Copper and copper-manganese 1D coordination polymers: Synthesis optimization, crystal structure and preliminary studies as catalysts for Baylis–Hillman reactions

Article abstract of DOI:10.1016/j.ica.2020.119985

This work reports the influence of experimental parameters (pH and counter-ion) in the synthesis of the 1D coordination polymer [Cu(IDA)(H₂O)₂]_n (IDA = iminodiacetate), named here Cu-IDA. Copper-manganese bimetallic coordi

Full text of DOI:10.1016/j.ica.2020.119985

InorganicaChimicaActa514(2021)119985
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Research paper
Copper and copper-manganese 1D coordination polymers: Synthesis
optimization, crystal structure and preliminary studies as catalysts for
Baylis–Hillman reactions
Julyanna Cândido Dutra de Andradea, Lucas Araujo Trajano Silvaa, Claudio Gabriel Lima-Juniora,
Jaroslaw Chojnackib, Mário Luiz Araújo de Almeida Vasconcellosa, R.B. da Silvac,
⁎
Severino Alves Júniord, Fausthon Fred da Silvaa,
a Departamento de Química, UFPB, 58051-900 João Pessoa, PB, Brazil
b Department of Inorganic Chemistry, Gdansk University of Technology, 80-233 Gdansk, Poland
c Departamento de Física, UFRN, 59078-900 Natal, RN, Brazil
d Departamento de Química Fundamental, UFPE, 50590-470 Recife, PE, Brazil
A R T I C L E I N F O
A B S T R A C T
Keywords:
This work reports the influence of experimental parameters (pH and counter-ion) in the synthesis of the 1D
coordination polymer [Cu(IDA)(H2O)2]n (IDA = iminodiacetate), named here Cu-IDA. Copper-manganese bi-
metallic coordination polymers were also obtained by isomorphic replacement into Cu-IDA structure, with
different molar ratio of Cu2+ and Mn2+ ions, denoted here as Cu/Mn-IDA (0.9/0.1; 0.7/0.3 and 0.5/0.5). New
coordination polymers are isostructural to Cu-IDA and amounts of manganese atoms inserted into crystalline
structure were evaluated by single-crystal X-ray diffraction and Rietveld refinement. All coordination polymers
obtained were also characterized by infrared absorption spectroscopy and thermogravimetric analysis.
Homometallic and bimetallic compounds were evaluated as catalysts for Baylis-Hillman reaction with yields and
reaction times comparable or superior to those in the literature. Compounds containing manganese cations
shows higher catalytic performance, especially Cu/Mn-IDA (0.9/0.1) with yield 91% in 5 h of reaction. Results
also indicate an important role played by the metallic centre in the catalytic mechanism.
Coordination polymers
Mixed-metal
Baylis-Hillman reactions
1. Introduction
and lanthanide ions [16,17], however 3d-4f heterometallic systems
were also quite explored [18,19]. Despite several CPs based on imino-
Iminodiacetic acid (H2IDA) and its derivatives such as N-(2-hyrox-
yethyl)iminodiacetic acid are flexible ligands and powerful chelating
agents [1]. These ligands can form high stable coordination compounds
with lanthanides cations [2], and their transition metal-based com-
plexes have been applied in several fields of research such as catalysis
[3], adsorption [4], magnetic materials [5], scintigraphy [6] and as
structural models for metalloproteins [7]. Due to its amino acid-like
structure, H2IDA is extensively used as agents for surface functionali-
zation [1,8,9] and as precursor not only for ordinary coordination
compounds, [10] but also for different types of materials such as hy-
drogels [11], metal clusters with high nuclearity [12] and also co-
ordination polymers (CPs) [13–19].
diacetic acid were reported, 3d-3d heterometallic systems are not ex-
plored yet. Heterobimetallic systems based on 3d-transition metals are
extensively investigated mainly due to their magnetic properties
[21–23]. Many parameters such as temperature, pH and molar ratio
were also investigated to better understand relationships between these
experimental variables and the crystal structure of coordination poly-
mers with H2IDA [19,14,24].
The literature reports CP based on H2IDA and/or its derivatives
employed as catalyst in many organic reactions. Gomez and co-workers
show the antibacterial activity of bismuth-iminodiacetate and its cata-
lytic properties in cyanosilylation reaction using carbonyl compounds
as substrate [25]. Bagherzadeh et al. also demonstrated the chemose-
lective catalytic performance of the [Mn(HIDA)2(H2O)2]n in oxidation
of alcohols and sulphides [26]. Cancino et al. report the synthesis of
isostructural heterometallic coordination polymers {[Cu3Ln2(IDA)6]
CPs have been established in the last decade as important inorganic
crystalline materials, especially due to its applicability as catalysts [20].
H2IDA has been used to obtain CPs based on transition metals [13–15]
⁎ Corresponding author.
E-mail address: fausthon@quimica.ufpb.br (F.F. da Silva).
https://doi.org/10.1016/j.ica.2020.119985
Received 22 July 2020; Received in revised form 23 August 2020; Accepted 23 August 2020
Availableonline28August2020
0020-1693/©2020ElsevierB.V.Allrightsreserved.

