Cationic heteroleptic cyclometalated iridiumIII complexes containing phenyl-triazole and triazole-pyridine clicked ligands

Article abstract of DOI:10.3390/molecules15032039

Novel heteroleptic iridium complexes containing the 1-substituted-4-phenyl- 1H-1,2,3-triazole (phtl) cyclometalating ligand have been synthesized. The 3+2 Huisgen dipolar cycloaddition method ('click' chemistry) was utilized to prepare a class of bidentat

Full text of DOI:10.3390/molecules15032039

Molecules 2010, 15, 2039-2059; doi:10.3390/molecules15032039
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molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Cationic Heteroleptic Cyclometalated IridiumIII Complexes
Containing Phenyl-Triazole and Triazole-Pyridine Clicked
Ligands
Marco Felici 1, Pablo Contreras-Carballada 2, Jan M. M. Smits 3, Roeland J. M. Nolte 1,
René M. Williams 2, Luisa De Cola 4 and Martin C. Feiters 1,*
1
Department of Organic Chemistry, Institute for Molecules and Materials, Faculty of Science,
Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands;
E-Mails: m.felici@science.ru.nl (M.F.); r.nolte@science.ru.nl (R.J.M.N.)
2
Van`t Hoff Institute for Molecular Sciences, Molecular Photonic Materials, Nieuwe Achtergracht
129, 1018 WS Amsterdam, The Netherlands; E-Mails: P.ContrerasCarballada@uva.nl (P.C.-C.);
R.M.Williams@uva.nl (R.M.W.)
3
Solid State Chemistry, Institute for Molecules and Materials, Faculty of Science, Radboud
University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands;
E-Mail: J.Smits@science.ru.nl (J.M.M.S.)
4
Physikalisches Institut, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10,
48149 Münster, Germany; E-Mail: decola@uni-muenster.de (L.D.C.)
* Author to whom correspondence should be addressed; E-Mail: m.feiters@science.ru.nl;
Tel.: +31 (0)24 36 52016, Fax: (+31) (0)24 36 52929.
Received: 8 February 2010; in revised form: 8 March 2010 / Accepted: 18 March 2010 /
Published: 23 March 2010
Abstract: Novel heteroleptic iridium complexes containing the 1-substituted-4-phenyl-1H-
1,2,3-triazole (phtl) cyclometalating ligand have been synthesized. The 3+2 Huisgen
dipolar cycloaddition method (‘click’ chemistry) was utilized to prepare a class of
bidentate ligands (phtl) bearing different substituents on the triazole moiety. By using
various ligands (phtl-R1 and pytl-R2) (R1=adamantane, methyl and R2=adamantane,
methyl, β-cyclodextrin, ursodeoxycholic acid), we prepared a small library of new
luminescent ionic iridium complexes [Ir(phtr-R1)2(pytl-R2)]Cl and report on their
photophysical properties. The flexibility of the clicking approach allows a straightforward

Molecules 2010, 15
control on the chemical-physical properties of the complexes by varying the nature of the
2040
substituent on the ligand.
Keywords: click chemistry; phenyl-triazole; pyridine-triazole; iridium; luminescence
1. Introduction
The photoluminescence of organometallic complexes has attracted much interest since it can be
utilized for a variety of applications such as oxygen sensors, biological probes and phosphorescent
dopants in optoelectronic devices [1,2]. In particular, cyclometalating complexes of iridiumIII have
received great attention because of the high tunability of their emission in terms of color and
efficiency. This has been achieved by screening a large variety of cyclometalating and ancillary
ligands, often bearing functional groups with electron withdrawing or releasing properties. While
much has been done on the investigation of the photophysical properties of iridiumIII complexes, little
attention has been focused on controlling other properties like solubility and polarity. The increasing
number of applications of such compounds has made this aspect more appealing; it is indeed
important, for example, to have photo-active materials which are water soluble in order to incorporate
them in electrochemiluminescence (ECL) devices, or apolar with high affinity for hydrophobic
matrices or with ‘sticky’ tails able to selectively recognize guests on modified surfaces [3]. The best
approach to obtain complexes with designed physico-chemical properties is through the
functionalization of ligands with selected substituents. Unfortunately, most of the ligands are difficult
to prepare or their synthesis requires a large number of steps [4–7]. Their functionalization is not
always trivial as it usually implies aromatic substitution reactions (on the phenyl or pyridyl moities)
and coupling reactions. This all leads to an increase in the cost of the material itself and to a limited
applicability. We now report on an exploration of the application of the Huisgen Cu-catalyzed [3+2]
cycloaddition as an efficient and flexible means to prepare a class of bidentate cyclometalated ligands,
1-substituted-4-phenyl-1H-1,2,3-triazole (phtl) (1 and 2, Scheme 1) [8]; we have also investigated
whether stable luminescent heteroleptic iridium complexes could be formed (Scheme 1), and what
properties emerge from the use of such a 1,2,3-triazole-containing chelator. The substituents we used
to functionalize pytl [2-(1-substituted-1H-1,2,3-triazol-4-yl)pyridine] and phtl [i.e., βCD, adamantanes,
ursodeoxycholic acid (UDC) derivative and methyl] are examples of moieties provided with different
chemico-physical properties. Decoration of a metal complex with these residues does not influence the
electronic properties of the molecule and thus it does not affect directly its correlated luminescent
properties. However, it can add other properties to the metal complex providing us with multi-
functional materials. We prepared a small library of phosphorescent complexes bearing either host
(βCD) or guest molecules (adamantane, UDC-derivative). Cyclodextrins are well-known cyclic
oligosaccharides that can form inclusion complexes in aqueous solution with a variety of hydrophobic
substrates, such as adamantane derivatives, and have been widely applied as supramolecular building
blocks in various areas [9–14], including photoactivated electron transfer processes [6,15–18]. With
βCD attached to [Ir(1)2(pytl-βCD)]Cl the phosphorescent dye can be immobilized on guest-appended

Molecules 2010, 15
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polymeric membranes, which are used as responsive materials for oxygen sensors. βCD can also act as
second sphere ligand, enhancing the photophysical properties of [Ir(1)2(pytl-βCD)]Cl [19]. The
presence of adamantanes in [Ir(2)2(pytl-ada)]Cl and [Ir(1)(2)(pytl-ada)]Cl allows the supramolecular
decoration with iridium complexes of the surface of vesicles and nanoparticles covered with
cyclodextrins [20]. Particularly interesting is the complex [Ir(1)2(pytl-DC)]Cl where a UDC derivative
instead of adamantane was used as a host. Native UDC is a amphiphilic molecule which has high
affinity for βCD [21] as well as for bilayer membranes [22–25]. As we show here, UDC can be easily
functionalized through the azido group (Scheme 3). Its affinity for membranes, combined with the
sensitivity of polyamine iridiumIII complexes to the polarity of their environment, provides us with an
interesting luminescent polarity probe for the study of the dynamics of natural and artificial
membranes [4,5,26]. Besides the supramolecular aspects, the nature of the substituents on the complex
[Ir(phtl-R1)2(pytl-R2)]Cl strongly affects other properties like solubility. This can be tuned by changing
the hydrophilicity of the ligands: the simplest complex of the series, the fully methylated [Ir(1)2(pytl-
Me)]Cl, displays a poor solubility in water which is dramatically increased in [Ir(1)2(pytl-βCD)]Cl by
the introduction of one per-methylated βCD.
Scheme 1. Structures of 1 and 2 and their heteroleptic iridium complexes.

