Synthesis and photophysical properties of copper(I) complexes obtained from 1,10-phenanthroline ligands with increasingly bulky 2,9-substituents

Article abstract of DOI:10.1002/ejic.200900954

In this paper, we describe the synthesis and the electronic properties of a series of [Cu(NN)₂]⁺ systems. The NN ligands investigated are 2,9-bis[(tert-butyldimethylsilyloxy)methyl]1,1.0-phenanthroline (1), 2,9-bis[(triisopropylsilyloxy)methyl]-l,1.0-phenanthrollne (2), 2,9-bis[(tert-butyldiphenylsilylmoxy)ethyl]-l,10-phenanthroline (3), 2,9-bis[2,6-bis(benzyloxy)phenethyl]-l,10-phenanthroline (4) and 2-(l,3-diphenylpropan-2-yl)-9-phenethyl-l,10-phenanthroline (5), The electrochemical properties and the ground state electronic absorption spectra of Cu(1)₂-Cu(5)₂ are in line with the classical behaviour of such [Cu(NN)₂]⁺ derivatives. Whereas all the compounds exhibit MLCT luminescence centered around. 630-650 nm, the emission quantum yields and the lifetimes are dramatically different as a function of stereoelectronic effects and/or the possibility of internal exciplex quenching when oxygen-containing functional groups are attached, to the phenanthroline ligands.

Full text of DOI:10.1002/ejic.200900954

FULL PAPER
DOI: 10.1002/ejic.200900954
Synthesis and Photophysical Properties of Copper(I) Complexes Obtained from
1,10-Phenanthroline Ligands with Increasingly Bulky 2,9-Substituents
Gianluca Accorsi,[a] Nicola Armaroli,*[a] Carine Duhayon,[b] Alix Saquet,[b]
Béatrice Delavaux-Nicot,*[b] Richard Welter,[c] Omar Moudam,[b,d] Michel Holler,[d] and
Jean-François Nierengarten*[d]
Keywords: Luminescence / Copper / Electrochemistry / Electronic structure / Phenanthroline
In this paper, we describe the synthesis and the electronic
properties of a series of [Cu(NN)2]+ systems. The NN ligands
investigated are 2,9-bis[(tert-butyldimethylsilyloxy)methyl]-
1,10-phenanthroline (1), 2,9-bis[(triisopropylsilyloxy)meth-
yl]-1,10-phenanthroline (2), 2,9-bis[(tert-butyldiphenylsilyl-
moxy)ethyl]-1,10-phenanthroline (3), 2,9-bis[2,6-bis(benzyl-
oxy)phenethyl]-1,10-phenanthroline (4) and 2-(1,3-diphen-
ylpropan-2-yl)-9-phenethyl-1,10-phenanthroline (5). The
electrochemical properties and the ground state electronic
absorption spectra of Cu(1)2–Cu(5)2 are in line with the clas-
sical behaviour of such [Cu(NN)2]+ derivatives. Whereas all
the compounds exhibit MLCT luminescence centered
around 630–650 nm, the emission quantum yields and the
lifetimes are dramatically different as a function of stereo-
electronic effects and/or the possibility of internal exciplex
quenching when oxygen-containing functional groups are
attached to the phenanthroline ligands.
anthroline is a good π* electron accepting molecule. Ac-
cordingly, [Cu(NN)2]+ may exhibit metal-to-ligand-charge-
transfer (MLCT) absorption bands at relatively low energy,
typically in the range 380–700 nm.[15–16] These features im-
part a marked color to these complexes which range from
orange, to deep red to magenta, depending on the relative
intensity of the various MLCT transitions, in turn related
to the specific symmetry of the complex. [Cu(NN)2]+ with
properly substituted phenanthroline ligands are also char-
acterized by a relatively long-lived MLCT emission in the
visible (Vis) spectral region. Over the years, substantial
elongation of the excited state lifetime has been pursued by
rational ligand design that has made [Cu(NN)2]+ potential
alternatives to popular RuII-polypyridine complexes,[14,16,18]
because of the larger abundance and smaller environmental
impact of Cu compared to Ru. Thus Cu complexes are by
far more attractive for potential applications such as dye-
sensitized sroline complex, [Cu(dtbp)2]+ (dtbp = 2,9-di-tert-
butyl-1,10-phenanthroline), which exhibits the longest
MLCT emission lifetime (τ = 3260 ns) and largest emission
quantum yield (Φ = 5.6%) ever reported for [Cu(NN)2]+
derivatives.[21,22] However, despite its outstanding photo-
physical properties, [Cu(dtbp)2]+ undergoes facile ligand re-
placement reactions, where one dtbp ligand is lost. Thus,
this compound is not very stable in the presence of nucleo-
philes and coordinating solvents. Indeed, even weakly coor-
dinating solvents such as acetone are capable of displacing
one dtbp ligand.[22] Therefore, substantial research efforts
are still needed to develop stable luminescent [Cu(NN)2]+
derivatives.
Introduction
1,10-Phenanthroline and its derivatives have been studied
for decades as versatile chelating agents,[1,2] analytical
probes,[3] DNA intercalators,[4] building blocks for multi-
component architectures[5–10] and molecular machines.[11]
One of the most successful fields of exploitation of these
ligands in coordination chemistry is concerned with the
preparation of CuI complexes. CuI-bisphenanthroline com-
plexes, [Cu(NN)2]+, display distorted tetrahedral geometries
due to intra- and intermolecular (in solid state crystals) π-
stacking interactions which are dictated by the size, chemi-
cal nature, and position of the phenanthroline substitu-
ents.[12–16]
CuI is characterized by a d10 electronic configuration[17]
and exhibits a low oxidation potential, whereas phen-
[a] Molecular Photoscience Group, Istituto per la Sintesi Organica
e la Fotoreattività, Consiglio Nazionale delle Ricerche,
Via Gobetti 101, 40129 Bologna, Italy
E-mail: nicola.armaroli@isof.cnr.it
[b] Laboratoire de Chimie de Coordination du CNRS,
205 route de Narbonne, 31077 Toulouse Cedex 4, France
E-mail: beatrice.delavaux-nicot@lcc-toulouse.fr
[c] Laboratoire DECOMET, Université de Strasbourg,
4 rue Blaise Pascal, 67000 Strasbourg, France
E-mail: welter@chimie.u-strasbg.fr
[d] Laboratoire de Chimie des Matériaux Moléculaires, Université
de Strasbourg et CNRS (UMR 7509), Ecole Européenne de
Chimie, Polymères et Matériaux (ECPM),
25 rue Becquerel, 67087 Strasbourg Cedex 2, France
E-mail: nierengarten@chimie.u-strasbg.fr
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.200900954.