J.C.D. de Andrade, et al.
InorganicaChimicaActa514(2021)119985
8·H2O}n (Ln = La, Gd or Yb) as catalysts for selective oxidation of
cycloalkenes [27]. Recently, Jacewicz and co-workers shows the po-
tentialities of the 1D-coordination polymer [Co(IDA)(H2O)2] as catalyst
for oligomerization of 2-chloro-2-propen-1-ol under normal pressure
and room temperature [28].
The system was left to rest at room temperature for few days. Blue
crystals obtained were filtered, washed with 5 mL of distilled water and
dried at room temperature. This procedure was repeated using different
molar proportions of Cu/Mn (0.7/0.3 and 0.5/0.5).
In this context, this paper explores the influence of experimental
parameters (pH and counter-ion) in the synthesis of a 1D-coordination
polymer based on iminodiacetic acid and copper cations with chemical
formula [Cu(IDA)(H2O)2]n, named here Cu-IDA. The synthesis of het-
erobimetallic coordination polymers containing copper and manganese
cations (Cu/Mn-IDA) were explored in different molar ratio of these
cations. CPs obtained were characterized by X-ray single-crystal dif-
fraction, X-ray powder diffraction (XRPD), thermogravimetric analysis
(TGA) and infrared spectroscopy (FT-IR).
2.3. Physical measurements
Infrared spectra (4000–400 cm−1) were recorded on a Shimadzu
model Prestige-21 spectrophotometer using KBr pallets. Elemental
Analysis CHN data (Table S1) were obtained in a CE Instruments ana-
lyser, model EA 1110. Thermogravimetric analyses were performed on
a Shimadzu model DTG-60H thermal analyser with a heating rate of
10 °C/min until 900 °C and N2 flow rate of 50 mL/min. XRPD patterns
were obtained in a Shimadzu diffractometer XRD-60000 with Kα(Cu)
1.54 Å source, step 0.02°, acquisition time of 1 s and window 5-50°.
Lattice parameters and atomics positions were determined by Rietveld
refinement using the software package Materials Analysis Using
Diffraction (MAUD).
Preliminary investigations about the performance of Cu-IDA and
bimetallic systems as catalyst in Baylis-Hillman reaction were carried
out. Since the 1980 s, this organic reaction became extensively ex-
plored, due the formation of CeC bonds and organic functions such as
hydroxyl groups, being utilized as synthetic route to obtain bioactive
compounds [29–31]. DABCO (1,4-diazabicyclo[2.2.2]octane) is the
most widely Lewis base used to promote these reactions, but many
reactions can still last for days with low yields, even using a stoichio-
metric ratio substrate/promoter [29–31]. Recently, coordination poly-
mers have been employed as catalyst for these organic reactions using
aromatic aldehydes as substrates with yields up to 92%, however with
reaction time up to 32 h [32–37]. Nevertheless, literature presents few
investigations in this area [32–37] which makes it a fruitful and un-
explored field of research.
2.4. Crystallography
For the samples Cu/Mn-IDA with 0.9/0.1, 0.7/0.3 and 0.5/0.5 M
ratios, single crystals were collected and their structures were solved
using single-crystal X-ray diffraction. Diffraction reflections intensity
data were collected on an IPDS 2T dual-beam diffractometer (STOE &
Cie GmbH, Darmstadt, Germany) at 120.0(2) K with MoKα or CuKα
radiation of a microfocus X-ray source (GeniX 3D Mo High Flux,
Xenocs, Sassenage, 50 kV, 1.0 mA, λ = 0.71069 Å or GeniX 3D Cu High
Flux, Xenocs, Sassenage, 50 kV, 0.6 mA, λ = 1.54186 Å). The in-
vestigated crystal was thermostated in nitrogen stream at 120 K using
CryoStream-800 device (Oxford CryoSystem, UK) during the entire
experiment. Data collection and data reduction were controlled by X-
Area 1.75 program. An absorption correction was performed on the
integrated reflections by a combination of frame scaling, reflection
scaling and a spherical absorption correction. The structures were
solved by intrinsic phasing methods (ShelXT [38,39]) and refined ani-
sotropically using the program packages Olex2 and SHELX-2015. Po-
sitions of the CeH hydrogen atoms were calculated geometrically and
taken into account with isotropic temperature factors. Water H-atoms
were refined as riding on their parent atoms using rotating group
model, except Cu/Mn-IDA (0.7/0.3 M ratio) where a model with con-
strained OeH bond lengths to 0.84(2) Å was applied. Hydrogen atoms
bound to nitrogen were refined with the NeH bond constrained to
0.88(2) Å. Metal atom site was refined as shared by Cu and Mn. Crys-
tallographic data were deposited in the Cambridge Crystallographic
Data Centre with CCDC numbers 1880235–1880237.
2. Experimental
2.1. Materials
Copper acetate hydrated (Cu2(AcO)4·2H2O, 98%) and copper
chloride dihydrated (CuCl2·2H2O, 99%) were obtained from Vetec.
