# Thin Film Electrodeposition of Ir(III) Cyclometallated Complexes

Authors: Andreea Ionescu; Iolinda Aiello; Alessandra Crispini; Nicolas Godbert
Journal: Journal of Chemistry
 (2016)

---

## Abstract

Novel electropolymerizable Ir(III) cyclometallated complexes have been synthesized and characterized. In these complexes the cyclometallated ligands are either 2-phenylpyridineH(PhPy) or benzothiazole-triphenylamineH(BzTh-tpa), while the Ir(III) coordination sphere is completed by a Schiff base substituted with a triphenylamine fragment. A complete electrochemical study has been conducted on all complexes, in order to verify the feasibility of electropolymerization and to elucidate the role of the specific position of the triphenylamine moiety in the molecular structure. Homogeneous thin films of Ir(III) metallopolymers have been successfully obtained through electropolymerization process.


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## Body

## 1. Introduction

Metallopolymers represent a fast rising class of functional materials due to their combined specific properties induced by metal centers and the processability and low cost of synthetic polymers [1]. Since the first reported poly(vinylferrocene) [2], metallopolymers (especially those containing d- and f-block metals) have been used in optoelectronic (super/semiconductors, electrochromic, and luminescent devices) and catalysis processes. Many polymerization techniques have been employed in the synthesis of metallopolymers, including “living” polymerization routes and self-assembling methods [3]. Nevertheless, the controlled deposition of high quality polymeric films on different substrates, a key step towards functional applications, still represents a challenge.In the case of deposition of metallopolymers, electropolymerization presents several advantages over the different film generating methods based on transition metal complexes, like layer-by-layer assembly [4], spin-casting [5], drop-casting [6], or electrostatic binding in the case of polyelectrolyte films [7]. In the electropolymerization process, the polymer formation and its deposition occur simultaneously, avoiding limitation such as scarce solubility of polymeric networks and leading to controllable film composition, thickness, and surface coverage [8].The first reports on the electrodeposition of organometallic monomers are referred to the reductive electropolymerization of vinyl-substituted polypyridine complexes [9]. Up to date, different electropolymerizable groups such as thiophene [10, 11], pyrrole [12], aromatic amines [13–15], and diphenylamino [16, 17] have been introduced in organometallic compounds. The obtained neutral and ionic complexes of different metal centers (Ru, Os, Fe, and Ir) [8] have afforded thein situ preparation and the deposition of metallopolymeric films on different conducting substrates.In this context, a series of electropolymerizable cyclometallated square planar photoconductive Pd(II) and Pt(II) complexes, containing as ancillary ligand a Schiff base substituted with a triphenylamine group, were recently reported by our group (Scheme1). The use of this specifically functionalized Schiff base ligands has been the key factor in the induction of an electropolymerization process during repetitive potential scans, allowing the deposition of highly stable and homogeneous electroactive and photoconductive Pd(II) and Pt(II) metallopolymers [18].Scheme 1
Electropolymerizable Pd(II)/Pt(II) complexes from [18].The choice of the triphenylamine substituent as a potential electropolymerizable fragment has been motivated by its ability to form cross-linked conjugated polymeric networks, favouring isotropic charge transport and showing high electrochemical stability [16, 17, 19].In order to extend the developed electrodeposition method towards octahedral complexes, we have incorporated the triphenylamine electropolymerizable Schiff baseH
(
O
∧
N
)
t
p
a (Figure 1) into Ir(III) cyclometallated complexes. Therefore, herein a series of new cyclometallated Ir(III) complexes containing the electropolymerizable Schiff base H
(
O
∧
N
)
t
p
a is reported, together with corresponding model complexes as direct comparison, where the H
(
O
∧
N
)
C
6 Schiff base ligand is lacking the electropolymerizable group (Figure 1).Figure 1
Molecular structures of the synthesized Ir(III) complexesI–IV and the O-, N-coordinated ligands.A complete electrochemical study has been performed on the novel complexesI–IV, in order to establish their redox behaviour and to probe the electrodeposition feasibility as high quality thin films.


## 2. Materials and Methods

All commercially available chemicals were purchased from Aldrich Chemical Co. and were used without further purification. IR spectra (KBr pellets) were recorded on a Perkin-Elmer Spectrum One FT-IR spectrometer.1H-NMR spectra were recorded on a Bruker WH-300 spectrometer in deuterated solvents with TMS as an internal standard. Elemental analyses were performed with a Perkin-Elmer 2400 analyzer CHNS/O. Melting points were examined with a Leica DMLP polarising microscope equipped with a Leica DFC280 camera and a CalCTec (Italy) heating stage.All potentials were measured using an Epsilon electrochemical analyser. Voltammetry experiments were performed in a 3 mL cell of dry and degassed (N2) dichloromethane solution using tetrabutylammonium hexafluorophosphate (0.1 M) as a supporting electrolyte, a Pt disk working as electrode, a Pt wire as counterelectrode, and an Ag wire as a pseudoreference electrode. Voltammograms were recorded at a 100 mV s−1 scan rate fromca. 10−3 M complex solutions. Redox potentials are given relative to a ferrocene/ferrocenium (Fc/Fc+) redox couple used as an internal reference. Estimation of HOMO/LUMO energy values was performed taking into account −4.8 eV for the couple Fc/Fc+ [20].


