(N^N)][PF₆] with L = 1–12 with

respect to Fc/Fc⁺; MeCN solutions with [ⁿBu₄N][PF₆] as supporting electrolyte

and scan rate of 0.1 V s⁻¹. Processes are reversible unless otherwise stated; qr =

quasi-reversible, irr = irreversible

[Ir(ppy)₂(N^N)]⁺

E^o_1/^x₂/V

E^r₁^e_/2^d/V

E_gap/eV

[Ir(ppy)₂(1)]⁺

[Ir(ppy)₂(2)]⁺

[Ir(ppy)₂(3)]⁺

[Ir(ppy)₂(4)]⁺

[Ir(ppy)₂(5)]⁺

[Ir(ppy)₂(6)]⁺

[Ir(ppy)₂(7)]⁺

[Ir(ppy)₂(8)]⁺

[Ir(ppy)₂(9)]⁺

[Ir(ppy)₂(10)]⁺

[Ir(ppy)₂(11)]⁺

[Ir(ppy)₂(12)]⁺

0.80

0.92

0.88

0.85

0.96

0.91

0.86

0.95

0.85

0.90

0.67

−1.80, −2.47, −2.60^qr

−1.77, −2.45, −2.62

−1.78, −2.45, −2.58^qr

−1.77, −2.43, −2.58^qr

−1.80^qr, −2.24, −2.46^qr

−1.85^qr, −2.32, −2.57

−1.74^qr, −2.16, −2.44, −2.56

−1.76^qr, −2.38, −2.58^qr

−1.30, −1.51, −1.64

−1.78, −2.39, −2.58^qr

−1.33, −1.80

2.18

2.27

2.24

2.19

2.31

2.38

2.26

2.25

1.81

2.22

1.86

1.89

−1.58, −2.08, −2.54

of the 6-substituent on the electronic structure of the

ox

1/2

complex is clear from the variation in E

which does not

follow a simple pattern based on electron withdrawing or

releasing nature of the substituents. Replacing the bpy-ligand

by the N,O-donor in [Ir(ppy)₂(12)][PF₆] results in a more easily

oxidized metal centre. Each of [Ir(ppy)₂(N^N)][PF₆] with L =

1–8 and 10 exhibits a reversible or quasi-reversible ligand-

based reduction process close to the −1.75 V observed for

[Ir(ppy)₂(6-Phbpy)][PF₆].⁴¹[Ir(ppy)₂(9)][PF₆] exhibits three

reversible processes at lower potentials (Table 2) consistent

with reduction processes associated with the nitrophenyl

substituents.

Photophysical properties

Fig. 12 Electronic absorption spectra of [Ir(ppy)₂(N^N)][PF₆] in degassed

MeCN: (a) L = 1–4; (b) L = 5, 8, 9 and 12.

Table 3 lists the absorption maxima in the UVVIS spectra of

[Ir(ppy)₂(N^N)][PF₆] with L = 1–12. Representative spectra are

shown in Fig. 12. All the complexes are orange with the excep-

tion of [Ir(ppy)₂(11)][PF₆] and [Ir(ppy)₂(12)][PF₆] which are red

and dark red, respectively. Fig. 12a shows that the absorption

spectra of [Ir(ppy)₂(N^N)][PF₆] with L = 1–4 are similar, with

broad, intense absorptions in the UV region and a tail into the

visible region. A similar spectrum is observed for [Ir(ppy)₂(5)][PF₆]

(Fig. 12b) and [Ir(ppy)₂(7)][PF₆]. The introduction of ad-

ditional aromatic susbtituents on going to [Ir(ppy)₂(8)][PF₆],

[Ir(ppy)₂(9)][PF₆] and [Ir(ppy)₂(10)][PF₆] is accompanied by the

expected increase in intensity of the ligand-based absorptions

(Fig. 12b). On going to [Ir(ppy)₂(12)][PF₆] (Fig. 12b), a relatively

intense absorption at 410 nm is observed which we assign to

an MLCT band.