Copper nitrate hydrated (Cu(NO3)2·2.5H2O, 98%) was obtained from
Acros Organics. Manganese sulphate (MnSO4·H2O, 99%) and imino-
diacetic acid (98%) was obtained from Sigma-Aldrich. All reagents
were used without previous purification.
2.2. Experimental procedure
2.2.1. Synthesis of [Cu(IDA)(H2O)2]n (Cu-IDA)
(a) Iminodiacetic acid (1.0 mmol, 270 mg) was dissolved in 5 mL of
distilled water (pH = 2, after full dissolution) and thereafter, 0.5 mmol
of Cu2(AcO)4·2H2O was added to this solution and dissolved under
stirring. The solution was left to rest at room temperature for few days.
The same procedure was used starting of copper nitrate and copper
chloride. Blue crystals were obtained only for the reaction with copper
acetate. Crystals were filtered, washed with 5 mL of distilled water and
dried at room temperature. Yield: 92% (based on the ligand).
(b) Iminodiacetic acid (1.0 mmol, 270 mg) was dissolved in 5 mL of
distilled water (pH = 2, after full dissolution). The pH of the solution
was adjusted to 7 using NaOH 0.1 M, then 1 mmol of copper salt
(chloride or nitrate) was dissolved in this solution under stirring. The
system was left to rest at room temperature for few days. The same
procedure was used starting of copper acetate, but no crystals were
observed. Blue crystals were obtained in the reactions with copper ni-
trate or copper chloride. The crystals were filtered, washed with 5 mL of
distilled water and dried at room temperature. Yield: 70% and 21%
(based on the ligand), respectively.
2.5. Catalytic assays
The catalytic activity in the Baylis-Hillman reaction of CPs was in-
vestigated using a procedure similar to the literature at room tem-
perature [40]. In a flask, 0.5 mmol of 3-nitrobenzaldehyde (75.5 mg)
was dissolved in 0.5 mL of methyl acrylate and 0.5 mL of N,N-di-
methylformamide (DMF). Then, 0.5 mmol (56.1 mg) of 1,4-diazabi-
cyclo[2.2.2]octane (DABCO) and 0.22 mmol (50 mg) of catalyst Cu-IDA
or Cu/Mn-IDA (0.9/0.1, 0.7/0.3 or 0.5/0.5) were added. The reactional
mixture was submitted to magnetic stirring at room temperature, and
the reaction was monitored by thin-layer chromatography using UV
light. In the end of the reaction, the catalyst was filtered off, and the
product was extracted using 60 mL H2O/ethyl acetate (1:1 v/v), and
Na2SO4 anhydrous was added to remove the residual water of the or-
ganic phase. The Na2SO4 was filtered off and product was obtained by
rotoevaporation. Isolated products were characterized by 1H and 13C
nuclear magnetic resonance (NMR) in a using Varian Mercury Spectra
AC 20 spectrometer (200 MHz for 1H, 50 MHz for 13C).
2.2.2. Synthesis of heterometallic CPs Cu/Mn-IDA
Iminodiacetic acid (1.0 mmol, 270 mg) was dissolved in 10 mL of
distilled water. Then, Cu2(AcO)4·2H2O (0.45 mmol) and MnSO4·H2O
(0.1 mmol) were added to this solution and dissolved under stirring.
2

J.C.D. de Andrade, et al.
InorganicaChimicaActa514(2021)119985
Fig. 1. Experimental conditions explored for the synthesis of the [Cu(IDA)(H2O)2]n coordination polymer.
3. Results and discussion
yield compared to the other reaction conditions investigated here,
however it was inefficient in pH 7 since no product was formed.
All successful experimental conditions resulted in blue prismatic
crystals, corresponding to the same crystalline phase, [Cu(IDA)(H2O)2]n
as confirmed in XRPD data. This compound is a 1D-coordination
polymer, already reported by Niclos-Gutierrez and co-workers [15].
These results indicate the influence of counter-ions and initial pH on
yields and reaction times, but not in crystalline phase obtained. Con-
sidering these observations, starting from copper acetate in pH 2 is the
best synthetic route with higher yield (92%) and lower reaction time
(one day). This methodology is faster and simpler with the same yield,
compared with the literature [15]. All experimental conditions and
results are summarized in the Fig. 1.
3.1. Cu-IDA system
3.1.1. Influence of counter-ion and pH on the synthesis
Cheetham [24] and Zhou [14] already report the influence of ex-
perimental parameters suchlike initial pH, stoichiometric ratio and
temperature in the complexation of H2IDA with transition metal ca-
tions. In this perspective, we explored the influence of the initial pH and
counter ions on the formation of coordination polymers with imino-
diacetic acid and Cu2+ ions in aqueous medium. Iminodiacetic acid
molecules generate zwitterionic species in acidic solution [41], thus the
coordination with metal cations should occur only through the carboxyl
groups due the protonation of amine groups. CPs with H2IDA and 3d-
metals obtained in acidic medium were already reported, such as [Mn
(HIDA)2(H2O)2]n [13] and [Zn(HIDA)2]·4H2O [14]. In these structures,
manganese and zinc ions are coordinated only through carboxyl groups,
forming 2D and 3D CPs, respectively.
