Copper(I) complexes with remotely functionalized phosphine ligands: Synthesis, structural variety, photophysics and effect onto the optical properties

Article abstract of DOI:10.1016/j.ica.2020.119971

The synthesis, chemical and photophysical investigation of a series of eight novel copper-halide derivatives with different nuclearity is herein presented. One mononuclear copper(I) complex with formula [CuI(pyridine)(P)₂], where P is a functio

Full text of DOI:10.1016/j.ica.2020.119971

InorganicaChimicaActa514(2021)119971
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Inorganica Chimica Acta
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Research paper
Copper(I) complexes with remotely functionalized phosphine ligands:
Synthesis, structural variety, photophysics and effect onto the optical
properties
Julien Eglya, Damien Bissessara, Thierry Acharda, Benoît Heinricha, Pascal Steffanutb,
⁎
⁎
Matteo Mauroa, , Stéphane Bellemin-Laponnaza,
a Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg-CNRS UMR 7504, 23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France
b CLARIANT Plastics and Coatings AG, Rothausstrasse 61, 4132 Muttenz, Switzerland
A R T I C L E I N F O
A B S T R A C T
Keywords:
The synthesis, chemical and photophysical investigation of a series of eight novel copper-halide derivatives with
different nuclearity is herein presented. One mononuclear copper(I) complex with formula [CuI(pyridine)(P)2],
where P is a functionalized phosphine, six dinuclear derivatives bearing the rhombic {Cu2I2} subunits and with
general formula [Cu(μ-I)(P)(N)]2 (N = pyridine, quinoline and 4-cyanopyridine) as well as one tetranuclear
copper-iodide clusters of general formula [Cu(μ-I)P]4 consisting of a cubane-like {Cu4X4} motif were straight-
forwardly prepared, also by means of mechano-chemical synthetic procedure. The phosphine ligands were
prepared in excellent yield by using simple hydrophosphination reactions. For five of the investigated cuprous
iodide derivatives their atom connectivity and solid-state crystalline packing was unambiguously confirmed by
solving their single-crystal X-ray structure. All the investigated complexes resulted into photo- and thermally-
stable luminescent species. In the solid state as microcrystalline powder samples, the complexes display intense
photoluminescence ranging from the sky-blue to orange-red portion of the spectrum with PLQY values of
0.28–0.50 and 0.34–0.97 at room and low (77 K) temperature, respectively, depending on the nature of both the
coordinated N-heteroaromatic ring and phosphine ligands. In spite of the remote location of the functionali-
zation of the phosphine, profound effects are observed onto the solid-state emission properties highlighting the
importance of microenvironment for the emitters in the aggregated phase.
Copper complexes
Cuprophilic interactions
Photophysics
Phosphine ligands
Phosphorescence
1. Introduction
consequence, it results that luminescent copper complexes typically
possess slower radiative rate constants and longer-lived excited states
Photoactive, earth-abundant, metal complexes are currently the
subject of intensive research in inorganic photochemistry that is mainly
driven by their appealing applications in the field of photocatalysis,
solar energy conversion and light emitting devices [1–5]. In particular,
Cu(I)-based emitters are considered as an attractive alternative to those
containing platinum group metals for the development of (electro-)lu-
minescent materials [6–10]. Compared to these latter, copper is indeed
less toxic and cheaper. Also, its luminescent complexes lack of low-lying
metal centered (MC) states that might detrimentally affect the emission
efficiency owing to the d10 electronic configuration of the Cu(I) ion. On
the other hand, copper atom exerts a much smaller spin orbit coupling
than those containing heavier metals. This makes the former less sui-
table for application in efficient solid-state light emitting devices at the
current stage, since detrimental processes such as triplet–triplet anni-
hilation (TTA) and exciton-polaron quenching may occur to a large
extent. Nonetheless, increasing efforts are devoted to enhance the
emission properties of copper-based emitters nowadays [11].
As function of the ligands surrounding the metal, temperature and
aggregation state, Cu complex can exhibit emissions that are derived
from different excited states, i.e. metal-to-ligand charge transfer
(MLCT), halide-to-ligand charge transfer (XLCT) and also cluster-cen-
tered (CC) for polynuclear copper complexes [8,9,12]. Remarkably,
some Cu(I) complexes have successfully displayed Thermally-Activated
Delayed Fluorescence (TADF) and showed efficient singlet harvesting in
Organic Light Emitting Diodes (OLEDs) [11,13–16].
(SOC) effect compared to iridium and platinum (ζCu = 857 cm−1
;
ζIr = 3909 cm−1; ζPt = 4481 cm−1), which significantly reduces the
first-order perturbation associated with singlet–triplet mixing. As a
⁎ Corresponding authors.
E-mail addresses: mauro@unistra.fr (M. Mauro), bellemin@unistra.fr (S. Bellemin-Laponnaz).
https://doi.org/10.1016/j.ica.2020.119971
Received 5 June 2020; Received in revised form 14 August 2020; Accepted 23 August 2020
Availableonline27August2020
0020-1693/©2020ElsevierB.V.Allrightsreserved.

J. Egly, et al.
InorganicaChimicaActa514(2021)119971
As a matter of fact, copper(I) shows propensity towards coordina-
Table 1
Catalyst-free hydrophosphination of alkenes in the presence of 4 equiv. of 2-
tion with halogens and heteroaromatic ligands, including nitrogen,
phosphorous and chalcogen-containing species, yielding a remarkable
structural variety that is highly dependent on the employed synthetic
procedure. Moreover, this class of emitters is characterized by rich
polymorphism and colorful photophysics in the solid state, which is also
strongly influenced by processing solvents and condition [17,18].
However, the high structural flexibility renders the selective prepara-
tion of copper-halide species often cumbersome.
MeTHF: synthesis of phosphine ligands P1-P4.
Pioneering investigations on the luminescence of mononuclear
copper complexes of general formula [Cu(N^N)2]+, where N^N is a
chelating diimine ligand such as substituted phenanthrolines, were re-
ported by the group of McMillin [19], which unrevealed emission from
an higher-lying 1MCLT state in thermal equilibrium with 3MLCT
manifold, [20,21] as well as the excited state quenching process
through D2 flattening and exciplex formation [22,23]. Recently, Kato
and collaborators showed that simple TADF-active copper(I) halide
complexes stabilized by triphenylphosphine ligand and various N-aro-
matic ligands can be efficiently prepared from inexpensive reagents via
mechanochemical syntheses in
[24–27].
a rather straightforward manner
Multinuclear cuprous compounds bearing heteroaromatic ligands
have been largely investigated as well, which display either discrete or
polymeric structure (formally) formed by the assembling of rhombic
{Cu2X2} subunits (X = halogen) into linear or ladder-type structure
that often display intense emission in the solid state. Though a few
scattered reports describing the photophysics of dinuclear {Cu2X2L4}
species, where L is a N- and/or P- ligand, were reported previously
[28–31], the first extensive investigation was carried out by Sasaki,
Tsuge and co-workers on compounds of the family [Cu(μ-X)(PPh3)L]2
and [Cu(μ-X)L2]2 with different ligand combinations (L = is pyridine/
substituted pyridine or a saturated amine) [12,32,33] that highlighted
the effect of the halogen and π-accepting ability of the N-containing
ligand on the nature of the emitting excited state. Following works by
Kato and co-workers investigated the photoluminescence properties of
the [Cu(μ-X)L2]2 scaffold bearing P- and S- ligands, [34–36] as well as
of coordination polymers containing the dinuclear {Cu2X2} scaffold
[37,38]. In addition, Bräse described a novel family of highly lumi-
nescent either homo- or heteroleptic complexes consisting of a but-
terfly-shaped {Cu2X2} skeleton and bearing various heteroaromatic P^N
bridging ligands [15,39,40].
different nuclearity in the solid state at both room and cryogenic tem-
perature.