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2. Results and Discussion
2.1. Synthesis of phtl and pytl ligands and their iridium complexes
The Huisgen cycloaddition, also known as ‘click reaction’ [27], involves the formation of 1,2,3-
triazole rings by coupling terminal alkynes and azides. It can be used to prepare the phtl ligand in one
step, by reacting ethynylbenzene with an azide-containing molecule. The known high efficiency of this
reaction, combined with its tolerance to other functional groups [27], allows the introduction of the
phtl (and pytl) ligand on many different substrates (i.e. methyl, adamantane, bile acid) [19,28,29],
requiring only the presence of at least one azido group on the molecule of interest. Therefore, this
approach makes a large library of cyclometalating ligands readily accessible. The ligands 1 and 2 were
prepared by reacting azidomethane and 1-azidoadamantane with ethynylbenzene for two hours in
deoxygenated THF, in the presence of CuBr and pentamethyldiethylenetriamine (PMDTA). The
products were isolated in 43% and 76% yield, respectively. The click reaction was used to prepare also
the ancillary ligands pytl-R, by reacting 2-ethynylpyridine with the corresponding azido-appended
derivatives in identical conditions (Scheme 2) as reported previously [19]. In addition to full
characterization by NMR and mass spectrometry, the crystal structures of the ligands 1 and 2 were
obtained by single crystal X-ray diffraction (Table S1, Figure S1 and S2).
Scheme 2. Synthesis and structures of the ligands phtl-R and pytl-R.
The preparation of the ligand 3β-(4'-(pyridin-6'-yl)-1'H-1',2',3'-triazol-1'-yl)-7β-hydroxy-5β-cholan-
24-oic acid (pytl-DC) required the synthesis of 3β-azido-7β-hydroxy-5β-cholan-24-oic acid methyl

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ester 7 (Scheme 3). This was achieved by adapting the procedure described in the literature for the
azidation of cholic acid [30]. The carboxylic group was initially protected as methyl ester to avoid
undesired reactions and the hydroxyl group converted into a better leaving group by tosylation. The
latter step produces a mixture of tosylated derivatives that was further used without purification. The
substitution of the tosylate by sodium azide accomplished a mixture of 6 and 7 separated by
chromatography. Both compounds are very interesting for bio- and supramolecular applications. Due
to the ability of the azido group to undergo different chemical modifications (click reaction, reduction
to amino group), they can be appended to a wide range of substrates.
Scheme 3. Synthesis of the cholic acid derivatives 6-8.
In addition to full characterization by NMR spectroscopy and mass spectrometry, the crystal
structures of the carboxylic acids derivatives pytl-DC, 6a and 7a (Figure 1 and Table S2) were
determined by single crystal X-Ray diffraction. It should be noted that the nucleophilic substitution of
the tosyl group occurred with a bimolecular (SN2) mechanism resulting in the inverted stereochemistry
of the carbon atom. This was proved by the crystal structures of 6a and 7a which clearly show that the
azide is in an axial position (Figure 1). This aspect is particularly important in the case of 7a because a
derivative with a molecular rod-like shape results when the pytl moiety is attached (Figure 1). We note
that, due to the inversion at the carbons 3 and 7 in ursodeoxycholic acid, 6a and 7a have in fact the
configurations of chenodeoxycholic and isoursodeoxycholic acid, respectively, according to accepted
deoxycholic acid nomenclature [31].
It is interesting to notice that the clicking approach allows the functionalization of phtl and pytl
with substituents which display very different molecular complexity. We explored here the range from
a simple methyl group to deoxycholic acid, which has a four-ring steroidal structure with two hydroxyl
groups and one carboxylic acid functionality. The efficiency and high flexibility of such an approach
provides a powerful tool for the preparation of large libraries of bidentate ligands.

Molecules 2010, 15
Figure 1. Crystal structures of pytl-DC, 6a and 7a. Gray, carbon; blue, nitrogen; red,
2044
oxygen. The thermal ellipsoids for the image represent 25% probability limit. Hydrogen
atoms are omitted for clarity.
The synthesis of an iridiumIII complex is usually accomplished through a two-step process: the
Nonoyama reaction that yields a chloride-bridged dinuclear iridium species [32] followed by the
substitution of the chlorides with an ancillary ligand (Scheme 4). The iridiumIII dimers [(1)2Ir-μ-Cl]2
and [(2)2Ir-μ-Cl]2 were prepared by reacting 1 or 2 with IrCl3, in a mixture water/2-methoxyethanol
1/3 (v/v) at 97 ºC. The compound [(1)(2)Ir-μ-Cl]2 was prepared by using an equimolar mixture of 1
and 2, which afforded a mixture of dinuclear species difficult to separate and further reacted without
purification. All the complexes were obtained by reacting the corresponding iridium dimer with a
bidentate pytl ligand (Scheme 4) under mild conditions, in a chloroform/methanol 3:1 (v/v) mixture at
45 °C. After 3 hours the formation on TLC of only one new spot was observed, characterized (in
contrast to the starting compound) by a bright luminescence under UV-Vis lamp at 366 nm. All the
complexes, except for [Ir(1)(2)(pytl-ada)]Cl, were purified by silica column chromatography or
preparative layer chromatography (PLC). In the case of [Ir(1)(2)(pytl-ada)]Cl, the non-selective
synthesis resulted in a mixture of different iridium species which could not be isolated by traditional
silica chromatography. We overcame this problem by using an HPLC apparatus equipped with a semi-
preparative reversed-phase column. The characterization was done by means of NMR spectroscopy
and high-resolution mass spectrometry. Compound [Ir(1)(2)(pytl-ada)]Cl is an example of
cyclometalated complex where three different ligands are present: 1, 2 and pytl-ada. It was synthesized
to investigate the possibility to prepare complexes with a higher degree of functionalization. To our
knowledge complexes with these structural characteristics have not been reported to date.

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Scheme 4. Synthesis of the iridiumIII complexes.
Cyclometalated iridium complexes have an octahedral geometry. The relative spatial orientation of
the substituents around the metal center depends on whether they are attached to the cyclometalating
or the ancillary ligands. In fact, it is known that in the chloride-bridged dinuclear iridium complex
prepared with the Nonoyama reaction the cyclometalating ligands are always oriented in a trans
position with respect to each other. In particular, the two nitrogens of the phtl ligands are aligned along
a common axis together with the central iridium atom [33]. The pytl, which is inserted in the second
synthetic step, is located on the plane perpendicular to that axis. By taking advantage of the well-
established orientation of the ligands around the complex, considering that both phtl and pytl can be
prepared starting from the same azide-appended molecule, we were able with our approach to control
the location of the substituents in the iridium complex simply by clicking them to either
2-ethynylpyridine or ethynylbenzene.
2.2. Photophysical characterization
All the iridium complexes are soluble in acetonitrile and these solutions were used to measure the
absorption and emission spectra. The UV-Vis spectra of all the complexes are very similar
(Supplementary Data); we show here only the spectrum of the iridium complex [Ir(1)(2)(pytl-ada)]Cl
(Figure 2). The intense absorption bands present in the UV region (190–240 nm) are assigned to
1(π-π*) transition of both phtl and pytl ligands (Figure 2). The shoulders appearing in the range
between 290 and 350 nm are likely to be due to weaker charge transfer (CT) transitions, being of both

