Iridium(III) Complexes Bearing a Formal Tetradentate Coordination Chelate: Structural Properties and Phosphorescence Fine-Tuned by Ancillaries

Article abstract of DOI:10.1021/acs.inorgchem.9b02799

Synthesis of the multidentate coordinated chelate N3C-H₂, composed of a linked functional pyridyl pyrazole fragment plus a peripheral phenyl and pyridyl unit, was obtained using a multistep protocol. Preparation of Ir(III) metal complexes bearing a N3C chelate in the tridentate (κ³), tetradentate (κ⁴), and pentadentate (κ⁵) modes was executed en route from two nonemissive dimer intermediates [Ir(κ³-N3CH)Cl₂]₂ (1) and [Ir(κ⁴-N3C)Cl]₂ (2). Next, a series of mononuclear Ir(III) complexes with the formulas [Ir(κ⁴-N3C)Cl(py)] (3), [Ir(κ⁴-N3C)Cl(dmap)] (4), [Ir(κ⁴-N3C)Cl(mpzH)] (5), and [Ir(κ⁴-N3C)Cl(dmpzH)] (6), as well as diiridium complexes [Ir₂(κ⁵-N3C)(mpz)₂(CO)(H)₂] (7) and [Ir₂(κ⁵-N3C)(dmpz)₂(CO)(H)₂] (8), were obtained upon treatment of dimer 2 with pyridine (py), 4-dimethylaminopyridine (dmap), 4-methylpyrazole (mpzH), and 3,5-dimethylpyrazole (dmpzH), respectively. These Ir(III) metal complexes were identified using spectroscopic methods and by X-ray crystallographic analysis of representative derivatives 3, 5, and 7. Their photophysical and electrochemical properties were investigated and confirmed by the theoretical simulations. Notably, green-emitting organic light-emitting diode (OLED) on the basis of Ir(III) complex 7 gives a maximum external quantum efficiency up to 25.1%. This result sheds light on the enormous potential of this tetradentate coordinated chelate in the development of highly efficient iridium complexes for OLED applications.

Full text of DOI:10.1021/acs.inorgchem.9b02799

Article
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
pubs.acs.org/IC
Iridium(III) Complexes Bearing a Formal Tetradentate Coordination
Chelate: Structural Properties and Phosphorescence Fine-Tuned by
Ancillaries
†
,‡
§
§
∥
⊥
Yi Yuan, Premkumar Gnanasekaran, Yu-Wen Chen, Gene-Hsiang Lee, Shao-Fei Ni,
†
,‡,
†,§,
Chun-Sing Lee, * and Yun Chi *
†Department of Materials Science and Engineering, Department of Chemistry, City University of Hong Kong, Hong Kong SAR,
China
‡
Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Hong Kong SAR, China
§
Department of Chemistry and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua
University, Hsinchu 30013, Taiwan
∥
Instrumentational Center, National Taiwan University, Taipei 10617, Taiwan
⊥
Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, China
*
S Supporting Information
ABSTRACT: Synthesis of the multidentate coordinated chelate N3C−H ,
2
composed of a linked functional pyridyl pyrazole fragment plus a peripheral
phenyl and pyridyl unit, was obtained using a multistep protocol. Preparation
3
of Ir(III) metal complexes bearing a N3C chelate in the tridentate (κ ),
4
5
tetradentate (κ ), and pentadentate (κ ) modes was executed en route from
3
4
two nonemissive dimer intermediates [Ir(κ -N3CH)Cl ] (1) and [Ir(κ -
2
2
N3C)Cl] (2). Next, a series of mononuclear Ir(III) complexes with the
2
4
4
4
formulas [Ir(κ -N3C)Cl(py)] (3), [Ir(κ -N3C)Cl(dmap)] (4), [Ir(κ -N3C)-
Cl(mpzH)] (5), and [Ir(κ -N3C)Cl(dmpzH)] (6), as well as diiridium
complexes [Ir (κ -N3C)(mpz) (CO)(H) ] (7) and [Ir (κ -N3C)-
4
5
5
2
2
2
2
(
dmpz) (CO)(H) ] (8), were obtained upon treatment of dimer 2 with
2 2
pyridine (py), 4-dimethylaminopyridine (dmap), 4-methylpyrazole (mpzH),
and 3,5-dimethylpyrazole (dmpzH), respectively. These Ir(III) metal
complexes were identified using spectroscopic methods and by X-ray crystallographic analysis of representative derivatives 3,
5
, and 7. Their photophysical and electrochemical properties were investigated and confirmed by the theoretical simulations.
Notably, green-emitting organic light-emitting diode (OLED) on the basis of Ir(III) complex 7 gives a maximum external
quantum efficiency up to 25.1%. This result sheds light on the enormous potential of this tetradentate coordinated chelate in the
development of highly efficient iridium complexes for OLED applications.
4
,11−13
INTRODUCTION
been reported,
especially in the fabrication of OLED,
■
with performances comparable to those of metal phosphors
assembled using traditional bidentate chelates. It should be
further emphasized that there is also a class of Ir(III)
phosphors with two tridentate chelates, i.e., the so-called bis-
A great deal of current research has been focused on both the
designs and applications of emissive, third-row transition metal
complexes bearing various bidentate and multidentate
1
−9
coordination chelates.
In contrast to the complexes bearing
14−17
tridentate Ir(III) phosphors,
and it has showed great
only bidentate chelates, it is believed that the multidentate
chelates are capable of increasing the ligand field stabilization
energy and inhibiting chelate dissociation, affording emitters
with higher emission quantum efficiency and enhanced
stability under severe conditions. Given the wide application
of transition-metal-based emitters in the fabrication of organic
light-emitting diodes (OLED), particular emphasis has been
placed on elucidating the roles these multidentate chelates may
play in improving the photophysical properties and on how
promise for OLED fabrication due to both the higher rigidity
and stability imposed by their dual tridentate framework.
Hence, the surge in employing multidentate chelate has led
to the design of tetradentate chelate and the preparation of
18−22
emissive Ir(III) or Pt(II) metal phosphors.
Furthermore,
tetradentate chelates, in comparison to the tridentate chelate of
octahedral complexes, are anticipated to have an even better
capability in encapsulating the central metal ion and forming
10
they are going to affect the chemistry and reactivity. Among
the plethora of molecular designs, a large variety of Ir(III) and
Pt(II) phosphors bearing at least one tridentate chelate have
Received: September 19, 2019
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.9b02799
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Inorganic Chemistry
Article
well-defined environments. Hence, they have been thoroughly
designed N3C−H chelate would act as the dianionic chelate,
2
examined for fundamental studies to serve as the durable
which is in sharp contrast to the monoanionic behavior
exhibited by N4−H, not to mention that the cyclometalation
requires a higher activation barrier as well as the production of
distinctive intermediate species. Hence, we are interested in
probing the structure−property relationship of relevant Ir(III)
complexes. After that, we are also interested in studying the
mechanistic information en route to the isolation of novel
diiridium dihydride complexes, via pyrazole coordination in
the presence of K CO . Eventually, the removal of the
23
template in the construction of redox mediators or catalysts
24−28
for the activation of small molecules.