2. Results and discussion
2.1. Synthesis of the phosphine ligands P1-P4
Phosphines P1–P4 were synthesized in one-step procedure starting
from diphenylphosphine, namely Ph2PH, and the corresponding alkene
derivative (i.e. methyl vinyl ketone, ethyl acrylate, tert-butyl acrylate,
itaconic acid methyl ester), according to our previously reported pro-
cedure [51]: they were prepared by addition of the corresponding al-
kene compounds on Ph2PH (1.2 equiv.) in presence of 2-MeTHF (4
equiv.) under argon atmosphere in a closed vessel. The hydropho-
sphination product was then easily isolated by flash chromatography on
silica with yield ranging from 81% to 95% (Table 1). The hydropho-
sphination of itaconic methyl ester generated a product that contains a
chiral center, which was next used in its racemic form.
Furthermore, tetranuclear copper-iodide clusters of general formula
[Cu(μ-I)L]4 consisting of a {Cu4X4} core and ligands located apically
have attracted major attention because of their intriguing photophysics,
including dual emission arising from two electronically decoupled ex-
cited states, namely a high-energy (HE) 3XLCT state and low-energy
(LE) 3CC one [8]. Since the pioneering investigation of Ford and co-
workers on the family [Cu(μ-I)(N)]4 (N = nitrogen containing ligand,
e.g. pyridine) [28,41,42] other groups investigated the effect of the
nature of the ligand onto the photoluminescence, electroluminescence
[43] as well as stimuli-responsive properties [44–46] of tetranuclear
cuprous halide clusters [Cu(μ-I)(P)]4 with phosphine ligands. Indeed,
owing to their high structural flexibility, most copper-halide species are
often emissive in the aggregated state only. Noteworthy, their emission
is not only influenced by the nature of the coordination sphere around
the metal atom, but tiny differences induced by the externally induced
modulation of the Cu···Cu distances, molecular packing and chemical
environment may have profound impact on the photophysical proper-
ties of these species [47–50].
2.2. Synthesis and crystal structure of the mononuclear copper complex
1P1A
The monuclear copper(I) complex 1P1A bearing phosphine ligand P1
and pyridine A was prepared in 85% yield by mechanochemical
synthesis by mixing copper iodide CuI with two equivalents of the
phosphine ligand in the presence of pyridine (ca. 20 equiv.) in a mortar
(Scheme 1). The ligand/metal stoichiometry of the product was de-
termined by elemental analyses and then confirmed by X-ray diffraction
studies on single crystal obtained from n-hexane/dichloromethane.
Fig. 1 displays the molecular structure of the compound along with
selected bond distances and angles. Complex 1P1A was crystallized in
the space group P21/c. The complex adopts a mononuclear tetrahedral
coordination geometry. An edge-to-face CH–π intramolecular interac-
tion between the two phosphine ligands was noted [distance of 2.85 Å
between the hydrogen H(24) and C(7)]. The torsion angle between the
pyridine and the Cu-I bond is of ca. 9° [C(37)–N(1)–Cu(1)–I(1)]
(Schemes 2 and 3).
An important motivation in developing copper(I) complexes is their
low cost and their easy synthetic access using simple starting ligands,
especially when considering their applications. Here, we investigated
the potential of alternative and remotely-functionalized phosphine li-
gands that are obtained in a straightforward manner and their impact
onto the photophysical properties of copper-halide species with
2

J. Egly, et al.
InorganicaChimicaActa514(2021)119971
Scheme 1. Synthesis of the mononuclear complex 1P1A of formula [CuI(pyridine)(P1)2] by grinding procedure.
Fig. 1. Single-crystal X-ray molecular structure of copper complex 1P1A
.
Selected bond distances (Å) and angles (°): Cu(1)–N(1), 2.080(2); Cu(1)–P(1),
2.2534(7); Cu(1)–P(2), 2.2588(7); Cu(1)–I(1), 2.6438(4); N(1)–Cu(1)–P(1),
112.55(6); N(1)–Cu(1)–P(2), 108.18(6); N(1)–Cu(1)–I(1), 103.89(6); P(1)–Cu
(1)–P(2), 115.74(2); P(1)–Cu(1)–I(1), 109.824(19); P(2)–Cu(1)–I(1),
105.811(19); C(37)–N(1)–Cu(1)–I(1), 9.04(4).
Scheme 2. Synthesis of binuclear copper(I) complexes of formula [Cu(μ-X)(L)
(P1)]2 by grinding, where L = pyridine (2P1A), quinoline (2P1B) and 4-cyano-
pyridine (2P1C).
2.3. Synthesis of the iodo-bridged binuclear copper complexes 2P1A, 2P1B
and 2P1C
obtained and used for X-ray analysis (Fig. 3). The dinuclear complex
2P1C has a molecular arrangement identical to the previous complex
albeit with a shorter Cu…Cu distance (2.8769 Å).
The dinuclear copper(I) complexes bearing phosphine ligand P1
were prepared by mechanochemical synthesis by mixing stoichiome-
trically CuI and P1 in presence of nitrogen-based ligand pyridine A (20
equiv.), quinoline B (1 equiv.) or 4-cyanopyridine C (1 equiv.), giving
complexes 2P1A, 2P1B and 2P1C, respectively (74–76% yield). All com-
pounds were characterized by 1H, 13C, 31P NMR and elemental analysis
and the data are reported in the experimental section and supporting
information. Crystals of 2P1A suitable for X-ray analysis were obtained
from n-hexane/dichloromethane (Fig. 2). Complex 2P1A was crystal-
lized in the triclinic space group P-1. The copper exhibits a tetrahedral
coordination with P-Cu–N angle of 118.75(5)°. The Cu2I2 geometry is
perfectly planar [Cu(1)–I(1)–Cu(1′)-I(1′) = 0.00] with a Cu(1)–I(1)
distance of 2.65 Å and Cu(1)–I(1′) of 2.71 Å. The Cu…Cu distance is
3.0566 Å indicating no interaction between the two copper atoms as
compared with sum of the van der Waals radius of copper (2.8 Å). The
pendant and flexible ketone arm of the phosphine ligands is pointing
inside the cavity presents on both side of the Cu2I2 square and the ke-
tone function is placed almost parallel to the adjacent pyridine ligand
[C(21)–N(1)–C(3′) –O(1′) = 2.3°]. Crystals of complex 2P1C were also
2.4. Synthesis of the binuclear copper complexes 2P2A, 2P3A, 2P4A
The dinuclear copper (I) complexes 2P2A, 2P3A and 2P4A bearing
phosphine ligands P2, P3 and P4 were prepared by mechanochemical
synthesis by mixing stoichiometrically copper iodide and the phosphine
in presence of 20 equiv. of pyridine A giving the product in yield ran-
ging from 65% to 71%. Among all attempts to get crystals, only Cu
complex 2P4A bearing the itaconic acid-based moiety gave crystals of
sufficient quality for X-ray diffraction studies. Fig. 4 displays the mo-
lecular structure along with selected bond lengths and angles. Complex
2P4A was crystallized in the triclinic P-1 space group. The Cu2I2 geo-
metry is planar and highly symmetric with a Cu(1)-I(1) distance of
2.695 Å and Cu(1)-I(1′) of 2.700 Å and a Cu…Cu distance of 3.005 Å.