## 3. Results and Discussion

### 3.1. Synthesis

The two first synthesized Ir(III) model complexesI andII contain thePhPy fragment as cyclometallated ligands and the Schiff bases H
(
O
∧
N
)
C
6 [21] and H
(
O
∧
N
)
t
p
a [18], respectively, as ancillary ligands. In order to complete the comparing series of Ir(III) complexes and study the influence of the position of theTPA fragment on the coordinated ligands with respect to the electropolymerization process, the two cyclometallated benzothiazole-triphenylamine Ir(III) complexesIII andIV, containing the same Schiff bases H
(
O
∧
N
)
C
6 and H
(
O
∧
N
)
t
p
a
, were synthesized.The synthesis of all the complexesI–IV (Scheme 2) was achieved starting from their corresponding dichlorobridged dimer. In particular, complexesI andII were obtained starting from the already described chlorobridged dimer1 [22]. In the case of complexesIII andIV, after synthesizing the cyclometallating ligandH(BzTh-tpa) [23], the corresponding dichlorobridged cyclometallated Ir(III) intermediate2 was obtained by modification of the reported procedure [23].Scheme 2
Reagents and conditions: (i) for1: 2-ethoxyethanol/water: 3/1, reflux, 48 h; for2: ethoxyethanol/water: 3/1, reflux, 4 d., N2; (ii) dichloromethane/acetone, reflux, 48 h.Finally, through bridge splitting reaction between the respective bridged intermediate and the appropriate substituted Schiff base, in the presence of an excess of trimethylamine for the complete deprotonation of the ancillary ligand, a single isomer of the final complexesI–IV was obtained in overall high yields.


### 3.2. Electrochemical Studies

ComplexesI–IV redox behaviour was studied by cyclic voltammetry. The measured oxidation potentials and the estimated HOMO levels are reported in Table 1, together with theH(BzTh-tpa) ligand oxidation potential added for direct comparison. The corresponding obtained cyclic voltammograms are shown in Figure 2.Table 1
Cyclic voltammetry data relative to complexesI–IV and H(BzTh-tpa). E
o
x
n, n
=
1,2
,
3, refer to the oxidation waves recorded on increasing potential. Estimated HOMO.
E
o
x
1 (mV)
E
o
x
2 (mV)
E
o
x
3 (mV)
HOMO (eV)
I
+165 (R)
/
/
−5.0
II
+190 (R)
+510 (R)
/
−5.0
H(BzTh-tpa)
+545 (R)
/
/
−5.3
III
+150 (R)
+530 (R)
/
−4.9
IV
+162 (QR)
+370 (R)
+545 (R)
−5.0
All potentials are given versus Fc/Fc+. (R): reversible wave; (QR): quasireversible.Figure 2
Cyclic voltammograms of (a) complexesI-II and (b) ligandH(BzTh-tpa) and complexesIII-IV. Scan rate 100 mV s−1 in dry dichloromethane.
(a)
(b)Considering the oxidation behaviour of the model complexesI-II (Figure 2(a)), the single reversible one-electron wave seen in the case of complexI can be attributed to the Schiff base H
(
O
∧
N
)
C
6 oxidation, while the two consecutive oxidation waves observed in the cyclic voltammogram ofII are typical of the triphenylamine moiety of the H
(
O
∧
N
)
t
p
a Schiff base [18].For the two reversible oxidation waves observed in the case of complexIII, the first one is probably associated with the Schiff base (
O
∧
N
)
C
6, while the second reversible wave can reasonably be attributed to the oxidation of the cyclometallated ligand [24],H(BzTh-tpa) showing, in the solvent window explored (−1.2–1.45 V), a single reversible oxidation atca. +545 mV versus Fc/Fc+.Regarding the oxidation properties of complexIV, a specific and unambiguous attribution of the oxidation processes on a molecular scale resulted to be unfeasible due to the overlap of the oxidation waves of the various fragments. However, according to the potential value of the first quasireversible wave, this oxidation process can be reasonably attributed to the first oxidation process of the H
(
O
∧
N
)
t
p
a Schiff base ligand. For all complexesI–IV, no reduction wave was recorded in the allowed solvent window (−1.2–1.45 V).As expected for complexI, no electropolymerization process was observed upon repetitive potential scan cycles, but neither for complexII containing the (
O
∧
N
)
t
p
a triphenylamine substituted Schiff base nor for complexIII, where the triphenylamine fragment is on the cyclometallated ligand, such electropolymerization processes were recorded (Figure 3). The slight increase in the current intensity visible on the respective cyclic voltammograms is only due to minor accumulation of oxidized specie at the surface electrode.Figure 3
Cyclic voltammograms of (a)II and (b)III obtained from six consecutive oxidation scans.
(a)
(b)From these observations, we can conclude that for the triphenylamine moieties incorporated either in the Schiff base (complexII) or in the cyclometallated ligand (BzTh-tpa) (complexIII) the electropolymerization is prevented, probably due to electronic factors induced by the nature of the other ligands surrounding the Ir(III) center. Indeed, as previously reported, the presence of electrowithdrawing substituents in paraposition with respect to triphenylamine fragments highly controls the electropolymerization process in which these units are involved [25].On the contrary, upon repetitive oxidation scans, a distinctive regular increase in current is observed in the cyclic voltammogram ofIV, which is typical of the electropolymerization of the substituted triphenylamine fragment (Figure 4(a)) [23]. In this case, the synergistic electronic contribution of all substituents on both the cyclometallated and the ancillary ligands produces an overall withdrawing effect able to allow the electropolymerization of the triphenylamine fragment of the (
O
∧
N
)
t
p
a Schiff base.Figure 4
(a) Cyclic voltammograms ofIV obtained from six consecutive oxidation scans and (b) cyclic voltammogram in fresh dichloromethane electrolytic solution of the resulting modified Pt electrode obtained after 20 cycles.
(a)
(b)Once the polymer was formed, the modified Pt disk working electrode covered with complexIV electropolymerized film was immersed in a freshly distilled dichloromethane solution (0.1 M electrolytic solution). The recorded cyclic voltammogram proved the electroactivity and stability of the deposited film (Figure 4(b)).Electrogenerated thin films ofIV were deposited on ITO etched glass substrates. A cyclic voltammogram recorded upon electropolymerization ofIV onto an ITO glass substrate is shown in Figure 5 together with the photography of the obtained deposited thin film.Figure 5
Electropolymerization ofIV on ITO substrate (20 cycles).