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spin-allowed 1MLCT and forbidden 3MLCT nature. All complexes are luminescent in solution at room
temperature and display very similar, broad, featureless emission spectra between 410 and 650 nm
(emission of [Ir(1)(2)(pytl-ada)]Cl, Figure 2) with a maximum for the emission at 510 nm.
Figure 2. UV-Vis absorption spectrum (solid) and room temperature emission spectrum
(dotted) in acetonitrile of [Ir(1)(2)(pytl-ada)]Cl (λexc= 335 nm). 77 K emission spectrum
(dashed) in glassy butyronitrile matrix of [Ir(1)(2)(pytl-ada)]Cl (λexc= 335 nm).
According to previously published work concerning analogous cyclometalated iridiumIII complexes
[34] such a broad emission is characteristic for a metal-to-ligand-charge-transfer excited state in
which, formally speaking, an electron is transferred from the metal center to the ligand with the lowest
reduction potential. If this transfer is understood as a HOMO-LUMO transition, the HOMO would be
localized on the metal core and the LUMO orbital on the ligand. This is also consistent with the
emission quantum efficiencies from all the complexes measured in air-equilibrated solutions which
range from 0.021 to 0.052 (Table 1); in de-aerated conditions the compounds [Ir(1)2(pytl-Me)]Cl,
[Ir(2)2(pytl-ada)]Cl and [Ir(1)(2)(pytl-ada)]Cl exibit a 2-3 fold increase of the emission quantum
yields; however, for [Ir(1)2(pytl-DC)]Cl and [Ir(1)2(pytl-βCD)]Cl the increase is very large and reaches
5-fold. For [Ir(1)2(pytl-βCD)]Cl the quantum yields are remarkably high and comparable with the
value measured for [Ir(ppy)2(pytl-ada)]Cl where the cyclometalating ligands were ppy [19]. This
behaviour could be explained by the tendency of molecules like β-cyclodextrin and especially
ursodeoxycholic acid to interact (aggregate or formation of inclusion complexes) even in very dilute
solutions; this interaction could increase the emission efficiencies by reducing the non-radiative decay
promoted by vibrational modes. Organization of organometallic complexes in solution through micelle
or vesicle formation, inclusion in a cyclodextrin cavity or by other means has have been shown to
influence greatly the properties of these complexes [35]. These changes in the emissive properties of
the compounds studied are always assigned to changes in the surrounding. For example vesicle
formation with metallosurfactants leads to the observation of fast components in the excited state
decay of the individual metal complexes [36]. All these complexes undergo large hypsochromic shifts
upon cooling to 77 K (spectrum of [Ir(1)(2)(pytl-ada)]Cl, Figure 2). In a butyronitrile solid matrix the

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maxima for the emission are blue-shifted and appear at 435 nm. Such a behavior is expected for
compounds emitting from a charge transfer excited state and it is due to the impossibility for the
solvent molecules to rearrange around the excited state. The consequent lack of stabilization of the
excited state leads to a more energetic (blue-shifted) emission. The emission spectra show a series of
vibronic transitions (emission of [Ir(1)(2)(pytl-ada)]Cl, Figure 2) which are not resolved at room
temperature and which imply that a considerable ligand-centered (LC) character develops in these
species at low temperature [37].
Table 1. Luminescence lifetimes and quantum yields of emission of the complexes. For
quantum yield measurements λexc= 335 nm. For lifetime measurements λexc= 324 nm. The
solutions were measured in air equilibrated acetonitrile (air) and argon saturated (Ar) for
degassing by bubbling argon for 20-30 minutes through the solution.
Complex
[Ir(1)2(pytl-Me)]Cl
[Ir(2)2(pytl-ada)]Cl
Φ(air)
0.037
0.021
Φ(Ar)
0.097
0.048
τ (ns, air) τ (ns, Ar)
24.8
27.1
18.0
17.4
11.8 (60%)
23.6 (40%)
[Ir(1)(2)(pytl-ada)]Cl
0.024
0.071
19.7
28.3 (84%)
2.22 (16%)
34.1
[Ir(1)2(pytl-DC)]Cl
[Ir(1)2(pytl-βCD)]Cl
0.039
0.052
0.203
0.254
24
26.4
3. Conclusions
In conclusion, we report the preparation and the photophysical properties of new highly
luminescent heteroleptic iridiumIII complexes. Click chemistry was used as an efficient tool to
introduce on the phtl and pytl ligands functional groups provided with various level of complexity.
The flexibility of such approach provides access to a large library of clicked ligands and therefore to
multi-functional iridiumIII complexes with tunable chemico-physical properties. In particular the
complex [Ir(1)2(pytl-DC)]Cl is a promising luminescent polarity probe for the study of membrane
dynamics; [Ir(1)2(pytl-βCD)]Cl and [Ir(2)2(pytl-ada)]Cl are interesting building blocks for
supramolecular systems. Here we also report the first synthesis of the 3β-azido-7β-hydroxy-5β-cholan-
24-oic acid (7a) and the isomer 3α-hydroxy-7α-azido-5β-cholan-24-oic (6a), both interesting
intermediates for both bio- and supramolecular systems.
4. Experimental
4.1. General
THF was purified by distillation under nitrogen from sodium/benzophenone and dry DMF was
purchased from Fluka. All other chemicals were purchased from Aldrich, Fluka or Acros and used as
received. Analytical thin layer chromatography (TLC) was performed on Merck precoated silica gel 60
F-254 plates (layer thickness 0.25 mm) and the compounds visualized by ultraviolet (UV) irradiation
at λ = 254 nm and/or λ = 366 nm and by staining with phosphomolybdic acid reagent or KMnO4.
Preparative layer chromatography (PLC) was performed on Merck precoated silica gel 60 F-254 plates

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(layer thickness 1 mm, concentrating zone 20 × 4 cm) and the compounds visualized by ultraviolet
(UV) irradiation at λ = 254 nm and/or λ = 366 nm. Purifications by silica gel chromatography were
performed using Acros (0.035 – 0.070 mm, pore diameter ca. 6 nm) silica gel. All click reactions were
performed in oxygen-free atmosphere of N2 using Schlenk conditions and solvents dried and distilled
according to standard laboratory procedures.
Nuclear magnetic resonance (NMR): 1H-NMR spectra were recorded, at 25 °C, on a Varian Inova 400
13
or a Bruker DMX-300 machines operating at 400 and 300 MHz, respectively. C-NMR spectra were
1
recorded on a Bruker DMX-300 machine operating at 75 MHz. H-NMR chemical shifts (δ) are
reported in parts per million (ppm) relative to a residual proton peak of the solvent, δ = 3.31 for
CD3OD, δ = 7.26 for CDCl3 and δ = 2.50 for DMSO. Multiplicities are reported as: s (singlet), d
(doublet), t (triplet), q (quartet), dd (doublet of doublets), ddd (doublet of doublet of doublets) or m
(multiplet). Broad peaks are indicated by b. Coupling constants are reported as a J value in Hertz (Hz).
The number of protons (n) for a given resonance is indicated as nH, and is based on spectral
13
integration values. C-NMR chemical shifts (δ) are reported in ppm relative to a carbon peak of the
solvent, δ = 49.0 for CD3OD, δ = 77 for CDCl3 and δ = 40 for DMSO. The signals of the protons on
hydroxyl and carboxylic groups could not be observed due to the fast exchange with traces of water
present in the deuterated solvents. The resolution of 13C spectra was increased when necessary by
performing an exponential apodization of the FID.
Mass spectrometry (MS): All the mass analysis were performed by using electrospray techniques
(ESI). High-Resolution mass spectrometry measurements were performed on a JEOL AccuTOF
instrument by using water, acetonitrile or methanol as solvents. Standard mass spectrometry
measurements were performed on a FINNIGAN LCQ Advantage Max by using water, acetonitrile or
methanol as solvents.
High-performance liquid chromatography (HPLC): High-performance liquid chromatography (HPLC)
was carried out on a Shimadzu LC-20AT HPLC system equipped with a UV-Vis detector SPD-10AV
and a fraction collector. Columns were purchased from Dr. Maisch GmbH. The compounds were
purified on mg scale using a semipreparative reversed-phase HPLC column. A 2 mL solution was
injected in a column ReproSil 100 C8, 5 μ (250X10 mm) operating at 30 °C. The detection
wavelengths were fixed at 254 and 215 nm. A gradient of H2O and acetonitrile both containing either
0.1% v/v HCl or TFA was used as mobile phase, with a flow rate of 4 mL min-1. HCl was used to
ensure that the chloride was the only counterion of the isolated compounds. In all cases the samples
were prepared by dissolving the compound in mixtures H2O/acetonitrile 95/5 or 1/1 v/v, and filtered
on a nylon syringe filter (0.2 μm).
X-ray crystallography: Single crystals of 1 (phtl-Me) and 2 (phtl-ada) were grown by slow evaporation
of a solution of compounds 1 and 2 in CHCl3/heptane. Single crystals of pytl-DC were grown by slow
evaporation of a solution of pytl-DC in CH3OH. Single crystals of 6a and 7a were grown by slow
evaporation of a slightly acidic solution of 6a and 7a in H2O/acetonitrile. The crystal data and
summaries of the data collection and structure refinement are given in Table S1 for compounds 1 and
2, and Table S2 for 6a, 7a, and pytl-DC; selected distances and bond angles as well as atomic