3.1.2. XRPD, infrared spectroscopy and thermogravimetry
The experimental powder pattern of the sample obtained from the
copper acetate is shown in the Fig. 2, compared to the calculated pattern
from the CIF file [15]. High concordance between experimental and
calculated diffraction patterns was observed, confirming crystalline phase
obtained. The absence of additional peaks in the experimental powder
pattern indicates the high purity of the product, with no starting reagent
residues or secondary crystalline phases. The diffraction patterns of the
other samples are similar and shown in Fig. S1. In all cases, a preferential
orientation in the (020) plane, instead the (102) plane were observed.
IR spectra of the sample obtained from the copper acetate and the
free ligand are shown in Fig. S2. A broad band between 3500 and
3100 cm−1 is related to the asymmetric OeH stretching, characteristic
of systems structured by hydrogen bonds. The signal of the asymmetric
NeH stretching at 3174 cm−1 is shifted by 84 cm−1 in comparison with
the free ligand, due to the coordination with the metal cation. The
signals related to the carboxyl group are at 1572 cm−1 and 1388/
1400 cm−1 also shifted due to the metal–ligand interaction. The ab-
sence of the peak at 1583 cm−1 (CeOeH bending) indicates the total
deprotonation of the ligand. All signals are in good agreement with the
literature [26,27]. Vibrational spectra of the others Cu-IDA samples
shows the same profile (Fig. S3).
In our case, this tendency is not observed for Cu2+ ions, since no
crystals were obtained in the reactions starting with copper nitrate or
copper chloride in acid aqueous medium. Thus, the Cu–N bond plays an
important role in the reaction between the IDA ions and copper cations.
On the other hand, crystals were formed when the reaction was con-
ducted with copper acetate and initial pH 2. Acetate anions are strong
Brønsted base, and can deprotonate the amine groups of the zwitter-
ionic iminodiacetate, making nitrogen atoms able to coordinate with
Cu2+ ions. This mechanism was more efficient, increasing the reaction
The thermal stability of the Cu-IDA was investigated via TGA ana-
lysis (Fig. S4). The first event observed (117–151 °C) corresponds to the
loss of coordinated water molecules (14.69% exp.; 14.95% calc. for 1.9
molecules). After the total dehydration, several mass losses between
220 and 580 °C related to the ligand decomposition (50.55% exp.;
50.26% calc.) were noticed. The remaining mass (34.7% exp.; 34.5%
calc.) is associated to the formation of copper oxide.
3.2. Heterometallic systems
Fig. 2. Experimental powder patterns of the [Cu(IDA)(H2O)2]n obtained from
the copper acetate (black line) and calculated (red line). (For interpretation of
the references to color in this figure legend, the reader is referred to the web
version of this article.)
3.2.1. Crystal structure and XRPD
The [Cu(IDA)(H2O)2]n crystallizes in the orthorhombic crystal
system and Pbca space group [15] and its structure was determined
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J.C.D. de Andrade, et al.
InorganicaChimicaActa514(2021)119985
Structures were solved by intrinsic phasing (SHELXT [38,39]) and
refined with the metal atom site occupied by copper or manganese in
the ratio refined (using EXYZ and EADP instructions of SHELXL pro-
gram). Results are rather sensitive to errors, but unequivocally show
that some amount of Mn atoms is present in the structures (Table 2).
Starting with 0.9/0.1 or 0.7/0.3 M ratios, similar isomorphic substitu-
tion degree was observed in single crystals analysed. Since the Cu/Mn
molar ratio determination using monocrystal analysis may not be sig-
nificant for the bulk material, the molar proportion between was also
investigated via Rietveld refinement using experimental diffraction
patterns.
For all samples Cu/Mn-IDA, experimental powder patterns were
measured at room temperature (Fig. 5). Similar diffraction patterns
were observed in all samples; thus, the same crystalline phase was
obtained in all cases in agreement with the single crystal data. Com-
pounds were obtained with high phase purity, since the powder pat-
terns show no additional peaks. The isomorphic substitution in crys-
talline structures depends mainly of the ionic radii of the atomic species
involved. For coordination compounds, the metal ionic radium is also
related to the nature of ligands (high spin or low spin configurations).
The iminodiacetic acid is a weak-field ligand [44], and for high spin
configuration and coordination number six, Cu2+ and Mn2+ have ionic
radii 73 pm and 83 pm, respectively [45]. Shifts in the diffraction an-
gles were observed due to this difference of radii between copper and
manganese ions, leading to local distortion and changes in the unit cell
parameters.
Fig. 3. Coordination polyhedron and chemical environmental in [Cu(IDA)
(H2O)2]n. Hydrogen atoms were omitted.
