Ullmann reaction through ecocatalysis: Insights from bioresource and synthetic potential

Article abstract of DOI:10.1039/c6ra08664k

We report the elaboration of novel bio-sourced ecocatalysts for the Ullmann coupling reaction. Ecocatalysis is based on the recycling of metals issued from phytoremediation or rehabilitation, and an innovative chemical valorization of the subsequent biomass in the field of catalysis. Here, we describe efficient copper accumulation by plants via phytoextraction and rhizofiltration. These phytotechnologies were revisited to demonstrate a novel potential of these natural resources for green chemistry. Taking advantage of the remarkable ability of the selected plants to accumulate Cu(ii) species into their roots or leaves, the latter can be directly used for the preparation of ecocatalysts, called Eco-Cu. The formed Eco-Cu catalysts are thoroughly characterized via ICP-MS, IR studies of pyridine sorption/desorption, TEM, XRD, SM and model reactions, in order to elucidate the chemical composition and catalytic activity of these new materials. Significant differences of properties and activities were observed between Eco-Cu and conventional Cu catalysts. Eco-Cu are highly active catalysts in Ullmann coupling reactions with lower Cu quantities compared to known copper catalysts.

Full text of DOI:10.1039/c6ra08664k

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Ullmann reaction through ecocatalysis: insights from
bioresource and synthetic potential
Guillaume Clavé1, Claire Garel1, Cyril Poullain1, BriceꢀLoïc Renard1, Tomasz K. Olszewski2, Bastien
Lange3,4, Mylor Shutcha5, MichelꢀPierre Faucon3, Claude Grison*1
1Bioꢀinspired Chemistry and Ecological Innovations (ChimEco), FRE 3673 CNRSꢀUniversity of
Montpellier, Cap Delta, 1682 rue de la Valsière, 34790 Grabels, France
2 Faculty of Chemistry, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50ꢀ370
Wroclaw, Poland
3Hydrogéochimie et Interactions SolꢀEnvironnement (HydrISE), UP.2012.10.102, Institut
Polytechnique LaSalle Beauvais (ISABꢀIGAL), 19 rue Pierre Waguet, FRꢀ60026 Beauvais, France
4Laboratoire d’Ecologie végétale et Biogéochimie, Université Libre de Bruxelles, 50 Avenue F.
Roosevelt, BEꢀ1150 Brussels, Belgium
5Ecology, Restoration Ecology and Landscape research Unit, Faculty of Agronomy, University of
Lubumbashi, 1825 route Kasapa, Campus universitaire, Lubumbashi, Democratic Republic of Congo
* Claude Grison; EꢀMail: claude.grison@cnrs.fr
Tel.: +33ꢀ786ꢀ854ꢀ454
Abstract: We report the elaboration of novel bioꢀsourced ecocatalysts for Ullmann coupling reaction.
Ecocatalysis is based on the recycling of metals issued from phytoremediation or rehabilitation, and an
innovative chemical valorization of the subsequent biomass in the field of catalysis. Here, we describe
the efficient copper accumulation by plants via phytoextraction and rhizofiltration. These
phytotechnologies were revisited to demonstrate a novel potential of these natural resources for the
Green Chemistry. Taking advantage of the remarkable ability of the selected plants to accumulate
Cu(II) species into their roots or leaves, these latter can be directly used for the preparation of
ecocatalysts, called EcoꢀCu®. The formed EcoꢀCu® catalysts are thoroughly characterized via ICPꢀMS,
IR study of pyridine sorption/desorption, TEM, XRD, SM and model reactions, in order to elucidate
the chemical composition and catalytic activity of these new materials. Significant differences of
properties and activities were observed between EcoꢀCu® and conventional Cu catalysts. EcoꢀCu®
appear as highly active catalysts in Ullmann coupling reactions with lower Cu quantity compared to
known copper catalysts.
Keywords: phytoextraction; Congolese mining sites; rhizofiltration; contaminated
effluents; ecological recycling; ecocatalysis; copper catalysis; Ullmann coupling
1. Introduction
Intensive mining and industrial metallurgic activities are responsible for the pollution of soils and
aquatic systems with metal trace elements (TEs). This is incredibly worrying, since the soil plays an
essential role largely determining food production and water quality. Moreover, TEs are some of the

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most harmful pollutants. They are not biodegradable and persist in organisms and contaminated
ecosystems.
For instance, the devastating effects of mining in the southern province of the Democratic Republic of
the Congo characterize one of the critical patterns implicated in global environmental change. In
Katanga, the negative consequences of mining operations for the local population are clear: largeꢀscale
destruction of natural ecosystems and arable soils, severe impacts on hydrological processes, increased
sediment pollution in rivers and the groundwater table, reduction of biodiversity, soil erosion, and
release of Cu and Co, which leads to contamination of soils, surface and ground water. Animals are
contaminated upon contact, through the inhalation of metal dust, ingestion of contaminated water and
food. Metal pollutants travel through the food chain, and thus they have also a significant impact on
human health.
Phytoremediation is used to solve environmental problems caused by TEs. Given their phytotoxicity,
metalliferous soils are under high selection pressure and generate particular habitats for plant species
and their associated microorganisms. This results in a unique biological resource, metallophytes. These
plants are defined as being capable of tolerating high concentrations of TEs, surviving and reproducing
on such sites1. Phytoextraction is one of the few interesting solutions for sustainable phytoremediation
of soils degraded or contaminated by TEs. It is defined as the partial rehabilitation of soils through the
accumulation of TEs in aerial parts of hyperaccumulator plants (e.g. A. murale2, A. vulneraria3, G.
exul4). Rhizofiltration is equivalent to phytoextraction process, but it takes place in an aqueous
medium instead of the rhizosphere5.
However, the development of phytoextraction and rhizofiltration is still restricted because
contaminated biomass is not recovered: the aerial parts of hyperaccumulator plants, or roots of plants
derived from rhizofiltration are considered as contaminated waste. Moreover, the extraction of TEs by
the root system increases the fraction of soluble elements. The sustainability of phytoextraction and
rhizofiltration is entirely related to the recycling of the generated biomass.
Our group has recently proposed a unique use and valorization of phytoextraction and rhizofiltration:
ecocatalysis6ꢀ8. Plant waste produced is recovered using an innovative concept of ecological recycling.
Taking advantage of the remarkable adaptive capacity of some plants to hyperaccumulate metals,
ecocatalysis is based on an original use of metal species of plant origin as reactants and catalysts in
fine organic chemical reactions. This allows the preparation of biomolecules using an ecoꢀresponsible
and bioꢀinspired approach. The obtained results demonstrate that these new catalytic systems present
unique chemical reactivity. Ecocatalysts constitute an entire new generation of Lewis acid catalysts9ꢀ15
,
very efficient green oxidative16, reductive17, and sustainable coupling agents in organic synthesis18.
They can be used as alternative reagents in place of those prohibited by the European legislation
REACH. Finally, we could use these reagents to develop innovative bioꢀinspired syntheses capable of
reducing the environmental impact of implemented procedures.
Ecocatalysis created a change in the paradigm: biomass from phytoextraction and rhizofiltration is no
longer considered as contaminated waste, but as a natural restoration system with high added value.
This biomass is a natural reservoir of transition metals, precious in organic synthesis. In other words,
wastes have become useful and innovative chemical tools.
This article aims at describing new results in the field of phytoremediation of systems contaminated by
copper from anthropogenic activities, and to study the recovery of the derived biomass through the