The complex is a meso dimer thus consisting of a racemic mixture of
ligand P4. In contrast with the previous structure, the ester functions
point to the outside of the molecule, probably due to their bulk.
3

J. Egly, et al.
InorganicaChimicaActa514(2021)119971
Fig. 3. Single-crystal X-ray molecular structure of copper complex 2P1C
.
Selected bond distances (Å) and angles (deg): Cu(1)-N(1), 2.068(4); Cu(1)-P(1),
2.2366(11); Cu(1)-I(1), 2.6446(5); Cu(1)-I(1′), 2.6854(6); Cu(1)-Cu(1′),
2.8769(9); N(1)-Cu(1)-P(1), 114.02(10); N(1)-Cu(1)-I(1), 103.67(10); P(1)-Cu
(1)-I(1), 116.04(3); P(1)-Cu(1)-I(1′), 103.89(3); I(1)-Cu(1)-I(1′), 114.671(18);
Cu(1)-I(1)-Cu(1′), 65.329(17); Cu(1)-I(1)-Cu(1′)-I(1′), 0.00(3).
Scheme 3. Synthesis of pyridine binuclear copper(I) complexes with phos-
phines P2, P3 and P4.
Fig. 4. Single-crystal X-ray molecular structure of copper complex 2P4A
.
Selected bond distances (Å) and angles (deg): Cu(1)-N(1), 2.0.54(3); Cu(1)-P
(1), 2.2348(10); Cu(1)-I(1), 2.6953(5); Cu(1)-I(1′), 2.6997(5); Cu(1)-Cu(1′),
3.0051(9); N(1)-Cu(1)-P(1), 117.93(10); N(1)-Cu(1)-I(1), 103.41(10); N(1)-Cu
(1)-I(1′), 105.74(9); P(1)-Cu(1)-I(1), 110.41(3); P(1)-Cu(1)-I(1′), 107.08(3); I
(1)-Cu(1)-I(1′), 112.300(17); Cu(1)-I(1)-Cu(1′), 67.700(17); Cu(1)-I(1)-Cu(1′)-I
(1′), 0.00(3).
3P1 was crystallized in the monoclinic P21/c space group and has the
general formula [Cu4I4L4] with L being P1 (Fig. 5). In complex 3P1, the
Cu–I bond distances and I–Cu–I angle values are within the range of
reported values for such type of compound containing phosphorus-
based ligands.[44,46] The copper cluster has a mean Cu…Cu distance of
2.77 Å, which may imply weak cuprophilic interactions.
Fig. 2. Single-crystal X-ray molecular structure of copper complex 2P1A
.
Selected bond distances (Å) and angles (deg): Cu(1)–N(1), 2.0600(17); Cu(1)–P
(1), 2.2311(5); Cu(1)–I(1), 2.7124(3); Cu(1)–I(1′), 2.6533(3); Cu(1)–Cu(1′),
3.0566(5); N(1)–Cu(1)–P(1), 118.75(5); N(1)–Cu(1)–I(1), 106.01(5); N(1)–Cu
(1)–I(1′), 104.45(6); P(1)–Cu(1)–I(1), 101.059(15); P(1)–Cu(1)–I(1′),
115.587(16); I(1)–Cu(1)–I(1′), 110.558(9); Cu(1)–I(1)–Cu(1′), 69.442(9); Cu
(1)–I(1)–Cu(1′)–I(1′), 0.00(4).
2.6. Photophysical characterization
2.5. Synthesis of the cubane-like copper cluster 3P1
Fluid dilute samples in CH2Cl2 solution of the investigated com-
plexes did not display any detectable photoluminescence. This is in line
with previous investigation of related copper-halide species and it was
ascribed to their chemical instability owing to flexible nature of the
complex’s scaffold and ligand dissociation.[8,12,24–26] On the other
hand, all the derivatives were brightly emissive in the solid state as neat
powders at both room temperature and 77 K and the corresponding
photophysical data are summarized in Table 2. All the neat powders
resulted to be thermally- and photo-stable (see Figs. S25–S32)
Silica gel was found to be an excellent medium for the synthesis of
cubane-type complex 3P1 (Scheme 4). The tetranuclear complex was
obtained in quantitative yield by passing solution of complex 2P1A
trough a silica gel column (CH2Cl2 as solvent). Alternatively, complex
3P1 could be synthesized directly by mixing an equimolar amount of
CuI with phosphine ligand 3a in toluene at 100 °C for one day. Suitable
crystals were obtained from dichloromethane/diethyl ether. Complex
4

J. Egly, et al.
InorganicaChimicaActa514(2021)119971
Scheme 4. Transformation of binuclear complex 2P1A into copper cluster 3P1 over silica.
molecular movements present at such cryogenic temperature. The
emission spectra of 1P1A are displayed in Fig. 6 for both temperatures.
Notably, the lowering of the temperature is further accompanied by
a small decrease of the kr, from 1.32 × 104 to 8.4 × 103 s−1. On the
basis of these findings one can thus assume that at low temperature the
radiative process arises from an excited state with an almost pure triplet
nature and admixed 3(M + X)LCT character; whilst, a thermally-as-
sisted equilibration between the lowest-lying 3(M + X)LCT and the
higher-lying 1(M + X)LCT state seems to take place at room tempera-
ture and the observed emission could be tentatively ascribed to the
1
delayed fluorescence arising from an emissive MLCT manifold. Thus,
the spectral shift of ca. 1200 cm−1 (ca. 0.15 eV) provides an estimation
of the energetic gap, namely ΔES-T, between these two excited states
[52]. Although a conclusive attribution of such phenomenon to TADF
would require variable-temperature investigation of the excited state
lifetime, it is worth to notice that these findings are in nice agreement
with related derivatives of the same family reported previously
[9,24–26].
The photophysical properties of the investigated dinuclear com-
plexes show rather striking differences within the series. The corre-
sponding emission spectra are displayed in Fig. 7.
Firstly, we examined compounds 2P1A and compared its emission to
that of [CuI(PPh3)(py)]2 congener reported previously. As far as the
latter is concerned, slightly different data are available in the literature.