164
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Synthesis and Photophysical Properties of Copper(I) Complexes
The effects on the intensity and color of the MLCT lumi-
A completely different approach to improve substantially
nescence band and on its related lifetime is attributed to the luminescence performance of CuI complexes is that of
geometric distortions that occur upon light excitation, when using heteroleptic coordination with imine- and phosphane-
the metal center changes its formal oxidation state from CuI type ligands, [Cu(NN)(PP)]+.[30,17] Unfortunately, [Cu(NN)-
to CuII and tend to assume a more flattened geometry.[15–16] (PP)]+ complexes often exhibit poor stability in solution
The flattening process was proposed by McMillin and co- and are more difficult to handle, making [Cu(NN)2]+ still
workers 20 years ago on the basis of classical photochemi- preferable in this regard. Here we present the synthesis, X-
cal experiments on series of [Cu(NN)2]+ complexes with in- ray crystal structures, electrochemistry, and photophysical
creasingly nucleophilic counteranions.[23] In recent years it properties of five novel [Cu(NN)2]+ complexes, exhibiting
has been confirmed by means of ultrafast transient absorp- rather different luminescence performance (see Schemes 1
tion and light-initiated time-resolved X-ray absorption and 2). To the best of our knowledge and by excluding the
spectroscopy (LITR-XAS).[24] The latter pump-and-probe unique and outstanding [Cu(dtbp)2],[22] Cu(5)2, is one of the
technique allows one to catch the transient oxidation state longest-lived [Cu(NN)2]+ emitters reported so far, with τ =
of a metal atom as well as its surrounding structures follow- 420 ns in oxygen-free CH2Cl2 solution.
ing photoexcitation via an ultrafast laser source. Practically,
the information obtained via LITR-XAS is a sort of snap-
shot of electronic excited states in disordered media (e.g.
solution), which are generated via a UV/Vis femtosecond
pump laser and subsequently probed with a 30–100 ps in-
tense X-ray pulse produced by 3rd generation large syn-
chrotron facilities.[25] Analogous investigations can be car-
ried out also on CuI complexes as solid crystals (“photo-
crystallography”).[26]
Recent fluorescence upconversion studies conclude that
flattening distortions in [Cu(NN)2]+ occur on a timescale
below 100 fs,[27] i.e. shorter that proposed before.[28–29] Im-
portantly, the distortion tends to reduce the excited state
lifetime of the luminescent level, due to parasite non radia-
tive quenching processes that involve binding of solvent
molecules and counterions to form pentacoordinate species.
To limit these undesired effects two strategies are typically
followed, i.e. choosing bulky substituents at the phen-
anthroline ligands that shield the metal site from inter-
molecular attack and selecting poor electron donor solvents
such as toluene or CH2Cl2 instead of CH3CN or
CH3OH.[14]
Scheme 2. Reagents and conditions: (a) KDA, THF, –78 °C then
2,6-dibenzyloxybenzyl bromide (49%); (b) KDA (3 equiv.), THF,
–78 °C then benzyl bromide (4 equiv.) (44%); (c) Cu(CH3CN)4BF4,
CH2Cl2, CH3CN [Cu(4)2: 60%; Cu(5)2: 50%].
Results and Discussion
Synthesis
The preparation of complexes Cu(1)2–Cu(3)2 is depicted
Scheme 1. Reagents and conditions: (a) TBDMSCl, DMF, imid-
in Scheme 1. Compound 6 was prepared according to a pre-
azole (80%); (b) TIPSCl, DMF, imidazole (73%); (c) TBDPSCl,
viously published procedure.[31] Protection of the two
DMF, imidazole (84%); (d) Cu(CH3CN)4BF4, CH2Cl2, CH3CN
[Cu(1)2: 73%; Cu(2)2: 76%; Cu(3)2: 73%].
alcohol groups of 6 with silylated protecting groups appear
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165

N. Armaroli, B. Delavaux-Nicot, J.-F. Nierengarten et al.
FULL PAPER
indeed as an easy way to increase the size of the 2,9-substit- resulting packing forces induce a significant rocking (ca.
uents of the 1,10-phenanthroline ligand. Reaction of 6 with 16.6°) of both phenanthroline ligands as schematically
tert-butyldimethylchlorosilane (TBDMSCl) in the presence shown in Figure 1 (C–D). This rocking distortion facilitates
of imidazole gave the TBDMS-protected ligand 1 in 80% the intermolecular phenanthroline-phenanthroline interac-
yield. Ligands 2 and 3 were prepared under similar condi- tions in the crystal lattice and produce an exceptionally
tions from the reaction of 6 with tri-isopropylchlorosilane large N(1)–Cu(1)–N(4) bond angle (139.40°) as well as a
(TIPSCl) and tert-butyldiphenylchlorosilane (TBDPSCl), lengthening of the Cu(1)–N(2) and Cu(1)–N(3) bonds when
respectively. The corresponding CuI complexes Cu(1)2– compared to the Cu(1)–N(1) and Cu(1)–N(4) bonds
Cu(3)2 were obtained in 73 to 76% by treatment of ligands (Table 1).
1–3 with Cu(CH3CN)4BF4 in CH2Cl2/CH3CN at room
temperature. The coordination of the phenanthroline ligand
to the CuI cation was easily observed by an instantaneous
color change of the solution upon addition of the CuI salt.
Actually, the colorless ligand solution became orange-red
due to the apparition of the MLCT band characteristic of
bis(2,9-disubstituted-1,10-phenanthroline)CuI derivatives
(vide infra). Compounds Cu(1)2–Cu(3)2 were characterized
Table 1. Bond lengths [Å] and angles [°] within the coordination
spheres for Cu(1)2 and Cu(5)2 (see Figures 1 and 2 for the number-
ing).
Cu(1)2
Cu(5)2
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–N(3)
Cu(1)–N(4)
N(1)–Cu(1)–N(2)
N(1)–Cu(1)–N(3)
N(1)–Cu(1)–N(4)
N(2)–Cu(1)–N(3)
N(2)–Cu(1)–N(4)
N(3)–Cu(1)–N(4)
2.007(3)
2.064(3)
2.053(3)
2.010(3)
82.5(1)
121.4(1)
139.4(1)
126.3(3)
120.4(1)
82.6(1)
2.031(7)
2.032(6)
2.026(7)
2.040(6)
82.6(3)
126.9(3)
120.3(3)
126.3(3)
123.9(3)
82.5(3)
1
by H- and 13C-NMR spectroscopy and elemental analysis.