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concept of ecocatalysis. Comparatively, the copper phytoextraction is studied on mining sites in
Katanga, while copper rhizofiltration is carried out with contaminated copper solutions. Results clearly
allow the preparation, characterization and study of the reactivity of these first EcoꢀCu® catalysts in Nꢀ
and Oꢀarylation coupling reactions.
2. Results and Discussion
2.1.1. Phytoextraction:
TEs contaminants occurrence and impact on humans and other organisms have already been reported
in Katanga (Democratic Republic of the Congo)19. Tropical soils contaminated by metal smelters and
mining represent a secondary source of contamination with major environmental issue related to low
pH20 of Ferralsol increasing TEs mobility, intense erosion by rainfall in the rainy season, and aerial
dispersal of metal particles by wind in the dry season. Reduction of environmental risks and TEs
dispersion can be performed by phytoremediation, using TEs tolerant and hyperaccumulator plants
from the plant biodiversity of natural habitats enriched in Cu21ꢀ23. This study is the first investigation
on the phytoextraction of soils contaminated by copper smelters and mining associated to the
preparation of Cu ecocatalysts.
Copper concentrations in plant shoots of Anisopappus chinensis
Mean of Cu concentration in A. chinensis plant shoots (FCu) was 230 µg gꢀ1dry weight (DW) (range:
45‒504 µg gꢀ1DW). The high variation of Cu accumulation observed in A. chinensisis in accordance
with previous studies22ꢀ24. As already highlighted for other Cuꢀaccumulating species, such variations
can be genetic, especially due to genetic differentiation within and between populations25, 26. Better
understanding of such accumulation variations requires an accurate characterization of the soilꢀroot
interface properties and mechanisms controlling Cu mobility and availability24, 27. Soil parameters like
pH, redox potential, organic matter quality and quantity, oxides, clays, sulphides and carbonates are
known to be essential factors controlling TEs mobility in soils28. In Congolese metalliferous soils, Cu
is known to be mostly adsorbed by organic matter and iron oxide species20, 24
.
Evaluation of phytoextraction parameters for one year of plant growth
Mean of shoot biomass of individuals of A. chinensis (n = 20) was 1.18 g (range: 0.14‒3.79 g).
Biomass productivity (Ybio) was estimated to 17.7 g/m2/year whether 177 kg/ha/year (range: 20‒568
kg/ha/year). Mean Cu content in A. chinensis plant shoots was 287 µg of Cu per plant from the DW
(range: 29‒1781 µg plantꢀ1). A comparable amount of Cu per plant can be phytoextracted using the Cuꢀ
tolerant species Elsholtzia splendens29, 30
.
Total Cu phytoextracted (YCu = FCu.Ybio) /ha/year on contaminated soil using plants of A. chinensis
from “Mine de l’Etoile” could reach 286 g/ha/year. A much more higher yield of phytoextracted Cu
can be obtained with E. splendens (1.7 kg Cu haꢀ1) 29, 30, but compared to some crop species, such a
yield of phytoextraction could be about five times higher (e.g. sunflower with 59 g Cu ha−1)31. A.
chinensis appears to be a good candidate for Cu phytoextraction. However, due to the great variability
of its ability to extract Cu from the soil, phytoextraction using A. Chinensis should be improved by

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plant selection and genotyping. Indeed, an individual from another natural population could
accumulate Cu up to 1 335 µg gꢀ1 DW for 5.1 g:6.7g plantꢀ1, i.e. a yield almost quadrupled (1
kg/ha/year)24. Potentially, Cu phytoextraction might be improved by performing a multispecies system
introducing other Cu tolerant and accumulator species. Such an innovative system on Cu contaminated
soils could lead to an increased phytoextraction yield as some species are known to accumulate Cu in
their shoots more effectively than A. chinensis (e.g. Haumaniastrum robertii)32.
This first evaluation on phytoextraction of soils contaminated by Cu in Tropical Africa has shown a
medium yield of Cu phytoextracted. Perspectives would be to test it at field scale with a multiꢀspecies
system, introducing functional diversity of Cuꢀtolerant plants (species and populations).
2.1.2.Rhizofiltration
Choice of the plants
Three plants have been studied to test their ability to accumulate copper into their roots from aqueous
medium. Bacopa monnieri was already known to well accumulate copper into its roots5, 33. Lolium
multiflorum was known to accumulate other metallic elements than copper, such as palladium, and its
main asset relies on its wellꢀdeveloped root biomass18, 34. Finally, Eichhornia crassipes was also
known to accumulate copper35, to multiply easily and also for its amazing root biomass, which of
course are assets to perform ecocatalysis.
Plant growth
Before studying the efficiency of these plants in rhizofiltration, it was interesting to have an insight of
the plant biomass growth, and of the biomass measuring (Table 1). The amount of root biomass is
important for the removal of copper from aqueous media, and also affects the quantity of ecocatalyst
(EcoꢀCu®) possibly formed.
B. monnieri and E. crassipes were directly bought in a garden center. L. multiflorum was grown in our
laboratory, and the germination percentage after 9 days was 82%.
Table 1. Biomass measuring (mg/plant) for Lolium multiflorum, Bacopa monnieri and Eichhornia
crassipes.
Root
Shoot
biomass
Growth
period
Species
Substrate for growth
biomass
(mg/plant)
(mg/plant)
Lolium
Fleximix Root Riot
8 weeks
6.8
54
20.2
multiflorum
Organic Starter Cubes
Natural substrate
Manado
Bacopa monnieri
5 months a
840.8

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Eichhornia
crassipes
/
5743
1629
aPeriod between the start of the cultivation on Manado substrate until the beginning of Cu accumulation
In terms of root biomass, E. crassipes gave better results than the other plants, which is an asset for
copper accumulation, and for ecocatalysts preparation. Moreover, this plant is easy to handle because it
can grow without any substrate thanks to its inflated petiole.
Plant analysis: determination of metal concentrations in roots and leaves
Copper concentrations in roots and leaves of the three plants were determined by an ICPꢀMS analysis.
The results are shown in table 2.
Table 2. Copper concentration in roots and leaves (wt% ± standard deviation), and BCF and TF
calculation.
Cu
concentration
in effluent
(mg/L)
Roots
BCF
Leaves
BCF
TF
(wt% ±SD)
(in roots)
(wt% ± SD)
(in leaves)
Plant
Bacopa
monnieria
1.34 ± 0.011
0.097 ± 0.0011
10.5
1279
666
92
0.072
0.0044
Lolium
multiflorumb
10.6
0.71 ± 0.0036
0.0031 ± 0.000007
2.9
0.082 ± 0.00073
0.19 ± 0.0014
(petiole)
78
0.032
0.074
Eichhornia
crassipesc
2.55 ± 0.027
10.5
2430
180.4
(petiole)
(petiole)
aDuring Cu accumulation the substrate used for growth was removed
bLolium multiflorum was still on Fleximix Root Riot Organic Starter Cubes during copper accumulation
cNo substrate used
Concentration of copper in root biomass is much higher in E. crassipes than in L. multiflorum and B.
monnieri. Besides, the translocation factors in the petiole and leaves of E. crassipes remain low, with
values between those obtained with L. multiflorum and B. monnieri. These results combined with
biomass measuring make E. crassipes a good candidate for rhizofiltration to produce ecocatalysts.
2.2.1. Preparation of the Eco-Cu® catalysts

