New polynuclear compounds based on N-benzyliminodipropionic acid: solution studies, synthesis, and X-ray crystal structures

Article abstract of DOI:10.1080/00958972.2016.1239086

Three new polynuclear compounds based on a dicarboxylic acid ligand are reported. In particular, two Cu(II) coordination compounds, [Cu₂(H₂O)₆(Hbzlidp)₂](CF₃SO₃)₂·2H₂O (1) and [Cu(NO₃)(Hbzlidp)]_∞ (2) (bzlidp^2??=?N-benzyliminodipropionate anion), and a Ni(II) dinuclear compound, [Ni₂(H₂O)₄(bzlidp)₂] (3), were synthesized and characterized by IR spectroscopy, elemental analysis and single crystal X-ray diffraction. Different structures were obtained depending on the reaction conditions. The structural analyses reveal that 1 was formed by dinuclear [Cu₂(H₂O)₆(Hbzlidp)₂]²⁺ units built by two copper(II) ions joined through two Hbzlidp^? ligands, while 2 was formed by pairs of Cu(II) centers bridged by four syn,syn carboxylate groups to generate “paddle wheel” units. The dinuclear copper units are arranged in a rhombus type grid, in a 2-D layer structure. In both cases, the N was protonated and not coordinated to the metal center. Compound 3 was formed by [Ni₂(H₂O)₄(bzlidp)₂] neutral dinuclear units, with octahedral Ni(II) centers. Solution studies of the ligand–M(II) systems (M(II)?=?Mn, Co, Ni, Cu, Zn, Cd, and Pb) were also carried out.

Full text of DOI:10.1080/00958972.2016.1239086

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
New polynuclear compounds based on N-
benzyliminodipropionic acid: solution studies,
synthesis, and X-ray crystal structures
Emiliano Braña, Delfina Quiñone, Sebastián Martínez, Joaquín Grassi,
Ignacio Carrera, Julia Torres, Javier González-Platas, Gustavo Seoane, Carlos
Kremer & Carolina Mendoza
To cite this article: Emiliano Braña, Delfina Quiñone, Sebastián Martínez, Joaquín Grassi,
Ignacio Carrera, Julia Torres, Javier González-Platas, Gustavo Seoane, Carlos Kremer & Carolina
Mendoza (2016) New polynuclear compounds based on N-benzyliminodipropionic acid:
solution studies, synthesis, and X-ray crystal structures, Journal of Coordination Chemistry,
69:24, 3650-3663, DOI: 10.1080/00958972.2016.1239086
To link to this article: http://dx.doi.org/10.1080/00958972.2016.1239086
Accepted author version posted online: 20
Sep 2016.
Published online: 04 Oct 2016.