Crystals suitable for X-ray crystal-structure analysis were
obtained by slow diffusion of Et2O into a CH2Cl2 solution
of Cu(1)2. The ORTEP drawing of the cationic moiety of
Cu(1)2 is depicted in part A of Figure 1. As typically seen
for copper phenanthroline complexes,[32] packing induced
distortions from an idealized pseudotetrahedral geometry
are observed. However, unlike what is typically seen in the
The synthesis of compounds Cu(4)2 and Cu(5)2 is de-
solid-state structures of related copper(I) complexes,[32] picted in Scheme 2. Ligand 4 was obtained from the reac-
there is no flattening of the two ligands relative to one an- tion of the dicarbanion derived from neocuproine (7)[33]
other (towards a square-planar geometry) as a consequence with 2,6-dibenzyloxybenzyl bromide. When the dicarbanion
of the packing. Indeed, close inspection of the crystal pack- was prepared from treatment of 7 with lithium diisopropyl
ing reveals columnar arrays in which intermolecular π- amide (LDA) in THF, the desired dialkylated product was
stacking interactions between the phenanthroline rings of obtained in low yields (Ͻ20%). In an attempt to optimize
neighboring Cu+(1)2 cations take place (Figure 1, B). The the preparation of ligand 4, the reaction was performed un-
Figure 1. (A) ORTEP view with partial numbering of the cationic part of complex Cu(1)2. The hydrogen atoms have been omitted for
clarity. Thermal ellipsoids include 30% of the electron density. (B) Stacking within the Cu(1)2 lattice highlighting the intramolecular π-π
stacking interactions between neighboring cations. (C) Schematic view showing how the packing forces induce the rocking distortion.
(D) Detailed view of the coordination sphere around the CuI cation highlighting the rocking of both phenanthroline ligands.
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Synthesis and Photophysical Properties of Copper(I) Complexes
der the conditions developed in the group of Gorman for boring Cu+(5)2 cations. Importantly, the six peripheral
the synthesis of dialkylated bipyridines.[34] Indeed, the use phenyl groups prevent intermolecular π-interactions involv-
of potassium diisopropyl amide (KDA) as base to depro- ing the phenanthroline subunits and thus the distortion of
tonate 7 followed by reaction with 2,6-dibenzyloxybenzyl the coordination sphere around the CuI cation. Further sta-
bromide led to an acceptable yield (49%) of the desired bilization is also provided by several intramolecular face-to-
product 4. By applying the same reaction conditions with edge π-stacking interactions involving the phenanthroline
benzyl bromide (2.5 equiv.) as electrophile, 2,9-diphenethyl- moiety of one ligand and two phenyl subunits of the other
1,10-phenanthroline[33] was isolated as the main product in one (Figure 2, B–C).
40% yield. Under these conditions, mono- and tri-alkylated
derivatives were also produced. When an excess of KDA
(3 equiv.) and benzyl bromide (4 equiv.) was used, the de-
sired trialkylated product 5 was isolated in 44% yield. It
Electrochemistry
can be noted that with larger excesses of KDA (4 equiv.)
The electrochemical properties of Cu(1)2–Cu(5)2 were de-
and benzyl bromide (6 to 8 equiv.), the trialkylated deriva- termined by cyclic voltammetry (CV) and Osteryoung
tive 5 was always the major product (40 to 45%) and no Square Wave Voltammetry (OSWV). All the experiments
traces of tetraalkylated products were detected. Finally, were performed at room temperature in CH2Cl2 solutions
treatment of ligands 4 and 5 with Cu(CH3CN)4BF4 in containing
CH2Cl2/CH3CN at room temperature gave the CuI com- (0.1 ) as supporting electrolyte and ferrocene (Fc) as in-
plexes Cu(4)2 and Cu(5)2, respectively. ternal reference, with a Pt disk as the working electrode and
tetra-n-butylammonium
tetrafluoroborate
The air stable complexes Cu(4)2 and Cu(5)2 were charac- a saturated calomel electrode (SCE) as a reference. Potential
terized by 1H- and 13C-NMR spectroscopy and their purity data for all of the complexes are collected in Table 2. In the
confirmed by elemental analysis. Complex Cu(5)2 was fur- anodic region, all the copper(I) complexes Cu(1)2–Cu(5)2
ther characterized by X-ray crystallography. The ORTEP show a reversible one-electron process assigned to the oxi-
drawing of the cationic moiety of Cu(5)2 is shown in Fig- dation of the metal center.[35] As far as the cathodic region
ure 2 (A). The dihedral angle between the ligands plane is is concerned, the typical reduction centered on the phenan-
almost 90°. As a consequence, the four Cu–N distances are throline ligand[35] could not be observed in the available po-
similar and the geometry of the copper/nitrogen framework tential window.
quite regular (Table 1) by comparison with other CuI bis-
The oxidation of CuI to CuII is accompanied by the re-
(phenanthroline) complexes.[32] Close inspection of the crys- arrangement from a pseudotetrahedral coordination geom-
tal packing reveals a network of intermolecular π-stacking etry to a distorted square planar one.[35] This process is
interactions between the different phenyl rings of neigh- strongly affected by the size of the substituent attached to
Figure 2. (A) ORTEP view with partial numbering of the cationic part of complex Cu(5)2. The hydrogen atoms have been omitted for
clarity. Thermal ellipsoids include 30% of the electron density. Space filling (B), and ball and stick (C) representations of the cationic
part of Cu(5)2 highlighting the intramolecular face-to-edge π-stacking interactions; a: 2.75 Å [distance from C(31)–H to the plane of the
phenanthroline]; b: 2.86 Å [distance from C(1)–H to the plane of the phenanthroline]; c: 2.83 Å [distance from C(70)–H to the plane of
the phenanthroline]; d: 2.86 Å [distance from C(40)–H to the plane of the phenanthroline].
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FULL PAPER
Table 2. Electrochemical data on the oxidation of the copper(I)
complexes determined by CV and OSWV on a Pt working electrode
in CH2Cl2 + 0.1  nBu4NBF4 at room temperature.
CV[a]
OSWV[b]
Cu(1)2
Cu(2)2
Cu(3)2
Cu(4)2
Cu(5)2
+0.99 (110)
+1.15 (100)
+1.19 (110)
+0.98 (100)
+1.28 (90)
+0.99
+1.16
+1.20
+0.98
+1.28
[a] Values for (Epa + Epc)/2 given in Volt vs. SCE and ∆Ep in mV
(in parenthesis) at a scan rate of 100 mVs–1. [b] OSWV values were
obtained using a sweep width of 20 mV, a frequency of 10 Hz, and
a step potential of 5 mV; values are given in Volt vs. SCE.
the phenanthroline ligand. Indeed, bulkier substituents on
the phenanthroline ligand hinder the formation of a more
flattened structure appropriate for the CuII oxidation state.