Table 3 Electronic absorption band maxima for MeCN (degassed) solutions of

[Ir(ppy)₂(N^N)][PF₆] with L = 1–12

With the exception of [Ir(ppy)₂(12)][PF₆] which contains an

N,O-chelating ligand, all the complexes are orange emitters in

degassed MeCN solution at room temperature. The excitation

and emission wavelengths are given in Table 4; the excitation

spectrum of each complex was recorded to confirm the origin

Cation

λ_max/nm (ε_max/10³dm³mol⁻¹cm⁻¹

)

[Ir(ppy)₂(1)]⁺

[Ir(ppy)₂(2)]⁺

[Ir(ppy)₂(3)]⁺

[Ir(ppy)₂(4)]⁺

252 (44.5), 264 (43.3), 287sh (30.4), 375 (3.4)

250 (37.0), 264 (34.0), 286sh (23.8), 377 (3.7)

248 (50.8), 264 (46.2), 296sh (28.5), 378 (3.7)

249 (32.9), 264 (30.0), 305sh (16.0), 324sh (11.3), 384

(2.4)

261 (40.6), 310 (21.5), 380 (3.7)

256 (49.2), 306 (25.8), 380 (4.7)

257 (57.6), 310 (31.0), 379 (8.9)

268 (51.2), 320sh (21.1), 383 (6.1)

253sh (58.0), 270 (64.5), 383 (9.5)

of the emission. For the complexes containing 6-substituted

[Ir(ppy)₂(5)]⁺

[Ir(ppy)₂(6)]⁺

[Ir(ppy)₂(7)]⁺

[Ir(ppy)₂(8)]⁺

[Ir(ppy)₂(9)]⁺

em

max

bpy ligands 1–5 and 11, λ

lies in the range 601–608 nm.

Each of these ligands contains an aromatic substituent. These

emission wavelengths are red-shifted with respect to those of

the 585 nm for [Ir(ppy)₂(bpy)][PF₆]⁴⁰and 595 nm for

[Ir(ppy)₂(6-Phbpy)][PF₆] (6-Phbpy = 6-phenyl-2,2′-bipyridine).⁴¹

A blue-shift in the emission (to 575 nm) is observed on going

[Ir(ppy)₂(10)]⁺257 (45.9), 270 (46.2), 291sh (40.2), 391 (7.3)

[Ir(ppy)₂(11)]⁺262 (53.8), 310 (27.8), 382 (5.3)

[Ir(ppy)₂(12)]⁺257 (58.7), 410 (25.2)

Dalton Trans., 2013, 42, 8086–8103 | 8099

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Table 4 Room temperature emission data for MeCN (degassed, 1.0 × 10⁻⁵mol

dm⁻³) solutions of [Ir(ppy)₂(N^N)][PF₆] with L = 1–11

em

max

[Ir(ppy)₂(N^N)]⁺

λ_exc/nm

λ

/nm

Quantum yield^a

[Ir(ppy)₂(1)]⁺

[Ir(ppy)₂(2)]⁺

[Ir(ppy)₂(3)]⁺

[Ir(ppy)₂(4)]⁺

[Ir(ppy)₂(5)]⁺

[Ir(ppy)₂(6)]⁺

[Ir(ppy)₂(7)]⁺

[Ir(ppy)₂(8)]⁺

[Ir(ppy)₂(9)]⁺

[Ir(ppy)₂(10)]⁺

[Ir(ppy)₂(11)]⁺

257

260

259

261

257

262

265

362

257

259

608

601

606

575

605

611

578

607

601

<0.01

0.04

<0.01

^aPL and QY measurements were made on diﬀerent instruments, see

Experimental section.

from the latter to [Ir(ppy)₂(6)]⁺which contains a 6-ⁿbutyl sub-

stituent. For complexes containing the 4,6-disubstituted

ligands 8–10, the eﬀect of the substituents is most noticeable

em

max

for 9 where λ

is blue-shifted by ca. 30 nm upon the intro-

duction of the electron withdrawing nitro-groups (Table 4).

With the exception of [Ir(ppy)₂(7)][PF₆] which contains the

pendant pyridyl substituent, quantum yields are below the

detectable limit of the instrument (Table 4).