However, as for the
application in making emissive metal complexes, it is essential
to introduce some conjugated segment into the chelate
backbone to allow systematic fine-tuning of the ππ* energy
gap and emission hue. To account for this requirement,
porphyrin-based chelates were known to afford red to NIR-
emitting Ir(III) complexes, such as Ir-OEP-Py , due to the
2
2
3
29
extended conjugation (Chart 1). A second example involved
remaining chloride and monodentate N-donor have produced
the metal complexes with much enhanced photoluminescence.
Chart 1. Structural Drawings of Ir-OEP-Py and (A)
2
RESULTS AND DISCUSSION
Syntheses and Characterization. The dianionic chelate
■
N3C−H described in this paper was prepared using 1-phenyl-
2
1
-(pyridin-2-yl)ethane (L1), which was obtained by direct
methylation of commercially available 2-benzylpyridine
(
Scheme 1). Independently, 2-bromo-6-(2-methyl-1,3-dioxo-
a
Scheme 1. Synthesis of Tetradentate Chelate N3C−H2
a series of Ir(III) complexes represented by (A), with a planar
tetradentate chelate and two axial ancillaries, which has been
applied in making the solution-processed red-emitting OLED
30
devices with an external quantum efficiency (EQE) of 10.5%.
Moreover, a distinctive facially arranged tetradentate 2,2′-(1-
6-(3-trifluoromethyl-1H-pyrazol-5-yl)pyridin-2-yl)ethane-1,1-
(
3
1
diyl)dipyridine chelate (e.g., N4−H in Chart 2) was also
Chart 2. Structural Drawings of Two Tetradentate Chelates
a
Experimental conditions: (i) n-BuLi, MeI, THF, −78 °C. (ii) n-BuLi,
N4−H and N3C−H and Ir(III) Metal Complex
2
2-bromo-6-(2-methyl-1,3-dioxolan-2-yl)pyridine, THF, −78 °C. (iii)
HCl, H O, reflux. (iv) NaOEt, CF CO Et, THF, reflux. (v) N H ·
H O, conc HCl, EtOH, reflux.
[
Ir(N4)(bipz)]
2
3
2
2
4
2
lan-2-yl)pyridine was prepared from the treatment of 2,6-
dibromopyridine with n-BuLi, followed by the addition of
dimethylacetamide and the protection of the acetyl group by
treatment with ethylene glycol in the presence of p-
toluenesulfonic acid. After that, the coupling of 1-phenyl-1-
(
2
pyridin-2-yl)ethane with 2-bromo-6-(2-methyl-1,3-dioxolan-
-yl)pyridine, followed by acid catalyzed hydrolysis, afforded
the key intermediate 1-(6-(1-phenyl-1-(pyridin-2-yl)ethyl)-
pyridin-2-yl)ethan-1-one (L4) in good yield. Finally, con-
densation of L4 with ethyl trifluoroacetate, followed by
hydrazine cyclization, afforded the desired tetradentate chelate
successfully obtained and put in the preparation of emissive
Ir(III) metal complexes. Unlike its planar counterpart, this
class of chelate would retain a pair of vacant cis-coordination
sites for accommodating a bidentate chelate, giving Ir(III)
complexes with a novel 4 + 2 architecture. This chemical
transformation was evidenced by the addition of di-
(N3C−H ). The corresponding synthetic protocol is depicted
2
in Scheme 1.
Next, this tetradentate chelate N3C−H was reacted with an
2
(
trifluoromethyl)-3,3′-bipyrazolate giving a charge-neutral,
iridium reagent IrCl ·3H O using a two-step coordination
3
2
3
1
sky-blue emitting Ir(III) complex [Ir(N4)(bipz)].
pattern. These manipulations led to the isolation of two
3
Herein, we present the structural design and characterization
of emissive Ir(III) complexes composed of a new class of
tetradentate chelate, which differs from previously reported
N4−H by replacing one peripheral pyridine with a phenyl
substituent, giving 2-(3-trifluoromethyl-1H-pyrazol-5-yl)-6-(1-
distinctive Ir(III) complexes, [Ir(κ -N3CH)Cl ] (1) and
2
2
4
[Ir(κ -N3C)Cl] (2), from reactions conducted either in
2
mixed 2-methoxyethanol (bp = 124 °C) and water or in
refluxing diethylene glycol monomethyl ether (DGME, bp =
194 °C), respectively. The key data to their assignment is
1
phenyl-1-(pyridin-2-yl)ethyl)pyridine, cf. N3C−H in Chart 2.
provided by their H NMR spectra, which exhibited a total of
2
This tetradentate chelate is expected to impose a large
alternation in electronic properties, as the phenyl group
would engage in cyclometalation rather than simple coordina-
tion as expected for a pyridyl group. Moreover, this newly
13 and 12 proton signals in the aromatic region, together with
a distinctive high-field methyl signal at δ 2.25 and δ 2.82 of
N3C chelate. The spectral pattern also confirmed the presence
of a free rotating phenyl appendage in 1 in solution and a
B
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rigidified cyclometalate phenyl group of the second dimer
intermediate 2. Besides, only the powders can be obtained for
both complexes, despite multiple attempts in conducting
crystallization and with distinctive solvents, which hampered
characterization using single crystal X-ray diffraction analysis.
This could be due to the existence of two possible isomers in
forming the proposed dimer complexes, i.e., cis and trans
forms, in both solution and solid states. However, only the
structural drawings of the trans isomer are depicted in Chart 3
for conveying our assignments.
Figures 1 and 2, both molecules exhibit a slightly distorted
octahedral arrangement around the iridium atom with the
Chart 3. Drawings of Dimeric Intermediates 1 and 2 in
Trans Arrangement
Figure 1. Structure of 3 with thermal ellipsoids shown at the 40%
probability, Ir−C(1) = 2.005(4), Ir−N(1) = 2.007(3), Ir−N(2) =
2
2
.021(3), Ir−N(4) = 2.045(3), Ir−N(5) = 2.067(3), and Ir−Cl(1) =
.4982(9) Å. Selected bond angles: N(2)−Ir−N(4) = 169.44(12),
N(1)−Ir−N(5) = 175.24(12), and C(1)−Ir−Cl(1) = 173.35(11)°.