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®
®
EcoꢀCu1ꢀ2 (A. chinensis), were prepared from harvested plants’ leaves and EcoꢀCu3ꢀ4 (B. monnieri),
EcoꢀCu5ꢀ6® (L. multiflorum) and EcoꢀCu7ꢀ8® (E. crassipes), were prepared from harvested plants’ roots
following the described procedure (see experimental part, section 3.4.). Each ecocatalyst must be
subjected to a heat treatment sufficient to destroy organic matter. EcoꢀCu2 , EcoꢀCu4®, EcoꢀCu6 and
EcoꢀCu8® were activated by chemical treatment with hydrochloric acid from EcoꢀCu1 , EcoꢀCu3 , Ecoꢀ
®
®
®
®
®
®
Cu5 and EcoꢀCu7 respectively. This step enables metal chlorides formation inside of the
ecocatalysts.
2.2.2. ICP-MS characterization of the Eco-Cu®
Table 3 shows mineral composition of the different EcoꢀCu® catalysts. It can be divided in two parts:
ecocatalysts derived from phytoextraction (EcoꢀCu1ꢀ2®) and those obtained from rhizofiltration (Ecoꢀ
Cu3ꢀ8®). Copper concentrations in EcoꢀCu® catalysts are quite different depending on the nature of the
plant, which is in agreement with phytoextraction and rhizofiltration studies reported in the previous
sections 2.1.1. and 2.1.2. It is clear that ecocatalysts derived from plants used in rhizofiltration are
more concentrated in Cu than ecocatalysts derived from plants used in phytoextraction. For instance,
®
copper concentrations in EcoꢀCu3ꢀ4 are 20 times higher than in EcoꢀCu1ꢀ2®, which confirms that B.
monnieri is a much better copper accumulator than A. chinensis. However, as reported previously (see
section 2.1.1. and 2.1.2.), the biomass of A. chinensis is more abundant than the biomass of B.
monnieri, which is an asset to produce ecocatalysts in larger quantities. E.crassipes is the best plant
tested for rhizofiltration, with a weight percentage of copper in its resulting ecocatalyst at least twice
higher than in the other ecocatalysts. Moreover, some significant differences between the compositions
of the catalysts are observed: A. chinensis catalysts are poor in sodium and rich in potassium whereas
these rates are reversed in case of B. monnieri. In the case of plants used in rhizofiltration, the main
difference, apart from the copper rate, is the calcium rate: L. multiflorum is richer in calcium than E.
crassipes.
Even if the two phytotechnologies, phytoextraction and rhizofiltration, gave different results in terms
of accumulation and biomass, they are complementary for the remediation of contaminated targets, soil
or water. This article is an opportunity to study the recovery of these different types of biomass
through the preparation and the activity of ecocatalysts.
Table 3. Mineral composition of EcoꢀCu® catalysts (wt% ± standard deviation) established by ICPꢀ
MS.
Ecocatalystst
Plant
Na
Mg
Al
K
Ca
Fe
Zn
Cu
0.11
7.85
1.01 23.29 8.44
0.92
0.08
®
0.38
EcoꢀCu1
±4.05 ±0.59 ±3.83 ±4.66 ±1.46 ±0.59 ±1.59 ±0.38
0.31 6.40 0.68 18.73 7.80 0.78 0.06
±1.55 ±0.64 ±0.77 ±0.60 ±0.91 ±0.80 ±0.48 ±0.97
Anisopappus chinensis
®
0.26
EcoꢀCu2

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9.60
±0.86 ±0.36 ±0.95 ±0.83 ±0.93 ±0.72 ±1.15 ±0.77
5.29 1.86 1.93 3.48 4.91 1.21 0.04
±0.18 ±0.53 ±1.14 ±0.29 ±0.77 ±0.34 ±0.77 ±0.45
0.78 0.60 0.00 1.11 34.61 0.04 0.09
±0.70 ±0.13 ±2.96 ±0.36 ±0.35 ±0.71 ±0.49 ±0.52
0.50 0.36 0.00 0.72 22.18 0.02 0.05
±0.69 ±1.48 ±6.00 ±0.71 ±0.59 ±1.86 ±0.72 ±1.05
1.26 0.43 0.13 0.38 0.97 1.85 0.06
±0.06 ±0.30 ±1.01 ±1.51 ±1.02 ±0.55 ±3.50 ±0.25
0.84 0.26 0.05 0.14 0.61 0.81 0.03
3.23
3.40
6.23
8.28
1.97
0.06
®
®
9.15
EcoꢀCu3
EcoꢀCu4
EcoꢀCu5
EcoꢀCu6
EcoꢀCu7
EcoꢀCu8
Bacopa monnieri
Lolium multiflorum
Eichhornia crassipes
4.75
®
®
3.29
2.02
®
®
18.15
10.37
±0.57 ±0.95 ±1.82 ±0.34 ±6.97 ±0.21 ±5.86 ±0.23
2.2.3. XPS Analysis
®
XPS analysis was performed on EcoꢀCu8 to study the oxidation state of copper after thermal
treatment and activation with HCl.
The strong peak at 202 ± 0.1 eV corresponding to chlorine 2p3/2 illustrates the formation of chloride
due to the aq. HCl activation of the material.
High resolution analysis of the copper element was carried out. The 2p3/2 Cu signal consists of a
combination of two components: 933 and 935 ± 0.1 eV. The more intense one is characterized by a
binding energy of 933 ± 0.1 eV, indicating the expected presence of Cu(II). The component at 935 ±
0.1 eV has a lower intensity (about 13% of the main peak) and may be assigned to Cu(I), in agreement
®
with the literature36. It is assumed that the observation of Cu (I) is not due to EcoꢀCu8 , because it is
well known that Cu(II) is easily reduced to Cu(I) when subjected to XPS analysis37. Finally, strong
2p3/2 satellite peaks of Cu(II) are present in the region of 940ꢀ950 ± 0.1 eV36.
Eco-Cu8
100,0k
Total spectrum
11k
10k
9k
Peak of Cu(II)
Peak of Cu(I)
Satellite peak of Cu(II)
Satellite peak of Cu(II)
Background
80,0k
60,0k
40,0k
20,0k
0,0
8k
7k
960
950
940
930
1200
1000
800
600
400
200
0
Binding energy / eV
Binding energy / eV
®
Figure 1. XPS analysis of EcoꢀCu8
The formation of Cu(II) is the consequence of an oxidative thermal treatment under air flow of plants'
roots. This hypothesis is reinforced by the reaction of EcoꢀCu8 with aqueous ammonia and the
formation of a deep blue [Cu(NH3)4]2+ complexes.

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i) 6M NH3/H20
ii) vortexing
EcoꢀCu8
®
Figure 2. Analytical characterization of EcoꢀCu8
In the aim to specify the nature of copper (II) chloride salts, mass spectrometry analysis were
performed by directꢀinjection mass spectrometric method.
2.2.5. Direct-injection mass spectrometric analysis
®
Structural information for EcoꢀCu8 was collected using mass spectrometry with electrospray
ionization operated in the negative ion mode. This MS method provided sufficient sensitivity and
selectivity for the rapid identification of an anionic inorganic species, but it led to the electrochemical
reduction of Cu(II) into Cu(I) according to Gianelli works38.
®
2ꢀ
ꢀ
With EcoꢀCu8 , two Cu chlorides species were detected: CuCl3 and CuCl2 . Taking into account the
copper oxidation state reduction of Cu by the ESI method, we can conclude that EcoꢀCu8® consists of a
mixture of CuCl42ꢀ and CuCl3ꢀ.This hypothesis is consistent with the XPS analysis.
2.2.6. XRD studies
®
XRD analyses of EcoꢀCu8 were performed in order to determine the crystalline structure of the
complexes in the catalyst (Figure 3). One polymetallic compound was detected: K6Fe2O5. Manganese
was present in the manganosite form MnO, in the presence of sodium chloride and calcium sulfate
hydrate. Copper was present in the amorphous form.
2200
2100
2000
1900
1800
1700
1600
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
10
20
30
40
50
60
70
80
90
2-Theta - Scale
CG151122-208 - File: CG151122-208.raw
01-083-2465 (C) - SiO2 - Quartz
Operations: Strip kAlpha2 0.500 | Background 1.000,1.000 | Import
01-076-2312 (C) - CaSO4(H2O).8 - Calcium Sulfate Hydrate
01-077-2064 (C) - NaCl - Sodium Chloride
00-048-0692 (I) - K6Fe2O5 - Potassium Iron Oxide
01-075-1090 (C) - MnO - Manganosite, syn
®
Figure 3. XRD analysis of EcoꢀCu8