In an earlier report, [CuI(PPh3)(py)]2 is described possessing an emis-
sion spectra with maximum at λem = 444 nm at both 298 K and 77 K
with a prolongation of the excited state lifetime upon lowering the
temperature, being τ298K = 11 μs and τ77K = 45 μs.[8] More recently,
Sasaki [12] reported photoluminescence with an emission maximum at
Fig. 5. Single-crystal X-ray molecular structure of copper complex 3P1. Selected
bond distances (Å) and angles (deg): Cu(1)-P(1), 2.2446(16); Cu(1)-I(1),
2.7369(8); Cu(1)-I(3), 2.6376(8); Cu(1)-I(4), 2.7042(8); Cu(1)-Cu(2),
2.7893(10); Cu(1)-Cu(3), 2.7331(10); Cu(1)-Cu(4), 2.7015(10); Cu(2)-P(2),
2.2572(16); Cu(2)-I(2), 2.7108(8); Cu(2)-I(1), 2.7088(8); Cu(2)-I(4), 2.6735(9),
Cu(2)-Cu(3), 2.8016(10); Cu(2)-Cu(4), 2.8835(10); Cu(3)-P(3), 2.2482(16); Cu
(3)-I(1), 2.6562(8); Cu(3)-I(2), 2.6723(8); Cu(3)-I(3), 2.7058(8); Cu(3)-Cu(4),
2.7359(10); Cu(4)-P(4), 2.2473(16); Cu(4)-I(2), 2.6647(8); Cu(4)-I(3),
2.7039(8); Cu(4)-I(4), 2.7414(8); P(1)-Cu(1)-I(1), 98.82(5); P(1)-Cu(1)-I(3),
113.60(5); P(1)-Cu(1)-I(4), 105.04(5); P(1)-Cu(1)-Cu(2), 133.30(5); P(1)-Cu
(1)-Cu(3), 144.58(6); P(1)-Cu(1)-Cu(4), 151.49(6).
λ
em = 500 nm with a bi-exponential decay (τ290k = 22 and 4.2 μs) at
290 K ascribed to an excited state with 3CT character with {Cu2X2} →
π* character. This assignment was as also corroborated by the hypso-
chromic shift to λem = 450 nm (τ80K = 39 μs) observed on cooling the
sample down to 80 K. Nonetheless, we observed a remarkably different
emission behavior for complex 2P1A, which simply differs from [CuI
(PPh3)(py)]2 by the phosphine coordinated onto the {Cu2X2}. Indeed,
2P1A displays an broad and featureless emission profile centered at
λem = 485 nm at room temperature with PLQY = 0.42, which is
bathochromically shifted compared to [CuI(PPh3)(py)]2 as consequence
of the more electron donating nature of the phosphine P1, and with bi-
exponential decay kinetics [τ1,298K = 23.5 μs (60%) and τ2,298K = 8.97
μs (40%), τav = 20.5 μs]. In sharp contrast, the bathochromic shift to
λem = 495 nm (PLQY = 0.96) and the much longer lifetime
(τ77K = 89.0 μs) observed at lower temperature along with the two-fold
decrease of kr point towards the occurrence of a thermally-assisted
delayed fluorescence process and support an emission arising from a
thermally-equilibrated emissive 1(M + X)LCT excited state at room
temperature, lying higher in energy by ΔES-T = 417 cm−1. This dif-
ferent behavior is mostly likely attributable to structural and packing
effects imparted by the substituted phosphine P1 in the aggregated
state. On the other hand, compound 2P1B and 2P1C, which bear the same
phosphine ligand 1a, but different π-accepting heteroaromatic ligands,
microcrystalline samples. The powder X-ray pattern of all the solid-state
samples was recorded and compared with the simulated one obtained
from single-crystal structure (when available), confirming the similar
native structure of the two kinds of samples with the exception of
samples of compound 2P4A. The data are displayed in Figs. S41–S46 of
the supporting information.
Upon photoexcitation, compound 1P1A displays a broad and fea-
tureless emission spectrum with maximum centered at λem = 470 nm
with moderate intensity (PLQY = 0.31) that can be ascribed to an
excited state with charge-transfer (CT) nature and shows a bi-ex-
ponential decay, being τ1 = 25.1 μs (78%), τ2 = 10.3 μs (22%).
Lowering the temperature down to 77 K induces a bathochromic shift of
the emission profile of the powder samples with an emission maximum
at λem = 498 nm, accompanied by sizeable prolongation of the excited
state lifetime (τ = 106.6 μs) and remarkable increase of the emission
efficiency (PLQY = 0.89). This latter can be mainly attributed to the
one order of magnitude decrease of knr as consequence of the reduced
5

J. Egly, et al.
InorganicaChimicaActa514(2021)119971
Table 2
Photophysical data of all the copper-iodide derivatives herein investigated, recorded in the solid state as neat powders at room temperature and 77 K. Excited state
lifetimes were recorded upon excitation at λexc = 375 nm. PLQYs were recorded upon excitation at λexc = 320 nm.
Compound
room temperature
77 K
a [μs]
a [μs]
λem [nm]
PLQY
kr b [×104 s−1
]
knr c [×104 s−1
]
λem [nm]
PLQY
kr b [×104 s−1
]
knr c [×103 s−1
]
1P1A
2P1A
2P1B
2P1C
2P2A
2P3A
2P4A
3P1
470
0.31
0.42
0.32
0.29
0.40
0.32
0.50
0.28
23.5
20.5
20.6
10.3
11.3
12.2
13.6
6.6d
1.32
2.05
1.55
2.82
3.54
2.62
3.68
4.24
2.94
2.83
3.30
6.89
5.31
5.57
3.68
10.9
498
0.89
0.85
0.54
0.34
0.97
0.79
0.85
0.67
106.6
0.84
0.96
0.34
0.64
3.77
1.36
1.14
17.2
1.03
1.69
2.88
12.5
1.17
3.60
2.01
84.6
485
495
89.0
159.8
52.8
25.7
58.3
74.7
595
592
610
598
445
448
465
455
475
475
425 (HE),
605 (LE)
419 (HE),
593 (LE)
3.9 d
a
average lifetimes, , were calculated by using Eq. (2) (see experimental details); b kr were estimated by using the and the employing the following equation
kr = PLQY/ ; c knr were estimated by using the and the employing the following equation knr = (1 − PLQY)/ ; d measured at λem = 605 nm. HE = high-energy
band; LE = low-energy band.
namely quinoline B and 4-cyanopyridine C, respectively, seem to do not
show TADF features. Both complexes show a bathochromic shift of the
emission with respect to complex 2P1A due the more extended π -con-
jugation of the quinoline and 4-cyanopyridine when compared to the
unsubstituted pyridine. Furthermore, while prolongation of the lifetime
is observed upon cooling, the corresponding emission spectrum displays
a small hypsochromic shift that can be attributed to the partial CT
nature of the emissive state, along with a sharpening of the profile that
owing to the rigidification of the molecular skeleton imposed by the
lower temperature. Therefore, it is plausible that the (M + X)CT excited
state admixes with the 3π -π* state that lies at lower energy in 2P1B and
2
P1C owing to the more π -accepting ability of quinoline and 4-cyano-
pyridine ligands. These picture is in agreement with the conclusions
drawn in a previous report on related derivatives and with the small kr
values observed at 77 K that underpin the main involvement of 3π-π *
states at low temperature [12].
