Exploring the self-assembly and energy transfer of dynamic supramolecular iridium-porphyrin systems

Article abstract of DOI:10.1039/c6dt02619b

We present the first examples of dynamic supramolecular systems composed of cyclometalated Ir(iii) complexes of the form of [Ir(C^N)₂(N^N)]PF₆ (where C^N is mesppy = 2-phenyl-4-mesitylpyridinato and dFmesppy = 2-(4,6-difluorophenyl)-

Full text of DOI:10.1039/c6dt02619b

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J. Hedley, D. B. Cordes, A. Slawin, D. Escudero, D. Jacquemin, T. Kosikova, D. Philp, D. Dawson, S. E.
Ashbrook, I. Samuel and E. Zysman-Colman, Dalton Trans., 2016, DOI: 10.1039/C6DT02619B.
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Exploring the SelfꢀAssembly and Energy Transfer of
Dynamic Supramolecular IridiumꢀPorphyrin Systems
Diego Rota Martir,a Gordon J. Hedley,b David B. Cordes,a Alexandra M. Z. Slawin,a Daniel
Escudero,c Denis Jacquemin,c,d Tamara Kosikova,a Douglas Philp,a Daniel M. Dawson,e
Sharon E. Ashbrook,e Ifor D.W. Samuel,b and Eli Zysman-Colmana*
a Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St
Andrews, St Andrews, Fife, KY16 9ST, UK, Fax: +44ꢀ1334 463808; Tel: +44ꢀ1334 463826;
Eꢀmail: eli.zysmanꢀcolman@stꢀandrews.ac.uk;
URL: http://www.zysmanꢀcolman.com
b Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St
Andrews, St Andrews, Fife, KY16 9SS, UK
c
CEISAM UMR CNRS 6230, Université de Nantes, 2 rue de la Houssinière, BP 92208,
44322 Nantes Cedex 3, France
d Institut Universitaire de France, 1, rue Descartes, 75231 Paris Cedex 5, France
e
EaStCHEM School of Chemistry and the Centre for Magnetic Resonance, University of St
Andrews, North Haugh, St Andrews, Fife, KY16 9ST, UK
Abstract. We present the first examples of dynamic supramolecular systems composed of
cyclometalated Ir(III) complexes of the form of [Ir(C^N)2(N^N)]PF6 (where C^N is mesppy =
2ꢀphenylꢀ4ꢀmesitylpyridinato and dFmesppy = 2ꢀ(4,6ꢀdifluorophenyl)ꢀ4ꢀmesitylpyridinato
and N^N is 4,4':2',2'':4'',4'''ꢀquaterpyridine, qpy) and zinc tetraphenylporphyrin (ZnTPP),
assembled through nonꢀcovalent interactions between the distal pyridine moieties of the qpy
ligand located on the iridium complex and the zinc of the ZnTPP. The assemblies have been
comprehensively characterized by a series of analytical techniques (1H NMR titration
1
experiments, 2D COSY and HETCOR NMR spectra and low temperature H NMR
spectroscopy) and the crystal structures have been elucidated by Xꢀray diffraction. The
optoelectronic properties of the assemblies and the electronic interaction between the iridium
and porphyrin chromophoric units have been explored with detailed photophysical
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measurements, supported by timeꢀdependent density functional theory (TDꢀDFT)
calculations.
Introduction.
The efficient energy transfer exhibited by natural photosynthetic organisms through
lightꢀharvesting antennae has drawn tremendous interest over the last decades, not only for
understanding the natural processes1 but also for technological applications in solar energy
conversion,1c, 1d, 2 which remains one of the great challenges of the century.2ꢀ3 In nature, lightꢀ
harvesting antennae are composed of different chromophoric units,1a, 4 which are generally
linked through nonꢀcovalent interactions5 such as hydrogen bonding, salt bridges, metalꢀ
ligand coordination or hydrophobic interactions, and are capable of absorbing sunlight and
efficiently channeling the energy to the reaction center.
Much effort has been devoted to the preparation of artificial donorꢀacceptor systems
based on combinations of multiꢀchromophoric arrays6 in order to emulate light harvesting in
plants. In particular, the covalent association between photophysicallyꢀactive Ru complexes
and zincꢀporphyrins has been wellꢀexplored in the context of understanding the efficiency of
the energy transfer involved.7 In these systems, formation of a chargeꢀseparated state
following ultraꢀfast photoinduced electron transfer (PeT) from the porphyrin donor to the
ruthenium acceptor are generally observed and as a result, the phosphorescence of the
ruthenium complexes is quenched and only weak porphyrinꢀcentered luminescence is
detected.5b, 6f
There are only a few examples of multiꢀmetallic dyads and triads composed of
metalloꢀporphyrins covalently linked to iridium(III) polypyridyl complexes. Unlike the
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examples discussed above, the nature of the electronic communication between the two
chromophores is far from straightforward. For instance, Soliman and coꢀworkers explored the
energy transfer processes in a multiꢀmetallic [ZnTAP]ꢀ[Pt]ꢀ[Ir] triad where [ZnTAP] is zinc
tetraarylporphyrin (ZnTAP), [Pt] is a Pt(II)ꢀdiacetylide bridge and [Ir] is [Ir(ppy)2(bpy)]PF6
(ppyH = 2ꢀphenylpyridine; bpy = 2,2'ꢀbipyridyl). Surprisingly, despite the presence of the
transꢀPt(II)ꢀdiacetylide bridge that was expected to mediate a direct electronic
communication between the two peripheral chromophores without itself contributing to the
overall photoꢀprocesseses,8 no electronic communication between the two units was observed
for this system. On the other hand, Sauvage, Flamigni and coꢀworkers showed that in a triad
consisting of zinc and gold tetraarylporphyrins covalently linked to a central
bis(terpyridyl)iridium(III) complex [Ir] (schematically, [ZnTAP]ꢀ[Ir]ꢀ[AuTAP], where
[AuTAP] is a gold tetraarylporphyrin), efficient and ultrafast electron transfer (kPeT > 5 × 1010
s–1) to the [AuTAP] occurred upon excitation of either [Ir] or [ZnTAP], leading to the
formation of a longꢀlived chargeꢀseparated state [ZnTAP]·+ꢀ[Ir]ꢀ[AuTAP]·–. No energy
transfer was detected for this system.6d
As these examples attest, although covalently linked metalloꢀporphyrin and
8ꢀ9
chromophoric organometallic complex dyads and triads have been explored,6d,
supramolecular systems involving metalloporphyrins and photophysicallyꢀactive complexes
nonꢀcovalently assembled remain largely unexplored.5b, 10 One relevant example, reported by
Kim and Shin, is that of an electron donor–acceptor dyad consisting of zinc
tetratolylporphyrin (ZnTTP) and a tris(bipyridyl)ruthenium(II) complex linked via axial
coordination of the distal pyridine moiety of the ruthenium complex to the zinc center.5b
Fluorescence of the porphyrin donor was significantly quenched as a result of facile electron
transfer to the ruthenium acceptor.