Relevant diiridium metal complexes with bridged chloride
ligands were known to undergo facile addition of the donor
3
2−36
group to afford the mononuclear metal complexes;
hence,
the diiridium metal complex 2 should be of no exception. To
confirm this speculation, we attempted the reactions with
various nitrogen donors, namely, pyridine (py), 4-dimethyla-
minopyridine (dmap), 4-methylpyrazole (mpzH), and 3,5-
dimethylpyrazole (dmpzH) from which we obtained mono-
4
nuclear Ir(III) complexes, namely, [Ir(κ -N3C)Cl(py)] (3),
4
4
[
[
Ir(κ -N3C)Cl(dmap)] (4), [Ir(κ -N3C)Cl(mpzH)] (5), and
4
Ir(κ -N3C)Cl(dmpzH)] (6) in moderate yields (cf. Chart 4).
The initial identification was provided by their FD MS data
+
1
that exhibited the anticipated molecular ion (M ) and their H
NMR spectra with all proton signals for both the N3C chelate
and added nitrogen donor in a 1:1 ratio.
Single crystal X-ray diffraction studies on 3 and 5 were next
conducted to reveal their structural characteristics. As shown in
Chart 4. Drawings of Mononuclear Ir(III) Complexes 3−6
Figure 2. Structure of 5 with thermal ellipsoids shown at the 40%
probability, Ir−C(1) = 2.015(5), Ir−N(1) = 2.047(4), Ir−N(2) =
2
.005(4), Ir−N(3) = 2.012(4), Ir−N(5) = 2.052(4), and Ir−Cl(1) =
.4658(13) Å. Selected bond angles: N(1)−Ir−N(3) = 167.50(16),
2
N(2)−Ir−N(5) = 173.34(17), and C(1)−Ir−Cl(1) = 174.24(15)°.
4
N3C chelate adopting the anticipated tetradentate κ -mode.
The pyrazolate-to-central pyridine unit is slightly bent away
from planarity to allow the coordination of peripheral phenyl
and pyridyl units. Overall, the three N atoms of N3C chelates
are arranged in the meridional mode, while the phenyl
appendage is located at the axial site vs the plane defined by
the meridional arranged N atoms and is located at the trans
disposition to the unique chloride, leaving the monodentate N
donor to occupy the remaining coordination site that is trans
to the central pyridine unit of N3C chelate. The unique Ir−C
distances of 2.005(4) Å in 3 and 2.015(5) Å in 5 are similar to
37
the reported Ir−C bond distances trans to the chloride, while
C
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Inorganic Chemistry
Article
the py and mpzH ligands of 3 and 5 exhibited the longest Ir−
N distances within each molecule, i.e., 2.067(3) and 2.052(4)
Å, which could be due to the strong trans influence exerted by
the central pyridine unit of the N3C chelate, which exhibited
the shortest Ir−N distance, i.e., 2.007(3) and 2.005(4) Å.
Finally, the monodentate pyridine in 3 is rotated along the N−
Ir vector by ∼45° for minimizing steric interaction to the
nearby pyrazolate fragment of the N3C chelate. In sharp
contrast, the mpzH ligand in 5 is aligned parallel to this
pyrazolate to allow for the formation of interligand H-bonding,
i.e., with N(4)···H(6)−N(6) contact of 1.990 Å. This
observation is also consistent with the downfield-shifted
1
pyrazolic proton signal at δ 14.20 in its H NMR spectrum
recorded in CD Cl solvent at room temperature (RT).
2
2
We next conducted the reaction of 2 with pyrazoles under
basic conditions, with an anticipation that the pyrazolate is
capable of replacing the chloride anion, giving dinuclear
38−47
complexes connected with two bridging pyrazolates.
To
our surprise, when the mixture of 2, mpz/dmpz (8 equiv), and
K CO (5 equiv) was refluxed in DGME for 12 h, these
2
3
Figure 3. Structure of 7 with thermal ellipsoids shown at the 40%
probability, Ir(1)−C(1) = 2.025(5), Ir(1)−N(1) = 2.039(4), Ir(1)−
N(2) = 2.032(4), Ir(1)−N(3) = 2.029(4), Ir(1)−N(5) = 2.158(4),
Ir(1)−N(7) = 2.036(4), Ir(2)−C(31) = 1.823(7), Ir(2)−N(4) =
reactions went in a different direction and afforded the
5
diiridium metal complexes [Ir (κ -N3C)(mpz) (CO)(H) ]
2
2
2
5
(
7) and [Ir (κ -N3C)(dmpz) (CO)(H) ] (8) as shown in
2 2 2
1
Chart 5, for which their H NMR spectra exhibited two
2
.210(4), Ir(2)−N(6) = 2.106(4), Ir(2)−N(8) = 2.137(4), Ir(2)−
H(2A) = 1.52(6), and Ir(2)−H(2B) = 1.547(10) Å. Selected bond
Chart 5. Structural Drawings of Diiridium Complexes 7 and
8
angles: N(1)−Ir1−N(3) = 166.48(17), N(2)−Ir1−N(7) =
1
=
71.23(17), N(5)−Ir1−C(1) = 177.68(18), and N(6)−Ir2−C(31)
172.3(2)°.
Ir(2) metal center. The three remaining coordination sites on
Ir(2) are next occupied by two cis-arranged hydrides and a
terminal carbonyl. Other metric parameters within this
molecule are normal and unremarkable.
As for a possible reaction pathway, the hydrides of both 7
and 8 may be derived from the hydroxyl group of a protic
solvent employed in the present studies, for which the
employed conditions are akin to many transformations
51,52
documented in the literature.
We have also tried to
hydride signals at δ −16.70 and δ −19.73 and δ −16.66 and δ
confirm this possibility by using isotope tracing, i.e., the
−
19.75 and IR spectra displayed a characteristic ν(CO)
addition of D O into the reaction mixture. However, the
2
−
1
stretching band at 2011 and 2007 cm , respectively. For the
introduction of a small amount of D O has failed to
2
1
hydride signals in H NMR spectra, one appears as a doublet
incorporate enough deuteride in the final product, but too
2
with J of ∼8.3 Hz, which is caused by the mutual coupling
much D O caused a complete suppression of product
HH
2
of cis-oriented hydrides, while the second multiplet, with an
formation, giving no answer to their origins. On the contrary,
the carbonyl group of both 7 and 8 is attributed to the added
K CO catalyst. As shown in Figure S1, in contrast to the
5
additional, smaller coupling constant of J = ∼3.8 Hz, is
HF
attributed to the long-range (or through space) coupling to an
2
3
adjacent CF substituent. Since this spectroscopic information
formation of diiridium complex 7 with only one ν(CO)
stretching band at 2011 cm , the addition of 10 and 25 equiv
3
−
1
cannot unambiguously identify their molecular arrangements, a
single crystal X-ray structural determination on 7 was next
conducted to decipher their exact structure.