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Date: 11 November 2016, At: 05:29

Journal of Coordination Chemistry, 2016
Vol. 69, no. 24, 3650–3663
ꢀꢁꢁp://ꢂx.ꢂꢃꢄ.ꢃꢅg/10.1080/00958972.2016.1239086
New polynuclear compounds based on N-benzyliminodipropionic
acid: solution studies, synthesis, and X-ray crystal structures
a
a
a
b
b
Emiliano Braña , Delfina Quiñone , Sebastián Martínez , Joaquín Grassi , Ignacio Carrera ,
a
c
b
a
Julia Torres , Javier González-Platas , Gustavo Seoane , Carlos Kremer and
Carolina Mendoza
a
ꢆ
Cáꢁꢇꢂꢅꢆ ꢂꢇ Qꢈíꢉꢄcꢆ iꢊꢃꢅgáꢊꢄcꢆ, dꢇpꢆꢅꢁꢆꢉꢇꢊꢁꢃ eꢋꢁꢅꢇꢌꢌꢆ Cꢆꢉpꢃꢋ, fꢆcꢈꢌꢁꢆꢂ ꢂꢇ Qꢈíꢉꢄcꢆ, uꢊꢄvꢇꢅꢋꢄꢂꢆꢂ ꢂꢇ ꢌꢆ rꢇpúbꢌꢄcꢆ,
b
mꢃꢊꢁꢇvꢄꢂꢇꢃ, uꢅꢈgꢈꢆꢍ; lꢆbꢃꢅꢆꢁꢃꢅꢄꢃ ꢂꢇ síꢊꢁꢇꢋꢄꢋ oꢅgáꢊꢄcꢆ, dꢇpꢆꢅꢁꢆꢉꢇꢊꢁꢃ ꢂꢇ Qꢈíꢉꢄcꢆ oꢅgáꢊꢄcꢆ, fꢆcꢈꢌꢁꢆꢂ ꢂꢇ Qꢈíꢉꢄcꢆ,
uꢊꢄvꢇꢅꢋꢄꢂꢆꢂ ꢂꢇ ꢌꢆ rꢇpúbꢌꢄcꢆ, mꢃꢊꢁꢇvꢄꢂꢇꢃ, uꢅꢈgꢈꢆꢍ; dꢇpꢆꢅꢁꢆꢉꢇꢊꢁꢃ ꢂꢇ fíꢋꢄcꢆ, sꢇꢅvꢄcꢄꢃ ꢂꢇ dꢄꢎꢅꢆccꢄóꢊ ꢂꢇ rꢆꢍꢃꢋ X,
c
uꢊꢄvꢇꢅꢋꢄꢂꢆꢂ ꢂꢇ lꢆ lꢆgꢈꢊꢆ, tꢇꢊꢇꢅꢄꢎꢇ, spꢆꢄꢊ
ABSTRACT
ARTICLE HISTORY
Three new polynuclear compounds based on a dicarboxylic acid
ligand are reported. In particular, two Cu(II) coordination compounds,
rꢇcꢇꢄvꢇꢂ 8 apꢅꢄꢌ 2016
accꢇpꢁꢇꢂ 9 aꢈgꢈꢋꢁ 2016
[
Cu (H O) (Hbzlidp) ](CF SO ) ·2H O (1) and [Cu(NO )(Hbzlidp)]∞ (2)
2 2 6 2 3 3 2 2 3
2−
KEYWORDS
(
bzlidp = N-benzyliminodipropionate anion), and a Ni(II) dinuclear
Pꢃꢌꢍꢊꢈcꢌꢇꢆꢅ cꢃꢉpꢌꢇxꢇꢋ;
Cꢈ(ii); nꢄ(ii); X-ꢅꢆꢍ
cꢅꢍꢋꢁꢆꢌ ꢋꢁꢅꢈcꢁꢈꢅꢇꢋ; N-
Bꢇꢊzꢍꢌꢄꢉꢄꢊꢃꢂꢄpꢅꢃpꢄꢃꢊꢆꢁꢇ;
flꢇxꢄbꢌꢇ ꢌꢄgꢆꢊꢂ; ꢋꢃꢌꢈꢁꢄꢃꢊ
ꢋꢁꢈꢂꢄꢇꢋ
compound, [Ni (H O) (bzlidp) ] (3), were synthesized and characterized by IR
2
2
4
2
spectroscopy, elemental analysis and single crystal X-ray diffraction. Different
structureswereobtaineddependingonthereactionconditions.Thestructural
2
+
analyses reveal that 1 was formed by dinuclear [Cu (H O) (Hbzlidp) ] units
2
2
6
2
−
built by two copper(II) ions joined through two Hbzlidp ligands, while 2
was formed by pairs of Cu(II) centers bridged by four syn,syn carboxylate
groups to generate “paddle wheel” units. The dinuclear copper units are
arranged in a rhombus type grid, in a 2-D layer structure. In both cases, the
N was protonated and not coordinated to the metal center. Compound 3
was formed by [Ni (H O) (bzlidp) ] neutral dinuclear units, with octahedral
2
2
4
2
Ni(II) centers. Solution studies of the ligand–M(II) systems (M(II) = Mn, Co,
Ni, Cu, Zn, Cd, and Pb) were also carried out.