## 3.1. Synthesis

The two first synthesized Ir(III) model complexesI andII contain thePhPy fragment as cyclometallated ligands and the Schiff bases H
(
O
∧
N
)
C
6 [21] and H
(
O
∧
N
)
t
p
a [18], respectively, as ancillary ligands. In order to complete the comparing series of Ir(III) complexes and study the influence of the position of theTPA fragment on the coordinated ligands with respect to the electropolymerization process, the two cyclometallated benzothiazole-triphenylamine Ir(III) complexesIII andIV, containing the same Schiff bases H
(
O
∧
N
)
C
6 and H
(
O
∧
N
)
t
p
a
, were synthesized.The synthesis of all the complexesI–IV (Scheme 2) was achieved starting from their corresponding dichlorobridged dimer. In particular, complexesI andII were obtained starting from the already described chlorobridged dimer1 [22]. In the case of complexesIII andIV, after synthesizing the cyclometallating ligandH(BzTh-tpa) [23], the corresponding dichlorobridged cyclometallated Ir(III) intermediate2 was obtained by modification of the reported procedure [23].Scheme 2
Reagents and conditions: (i) for1: 2-ethoxyethanol/water: 3/1, reflux, 48 h; for2: ethoxyethanol/water: 3/1, reflux, 4 d., N2; (ii) dichloromethane/acetone, reflux, 48 h.Finally, through bridge splitting reaction between the respective bridged intermediate and the appropriate substituted Schiff base, in the presence of an excess of trimethylamine for the complete deprotonation of the ancillary ligand, a single isomer of the final complexesI–IV was obtained in overall high yields.