This rationale perfectly explains the positive shift when go-
ing from Cu(1)2 to Cu(3)2 as a result of the increasing size
of the silyl protecting groups. This effect is even stronger in
the case of Cu(5)2 for which the oxidation is the most diffi-
cult. Indeed, this is in good agreement with the X-ray crys-
tal structure analysis of Cu(5)2 which revealed how the six
peripheral phenyl subunits prevent significant distortion of
the coordination geometry of the copper center. In contrast,
the oxidation process is almost not affected by substituents
that are attached too far from the phenanthroline ligand.
Effectively, the benzyloxy subunits of Cu(4)2 have no signifi-
cant effect on the redox potential of the CuII/CuI couple.
Indeed, the potential value observed for Cu(4)2 is similar to
the one observed for the corresponding unsubstituted cop-
per(I) complex prepared from the 2,9-diphenethyl-1,10-
phenanthroline.[36] It appears that the benzyloxy groups of
Cu(4)2 are not capable of significantly preventing the distor-
tion of the coordination sphere around the copper center.
Figure 3. (a) Absorption spectra of Cu(1)2 (empty square), Cu(2)2
(dotted line), Cu(3)2 (dashed line) in toluene and Cu(4)2 (grey line)
and Cu(5)2 (black line) in CH2Cl2. For the sake of clarity the visible
spectral region is multiplied by a factor of ten. The spectra of
Cu(1)2 and Cu(2)2 are truncated at 290 nm, limit of the optical
window of toluene. (b) Emission spectra of Cu(4)2 and Cu(5)2 in
CH2Cl2 (298 K, λexc = 450 nm); relative intensities reflect the mag-
nitude of the corresponding quantum yields. The emission spectra
of Cu(1)2–Cu(3)2 are extremely weak and have been omitted. (c)
Luminescence decays of Cu(4)2 and Cu(5)2, λexc = 407 nm, oxygen-
free solutions.
As detailed above, the MLCT emissive excited state of
[Cu(NN)2]+ complexes is populated after extensive molecu-
lar rearrangements, in particular flattening distortion of the
initial pseudo-tetrahedral Franck-Condon geometry and
expansion of the coordination number.[29,15] When the li-
gand skeleton provides stronger rigidity to the complex, i.e.
limited chance of rearrangement, the emission performance
and excited state lifetime tend to increase.
In the present case the emission bands of Cu(1)2–Cu(3)2
are barely detectable in CH2Cl2, which is the classical sol-
vent for [Cu(NN)2]+, because it offers the best compromise
between solubility power and little emission quenching by
nucleophilic attack.[14] Less nucleophilic solvents such as
Photophysical Properties
In Figure 3 are depicted the absorption spectra of toluene can hardly solubilize ionic species like [Cu(NN)2]+,
Cu(1)2–Cu(5)2 in toluene or dichloromethane solutions. The which could thus be studied in this solvent only very
UV spectral window is characterized by intense ligand-cen- rarely.[29] Quite unexpectedly, Cu(1)2–Cu(3)2 turned out to
tered (LC) bands typical of the ππ* transitions of the phen- be reasonably soluble in toluene, so as to enable the deter-
anthroline ligands, with molar absorption coefficients (ε) of mination of molar absorption coefficient values (Figure 3).
the order of 50,000–60,000 –1 cm–1.[2] The bands lying in However, also in this solvent, very weak emission bands
the VIS spectral region (≈ 380–600 nm) are much weaker were detected with quantum yields lower than 1ϫ10–5 (Fig-
than those in the UV and are assigned to MLCT electronic ure S1) and lifetimes of just a few nanoseconds (Table 3).
transitions.[15,16] Their shape and relatively high intensity These values are even much smaller than those of [Cu-
are typical of phenanthrolines with alkyl-type substituents (dmp)2]+ (dmp
=
2,9-dimethyl-1,10-phenanthroline,
at the 2 and 9 position,[37] which are substantially different 72 ns)[37] that, in principle, is expected to offer a more lim-
from those with phenyl residues.[38] The substantial similar- ited steric protection to the excited molecule, compared to
ity between the MLCT absorption features [Cu(1)2– Cu(1)2–Cu(3)2, with its tiny methyl residue. This suggests an
Cu(3)2 and Cu(4)2–Cu(5)2, in particular, are virtually iden- active role of the silyloxy groups in depressing the emission
tical] suggests that the ground state symmetry and elec- performance, most likely via internal nucleophilic quench-
tronic configuration of the complexes is pretty much the ing by the oxygen atom. This effect has been already ob-
same along the series. By contrast (vide infra) luminescence served earlier, both at room temperature[37] and at 77 K,[39]
properties suggest marked differences in the excited state in [Cu(NN)2]+ with appended fragments bearing N or O
behaviour.
atoms.
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Synthesis and Photophysical Properties of Copper(I) Complexes
Table 3. Photophysical data in solution, low-temperature rigid matrix and solid state as powder.
Solution (298 K)
Rigid matrix (77 K)
Solid state (298 K)
[b]
λmax[a] [nm]
Φem
τ[c] [ns]
λmax[a] [nm] τ[c] [µs]
λmax[a] [nm] τ[c] [µs]
Cu(1)2
Cu(2)2
Cu(3)2
Cu(4)2
652[d]
Ͻ 1ϫ10–5[d]
(Ͻ 1ϫ10–5)[d]
Ͻ 1ϫ10–5[d]
(Ͻ 1ϫ10–5)[d]
Ͻ 1ϫ10–5[d]
(Ͻ 1ϫ10–5)[d]
2.2ϫ10–4[e]
2.8[d]
650[d]
632[d]
640[d]
642[e]
3.4[d]
5.2[d]
4.9[d]
5.4[e]
652
648
622
645
0.024
0.030
0.87
644[d]
650[d]
668[e]
2.4[d]
6.0[d]
6.1, 15%[e,f]
85.9, 85%[e,f]
(6.1, 19%)[e,f]
(95.3, 81%)[e,f]
9.3, 2%[e,f]
309, 98%[e,f]
(420)
0.49
(2.5ϫ10–4)[e]
Cu(5)2
638[e]
1.9ϫ10–3[e]
638[e]
6.3[e]
626
1.3
(2.6ϫ10–3)[e]
[a] Emission maxima from spectra uncorrected for the detector response. [b] Emission quantum yields in air-equilibrated and, in brackets,
in oxygen-free solution. [c] Excited state lifetimes in air-equilibrated and, in brackets, in oxygen-free solution. [d] Toluene. [e] CH2Cl2. [f]
The percentage value is the relative amplitude of the decay components.