Secondly, we compare the photophysics of 2P1A to the results ob-
tained for 2P2A, 2P3A, and 2P4A which all contains pyridine as the π
-accepting moiety, but different phosphine ligand, namely P1, P2, P3
and P4, respectively. The data are summarized in Table 2. It is rea-
sonable to assume that the electron-donating property of the phos-
phines is rather similar, thus one might expect similar photo-
Fig. 6. Emission spectra of compound 1P1A as neat powder at room temperature
and (solid trace) and 77 K (dashed trace) upon excitation at λexc = 300 nm.
luminescence for the compounds in this series. Indeed, compound 2P2A
,
2
P3A and 2P4A display a long-lived emission featuring a broad spectrum
that is hypsochromically shifted by about 40 nm (1853 cm−1), 20 nm
(887 cm−1) and 10 nm (434 cm−1) when compared to 2P1A at room
temperature with PLQY in the range 0.32–0.50 and similar kr values,
indicating that the complexes share the same nature of the emitting
excited state. Although, the more flexible nature of the phosphines in
compounds 2P2A, 2P3A and 2P4A opens for more efficient radiationless
deactivation channels as demonstrated by the increase of knr values.
Lowering the temperature down to 77 K yields a prolongation of the
excited state lifetimes, yet a minor effect onto the corresponding
emission maximum is observed, with no clear evidence of TADF effect.
Overall, it is evident that not only the electronic properties of the co-
ordinated ligands onto the rhombic {Cu2X2} scaffold, but also the solid-
state environment can sizably influence the emissive properties of such
class of compounds. Although the precise reason at the origin of such
spectral shift observed for the series 2P1A, 2P2A, 2P3A and 2P4A, is not
known at the current stage and further investigations are needed in this
direction, these results clearly highlight the importance of the effects
imparted by environment in changing the emission wavelength, colors
purities and TADF processes; these are undoubtedly fundamental
parameters in view of the potential applications of these compounds as
solid state emitters. These factors might include the degree of crystal-
linity and crystalline phases, intermolecular interactions, constrain to
the excited-state structural distortion imposed by the rigid
Fig. 7. Emission spectra of compound 2P1A (black trace), 2P1B (red trace), 2P1C
(light gree trace), 2P4A (blue trace), 2P2A (dark green trace) and 2P3A (orange
trace) as neat powder at room temperature and (solid traces) and 77 K (dashed
traces) upon excitation at λexc = 300 nm. (For interpretation of the references
to colour in this figure legend, the reader is referred to the web version of this
article.)
6

J. Egly, et al.
InorganicaChimicaActa514(2021)119971
states, 3XLCT/3MLCT and 3CC/3XLCT, under thermal equilibrium. In
turn, a fast and efficient population of this latter state may occur even at
77 K, which can still emit efficiently (PLQY = 0.67).
3. Conclusion
A series of eight novel luminescent copper(I) iodide complexes has
been synthesized in good yields by mechanochemistry using easily ac-
cessible functionalized diphenylphosphino-type ligands. Full char-
acterization including X-ray crystallographic studies for five of them
and elemental analyses revealed their nuclearity. These compounds
displayed no detectable photoluminescence in solution, however they
were brightly emissive in the solid state as powders at both room
temperature and low temperature (77 K). Among all investigated de-
rivatives, two of them displayed photophysical features that may un-
derpin TADF processes. In spite of the remote location of the functio-
nalization of the phosphine ligands, noticeable effects were observed
onto the solid-state emission properties thus highlighting the im-
portance of microenvironment for the Cu(I)-halide emitters in the ag-
gregated phase in view of their potential application as active materials
in solid-state light-emitting devices.
Fig. 8. Emission spectra of compound 3P1 as neat powder at room temperature
and (solid trace) and 77 K (dashed trace) upon excitation at λexc = 300 nm.
4. Experimental section
environment, and defects acting as emission traps, to cite a few possi-
bilities [18,53–58].
4.1. General comments
Finally, the emission properties of the tetranuclear complex 3P1 are
evaluated and the spectra are displayed in Fig. 8.
All manipulations were carried under an air atmosphere (except for
mechanosyntheses). Reagents were purchased from commercial che-
mical suppliers and used without further purification. Solvents were
At room temperature, the emission spectra of 3P1 displays two
bands, namely a high (HE) and a low energy (LE) band as typically of
cubane-like copper clusters bearing N-heteroaromatic ligands
[Cu4I4L4],[8,28,41] and phosphines (P) [Cu4I4P4] [44,46,47,59] with
an overall PLQY of 0.32. The two bands are centered at λem = 425 and
605 nm and are confidentially ascribed to two electronically-decoupled
and thermally-equilibrated long-lived excited states with 3XLCT/3MLCT
and 3CC/3XLCT nature (strong Cu 3d → 4s,4p character), respectively,
on the basis of previous investigation on related species. Analysis of the
excited state decay at the LE band results in a bi-exponential kinetics
(τav = 6.6 μs), although no risetime was observed; a value that could be
comparable or shorter than the instrumental resolution employed. In-
terestingly, the maximum of the HE band nicely agree with the value
reported for closely-related [Cu4I4(PPh2Pr)4] derivative, where PPh2Pr
is diphenylpropylphosphine [46]. It is worth to notice that owing to its
nature, the LE band is instead sizably influenced by the extent of me-
tal–metal interaction and distance [8,28,42–42,45–46,49]. As discussed
above, compound 3P1 features an average Cu···Cu bond distance of
2.77 Å, a value that is shorter than the sum of the van der Waals radii
for Cu(I) 2.8 Å [60] and amongst the shortest found for phosphine-
capped cubane-like {Cu4I4} structures,[47] thus highlighting the es-
tablishment of cuprophilic interactions between two adjacent iodo-
bridged d10 metal centers. In consequence, the LE band for compound
3P1 is bathochromically shifted when compared with other [CuIP]4
congeners that typically show emission in the region
λem = 520–580 nm [45–46,49]. Upon lowering the temperature down
to 77 K, the LE band still results in the predominant emission feature
and only a small hypsochromic shift is observed to λem = 593 nm with
concomitant narrower profile, most likely caused by the temperature
induced geometrical distortion of the flexible {Cu4I4} framework that
reduces the metal–metal interaction at low temperature, thus destabi-
lizing the emissive 3CC/3XLCT state [44]. The absence of neat ther-
mochromism in the temperature window under investigation and, thus,
the lack of increase of the relative intensity of the HE band compared to
the LE one at lower temperature compared to other [Cu4I4P4] species
might be attributable to a smaller energetic barrier between the two
dried according to standard procedures. H, 13C{1H} and 31P{1H} nu-
1
clear magnetic resonance (NMR) spectra were recorded on a Bruker
Avance 300 spectrometer aor Bruker Avance III HD − 500 MHz. 13C
assignments were confirmed when necessary with the use of DEPT 135
experiments. 1H and 13C NMR spectra were referenced using the re-
sidual solvent peak (CDCl3: δ H = 7.26 ppm; δ C = 77.16 ppm) at
295 K. Chemical shifts are reported in ppm (δ) compared to TMS (1H
and 13C) using the residual peak of deuterated solvent as internal
standard. MS spectra were performed by the mass spectrometry service
of the “Institut de Chimie de Strasbourg” on microTOF, Bruker
Daltonics. Elemental analyses were performed by the ‘Service d’analyse
élémentaire’ of the Faculté de Chimie of the University of Strasbourg.