## 3.2. Electrochemical Studies

ComplexesI–IV redox behaviour was studied by cyclic voltammetry. The measured oxidation potentials and the estimated HOMO levels are reported in Table 1, together with theH(BzTh-tpa) ligand oxidation potential added for direct comparison. The corresponding obtained cyclic voltammograms are shown in Figure 2.Table 1
Cyclic voltammetry data relative to complexesI–IV and H(BzTh-tpa). E
o
x
n, n
=
1,2
,
3, refer to the oxidation waves recorded on increasing potential. Estimated HOMO.
E
o
x
1 (mV)
E
o
x
2 (mV)
E
o
x
3 (mV)
HOMO (eV)
I
+165 (R)
/
/
−5.0
II
+190 (R)
+510 (R)
/
−5.0
H(BzTh-tpa)
+545 (R)
/
/
−5.3
III
+150 (R)
+530 (R)
/
−4.9
IV
+162 (QR)
+370 (R)
+545 (R)
−5.0
All potentials are given versus Fc/Fc+. (R): reversible wave; (QR): quasireversible.Figure 2
Cyclic voltammograms of (a) complexesI-II and (b) ligandH(BzTh-tpa) and complexesIII-IV. Scan rate 100 mV s−1 in dry dichloromethane.
(a)
(b)Considering the oxidation behaviour of the model complexesI-II (Figure 2(a)), the single reversible one-electron wave seen in the case of complexI can be attributed to the Schiff base H
(
O
∧
N
)
C
6 oxidation, while the two consecutive oxidation waves observed in the cyclic voltammogram ofII are typical of the triphenylamine moiety of the H
(
O
∧
N
)
t
p
a Schiff base [18].For the two reversible oxidation waves observed in the case of complexIII, the first one is probably associated with the Schiff base (
O
∧
N
)
C
6, while the second reversible wave can reasonably be attributed to the oxidation of the cyclometallated ligand [24],H(BzTh-tpa) showing, in the solvent window explored (−1.2–1.45 V), a single reversible oxidation atca. +545 mV versus Fc/Fc+.Regarding the oxidation properties of complexIV, a specific and unambiguous attribution of the oxidation processes on a molecular scale resulted to be unfeasible due to the overlap of the oxidation waves of the various fragments. However, according to the potential value of the first quasireversible wave, this oxidation process can be reasonably attributed to the first oxidation process of the H
(
O
∧
N
)
t
p
a Schiff base ligand. For all complexesI–IV, no reduction wave was recorded in the allowed solvent window (−1.2–1.45 V).As expected for complexI, no electropolymerization process was observed upon repetitive potential scan cycles, but neither for complexII containing the (
O
∧
N
)
t
p
a triphenylamine substituted Schiff base nor for complexIII, where the triphenylamine fragment is on the cyclometallated ligand, such electropolymerization processes were recorded (Figure 3). The slight increase in the current intensity visible on the respective cyclic voltammograms is only due to minor accumulation of oxidized specie at the surface electrode.Figure 3
Cyclic voltammograms of (a)II and (b)III obtained from six consecutive oxidation scans.
(a)
(b)From these observations, we can conclude that for the triphenylamine moieties incorporated either in the Schiff base (complexII) or in the cyclometallated ligand (BzTh-tpa) (complexIII) the electropolymerization is prevented, probably due to electronic factors induced by the nature of the other ligands surrounding the Ir(III) center. Indeed, as previously reported, the presence of electrowithdrawing substituents in paraposition with respect to triphenylamine fragments highly controls the electropolymerization process in which these units are involved [25].On the contrary, upon repetitive oxidation scans, a distinctive regular increase in current is observed in the cyclic voltammogram ofIV, which is typical of the electropolymerization of the substituted triphenylamine fragment (Figure 4(a)) [23]. In this case, the synergistic electronic contribution of all substituents on both the cyclometallated and the ancillary ligands produces an overall withdrawing effect able to allow the electropolymerization of the triphenylamine fragment of the (
O
∧
N
)
t
p
a Schiff base.Figure 4
(a) Cyclic voltammograms ofIV obtained from six consecutive oxidation scans and (b) cyclic voltammogram in fresh dichloromethane electrolytic solution of the resulting modified Pt electrode obtained after 20 cycles.
(a)
(b)Once the polymer was formed, the modified Pt disk working electrode covered with complexIV electropolymerized film was immersed in a freshly distilled dichloromethane solution (0.1 M electrolytic solution). The recorded cyclic voltammogram proved the electroactivity and stability of the deposited film (Figure 4(b)).Electrogenerated thin films ofIV were deposited on ITO etched glass substrates. A cyclic voltammogram recorded upon electropolymerization ofIV onto an ITO glass substrate is shown in Figure 5 together with the photography of the obtained deposited thin film.Figure 5
Electropolymerization ofIV on ITO substrate (20 cycles).


## 4. Conclusions

Novel biscyclometallated Ir(III) complexes (I–IV), bearing (PhPy) or (BzTh-tpa) as cyclometallated ligand as well as substituted Schiff bases as (
O
∧
N
) chelated ancillary ligand, have been synthesized. A complete electrochemical study has been performed on all complexes. It has been observed that electropolymerization of the triphenylamine fragment is highly dependent onto the nature of the ligands incorporated within the coordination sphere of the metal ion. Indeed, the introduction of the triphenylamine fragment on the Schiff base (
O
∧
N
)
t
p
a ligand in the presence of the cyclometallated (BzTh-tpa) ligands favoured the electropolymerization process. Upon repetitive potential scans, high quality polymeric thin films of complexIV have been electrodeposited on ITO covered glass electrodes. The presence of the triphenylamine fragment in the Schiff base represents thus a necessary condition in order to induce electropolymerization. However, the described results of the electrochemical study proved that this condition is not sufficient, as demonstrated by the lack of electropolymerization in the case of complexII bearing (PhPy) fragments as cyclometallated ligands. Furthermore, investigations of the photophysical and electrochromic properties of these metallopolymers are in progress, in order to test the potential application of Ir(III) thin films in electroluminescent and/or electrochromic devices.