The emission spectra of Cu(4)2–Cu(5)2 in CH2Cl2 solu- which might foster peculiar intramolecular (see above) and
tion at room temperature are reported in Figure 3. The re- perhaps even intermolecular quenching effect for this com-
lated quantum yields and excited state lifetimes are gathered plex, yielding complex decay kinetics.
in Table 3 and are at least one order of magnitude larger
Notably, for Cu(5)2, the emission decay detected in oxy-
than those of Cu(1)2–Cu(3)2. This substantially different gen free CH2Cl2 solution exhibits a negligibly weak short
performance can be explained with the better protection of- component and can be well fitted monoexponentially (Fig-
fered by the bulkier phenanthroline substituents in 4 and 5 ure 3). A lifetime of 420 ns is thus calculated, i.e. one of
relative to 1–3. It has to be emphasized that Cu(5)2 exhibits the longest detected to date for conventional [Cu(NN)2]+
a particularly good MLCT luminescence quantum yield for homoleptic complexes.[14,15] The longer lifetime component
a conventional bisphenanthroline copper(I) complex[15] (Φ of the less sterically protected Cu(4)2 is substantially
= 2.6ϫ10–3 in oxygen free solution), whereas the value of shorter, i.e. 95.3 ns.
Cu(4)2 is 10 times lower (Figure 3). This remarkably dif-
Cu(1)2–Cu(5)2 were also investigated in solid state as
ferent emission behavior could be related again to the pres- powder (room temperature) and in rigid matrix at 77 K
ence of oxygen atoms in the phenanthroline substituents of (Figure 4, Table 3). The most notable result is the substan-
4, which may prompt internal exciplex quenching, as dis- tial increase of the excited state lifetime of Cu(1)2–Cu(3)2 at
cussed above for Cu(1)2–Cu(3)2. Electrochemical data are in 77 K, compared to solutions. Hence, for the whole series,
line with the good performance of Cu(5)2, which exhibits lifetime values of a few µs are measured, in line with MLCT
the highest oxidation potential, i.e. it is the least prone to lifetimes of [Cu(NN)2]+ in low temperature matrices.[37] The
undergo molecular rearrangements upon oxidation.[40] The emission intensity, albeit non obtainable quantitatively un-
remarkable differences in the emission quantum yields be-
tween Cu(1)2–Cu(3)2 and Cu(4)2–Cu(5)2 are in line with the
trend of MLCT excited state lifetimes. Cu(1)2–Cu(3)2 exhi-
bit a lifetime of a few ns in toluene solution, unaffected by
the removal of oxygen. In the case of Cu(4)2–Cu(5)2 double
exponential luminescence decays are found, with minor (rel-
ative amplitude Յ 15%) shorter components of a few ns
(Table 3). Bicomponent emission decays were already found
earlier for [Cu(NN)2]+ but, in these cases, the shorter life-
times were much smaller than found here (ϽϽ 1 ns) and
associated with emission from the singlet level (1MLCT)[41]
or to excited states that have not yet undergone structural
rearrangements.[42] The longer values in the present com-
plexes (ca. 6 ns) can be hardly related to dynamic structural
phenomena also because, recently, it has been suggested
that they occur in the sub picosecond timescale.[27] The mul-
Figure 4. Emission spectra of Cu(3)2 (dashed line), Cu(4)2 (grey
line) and Cu(5)2 (black line) in the solid state as powder (left;
tiexponential luminescence decays observed for Cu(4)2 [the
effect in Cu(5)2 is much less pronounced, see Table 3] seem
to be related to the cumbersome phenanthroline residues omitted for the sake of clarity (see Supporting Information).
298 K, λexc = 450 nm) and at 77 K rigid matrix (right; λexc
=
450 nm). The emission spectra of Cu(1)2 and Cu(2)2 have been
Eur. J. Inorg. Chem. 2010, 164–173
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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169

N. Armaroli, B. Delavaux-Nicot, J.-F. Nierengarten et al.
FULL PAPER
CH2O), 0.91 (s, 18 H, tBu), 0.10 (s, 12 H, Me) ppm. C26H40N2O2Si2
(468.79): calcd. C 66.62, H 8.60, N 5.98; found C 66.66, H 8.79, N
5.69.
der these conditions, is quite comparable for the whole
series. This strengthens the hypothesis that internal exciplex
quenching by oxygen is relevant for Cu(1)2–Cu(4)2 and pe-
culiarly abates the luminescence performance in fluid solu-
tion at room temperature. Notably, lifetimes in solid state
as powder are very short for Cu(1)2 and Cu(2)2 in line with
the behaviour in fluid solution at room temperature. Hence,
taken together, photophysical data in the solid state indicate
that low temperature is essential to limit parasite lumines-
cence quenching processes.
2,9-Bis[(triisopropylsilyloxy)methyl]-1,10-phenanthroline (2): A mix-
ture of TIPSCl (1.1 mL, 5.19 mmol), imidazole (380 mg,
5.56 mmol) and 6 (500 mg, 2.08 mmol) in DMF (20 mL) was
stirred at 0 °C for 24 h and the solvents evaporated. The residue
was taken up with CH2Cl2, washed with brine, dried (MgSO4), fil-
tered and the solvents evaporated. Column chromatography (SiO2,
CH2Cl2/0.5% MeOH) yielded 2 (836 mg, 73%). Colourless glassy
product. 1H NMR (CDCl3, 300 MHz): δ = 8.28 (d, J = 8 Hz, 2 H,
H4–7), 8.02 (d, J = 8 Hz, 2 H, H3–8), 7.75 (s, 2 H, H5–6), 5.36 (s, 4
H, CH2O), 1.14 (s, 42 H, iPr) ppm. C32H52N2O2Si2 (552.95): calcd.
C 69.51, H 9.48, N 5.07; found C 69.19, H 9.71, N 4.88.