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Experiment Design
Herein we report the first examples of dynamic supramolecular assemblies composed
of cyclometalated Ir(III) complexes of the form of [Ir(C^N)2(qpy)]PF6 (where C^N is mesppy
= 2ꢀphenylꢀ4ꢀmesitylpyridinato in 1a and 1b and dFmesppy = 2ꢀ(4,6ꢀdifluorophenyl)ꢀ4ꢀ
mesitylpyridinato in 2a and 2b, and qpy is 4,4':2',2'':4'',4'''ꢀquaterpyridine) that act as the
donors, and zinc tetraphenylporphyrin (ZnTPP) that acts as the acceptor (Chart 1). In these
systems, the ZnTPP can coordinate to one or both of the two distal pyridine rings of the
[Ir(C^N)2(qpy)]PF6 complexes ([Ir(mesppy)2qpy]PF6, 1 and [Ir(dFmesppy)2qpy]PF6, 2,
(Chart 1) forming the assemblies shown in Chart 2a. Complexes 1 and 2 were designed with
the goal of modulating the donor energy as a function of the choice of C^N ligand and to
explore electronic communication between the two chromophoric units and ZnTPP in the
assemblies 1a, 1b, 2a and 2b (Chart 2a).
Chart 1. Chemical structures of the reference mononuclear cyclometalated Ir(III) complexes
1, 2 and 3 and ZnTPP under investigation in this work.
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The use of [Ir(mesppy)2(dtbubpy)]PF6, 3 (Chart 1) provides a useful negative control
in the form of the “nonꢀassembly” 3a (Chart 2b) to verify the presence/absence of electronic
communication between 1 or 2 and ZnTPP that is a direct result of axial coordination to Zn
(dtbubpy is 4,4'ꢀdiꢀtertꢀbutylꢀ2,2'ꢀbipyridine). By combining oneꢀ and twoꢀdimensional NMR
1
spectroscopy (1H NMR titrations, 2D COSY and HETCOR NMR, and lowꢀtemperature H
NMR spectra), detailed optoelectronic investigations (UVꢀVis and Near InfraRed (NIR)
absorption spectroscopy, steadyꢀstate and timeꢀresolved emission studies, including streak
camera measurements, and cyclic voltammetry experiments) and Xꢀray single crystal
structure analysis of the assemblies 1a, 1b, 2a and 2b (Chart 2a), the nature of the interaction
and electronic communication between Ir and Zn in these complexes is elucidated.
Chart 2. Chemical structures of a) the assemblies 1a [Ir(mesppy)2(qpy)]PF6 : ZnTPP 1:1 ratio
and 2a [Ir(dFmesppy)2(qpy)PF6 : ZnTPP 1:1 ratio; 1b [Ir(mesppy)2(qpy)]PF6 : ZnTPP 1:2
ratio and 2b [Ir(dFmesppy)2(qpy)]PF6 : ZnTPP 1:2 ratio, and b) Chemical structure of
complex 3 mixed with ZnTPP (3a) used as a control experiment.
Results and Discussion
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Synthesis.
The syntheses of the C^N and qpy ligands and the heteroleptic iridium complexes 1–3
are shown in Scheme 1. The mesppy and dFmesppy C^N ligands were each prepared in high
yield via SuzukiꢀMiyaura11 palladiumꢀcatalysed crossꢀcoupling reactions. The bulky mesityl
substituent was incorporated at the 4ꢀposition of the pyridine ring of ppy and dFppy C^N
ligands as mesityl substitution had been previously shown by Bryce and coꢀworkers12 for
[Ir(dFmesppy)2(pic)] (where pic is 2ꢀpiconilate) and ZysmanꢀColman and coꢀworkers13 for
[Ir(dFmesppy)2(dppe)]PF6 (where dppe is 1,2ꢀbis(diphenylphosphino)ethene)) to improve the
solubility of the complex in organic solvents and to reduce intermolecular interaction.14
Scheme 1. Synthesis of C^N and qpy ligands and [Ir(C^N)2(N^N)]PF6 complexes 1, 2 and 3.
a
Reagents and conditions: 2.0 equiv. K2CO3, 5 mol% Pd(PPh3)4, N2, 1,4ꢀdioxane/H2O (4:1
b
v/v), 105 °C, 56 h; 2.0 equiv. K2CO3, 5 mol% Pd(PPh3)4, N2, (MeOCH2)2/H2O (4:1 v/v),
c
d
130 °C, 19 h; 2ꢀEtOC2H4OH/H2O (4:1 v/v), 110 °C, N2, 19 h. DMF, 10 mol% Pd/C,
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e
f
165°C, 48h, i. CH2Cl2/MeOH (2:1 v/v), 55 °C, 19 h, N2; ii. Excess solid NH4PF6;
Zn(OAc)2, CHCl3/MeOH (5:1 v/v), 20 °C, 10 h.
.
The C^N ligands were complexed with IrCl3 3H2O and the resulting ꢀꢀdichloroꢀ
bridged iridium dimers [Ir(mesppy)2Cl]2, D1 and [Ir(dFmesppy)2Cl]2, D2 were formed in
good yield under standard conditions.15 The qpy ligand was prepared in low yield following
an oxidative Pdꢀcatalyzed coupling reaction of 4,4'ꢀbipyridine.16 Complexes 1 and 2 were
isolated through cleavage of D1 and D2 with qpy, whereas complex 3 was prepared through
cleavage of D1 with dtbubpy. All complexes were purified by column chromatography and
isolated as their hexafluorophosphate salt following an anion metathesis reaction using
NH4PF6. Zinc tetraphenylphorphyrin (ZnTPP) was prepared in high yield by complexation of
tetraphenylporphyrin with anhydrous zinc acetate.17 The purity of the complexes was
confirmed by 1H, 13C, and 19F NMR spectroscopy, HRMS and melting point analyses (see the
Electronic Supplementary Information, ESI). HRMS analysis showed in each case the
diagnostic molecular ion peak.