Rietveld refinement was preformed to estimate the Cu/Mn molar
ratio from the experimental powder diffraction and results are show in
Tables 2, Table S5, Fig. 5 and Fig. S6. This method has been used
successfully to estimate atomic positions and stoichiometric proportion
in CP-based bimetallic systems [46,47], with results comparable to
other techniques more frequently used such as ICP-OES [47]. Lattice
parameters obtained for the Cu-IDA sample are
a = 10.258,
b = 10.438 and c = 13.698 Å, in agree with the related in literature
showed in Table 1. A slight change in this value was observed with the
replacement of Cu by Mn in structure (Table S5), such as in Cu/Mn-IDA
(0.5/0.5) a = 10.429, b = 10.409 and c = 13.679 Å. Low value of χ2
were observed (Fig. 5) confirms goodness of refinement values.
For Cu/Mn-IDA (0.9/0.1) both analyses show a higher amount of
manganese compared to the initial experimental proportion (Table 2).
For the other samples, these molar ratio values are located near the
experimental ratio. The difference between the values shown in Table 2
may also indicate a non-homogeneous distribution of the amount of
manganese in the crystals. Although the values obtained from single
crystals diffraction present a reasonable estimate of the percentage of
manganese inserted in the sample, the refinement determination in-
cludes a more significant portion of the sample, being more re-
presentative.
Fig. 4. Crystal packing of the [Cu(IDA)(H2O)2]n 1-D chains.
initially in 1979 [42] and redetermined in 1999 [18], named: catena-
((μ2-iminodiacetato)-diaqua-copper(ii)). Each Cu2+ cation is in an oc-
tahedral environment with tetragonal distortion, coordinated by one
atom of nitrogen, two oxygen atoms from water molecules and two
oxygen atoms from one IDA2- anion and one from another anion (Figs. 3
and 4). Iminodiacetate residue act as both triply chelating (κ3-N,O,O’)
ligand and bridging (κ-O”) ligand. One oxygen atom, O2, does not take
part in metal coordination, but forms rather strong O…HeO and O…
HeN hydrogen bonding with neighbour chains’ molecules. Coordina-
tion sphere of metal is saturated by two water molecules, engaged also
in intermolecular interactions among chains (Tables S2–S4). Mono-
meric coordination units are linked into endless zigzag chains spreading
parallel to the crystallographic a-axis (Fig. 4). The chains themselves
have non-trivial rod symmetry (p1121 or R9 see IUCr Tables, Vol. E
[43]), since the 21 screw axis passes through the rod centre and is the
symmetry element which maps every monomeric unit into another in
the same chain.
3.2.2. Infrared spectroscopy and thermogravimetry
In infrared spectra of bimetallic compounds (Fig. S7), the same
absorption profiles were observed compared to the initial crystalline
phase (CuIDA), in good agreement with XRPD results. No significant
shifts were observed in the main signals (CeO; C]O and CeN
stretching) in comparison to the compound with only copper ions, thus,
interactions between the ligand and Cu2+ and Mn2+ ions are very si-
milar.
Due to atomic similarity of copper and manganese it proved possible
to exchange both types of atoms and obtain isostructural solid-state
solutions with several proportions of Mn and Cu. The intense blue color
of the Cu-IDA compound is related to the electronic d-d transitions of
copper ions in the octahedral field. Thus, the increase in the con-
centration of Mn2+ ions in the solid solution led to a decrease in the
blue color intensity of the crystals (Fig. S5), indicating qualitatively the
insertion of theses ions into the crystal structure. Mixed-metal com-
pounds crystallize in the same space group with small deviations of unit
cell dimensions from the copper-only structure. Comparison of unit
cells is given in Table 1.
Thermal stability of heterometallic compounds was investigated
using thermogravimetric analysis. In the CuIDA, 1D chains are linked
through hydrogen bonds between IDA2- anions and coordinated water
molecules, and interactions is important to measure the thermal sta-
bility of the compound. Heterometallic compounds shows similar
thermal decomposition profile (Fig. 6), since all have the same crys-
talline structure in agreement with single-crystal diffraction and XDR
data. However, higher temperatures are required for the loss of co-
ordinated water molecules in the bimetallic compounds, leading to the
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J.C.D. de Andrade, et al.
InorganicaChimicaActa514(2021)119985
Table 1
Crystallographic data of Cu/Mn-IDA compounds and the reference [Cu(IDA)(H2O)2]n.