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2.2.7 TEM studies
®
The morphology and structure of EcoꢀCu8 was further characterized using TEM. Figures 4a and 4b
shows the TEM images. The microstructure of the ecocatalyst is layered with dark shades and clear
areas, indicating a satisfactory uniformity in the composition of the ecocatalyst. TEM images of Ecoꢀ
Cu8® in figure 4b reveal Cu nanoparticles, which are embedded in the solid matrix. These nanoparticles
are not aggregated and are well dispersed at the surface of the matrix. The particle size has been
determined based on the average size of 40 particles. The particles show a relatively narrow size
distribution centered around 4ꢀ8 nm.
®
Figures 4a and4b. TEM images of EcoꢀCu8
2.2.8. Acidity characterization of the Eco-Cu® catalyst
®
We decided to study Lewis and Brønsted acid properties of our best ecocatalyst (EcoꢀCu8 , see 2.3
section) versus commercial copper chlorides. Lewis acidity is usually defined by its strength and its
hardness according to the HSAB principle, described by Pearson39, 40. Two conventional methods were
used: the first one is based on the infrared study of pyridine adsorption/desorption on the catalysts. The
second, introduced by Corma et al. consists in studying the rearrangement of a cyclic acetal. The first
method enables a comparison of the Lewis acid strength and Brønsted acidity between different
catalysts. The method implemented by Corma et al. enables also a comparison of the hardness of
Lewis acidity.
Pyridine is often used as a probe to evaluate Lewis and Brønsted acidity of solid acids41, 42 by
monitoring its infrared absorption bands between 1400 and 1660 cmꢀ1. Infrared spectra of pyridine
®
adsorbed on EcoꢀCu8 , on commercial anhydrous CuCl2, and on CuCl2.2H2O were recorded at 23°C
and at 150°C in order to distinguish physisorbed pyridine from pyridine coordinately bonded to Lewis
acid sites. The absorption bands around 1450 cmꢀ1 observed on the spectra are characteristic of
strongly bonded pyridine to Lewis acid sites41, 42 (Figure 5). Because the frequencies of these
absorption bands were similar in the three catalysts, we can conclude that the strength of the Lewis
®
acidity is not really different between EcoꢀCu8 , anhydrous CuCl2 and CuCl2.2H2O. Besides, two

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absorption bands, characteristic of pyridinium ion, were observed at 1530 and 1537 cmꢀ1 42 with Ecoꢀ
Cu8® only. Thus EcoꢀCu8® present a Brønsted acidity contrary to both commercial copper chlorides.
®
Figure 5. IR spectra of pyridine adsorbed on EcoꢀCu8 , on commercial anhydrous CuCl2 and
CuCl2.2H2O.
These first conclusions were completed and supported by another method, implemented and tested by
Corma et al.43, 44. This method consists in studying the rearrangement pathway of the cyclic acetal of
αꢀbromopropiophenone, in the presence of a catalyst. The selectivity of products formed during the
reaction provides informations to assess the hardness of the Lewis acid sites of the catalysts. It can also
highlight their Brønsted acid property. The selectivity results obtained are presented in Table 4. The
®
Brønsted acid pathway is slightly stronger in EcoꢀCu8 than in both commercial copper chlorides,
which supports the previous infrared study of adsorbed pyridine. According to conversion rates, Ecoꢀ
®
Cu8 is more active on cyclic acetal than both commercial copper chlorides, which might result from
its stronger Brønsted acid character. Finally, the product from the soft Lewis acid pathway is only
®
formed with commercial copper chlorides but not with EcoꢀCu8 . Therefore, the Lewis acidity of Ecoꢀ
®
Cu8 is harder than the Lewis acidity of commercial copper chlorides, which might be due to the
presence of other elements known to be hard Lewis acids45, such as iron or calcium as shown by the
ICPꢀMS analysis (Table 3).
Table 4. Conversion rates and selectivities of products coming from the rearrangement of cyclic acetal
of αꢀbromopropiophenone with EcoꢀCu8® and commercial anhydrous CuCl2 and CuCl2.2H2O.

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Conversion
ratea [%]
Catalysts
Selectivitya [%]
(R=H, Br, Cl)
(X=H, Br, Cl)
Brønsted acidity
products
Hard Lewis acidity
products
Soft Lewis
acidity product
®
EcoꢀCu8
100
49
64
52
39
36
41
58
0
7
3
Anhydrous CuCl2
CuCl2.2H2O
65
a Determined by GCꢀMS analysis
2.3. Reactivity of Eco-Cu® in Ullmann coupling reaction
Copper was the first metal used in crossꢀcoupling reactions46, 47 decades before palladiumꢀ and nickelꢀ
catalyzed procedures had emerged. Copper has the advantage of being inexpensive, earthꢀabundant,
nonꢀtoxic and then found in widespread applications in homogeneous chemical catalysis. Indeed for
more than a century, copper is an effective catalyst for the useful and practical formation of C(aryl)ꢀN,
C(aryl)ꢀC, and C(aryl)ꢀO bonds48ꢀ50. Such copperꢀmediated coupling reactions have numerous
industrial applications, including the synthesis of intermediates as well as synthetic targets for the life
sciences, agrochemical and polymer industries51, 52. However, Ullmannꢀtype coupling reactions have
been neglected for a long time because of their drawbacks: harsh reaction conditions often used,
limited range of suitable substrates and moderate yields obtained. These condensations are usually
conducted in aprotic polar solvents such as Nꢀmethylpyrrolidone or N,NꢀDimethylformamide at high
temperature, with copper reagent rarely used in catalytic quantities. Therefore important efforts are
provided among the community of organic chemists to discover new milder, inexpensive and
environmentally benign reaction conditions. Recently, several research groups obtained interesting
results in producing inexpensive copper catalysts complexed with simple ligands53, able to perform
economical and efficient Nꢀarylation of nitrogenꢀcontaining heterocycles with aryl halides. These
ligands derived from phosphines54, amino acids55,
β
ꢀdiketones56 or 1,2ꢀdiamines57, 58. They are
important to improve both the catalyst concentration and its electronic density. With these ligands, the
coupling reactions are more efficient, but this implies increasing cost, bad ecological footprint and
contamination of the final product. The past few years, to circumvent those inconveniences, ligandꢀ