## 5. Experimental Details

### 5.1. Synthesis of ComplexI

Intermediate complex1 [22] (150 mg, 0.14 mmol) was solubilized inca. 50 mL of a 1 : 1 mixture of acetone and chloroform. 2 eqs. of H
(
O
∧
N
)
C
6 [21] (87 mg, 0.28 mmol) and 30 eqs. (0.3 mL, 4.2 mmol) of trimethylamine were added to the solution. The reaction mixture was stirred at reflux for 72 h. The solvent was evaporated and the organic phase extracted with dichloromethane/water and dried over sodium sulphate. The crude product was purified by precipitation from dichloromethane/n-hexane. The solid was filtered off, washed with hexane, and dried under vacuum.Red solid; yield 66% (149 mg); m.p. > 250°C;1H NMR (300 MHz, CDCl3, 25°C, TMS) δ
=
8.92 (d, J
=
5.49 Hz, 1H), 8.86 (d, J
=
5.79 Hz, 1H), 8.05 (s, 1H), 7.88 (d, J
=
8.37 Hz, 1H), 7.67 (d, J
=
13 Hz, 1H), 7.68 (t, J
=
14 Hz, 1H), 7.59 (d, J
=
7.83 Hz, 1H), 7.51 (d, J
=
8.1 Hz, 1H), 7.12 (t, J
=
5.76 Hz, 1H), 7.06–7.00 (m, 2H), 6.95 (d
d, J
=
9.18 Hz, J
=
3.3 Hz, 1H), 6.85 (t, J
=
7.95 Hz, 1H), 6.72 (t, J
=
7.26 Hz, 1H), 6.65 (d, J
=
9.18 Hz, 1H), 6.57 (d, J
=
3.3 Hz, 1H), 6.51–6.49 (m, 4H), 6.28 (d, J
=
7.26 Hz, 1H), 6.17 (d, J
=
7.69 Hz, 1H), 6.02 (d, J
=
8.25 Hz), 3.71 (s, 3H), 2.35 (t, J
=
7.56 Hz, 2H), 1.67–1.22 (m, 8H), 0.93 (t, J
=
6.72 Hz, 3H, –OCH3); FT-IR (KBr, cm−1): 3041, 2996, 2925, 2853 (alkyl stretching), 1620 (CN Schiff base), 1604, 1584, 1476, 1465, 1425, 1314, 1212, 1147, 1030, 755, 729; elemental analysis calculated for C42H40IrN3O2 (811.00 g/mol): C 62.20%, H 4.97%, N 5.18%, found C 62.50%, H 5.14%, N 5.20%.


### 5.2. Synthesis of ComplexII

1 (100 mg, 0.09 mmol) was solubilized inca. 50 mL of a 1 : 1 mixture of acetone and chloroform. 2 eqs. of H
(
O
∧
N
)
t
p
a [18] (88 mg, 0.18 mmol) and 30 eqs. (0.2 mL, 2.8 mmol) of trimethylamine were added to the solution. The reaction mixture was stirred at reflux for 72 h. The solvent was evaporated and the organic phase extracted with dichloromethane/water and dried over sodium sulphate. The crude product was purified by precipitation from dichloromethane/hexane. The solid was filtered off, washed with n-hexane, and dried under vacuum.Red solid; yield 80% (145 mg); m.p. > 250°C;1H NMR (300 MHz, CDCl3, 25°C, TMS) δ
=
8.93 (d, J
=
5.34 Hz, 1H), 8.89 (d, J
=
5.49 Hz, 1H), 7.89 (d, J
=
8.1 Hz, 1H), 7.75–7.59 (m, 3H), 7.50 (d, J
=
8.1 Hz, 1H), 7.31–7.22 (m, 4H), 7.14–7.02 (m, 13H), 6.99–6.95 (m, 1H), 6.89–6.83 (m, 3H), 6.75–6.65 (m, 2H), 6.59 (d, J
=
3.18 Hz, 1H), 6.56–6.54 (m, 2H), 6.29 (d, J
=
7.68 Hz, 1H), 6.22–6.19 (m, 1H), 6.16 (d, J
=
8.25 Hz, 2H), 3.72 (s, 3H, –OCH3); FT-IR (KBr, cm−1): 3030, 2920, 2833 (alkyl stretching), 1610 (CN Schiff base), 1584, 1525, 1486, 1476, 1436, 1313, 1267, 1212, 1146, 1029, 823, 753, 729, 695; elemental analysis calculated for C54H41IrN4O2 (970.29 g/mol): C 66.85%, H 4.26%, N 5.78%, found: C 66.80%, H 4.14%, N 5.82%.