Molecules 2010, 15
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coordinates and equivalent isotropic displacement parameters for the non-hydrogen atoms are also
given in the Supplementary Information. All measurements were performed at -65 °C. The structures
of 1, 6a, and 7a were solved by the program SHELXS [38], those of 2 and pytl-DC by the program
CRUNCH [39]. All non-hydrogen atoms were refined with anisotropic temperature factors. The
hydrogen atoms were placed at calculated positions, and refined isotropically in riding mode.
Crystallographic data (excluding structure factors) for the structures reported in this paper have been
deposited with the Cambridge Crystallographic Data Centre as supplementary publication CCDC-
1003/, deposition codes: 1 (FELIC3), 757888; 2 (MFR130), 757886; 6a (MFR99), 757884; 7a
(MFR99B), 757885; pytl-DC (PYTLUD), 757887. Copies of available material can be obtained, free
of charge, on application to the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, (fax: +44-
(0) 1223-336033 or e-mail:teched@chemcrys.cam.ac.uk).
Emission and UV-vis: Electronic absorption spectra were recorded in a quartz cuvette (1 cm, Hellma)
on Hewlett-Packard 8543 diode array spectrometer (range 190 nm-1100 nm). Steady state fluorescence
spectra were recorded using a Spex 1681 fluorimeter, equipped with a Xe arc light source, a
Hamamatsu R928 photomultiplier tube detector and double excitation and emission monochromator.
Emission spectra were corrected for source intensity and detector response by standard correction
curves, unless otherwise noted. Luminescence quantum yields (Φem) were measured in optically dilute
solutions (O.D. < 0.1 at excitation wavelength), using [Ru(bpy)3]Cl2 in aerated and deoxygenated H2O
(Φem, air = 0.028; Φem, deox = 0.042) or diphenylanthracene in aerated and deoxygenated cyclohexane
(Φem, air = 0.77; Φem, deox = 0.91) as references.
Lifetimes of excited states were determined using a coherent Infinity Nd:YAG-XPO laser (2 ns
pulses fwhm) and a Hamamatsu C5680-21 streak camera equipped with Hamamatsu M5677 low speed
single sweep unit. Streak cameras are high-speed light detectors, which enable detection of the
fluorescence as a function of the spectral and the time evolution simultaneously.
4.2. Synthesis and characterization
1-Methyl-4-phenyl-1H-1,2,3-triazole (1): Dry DMF was deoxygenated prior to use by performing three
freeze-pump-thaw cycles. A two-necked round bottom flask was carefully dried with flame, under N2
flow. In the cooled flask, NaN3 (198 mg, 3 mmol) was added together with deoxygenated dry DMF
(40 mL). CH3I (0.3 mL, 4.8 mmol) was added dropwise and the solution was stirred in the dark
overnight. The methyl-azide formed is a highly explosive intermediate and therefore it was not isolated
[40]. The ‘clicking’ reagents were subsequently added to the reaction mixture and a large excess of
ethynylbenzene (658.9 μL, 6 mmol) and of catalyst were used to ensure the complete consumption of
the methyl-azide. A solution of CuBr (430 mg, 3 mmol) and PMDTA (0.67 mL, 3.2 mmol) was
prepared by dissolving both reagents in oxygen-free dry DMF (10 mL), bubbling nitrogen through the
solution for 20 min to prevent oxidation of Cu(I). When the CuPMDTA complex dissolved, an aliquot
of the solution (5 mL), together with compound ethynylbenzene (0.45 mL, 4.5 mmol) were added to
the flask. The resulting mixture was stirred in the dark at room temperature under a nitrogen
atmosphere for 24 hours. The reaction was followed by TLC (eluent: Et2O). After removal of the
solvent in vacuo (CAUTION: this solution may still contain methyl azide in case the conversion with
phenylacetylene was not 100 %) the solid obtained was purified by column chromatography

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(Et2O/Heptane 50/50 followed by Et2O/ethyl acetate 90/10). Product 1 was obtained as a white solid
(208 mg, overall yield 43%). Crystals were grown by slow evaporation of a solution of 1 in
CHCl3/heptane. The structure was further confirmed by X-ray single crystal diffraction. 1H-NMR (300
MHz, CDCl3): δ ppm 7.86–7.78 (m, 2H), 7.73 (s, 1H), 7.47–7.38 (m, 2H), 7.37–7.29 (m, 1H), 4.14 (s,
3H); 13C-NMR (75 MHz, CDCl3): δ ppm 148.0, 130.6, 128.8, 128.1, 125.7, 120.5, 36.7; HRMS (ES+,
CHCl3/CH3OH): m/z calcd for C9H10N3: 160.08747; found: 160.08768 [M+H]+.
1-Adamantyl-4-phenyl-1H-1,2,3-triazole (2): Distilled THF was bubbled with N2 for 1h prior to use in
order to remove the oxygen. Ethynylbenzene (185.6 μL, 1.69 mmol) and 1-adamantylazide (300 mg,
1.69 mmol) were added under nitrogen atmosphere in a Schlenk tube and dissolved in deoxygenated
THF (15 mL). A solution of CuBr (242.4 mg, 1.69 mmol) and PMDTA (365.8 μL, 1.75 mmol) was
prepared by dissolving both reagents in deoxygenated THF (15 mL) and bubbling nitrogen through the
solution for 20 min to prevent oxidation of Cu(I). When the CuPMDTA complex dissolved, the
solution became slightly green, and an aliquot of it (3 mL) was added to the Schlenk tube. The
resulting mixture was stirred in the dark, at room temperature under a nitrogen atmosphere for
2.5 hours. The reaction was followed by TLC (eluent: Et2O/heptane 80/20). No workup was done and
after removal of the solvent in vacuo, the blue-green solid obtained was directly purified by column
chromatography (Et2O/heptane 30/70). Product 2 was obtained as a white solid (358.8 mg, 76%).
Crystals were grown by slow evaporation of a solution of 2 in CHCl3/heptane. The structure was
1
further confirmed by X-ray single crystal diffraction. H-NMR (300 MHz, CDCl3): δ ppm 7.86–7.81
(m, 2H), 7.82 (s, 1H), 7.45–7.38 (m, 2H), 7.34–7.28 (m, 1H), 2.32–2.26 (m, 9H), 1.85–1.79 (m, 6H);
13C-NMR (75 MHz, CDCl3): δ ppm 137.8, 131.1, 128.8, 127.8, 125.6, 118.2, 59.6, 43.0, 35.9, 29.5;
HRMS (ES+, CHCl3/CH3OH): m/z calcd for C18H22N3: 280.18137; found: 280.18165 [M+H]+.
3α,7β-Dihydroxy-5β-cholan-24-oic acid methyl ester (3): Ursodeoxycholic acid (UDC, 277.1 mg,
0.71 mmol) was dissolved in methanol (10 mL). A catalytic amount of p-toluensolfonic acid was
added and the solution was stirred under reflux for 2.5 hours. The reaction was followed by TLC
(eluent: ethyl acetate/heptane 80/20). After removal of the solvent in vacuo, the crude product was
dissolved in CHCl3 and washed with aqueous solution of K2CO3 (1M, 1 × 100 mL). The organic phase
was dried over Na2SO4 anhydrous and the solvent removed under reduced pressure to yield 3 as a
1
white solid (282.3 mg, 98%). H-NMR (300 MHz, CDCl3): δ ppm 3.64 (s, 3H), 3.61–3.48 (m, 2H),
2.41–2.10 (m, 2H), 2.01–0.96 (m, 24H), 0.92 (s, 3H), 0.90 (d, J = 6.4 Hz, 3H), 0.65 (s, 3H); 13C-NMR
(75 MHz, CDCl3): δ ppm 174.7, 71.3, 71.2, 55.7, 54.9, 51.4, 43.69, 43.66, 42.4, 40.1, 39.2, 37.3, 36.9,
35.2, 34.9, 34.0, 31.01, 30.96, 30.3, 28.5, 26.8, 23.3, 21.1, 18.3, 12.1.
Mixture of 3α-(4-Methylphenyl)sulfonyloxy-7β-hydroxy-5β-cholan-24-oic acid methyl ester (4) and
3α-hydroxy-7β-(4-Methylphenyl)sulfonyloxy-5β-cholan-24-oic acid methyl ester (5): Compound 3
(254.5 mg, 0.62 mmol) was added under nitrogen atmosphere in a Schlenk tube and dissolved in dry
pyridine (5 mL). Tosyl chloride (178.4 mg, 0.94 mmol) was added and the solution was heated to
50 ºC under nitrogen for 4 hours. The reaction was followed by TLC (eluent: ethyl acetate/heptane
50/50). After removal of the solvent in vacuo, the crude product was dissolved in ethyl acetate, washed
with HCl (1N, 3 × 80 mL) and water (1 × 80 mL). The organic phase was dried over Na2SO4