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free Ullmann coupling have been performed using CuI and Cu2O as catalysts with good results. Indeed
Ullmannꢀtype coupling reaction can be catalyzed by all copper species from Cu(I) to Cu(II) and even
by metal copper since the original work of Ullmann and Goldberg46, 47, 59, 60. In 1928, Weston et al.
published results concerning the Ullmann reaction comparing a wide range of catalyst sources, leading
them to say that: “almost any copper or copper compound may be used as a source of catalyst”,
although Cu(I) salts appeared to give better results. In fact, it has been demonstrated later by analytical
meanings that the active species is the cuprous salt (Cu+) which if not directly introduced, can be
generated by in situ reduction of Cu(II) or oxidation of Cu(0)61ꢀ64. Besides it is known that common
nitrogen heterocycles such as phtalimide, pyrrole, imidazole and pyrazole derivatives are more reactive
in Ullmann coupling 65ꢀ68. In spite of the significant progress, more efficient, air or/and moistureꢀstable
and easyꢀsynthesized ligands are still in demand, in order to facilitate these coupling reactions under
relatively mild conditions. The copperꢀmediated Ullmann reaction still suffers from required drastic
reaction conditions: ligands and large amount of Cu are necessary for successful coupling reactions.
From these observations, and regarding the efficiency of palladium ecocatalsysts (EcoꢀPd®) developed
in our laboratory in crossꢀcoupling reactions18, the catalytic potential of EcoꢀCu® should be
investigated.
2.3.1. Results
With regard to the unusual acid properties of the EcoꢀCu® , it was interesting to study their reactivity in
arylation of amines and alcohols. The Lewis acidity of EcoꢀCu® was an interesting parameter to
modulate the reactivity of nucleophiles, and to activate the halide partners during the oxidative
addition step.
The first part of this work is a comparative study of the different EcoꢀCu® catalysts on a model
coupling reaction. It is known that common nitrogen heterocycles such as phtalimide, pyrrole,
imidazole and pyrazole derivatives are particularly reactive in the Ullmann coupling reaction65ꢀ68
.
Thus, the model Nꢀarylation was performed with pyrazole and iodobenzene, using the conditions
described by Taillefer et al.65 who developed one of the few examples of bimetallic catalysis69, 70
.
Cesium carbonate was chosen to avoid the use of strong bases, as described by the group of
Buchwald71 in diaryl ether synthesis. Many different copper salts and oxides have been used to
catalyze Ullmannꢀtype reactions. These results suggested that each EcoꢀCu®could be efficient in the
®
®
®
reaction. However we observed that EcoꢀCu® activated by HCl (EcoꢀCu2 , EcoꢀCu4 , EcoꢀCu6 and
EcoꢀCu8 ) are much more efficient than EcoꢀCu® solely thermally treated (EcoꢀCu1 , EcoꢀCu3 , Ecoꢀ
®
®
®
®
®
Cu5 , and EcoꢀCu7 ) (Table 5). Then, we observed a direct correlation between coupling efficiency
and copper concentration inside the catalyst, which is an essential observation concerning the recovery
®
of biomass obtained via phytoextraction or rhizofiltration technics. Indeed, although EcoꢀCu4 , Ecoꢀ
Cu6® and EcoꢀCu8® give similar good conversion rates with copper concentrations from 2 to 10 percent
®
by weight (Table 5), EcoꢀCu2 with only 0.26 percent by weight of copper, has shown a much lower
conversion rate.
Moreover, with most of the ecocatalysts, we managed to get good yields with only 1mol% of copper,
which is a very low catalytic loading compared to studies described in previous literature (10ꢀ20
mol%)72ꢀ74. Using small amounts of catalyst is a significant advantage for this type of CꢀN coupling

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reaction, both for practical, environmental and economic reasons. Thus, we attempted to optimize the
®
catalyst amount using the most active ecocatalyst, EcoꢀCu8 , (entries 8, 9, 10). The coupling reaction
was still possible with 0.25 mol% of copper (entry 10). Surprisingly, increasing the catalyst amount
did not improve the conversion rate (entry 9).As the results show, the catalytic loading of 1 mol% is a
very good compromise between catalyst economy and chemical efficiency. It is important to mention
that similar reactions under ligandꢀfree conditions, described in literature, require a considerably
higher loading of copper sources and more drastic reaction conditions e.g. 20 mol%, 8h at 120oC in nꢀ
PrCNas described by Hu an coworkers75, or 10 mol%, 24h at 120oC in DMF as described by Zhang et
al.74. In comparison, the same authors reported that the Nꢀarylation of pyrazole with iodobenzene using
an excess of tetraethylenepentamine (TEPA) (2 equiv.), as a base, and 10 mol% of copper source were
still necessary, TBAB (0.3 equiv.) and reaction time of 12 h at 125oC76. The loading of copper could
be reduced to 5 mol%. However, if the amount of copper is reduced, then use of unusual copper
sources such as CuO hollow nanospheres immobilized onto acetylene black77, or Cu2O coated Cu
nanoparticles78, must be used. Unfortunately, both protocols require harsh reaction conditions, 18h at
180oC and 18h at 150oC, respectively. Finally the loading of copper sources of 0.08 mol% for the Nꢀ
arylation of pyrazole with iodobenzene under ligandꢀfreeꢀlike conditions was reported by Bolmet. al.79.
However the reaction described requires the presence of DMEDA (20 mol%). It was carried out at
135oC for 24 h and authors did not test other aryl halides, thus the scope of the reaction remains
unknown. It can be concluded therefore, that the use of EcoꢀCu® catalysts represents a clear advantage
over the literature protocols.
Finally, the results obtained with the use of EcoꢀCu® catalysts can also be advantageously compared to
commercial Cu catalysts, such as CuCl2, CuCl and CuO (entries 11, 12, 13and 14). Commercial CuO
exhibited poor activity in the conditions used. Commercial CuCl2 and CuCl promoted the reaction, but
®
conversion rates were lower than those obtained with EcoꢀCu8 . These results demonstrated the
performance of EcoꢀCu®.
Table 5. Screening of EcoꢀCu® using fixed reaction conditions.
Entrya EcoꢀCu® catalyst Cu in catalyst (wt. %) Cu quantity (mol%)
Yields (%)b
®
1
EcoꢀCu1
EcoꢀCu2
EcoꢀCu3
EcoꢀCu4
EcoꢀCu5
EcoꢀCu6
EcoꢀCu7
0.38
0.26
9.1
4.8
3.3
2.0
18
1
1
1
1
1
1
1
25c
37c
18c
84
®
®
®
®
®
®
2
3
4
5
6
7
11c
77
66

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®
Eco-Cu8
10
10
10
1
85
8
9
®
EcoꢀCu8
EcoꢀCu8
4
83
57
®
10
0.25
11
12
13
14
CuCl2
CuCl2
CuCl
CuO
ꢀ
ꢀ
ꢀ
ꢀ
1
3
1
1
48c
79c
76c
9c
aReaction conditions: iodobenzene (5 mmol), pyrazole (7.5 mmol), EcoꢀCu® (50 µmol), Cs2CO3 (10 mmol), DMF (5 mL),
90 °C, 15 h, argon atmosphere
bIsolated yields
cYields were determined by GCꢀMS analysis
EcoꢀCu8® appears as a highly active catalyst in Nꢀarylation reaction without ligands and additives,
which represents a valuable alternative compared to classical catalytic systems used in literature.
Moreover, the reaction requires a considerably low quantity of Cu (1 mol%). This is important in light
of the need to lower the residual copper levels in the product after workꢀup, especially in the case of
pharmaceutical synthesis.
The very good performance of EcoꢀCu8® could be partially explained by its polymetallic composition,
and more precisely by the presence of alkaline metals, as highlighted by ICPꢀMS analysis (see section
2.2.2). Indeed, Zhang et al.80, have demonstrated the benefits of inorganic salt particles in transition
metalꢀcatalyzed coupling reactions. The partial negative charges on the salt surface create an electronꢀ
donating effect, which increases the electron density of the metal center. Besides, the anions at the
surface of the solid salt particles have a similar influence on the aryl halide. The combination of these
effects promotes the oxidative addition step and enhances the reaction rate.
Furthermore, Fan et al. have described the activity of several Lewis acids to assist the polarization of
the arylꢀhalogen bond. Significant rateꢀenhancement has been reported by addition of catalytic
amounts of Lewis acids during transition metalꢀcatalyzed cross coupling reactions81, 82. As metallic
elements highlighted by ICPꢀMS analysis in EcoꢀCu8® are Lewis acids, they might thus promote the
reaction.
Finally, these results are consistent with our previous work on HeckꢀMizoroki and SuzukiꢀMiyaura
cross coupling reactions with EcoꢀPd® catalysts18, characterized by an excellent dispersion of active
centers on the saline matrix.
After this first screening of different EcoꢀCu® catalysts, the methodology has been extended to
®
different amines, by using the most active catalyst, EcoꢀCu8 , with Cs2CO3 at 90°C. As shown in
Table 6, azole derivatives are the most reactive substrates, whereas no conversion rate was observed
with aniline. Besides, low conversion rates were obtained with secondary amines such as pyrrolidine
and morpholine (entries 5 and 6).
Table 6. Screening of amines using fixed reaction conditions.