### 5.3. Synthesis of Intermediate Complex2

To a degassed aqueous solution (10 mL) of IrCl3·xH2O (93 mg, 0.25 mmol), 2 eqs. ofH(BzTh-tpa) [23] (200 mg, 0.50 mmol) solubilized in 30 mL of degassed ethoxyethanol is added. The reaction mixture was refluxed for 4 days under inert atmosphere (N2). A brown solid is filtered off and washed with distilled water and ethanol and dried under vacuum.Brown solid; yield 40% (96 mg); m.p. > 250°C;1H NMR (CDCl3, 300 MHz, TMS) δ
=
8.62 (d, J
=
6.0 Hz, 2H), 7.27 (d, J
=
1.23 Hz, 2H), 7.05–7.03 (m, 4H), 6.95–6.91 (m, 10H), 6.84–6.81 (m, 4H), 6.70–6.68 (m, 8H), 6.46 (d
d, J
=
8.45 Hz, J
=
2.04 Hz, 2H), 5.48 (d, J
=
2.19 Hz, 2H); FT-IR (KBr, cm−1): 1571, 1498, 1459, 1429, 1378, 1262, 1096, 1022, 802, 749, 694, 508; elemental analysis calculated for C50H34Cl2Ir2N4S2: C 49.54%, H 2.99%, N 4.62%, found: C 49.60%, H 3.04%, N 4.42%.


### 5.4. Synthesis of ComplexIII

Intermediate complex2 (75 mg, 0.038 mmol) was solubilized inca. 50 mL of a 1 : 1 mixture of acetone and chloroform. 2 eqs. (24 mg, 0.076 mmol) of H
(
O
∧
N
)
C
6 [21] and 30 eqs. (0.06 mL, 0.9 mmol) of trimethylamine were added to the solution. The reaction mixture was stirred at reflux for 48 h. and at r.t. for 48 h. The solvent was evaporated and the organic phase extracted with dichloromethane/water and dried over sodium sulphate. The crude product was purified by precipitation from dichloromethane/cold ethanol. The solid was filtrated, washed with cold methanol, and dried under vacuum.Red-brown solid; yield 55% (53 mg), m.p. > 250°C;1H NMR (CDCl3, 300 MHz, TMS) δ
=
8.43 (d, J
=
9.09 Hz, 1H), 8.01 (d, J
=
9.24 Hz, 1H), 7.91 (s, 1H), 7.59 (d, J
=
7.62 Hz, 2H), 7.39 (d, J
=
8.49 Hz, 1H), 7.20 (d, J
=
9.39 Hz, 4H), 7.09–6.95 (m, 7H), 6.89–6.82 (m, 10H), 6.69 (d, J
=
9.3 Hz, 3H), 6.63 (d, J
=
8.07 Hz, 3H), 6.50 (d
d, J
=
8.43 Hz, J
=
2.2 Hz, 1H), 6.47 (d, J
=
3.09 Hz, 1H), 6.34 (d, J
=
8.49 Hz, 2H), 6.16 (d, J
=
8.07 Hz, 3H), 5.86 (d, J
=
2.05 Hz, 1H), 5.70 (d, J
=
2.07 Hz, 1H), 3.62 (s, 3H, –OCH3), 2.42 (m, 2H), 1.27 (m, 8H), 0.91 (t, J
=
6.6 Hz, 3H); FT-IR (KBr, cm−1): 1584, 1571, 1483, 1459, 1429, 1261, 1095, 1021, 865, 801, 751, 694; elemental analysis calculated for C70H58IrN5O2S2 (1257.59 g/mol): C 66.85%, H 4.65%, N 5.57%, found: C 66.90%, H 4.064%, N 5.59%.


### 5.5. Synthesis of ComplexIV

ComplexIV was prepared following the same procedure reported for complexIII with the following modifications: intermediate2 (96 mg, 0.048 mmol) and 2 eqs. of H
(
O
∧
N
)
t
p
a [18] (46 mg, 0.096 mmol) were treated with 30 eqs. of trimethylamine (86 mg, 1.44 mmol).Brown solid; yield: 51% (70 mg); m.p. > 250°C;1H NMR (CDCl3, 300 MHz, TMS) δ
=
8.44 (d, J
=
8.37 Hz, 1H), 8.05 (d, J
=
7.14 Hz, 1H), 7.98 (s, 1H), 7.61 (t, J
=
6.59 Hz, 3H), 7.41 (d, J
=
8.64 Hz, 2H), 7.20–6.80 (m, 36H), 6.72 (d, J
=
9.06 Hz, 4H), 6.52 (d, J
=
10.
83 Hz, 4H), 6.33 (t, J
=
9.33 Hz, 4H), 5.86 (d, J
=
2.19 Hz, 1H), 5.73 (d, J
=
1.53 Hz, 1H), 3.65 (s, 3H, –OCH3); FT IR (KBr, cm−1): 1572, 1526, 1490, 1460, 1386, 1268, 1172, 1144, 1067, 822, 751, 695, 509; elemental analysis calculated for C82H59IrN6O2S2 (1416.73 g/mol): C 69.52%, H 4.20%, N 5.93%, found: C 69.60%, H 4.30%, N 6.01%.