Assemblies 1a and 1b were rapidly obtained after mixing 1 with one or two
equivalents of ZnTPP, respectively, in CD2Cl2 at room temperature. The analogous
assemblies 2a and 2b were formed upon mixing 2 with one or two equivalents of ZnTPP
1
(Chart 2a). The formation of the assemblies was monitored by H NMR, 2D COSY, HMBC
and HMQC and 19F NMR experiments and HRMS spectrometry (NMR data are reported in
the ESI). Crystal structures of 1, 3, 1a and 1b were obtained through Xꢀray singleꢀcrystal
diffraction (vide infra), which confirmed the identity of the assemblies under study.
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Solutionꢀstate structural elucidation.
The assignment of all of the resonances in the H NMR spectrum of 1, 1a and 1b
1
1
1
1
(Figure S41) was carried out using 2D Hꢀ1H COSY, Hꢀ13C HMBC and Hꢀ13C HMQC
NMR experiments. After mixing 1 with one equivalent of ZnTPP in CD2Cl2 (1a, Figure 4h),
the proton resonances associated with 1 experienced an upfield shift (Figure 4c). As
expected, the proton resonances associated with the qpy moiety (Ha, Hb, Hc, Hd and He in
Figure 4h) were most sensitive to the axial coordination of the pyridine ring to ZnTPP. After
the addition of a second equivalent of ZnTPP, the qpy proton resonances experienced a
further upfield (Figure 4d). The formation of 1a and 1b takes place essentially
instantaneously after mixing 1 with ZnTPP and, after their formation, no further changes in
1
the H NMR spectra were observed. This observation has been described5b, 10b, 18 for many
axial interactions between Nꢀdonor ligands and ZnTPP.
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1
Figure 4. H NMR spectra (CD2Cl2, 500 MHz) of. a) 1 (298 K); b) ZnTPP (298 K); c) 1a
(298 K); d) 1b (298 K); e) 1a (236 K); f) 1b (236 K); g) 1 mixed with 4 equivalents of
ZnTPP (236 K). The spectral assignments correspond to the labeling scheme in h.
1
The H NMR spectrum for 1a (Figure 4c) is relatively simple, indicating a local C2
symmetry around the iridium center. This observation suggests that the exchange of bound
1
and unbound ZnTPP is fast compared to the NMR chemical shift timescale and that the H
NMR spectrum observed reflects a mixed speciation of ZnTPP – both free ZnTPP and ZnTPP
bound to 1. Titration of ZnTTP into a 3.09 mM solution of 1 in CD2Cl2 results in the
expected upfield shift of the resonance arising from Ha from δ 8.90 to δ 7.55 as the
concentration of ZnTPP is increased from 0 to 8.95 mM. This 1H NMR titration data could be
fitted to a sequential binding model (Figure 5) and affords an equilibrium constant of 8000 ±
370 M–1 for the formation of 1a from 1 and ZnTPP and 2000 ± 190 M–1 for the formation of
1b from 1a and ZnTPP. These data can then be used to construct speciation plots for
complexes 1a and 1b as a function of the initial concentration and the stoichiometry of the
mixture. For solutions containing 1:1 mixture of 1 and ZnTPP initially, 1a is the dominant
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complex at all concentrations between 100 µM and 100 mM. For solutions containing 1:2
mixture of 1 and ZnTPP initially, 1a is the dominant complex at concentrations below 600
µM and 1b is the dominant complex between this concentration and 100 mM.
1
Figure 5. (a) The chemical shift changes observed in the H NMR spectrum of a 3.09 mM
solution of 1 in CD2Cl2 upon addition of aliquots of ZnTPP (black points) are fitted (red line)
to a sequential binding model corresponding to the formation of 1a and 1b. Fractions of 1:1
complex 1a (blue lines) and 1:2 complex 1b (red lines) present in solution as a function of
concentration when (b) [ZnTPP]initial = [1]initial and (c) [ZnTPP]initial = 2 × [1]initial
.
The lower association constant for the binding of the second ZnTPP molecule to form
1b was expected, as the coordination of a second ZnTPP to 1a would be somewhat impeded
as a result of the steric bulk of the alreadyꢀbound ZnTPP. The association constants for the
formation of 1a and 1b are in the range reported for coordination between zinc porphyrins
and monotopic nitrogen ligands such as pyridine, with measured association constants
ranging between Ka = 102 and 105 M–1.5b, 10b The addition of more than 2 equivalents of
ZnTPP to 1 results in no further changes in the 1H NMR spectra (Figure S42).
1
The lowꢀtemperature (236 K) H NMR spectra of 1a (Figure 4e), 1b (Figure 4f) and
of 1 in the presence of 4 equivalents of ZnTPP (Figure 4g) are all similar. These results
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suggest that at 236 K similar speciation exists, regardless of relative stoichiometry of 1 and
ZnTPP, due to the slowing of the interchange processes between ZnTPP and the two distal
pyridine moieties of the qpy ligand.
1H NMR DOSY experiments of 1, 1a and 1b in CD2Cl2 at room temperature were
carried out in order to estimate the diffusion coefficients of the three entities in solution and
the results are reported in Figures S13, S29 and S36, respectively. Although 1a and 1b
possess higher molecular weights than 1, similar diffusion coefficients of ca. D = 1.35
×
10ꢀ9
m2·sꢀ1 have been obtained for the three entities. These results corroborate the dynamic and
weak NꢀZn coordination for 1a and 1b. As expected, when 3 was mixed with 2 equivalents of
ZnTPP no change was observed in the 1H NMR spectra (Figure S45), which clearly confirms
that the upfield shifting of the protons in 1a and 1b compared to 1 (cf. Figure 4) results from
NpyrꢀZn coordination.
Crystal Structures.
Crystal structures of 1, 1a and 1b (Figure 6) were obtained through singleꢀcrystal Xꢀ
ray diffraction studies. The crystal structures of 3 and ZnTPP coordinated to diethyl ether
were also obtained and are presented in the ESI (Figure S46), along with crystallographic
data for all complexes. Diffraction for complexes 1a and 1b was very weak, but despite this,
the structures of the two complexes could be unambiguously determined. In 1, 1a and 1b the
iridium center adopts a distorted octahedral geometry, with the two nitrogen atoms of the
C^N ligands are mutually trans while the two nitrogen atoms of the qpy ligand are disposed
trans with respect to the two IrꢀCC^N bonds, as observed for other [Ir(C^N)2(N^N)]PF6
complexes in the literature.19 Notably, the geometries (bond lengths and angles) of 1 do not
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differ markedly from those of 1a and 1b, indicating little perturbation of the local structure of
iridium upon coordination of 1 with ZnTPP. For all three structures the IrꢀNC^N bonds are ca.