1. Introduction
Coordination polymers are infinite crystalline lattices composed of inorganic nodes (metal ions or clus-
ters) connected by organic polytopic ligands that act as linkers [1]. Solid-state materials with different
CONTACT Cꢆꢅꢃꢌꢄꢊꢆ mꢇꢊꢂꢃzꢆ
cꢉꢇꢊꢂꢃzꢆ@ꢎq.ꢇꢂꢈ.ꢈꢍ
sꢈppꢌꢇꢉꢇꢊꢁꢆꢌ ꢂꢆꢁꢆ ꢎꢃꢅ ꢁꢀꢄꢋ ꢆꢅꢁꢄcꢌꢇ cꢆꢊ bꢇ ꢆccꢇꢋꢋꢇꢂ ꢆꢁ ꢀꢁꢁp://ꢂx.ꢂꢃꢄ.ꢃꢅg/10.1080/00958972.2016.1239086.
©
2016 iꢊꢎꢃꢅꢉꢆ uK lꢄꢉꢄꢁꢇꢂ, ꢁꢅꢆꢂꢄꢊg ꢆꢋ tꢆꢍꢌꢃꢅ & fꢅꢆꢊcꢄꢋ Gꢅꢃꢈp

JOꢀRNꢁꢂ OF COORDINꢁTION CHEMISTRꢃ
3651
architectures, linear, bi- or tri-dimensional arrays, are formed by a self-assembly process [2]. The design
and preparation of coordination polymers is of current interest due to their promising applications in gas
storage, catalysis, drug delivery, magnetochemistry, or supramolecular chemistry [1, 3–8]. Initially, rigid,
highly directional ligands were used to connect the metal ions, an approach of choice if specific crystal
motifs are desired [9]. Recently, the use of flexible ligands in the synthesis of coordination polymers has
caught the attention of several groups [10–18]. Examples of flexible ligands employed in the preparation
of coordination polymers are dicarboxylic acid compounds such as 1,4-cyclohexanedicarboxylic acid
(
H chdc) [19] or 1,4-phenylenediacetic acid (H pda) [20], dipyridine derivatives such as 1,2-bis(4-pyridyl)
2
2
ethane (bpe) [21] or tricarboxylic acids such as nitrilotriacetic acid (H nta) [22] and nitrilotripropionic
3
acid (H ntp) [23]. In these ligands, the flexibility is due to the rotation of the single bonded carbon
3
chains [22]. The existence of different conformations may lead to different final structures [12]. The use
of flexible ligands is of interest because flexibility is essential in the design of molecular devices whose
functionality is based on conformational changes. The breathing ability of certain solid-state polymers
or the possibility of adaptive recognition of guests are good examples [4, 24, 25].
In comparison to rigid connectors, the use of flexible ligands to build coordination polymers is
more difficult [12]. The reasons for this include: (a) the ligand can adopt different conformations which
are difficult to control, making the design of polymers complicated; (b) the self-assembly process is
sensitive to many factors related to the reaction conditions, in particular the metal ion, the reactant
concentration, and the solution pH; and finally, (c) flexible ligands can also act as polydentate ligands
forming mononuclear entities, a competitive process that should be avoided.
Polycarboxylate ligands are frequently selected as flexible organic linkers in the construction of
metal clusters, because they show different coordination modes, resulting from completely or partially
deprotonated sites, allowing for various structural topologies [26]. They can act as terminal unidentate,
chelating, bridging bidentate, or bridging tridentate ligands [27]. They also present the ability to act as
hydrogen bond acceptors to assemble supramolecular structures [28].
We are interested in the design of coordination polymers using flexible polytopic ligands. In previous
work, we reported the preparation of polymers [ꢂn(Hida) ]·xH O (ꢂn = lanthanide ion; H ida = imi-
3
2
2
nodiacetic acid) [29]. ꢁlthough this is a typical tridentate ligand, if the synthesis is performed under
−
acidic conditions, nitrogen protonation occurs, and Hida becomes a ditopic flexible ligand. It is able
to build polymeric complexes, which exhibit, in the solid state, large hexagonal channels with more
than 11 Å diameters. We also reported the preparation and X-ray crystal structure of trinuclear cop-
3−
per(II) complexes with nitrilotripropionate (ntp ), working at acidic pH values. The structure of the
polynuclear complexes shows the presence of well-defined capsules formed by three Cu(II) cations and
two protonated Hntp2− ligands in a tritopic arrangement. The counter ion of the copper salt used in
the preparation influences the final structure by changing the connection between the capsules [30].