For all the investigated complexes, the corresponding H, 13C and 31P
1
NMR spectra are displayed in Figs. S1–S24 and the thermogravimetric
analyses are shown in Figs. S25–S32 of the Supporting Information.
4.2. X-ray analyses
Single crystal X-ray diffraction. For complexes 2P1C, 2P2A and 5, X-
ray diffraction data collection was carried out on a Nonius Kappa-CCD
diffractometer equipped with an Oxford Cryosystem liquid N2 device,
using Mo-Kα radiation (λ = 0.71073 Å). The crystal-detector distance
was 36 mm. The cell parameters were determined (Denzo software)
[61] from reflections taken from one set of 10 frames (1.0° steps in phi
angle), each at 20 s exposure. The structures were solved by direct
methods using the program SHELXS-2013 [62]. The refinement and all
further calculations were carried out using SHELXL-2013 [63]. The H-
atoms were included in calculated positions and treated as riding atoms
using SHELXL default parameters. The non-H atoms were refined ani-
sotropically, using weighted full-matrix least-squares on F2. A semi-
empirical absorption correction was applied using the MULscanABS
routine in PLATON [64].
For complexes 1P1A and 2P1A, X-ray diffraction data collection was
carried out on a Bruker APEX II DUO Kappa-CCD diffractometer
equipped with an Oxford Cryosystem liquid N2 device, using Mo-Kα
7

J. Egly, et al.
InorganicaChimicaActa514(2021)119971
radiation (λ = 0.71073 Å). The crystal-detector distance was 38 mm.
The cell parameters were determined (APEX2 software) [65] from re-
flections taken from tree sets of 12 frames, each at 10 s exposure. The
structure was solved by direct methods using the program SHELXS-97
[66]. The refinement and all further calculations were carried out using
SHELXL-97. The H-atoms were included in calculated positions and
treated as riding atoms using SHELXL default parameters. The non-H
atoms were refined anisotropically, using weighted full-matrix least-
squares on F2. A semi-empirical absorption correction was applied using
SADABS in APEX2.
CDCl3): δ 8.66 (d, 4H, CHpyr, J = 4 Hz), 7.67 (tt, 2H, CHpyr, J = 8 Hz;
2 Hz), 7.57–7.48 (m, 8H, CHph), 7.30 (m, 4H, CHpyr), 7.28–7.20 (m,
12H CHph), 2.64 (m, 4H, CH2–O), 2.45 (m, 4H, CH2–P), 1.93 (s, 6H,
CH3) ppm. 13C NMR (125 MHz, CDCl3): δ 207.40, 150.26, 136.63,
133.40, 133.02 (d); 129.74, 128.53 (d), 124.12, 38.76 (d), 29.78,
21.33(d) ppm. 31P{1H} NMR (202 MHz, CDCl3): δ –17.8 (br) ppm. Anal.
Calcd for C42H44Cu2I2N2O2P2: C, 47.97; H, 4.22; N, 2.66. Found: C,
47.50; H, 4.16; N, 2.40.
5.4. Synthesis of complex 2P1B
4.3. CCDC deposition numbers 2007757–2007761
Copper(I) iodide (148 mg, 0.780 mmol, 1 equiv.) was reacted with
phosphine 1a (200 mg, 0.780 mmol, 1 equiv.) and quinoline (0.092 mL,
0.780 mmol, 1 equiv.) according to the general procedure previously
mentioned to give an orange solid (332 mg, yield 74%). 1H NMR
(500 MHz, CDCl3): δ 9.01 (d, 2H, CHquino, J = 4 Hz), 8.28 (d, 2H,
CHquino, J = 7 Hz), 8.18 (d, 2H, CHquino, J = 8 Hz), 7.82 (d, 2H,
CHquino, J = 8 Hz), 7.69 (m, 2H, CHquino), 7.62–7.53 (m, 10H
CHph + CHquino), 7.40 (dd, 2H, CHquino, J = 4 Hz, 8 Hz), 7.35 (m, 4H,
CHph), 7.30–7.27 (m, 8H, CHph), 2.67 (m, 4H, CH2–O), 2.50 (m, 4H,
CH2-P), 1.94 (s, 6H, CH3) ppm. 13C NMR (125 MHz, CDCl3): δ 207.51,
151.11, 148.07, 136.72, 133.3 (d, J = 13 Hz), 133.06, 129.96, 129.82,
129.65, 128.69 (d, J = 8 Hz); 128.00, 126.92, 121.32, 38.90 (d,
J = 7 Hz), 30.02, 21.17 (d, J = 21 Hz) ppm. 31P{1H} NMR (202 MHz,
CDCl3): δ –24,04 (br) ppm. Anal. Calcd for C50H48Cu2I2N2O2P2: C,
52.14; H, 4.20; N, 2.43. Found: C, 51.97; H, 4.14; N, 2.38.
Powder X-ray diffractometic analyses. The powder XRD patterns
were obtained with a transmission Guinier-like geometry. A linear fo-
calized monochromatic Cu Kα1 beam (λ = 1.5405 Å) was obtained
using a sealed-tube generator (600 W) equipped with a bent quartz
monochromator. The samples were filled in home-made sealed cells of
adjustable path. The patterns were recorded on image plates and
scanned by Amersham Typhoon IP with 25 µm resolution. The intensity
vs 2 theta profiles were obtained from images by using home-developed
software.
The comparison between the simulated (when available from single-
crystal structure) and experimental power diffraction patterns for the
investigated copper complexes are displayed in Figs. S41–S46 of the
Supporting Information.
5. Synthetic procedures
5.5. Synthesis of complex 2P1C
5.1. General procedure for grinding method
Copper(I) iodide (37 mg, 0.195 mmol, 1 equiv.) was reacted with
phosphine 1a (50 mg, 0.195 mmol, 1 equiv.) and 4-cyanopyridine
(20 mg, 0.195 mmol, 1 equiv.) according to the general procedure
previously mentioned to give an orange solid (332 mg, yield 74%).
Suitable crystals for X-Ray analysis were obtained by slow diffusion of
vapor of hexane into a solution of complex in dichloromethane. 1H
NMR (500 MHz, CDCl3): δ 8.81 (d, 4H, CHpyr, J = 4 Hz), 7.57–7.48 (m,
8H, CHph), 7.30 (m, 4H, CHpyr), 7.28–7.20 (m, 12H CHph), 2.64 (m, 4H,
CH2–O), 2,45 (m, 4H, CH2–P), 1,94 (s, 6H, CH3) ppm. 13C NMR
(125 MHz, CDCl3): δ 207.33, 151.00, 133.17 (d, J = 13 Hz), 132.79,
129.82, 128.53 (d, J = 9 Hz), 125.54, 120.68, 116.23, 38.67 (d,
J = 7 Hz), 29.82, 20.99 (d, J = 20 Hz) ppm. 31P {1H} NMR (202 MHz,
CDCl3): δ – 24.03 (br) ppm. Anal. Calcd for C44H42Cu2I2N4O2P2: C,
47.97; H, 3.84; N, 5.09. Found: C, 47.76; H, 3.65; N, 4.99.