2.03 Å, the IrꢀCC^N bonds ca. 2.00 Å, and the IrꢀNN^N bonds ca. 2.12 Å, which are close to the
values reported for other [Ir(C^N)2(N^N)]PF6 complexes.19ꢀ20 In each complex, an orthogonal
orientation of the mesityl ring with respect to the pyridine ring is observed (torsion angles ca.
90.5°). This feature was also observed in the crystal structures reported for other mesitylꢀ
containing iridium complexes.13 The four pyridine rings of the qpy moiety in each of 1, 1a
and 1b are not completely coplanar but instead adopt a torsion angle of approximately –40°
between each of the two distal pyridine rings and the central bipyridyl moiety.
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–
Figure 6. Views of the structures of (a) 1; (b) 1a; and (c) 1b, with PF6 anions, solvent
molecules, minor disorder components and hydrogen atoms omitted for clarity.
In all the structures, the bond angles between the iridium center and the qpy ligand
(NqpyꢀIrꢀNqpy) are essentially the same, ranging between 76.29(19) and 79.2(7)°. In 1a and 1b,
the Zn–Npyridyl bond distances are approximately 2.15 Å, which are in agreement with the
typical bond length values between Nꢀdonor ligands and ZnTPP.21 In 1a and 1b the qpy
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moieties show vector angles of, respectively, 74.16 and 64.68° (Figure S46) appropriate to
accommodate either one or two ZnTPP molecules around one iridium complex (Chart 2a)
resulting in Ir…Zn separations of 11.22–11.33 Å. Solidꢀstate NMR of bulk samples of 1 and
1a are consistent with the solidꢀstate structures (see the solidꢀstate NMR section in the ESI).
Photophysical properties.
Absorption.
The optoelectronic properties of all compounds were investigated in DCM solutions
at varying concentrations between 5 × 10–4 (above kd) and 1 × 10–6 (below kd) M at room
temperature and the results are summarized in Tables S2 and S3. In addition, DFT and TDꢀ
DFT calculations (see computational details in the ESI) were performed to gain insights into
the nature of the electronic transitions of the different complexes and assemblies. At a
concentration of 1 × 10–6 M, less than 1% of ZnTPP is actually bound to the qpy ligand in 1a,
1b, 2a and 2b whereas at a concentration of 5 × 10ꢀ4 M ca. 90% of the ZnTPP is bound to the
iridium complex. After mixing 1 and ZnTPP in a 1:1 ratio, a speciation of 1:1a:1b = 0.3:1.3:1
exists. After mixing 1 with two equivalents of ZnTPP, leads to a speciation of 1:1a:1b =
0.2:1:1.4.22
The UVꢀVisible (UVꢀVis) and Near InfraꢀRed (NIR) absorption spectra of ZnTPP,
1b, 2b, 3a and ZnTPP coordinated to pyridine (ZnTPPꢀpy, used as a reference assembly) are
shown in Figure 7a (the UVꢀVis absorption spectra of complexes 1–3 are shown in Figure
S49). The absorption spectra of all the iridium complexes are characterized by two intense
bands between 260 nm and 330 nm and a broad, lowerꢀintensity band at around 390 nm.
These bands are well reproduced by the TDꢀDFT calculations using the B3LYP exchangeꢀ
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correlation functional (see, for example, the UVꢀVis spectra of 1 and 2 in Figures S77a and
S80, respectively). A comparison with the TDꢀCAMꢀB3LYP results is provided in Figure
S77b for 1. This rangeꢀseparated functional generally yields blueꢀshifted bands compared to
experiment, therefore we have used the former functional for the rest of complexes.23 In line
with other cationic iridium complexes of the form [Ir(C^N)2(N^N)]+,56–59,86 the two higher
1
energy bands are theoretically assigned to spinꢀallowed πꢀπ* ligand centered (1LC)
transitions localized on the C^N ligands, while the broad bands at wavelengths >350 nm are
due to several metalꢀtoꢀligand charge transfer and ligandꢀtoꢀligand charge transfer transitions
(1MLCT/1LLCT).19, 24 This absorption band in 2 is blueꢀshifted (λmax ca. 360 nm) compared
to 1 due to presence of the electronꢀwithdrawing fluorine atoms on the C^N ligands, which
stabilize the highest occupied molecular orbital (HOMO) and consequently increase the band
gap.25 The energy levels of the frontier orbitals of 1 and 2 are given in Figure S78.
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Figure 7. a) UVꢀVis absorption spectra of ZnTPP, 1b, 2b and 3a recorded in DCM at 298 K
at a concentration of approximately 10–6 M. b) NIRꢀabsorption spectra from 450 to 950 nm of
ZnTPP, 1b, 2b, 3a and ZnTPPꢀpyridine recorded in DCM at 298 K at a concentration of 5 ×
10–4 M. c) expansion of the NIRꢀabsorption spectra from 650 to 950 nm of ZnTPP, 1b, 2b
and ZnTPPꢀpyridine after mathematical subtraction of the absorption of free ZnTPP.
The UVꢀVis absorption spectrum of ZnTPP (Figure 7a) is characterized by two major
1
bands. The intense absorption between 400 and 430 nm (Soret band) is due to a π
ꢀπ*
transition (S2) localized on the porphyrin moiety while the lowꢀintensity absorption band
between 500 and 600 nm shows vibronic structures and originates from the 1π
ꢀ
π* electronic
excitation (S1), the soꢀcalled Qꢀbands.8, 17 As shown in Figure S79, good agreement with the
computed TDꢀDFT results is obtained. The absorption spectra of 1b, 2b, and 3a collected at a
concentration of approximately 10–6 M (association < 1%) are very similar in profile to that
of ZnTPP and show the sum of the absorptivities of the iridium complexes and ZnTPP,
without any significant interactions between the two (Figure 7a).