1
3
of C-isotope enriched K CO afforded diiridium complex 7
2
3
−
1
with an additional ν(CO) stretching signal at 1965 cm .
Hence, some of the carbonate ion dissolved in the reaction
media has been reduced by forming carbon monoxide in the
reaction media and, eventually, participating in the formation
of the diiridium products. Moreover, the heating of Ir(III)
complexes 5 and 6 with a corresponding pyrazole in the
presence of K CO also afforded the diiridium complexes 7
The single crystal X-ray structural analysis on 7 depicted the
existence of two crystallographically independent, but
structurally similar, molecules within the unit cells. Figure 3
shows one molecular drawing of these molecules, which
5
consists of one pentacoordinated κ -N3C chelate spanning
across two octahedral arranged Ir(III) metal centers. The first
2
3
4
Ir(1) metal atom interacts with the N3C chelate using the κ -
and 8 in lower yields, which confirmed the possible
intermediacy of mononuclear 5 and 6 while the lower yields
reflected the demand of a second Ir(III) metal fragment en
route to the formation of diiridium complexes 7 and 8.
Photophysical Properties. The diiridium complexes 1
and 2 are essentially nonemissive in both solution and solid
states, and hence, only the photophysical data of Ir(III)
mode, while the remaining cis-coordination sites are bridged by
two mpz chelates. These three pyrazolate chelates, one from
N3C and two from mpz anions, formed a facially coordinated
tridentate ensemble, in a manner related to that of the well-
established tris-pyrazolyl borate chelates known to the
48−50
coordination chemistry,
and interacted with the second
D
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Article
complexes 3−8 were recorded and depicted in Figure 4, while
The oxidation and reduction potentials of 3−8 were
measured by cyclic voltammetry, to which the data and
corresponding voltammograms were depicted in Table 1 and
Figure S3. As can be seen, all mononuclear complexes 3−6
showed a quasi-reversible, metal-centered oxidation process,
for which those with a more electron donating nitrogen donor,
i.e., dmap vs py and dmpzH vs mpzH, displayed a slight
shifting of potential to a less positive region, confirming the
metal-centered oxidation process. Moreover, dmap-substituted
complex 4 exhibited the least positive oxidation potential
among all complexes, which could be due to the strongest
electron donating effect exerted by the dimethylamino group
of dmap ligand. On the contrary, the oxidation peak profile of
diiridium complexes 7 and 8 turned irreversible and underwent
a slight cathodic shifting at the same time, making the
corresponding electrochemistry distinctive from their mono-
nuclear counterparts 3−6. This result echoes the large
distinction between mononuclear and diiridium metal
complexes. Finally, their HOMO/LUMO energy levels were
calculated to be −5.68/−2.29, −5.52/−2.26, −5.65/−2.39,
their numeric data were summarized in Table 1. In general, all
Figure 4. UV−vis absorption and emission of Ir(III) complexes in
−
5
CH Cl solution at 10 M at RT.
2
2
−
5.64/−2.28, −5.62/−2.37, and −5.54/−2.39 eV for
complexes 3−8, respectively, according to the equation of
higher energy absorption peaks (≤400 nm) with higher
excitation coefficients in UV−vis spectra are attributed to the
intraligand charge transfer (ILCT) transition of tetradentate
HOMO/LUMO = −(E /E + 4.8) eV.
ox red
Theoretical Investigations. Density functional theory
(DFT) and time-dependent DFT (TDDFT) calculations were
performed on Ir(III) complexes 3, 5, and 7 in order to
decipher their photophysical and electrochemical character-
istics. As depicted in Figure 5, both complexes 3 and 5, bearing
a monodentate py and a mpzH ligand, have similar HOMO
distributions, with electron clouds mainly located on the
central iridium atom, chloride, and both pyrazolate and phenyl
4
κ -N3C chelate. Moreover, the strong absorption of 4 at
approximately 298 nm originates from the charge transfer
absorption of coordinated 4-dimethylaminopyridine. Finally,
the absorptions at ∼420 nm and their shoulder in the lower
energy region ≥470 nm are attributed to both the spin allowed
and forbidden metal-to-ligand charge transfer (MLCT)
transition.
4
rings of κ -N3C chelate. However, the location of the LUMO
As for the emission, all studied Ir(III) complexes showed a
broadened, structureless profile with a peak maximum between
is slightly different, for which the electron cloud of 3 is spread
4
over the entire κ -N3C chelate except for the phenyl ring,
4
80−505 nm for Ir(III) complexes 3−6 and at 524 and 536
while for complex 5, the LUMO showed little contribution
from the mpzH ancillary, probably due to both the slightly
stronger donor strength and the reduced π-conjugation. For
the diiridium complex 7, the HOMO is mainly localized on the
Ir(1) atom (as defined in single crystal X-ray structural
nm for diiridium complexes 7 and 8, respectively. It is notable
that complexes 3−6 exhibited poor emission quantum yields
(
QY), which are due to the fast nonradiative process exerted
by both the weak-field chloride ligand and monodentate
nitrogen donor. In sharp contrast, the diiridium complexes 7
and 8 exhibited much higher QY due to the absence of
chloride and the possession of two bridging pyrazolates; the
latter would allow a significantly reduced rotational freedom in
solution in comparison to the case for the monodentate
coordinated pyridines or pyrazoles.
Thermal and Electrochemical Properties. The thermal
properties of the titled complexes 3−8 were evaluated by
thermal gravimetric analysis under a nitrogen atmosphere. As
depicted in Figure S2, the decomposition temperature with a
5
analysis), the phenyl ring of the κ -N3C chelate, and two
bridging mpz anions, while the LUMO is primarily dispersed
5
over the pyrazolate and both pyridyl fragments of the κ -N3C
chelate as well as the central Ir(1) atom.
Besides, complexes 3, 5, and 7 exhibited the HOMO levels
of −5.78, −5.77, and −5.76 eV, respectively, which are
consistent with their CV data (Figure S3 and Table 1). The
associated electronic transitions and emission wavelengths are
next calculated on the basis of their optimized S geometries.
0
5
2
% weight loss for complexes 3−8 was recorded in the range
As depicted in Table S1, the calculated S → S transition
wavelengths for 3 (379.3 nm), 5 (379.74 nm), and 7 (380.18
0
1
87−389 °C, indicating their good thermal stability.