Molecules 2010, 15
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anhydrous and the solvent removed under reduced pressure. The crude product (348.4 mg) was further
reacted without purification.
3α-Hydroxy-7α-azido-5β-cholan-24-oic acid methyl ester (6) and 3β-azido-7β-hydroxy-5β-cholan-24-
oic acid methyl ester (7): The crude material containing compounds 4+5 (348.4 mg) was added under
nitrogen atmosphere in a Schlenk tube and dissolved in dry DMF (15 mL). Sodium azide (201.5 mg,
3.1 mmol) was added and the solution was heated to 60 ºC under nitrogen for 20 hours. The reaction
was followed by TLC (eluent: ethyl acetate/heptane 50/50). After removal of most of the solvent in
vacuo, the crude material was dissolved in ethyl acetate and washed with water (2 × 80 mL). The
organic phase was dried over Na2SO4 anhydrous and the solvent removed under reduced pressure. The
crude material was purified by column chromatography (eluent: ethyl acetate/heptane 15/85). Product
6 was obtained as a slightly yellow viscous oil (48.2 mg, overall yield = 18%). Product 7 was obtained
as a slightly yellow viscous oil (72.8 mg, overall yield = 27.2%).
6: 1H-NMR (300 MHz, CDCl3): δ ppm 3.73–3.68 (m, 1H), 3.66 (s, 3H), 3.55–3.43 (m, 1H), 2.43–0.95
13
(m, 26H), 0.92 (d, J = 6.1 Hz, 3H), 0.91 (s, 3H), 0.63 (s, 3H); C-NMR (75 MHz, CDCl3): δ ppm
174.7, 71.8, 60.5, 55.6, 51.5, 51.1, 42.6, 41.0, 39.3, 38.3, 38.2, 35.3, 35.2, 34.9, 33.7, 31.0, 30.9, 30.6,
30.4, 28.0, 23.3, 22.9, 20.4, 18.3, 11.7.
7: 1H-NMR (300 MHz, CDCl3): δ ppm 3.93–3.88 (m, 1H), 3.66 (s, 3H), 3.59–3.46 (m, 1H), 2.41–2.15
(m, 2H), 2.04–0.99 (m, 24H), 0.97 (s, 3H), 0.92 (d, J = 6.4 Hz, 3H), 0.67 (s, 3H); 13C-NMR (75 MHz,
CDCl3): δ ppm 174.6, 71.3, 58.3, 55.8, 54.9, 51.5, 43.7, 43.6, 40.1, 38.9, 37.8, 36.3, 35.2, 34.4, 31.2,
31.01, 30.98, 30.3, 28.5, 26.8, 24.5, 23.7, 21.3, 18.3, 12.1.
3α-Hydroxy-7α-azido-5β-cholan-24-oic acid (6a) and 3β-azido-7β-hydroxy-5β-cholan-24-oic acid
(7a): A solution of NaOH was prepared by adding an aqueous solution of NaOH (2 N, 2 mL) into
CH3OH (7 mL). 6a (20 mg, 0.046 mmol) or 7a (20 mg, 0.046 mmol) were dissolved in this solution
and the resulting mixture was stirred at room temperature overnight. The reaction was followed by
TLC (eluent: ethyl acetate). While cooling the reaction in ice bath, HCl (4 N) was added until pH = 7.
After removal of the solvent in vacuo, the crude material obtained was purified by column
chromatography (eluent: ethyl acetate). Product 6a was obtained as a white solid (18.6 mg, 97%).
Product 7a was obtained as a white solid (19 mg, 99%). Single crystals of 6a and 7a were grown by
slow evaporation of their slightly acidic solution in H2O/acetonitrile. The structures were further
confirmed by X-ray single crystal diffraction. Alternatively, compounds 6a and 7a could be isolated
from the crude mixture by semipreparative HPLC equipped with a reversed-phase column. The mobile
phase was a gradient of H2O and acetonitrile (30% to 0% v/v of H2O in 35 min) both containing 0.1%
v/v TFA, with a flow rate of 4 mL min-1.
1
6a: H-NMR (300 MHz, CDCl3): δ ppm 3.73–3.68 (m, 1H), 3.56–3.44 (m, 1H), 2.46–0.95 (m, 26H),
13
0.95–0.90 (m, 6H), 0.64 (s, 3H); C-NMR (75 MHz, CDCl3): δ ppm 179.0, 71.8, 60.4, 55.6, 51.1,
42.6, 41.0, 39.3, 38.3, 38.1, 35.3, 35.2, 34.9, 33.7, 30.8, 30.7, 30.6, 30.4, 28.0, 23.6, 22.9, 20.5, 18.2,
11.8.