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Entrya
Nucleophile
pyrazole
Yield (%)b
GC/MS spectral datad
rt = 11.63 min,
1
2
85
m/z = 144 (51, 77, 90, 117)
rt = 12.76 min,
imidazole
54
m/z = 144 (51, 77, 90, 117)
3
4
7
8
2ꢀpyrrolidone
aniline
31c
0c
pyrrolidine
morpholine
6c
5c
®
aReaction conditions: iodobenzene (5 mmol), nucleophile (7.5 mmol), EcoꢀCu8 (50 µmol), Cs2CO3 (10 mmol), DMF (5
mL), 90°C, 15 h, argon atmosphere
bIsolated yields
cYields were determined by GCꢀMS analysis
dAll compounds synthetized were fully characterized and found to be in agreement with the literature data
. GC retention
time and mass spectrometry (EI) data are given.
After those preliminary results, our efforts have been focused on pyrazole as nucleophile for Ullmann
condensation. Numerous aryl halides substituted with various electronꢀwithdrawing and ꢀdonating
groups were investigated (Table 7) at different temperatures, with Cs2CO3 as base, 1mol% of catalytic
charge and without ligands. The Ullmann reaction required DMF as solvent. Indeed water, toluene and
γꢀvalerolactone were tested as green solvents83 but the reaction did not occur, except in γꢀvalerolactone
with limited conversion rate (results not shown). The usual influence of the nature of the halide in
®
coupling reactions was respected (entries 1, 5 and 9). EcoꢀCu8 was efficient in crossꢀcoupling
reactions with aryl iodides, aryl bromides and even aryl chlorides. The use of aryl chlorides in
Ullmann type reactions is especially desirable to industries, because they are often less expensive than
iodides and bromides, thus their use has a real economic advantage84.
Tertiary amines were formed in good to excellent yields if temperature was adjusted. Noteworthy, the
coupling reaction of pyrazole was sensitive to electronic effects of substituents on aryl halides partners.
The presence of p-OMe electronꢀdonating substituent clearly diminished the efficiency of the reaction.
This could be counter balanced by a moderate elevation of the reaction temperature (entries 1, 2 and 3)
from 90 to 110°C. Finally, electronꢀwithdrawing groups facilitated the coupling reaction depending on
the electronegativity of the groups (entries 4ꢀ9). Thus, the reaction was quantitative in4h at 90°C using
iodoacetophenone (entry 4).
Table 7. Aryl halides and temperature conditions screening.

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Eco-Cu®
8
HN
+
N
R
I
Cs2CO3, DMF,
90°C, 15 h
N
N
Entrya
1
Aryl halide
T°C
90
Time (h)
15
Yield(%)b
GC/MS spectral data d
rt = 11.63 min,
85
m/z = 144 (51, 77, 90, 117)
rt = 13.97 min,
2
3
90
15
15
63c
m/z = 174 (77, 131, 159)
110
93
rt = 15.31 min,
4
5
90
90
4
>98
m/z = 186 (89, 116, 143, 171)
15
31c
rt = 15.55 min,
6
7
8
9
90
90
4
4
>98
>98
73
m/z = 189 (65, 89, 116, 131,
159)
rt = 14.61 min,
90
15
15
m/z = 169 (75, 102, 115, 142)
110
89
®
aReaction conditions: Aryl halide (5 mmol), pyrazole (7.5 mmol), EcoꢀCu8 (50 µmol), Cs2CO3 (10 mmol), DMF (5 mL),
argon atmosphere
bIsolated yields
cYields were determined by GCꢀMS analysis

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85
dAll compounds synthetized were fully characterized and found to be in agreement with the literature data
time and mass spectrometry (EI) data are described.
. GC retention
Finally, regarding the encouraging results obtained in arylation of amines, the efficiency of EcoꢀCu8®
catalyst was studied in the synthesis of alkyl aryl ethers (Table 8). The synthesis of the latter was
already described by Ullmann in his original articles46, 47. However, despite the recent progress in the
catalytic Ullmann reaction, less articles have appeared for the CꢀO than for the CꢀN coupling reaction.
The most convenient approach is based on the reaction of aryl bromides or iodides with phenols and
usually involves the presence of high ligand and copper loadings (10ꢀ30%mol)86ꢀ89 and elevated
temperatures (50ꢀ110oC)87ꢀ89. In the case of the use of aryl chlorides even higher temperatures are
necessary (135oC)90. Importantly, examples involving “ligandꢀfree” coupling of aryl halides with
phenols are scarcely described in the literature and they usually require extreme reaction conditions
(temperatures of 150ꢀ160oC)91, 92
.
The EcoꢀCu®ꢀcatalyzed CꢀO bondꢀforming reactions were very efficient, without ligands and with
Cs2O3 as base. In the presence of 1 mol% of Cu, satisfactory to high yields were obtained for various
aryl alkyl ethers. Contrary to conventional procedures, the reaction was sensitive to both electronꢀ
withdrawing and ꢀdonating groups on the substrates, and also to the nature of the halide partner. Indeed
good conversion rates were obtained with aryl iodides and aryl bromides in mild conditions (entries 1ꢀ
5), whereas strong activating substituents and an increase in the reaction temperature were required to
perform the coupling reaction with aryl chlorides (entries 11ꢀ12). These conditions were compatible
with a wide range of functionalities including nitriles, ketones, ethers, alkyl and nitro groups.
Table 8.EcoꢀCu®ꢀcatalyzed synthesis of alkyl aryl ethers
Aryl
GC/MS
Entrya
1
Nucleophile T°C
110
Product
Yield(%)b
66c
halide
spectral datad
rt = 14.17 min,
m/z = 198 (77,
91, 155, 183)93
rt = 14.72 min,
m/z = 200 (51,
77, 129, 185)93
2
110
64c
rt = 17.13 min,
m/z = 240 (77,
105, 225)94
3
4
110
130
>98
>98

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5
6
7
130
130
130
>98
84
82
rt = 14.62 min,
m/z = 200 (51,
77, 92, 129,
157)95
8
130
92
9
130
110
51c
rt = 18.18 min,
m/z = 240 (80,
108, 210)96
10
>98
rt = 17.29 min,
m/z = 243 (77,
108, 170,
11
12
110
110
>98
>98
213)97
aReaction conditions: Aryl halide (5 mmol), phenol (6mmol), EcoꢀCu8® (50 µmol), Cs2CO3 (10 mmol), DMF (5 mL), 15 h,
argon atmosphere
bIsolated yield
c Yields were determined by GCꢀMS analysis
dAll compounds synthetized were fully characterized and found to be in agreement with the literature data: GC retention
time / Mass spectrometry (EI) / literature references for NMR spectroscopy are given
Innovative reusability technologies of EcoꢀCu8® through ecological recycling based on rhizofiltration
were under investigation"
3. Experimental Section
3.1. General remarks