Table 1. Photophysical and Electrochemical Data of the Studied Ir(III) Metal Complexes
abs λ [nm] (ε × 10− M−1 cm−1
4
)
a
λmax (nm)
a
Φ (%)
a
τobs (μs)
a
kr (s−1)
knr (s−1
)
Eox [V]
b
Ered [V]
b
3
4
5
6
7
8
294 (2.12), 326 (1.44), 353 (1.07)
273 (3.11), 298 (3.25), 364 (1.03)
292 (1.95), 320 (1.17), 358 (0.83)
295 (1.95), 319 (1.19), 362 (0.84)
299 (1.72), 365 (0.76), 436 (0.23)
305 (1.16), 381 (0.49), 440 (0.19)
480
496
495
504
524
536
0.86
1.5
1.2
1.2
75
0.011
0.041
0.032
0.014
5.96
7.8 × 105
3.7 × 105
3.8 × 105
8.6 × 105
1.3 × 10
1.0 × 105
9.0 × 107
2.4 × 107
3.1 × 107
7.1 × 107
4.2 × 10
4.0 × 104
0.88
0.72
0.85
0.84
0.82
0.74
−2.51
−2.54
−2.41
−2.52
−2.43
−2.41
5
4
72
6.96
a
−5
b
UV−vis spectra, PL spectra, and lifetime and quantum yields were recorded in CH Cl at a concentration of 10 M at RT. The oxidation and
2
2
reduction potentials were recorded in CH Cl and THF, respectively.
2
2
E
DOI: 10.1021/acs.inorgchem.9b02799
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 5, the negative regions were mainly localized over the
central Ir(III) atom and the N3C chelate, and partially on the
chloride and monodentate ligands, while the positive areas
were distributed over the N3C chelate, indicating the mixed
charge transfer transition characteristics.
Fabrication of OLED Devices. Given its high phosphor-
escence quantum yield, diiridium complex 7 is selected as a
representative dopant emitter to investigate its electro-
luminescent (EL) performance. Thus, the OLEDs with an
architecture of indium tin oxide (ITO)/1,1-bis[4-[N,N′-di(p-
tolyl)amino]phenyl]cyclohexane (TAPC, 50 nm)/10 wt % 7
doped in 4,4′,4″-tris(N-carbazolyl)-triphenylamine (TCTA, 20
nm)/3,3′-(5′-(3-(pyridin-3-yl)-phenyl)-[1,1′:3′,1″-terphenyl]-
3,3″-diyl)dipyridine (TmPyPB, 50 nm)/LiF (1 nm)/Al (120
nm) was fabricated. Doped TCTA constituted the light-
emissive layer (EML), while TAPC and TmPyPB served as the
hole-transporting and electron-transporting layers, respectively.
As shown in Figure 6, this device gives bright green emission
with a peak maximum at 530 nm and CIE 1931 chromaticity
coordinates of (0.34, 0.59). The EL spectrum is essentially
identical to its solution PL spectrum and free from the TCTA
host emission and others, indicating the efficient energy
transfer and exciton confinement within the EML. As shown in
the current density−voltage−luminance (J−V−L) curve, this
device exhibited a small charge injection barrier by giving low
Figure 5. Contours and energy levels of the frontier molecular orbitals
in the optimized S state and the electron density difference maps for
0
Ir(III) complexes 3, 5, and 7, to which the blue and green contours of
EDD maps represent the decrease and increase of the electron density
upon excitation, respectively.
−2
turn-on voltage of <3.5 V at a brightness of 1 cd m . Figure 6b
shows the device efficiency at different current densities, for
which an excellent performance with a maximum current
efficiency of 81.7 cd A and external quantum efficiency of
nm) are qualitatively akin to the lowest energy absorption band
−1
(
5
Figure 4). The T → S transition energy was calculated to be
10.47, 574.21, and 585.41 nm for 3, 5, and 7, respectively,
1 0
2
5.1% were obtained. Moreover, upon an increase in the
−
2
luminance to 1000 cd m , its EQE remains as high as 20%.
These device performances are much better than our previous
report on the Ir(III) emitter bearing tetradentate N4 chelate,
showing the same trend to the observed phosphorescence as
revealed in Figure 4. As for their assignment, the S → S and
0
1
31
S → T transitions are both dominated by HOMO−1 →
0
1
albeit with a much red-shifted emission wavelength. Unfortu-
nately, like most reported phosphorescent OLED devices, as
the luminance or current density is further increased, the
efficiency dropped rapidly, which can be explained by triplet−
triplet annihilation caused by the relatively long lifetime of
Ir(III) dopant 7. Further optimization targeted at increasing
the optical bandgap of the N3C-based Ir(III) complex is under
way.
LUMO for 3 and HOMO → LUMO for 7, respectively, and
are changed to HOMO → LUMO and HOMO−1 → LUMO
processes for 5. Also, as depicted in Table S1, their lowest
triplet excited states showed mixed MLCT, ILCT, and ligand-
to-ligand charge transfer (LLCT) characters. To obtain a clear
orbital representation, we applied the electron density
difference (EDD) maps to visualize the electronic transition
that constituted the lowest triplet excited states. As exhibited in
Figure 6. (a) Current density−voltage−luminance (J−V−L) characteristics and (b) efficiency versus current density plots for complex-7-based
OLEDs (inset: EL spectra at 4.5 V).
F
DOI: 10.1021/acs.inorgchem.9b02799
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
7
.88 (m, 2H), 7.56 (t, J = 5.2 Hz, 1H), 7.53 (d, J = 6.2 Hz, 1H), 7.43
CONCLUSION
■
(
6
d, J = 6.3 Hz, 1H), 7.07 (t, J = 6.0 Hz, 1H), 6.98 (t, J = 5.9 Hz, 1H),
.78 (s, 1H), 2.82 (s, 3H). F NMR (376 MHz, CD Cl , 298 K): δ
In summary, we designed and synthesized a potentially
tetradentate coordinated chelate, namely, 2-(3-trifluorometh-
yl-1H-pyrazol-5-yl)-6-(1-phenyl-1-(pyridin-2-yl)ethyl)pyridine
19
2 2
+
−
60.45 (s, 3F). FD MS: m/z 1205.1 (M − Cl). Anal. Calcd for
C H Cl F Ir N : C, 42.62; H, 2.44; N, 9.04. Found: C, 42.35; H,
4
4
30
2
6
2
8
(
N3C−H ). A series of mononuclear and diiridium metal
2.24; N, 9.59.
2
4
complexes were next obtained with the N3C chelate, showing a
Preparation of [Ir(κ -N3C)Cl(py)] (3). A mixture of 2 (300 mg, 0.24
mmol) and pyridine (py, 153 mg, 1.93 mmol) in 40 mL of DGME
was refluxed for 14 h. After it cooled to RT, the solvent was removed
3
metal−ligand bonding mode varying from a κ -mode in dimer
4
1
to a κ -mode in both dimer 2 and mononuclear Ir(III)
5
and the residue was taken into CH
Cl , washed with water, dried over
2 2
complexes 3−6 and finally to a κ -mode in diiridium
complexes 7 and 8, respectively. The mechanistic pathways
that give these Ir(III)-based metal complexes were unambig-
uously clarified. Except for dimer complexes 1 and 2, which are
essentially nonemissive, other newly synthesized mononuclear
complexes 3−6 and diiridium complexes 7 and 8 exhibited
bright sky-blue to green emissions with a peak wavelength
spanning 480−536 nm. More importantly, the removal of the
chloride and monodentate ancillary produced the diiridium
complexes 7 and 8 with much enhanced emission efficiency.