With these examples in mind, we started study of iminodipropionic acid derivatives, in particular
N-benzyliminodipropionic acid (H bzlidp, figure 1) as flexible ligand to connect metal ions. H bzlidp is a
2
2
dicarboxylic acid that has been scarcely studied as a ligand in coordination chemistry. To our knowledge,
the three compounds reported here are the first examples of polynuclear complexes containing this
Figure 1. sꢁꢅꢈcꢁꢈꢅꢇ ꢃꢎ N-bꢇꢊzꢍꢌꢄꢉꢄꢊꢃꢂꢄpꢅꢃpꢄꢃꢊꢄc ꢆcꢄꢂ (h bzꢌꢄꢂp).
2

3652
E. BRꢁꢄꢁ ET ꢁꢂ.
ligand. H bzlidp was prepared based on a slight modification of a previously reported protocol for the
2
synthesis of the N-methyliminodipropionic acid (H midp) [31]. The authors reported the preparation of a
2
Cu(II) compound ([Cu(H O)midp]·H O) where the coordination geometry of each Cu ion can be described
2
2
2
−
as a slightly distorted square pyramid and the midp is a tetradentate bridging ligand resulting in
infinite chains, which extend along [010]. Other related iminodipropionic ligands have been employed in
the preparation of Cu(II) mononuclear coordination compounds. For instance, with the o-anisidine-N,N-
2−
di-3-propionate anion (o-ꢁndp ) a mononuclear compound, [Cu(o-ꢁndp)(H O) ]·2H O, was obtained
2
2
2
where the Cu coordination polyhedron is a distorted tetragonal bipyramid (4 + 2) and the ligand is a
2
−
tetradentate chelator, forming three chelate rings [32]. With p-toluidine-N,N-di-3-propionate (p-Tdp )
2−
2−
2−
and aniline-N,N-di-3-propionate (ꢁdp ), mononuclear complexes [Cuꢂ(H O) ] (ꢂ = p-Tdp or ꢁdp )
2
2
were prepared and show a square pyramid Cu coordination polyhedron with the ligand as tridentate
chelator. However, no polynuclear species were reported with these ligands [33, 34].
2
. Experimental
.1. General information
ll common laboratory chemicals were reagent grade, purchased from commercial sources and used
without purification. Infrared spectra, as KBr pellets, were obtained from a FTIR Shimadzu IR-Prestige-21
2
ꢁ
−1
spectrophotometer from 4000 to 400 cm . Elemental analyses (C, H, N, and S) were performed on a
Flash 2000 instrument. NMR spectra were obtained on a Bruker ꢁvance DPX-400 instrument. Proton
chemical shifts (δ) are reported in ppm downfield from TMS as an internal reference. Thermogravimetric
analyses (TGꢁ) were performed in a Shimadzu TGꢁ-50 instrument with a Tꢁ 50 I interface using plati-
−1
num cells. TGꢁ results were recorded under a nitrogen stream (50 mꢂ min ) and with a heating rate of
.0 °C min− from 18 to 300 °C and 30 °C min from 300 to 700 °C.
1
−1
1
For solution studies, MnCl ·4H O (98%, Merck), CoCl ·6H O (98%, Carlo Erba), NiCl ·6H O (98%, Merck),
2
2
2
2
2
2
CuCl ·2H O (99.2%, Baker), ZnCl (98%, Sigma ꢁldrich), CdCl (99%, Fluka), and Pb(NO ) (99%, Sigma
2
2
2
2
3 2
ꢁldrich) were used as metal cation sources. The standard HCl and NaOH solutions were prepared by
diluting Merck standard ampoules. Me NCl solutions were prepared from Me NCl (98% from Fluka). ꢁcid
4
4
and base stock solutions were standardized against sodium borate and potassium hydrogen phthalate,
−1
respectively. ꢁll solutions were prepared with analytical grade water (18 μS cm ) and were freed of
carbon dioxide by bubbling with argon.
2
.2. Equilibrium studies
The protonation constants of bzlidp2− were determined through four potentiometric titrations (ca.