In a mortar, copper iodide and pyridine or nitrogen-containing de-
rivative (x equivalents) were grinded together during 5 min. A yellow
solution appeared directly after the addition of pyridine derivative. The
adequate phosphine (one equivalent or two equivalents) was then
added to the solution and the mixture was grinded during 10 min. The
yellow mixture became colorless during the processing. Then di-
chloromethane was added and the solution was poured into Et2O. The
complex precipitated directly, was filtrated and washed several times
with Et2O. The product was dried under vacuum to afford the copper
product.
5.2. Synthesis of complex 1P1A
Copper(I) iodide (75 mg, 0,390 mmol, 1 equiv.) was reacted with
phosphine 1a (200 mg, 0.780 mmol, 2 equiv.) and pyridine (0.63 mL,
7.80 mmol, 20 equiv.) according to the general procedure to give a
white solid (186 mg, yield 85%). Suitable crystals for X-Ray analysis
were obtained by slow diffusion of vapor of n-hexane into a solution of
complex in dichloromethane. 1H NMR (500 MHz, CDCl3): δ 8.63 (br,
2H, CHpyr), 7.68 (t, 1H, CHpyr, J = 7 Hz), 7.45–7.20 (m, 12H, CHph),
7.26 (m, 2H, CHpyr), 7.24–7.19 (m, 8H CHph), 2.60 (br, 4H, CH2-O),
2.43 (br, 4H, CH2-P), 2.00 (s, 6H, CH3) ppm. 13C{1H} NMR (125 MHz,
CDCl3) δ: 207.1; 149.6; 136.3; 133.4; 132.9 (d); 129.7: 128,58 (d);
123.9; 38.6 (d); 29.83; 21.69 (d) ppm. 31P{1H} NMR (202 MHz, CDCl3)
δ: –15.5 (br) ppm. Anal. Calcd for C37H39CuINO2P2: C, 56.82; H, 5.03;
N, 1,79. Found: C, 56.56; H, 4.91; N, 1.27.
5.6. Synthesis of complex 2P2A
Copper(I) iodide (199 mg, 1.05 mmol, 1 equiv.) was reacted with
phosphine 1b (300 mg, 1.05 mmol, 1 equiv.) and pyridine (1.69 mL,
21 mmol, 20 equiv.) according to the general procedure previously
mentioned to give a white solid (378 mg, yield 65%). 1H NMR
(500 MHz, CDCl3): δ 8.66 (d, 4H, CHpyr, J = 4 Hz), 7.65 (tt, 2H, CHpyr
,
J = 8 Hz; 2 Hz), 7.57–7.48 (m, 8H, CHph), 7.31 (m, 4H, CHpyr),
7.28–7.20 (m, 12H CHph), 3.99 (q, 4H, CH2, J = 7 Hz), 2.50 (m, 8H,
CH2–O and CH2–P), 1.14 (t, 6H, CH3, J = 7 Hz) ppm. 13C NMR
(125 MHz, CDCl3): δ 172.91 (d), 150.39, 136.48, 133.18 (d), 132.86,
129.71, 128.54 (d), 124.07, 60.59, 29.54 (d), 22.72(d), 14.20 ppm. 31
P
{1H} NMR (202 MHz, CDCl3): δ –17.82 (br) ppm. Anal. Calcd. for
C
44H48Cu2I2N2O4P2: C, 47.54; H, 4.35; N, 2.52. Found: C, 47.39; H,
5.3. Synthesis of complex 2P1A
4.45; N, 2.45.
Copper(I) iodide (148 mg, 0.780 mmol, 1 eq) was reacted with
phosphine 1a (200 mg, 0.780 mmol, 1 eq.) and pyridine (1.25 mL,
15.6 mmol, 20 eq.) according to the general procedure previously
mentioned to give a white solid (310 mg, yield 76%). Suitable crystals
for X-ray analysis were obtained by slow diffusion of vapor of n-hexane
into a solution of complex in dichloromethane. 1H NMR (500 MHz,
5.7. Synthesis of complex 2P3A
Copper(I) iodide (191 mg, 1.01 mmol, 1 equiv.) was reacted with
phosphine 1c (300 mg, 1.01 mmol, 1 equiv.) and pyridine (1.62 mL,
20.1 mmol, 20 equiv.) according to the general procedure previously
mentioned to give a white solid (412 mg, yield 71%). 1H NMR
8

J. Egly, et al.
InorganicaChimicaActa514(2021)119971
(500 MHz, CDCl3): δ 8.68 (d, 4H, CHpyr, J = 4 Hz), 7.66 (tt, 2H, CHpyr
,
200 kHz–40 MHz) was used to excite the sample in burst mode and
mounted directly on the sample chamber at 90°. The photons were
collected by a PMA Hybrid-07 single photon counting detector. The
data were acquired by using the commercially available software
EasyTau II (PicoQuant GmbH, Germany), while data analysis was per-
formed using the built-in software FluoFit (PicoQuant GmbH,
Germany). All the PLQYs on solid state samples, both crystals and thin-
films, were recorded at a fixed excitation wavelength by using a
Hamamatsu Photonics absolute PLQY measurements system (C9920-
02) equipped with L9700-01 CW Xenon light source (150 W), mono-
chromator, integrating sphere, C7473 photonics multi-channel analyzer
and employing the commercially available U6039-05 PLQY measure-
ment software (Hamamatsu Photonics Ltd., Shizuoka, Japan). All
measurements were repeated 5 times at the excitation wavelength
λexc = 320. Low temperature (77 K) PLQY were measured by using a
calibrated quartz Dewar (Hamamatsu) filled with liquid N2.
J = 8 Hz; 2 Hz), 7.57–7.48 (m, 8H, CHph), 7.31 (m, 4H, CHpyr),
7.28–7.20 (m, 12H CHph), 2.50 (m, 4H, CH2-O), 2.40 (m, 4H, CH2-P),
1.35 (s, 18H, CH3,) ppm. 13C NMR (125 MHz, CDCl3): δ 172.91 (d,
J = 19 Hz); 150.40, 136.50, 133.17 (d, J = 13 Hz), 133.00, 129.67,
128.54 (d, J = 8 Hz); 124.08, 80.55, 30.59 (d, J = 8 Hz), 28.12, 22.68
(d, J = 19 Hz) ppm. 31P {1H} NMR (202 MHz, CDCl3): δ –17.84 (br)
ppm. Anal. Calcd for C48H56Cu2I2N2O4P2: C, 49.37; H, 4.83; N, 2.40.
Found: C, 48.96; H, 4.31; N, 2.27.