Cu/Mn-IDA (0.9/0.1)
Cu/Mn-IDA (0.7/0.3)
Cu/Mn-IDA (0.5/0.5)
Reference [42]
Crystal data
Chemical formula
Mr
C4H9Cu0.76Mn0.24NO6
C4H9Cu0.74Mn0.26NO6
228.38
C4H9Cu0.59Mn0.41NO6
227.14
C4H9NO6Cu
230.66
228.58
Crystal system, space group
Temperature (K)
a, b, c (Å)
Orthorhombic, Pbca
Orthorhombic, Pbca
120
Orthorhombic, Pbca
120
Orthorhombic, Pbca
203
120
10.1682 (3), 10.3412 (3), 13.5635
10.1614 (9), 10.3906 (10), 13.5823 10.2117 (8), 10.3446 (10), 13.5645 10.2024 (8), 10.3712
(3)
(17)
(10)
(7), 13.6089 (15)
V (Å3)
1426.22 (7)
1434.1 (3)
1432.9 (2)
1440.0 (2)
8
Z
8
8
8
Radiation type
Mo Kα
Cu Kα
Cu Kα
m (mm−1
)
2.76
7.20
8.75
Crystal size (mm)
Data collection
0.21 × 0.17 × 0.12
0.11 × 0.09 × 0.08
0.13 × 0.1 × 0.08
Diffractometer
STOE IPDS 2 T
STOE IPDS 2 T
STOE IPDS 2 T
Absorption correction
Integration
Integration
Integration
STOE X-RED32, absorption
correction by Gaussian integration*
0.787, 0.980
STOE X-RED32, absorption
correction by Gaussian integration*
0.783, 0.943
STOE X-RED32, absorption
correction by Gaussian integration*
0.786, 0.981
T
min, Tmax
No. of measured, independent and
13235, 1557, 1486
2416, 1006, 926
4099, 1063, 1036
observed [I > 2 s(I)]
reflections
Rint
0.043
27.0
0.044
59.0
0.079
60.5
θmax (°)
(sin θ/λ)max (Å−1
Refinement
)
0.639
0.556
0.564
R[F2 > 2σ(F2)], wR(F2), S
No. of reflections
0.034, 0.097, 1.14
0.057, 0.160, 1.08
0.083, 0.223, 1.08
1557
1006
1063
No. of parameters
No. of restraints
130
130
122
0
4
4
H-atom treatment
H atoms treated by a mixture of
independent and constrained
refinement
H atoms treated by a mixture of
independent and constrained
refinement
H atoms treated by a mixture of
independent and constrained
refinement
Δ > max, Δ > min(e Å−3
)
0.50, −0.66
0.56, −0.98
0.93, −1.25
*analogous to P. Coppens, “The Evaluation of Absorption and Extinction in Single-Crystal Structure Analysis”, published in F. R. Ahmed (Editor), “Crystallographic
Computing”, Munksgaard, Copenhagen (1970), 255 – 270.
Table 2
Degree of substitution of copper by manganese as determined by X-ray dif-
fraction single-crystal diffraction studies and Rietveld refinement.
Cu/Mn-IDA (0.9/0.1)
Cu/Mn-IDA (0.7/0.3)
Cu/Mn-IDA (0.5/0.5)
Single-crystal analysis
Cu
0.76
0.24
0.74
0.26
0.59
0.41
Mn
Rietveld refinement
Cu
0.82
0.18
0.69
0.31
0.53
0.47
Mn
structural decomposition. Therefore, the insertion of manganese into
CuIDA crystalline structure improves the thermal stability of the com-
pounds. After total decomposition, amounts of oxides observed de-
creases with the quantities of Mn inserted in the structure (Table 3),
may due to the lower atomic mass of the manganese compared to
copper.
3.3. Catalytic proprieties
Reactions were conducted using 3-nitrobenzaldehyde as substrate
(Fig. 7) in DMF at room temperature in presence and absence of
DABCO. Table 4 summarizes the yields and reaction times obtained in
the experiments. All successful reactions lead to only one product
(Methyl 2-[hydroxyl(3-nitrophenyl)methyl] acrylate) and 1H and 13C
NMR data are shown in Figs. S8 and S9.
DABCO and other Lewis bases are extensive used as reaction pro-
moter in Baylis-Hillman reactions, activating methyl acrylate molecules
to generate zwitterionic aza-enolate species (Fig. S10), in a mechanism
well established in the literature [29,48]. Initial catalytic assays were
Fig. 5. Experimental DRX and Rietveld refinement (red line) data of [Cu(IDA)
(H2O)2]n and Cu/Mn-IDA samples. (For interpretation of the references to color
in this figure legend, the reader is referred to the web version of this article.)
5

J.C.D. de Andrade, et al.
InorganicaChimicaActa514(2021)119985
Fig. 7. Reaction scheme in the catalytic assays.
Table 4
Reaction times and yields in catalytic assays.a
Entry
Catalyst/Promoter
Time (h)
Yield (%)b
1
2
3
4
5
6
7
DABCO
23
23
23
23
5
43
73
NR
NR
91
64
56
Cu-IDA/DABCO
Cu-IDA/DABCOc
Cu-IDAd
Cu/Mn-IDA (0.9/0.1)/DABCO
Cu/Mn-IDA (0.7/0.3)/DABCO
Cu/Mn-IDA (0.5/0.5)/DABCO
Fig. 6. TGA curves of heterobimetallic compounds.