Conclusions
The ground state electronic absorption spectra of
2,9-Bis[(tert-butyldiphenylsilyloxy)methyl]-1,10-phenanthroline (3):
Cu(1)2–Cu(5)2 show the typical MLCT pattern in the Vis A mixture of TBDPSCl (1.1 mL, 4.22 mmol), imidazole (290 mg,
4.22 mmol) and 6 (406 mg, 1.69 mmol) in DMF (20 mL) was
stirred at 0 °C for 48 h and the solvents evaporated. The residue
was taken up with CH2Cl2, washed with brine, dried (MgSO4), fil-
tered and the solvents evaporated. Column chromatography (SiO2,
CH2Cl2/0.5% MeOH) yielded 3 (1.02 g, 84%). Colourless glassy
product. 1H NMR (CDCl3, 300 MHz): δ = 8.24 (d, J = 8 Hz, 2 H,
H4–7), 8.05 (d, J = 8 Hz, 2 H, H3–8), 7.70 (s, 2 H, H5–6), 7.58 (m, 8
H, Ph), 7.35 (m, 12 H, Ph), 5.28 (s, 4 H, CH2O), 1.02 (s, 18 H,
tBu) ppm. C46H48N2O2Si2 (717.07): calcd. C 77.05, H 6.75, N 3.91;
found C 77.00, H 6.86, N 3.82.
spectra region. Their shape and intensity is in line with the
behaviour of [Cu(NN)2]+ with 2,9-dialkylphenanthroline li-
gands. All the compounds exhibit MLCT luminescence cen-
tered around 630–650 nm, but emission quantum yields and
lifetimes are dramatically different along the series. Cu(1)2–
Cu(3)2 exhibit vanishingly weak emission features even in a
solvent of low nucleophilicity such as toluene (Φ Ͻ
1ϫ10–5, τ in the range 2.4–6.0 ns). Cu(4)2 is a substantially
better luminophore (Φ = 2.5ϫ10–4, τ = 95.3 ns in oxygen-
free solution), but the best performer is Cu(5)2 which exhib-
its one of the longest MLCT lifetimes detected so far for
conventional CuI-bisphenanthroline complexes (420 ns).
The poor luminescence behaviour of Cu(1)2–Cu(4)2 com-
pared to Cu(5)2 in solution is attributed to a combination
of factors, i.e. internal exciplex quenching by oxygen atoms
on the phenanthroline residues and a more pronounced ten-
dency to undergo flattening distortion upon light exci-
tation, thanks to smaller steric hindrance.
2,9-Bis[2,6-bis(benzyloxy)phenethyl]-1,10-phenanthroline (4):
A
1.6  nBuLi solution (8.8 mL, 14.1 mmol) was added by syringe at
room temperature to an argon-flushed, stirred solution of diisopro-
pylamine (2.2 mL, 16.0 mmol) and tBuOK (1.68 g, 15.0 mmol) in
dry THF (60 mL) at –78 °C under Ar. After 1 h, the resulting solu-
tion was added slowly by means of a double-ended needle to a
solution of 7 (1.04 g, 5.0 mmol) in dry THF (80 mL) at –78 °C.
After 1 h, a solution of 2,6-dibenzyloxybenzyl bromide (1.98 g,
14.0 mmol) in THF (25 mL) was added dropwise. The resulting
mixture was stirred 2 h at –78 °C, then 12 h at room temperature.
The solution was then poured into ice water (150 mL). The mixture
was extracted with CH2Cl2 (3ϫ100 mL) and the combined organic
layers dried (MgSO4), filtered and the solvents evaporated. Column
chromatography (SiO2, CH2Cl2) yielded 4 (1.98 g, 49%). Colourless
glassy product. 1H NMR (CDCl3, 300 MHz): δ = 7.86 (d, J = 8 Hz,
2 H, H4–7), 7.54 (s, 2 H, H5–6), 7.12–7.02 (m, 24 H, H3–8 and Ph),
7.00 (t, J = 7 Hz, 2 H, Ar-H4), 6.51 (d, J = 7 Hz, 4 H, Ar-H3–5),
4.97 (s, 8 H, OCH2), 3.40 (m, 4 H, CH2), 3.29 (m, 4 H, CH2) ppm.
C56H48N2O4 (813.01): calcd. C 82.73, H 5.95, N 3.45; found C
82.44, H 6.13, N 3.12.
Experimental Section
General: Reagents and solvents were purchased as reagent grade
and used without further purification. Compound 6,[31] and 2,6-
dibenzyloxybenzyl bromide[43] were prepared according to the lit-
erature. THF was distilled from sodium benzophenone ketyl. All
reactions were performed in standard glassware under an inert Ar
atmosphere. Evaporation and concentration were done at water as-
pirator pressure and drying in vacuo at 10–2 Torr. Column
chromatography: silica gel 60 (230–400 mesh, 0.040–0.063 mm) was
purchased from E. Merck. Thin Layer Chromatography (TLC) was
performed on glass sheets coated with silica gel 60 F254 purchased
from E. Merck, visualization by UV light. NMR spectra were re-
corded on a Bruker AC 300 with solvent peaks as reference. Ele-
mental analyses were performed by the analytical service at the
Institut Charles Sadron, Strasbourg.
2-(1,3-Diphenylpropan-2-yl)-9-phenethyl-1,10-phenanthroline (5): A
1.6  nBuLi solution (8.8 mL, 14.1 mmol) was added by syringe at
room temperature to an argon-flushed, stirred solution of diisopro-
pylamine (2.2 mL, 16.0 mmol) and tBuOK (1.68 g, 15.0 mmol) in
dry THF (60 mL) at –78 °C under Ar. After 1 h, the resulting solu-
tion was added slowly by means of a double-ended needle to a
solution of 7 (1.04 g, 5.0 mmol) in dry THF (80 mL) at –78 °C.
After 1 h, a solution of benzyl bromide (2.40 mL, 20.0 mmol) in
THF (25 mL) was added dropwise. The resulting mixture was
stirred 2 h at –78 °C, then 12 h at room temperature. The solution
was then poured into ice water (150 mL). The mixture was ex-
tracted with CH2Cl2 (3ϫ100 mL) and the combined organic layers
dried (MgSO4), filtered and the solvents evaporated. Column
chromatography (SiO2, CH2Cl2) yielded 5 (1.06 g, 44%). Colourless
glassy product. 1H NMR (CD2Cl2, 300 MHz): δ = 8.12 (d, J =
2,9-Bis[(tert-butyldimethylsilyloxy)methyl]-1,10-phenanthroline (1):
A mixture of TBDMSCl (660 mg, 4.38 mmol), imidazole (380 mg,
5.56 mmol) and 6 (500 mg, 2.08 mmol) in DMF (20 mL) was
stirred at 0 °C for 4 h and the solvents evaporated. The residue was
taken up with CH2Cl2, washed with brine, dried (MgSO4), filtered
and the solvents evaporated. Column chromatography (SiO2,
CH2Cl2/1% MeOH) yielded 1 (780 mg, 80%). Colourless glassy
product. 1H NMR (CDCl3, 300 MHz): δ = 8.16 (d, J = 7 Hz, 2 H,
H4–7), 7.85 (d, J = 7 Hz, 2 H, H3–8), 7.64 (s, 2 H, H5–6), 5.19 (s, 4 H, 8 Hz, 1 H, H4), 7.97 (d, J = 8 Hz, 1 H, H7), 7.68 (AB, J = 8 Hz, 2
170 Eur. J. Inorg. Chem. 2010, 164–173
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Synthesis and Photophysical Properties of Copper(I) Complexes
H, H5–6), 7.47 (d, J = 8 Hz, 1 H, H3), 7.44 (d, J = 8 Hz, 1 H, H8),
7.20 (m, 15 H, Ph), 3.88 (m, 1 H, phen-CH), 3.50 (m, 6 H,
3ϫCH2), 3.25 (m, 2 H, CH2) ppm. C35H30N2 (478.64): calcd. C
87.83, H 6.32, N 5.85; found C 87.60, H 6.60, N 5.80.