5.8. Synthesis of complex 2P4A
Copper(I) iodide (110 mg, 0.580 mmol, 1 equiv.) was reacted with
phosphine 1d (200 mg, 0.580 mmol, 1 equiv.) and pyridine (0.93 mL,
11.6 mmol, 20 equiv.) according to the general procedure previously
mentioned to give a white solid (249 mg, yield 70%). 1H NMR
(500 MHz, CDCl3): δ 8.68 (d, 4H, CHpyr, J = 5 Hz), 7.69 (tt, 2H, CHpyr
,
Methods. For time resolved measurements, data fitting was per-
formed by employing the maximum likelihood estimation (MLE)
methods and the quality of the fit was assessed by inspection of the
reduced χ2 function and of the weighted residuals. For multi-ex-
ponential decays, the intensity, namely I(t), has been assumed to decay
as the sum of individual single exponential decays (Eqn. (1)):
J = 7 Hz, 2 Hz), 7.65–7.50 (m, 8H, CHph), 7.40–7.25 (m, 16H
CHph + CHpyr), 3.49 (s, 6H, CH3), 3.42 (s, 6H, CH3), 3.29 (br, 2H, CH),
2.83–2.50 (m, 8H, CH2) ppm. 13C NMR (125 MHz, CDCl3): δ 173.33,
170.73, 149.11, 135.88, 132.56, 132.43, 132.23, 132.10, 131.41,
128.79 (d, J = 16 Hz); 127.51 (dd, J = 9 Hz, 5 Hz); 127.43, 123.18,
131.12, 51.01, 50.51, 36.73 (d, J = 7 Hz); 35.59 (d, J = 6 Hz); 27.49
(d, J = 14 Hz) ppm. 31P{1H} NMR (202 MHz, CDCl3): δ –17.8 ppm.
Anal. Calcd for C48H52Cu2I2N2O8P2: C, 46.97; H, 4.27; N, 2.28. Found:
C, 46.46; H, 4.05; N, 2.03.
n
t
i
I (t) =
i exp
(1)
i=1
where τ are the decay times and αi are the amplitudes of the compo-
nents at t = 0. In the tables, the percentages to the pre-exponential
factors, αi, are listed upon normalization. Intensity average lifetimes
were calculated by using the following equation (Eqn. (2)): [67].
5.9. Synthesis of complex 3P1
Copper(I) Iodide (0.60 mmol), phosphine (0.60 mmol) and dry to-
luene (5 mL) were placed in a flame-dried Schlenk tube under argon.
The solution was heated at 100 °C during 24 h. Then the mixture was
cool down to room temperature and the solvent was removed under
vacuum. The solid residue was dissolved in CH2Cl2 and the solution was
poured into Et2O. The complex precipitated instantaneously and was
filtered and washed several times with Et2O. The product was dried
under vacuum (yield 92%). Alternatively, complex 3P1 could be ob-
tained from complex 2P1A. Complex 2P1A was dissolved in a minimum of
ethyl acetate and then added to a silica gel chromatography using
EtOAc/cyclohexane (8:2) to give compound 3P1 in quantitative yield.
1H NMR (500 MHz, CDCl3): δ 7.60 (m, 16H, CHarom), 7.33 (m, 8H,
CHarom), 7.20 (m, 16H, CHarom), 2.61 (m, 8H, CH2P), 2.51 (m, 8H,
CH2CH2P), 1.91 (s, 12H, CH3) ppm. 13C NMR (CDCl3, 125 MHz): δ,
207.57 (d, J = 15 Hz), 133.41 (d, J = 11 Hz), 133.30, 130.04, 128.63
(d, J = 6 Hz), 38.84 (d, J = 6 Hz), 30.00, 20.97 (d, J = 17 Hz) ppm.
2
2
a1 + a2
1
2
=
a1 1 + a2
(2)
2
Time resolved emission decay traces along with the fitting curves
and residuals are reported as supplementary materials in Figs. S33–S40.
Author Statement
Conceptualization: S. Bellemin-Laponnaz (SBL), P. Steffanut (PS).
Funding acquisition: SBL, PS, M. Mauro (MM). Investigation: J. Egly
(JE), D. Bissessar (DB), B. Heinrich (BD). Methodology: T. Achard (TA),
MM, SBL. Project Administration: SBL. Ressources: JE, DB, TA, PS, MM,
SBL. Supervision: MM, SBL. Validation: MM, SBL. Visualization: JE, BH,
MM, SBL. Writing Original Draft: MM, SBL.
CRediT authorship contribution statement
Julien Egly: Investigation, Formal analysis, Visualization. Damien
Bissessar: Investigation, Formal analysis, Visualization. Thierry
Achard: Methodology. Benoît Heinrich: Investigation, Formal ana-
lysis, Visualization. Pascal Steffanut: Conceptualization, Funding ac-
quisition, Resources. Matteo Mauro: Funding acquisition,
Methodology, Resources, Supervision, Validation, Visualization,
Writing - original draft, Writing - review & editing. Stéphane
31P{1H} NMR (202 MHz, CDCl3) δ: –29.5 ppm. FTIR:
(pure, dia-
mond orbit) = 3053, 2912, 1710, 1575, 1487, 1434, 135m6a,x1215, 1159,
1099, 868, 739, 693 cm−1. Anal. Calcd for C64H68Cu4I4O4P4: C, 43.02;
H, 3.84 Found: C, 43.61; H, 3.92.
6. Photophysics
Bellemin-Laponnaz:
Conceptualization,
Funding
acquisition,
Instrument details. Steady-state emission spectra were recorded on a
Horiba Jobin − Yvon IBH FL-322 Fluorolog 3 spectrometer equipped
with a 450 W xenon arc lamp, double-grating excitation, and emission
Methodology, Project administration, Resources, Supervision,
Visualization, Writing - original draft.
monochromators (2.1 nm mm−1 of dispersion; 1200 grooves mm−1
)
Declaration of Competing Interest
and a Hamamatsu R13456 red sensitive Peltier-cooled PMT detector.
Emission and excitation spectra were corrected for source intensity
(lamp and grating) and emission spectral response (detector and
grating) by standard correction curves. Time-resolved measurements
were performed using either the Time-Correlated Single-Photon
Counting (TCSPC) or the Multi Channel Scaling (MCS) electronics op-
tion of the TimeHarp 260 board installed on a PicoQuant FluoTime 300
fluorimeter (PicoQuant GmbH, Germany), equipped with a PDL 820
laser pulse driver. A pulsed laser diode LDHePeCe375 (λ = 375 nm,
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
Acknowledgments
Financial support for this project was provided by the Région Grand
Est (France) and Clariant (Muttenz, Switzerland). Dr. Lydia Brelot and
pulse full width at half maximum
<
50 ps, repetition rate
9

J. Egly, et al.
InorganicaChimicaActa514(2021)119971
Corinne Bailly are gratefully acknowledged for X-ray crystallographic
analyses. Prof. Cristian A. Strassert, M. E. Gutierrez Suburu and I.
Maisuls (Westfälische Wilhelms-Universitët Münster) are gratefully
acknowledged for the help with the PLQY measurements.
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