5
5
conducted with the presence of 100 mol% (1:1 M ratio) of DABCO
(Table 4, entry 1), leading to yield 43% in 23 h. The addition of Cu-IDA
in the reaction (Table 4, entry 2) increases the yield to 73% fixing the
same reaction time, however using 10 mol% of DABCO (Table 4, entry
3) no product was formed. If the reaction in presence of Cu-IDA follows
a similar mechanism shown in Fig. S10, the absence of product agrees
with the literature, since the rate law in this mechanism depends on the
DABCO concentration [48].
a
Reactional condition: aldehyde (0.5 mmol), 0.5 mL methyl acrylate,
DABCO (0.5 mmol, 100 mol%), 0.22 mmol (50 mg) of the catalyst and 0.5 mL
de DMF. All experiments were carried out at room temperature.
b
c
d
Yield calculated after the isolated product; NR = No reaction.
Same conditions, but using 0.05 mmol of DABCO (10 mol%).
Reaction without DABCO.
bimetallic structure compared to the isostructural monometallic com-
pound is already reported in others coordination polymers [56,57].
Catalytic performance of Cu/Mn-IDA (0.7/0.3) and Cu/Mn-IDA
(0.5/0.5) were comparatively investigated fixing the reaction time in
5 h (Table 4, entry 6 and 7) and measured yields were 64% and 56%,
respectively. This allows to establish a preliminary relationship be-
tween the catalytic activity and amounts of manganese atoms into the
structure. A decreasing in reaction yields was observed when the molar
ratio of manganese ions increases into the crystal structure. High
amounts of manganese in the structure leads to more active sites closer
to each other, which can cause a steric impediment between adsorbed
species in these sites nearby, and this can be the main factor to the yield
decreasing in the first five hours of reaction. Other bimetallic systems
still seem to have superior catalytic performance when compared to Cu-
IDA, however further studies should be conducted to confirm this ob-
servation.
In absence of DABCO no product was observed (Table 4, entry 4).
This confirms the importance of DABCO in stoichiometric proportion to
increase the efficiency of the catalytic process. These observations also
suggest that even in the presence of Cu-IDA, the reaction may follow a
same mechanism to the one only in the presence of the Lewis base.
Similar results were found by Aggarwal and co-workers in lanthanide
coordination compounds as catalyst in Baylis-Hillman reactions using
methyl acrylate and benzaldehyde as substrates [49,50]. In this case,
metal complexes may act as Lewis acids increasing reaction rates by the
stabilization of the aza-enolate and/or activating the aldehyde through
coordinate bonds with the metal cations [49,50]. The cooperative Lewis
acid/base mechanism was also observed in asymmetric reactions also
mediated by lanthanide complexes [51,52] and used to understand the
catalytic activity of transition metals such as titanium [53] and palla-
dium [54] in Baylis-Hillman reactions.
Heterobimetallic compounds obtained were also investigated as
catalysts in the presence of DABCO and results were also shown in
Table 4. Cu/Mn-IDA (0.9/0.1) presents high performance (entry 5) with
91% yield and time reaction of five hours. Based on the mechanism
reported to metal complexes as catalysts [49–54], two steps are de-
terminant to the reaction rate: (a) stabilization of the aza-enolate and
(b) the nucleophilic substitution in the aldehyde carbonyl group; and
both are mediated by the coordination with metal cations. In this
process, the literature reports the superior efficiency of harder cations
due to their tendency to form more labile DABCO-Lewis acid complex
[50]. Moreover, there is a relationship between the increasing in the
cation ionic radius and higher reaction rates [50]. This can justify the
superior catalytic performance of the Cu/Mn-IDA (0.9/0.1), since Mn2+
ions have higher ionic radii [45] and are harder Lewis acids [55]
compared to Cu2+ ions. Improvements in catalytic performance of
Few studies were conducted to explore the catalytic activity of co-
ordination polymers in Baylis-Hillman reactions [32–37], and me-
chanistic aspects are not detailed yet. Hydrogen bonds must play an
important role in the catalytic mechanism as reported in other CPs in
the literature [35]. However, experiments involving Cu/Mn-IDA ma-
terials here indicates a relationship between the catalytic activity and
the nature of the cation centre. Therefore, it is reasonable to assume the
coordination with the metal centre as the main aspect in the catalytic
activity of these materials, similar to proposed mechanism for metal-
triflates catalysts [49–52]. Considering these experimental observations
and the literature [49–52], a proposal for the catalytic mechanism is
shown in Fig. 8. The transition state proposed consists in the metal
centre coordinated by the aldehyde and aza-enolate in substitution to
water molecules, before the nucleophilic attack on carbonyl group
(Fig. 8). Leaving water molecules are adjacent (cis position, Fig. 3),
Table 3
Thermal decomposition data of [Cu(IDA)(H2O)2]n compared to heterobimetallic compounds.
Cu-IDA
Cu/Mn-IDA (0.9/0.1)
Cu/Mn-IDA (0.7/0.3)
Cu/Mn-IDA (0.5/0.5)
H2O
117–166 °C (14.7%)
220–580 °C (50.6%)
34.7%
135–163 °C (14.7%)
175–500 °C (51.9%)
33.4%
133–190 °C (15.8%)
204–510 °C (52.6%)
31.6%
135–186 °C (15.4%)
201–730 °C (53.7%)
30.9%
Ligand
Residue
6

J.C.D. de Andrade, et al.