Molecules 2010, 15
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1
7a: H-NMR (300 MHz, CDCl3): δ ppm 3.93–3.89 (m, 1H), 3.57–3.45 (m, 1H), 2.45–2.22 (m, 2H),
2.04–1.0 (m, 24H), 0.98 (s, 3H), 0.94 (d, J = 6.4 Hz, 3H), 0.69 (s, 3H); 13C-NMR (75 MHz, CDCl3): δ
ppm 178.8, 71.4, 58.3, 55.8, 54.9, 43.8, 43.6, 40.1, 38.9, 37.9, 36.3, 35.2, 34.5, 31.3, 30.8, 30.3, 29.7,
28.6, 26.8, 24.6, 23.8, 21.4, 18.4, 12.1.
3β-(4'-(Pyridin-6'-yl)-1'H-1',2',3'-triazol-1'-yl)-7β-hydroxy-5β-cholan-24-oic acid methyl ester (8)
(Scheme 5): Distilled THF was bubbled with N2 for 1 hour prior to use in order to remove the oxygen.
2-Ethynylpyridine (58.6 μL, 0.58 mmol) and 7 (250 mg, 0.58 mmol) were added under nitrogen
atmosphere in a Schlenk tube and dissolved in deoxygenated THF (10 mL). A solution of CuBr
(83.2 mg, 0.58 mmol) and PMDTA (125.4 μL, 0.6 mmol) was prepared by dissolving both reagents in
deoxygenated THF (10 mL) and bubbling nitrogen through the solution for 20 min to prevent
oxidation of Cu(I). When the CuPMDTA complex dissolved, the solution became slightly green, and
an aliquot of it (4 mL) was added to the Schlenk tube. The resulting mixture was stirred in the dark, at
room temperature under a nitrogen atmosphere for 24 hours. The reaction was followed by TLC
(eluent: ethyl acetate). After removal of the solvent in vacuo, the blue-green solid obtained was
directly purified by column chromatography (eluent: ethyl acetate/heptane 50/50 followed by ethyl
acetate/heptane 60/40). Product 8 was obtained as a white solid (303.9 mg, 98%). 1H-NMR (400 MHz,
CDCl3): δ ppm 8.57 (ddd, J = 4.9, 1.7, 0.9 Hz, 1H), 8.24 (s, 1H), 8.20 (ddd, J = 8.0, 1.0, 1.0, Hz, 1H),
7.77 (ddd, J = 7.8, 7.8, 1.8 Hz, 1H), 7.22 (ddd, J = 7.6, 4.9, 1.1 Hz, 1H), 4.72–4.68 (m, 1H), 3.66 (s,
13
3H), 3.67–3.57 (m, 1H), 2.40–1.02 (m, 26H), 0.94–0.91 (m, 6H), 0.68 (s, 3H); C-NMR (75 MHz,
CDCl3): δ ppm 174.5, 150.3, 149.1, 147.6, 136.8, 122.6, 121.0, 120.1, 70.9, 56.5, 55.8, 54.8, 51.3,
43.5, 43.2, 39.9, 39.4, 37.6, 36.2, 35.1, 34.2, 30.94–30.77 (m), 30.4, 28.4, 26.7, 24.8, 23.4, 21.3, 18.2,
12.0; HRMS (ES+, CH3OH): m/z calcd for C32H46N4NaO3: 557.34676; found: 557.34578 [M+Na]+.
Scheme 5. Structure and atom labeling of 8.
3β-(4'-(Pyridin-6'-yl)-1'H-1',2',3'-triazol-1'-yl)-7β-hydroxy-5β-cholan-24-oic acid (pytl-DC) (Scheme
6): A solution of NaOH was prepared by adding an aqueous solution of NaOH (2 N, 2 mL) into
CH3OH (7 mL). 8 (55.9 mg, 0.10 mmol) was dissolved in this solution and the resulting mixture was
stirred at room temperature overnight. The reaction was followed by TLC (eluent: CH3OH/ethyl
acetate 10/90). While cooling the reaction in ice bath, HCl (4 N) was added until pH=7–8. After
removal of the solvent in vacuo, the crude material obtained was purified by column chromatography

Molecules 2010, 15
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(CH3OH/ethyl acetate 10/90). Pytl-DC was obtained as a white solid (55.6 mg, 98%). Crystals were
grown by slow evaporation of a solution of pytl-DC in CH3OH. The structure was further confirmed
by X-ray single crystal diffraction. 1H-NMR (300 MHz, DMSO-d6): δ ppm 8.67 (s, 1H), 8.59 (ddd,
J = 4.9, 1.8, 1.0 Hz, 1H), 8.05 (ddd, J = 8.0, 1.1, 1.1 Hz, 1H), 7.89 (ddd, J = 8.0, 7.8, 1.8 Hz, 1H), 7.33
(ddd, J = 7.7, 4.9, 1.1 Hz, 1H), 4.74–4.68 (m, 1H), 3.44–3.32 (m, 1H), 2.29–0.93 (m, 26H), 0.89 (d, J
= 6.4 Hz, 3H), 0.85 (s, 3H), 0.63 (s, 3H); 13C-NMR (75 MHz, DMSO-d6): δ ppm 175.8, 150.7, 149.9,
147.4, 137.6, 123.3, 122.9, 119.9, 69.8, 56.6, 56.2, 55.3, 43.5, 43.2, 40.2, 39.3, 38.1, 37.2, 35.3, 34.4,
31.6, 31.4, 31.0, 30.7, 28.6, 27.1, 24.8, 24.0, 21.6, 18.8, 12.5; HRMS (ES+, CH3OH): m/z calcd for
C31H44N4NaO3: 543.33111; found: 543.33058 [M+Na]+.
Scheme 6. Structure and atom labeling of pytl-DC.
[(1)2Ir-µ-Cl]2: A mixture 3/1 of 2-methoxyethanol/water (9 mL) was deoxygenated by bubbling
nitrogen through it for 10-15 min. The ligand 1 (91.5 mg, 0.57 mmol) and IrCl3⋅3H2O (70 mg,
0.23 mmol) were added and the solution was heated to 97 ºC in the dark for 24 hours, under nitrogen
atmosphere (without bubbling). After cooling to room temperature, the yellow solid was filtered off,
washed with water (3 × 100 mL), diethyl ether (3 × 100 mL) and dried. After purification by column
chromatography (eluent: from MeOH/CHCl3 5/95 to MeOH/CHCl3 10/90), the chloride-bridged
1
complex [(1)2Ir-µ-Cl]2 was obtained as a yellow solid (97.4 mg, 78%). H-NMR (400 MHz, DMSO-
d6): δ ppm 8.61 (s, 2H), 8.59 (s, 2H), 7.42 (ddd, J = 7.4, 1.4, 0.5 Hz, 2H), 7.41 (ddd, J = 7.5, 1.4, 0.5
Hz, 2H), 6.81 (ddd, J = 7.4, 7.4, 1.2 Hz, 2H), 6.80 (ddd, J = 7.4, 7.4, 1.2 Hz, 2H), 6.64 (ddd, J = 7.4,
7.4, 1.4 Hz, 2H), 6.63 (ddd, J = 7.4, 7.4, 1.5 Hz, 2H), 6.05 (ddd, J = 7.6, 1.2, 0.5 Hz, 2H), 6.00 (ddd,
J = 7.6, 1.2, 0.5 Hz, 2H), 4.30–4.26 (m, 12H). ESI-MS (ES+, CHCl3/CH3OH): m/z = 1053.1 [M-Cl]+.
[(2)2Ir-µ-Cl]2: A mixture 3/1 of 2-methoxyethanol/water (9 mL) was deoxygenated by bubbling
nitrogen through it for 10-15 min. The ligand 2 (50 mg, 0.18 mmol) and IrCl3⊕3H2O (21.4 mg,
0.072 mmol) were added and the solution was heated to 97 ºC in the dark for 24 hours, under nitrogen
atmosphere (without bubbling). After cooling to room temperature, the yellow solid was filtered off,
washed with water (3 × 80 mL) and dried. After purification by column chromatography (eluent: ethyl
acetate), the chloride-bridged complex [(2)2Ir-µ-Cl]2 was obtained as a yellow solid (35 mg, 62%). 1H-
NMR (400 MHz, CDCl3): δ ppm 7.83 (s, 2H), 7.77 (s, 2H), 7.27–7.22 (m, 4H), 6.75 (ddd, J = 7.4, 7.4,
1.1 Hz, 2H), 6.70 (ddd, J = 7.3, 7.3, 1.2 Hz, 2H), 6.64 (ddd, J = 7.2, 7.2, 1.1 Hz, 2H), 6.62 (ddd,
J = 7.3, 7.3, 1.2 Hz, 2H), 6.15 (dd, J = 7.4, 0.8 Hz, 2H), 6.04 (dd, J = 7.6, 0.5 Hz, 2H), 2.48–2.28 (m,