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NMR spectra were recorded on a Brüker Avance 300 spectrometer at room temperature, 1H frequency
is at 300 MHz, 13C frequency is at 75 MHz. IR spectra were recorded on a Perkin Elmer Spectrum 100
FTꢀIR spectrometer in ATR mode. GCꢀMS analyses were performed on a Shimadzu QP2010SE
apparatus. Two different methods were used for analysis. Method A: GCꢀMS (Phenomenex ZBꢀ5MSi
Guardian column, 0.25 ꢁm x 0.25 mm x 30 m) with hydrogen as carrier gas using the following
temperature program: isothermal at 80°C (4 min), then linear gradient from 80°C to 270°C at
20°C/min.Method B: GCꢀMS (Phenomenex ZBꢀ5MSi Guardian column, 0.18 ꢁm x 0.18 mm x 20 m)
with hydrogen as carrier gas using the following temperature program: isothermal at 100°C (1 min),
then linear gradient from 100°C to 145°C at 50°C/min, then isothermal at 145°C (0.50 min), then
increasing from 145°C to 190°C at 50°C/min, then isothermal at 190°C (0.60 min), and finally
increasing from 190°C to 320°C at 90°C/min.GCꢀMS samples were prepared in dichloromethane using
1,1’ꢀbiphenyl as internal standard. Mass spectra were recorded in electron impact (EI) mode at 70 V
and identified by comparison with data of the NIST 11 software library and by comparison of the
retention time of the standard compounds. Xꢀray photoelectron spectroscopy (XPS) analysis were
performed with a Kratos Analytical Axis Ultra DLD, using an Al Kα source monochromatized at
1486.6 eV. We used a hemispheric analyzer working at pass energy of 50 eV for the global spectrum
and 20 eV when focusing on the sole core levels. Directꢀinjection mass spectrometry was performed
with a Micromass Quattro micro API™, which was combined with HPLC detector and triple
quadrupolemass analyser for determining massꢀtoꢀcharge ratio (m/z). The transmission electron
microscopy (TEM) images were taken using a Jeol 1400 Plus Transmission Electron
Microscope at accelerating voltage of 120 kV. Ecocatalyst was put in suspension in EtOH 70%
and was dropped off on a grid CF 300ꢀCu (carbon film on 300 Mesh copper grids).
3.2. Elemental analyses
Chemical element analyses of plants and ecocatalysts were determined by ICPꢀMS analyses
(inductively coupled plasma mass spectrometry). ICPꢀMS analyses were performed using the metal
analysis of total dissolved solutes in water. The samples were first digested either in a mixture of
hydrochloric acid (37%) (8 mL) and nitric acid (65%) (2 mL) (L. multiflorum, E. crassipes and
ecocatalysts EcoꢀCu®), or in pure nitric acid (B. monnieri, A. chinensis) using a microwaveꢀassisted
digestion. Microwave digestions were performed on a Mileston ETHOS Touch Control device with
two different temperature programs: 1. Linear gradient from 20 to 90°C at 10°C/mn, then from 90 to
170°C at 16°C/mn, then from 170 to 210°C at 10°C/mn and then 20 min isothermal at 210°C (L.
multiflorum, E. crassipes, and ecocatalysts EcoꢀCu®); 2. Linear gradient from 20 °C to 180°C at 32
°C/mn, then 10 min isothermal at 180 °C (B. monnieri, A. chinensis). Samples were then diluted to 0.1
mg.Lꢀ1 in 2.5% aqueous nitric acid. Three blanks were recorded for each step of the digestion and
dilution procedure. ICPꢀMS analyses were performed on a Thermo Scientific™ ELEMENT XR™
ICPꢀMS.All analysis results were performed in triplicate.
3.3. Phytoextraction

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Study site
The study site is the “Mine de l’Etoile”, in the vicinity of Lubumbashi, a “locus classicus” of Cu and
Co hyperaccumulation by plants in Katanga (Democratic Republic of the Congo)22. Soil of “Mine de
l’Etoile” is contaminated by tailings which were spontaneously colonized by some CuꢀCo tolerant
species. Total Cu concentrations in soil vary from 10,000 to 30,000 mg.kgꢀ1 20
.
A. chinensis L. Hook.f. & Arn. (Asteraceae) is a perennial pseudoꢀmetallophyte presenting a large
variation of Cu concentrations in shoots in natura23, 24. Plant shoots of 20 individuals of A. chinensis
were collected all over the “Mine de l’Etoile” (11° 38′ S; 27° 35′ E,. 1277 m asl). This site is
characterized by a subtropical humid climate including a rainy season (from November to March) and
a dry season (from May to September). Maximum density of individuals (ind) of A. chinensis were
estimated to 15 ind/m2 from field observations (i.e. mean of 10 quadrats of m2). Biomass productivity
(BP) of monospecific crop of A. chinensis was then estimated: BP = mean biomass of A. chinensis
individual x 15.
Determinations of Cu concentration in plant shoots
After harvesting, plants were carefully brushed (whole shoots), washed with Alconox® 1% in
deionized water, dried at 65°C for 48h22 and weighted. Determination of Cu concentration in A.
chinensis was performed in two steps. A mass of leaves was digested using a mixture of 8 mL HNO3
and 2 mL HCl98 Vessels containing the mix were heated by microwaves for digestion24, 99.Then, Cu
concentration in samples was determined by ICPꢀMS.
Evaluation of phytoextraction parameters
Cu amount phytoextracted per hectare and per year was calculated by the following formula:
YCu = FCu.Ybio
FCu: Average fraction of Cu in A. chinensis biomass
Ybio: Biomass productivity of hyperaccumulator (kg/ha/year)
YCu: Total Cu gain (g/ha/year)
3.4. Rhizofiltration
Germination and growth
B. monnieri was bought directly in a garden center Jardiland. It was then immersed in a hydroponic
reservoir with a natural substrate called Manado (pozzolan) and 17 L of distillated water. The plants
were fed once every week with a fertilizer called “S7 Vitamix”, mainly containing 0.65% K2O, 0.14%
Mg, 0.41% S, 0.06% N, 0.065% Fe, 0.026% Mn. The plants were grown under neon light (12 h per
day) and under ambient temperature. The cultivation lasted 5 months in these conditions before the
beginning of copper accumulation.

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L. multiflorum was grown in our lab. Seeds were first transferred in Fleximix Root Riot Organic
Starter Cubes©, 82% of seeds were germinated after 9 days. The culture plate was placed in a shallow
hydroponic reservoir, to be sure that only the roots of the plants were immersed in water at ambient
temperature. The plants were fed with a fertilizer called “water lily dream” containing 1% K2O, 0.14%
Mo, 0.0028% Zn, 0.0027% Cu, 0.0004% Li. They were exposed during 8 weeks, 12 h per day, under
mercury lamp UV (37,000 lumens), before the beginning of copper accumulation.
E. crassipes was bought in a garden center Jardiland. They were put in an outdoor pool with water
during 6 months without additional fertilizer.
Conditions of accumulation
After five months of growth, B. monnieri was placed in another hydroponic reservoir, without
substrate, and with 17 L of an aqueous solution made of distillated water and 40 mg/L of
Cu(NO3)2.3H2O (10.5 mg/L of Cu). The accumulation occurred under ambient temperature, and under
neon light (12 h per day), during 7 days.
After 8 weeks of growth, L. multiflorum was exposed to an aqueous media made of distillated water
with 40 mg/L of Cu(NO3)2.3H2O (10.5 mg/L of Cu). The accumulation occurred under ambient
temperature, and under mercury lamp UV (37,000 lumens), during 7 days.
After 6 months in the pool, E. crassipes was exposed to an aqueous solution made of 40 mg/L of
Cu(NO3)2.3H2O(10.5 mg/L of Cu). The accumulation occurred outside (the plants suffered from
necrosis quickly in inside pool), during 7 days.
Crops
The plants were collected and separated into roots and aerial parts. Plant tissues were washed with
distillated water to remove any metallic particles attached to the plant surfaces. Then the biomass was
dried in an oven at 80°C during 48 h.
Evaluation of rhizofiltration parameters
Biomass measuring:
Once harvested and dried, the root biomass and the shoot biomass were weighted for each plant.
BCF (bioconcentration factor):
The BCF was calculated as the ratio of a given element concentration in the plant tissues (P, mg/kg dry
weight) at harvest to the concentration of the element in the effluent (E, mg/L) according to Eq.(1)
BCF=P/E
(1)
TF (translocation factor):
TF was calculated by dividing the Cu concentration in shoot tissues (As, mg/kg dry weight) by the
concentration of Cu accumulated in root tissues (Ar, mg/kg dry weight) (Eq.(2)):
TF = (As/Ar)
(2)
Determination of metals concentration in roots and shoots