Therefore, the green OLEDs incorporating 7 as the dopant
emitter achieved excellent performance with an emission peak
maximum located at 530 nm and with a maximum EQE of
Na SO , filtered, and concentrated to dryness. It was purified by silica
2
4
gel column chromatography (CH Cl and ethyl acetate = 3:1) to
2
2
4
afford light-yellow solid [Ir(κ -N3C)Cl(py)] (3, 140 mg, 41%).
1
Spectral data of 3. H NMR (500 MHz, DMSO-d , 373 K): δ 8.62
6
(s, 2H), 8.17−8.02 (m, 4H), 7.95 (t, J = 7.9 Hz, 1H), 7.78 (d, J = 7.6
Hz, 1H), 7.67 (d, J = 7.8 Hz, 1H), 7.54 (t, J = 6.7 Hz, 2H), 7.35 (d, J
= 7.7 Hz, 1H), 7.29 (t, J = 6.1 Hz, 1H), 7.15 (s, 1H), 6.88 (t, J = 7.3
Hz, 1H), 6.82 (d, J = 7.1 Hz, 1H), 6.68 (t, J = 7.2 Hz, 1H), 2.66 (s,
1
9
3
H). F NMR (471 MHz, DMSO-d , 373 K): δ −58.50 (s). FD MS:
6
+
m/z 699.0 (M ). Anal. Calcd for C H ClF IrN : C, 46.38; H, 2.88;
2
7
20
3
5
N, 10.02. Found: C, 46.73; H, 2.57; N, 9.81.
Selected X-ray structural data of 3: C H Cl F IrN ; M = 784.08;
2
8
22
3
3
5
̅
triclinic; space group = P1, a = 9.5645(3) Å, b = 12.3522(4) Å, c =
1
4.4243(4) Å; α = 107.7491(9)°, β = 97.3463(9)°, γ = 104.0035(9)°;
−
1
3
−3
2
5.1% and luminescence of 81.7 cd A . Hence, our study
V = 1536.83(8) Å ; Z = 4; ρ
crystal size = 0.135 × 0.127 × 0.088 mm ; T = 150 (2) K; μ = 4.649
= 1.690 Mg·m ; F(000) = 756;
calcd
3
presents a new approach in designing efficient iridium-based
phosphors for OLED applications.
−
1
mm ; 14049 reflections collected, 7044 independent reflections (Rint
0.0154), max and min transmission = 0.7456 and 0.6324; restraints/
=
parameters = 25/383, GOF = 1.117, final R [I > 2σ(I)] = 0.0262 and
1
EXPERIMENTAL SECTION
■
wR (all data) = 0.0721; largest diff peak and hole = 1.760 and −0.914
2
−
3
General Information and Materials. All reactions were
performed under a nitrogen atmosphere. Solvents were distilled
from appropriate drying agents prior to use. Commercially available
reagents were used without further purification. Mass spectra were
obtained on a JEOL AccuTOF GCX instrument operating in field
e·Å .
4
Preparation of [Ir(κ -N3C)Cl(dmap)] (4). A mixture of 2 (500 mg,
0.40 mmol) and 4-dimethylaminopyridine (dmap, 390 mg, 3.2 mmol)
in 40 mL of DGME was refluxed for 14 h. After it cooled to RT, the
solvent was removed and the residue was taken into CH Cl , washed
2
2
1
19
desorption (FD) mode. H and F NMR spectra were obtained using
the Varian Mercury-400 and -500 NMR instruments. Elemental
analyses were performed using the Elementar Vario EL III CHN-O
rapid elementary analyzer. Steady-state absorption and emission
spectra were recorded by a Hitachi (U-3900) spectrophotometer and
an Edinburgh (FLS920) fluorometer, respectively. To determine the
photoluminescence quantum yield in solution, the samples were
degassed by three freeze−pump−thaw cycles. All electrochemical
potentials were measured in a 0.1 M TBAPF /CH Cl solution for
with water, dried over Na SO , filtered, and concentrated to dryness.
2 4
It was purified by silica gel column chromatography (CH Cl and
2
2
4
ethyl acetate = 3:1) to afford light-yellow [Ir(κ -N3C)Cl(dmap)] (4,
300 mg, 46%).
1
Spectral data of 4. H NMR (500 MHz, DMSO-d , 373 K): δ 8.30
6
(d, J = 5 Hz, 1H), 8.07−8.02 (m, 4H), 7.91 (t, J = 7.9 Hz, 1H), 7.74
(d, J = 7.5 Hz, 1H), 7.63 (d, J = 7.9 Hz, 1H), 7.34−7.26 (m, 2H),
7.12 (s, 1H), 6.98 (dd, J = 7.4, 1.2 Hz, 1H), 6.89−6.84 (m, 1H), 6.68
1
9
(dd, J = 10.9, 3.9 Hz, 3H), 3.08 (s, 6H), 2.64 (s, 3H). F NMR (471
6
2
2
oxidation and THF for reduction reaction and were reported in volts
MHz, DMSO-d , 373 K): δ −58.35 (s). FD MS: m/z 742.1 (M +
6
+
+
using Fc/Fc as the reference; ΔE is defined as E (anodic peak
H ). Anal. Calcd for C H ClF IrN : C, 46.93; H, 3.40; N, 11.32.
p
pa
29 25
3
6
potential) − E (cathodic peak potential), and these data are quoted
Found: C, 47.11; H, 3.37; N, 11.32.
pc
4
in millivolts. Platinum and gold wires were selected as the cathode
and anode of electrochemical measurements, respectively.
Preparation of [Ir(κ -N3C)Cl(mpzH)] (5). A mixture of 2 (500 mg,
0.40 mmol) and 4-methylpyrazole (mpzH, 270 mg, 3.2 mmol) in 40
mL of DGME was refluxed for 14 h. After it cooled to RT, the solvent
was removed and the residue was taken into CH Cl , washed with
3
Preparation of [Ir(κ -N3CH)Cl ] (1). A mixture of IrCl ·3H O
2
2
3
2
(
2
200 mg, 0.57 mmol) and N3C−H (0.22 g, 0.56 mmol) in 30 mL of
-methoxyethanol and 10 mL of water was refluxed for 12 h. After it
2
2
2
water, dried over Na SO , filtered, and concentrated to dryness. It was
2 4
cooled to RT, the resulting precipitate was collected and washed with
purified by silica gel column chromatography (CH Cl and ethyl
2 2
acetate = 3:1) to afford light-yellow [Ir(κ -N3C)Cl(mpzH)] (5, 260
4
ethanol and diethyl ether to afford light-yellow solid 1 (290 mg, 76%).