NIR absorption spectroscopy of ZnTPP, 1b, 2b, 3a and ZnTPPꢀpy collected in DCM
at a concentration of 5 × 10–4 M are shown in Figure 7b. For metalloꢀporphyrins, the
presence of broad and weak absorption bands between 820 and 850 nm are generally ascribed
to the formation of molecular aggregates, which can occur at a concentration higher than 10–5
M.26 Indeed, in each of ZnTPP, ZnTPPꢀpy, 2a, 2b and 3a, there is a weak and broad
absorption band centered at approximately 800 nm. However, compared to ZnTPP, which
shows a single broad and unstructured absorption band in the NIR, there are two distinct
bands observed with enhanced absorptivity at 768 and 853 nm for 1b and 755 and 827 nm for
2b, respectively. This behavior matches the profile of ZnTPPꢀpy, which was formed in situ
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upon addition of an excess pyridine to ZnTPP (Figure 7b). By contrast, for 3a, where no
coordination between the chromophoric units takes place, the NIR absorption profile is very
similar to that of ZnTPP. Importantly, for metalloꢀporphyrins spinꢀforbidden singletꢀtriplet
transitions are possible and, as previously reported, the axial coordination between Nꢀdonor
ligands and ZnTPP can easily perturb the lowest triplet excited states of ZnTPP.27 From our
experiments, the enhanced absorptivity in the NIR observed for 1b and 2b seems to be
primarily due to perturbation the triplet state of ZnTPP, which is promoted by the axial
coordination between the distal pyridines of 1 and 2 with ZnTPP; though porphyrin
aggregation cannot be ruled out as contributing to this absorption band. In view of the TDꢀ
DFT results, the NIR absorption observed for 1b and 2b can tentatively be assigned to T1 and
T2 (both located at 750 nm). Note that, within the computational approach employed, the
triplet excitation energies have no intensity because spinꢀorbit coupling (SOC) was neglected.
Notably, the absorption spectra shown in Figure 7b are the weighted superposition of
the assemblies and free mononuclear complexes ZnTPP, 1 and 2. Figure 7c shows the
deconvoluted absorption spectra for 1b, 2b and ZnTPPꢀpy after mathematical subtraction of
the absorption spectrum of unbound ZnTPP. The remarkable enhancement of the NIR
absorption in 2a and 2b showcases the sensitivity of the triplet excitedꢀstate of ZnTPP to the
presence and nature of the axially bound ligand. As a result, upon coordination to the ZnTPP,
new CT singlet and triplet excitedꢀstates arise in the assemblies. A very low intensity
πporꢀπdtbbpy* CT transition (S1), which is predicted by TDꢀDFT to occur at 736 nm (using the
CAMꢀB3LYP functional for this obviously longꢀrange CT transition), might importantly
contribute (along with the ZnTPPꢀbased lowest triplet excited states) to the lowꢀenergy UVꢀ
Vis bands. These new bands significantly contribute to the observed enhancement of the NIR
features of the assemblies.
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Electrochemical properties.
The groundꢀstate electronic communication between the iridium and ZnTPP moieties
in 1a, 1b, 2a and 2b has been investigated by cyclic voltammetry, the data of which is
reported in Table S4 and the cyclic voltammograms (CVs) of 1, ZnTPP, 1a and 1b are shown
in Figure 8a (the CVs of 3 and 3a are reported in Figure 8b while the CVs of 2a and 2b and
are reported in the Figure S72). The CVs were recorded in deaerated DCM solution
containing n-NBu4PF6 as the supporting electrolyte and using Fc/Fc+ as an internal standard
at 298 K at a concentration of the iridium complexes of 1.46
×
10–3 M. At this concentration,
for 1a, 2a, 1b and 2b, ZnTPP is completely bound to iridium. After mixing 1 and ZnTPP in a
1:1 ratio, a speciation of 1:1a:1b = 0.1:5:1 exists; after mixing 1 with two equivalents of
ZnTPP, a speciation of 1:1a:1b = 0.1:1:6 is formed22 In agreement with the previously
reported electrochemistry,28 ZnTPP exhibits two monoꢀelectronic irreversible reduction
processes that are ascribed to the formation of the porphyrin radical anion [porph]·– and
dianion species [porph]2– at Epc = –1.29 V and –1.52 V, respectively. There are two monoꢀ
electronic reversible oxidation processes due to the formation of the porphyrin radical cation
[porph]·+ and dication species, [porph]2+ at Eox = 0.75 V and 1.05 V, respectively (ZnTPP
1/2
in Figure 8). Similar to the CVs of other cationic heteroleptic Ir(III) complexes,24a 1 exhibits
one quasiꢀreversible reduction wave at Ered1/2 = –1.21 V attributed to the first reduction of the
qpy ligand (note that the LUMO is located on this ligand, as shown in Figure S78) and one
irreversible oxidation at Epa = 1.35 V assigned to the IrIII/IrIV redox couple with significant
contribution from the C^N ligands (1 in Figure 8a, see also the HOMO in Figure S78).
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For the assemblies 1a and 1b, the oxidation potentials localized on the iridium
complex are only slightly cathodically shifted compared to 1 (Epa = 1.35 V for 1 vs. Epa
=
1.34 V for 1a and Epa = 1.33 V for 1b). However, remarkable changes are observed for the
redox processes localized on ZnTPP. Indeed, compared to ZnTPP, the Znꢀcentered oxidation
waves of both 1a and 1b exhibit a cathodic shift (Eox1/2 = 0.40 V for 1a, Eox1/2 = 0.36 V for 1b
vs. Eox = 0.75 V for ZnTPP) and their first reduction processes are likewise cathodically
1/2
shifted (Ered = –1.39 V for 1a, Ered = –1.40 V for 1b vs. Epc = –1.29 V for ZnTPP). This
1/2
1/2
behavior mirrors the electrochemistry of ZnTPP coordinated with Nꢀdonor electronꢀdonating
ligands,18b, 28ꢀ29 making the ZnTPP more easily oxidized and less easily reduced. The CV of
ZnTPP coordinated with pyridine (ZnTPPꢀpy) (Figure S74) corroborates the observed trends
in the CVs for 1a and 1b, where both the reduction and the oxidation waves of ZnTPPꢀpy are
shifted cathodically (Eox1/2 = 0.69 V, Eox1/2 = 0.36 V, Ered1/2 = –1.61 V) relative to ZnTPP.
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Figure 8. a) CVs for 1, ZnTPP, 1a and 1b and b) CVs for 3, ZnTPP and 3a recorded at 298 K
in deaerated DCM solution containing n-NBu4PF6 as the supporting electrolyte and using
Fc/Fc+ as an internal standard (Fc/Fc+ = 0.46 V in DCM with respect to SCE).30
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The electrochemistry of 2, 2a and 2b was also investigated (Figure S73) and the
trends match those presented above. CVs of 3 and 3a are shown in Figure 8b. In deaerated
DCM, 3 exhibits one irreversible reduction at Ered = –1.15 V attributed to the reduction of the
dtbubpy ligand and one reversible oxidation at Eox1/2 = 1.17 V, assigned to the IrIII/IrIV redox
couple with contribution from the C^N ligands (3 in Figure 8b).19 In line with NMR and
absorption data, the CV of 3a contains the superposition of the CVs of 3 and ZnTPP. These
control experiments show that, as expected, there is no groundꢀstate electronic
communication between 3 and ZnTPP.
Emission studies.