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22
Metal concentrations in roots and shoots were determined by ICPꢀMS. The procedure is the same as
described in section 3.2., Elemental analyses.
3.4. Preparation of Eco-Cu® catalysts
EcoꢀCu® catalysts were prepared either from roots of plants used for rhizofiltration, or from harvested
leaves of plants used for phytoextraction. Biomasses were first dried into an oven at 80°C, then
thermally treated in an oven using the following temperature program: linear gradient from 20 to
®
550°C (1 h)and then 4 hours at 550°C before a slow cooling overnight to obtain ashes (EcoꢀCu1 (A.
chinensis), EcoꢀCu3® (B. monnieri), EcoꢀCu5 (L. multiflorum) and EcoꢀCu7 (E. crassipes)). Thereafter
the ashes obtained were subjected to a chemical treatment. The typical procedure used was as follow:
around 50 mg of ashes were suspended in concentrated hydrochloric acid (5 mL). The solutions were
stirred at 80 °C for 4h and then evaporated to dryness under vacuum to get EcoꢀCu2® (A. chinensis),
®
®
®
®
®
EcoꢀCu4 (B. monnieri), EcoꢀCu6 (L. multiflorum) and EcoꢀCu8 (E. crassipes)) respectively, as
yellow powders. EcoꢀCu® catalysts were stored under vacuum in a desiccator.
®
®
®
®
Thermic treatment: EcoꢀCu1 , EcoꢀCu3 , EcoꢀCu5 , EcoꢀCu7
®
®
®
®
Thermic and chemical treatment; EcoꢀCu2 , EcoꢀCu4 , EcoꢀCu6 , EcoꢀCu8
3.4. Characterization of Eco-Cu® catalysts
3.4.1. Chemical element analysis
ICPꢀMS was used to determine the composition of the various ecocatalysts prepared. ICPꢀMS analyses
were performed as described section 3.2. Elemental analyses.
3.4.2. Acidity characterization
PyridineꢀFTIR (Fourier transform infrared spectroscopy):
Excess pyridine was adsorbed on catalysts, then the samples were degassed for 15 min at 23 °C (10−3
Pa) and a first IR spectrum was recorded. The samples were then degassed for 30 min at 150 °C (10−3
Pa) to eliminate the physisorbed pyridine and a second IR spectrum was recorded.
Rearrangement of αꢀbromopropiophenone cyclic acetal:
A solution of αꢀbromopropiophenone cyclic acetal (75.8 mg, 295 µmol, 1 equiv.) in 1,2ꢀ
dichlorobenzene (3.35 mL) was poured onto catalyst (mass corresponding to 12.4 ꢁmol of Cu, 0.04
equiv.). Thereafter water was added (5.31 µL, 295 ꢁmol, 1 equiv.) and the resulting suspension was
stirred at 175°C for 20 h. The crude was analyzed by GCꢀMS (method B).
®
3.4.3. Analytic test of EcoꢀCu8

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®
EcoCu8 (8.1 µmol of Cu, 5 mg) was suspended into aq. 30 w% ammonia (200 µL). The suspension
was vortexed and the liquid phase turned deep blue within 1 minute demonstrating the presence of
Cu2+ into our catalyst by forming [Cu(NH3)4]2+ complexes. The mixture was centrifuged for better
observation of the solution.
3.5. General procedure for catalytic Ullmann coupling reaction and analysis of reaction products
The general procedure is described here with the case of 1H-pyrazole.
To a solution of 1Hꢀpyrazole (510 mg, 7.5 mmol) and iodobenzene (560 µL, 5.0 mmol) in dry DMF (5
mL) were sequentially added: EcoꢀCu® catalysts (3.3 mg, 0.05 mmol of Cu) and Cs2CO3 (3.25 g, 10.0
mmol). The resulting mixture was stirred at 90°C under inert atmosphere for 15 h. After cooling to
room temperature, the crude was diluted with ethyl acetate, filtered and concentrated under reduced
pressure. The resulting residue was purified on a silica gel column (Cyclohexane/ethyl acetate 8:2) to
give 1ꢀphenylꢀ1Hꢀpyrazole as a colourless oil (647 mg, 90% yield). 1H NMR (300 MHz, CDCl3) ppm:
δ
= 7.93ꢀ7.92 (dd, 1H), 7.76ꢀ7.70 (m, 3H), 7.49ꢀ7.42 (m, 2H), 7.32ꢀ7.26 (m, 1H), 6.48ꢀ6.46 (m, 1H);
13C NMR (75 MHz, CDCl3) ppm:
δ = 143.6, 142.7, 131.9, 129.2, 128.9, 121.7, 110.1; MS (EI): m/z
144 (M+, 100%), 117, 104, 90, 77, 51.
4. Conclusion
The aim of this work was to prepare and to study novel copper catalysts based on using Cu
hyperaccumulator plants which present an interest for the phytoremediation of mining sites and
contaminated aqueous systems. From these studies, it may be concluded that the new catalytic systems
show a very interesting activity in the arylation of nucleophiles. The chemistry described in this article
demonstrated that EcoꢀCu® catalysts are original and show valuable physicochemical properties,
especially regarding their polymetallic composition. EcoꢀCu® catalysts offer unexplored potential for
coupling reactions, especially those deriving from rhizofiltration (E. crassipes). EcoꢀCu®ꢀcatalyzed Cꢀ
N and CꢀO bond forming reactions are interesting methods for the synthesis of tertiary amines and aryl
ethers. The development of these new ecocatalytic systems represents exciting opportunities to
valorize phytoremediation of polluted ecosystems and for future organic synthesis. The combination of
these beneficial properties will undoubtedly prompt further research efforts toward the development of
ecocatalysis.
Acknowledgments
The authors would like to thank the Centre National de la Recherche Scientifique (CNRS) for financial
support. Belgian Fund for Scientific Research (FRSFNRS) are acknowledged too, for financial support
to Bastien Lange, who is a research fellow of the Fonds pour la Recherche dans l’Industrie et
l’Agriculture (FRIA, Belgium). Finally, we thank the CRESICA and the University of New Caledonia
(M. Meyer and A. Douyere) for the TEM images.
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Page 27 of 27
RSC Advances
Ullmann reaction through ecocatalysis: insights from bioressource
and synthetic potential
Guillaume Clavé1, Claire Garel1, Brice-Loïc Renard1, Tomasz K.
Olszewski,2 Bastien Lange3,4, Mylor Shutcha5, Michel-Pierre Faucon3,
Claude Grison*
Eco-Cu