## 5.1. Synthesis of ComplexI

Intermediate complex1 [22] (150 mg, 0.14 mmol) was solubilized inca. 50 mL of a 1 : 1 mixture of acetone and chloroform. 2 eqs. of H
(
O
∧
N
)
C
6 [21] (87 mg, 0.28 mmol) and 30 eqs. (0.3 mL, 4.2 mmol) of trimethylamine were added to the solution. The reaction mixture was stirred at reflux for 72 h. The solvent was evaporated and the organic phase extracted with dichloromethane/water and dried over sodium sulphate. The crude product was purified by precipitation from dichloromethane/n-hexane. The solid was filtered off, washed with hexane, and dried under vacuum.Red solid; yield 66% (149 mg); m.p. > 250°C;1H NMR (300 MHz, CDCl3, 25°C, TMS) δ
=
8.92 (d, J
=
5.49 Hz, 1H), 8.86 (d, J
=
5.79 Hz, 1H), 8.05 (s, 1H), 7.88 (d, J
=
8.37 Hz, 1H), 7.67 (d, J
=
13 Hz, 1H), 7.68 (t, J
=
14 Hz, 1H), 7.59 (d, J
=
7.83 Hz, 1H), 7.51 (d, J
=
8.1 Hz, 1H), 7.12 (t, J
=
5.76 Hz, 1H), 7.06–7.00 (m, 2H), 6.95 (d
d, J
=
9.18 Hz, J
=
3.3 Hz, 1H), 6.85 (t, J
=
7.95 Hz, 1H), 6.72 (t, J
=
7.26 Hz, 1H), 6.65 (d, J
=
9.18 Hz, 1H), 6.57 (d, J
=
3.3 Hz, 1H), 6.51–6.49 (m, 4H), 6.28 (d, J
=
7.26 Hz, 1H), 6.17 (d, J
=
7.69 Hz, 1H), 6.02 (d, J
=
8.25 Hz), 3.71 (s, 3H), 2.35 (t, J
=
7.56 Hz, 2H), 1.67–1.22 (m, 8H), 0.93 (t, J
=
6.72 Hz, 3H, –OCH3); FT-IR (KBr, cm−1): 3041, 2996, 2925, 2853 (alkyl stretching), 1620 (CN Schiff base), 1604, 1584, 1476, 1465, 1425, 1314, 1212, 1147, 1030, 755, 729; elemental analysis calculated for C42H40IrN3O2 (811.00 g/mol): C 62.20%, H 4.97%, N 5.18%, found C 62.50%, H 5.14%, N 5.20%.


## 5.2. Synthesis of ComplexII

1 (100 mg, 0.09 mmol) was solubilized inca. 50 mL of a 1 : 1 mixture of acetone and chloroform. 2 eqs. of H
(
O
∧
N
)
t
p
a [18] (88 mg, 0.18 mmol) and 30 eqs. (0.2 mL, 2.8 mmol) of trimethylamine were added to the solution. The reaction mixture was stirred at reflux for 72 h. The solvent was evaporated and the organic phase extracted with dichloromethane/water and dried over sodium sulphate. The crude product was purified by precipitation from dichloromethane/hexane. The solid was filtered off, washed with n-hexane, and dried under vacuum.Red solid; yield 80% (145 mg); m.p. > 250°C;1H NMR (300 MHz, CDCl3, 25°C, TMS) δ
=
8.93 (d, J
=
5.34 Hz, 1H), 8.89 (d, J
=
5.49 Hz, 1H), 7.89 (d, J
=
8.1 Hz, 1H), 7.75–7.59 (m, 3H), 7.50 (d, J
=
8.1 Hz, 1H), 7.31–7.22 (m, 4H), 7.14–7.02 (m, 13H), 6.99–6.95 (m, 1H), 6.89–6.83 (m, 3H), 6.75–6.65 (m, 2H), 6.59 (d, J
=
3.18 Hz, 1H), 6.56–6.54 (m, 2H), 6.29 (d, J
=
7.68 Hz, 1H), 6.22–6.19 (m, 1H), 6.16 (d, J
=
8.25 Hz, 2H), 3.72 (s, 3H, –OCH3); FT-IR (KBr, cm−1): 3030, 2920, 2833 (alkyl stretching), 1610 (CN Schiff base), 1584, 1525, 1486, 1476, 1436, 1313, 1267, 1212, 1146, 1029, 823, 753, 729, 695; elemental analysis calculated for C54H41IrN4O2 (970.29 g/mol): C 66.85%, H 4.26%, N 5.78%, found: C 66.80%, H 4.14%, N 5.82%.