1
Spectral data of 1. H NMR (400 MHz, DMSO-d , 298 K): δ 10.57
mg, 46%).
6
1
(
7
d, J = 5.8 Hz, 1H), 7.86 (d, J = 7.6 Hz, 1H), 7.68 (t, J = 7.5 Hz, 1H),
.61 (t, J = 7.9 Hz, 1H), 7.40 (m, 4H), 7.33−7.27 (m, 2H), 7.19 (s,
H), 7.02 (d, J = 8.1 Hz, 1H), 6.71 (d, J = 8.1 Hz, 1H), 2.25 (s, 3H).
Spectral data of 5. H NMR (400 MHz, CD Cl , 298 K): δ 14.20
2
2
(br, NH, 1H), 8.90 (d, J = 5.9 Hz, 1H), 7.91 (d, J = 4.8 Hz, 2H), 7.82
(s, 1H), 7.78 (t, J = 7.8 Hz, 1H), 7.51 (d, J = 7.9 Hz, 2H), 7.31 (d, J =
7.7 Hz, 1H), 7.23−7.21 (m, 1H), 6.99 (s, 1H), 6.90−6.82 (m, 3H),
1
19
F NMR (376 MHz, DMSO-d , 298 K): δ −58.42 (s, 3F). FD MS:
6
+
19
m/z 1205.1 (M − H Cl ). Anal. Calcd for C H Cl F Ir N : C,
4
6.66 (t, J = 7.4 Hz, 1H), 2.66 (s, 3H), 2.13 (s, 3H). F NMR (376
2
3
44 32
4
6
2
8
0.25; H, 2.46; N, 8.53. Found: C, 39.87; H, 2.81; N, 8.73.
MHz, CD
2
Cl
2
, 298 K): δ −60.67 (s, 3F). FD MS: m/z 702.1 (M +
4
+
Preparation of [Ir(κ -N3C)Cl] (2). A mixture of 1 (290 mg, 0.22
H ). Anal. Calcd for C H ClF IrN : C, 44.48; H, 3.01; N, 11.97.
2
26 21
3
6
mmol) in 20 mL of diethylene glycol monomethyl ether (DGME)
was refluxed for 12 h. After it cooled to RT, the solvent was removed
and the residue was taken into CH Cl , washed with water, dried over
Found: C, 44.72; H, 3.32; N, 11.84.
Selected X-ray structural data of 5: C H Cl F IrN ; M = 787.06;
2
7
23
3
3
6
monoclinic; space group = C2/c, a = 29.4830(15) Å, b = 13.6321(7)
2
2
3
Na SO , filtered, and concentrated to dryness. It was purified by silica
Å, c = 14.3728(6) Å; β = 106.6523(16)°; V = 5534.4(5) Å ; Z = 8;
2
4
−
3
gel column chromatography (CH Cl and methanol = 10:1) to afford
ρcalcd = 1.889 Mg·m ; F(000) = 3056; crystal size = 0.256 × 0.064 ×
3
2
2
−1
light-yellow solid 2 (210 mg, 76%).
0.033 mm ; T = 230 (2) K; μ = 5.165 mm ; 20902 reflections
collected, 6356 independent reflections (Rint = 0.0322), max and min
transmission = 0.7456 and 0.5699; restraints/parameters = 42/387,
1
Spectral data of 2. H NMR (400 MHz, CD Cl , 298 K): δ 9.46 (d,
2
2
J = 4.5 Hz, 1H), 8.22−8.15 (m, 2H), 8.03 (t, J = 6.4 Hz, 1H), 7.90−
G
DOI: 10.1021/acs.inorgchem.9b02799
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
GOF = 1.07, final R [I > 2σ(I)] = 0.0312 and wR (all data) = 0.0885;
the SMART program. Cell refinement and data reduction were made
1
2
−3
largest diff peak and hole = 1.351 and −1.005 e·Å .
with the SAINT program. The structure was determined using the
4
53
Preparation of [Ir(κ -N3C)Cl(dmpzH)] (6). A mixture of 2 (500
SHELXTL/PC program and refined using full-matrix least-squares.
mg, 0.40 mmol) and 3,5-dimethylpyrazole (dmpzH, 310 mg, 3.2
mmol) in 40 mL of DGME was refluxed for 14 h. After it cooled to
RT, the solvent was removed and the residue was taken into CH Cl ,
All non-hydrogen atoms were refined anisotropically, whereas all
hydrogen atoms of hydrocarbyl fragments were placed at the
calculated positions with fixed positional parameters, and hydride
was independently located on the electron density map and included
in the final stage of refinements. CCDC 1953441 (3), 1953442 (5)
and 1953443 (7) contain the crystallographic data for this paper.
2
2
washed with water, dried over Na SO , filtered, and concentrated to
2
4
dryness. It was next purified by silica gel column chromatography
4
(
CH Cl2 and ethyl acetate = 3:1) to afford light-yellow [Ir(κ -
2
N3C)Cl(dmpzH)] (6, 270 mg, 46%).
1
Spectral data of 6. H NMR (400 MHz, CD Cl , 298 K): δ 13.00
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.inorgchem.9b02799.
2
2
■
(
=
1
1
0
br, NH, 1H), 8.94 (d, J = 5.4 Hz, 1H), 7.89−7.86 (m, 2H), 7.77 (t, J
7.8 Hz, 1H), 7.48 (dd, J = 8.0, 2.8 Hz, 2H), 7.33 (d, J = 8.0 Hz,
*
S
H), 7.16−7.12 (m, 1H), 7.01−6.99 (m, 2H), 6.90 (t, J = 7.5 Hz,
H), 6.67 (t, J = 7.2 Hz, 1H), 5.96 (s, 1H), 2.67 (s, 3H), 2.56 (s, 3H),
.87 (s, 3H). 19F NMR (376 MHz, CD Cl , 298 K): δ −60.85 (s, 3F).
2
2
General experimental procedures of all measurements
and calculations, synthetic protocol of chelates, figures of
normalized IR ν(CO) spectra, TGA data curves, cyclic
+
FD MS: m/z 716.1 (M + H ). Anal. Calcd for C H ClF IrN : C,
2
7
23
3
6
4
5.28; H, 3.24; N, 11.73. Found: C, 45.45; H, 3.18; N, 11.61.