Upon photoexcitation into the CT band of the iridium complex (λexc = 360 nm) at a
concentration of 3
×
10ꢀ5 M, a broad and unstructured emission profile is observed for 1 (λem
3
= 638 nm, red line in Figure S50a), indicating an emission from a mixed MLCT/3LLCT
state. The character of the emissive state was confirmed by the DFT optimization of the
lowest triplet excited state (T1, (Figure 9)). Incorporation of electronꢀwithdrawing fluorine
atoms on the C^N ligand induced the expected blueꢀshift in the emission observed for
complexes 2 (λem: 565 nm) compared to the fluorineꢀfree congener 1 (red line in Figure
S50b). As reported in Table S3, a ΦPL of 14% (λexc = 360 nm) with τe of 300 ns has been
obtained for 1 whereas a higher ΦPL of 34% (λexc = 360 nm) with τe of 993 ns has been
obtained for 2. Upon excitation of ZnTPP into either the Soret or Q bands (λexc = 420 or 550
nm, respectively), a vibronic emission, characteristic of ZnTPP,17 is observed between 570
and 740 nm (light blue line in Figure S50).
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Figure 9. Spinꢀdensity distributions (B3LYP/6ꢀ31G(d) ꢀ ecpꢀ60ꢀmwb for Ir) at the
optimized geometry of the lowest triplet excited state of 1 and 1a and 1b. ꢁSCFꢀDFT
emission energies determined at the same level of theory are indicated below the structures.
Contour threshold: 0.009 a.u. (1) and 0.005 a.u. (1a and 1b).
In order to investigate the nature of the emission of 1a, 1b, 2a and 2b and the
presence of energy and/or electron transfer between the iridium moiety and ZnTPP, these
1
assemblies were excited into both the CT band (centered on the iridium complex, λexc= 360
nm), and the Soret and Q bands. Unfortunately, the emission of 1 and ZnTPP coincidentally
overlap and consequently the study of this system proved challenging (Figure S50a). In
contrast, due to the introduction of the fluorine atoms on the C^N ligands, the emissions of 2
and ZnTPP are better resolved (Figure S50b), which makes this system much more amenable
towards the study of electronic communication between the chromophores.31 However, at the
very low concentrations required for quantifiable steadyꢀstate emission experiments, the
association between ZnTPP and the iridium complex is almost nonꢀexistent, whereas at
concentrations higher than 10ꢀ4 M (above kd, association > 80%), only selfꢀabsorption of the
emission of complex 2 due to the presence of ZnTPP is observed by both emission titration
experiments and highꢀtimeꢀresolution streak camera measurements (see Figure S66 for
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emission titrations and Figure S75 and S76 for streak camera studies). The same selfꢀ
absorption was also observed for the “nonꢀassembly 3a” (Figure S67).
DFT modeling reveals that for 1a and 1b the lowest triplet excitedꢀstate is a 3CT state
involving the HOMO located on the ZnTPP moiety and the LUMO located on the qpy ligand.
They are theoretically located in the NIR region (e.g., at ca. 1250 nm for 1a). Therefore,
3
these CT states are likely not involved in the emission of the assemblies and may play an
important role in the nonꢀradiative deactivation pathways of the assemblies. Thus, the
emission observed for the assemblies is merely monomerꢀbased and the hypothesis of
emission arising from new transitions can be ruled out. The same findings also hold for both
2a and 2b.
The redox potentials combined with the optical data were used to estimate the free
energies associated with PeT processes in 1a and 2a following the RehmꢀWeller equation
(see the ESI for details).32 Due to the very similar optoelectronic data obtained for 1b and 2b,
the same results can be readily extended to the 1:2 assemblies. For both for 1a and 2a, upon
photoexcitation of the porphyrin unit, photoinduced electron transfer to the iridium center is
found to be exergonic in DCM (ꢁGCS = –0.68 eV). At present no evidence of emission
quenching due to formation of chargeꢀseparated state has been experimentally observed by
steadyꢀstate and timeꢀresolved spectroscopy. By contrast, due to the higher energy required to
extract an electron from the iridium complexes, ꢁGCS for PeT processes, in which 1 and 2 act
as donors and ZnTPP acts as the acceptor, are found to be +0.38 eV for 1a and +0.08 eV for
2a and thus not thermodynamically favorable (for further details see estimation of PeT in the
ESI).
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Conclusions.
We report the synthesis and optoelectronic study of supramolecular assemblies
composed of a cationic iridium complex of the form [Ir(C^N)2(qpy)]PF6 and ZnTPP, through
dynamic and nonꢀcovalent interactions between the distal pyridine moieties of the qpy
1
ligands of the iridium complex and zinc. H NMR titration experiments reveal equilibrium
constants of 8000 ± 370 M–1 for the formation of 1a from 1 and ZnTPP, and 2000 ± 190 M–1
for the formation of 1b from 1a and ZnTPP. The structures of the assemblies have been
elucidated by XꢀRay singleꢀcrystal structure analyses. For the assemblies 1a, 1b, 2a and 2b,
strong selfꢀabsorption of the iridium emissions due to the presence of ZnTPP was observed
with no evidence of Förster energy transfer between the units. Furthermore, despite favorable
thermodynamics for electron transfer from ZnTPP to iridium, no evidence of the formation of
a chargeꢀseparated state following electron transfer was observed by steadyꢀstate and timeꢀ
resolved emission spectroscopy.
Acknowledgements. EZꢀC acknowledges the University of St Andrews for financial
support. We thank Umicore AG for the gift of materials. IDWS acknowledges support from
EPSRC (EP/J009016) and the European Research Council (grant 321305). IDWS also
acknowledges support from a Royal Society Wolfson research merit award. We thank the
EPSRC UK National Mass Spectrometry Facility at Swansea University for analytical
services. DJ acknowledges the European Research Council (grant: 278845) and the RFI
Lumomat for financial support. This research used resources of (1) the GENCIꢀ
CINES/IDRIS, (2) Centre de Calcul Intensif des Pays de Loire (CCIPL), and (3) a local Troy
cluster.
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Supporting information. Experimental section, characterization of precursors, ligands,
iridium complexes and supramolecular assemblies; solution NMR investigations of the
assemblies; determination of the association constants and displacement assays using DMAP;
Xꢀray crystal structure parameters of 1, 1a and 1b, and crystal structures of complex 3 and
ZnTPPꢀether; solidꢀstate NMR characterization; absorption and emission studies at different
concentrations, emission studies, streak camera studies and electrochemical characterization;
computational details, including simulated absorption spectra, representation of the key
frontier molecular orbitals; theoretical estimation of photoinduced electron transfer processes;
as well as CIF files for 1, 1a and 1b, 3 and ZnTPPꢀether, CCDC: 1472895ꢀ1472899.