InorganicaChimicaActa514(2021)119985
Fig. 8. Proposed catalytic mechanism for M−IDA catalysts.
which favours the approximation of reagents in the transition state.
Although the proposed mechanism seems quite reasonable considering
experimental data, more studies must be carried out in order to confirm
this mechanism in the future.
4. Conclusions
Here, the influence of experimental parameters (pH and counter-
ion) in the synthesis of the 1D-CP [Cu(IDA)(H2O)2]n were investigated
and the best synthetic route was determined. Parameters studied have
an effect only in the yield and reaction time, but not in crystalline phase
obtained. Three isostructural Cu/Mn-IDA CPs were obtained via iso-
morphic replacement of copper ions. Cu/Mn stochiometric ratios were
determined by Rietveld refinement and the single-crystal structures
were solved. Catalytic performance of the Cu-IDA and bimetallic CPs in
Baylis-Hillman reactions were investigated, showing yields up to 91%
and time reactions of 5 h. Results indicate a relationship between ca-
tions ionic radii, Cu/Mn molar ratio into the structure and the catalytic
performance of the coordination polymers. Based on the experimental
evidences, a catalytic mechanism was also proposed.
Since 2014 [35], some CP-structures have been reported as poten-
tial catalysts for Baylis-Hillman reactions [32–37]. The main strategy
used is the functionalization of the structure pores with organic groups
that can act as Lewis bases or Brønsted acids, improving the catalytic
performance. Table 5 shows comparative data of yields and reaction
times for CP-based catalysts already reported in literature, also using 3-
nitrobenzaldehyde as substrate and results indicate the superior activity
of the Cu/Mn-IDA (0.9/0.1). High surface areas can increase catalytic
processes, which certainly justifies the superior number of studies re-
porting porous coordination polymers as catalysts in several organic
reactions including Baylis-Hillman reaction [32–37]. Although the 1D-
CPs studied here do not tend to have appreciable porosity, they still
perform better when compared to high-porosity materials in the lit-
erature (Table 5).
CRediT authorship contribution statement
Some of these CP-based catalysts can act without the presence of
DABCO with satisfactory catalytic activity [34], however, pore func-
tionalization is experimentally expensive in ligand synthesis or post-
synthetic modification in the structure. Thus, these initial studies show
the potentialities of the M−IDA coordination polymers, especially Cu/
Mn-IDA (0.9/0.1), as promising low-cost catalysts with high-perfor-
mance in the Baylis-Hillman reactions.
Julyanna Candido Dutra de Andrade: Conceptualization,
Methodology, Validation, Investigation, Formal analysis. Lucas Araujo
Trajano Silva: Conceptualization, Methodology, Validation,
Investigation, Formal analysis, Writing - original draft. Claudio
Gabriel Lima-Júnior: Conceptualization, Methodology, Validation,
Resources, Visualization, Investigation, Funding acquisition, Writing -
original draft, Formal analysis, Project administration. Jaroslaw
Chojnacki: Methodology, Validation, Investigation, Formal analysis.
Mário Luiz Araújo de Almeida Vasconcelos: Conceptualization,
Funding acquisition, Project administration. Rodolfo Bezerra da Silva:
Methodology, Validation, Investigation, Formal analysis. Severino
Alves Júnior: Conceptualization, Funding acquisition, Project admin-
istration. Fausthon Fred da Silva: Conceptualization, Methodology,
Validation, Resources, Visualization, Investigation, Funding acquisi-
tion, Writing - original draft, Formal analysis, Project administration.
Table 5
Reaction times and yields for Baylis-Hillman reactions catalysed by co-
ordinating polymers, using 3-nitrobenzaldehyde as substrate.
Catalyst
Time (h) Solvent
Yield (%)a Ref.
Cu/Mn-IDA (0.9/0.1)/DABCO
5
DMF
91
This work
L
CuPRO
24
CHCl3/THFb 69
CHCl3/THFc 67
[32]
[33]
[34]
{[Zn2(L)2(azp)]·8DMF·3H2O}n 32
TiO2@UiO-68-CIL
48
MeOHb
56
Declaration of Competing Interest
a
b
c
Yield calculated after the isolated product.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to
reaction conducted with imidazole instead DABCO.
reaction with methyl vinyl ester in absence of DABCO.
7

J.C.D. de Andrade, et al.
InorganicaChimicaActa514(2021)119985
influence the work reported in this paper.
novel 3D oxalate-based coordination polymer {[Cu(bpy)3][Mn2(C2O4)3]·H2O}n,
Dalton Trans. 44 (2015) 20626–20635.
[23] E. Samol’ová, J. Kuchár, V. Grzimek, A. Kliuikov, E. Cizmár, Synthesis, Crystal
structure and magnetic properties of the new Cu(II)/Mn(II) coordination polymer
[{Cu(cyclam)MnCl3(H2O)2}Cl]n, Polyhedron 170 (2019) 51-59.
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Appendix A. Supplementary data
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.ica.2020.119985.
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9