Molecules 2010, 15
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36H), 1.90–1.79 (m, 24H); 13C-NMR (75 MHz, CDCl3): δ ppm 157.0, 156.8, 145.9, 143.9, 136.3,
135.8, 132.9, 132.3, 127.24, 127.22, 121.08, 121.06, 120.8, 120.6, 113.9, 113.7, 61.9, 61.4, 42.9, 42.8,
35.79, 35.75, 29.49, 29.46; ESI-MS (ES+, CHCl3/CH3OH): m/z = 807.0 [(M/2)+Na]+
[(1)(2)Ir-µ-Cl]2: A mixture 3/1 of 2-methoxyethanol/water (12 mL) was deoxygenated by bubbling
nitrogen through it for 10-15 min. The ligands 1 (40 mg, 0.25 mmol) and 2 (70.2 mg, 0.25 mmol), and
IrCl3⊕3H2O (62.5 mg, 0.21 mmol) were added and the solution was heated to 97 ºC in the dark for
24 hours, under nitrogen atmosphere (without bubbling). After cooling to room temperature, the
yellow solid was filtered off, washed with water (3 × 80 mL) and dried. This reaction is expected to
yield a mixture of chloride-bridged complexes [(X)(Y)Ir-µ-Cl]2 (X=Y=1,2). The reaction was followed
by TLC (eluent: CH3OH/CHCl3 20/80) where several spots, corresponding to different dimeric
species, could be observed. The crude material was further reacted without purification.
[Ir(1)2(pytl-Me)]Cl: To a suspension of the precursor [(1)2Ir-µ-Cl]2 (47.2 mg, 0.043 mmol) in
MeOH/CHCl3 1/3 v/v (4 mL) was added pytl-Me as a solid (14.6 mg, 0.086 mmol). The suspension
was heated to 45 ºC and stirred in the dark for 3 hours, after which time a clear and yellow solution
was obtained. The reaction was followed by TLC (eluent: MeOH/CHCl3 30/70) where, under UV light
at 366 nm, the compound appeared as a bright green-blue luminescent spot. After removal of the
solvent in vacuo, the solid obtained was purified by PLC (eluent: MeOH/CHCl3 25/75). The product
was obtained as a slightly yellow solid (47.4 mg, 80%). 1H-NMR (400 MHz, CDCl3): δ ppm 10.48 (s,
1H), 8.88 (d, J = 7.9 Hz, 1H), 7.93-7.87 (m, 2H), 7.77 (s, 1H), 7.73 (s, 1H), 7.43 (dd, J = 7.5, 1.1 Hz,
1H), 7.39 (dd, J = 7.4, 1.1 Hz, 1H), 7.12 (ddd, J = 7.5, 5.6, 1.3 Hz, 1H), 6.96 (ddd, J = 7.5, 7.5, 1.2 Hz,
1H), 6.92 (ddd, J = 7.4, 7.4, 1.2 Hz, 1H), 6.85 (ddd, J = 7.5, 7.5, 1.4 Hz, 1H), 6.81 (ddd, J = 7.5, 7.5,
1.4 Hz, 1H), 6.32–6.28 (m, 2H), 4.16 (s, 3H), 4.08 (s, 3H), 4.05 (s, 3H); 13C-NMR (75 MHz, CDCl3): δ
ppm 157.9, 157.5, 151.1, 150.3, 149.3, 146.1, 142.3, 139.0, 135.3, 135.0, 132.75, 132.73, 128.9, 128.6,
128.1, 124.8, 123.7, 122.6, 122.3, 122.2, 122.1, 118.9, 118.8, 38.60, 38.56, 38.5; HRMS (ES+,
CH3OH): m/z calcd for C26H24IrN10: 669.18146; found: 669.18464 M+.
[Ir(2)2(pytl-ada)]Cl: To a suspension of the precursor [(2)2Ir-µ-Cl]2 (20.0 mg, 0.013 mmol) in
MeOH/CHCl3 1/3 v/v (4 mL) was added pytl-ada as a solid (7.29 mg, 0.026 mmol). The suspension
was heated to 45 ºC and stirred in the dark for 3 hours, after which time a clear and yellow solution
was obtained. The reaction was followed by TLC (eluent: MeOH/CHCl3 20/80) where, under UV light
at 366 nm, the compound appeared as a bright green-blue luminescent spot. After removal of the
solvent in vacuo, the solid obtained was purified by column chromatography (eluent: from CHCl3 to
MeOH/CHCl3 5/95). The product was obtained as a slightly yellow solid (20.3 mg, 76%). 1H-NMR
(400 MHz, CDCl3): δ ppm 10.56 (s, 1H), 9.16 (d, J = 7.8 Hz, 1H), 7.96 (bd, J = 5.4 Hz, 1H), 7.92
(ddd, J = 7.8, 7.8, 1.4 Hz, 1H), 7.76 (s, 1H), 7.71 (s, 1H), 7.34 (dd, J = 5.7, 1.3 Hz, 1H), 7.32 (dd,
J = 5.6, 1.2 Hz, 1H), 7.07 (ddd, J = 7.2, 5.8, 1.2 Hz, 1H), 6.91 (ddd, J = 6.7, 6.7, 1.2 Hz, 1H), 6.88
(ddd, J = 6.6, 6.6, 1.2 Hz, 1H), 6.82 (ddd, J = 7.4, 7.4, 1.4 Hz, 1H), 6.77 (ddd, J = 7.5, 7.5, 1.4 Hz,
1H), 6.16 (dd, J = 7.6, 0.6 Hz, 1H), 6.13 (dd, J = 7.5, 0.6 Hz, 1H), 2.30–2.19 (m, 15H), 2.13–2.10 (m,
12H), 1.81–1.68 (m, 18H); 13C-NMR (75 MHz, CDCl3): δ ppm 156.7, 156.1, 151.7, 150.0, 148.9,
146.8, 143.3, 138.9, 136.1, 135.7, 133.0, 132.3, 128.2, 127.4, 125.2, 124.01, 123.95, 122.1, 121.7,