Photoluminescence in thin films and ionic liquid medium

Five of the complexes were selected for an investigation of

their photoluminescence in thin films (5% in weight of the

complex in PMMA) and in ionic liquid (1-butyl-3-methylimid-

azolium hexafluoridophosphate) with a molar ratio iTMC : IL

4 : 1 (device configuration). Two families were chosen:

[Ir(ppy)₂(N^N)][PF₆] in which N^N = 1–3 (aromatic heterocyclic

substituent in the 6-position of the bpy ligand) and

[Ir(ppy)₂(N^N)][PF₆] with N^N = 8 and 10 (4,6-diaryl-substituted

bpy ligands). The diluted thin-film photoluminescence spectra

exhibited maxima at 565, 564 and 563 nm with quantum

yields of 34, 42 and 41% for N^N = 1, 2 and 3, respectively (λ_exc

= 314 nm). Each emission is blue shifted by ca. 40 nm with

Fig. 13 Photoluminescence spectra for [Ir(ppy)₂(N^N)][PF₆]/[BMIM][PF₆] (4 : 1)

in the solid state: (a) N^N = 1–3, (b) N^N = 8 and 10.

Device performances

respect to the solution maximum (Table 4) but, as in solution, In view of the promising photoluminescence eﬃciency data

a change in the heteroatom in the pendant substituent in the for the thin films, LEC devices were prepared using the com-

N^N ligand has minimal eﬀect upon the emission. In an ionic plexes [Ir(ppy)₂(N^N)][PF₆] with N^N = 1, 2, 3, 8 and 10 accord-

liquid medium (Fig. 13a), the emissions are again similar for ing to the procedure described in the Experimental section.

em

max

the three complexes (λ

= 595, 595 and 594 for the complexes Devices consisted of a 100 nm emitting layer, comprising the

with N^N = 1, 2 and 3, respectively) and are red-shifted with iTMC-complex and the ionic liquid [BMIM][PF₆] in a molar

respect to the diluted thin film emission maxima; quantum ratio of iTMC : IL 4 : 1, sandwiched between an ITO/PEDOT:

yields are 11, 14 and 14%, respectively. Thus, the quantum PSS (100 nm) anode and a thermally evaporated aluminum

yields are greatly enhanced on going from fluid solution cathode (70 nm). PEDOT:PSS was used to smooth the ITO

(Table 4) to diluted thin film and even in the device configur- surface, increasing the yield and reproducibility of working

ation with only a small amount of ionic liquid present.

devices, whereas the ionic liquid was employed to facilitate

The emission maxima of [Ir(ppy)₂(8)][PF₆] and [Ir(ppy)₂(10)][PF₆] charge injection into the devices, thereby reducing the turn-on

in ionic liquid are both 600 nm (Fig. 13b), and show only a time. The LECs using complexes [Ir(ppy)₂(N^N)][PF₆] with N^N

small blue shift compared to the solution data in Table 4. = 1, 2 or 3 were driven under a dc voltage of 4 V, whereas those

Quantum yields are again significantly enhanced (15% for using complexes [Ir(ppy)₂(N^N)][PF₆] with N^N = 8 and 10

[Ir(ppy)₂(8)][PF₆] and 19% for [Ir(ppy)₂(10)][PF₆]).

were operated using a pulsed current driving method. The

8100 | Dalton Trans., 2013, 42, 8086–8103

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Table 5 Performance of LEC devices, either (a) driven using a constant voltage

mode (4V) for [Ir(ppy)₂(N^N)][PF₆] with N^N = 1, 2 or 3 or (b) using a pulsed

current mode (average current density 50 A m⁻², 1000 Hz, 50% duty cycle,

block wave) for [Ir(ppy)₂(N^N)][PF₆] with N^N = 8 or 10

Power

[Ir(ppy)₂-

(N^N)]⁺

L_max

/

Eﬃcacy/ eﬃcency/lm

t_on/h cd m⁻²t_1/2/h cd A⁻¹

W⁻¹

EQE/%

[Ir(ppy)₂(1)]⁺33

[Ir(ppy)₂(2)]⁺24

[Ir(ppy)₂(3)]⁺28

41

86

46

61

58

1.5

0.5

0.4

0.3

1.5

1.2

1.8

0.3

0.2

0.9

1.2

1.7

335^a2.7

125^a2.4

130^a3.7

[Ir(ppy)₂(8)]⁺

2.4 114

[Ir(ppy)₂(10)]⁺3.3 182

^aValue from extrapolation.