## 5.3. Synthesis of Intermediate Complex2

To a degassed aqueous solution (10 mL) of IrCl3·xH2O (93 mg, 0.25 mmol), 2 eqs. ofH(BzTh-tpa) [23] (200 mg, 0.50 mmol) solubilized in 30 mL of degassed ethoxyethanol is added. The reaction mixture was refluxed for 4 days under inert atmosphere (N2). A brown solid is filtered off and washed with distilled water and ethanol and dried under vacuum.Brown solid; yield 40% (96 mg); m.p. > 250°C;1H NMR (CDCl3, 300 MHz, TMS) δ
=
8.62 (d, J
=
6.0 Hz, 2H), 7.27 (d, J
=
1.23 Hz, 2H), 7.05–7.03 (m, 4H), 6.95–6.91 (m, 10H), 6.84–6.81 (m, 4H), 6.70–6.68 (m, 8H), 6.46 (d
d, J
=
8.45 Hz, J
=
2.04 Hz, 2H), 5.48 (d, J
=
2.19 Hz, 2H); FT-IR (KBr, cm−1): 1571, 1498, 1459, 1429, 1378, 1262, 1096, 1022, 802, 749, 694, 508; elemental analysis calculated for C50H34Cl2Ir2N4S2: C 49.54%, H 2.99%, N 4.62%, found: C 49.60%, H 3.04%, N 4.42%.


## 5.4. Synthesis of ComplexIII

Intermediate complex2 (75 mg, 0.038 mmol) was solubilized inca. 50 mL of a 1 : 1 mixture of acetone and chloroform. 2 eqs. (24 mg, 0.076 mmol) of H
(
O
∧
N
)
C
6 [21] and 30 eqs. (0.06 mL, 0.9 mmol) of trimethylamine were added to the solution. The reaction mixture was stirred at reflux for 48 h. and at r.t. for 48 h. The solvent was evaporated and the organic phase extracted with dichloromethane/water and dried over sodium sulphate. The crude product was purified by precipitation from dichloromethane/cold ethanol. The solid was filtrated, washed with cold methanol, and dried under vacuum.Red-brown solid; yield 55% (53 mg), m.p. > 250°C;1H NMR (CDCl3, 300 MHz, TMS) δ
=
8.43 (d, J
=
9.09 Hz, 1H), 8.01 (d, J
=
9.24 Hz, 1H), 7.91 (s, 1H), 7.59 (d, J
=
7.62 Hz, 2H), 7.39 (d, J
=
8.49 Hz, 1H), 7.20 (d, J
=
9.39 Hz, 4H), 7.09–6.95 (m, 7H), 6.89–6.82 (m, 10H), 6.69 (d, J
=
9.3 Hz, 3H), 6.63 (d, J
=
8.07 Hz, 3H), 6.50 (d
d, J
=
8.43 Hz, J
=
2.2 Hz, 1H), 6.47 (d, J
=
3.09 Hz, 1H), 6.34 (d, J
=
8.49 Hz, 2H), 6.16 (d, J
=
8.07 Hz, 3H), 5.86 (d, J
=
2.05 Hz, 1H), 5.70 (d, J
=
2.07 Hz, 1H), 3.62 (s, 3H, –OCH3), 2.42 (m, 2H), 1.27 (m, 8H), 0.91 (t, J
=
6.6 Hz, 3H); FT-IR (KBr, cm−1): 1584, 1571, 1483, 1459, 1429, 1261, 1095, 1021, 865, 801, 751, 694; elemental analysis calculated for C70H58IrN5O2S2 (1257.59 g/mol): C 66.85%, H 4.65%, N 5.57%, found: C 66.90%, H 4.064%, N 5.59%.


## 5.5. Synthesis of ComplexIV

ComplexIV was prepared following the same procedure reported for complexIII with the following modifications: intermediate2 (96 mg, 0.048 mmol) and 2 eqs. of H
(
O
∧
N
)
t
p
a [18] (46 mg, 0.096 mmol) were treated with 30 eqs. of trimethylamine (86 mg, 1.44 mmol).Brown solid; yield: 51% (70 mg); m.p. > 250°C;1H NMR (CDCl3, 300 MHz, TMS) δ
=
8.44 (d, J
=
8.37 Hz, 1H), 8.05 (d, J
=
7.14 Hz, 1H), 7.98 (s, 1H), 7.61 (t, J
=
6.59 Hz, 3H), 7.41 (d, J
=
8.64 Hz, 2H), 7.20–6.80 (m, 36H), 6.72 (d, J
=
9.06 Hz, 4H), 6.52 (d, J
=
10.
83 Hz, 4H), 6.33 (t, J
=
9.33 Hz, 4H), 5.86 (d, J
=
2.19 Hz, 1H), 5.73 (d, J
=
1.53 Hz, 1H), 3.65 (s, 3H, –OCH3); FT IR (KBr, cm−1): 1572, 1526, 1490, 1460, 1386, 1268, 1172, 1144, 1067, 822, 751, 695, 509; elemental analysis calculated for C82H59IrN6O2S2 (1416.73 g/mol): C 69.52%, H 4.20%, N 5.93%, found: C 69.60%, H 4.30%, N 6.01%.



---

*Source: 2856973-2016-01-06.xml*