References
(1). (a) R. A. Haycock, A. Yartsev, U. Michelsen, V. Sundström and C. A. Hunter, Angew.
Chem. Int. Ed., 2000, 39, 3616ꢀ3619; (b) X. Chi, A. J. Guerin, R. A. Haycock, C. A. Hunter
and L. D. Sarson, J. Chem. Soc., Chem. Commun., 1995, 2567ꢀ2569; (c) Y. Kuramochi, A.
Satake, M. Itou, K. Ogawa, Y. Araki, O. Ito and Y. Kobuke, Chemistry, 2008, 14, 2827ꢀ2841;
(d) Y. Kuramochi, A. S. Sandanayaka, A. Satake, Y. Araki, K. Ogawa, O. Ito and Y. Kobuke,
Chemistry, 2009, 15, 2317ꢀ2327; (e) J.ꢀM. Lehn, Science, 2002, 295, 2400ꢀ2403.
(2). N. Armaroli and V. Balzani, Angew Chem Int Ed Engl, 2007, 46, 52ꢀ66.
(3).
N. Armaroli and V. Balzani, Chem. Eur. J., 2015, ASAP, DOI:
10.1002/chem.201503580.
(4). (a) A. W. Roszak, T. D. Howard, J. Southall, A. T. Gardiner, C. J. Law, N. W. Isaacs and
R. J. Cogdell, Science, 2003, 302, 1969ꢀ1972; (b) G. McDermott, S. M. Prince, A. A. Freer,
A. M. HawthornthwaiteꢀLawless, M. Z. Papiz, R. J. Cogdell and N. W. Isaacs, Nature, 1995,
374, 517ꢀ521; (c) S. Bahatyrova, R. N. Frese, C. A. Siebert, J. D. Olsen, K. O. van der Werf,
R. van Grondelle, R. A. Niederman, P. A. Bullough, C. Otto and C. N. Hunter, Nature, 2004,
430, 1058ꢀ1062.
(5). (a) M. D. Ward, Chem. Soc. Rev., 1997, 26, 365ꢀ375; (b) D. Kim and E.ꢀJ. Shin, Bull.
Korean Chem. Soc., 2003, 24, 1490ꢀ1494; (c) J. L. Sessler, C. T. Brown, D. O'Connor, S. L.
Springs, R. Wang, M. Sathiosatham and T. Hirose, J. Org. Chem., 1998, 63, 7370ꢀ7374.
(6). (a) A. Prodi, M. T. Indelli, C. J. Kleverlaan, E. Alessio and F. Scandola, Coord. Chem.
Rev., 2002, 229, 51ꢀ58; (b) F. D’Souza, E. Maligaspe, K. Ohkubo, M. E. Zandler, N. K.
Subbaiyan and S. Fukuzumi, J. Am. Chem. Soc., 2009, 131, 8787ꢀ8797; (c) L. Yu, K.
Muthukumaran, I. V. Sazanovich, C. Kirmaier, E. Hindin, J. R. Diers, P. D. Boyle, D. F.
Bocian, D. Holten and J. S. Lindsey, Inorg. Chem., 2003, 42, 6629ꢀ6647; (d) L. Flamigni, G.
Marconi, I. M. Dixon, J.ꢀP. Collin and J.ꢀP. Sauvage, J. Phys. Chem. B, 2002, 106, 6663ꢀ
6671; (e) F. Ito, Y. Ishibashi, S. R. Khan, H. Miyasaka, K. Kameyama, M. Morisue, A.
25

Dalton Transactions
Page 26 of 27
View Article Online
DOI: 10.1039/C6DT02619B
Satake, K. Ogawa and Y. Kobuke, J. Phys. Chem. A, 2006, 110, 12734ꢀ12742; (f) D.
LeGourriérec, M. Andersson, J. Davidsson, E. Mukhtar, L. Sun and L. Hammarström, J.
Phys. Chem. A, 1999, 103, 557ꢀ559; (g) Y. Ishida, T. Shimada and S. Takagi, J. Phys. Chem.
C, 2013, 117, 9154ꢀ9163; (h) E. Iengo, E. Zangrando, M. Bellini, E. Alessio, A. Prodi, C.
Chiorboli and F. Scandola, Inorg. Chem., 2005, 44, 9752ꢀ9762; (i) B. Ventura, A. Barbieri,
A. Degli Esposti, J. B. Seneclauze and R. Ziessel, Inorg. Chem., 2012, 51, 2832ꢀ2840; (j) J.
Osío Barcina, N. HerreroꢀGarcía, F. Cucinotta, L. De Cola, P. ContrerasꢀCarballada, R. M.
Williams and A. GuerreroꢀMartínez, Chem. Eur. J., 2010, 16, 6033ꢀ6040.
(7). (a) F. Scandola, C. Chiorboli, A. Prodi, E. Iengo and E. Alessio, Coord. Chem. Rev.,
2006, 250, 1471ꢀ1496; (b) J. Otsuki, T. Akasaka and K. Araki, Coord. Chem. Rev., 2008,
252, 32ꢀ56; (c) A. F. Nogueira, L. F. O. Furtado, A. L. B. Formiga, M. Nakamura, K. Araki
and H. E. Toma, Inorg. Chem., 2004, 43, 396ꢀ398; (d) D. E. Williams, J. A. Rietman, J. M.
Maier, R. Tan, A. B. Greytak, M. D. Smith, J. A. Krause and N. B. Shustova, J. Am. Chem.
Soc., 2014, 136, 11886ꢀ11889; (e) A. Gabrielsson, F. Hartl, H. Zhang, J. R. Lindsay Smith,
M. Towrie, A. Vlček and R. N. Perutz, J. Am. Chem. Soc., 2006, 128, 4253ꢀ4266.
(8). A. Harriman, M. Hissler, O. Trompette and R. Ziessel, J. Am. Chem. Soc., 1999, 121,
2516ꢀ2525.
(9). (a) J. Henderson and C. P. Kubiak, Inorg Chem, 2014, 53, 11298ꢀ11306; (b) M. Murai,
M. Sugimoto and M. Akita, Dalton Trans, 2013, 42, 16108ꢀ16120; (c) P. Sweigert, Z. Xu, Y.
Hong and S. Swavey, Dalton Trans, 2012, 41, 5201ꢀ5208; (d) A. M. Soliman, M.
Abdelhameed, E. ZysmanꢀColman and P. D. Harvey, Chem. Commun., 2013, 49, 5544ꢀ5546.