The device data show clearly that the bulky ligands used for

[Ir(ppy)₂(8)][PF₆] and [Ir(ppy)₂(10)][PF₆] are beneficial for the

operation of LECs. In view of the PL quantum yields observed

in thin film configuration and assuming a light outcoupling

eﬃciency of 20% for these planar devices, maximum EQEs for

the LECs using complex [Ir(ppy)₂(8)][PF₆] and [Ir(ppy)₂(10)][PF₆]

of 3 and 3.8% are expected. Hence, the observed values

are quite good, especially taking into account that the exciton

to photon conversion eﬃciency is decreased under influence

of an electric field.

Conclusions

We have described the preparation and characterization of a

series of [Ir(ppy)₂(N^N)][PF₆] complexes in which each N^N

ligand contains a bpy-core and is functionalized in the 6- or

5-positions. The substituents are structurally and electronically

very varied, but most contain an aromatic ring that is designed

to permit the formation of an intra-cation π-stacking inter-

action with one of the [ppy]⁻domains. Single crystal X-ray

diﬀraction studies of [Ir(ppy)₂(N^N)][PF₆] containing 1, 9, 10

and 12 confirm the presence of this interaction, although the

presence of the N-methyl substituent in 1 results in a signifi-

cantly distorted octahedral coordination environment for the

Fig. 14 (a) Luminance and current density (inset) versus time for ITO/PEDOT:

PSS/[Ir(ppy)₂(N^N)][PF₆]/IL(4 : 1)/Al LEC: (a) N^N = 1–3 with devices biased by

4V DC; (b) N^N = 8 and 10 with devices biased by a pulsed current of 50 A m⁻²

(1000 Hz, 50% duty cycle, block wave).

luminance and current/average voltage characteristics versus

operation time are shown in Fig. 14.

1

Very fast turn of the luminance is observed accompanied by

a rapid decrease of the average voltage applied. This is evi-

dence of the particular operation mechanism of the LECs.^42,43

The ions present in the light-emitting film migrate to the

respective electrodes under the influence of the applied bias,

and as a result decrease the barrier for electron injection.

Under current driving this leads to a strong reduction of the

voltage to sustain the pre-set current density. The light emis-

sion turns-on very rapidly as well, even though the maximum

emission is only observed after a few hours. When compared

with voltage driving the turn-on of luminance is much faster.

Once the maximum luminance is obtained it only gradually

decreases with time leading to quite good lifetimes. More

importantly the eﬃciency is also much more stable with time

and remains almost constant over the lifetime of the devices. A

summary of the most important device parameters is given in

Table 5.

iridium(^III) centre. In solution, H NMR spectroscopy has been

used to investigate the dynamic behaviour of the complexes.

The preparation and characterization of a representative

[Ir(ppy)₂(N^O)]⁺complex (N^O = 12) has also been described. In

degassed MeCN and at room temperature, the [Ir(ppy)₂(N^N)][PF₆]

em

max

complexes are all orange emitters with λ

in the range

575 to 608 nm; quantum yields are very low. [Ir(ppy)₂(12)][PF₆]

is non-emissive. The variation in the oxidation potential of the

iridium ion compared to literature data for [Ir(ppy)₂(6-Phbpy)]-

[PF₆] suggests that the structural influence of the 6-substituent

on the electronic structure of the complex is the dominant

factor; there is no simple trend that can be associated with

electron-withdrawing or releasing nature of the substituents

on the N^N domain. The complexes with the bulky N^N

ligands 8 and 10 lead to very interesting LECs that show quite

good performances. In view of the limited photolumine-

scence eﬃciency, very good external quantum eﬃciencies are

Dalton Trans., 2013, 42, 8086–8103 | 8101

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Acknowledgements

We thank the European Research Council (Advanced Grant

267816 LiLo), the Swiss National Science Foundation, and the

University of Basel for financial support, the Spanish Ministry

of Economy and Competitiveness (MINECO) (MAT2011-24594,

CTQ2009-08790 and Consolider-Ingenio CSD2007-00010), the

Generalitat Valenciana (PROMETEO/2012/053), and the European

Union (CELLO, STRP 248043; https://www.cello-project.eu/) for

financial support. A.P. also acknowledges MINECO for an FPI

grant. Nik Hostettler is thanked for recording low temperature

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Dalton Trans., 2013, 42, 8086–8103 | 8103

Article Doi

Solution, structural and photophysical aspects of substituent effects in the N^N ligand in [Ir(C^N)2(N^N)]+ complexes

DOI: 10.1039/c3dt50492a

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