Molecules 2010, 15
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121.5, 121.2, 114.1, 114.0, 62.2, 61.9, 61.8, 42.70, 42.67, 42.5, 35.67, 35.63, 29.7, 29.5, 29.37, 29.36;
HRMS (ES+, CH3OH): m/z calcd for C53H60IrN10: 1029.46316; found: 1029.46242 M+.
[Ir(1)(2)(pytl-ada)]Cl: To a suspension of the crude mixture of the precursors [(X)(Y)Ir-µ-Cl]2
(X=1,2; Y=1,2) (76.2 mg) in MeOH/CHCl3 1/3 v/v (8 mL) was added pytl-ada as a solid (44.8 mg,
0.16 mmol). The suspension was heated to 45 ºC and stirred in the dark for 3 hours, after which time a
yellow solution was obtained. The reaction was followed by TLC (eluent: MeOH/CHCl3 20/80). The
mixture of products obtained could not be separated by column chromatography. After removal of the
solvent in vacuo, the crude material was purified by using a semipreparative HPLC equipped with a
reversed-phase column. The mobile phase was a gradient of H2O and acetonitrile (50% for 20 min +
gradient 50% to 100% v/v of acetonitrile in 40 min) both containing 0.1% v/v HCl. The complex
[Ir(1)(2)(pytl-ada)]Cl exists in four stereoisomeric forms: the two diastereoisomers A and B
(Scheme 7), and their corresponding enantiomers (Λ,Δ). The diastereoisomeric species A(Λ+Δ) and
B(Λ+Δ) could be separated by HPLC in the conditions described above. However, we did not perform
their isolation and collected them as a mixture. The HPLC fractions containing the desired iridium
complex were identified by ESI-MS. The retention time of the two peaks of [Ir(1)(2)(pytl-ada)]Cl were
t = 41.9 min and t = 43.3 min. After collecting the fractions, the solvent was removed in vacuo at
40 ºC. The product was obtained as a slightly yellow solid (21.1 mg, overall yield = 11%) containing
1
the two diastereoisomers in a ratio 1:0.8 as calculated from the NMR spectrum. H-NMR (400 MHz,
CDCl3): δ ppm 10.49 (s, 0.8H), 10.45 (s, 1H), 9.12–9.05 (m, 1H+0.8H), 7.93–7.83 (m, 2H+1.6H), 7.77
(bs, 1.6H), 7.76 (s, 1H), 7.73 (s, 1H), 7.33 (dd, J = 7.4, J = 1.1 Hz, 1.6H), 7.32 (dd, J = 7.2, J = 1.1 Hz,
1H), 7.29 (dd, J = 7.4, J = 1.2 Hz, 1H), 7.08–7.02 (m, 1H+0.8H), 6.92–6.76 (m, 3H+2.4H), 6.75 (ddd,
J = 7.4, J = 7.4, J = 1.3 Hz, 0.8H) 6.74 (ddd, J = 7.4, J = 7.4, J = 1.3 Hz, 1H), 6.31 (d, J = 7.5 Hz,
0.8H), 6.24 (d, J = 7.5 Hz, 1H), 6.12 (d, J = 7.5 Hz, 1H), 6.08 (d, J = 7.5 Hz, 0.8H), 4.02 (s, 2.4H),
4.00 (s, 3H), 2.28–2.22 (m, 9H+7.2H), 2.22–2.17 (m, 3H+2.4H), 2.14–2.09 (m, 6H+4.8H), 1.82–1.66
(m, 12H+9.6H); 13C-NMR (75 MHz, CDCl3): δ ppm 157.8, 157.2, 156.6, 156.0, 151.48, 151.47, 150.1,
149.9, 148.84, 148.79, 146.5, 146.2, 143.2, 142.9, 138.9–138.8 (m), 135.9, 135.63, 135.60, 135.4,
133.1, 132.9, 132.4, 132.2, 128.2, 128.1, 127.5, 127.3, 125.1, 124.9, 124.3, 124.2, 123.7, 123.6,
122.23, 122.19, 122.1, 121.8, 121.7, 121.56, 121.55, 121.3, 119.2, 119.0, 114.3, 114.1, 62.4, 62.3,
61.9, 61.8, 42.62, 42.57, 42.4, 42.3, 38.5, 38.4, 35.60, 35.58, 35.55, 29.41–29.37 (m), 29.32, 29.30;
HRMS (ES+, CH3OH): m/z calcd for C44H48IrN10: 909.36926; found: 909.37012 M+.
Scheme 7. Structure of the diastereoisomers A and B of [Ir(1)(2)(pytl-ada)]Cl.

Molecules 2010, 15
2056
[Ir(1)2(pytl-DC)]Cl: To a suspension of the precursor [(1)2Ir-µ-Cl]2 (28.3 mg, 0.026 mmol) in
MeOH/CHCl3 1/3 v/v (4 mL) was added pytl-DC as a solid (26.8 mg, 0.052 mmol). The suspension
was heated to 45 ºC and stirred in the dark for 17 hours, after which time a clear and yellow solution
was obtained. The reaction was followed by TLC (eluent: MeOH/CHCl3 20/80) where, under UV light
at 366 nm, the compound appeared as a bright green-blue luminescent spot. After removal of the
solvent in vacuo, the solid obtained was purified by PLC (eluent: MeOH/CHCl3 20/80). The product
was obtained as a slightly yellow solid (39.1 mg, 73%) containing a mixture 1:1 of two
diastereoisomers as also confirmed by the NMR spectrum. 1H-NMR (400 MHz, CD3OD): δ ppm 9.041
(s, 1H), 9.038 (s, 1H), 8.24–8.23 (m, 1H), 8.23 –8.22 (m, 3H), 8.20–8.16 (m, 2H), 8.08–7.99 (m, 4H),
7.50–7.46 (m, 2H), 7.44–7.40 (m, 2H), 7.34–7.30 (m, 2H), 6.97–6.92 (m, 2H), 6.88–6.79 (m, 4H), 6.71
(ddd, J = 7.4, J = 1.4, J = 1.4 Hz, 2H), 6.29 (ddd, J = 7.5, J = 1.1, J = 0.5 Hz, 1H), 6.28 (ddd,
J = 7.6, J = 1.1, J = 0.5 Hz, 1H), 6.25–6.22 (m, 2H), 4.81–4.76 (m, 2H), 4.07–4.06 (m, 6H), 4.05 (bs,
6H), 3.51–3.42 (m, 2H), 2.37–0.89 (m, 64H), 0.72 (s, 6H); HRMS (ES+, CH3OH): m/z calcd for
C49H60IrN10O3: 1029.44791; found: 1029.44633 M+.
[Ir(1)2(pytl-βCD)]Cl: To a suspension of the precursor [(1)2Ir-µ-Cl]2 (7.04 mg, 0.006 mmol) in
MeOH/CHCl3 1/3 v/v (4 mL) was added pytl-βCD as a solid (20.1 mg, 0.013 mmol). The suspension
was heated to 45 ºC and stirred in the dark for 3 hours, after which time a clear and yellow solution
was obtained. The reaction was followed by TLC (eluent: MeOH/CHCl3 15/85) where, under UV light
at 366 nm, the compound appeared as a bright green-blue luminescent spot. After removal of the
solvent in vacuo, the solid obtained was purified by column chromatography (eluent: MeOH/CHCl3
5/95). The product was obtained as a slightly yellow solid (16.0 mg, 59%) containing a mixture 1:1 of
1
two diastereoisomers as also confirmed by the NMR spectrum. H-NMR (300 MHz, CDCl3): δ ppm
9.73 (s, 1H), 9.63 (s, 1H), 8.87–8.68 (m, 2H), 7.95–7.87 (m, 2H), 7.81 (s, 1H), 7.78 (s, 1H), 7.744 (s,
1H), 7.736 (s, 1H), 7.40–7.21 (m, 6H), 7.17–7.11 (m, 2H), 6.97–6.65 (m, 8H), 6.30–6.21 (m, 2H),
6.17–6.06 (m, 2H), 5.57–5.46 (m, 1H), 5.39–5.03 (m, 13H), 4.95–4.83 (m, 1H), 4.78–4.69 (m, 1H),
4.17 (s, 3H), 4.12 (s, 3H), 4.11 (s, 3H), 4.05 (s, 3H), 4.15–2.98 (m, 200H), 2.96–2.89 (m, 1H),
2.81–2.74 (m, 1H); HRMS (ES+, CH3OH): m/z calcd for C87H130IrN10O34: 2051.83801; found:
2051.83965 M+.
Acknowledgements
The authors thank the European Union for support through the Marie Curie Research and Training
Network UNI-NANOCUPS. M.F. acknowledges University “La Sapienza” of Rome for a scholarship.
R.J.M.N. acknowledges the Royal Netherlands Academy of Science and Art for financial support.
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Sample Availability: Not Available.
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