Preparation of [Ir (κ -N3C)(mpz) (CO)(H) ] (7). A mixture of 2 (50
mg, 0.04 mmol), 4-methylpyrazole (39 mg, 0.32 mmol) and K CO
30 mg, 0.20 mmol) in 10 mL of DGME was refluxed for 12 h. After
5
2
2
2
1
voltammograms, and H NMR spectra, and tables of
2
3
calculated energy levels and orbital transition analyses
(
(PDF)
it cooled to RT, the solvent was removed and the residue was taken
into excess of CH Cl , washed with water, dried over Na SO , filtered,
2
2
2
4
Accession Codes
and concentrated to dryness. It was next purified by silica gel column
5
CCDC 1953441−1953443 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
chromatography (CH Cl and hexane = 1:2) to afford yellow [Ir (κ -
2
2
2
N3C)(mpz) (CO)(H) ] (7, 16 mg, 41%).
2
2
1
Spectral data of 7. H NMR (500 MHz, acetone-d , 298 K): δ 8.29
6
(
d, J = 8.3 Hz, 1H), 8.17 (td, J = 7.8, 1.5 Hz, 1H), 7.99 (t, J = 7.9 Hz,
1
7
7
1
3
(
−
2
H), 7.93 (dd, J = 8.0, 0.9 Hz, 1H), 7.80−7.74 (m, 2H), 7.67 (s, 1H),
.39 (d, J = 7.3 Hz, 1H), 7.27 (td, J = 7.3, 1.1 Hz, 1H), 7.24 (s, 1H),
.20 (s, 1H), 6.93 (dd, J = 7.6, 1.2 Hz, 1H), 6.84 (td, J = 8.3, 1.4 Hz,
H), 6.62 (td, J = 7.3, 0.9 Hz, 1H), 5.94 (s, 1H), 5.91 (s, 1H), 2.84 (s,
H), 1.91 (s, 3H), 1.65 (s, 3H), −16.69 to −16.71(m, 1H), −19.73
AUTHOR INFORMATION
Corresponding Authors
*E-mail: apcslee@cityu.edu.hk.
*E-mail: yunchi@cityu.edu.hk.
■
1
9
d, J = 8.6 Hz, 1H). F NMR (470 MHz, acetone-d , 298 K): δ
6
+
58.20 (s, 3F). FD MS: m/z 968.1 (M + H ). IR(νCO, KBr pellet):
011 cm . Anal. Calcd for C H F Ir N O: C, 38.42; H, 2.81; N,
−
1
31 27 3 2 8
1
1.56. Found: C, 38.71; H, 2.81; N, 11.33.
Selected X-ray structural data of 7: C62.5H ClF Ir N O ; M =
ORCID
55
6
4
16
2
Chun-Sing Lee: 0000-0001-6557-453X
Yun Chi: 0000-0002-8441-3974
Notes
1
1
980.47 monoclinic; space group = P2/c, a = 20.6917(8) Å, b =
4.4421(5) Å, c = 22.1350(8) Å; β = 110.8392(8)°; V = 6181.9(4)
3
−3
Å ; Z = 4; ρ
= 2.128 Mg·m ; F(000) = 3748; crystal size = 0.130
3
calcd
−1
×
0.118 × 0.066 mm ; T = 220 (2) K; μ = 8.704 mm ; 45392
The authors declare no competing financial interest.
reflections collected, 14199 independent reflections (Rint = 0.0365),
max and min transmission = 0.7456 and 0.6170; restraints/parameters
ACKNOWLEDGMENTS
=
22/860, GOF = 1.078, final R [I > 2σ(I)] = 0.0296 and wR (all
■
1
2
−
3
data) = 0.0633; largest diff peak and hole = 2.596 and −2.481 e·Å .
This work was supported by the funding from Ministry of
Science and Technology (MOST), featured areas research
program within the framework of the Higher Education Sprout
Project administrated by Ministry of Education (MOE) of
Taiwan, and the Research Grant Council and City University
of Hong Kong, Hong Kong SAR.
5
Preparation of [Ir (κ -N3C)(dmpz) (CO)(H) ] (8). A mixture of 2
2
2
2
(
50 mg, 0.04 mmol), 3,5-dimethylpyrazole (30 mg, 0.32 mmol), and
K CO (30 mg, 0.20 mmol) in 10 mL of DGME was refluxed for 12
2
3
h. After it cooled to RT, the solvent was removed and the residue was
taken into CH Cl , washed with water, dried over Na SO , filtered,
2
2
2
4
and concentrated to dryness. It was next purified by silica gel column
5
chromatography (CH Cl and hexane = 1:2) to afford yellow [Ir (κ -
2
2
2
REFERENCES
N3C)(dmpz) (CO)(H) ] (8, 126 mg, 30%).
■
2
2
1
Spectral data of 8. H NMR (500 MHz, acetone-d , 298 K): δ 8.29
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Functionalized Multidentate Ligands: Tactical Designs and Opto-
electronic Applications. Chem. - Eur. J. 2016, 22, 17892−17908.
(5) Henwood, A. F.; Zysman-Colman, E. Lessons learned in tuning
the optoelectronic properties of phosphorescent iridium(iii) com-
plexes. Chem. Commun. 2017, 53, 807−826.
6
(
1
8
d, J = 8.3 Hz, 1H), 8.16 (td, J = 7.6, 1.5 Hz, 1H), 8.02 (t, J = 7.9 Hz,
H), 7.93 (d, J = 7.8 Hz, 1H), 7.88 (d, J = 4.6 Hz, 1H), 7.77 (d, J =
.0 Hz, 1H), 7.40 (d, J = 7.9 Hz, 1H), 7.27 (t, J = 6.1 Hz, 1H), 7.22
(
6
s, 1H), 7.09 (dd, J = 7.4, 1.1 Hz, 1H), 6.87 (td, J = 7.1, 1.2 Hz, 1H),
.63 (t, J = 7.3 Hz, 1H), 5.77 (s, 1H), 5.42 (s, 1H), 2.85 (s, 3H), 2.52
s, 3H), 2.13 (s, 3H), 0.43 (s, 3H), 0.17 (s, 3H), −16.65 to −16.67
(
(
1
9
m, 1H), −19.75 (d, J = 7.7 Hz, 1H). F NMR (470 MHz, acetone-
+
d , 298 K): δ −58.13 (s, 3F). FD MS: m/z 996.1 (M + H ). IR(νCO,
KBr pellet): 2007 cm . Anal. Calcd for C H F Ir N O: C, 39.75;
6
−
1
3
3
31
3
2
8
H, 3.13; N, 11.24. Found: C, 39.35; H, 3.31; N, 11.04.
X-ray Structural Determination. All crystals for X-ray
diffraction were obtained from the slow evaporation of an acetonitrile
solution at RT. Single crystal X-ray diffraction data were recorded on
a Bruker D8 VENTURE diffractometer equipped with a Oxford
Cryostream 800+ controller. The data collection was executed using
H
DOI: 10.1021/acs.inorgchem.9b02799
Inorg. Chem. XXXX, XXX, XXX−XXX

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