General Procedure for the Preparation of the CuI Complexes: A solu-
tion of Cu(CH3CN)4·BF4 (1 equiv.) in CH3CN was added under
an argon atmosphere at room temperature to a stirred, degassed
solution of the appropriate ligand (2 equiv.) in CH2Cl2. The solu-
tion turned orange-red instantaneously, indicating the formation of
the complex. After 1 h, the solvents were evaporated. The resulting
complexes were purified by recrystallization from CH2Cl2/Et2O.
The CuI complexes were thus obtained as their BF4 salts in 50–
76% yields.
solutions used during the electrochemical studies were typically
10–3  in compound and 0.1  in supporting electrolyte. Before
each measurement, the solutions were degassed by bubbling Ar and
the working electrode was polished with a polishing machine (Presi
P230). Under these experimental conditions, Fc+/Fc is observed at
+0.54Ϯ0.01 V vs. SCE.
Spectroscopic Measurements: Absorption spectra were recorded
with a Perkin–Elmer λ9 spectrophotometer. For luminescence ex-
periments, the samples were placed in fluorimetric 1-cm path cu-
vettes and, when necessary, purged from oxygen by bubbling with
argon. Uncorrected emission spectra were obtained with an Edin-
burgh FLS920 spectrometer equipped with a peltier-cooled Hama-
matsu R928 photomultiplayer tube (185–850 nm). An Edinburgh
Xe900 450 W Xenon arc lamp was used as exciting light source.
Corrected spectra were obtained via a calibration curve supplied
with the instrument. Luminescence quantum yields (Φem) in solu-
tion obtained from spectra on a wavelength scale [nm] were mea-
sured according to the approach described by Demas and
Crosby[44] using air-equilibrated [Ru(bpy)3Cl2 in water solution,
Φem = 0.028][45] as standard. Emission lifetimes were determined
with the single photon counting technique by means of the same
Edinburgh FLS920 spectrometer using a laser diode as excitation
source (1 MHz, λexc = 407 nm, 200 ps time resolution after decon-
volution) and the above-mentioned PMTs as detectors. Or, with an
IBH single-photon counting spectrometer equipped with a thyra-
tron-gated nitrogen lamp working in the range 2–40 kHz (0.5 ns
time resolution); the detector was a red-sensitive (185–850 nm)
Hamamatsu R-3237–01 photomultiplier tube. To record the 77 K
luminescence spectra, the samples were put in glass tubes (2 mm
diameter) and inserted in a special quartz dewar, filled up with
liquid nitrogen. Experimental uncertainties are estimated to be
Ϯ8% for lifetime determinations, Ϯ20% for emission quantum
yields, Ϯ2 nm and Ϯ5 nm for absorption and emission peaks
respectively.
1
Cu(1)2: H NMR (CDCl3, 300 MHz): δ = 8.73 (d, J = 8 Hz, 4 H,
H4–7), 8.20 (s, 4 H, H5–6), 8.11 (d, J = 8 Hz, 4 H, H3–8), 4.47 (s, 8
H, CH2O), 0.59 (s, 36 H, tBu), –0.37 (s, 24 H, Me) ppm. 13C NMR
(CDCl3, 75 MHz): δ = 160.1, 142.4, 138.5, 128.9, 127.0, 122.6, 66.2,
25.4, 18.5, –6.0 ppm. C52H80BCuF4N4O4Si4 (1087.92): calcd. C
57.41, H 7.41, N 5.15; found C 57.55, H 7.44, N 5.34.
1
Cu(2)2: H NMR (CDCl3, 300 MHz): δ = 8.71 (d, J = 8 Hz, 4 H,
H4–7), 8.22 (s, 4 H, H5–6), 8.12 (d, J = 8 Hz, 4 H, H3–8), 4.51 (s, 8
H, CH2O), 0.60 (s, 84 H, iPr) ppm. 13C NMR (CDCl3, 75 MHz):
δ = 160.2, 142.3, 138.4, 128.9, 126.9, 122.3, 66.7, 17.4, 11.6 ppm.
C64H104BCuF4N4O4Si4 (1256.25): calcd. C 61.19, H 8.34, N 4.46;
found C 61.43, H 8.51, N 4.32.
1
Cu(3)2: H NMR (CDCl3, 300 MHz): δ = 8.55 (d, J = 8 Hz, 4 H,
H4–7), 8.01 (s, 4 H, H5–6), 7.96 (d, J = 8 Hz, 4 H, H3–8), 7.19 (t, J
= 7 Hz, 8 H, Ph), 7.02 (m, 16 H, Ph), 6.94 (m, 16 H, Ph), 4.01 (s,
8 H, CH2O), 0.82 (s, 36 H, tBu) ppm. 13C NMR (CDCl3, 75 MHz):
δ = 158.9, 141.7, 137.9, 134.7, 131.6, 131.1, 129.9, 128.3, 127.5,
127.1, 126.7, 121.9, 66.3, 26.5, 18.9 ppm. C92H96BCuF4N4O4Si4
(1584.49): calcd. C 69.74, H 6.11, N 3.54; found C 69.69, H 6.25,
N 3.33.
1
X-ray Crystal Structure of Cu(1)2: The orange crystal used for the
diffraction study (0.15ϫ0.10ϫ0.05 mm) was produced by slow dif-
fusion of Et2O into a CH2Cl2 solution of Cu(5)2. Single crystals of
complex Cu(1)2 was mounted on a Nonius Kappa-CCD area detec-
tor diffractometer (λMo-Kα = 0.71073 Å). The structure was solved
by direct methods (SHELXS97)[46] and refined against F2 using the
SHELXL97 software (Table 4).[47] The absorption was non-cor-
rected. Excepted for the F atoms of the BF4 counter anion, all non-
hydrogen atoms were refined anisotropically. Hydrogen atoms were
generated according to stereo-chemistry and refined using a riding
model in SHELXL97.