(10). (a) M. D. Ward and P. R. Raithby, Chem. Soc. Rev., 2013, 42, 1619ꢀ1636; (b) A. Satake
and Y. Kobuke, Tetrahedron, 2005, 61, 13ꢀ41; (c) L. Flamigni, J.ꢀP. Collin and J.ꢀP.
Sauvage, Acc. Chem. Res., 2008, 41, 857ꢀ871; (d) I. M. Dixon, J.ꢀP. Collin, J.ꢀP. Sauvage, L.
Flamigni, S. Encinas and F. Barigelletti, Chem. Soc. Rev., 2000, 29, 385ꢀ391.
(11). (a) N. Miyaura and A. Suzuki, Chem. Rev., 1995, 95, 2457ꢀ2483; (b) N. Miyaura, T.
Yanagi and A. Suzuki, Synth. Commun., 1981, 11, 513ꢀ519.
(12). V. N. Kozhevnikov, Y. Zheng, M. Clough, H. A. AlꢀAttar, G. C. Griffiths, K.
Abdullah, S. Raisys, V. Jankus, M. R. Bryce and A. P. Monkman, Chem. Mater., 2013, 25,
2352ꢀ2358.
(13). D. Rota Martir, A. K. Bansal, V. Di Mascio, D. B. Cordes, A. F. Henwood, A. M. Z.
Slawin, P. C. J. Kamer, L. MartinezꢀSarti, A. Pertegas, H. J. Bolink, I. D. W. Samuel and E.
ZysmanꢀColman, Inorganic Chemistry Frontiers, 2016, 3, 218ꢀ235.
(14). C. Zhong, C. Duan, F. Huang, H. Wu and Y. Cao, Chem. Mater., 2011, 23, 326ꢀ340.
(15). M. Nonoyama, Bull. Chem. Soc. Jpn., 1974, 47, 767ꢀ768.
(16). S. Bossmann, A. Shi and M. Pokhrel, Synthesis, 2007, 2007, 505ꢀ514.
(17). J. C. Manton, C. Long, J. G. Vos and M. T. Pryce, Dalton Trans, 2014, 43, 3576ꢀ3583.
(18). (a) H. Sun, C. Navarro and C. A. Hunter, Org. Biomol. Chem., 2015, 13, 4981ꢀ4992; (b)
F. D'Souza, S. Gadde, M. E. Zandler, M. Itou, Y. Araki and O. Ito, Chem. Commun., 2004,
2276ꢀ2277.
(19). S. Ladouceur, D. Fortin and E. ZysmanꢀColman, Inorg. Chem., 2010, 49, 5625ꢀ5641.
(20). (a) N. M. Shavaleev, G. Xie, S. Varghese, D. B. Cordes, A. M. Z. Slawin, C.
Momblona, E. Ortí, H. J. Bolink, I. D. W. Samuel and E. ZysmanꢀColman, Inorg. Chem.,
2015, 54, 5907ꢀ5914; (b) R. D. Costa, E. Ortì, H. J. Bolink, S. Graber, S. Schaffner, M.
Neuburger, C. E. Housecroft and E. C. Constable, Adv. Funct. Mater., 2009, 19, 3456ꢀ3463;
(c) A. B. Tamayo, S. Garon, T. Sajoto, P. I. Djurovich, I. M. Tsyba, R. Bau and M. E.
Thompson, Inorg. Chem., 2005, 44, 8723ꢀ8732.
(21). (a) P. S. Sobolev, V. P. Andreev and T. A. Ekimova, Russ. J. Gen. Chem., 2014, 84,
1399ꢀ1403; (b) A. L. Litvinov, D. V. Konarev, A. Y. Kovalevsky, I. S. Neretin, P. Coppens
and R. N. Lyubovskaya, Crystal Growth & Design, 2005, 5, 1807ꢀ1819.
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(22). After mixing 1 with 1 equivalent of ZnTPP, the following concentrations are obtained:
[1] = 0.00007 M; [1a] = 0.002 M; [1b] = 0.0004 M. After mixing 1 with 2 equivalent of
ZnTPP, the following concentrations are obtained: [1] = 0.00006 M; [1a] = 0.0006 M; [1b] =
0.0009 M.
(23). (a) D. Escudero and W. Thiel, J. Chem. Phys., 2014, 140, 194105; (b) D. Escudero and
D. Jacquemin, Dalton Trans., 2015, 44, 8346ꢀ8355.
(24). (a) S. Ladouceur and E. ZysmanꢀColman, Eur. J. Inorg. Chem., 2013, 2013, 2985ꢀ3007;
(b) S. Lamansky, P. Djurovich, D. Murphy, F. AbdelꢀRazzaq, R. Kwong, I. Tsyba, M. Bortz,
B. Mui, R. Bau and M. E. Thompson, Inorg. Chem., 2001, 40, 1704ꢀ1711; (c) S. Lamansky,
P. Djurovich, D. Murphy, F. AbdelꢀRazzaq, H.ꢀE. Lee, C. Adachi, P. E. Burrows, S. R.
Forrest and M. E. Thompson, J. Am. Chem. Soc., 2001, 123, 4304ꢀ4312.
(25). S. Ladouceur, D. Fortin and E. ZysmanꢀColman, Inorg. Chem., 2011, 50, 11514ꢀ11526.
(26). (a) P. C. Ray and Z. Sainudeen, J. Phys. Chem. A, 2006, 110, 12342ꢀ12347; (b) E.
Collini, C. Ferrante and R. Bozio, J. Phys. Chem. C, 2007, 111, 18636ꢀ18645.
(27). V. A. Walters, J. C. de Paula, B. Jackson, C. Nutaitis, K. Hall, J. Lind, K. Cardozo, K.
Chandran, D. Raible and C. M. Phillips, J. Phys. Chem., 1995, 99, 1166ꢀ1171.
(28). C.ꢀW. Huang, K. Yuan Chiu and S.ꢀH. Cheng, Dalton Trans., 2005, 2417ꢀ2422.
(29). F. D'Souza, Y.ꢀY. Hsieh and G. R. Deviprasad, Inorg. Chem., 1996, 35, 5747ꢀ5749.
(30). N. G. Connelly and W. E. Geiger, Chem. Rev., 1996, 96, 877ꢀ910.
(31). J. Wu, F. Liu, J. Ma, R. J. Silbey and J. Cao, J Chem Phys, 2012, 137, 174111.
(32). (a) G. J. Kavarnos and N. J. Turro, Chem. Rev., 1986, 86, 401ꢀ449; (b) S. Doose, H.
Neuweiler and M. Sauer, Chemphyschem, 2009, 10, 1389ꢀ1398.
TOC Graphic
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