Cu(4)2: H NMR (CDCl3, 300 MHz): δ = 7.84 (d, J = 8 Hz, 4 H,
H4–7), 7.68 (s, 4 H, H5–6), 7.10 (m, 28 H, H3–8 and Ph), 6.80 (m,
20 H, Ph and Ar-H4), 6.15 (d, J = 7 Hz, 8 H), 2.84 (m, 8 H, CH2),
2.71 (m, 8 H, CH2) ppm. 13C NMR (CDCl3, 75 MHz): δ = 161.6,
156.8, 142.8, 136.9, 136.2, 128.3, 127.4, 126.4, 125.8, 116.9, 104.9,
69.5, 39.2, 22.6 ppm. C112H96BCuF4N4O8·H2O (1794.38): calcd. C
74.97, H 5.50, N 3.12; found C 74.76, H 5.47, N 3.12.
1
Cu(5)2: H NMR (CDCl3, 300 MHz): δ = 8.68 (d, J = 8 Hz, 2 H,
H4), 8.63 (d, J = 8 Hz, 2 H, H7), 8.02 (s, 4 H, H5–6), 7.80 (d, J =
8 Hz, 2 H, H3), 7.70 (d, J = 8 Hz, 2 H, H8), 6.80 (m, 14 H, Ph),
6.68 (m, 4 H, Ph), 6.22 (m, 4 H, Ph), 6.13 (m, 4 H, Ph), 6.04 (m,
4 H, Ph), 3.50 (m, 2 H, phen-CH), 2.71 (m, 4 H, 2ϫCH2), 2.50
(m, 8 H, 4ϫCH2) ppm. 13C NMR (CDCl3, 75 MHz): δ = 163.5,
160.6, 143.4, 143.1, 139.2, 137.9, 137.8, 137.75, 128.7, 128.5, 128.3,
128.1, 127.9, 127.1, 126.9, 126.7, 126.3, 125.0, 123.9, 52.3, 41.1,
39.9, 38.5, 34.5 ppm. C70H60BCuF4N4 (1107.62): calcd. C 75.91, H
5.46, N 5.06; found C 75.81, H 5.51, N 5.02.
X-ray Crystal Structure of Cu(5)2: The red crystal used for the dif-
fraction study (0.20ϫ0.25ϫ0.35 mm) was produced by slow dif-
fusion of Et2O into a CH2Cl2 solution of Cu(5)2. Data were col-
lected at low temperature on an Oxford-Diffraction XCALIBUR
CCD diffractometer using a graphite-monochromated Mo-Kα radi-
ation (λ = 0.71073 Å) and equipped with an Oxford Cryosystems
Cryostream Cooler Device. The structure was solved by direct
methods using SIR92,[48] and refined by means of least-squares
procedures on F using the programs of the PC version of CRYS-
TALS (Table 4).[49] Atomic scattering factors were taken from the
International tables for X-ray Crystallography.[50] All non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were refined
using a riding model.
Electrochemistry: The cyclic voltammetric measurements were car-
ried out with a potentiostat Autolab PGSTAT100. Experiments
were performed at room temperature in a homemade airtight
three–electrode cell connected to a vacuum/argon line. The refer-
ence electrode consisted of a saturated calomel electrode (SCE) sep-
arated from the solution by a bridge compartment. The counter
electrode was a platinum wire of ca 1 cm2 apparent surface. The
working electrode was a Pt microdisk (0.5 mm diameter). The sup-
porting electrolyte [nBu4N][BF4] (Fluka, 99% electrochemical
grade) was used as received and simply degassed under argon.
Dichloromethane was freshly distilled from CaH2 prior to use. The
CCDC-739310 [for Cu(1)2] and -737783 [for Cu(5)2] contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Eur. J. Inorg. Chem. 2010, 164–173
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
171

N. Armaroli, B. Delavaux-Nicot, J.-F. Nierengarten et al.
FULL PAPER
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Table 4. Crystallographic and structure refinement data for com-
pounds Cu(1)2 and Cu(5)2.
Cu(1)2
Cu(5)2
Chemical formula
Formula weight
Crystal system
Space group
a [Å]
b [Å]
c [Å]
C52H80BCuF4N4O4Si4·Et2OC70H60BCuF4N4
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1162.03
monoclinic
P21/n
1107.62
orthorhombic
Pna21
23.1526(6)
11.7421(3)
20.9595(5)
90
2185–2193.
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11.6980(10)
32.578(5)
17.806(2)
90
α [°]
β [°]
107.86(5)
90
6458.8(13)
4
90
90
5698.1(2)
4
[20] M. T. Miller, P. K. Gantzel, T. B. Karpishin, J. Am. Chem. Soc.
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γ [°]
V [Å3]
[21] B. A. Gandhi, O. Green, J. N. Burstyn, Inorg. Chem. 2007, 46,
Z
3816–3825.
Density
1.195
0.469
2480
1.291
0.443
2312
µ (Mo-Kα) [mm–1]
F (000)
[22] O. Green, B. A. Gandhi, J. N. Burstyn, Inorg. Chem. 2009, 48,
5704–5714.
[23] R. M. Everly, D. R. McMillin, Photochem. Photobiol. 1989, 50,
T [K]
Reflections collected
Independent reflections 18686
Reflections used in the
173
18686
160
52557
14050
711–716.
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2003, 125, 7022–7034.
calculation
Parameters
8645 [I Ͼ 2σ]
673
4878 [I Ͼ 3σ]
466
Goodness-of-fit on F
R
wR
1.154
0.0920
0.2403
1.0773
0.0733
0.0857
Supporting Information (see also the footnote on the first page of
this article): Emission spectra of Cu(1)2, Cu(2)2 and Cu(3)2 in tolu-
ene.
[30] D. G. Cuttell, S. M. Kuang, P. E. Fanwick, D. R. McMillin,
R. A. Walton, J. Am. Chem. Soc. 2002, 124, 6–7; L. Yang, J. K.
Feng, A. M. Ren, M. Zhang, Y. G. Ma, X. D. Liu, Eur. J. Inorg.
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Acknowledgments
This work was supported by the Italian National Research Council
(PM.P04.010, MACOL), the Centre National de la Recherche Sci-
entifique (CNRS) (UMR 7509, UPR 8241) and the European
Commision (OLLA IST-2002-004607, ITN FINELUMEN, PITN-
GA-2008-215399). We thank Mr. Roberto Cortesi for technical as-
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