−
1
1
00–150 experimental points each) in the concentration range 1–4 mmol ꢂ . Then, the behavior of the
ligand in the presence of metal cations M(II) (M = Mn, Co, Ni, Cu, Zn, Cd, and Pb) was analyzed through
at least six potentiometric titrations (ca. 100–150 experimental points each) for each system, at metal
−1
cation concentrations ranging from 1 to 3 mmol ꢂ , and ligand to metal cation total molar ratios varying
from 5:1 to 1:2. The pH interval from 2 to the pH where solid formation was evidenced was covered
(
pH value for the solid formation was always higher than six). In those cases, the formation of solid
M(II) hydroxide was consistent with previous reports on metal hydroxide solubilities [35]. The forma-
tion constants of soluble hydroxo species of M(II) were also determined analogously under the same
experimental conditions. Four titrations of M(II) solutions (ca. 80 experimental points each) were carried
−1
out in the concentration interval 1–3 mmol ꢂ . The obtained values for these hydrolysis constants
were taken into account in the Hyperquad input for the subsequent formation constants calculation.
In each potentiometric experiment, the solutions were poured into a 50 mꢂ titration cell. ꢁfter
thermal equilibrium was reached, hydrogen ion concentrations were determined by successive read-
ings, each performed after a small incremental addition of standard 0.1 mol ꢂ− NaOH solution. The
titrant addition and e.m.f. measurements were carried out using an automatic titrator, Mettler–Toledo
1

JOꢀRNꢁꢂ OF COORDINꢁTION CHEMISTRꢃ
3653
Dꢂ50-Graphix. The ionic strength was kept almost constant throughout the titrations by using solutions
containing 0.50 mol ꢂ−1 Me NCl and relatively low initial concentrations of metal ions and bzlidp (the
4
sum of these reactants initial concentrations did not contribute more than 2% to the total ionic strength).
Pre-saturated argon (free of CO ) was bubbled through the solutions during titrations to eliminate the
2
effect of atmospheric carbon dioxide, and the temperature was kept at 20.0 (±0.1) °C. Equilibrium attain-
ment after each titrant addition was verified by controlling the deviation of successive e.m.f. readings.
Independent stock solutions were used in some titrations to check reproducibility. The cell electrode
potential E° and the acidic junction potential were determined according to reported procedure [36]
from independent titrations of the strong acid with the titrant solution. In this way, the pH scale was
the free hydrogen concentration scale. The calibration in the alkaline range was checked by recalcu-
lating K values for each system. The obtained values (average log K = −13.90) were always checked
w
10
w
to assure they were in line with previously reported data under similar experimental conditions [35].
Data were analyzed using the HꢃPERQꢀꢁD program [37], and species distribution diagrams were
produced using the HySS program [38]. The fit of the values predicted by the model to the experimental
data was estimated on the basis of the σ parameter, corresponding to the scaled sum of squared dif-
ferences between predicted and experimental values. Many other possible stoichiometries were tried
for each system, and final models were selected on the basis of the σ parameter, the model confidence
level estimator, Chi squared, and the internal consistency of data reflected in standard deviations of
the formation constants [37].
2
.3. Synthesis of N-benzyliminodipropionic acid (H bzlidp)
2
N-benzyliminodipropionic acid (H bzlidp) was prepared based on a slight modification of a previously
2
−1
reported protocol [31]. ꢁcrylic acid (31.7 g, 0.44 mol) was added to 20 mꢂ of an 8 mol ꢂ solution of
benzylamine in dry ethanol (17.1 g, 0.16 mol). The mixture was heated overnight at boiling. The product
precipitated as a white solid which was filtered and washed with cold ethanol (32.97 g, 0.13 mol, 82%.
yield). H NMR (400 Hz, DMSO-d , δ, ppm): 7.36–7.31 (m, 5H), 3.62 (s, 2H) 2.71 (t, J = 2.7 Hz, 4H), 2.41 (t,
J = 2.4 Hz, 4H); C NMR (100 Hz) 174.0, 139.4, 129.1, 129.1, 128.6, 128.6, 127.4, 57.5, 48.9, 32.1. Selected
1
6
1
3
−
1
IR data (vmax/cm ): 3017, 3003, 2765, 1701, 1396, 1223, 1095; ꢁnal. Calcd for C H NO (%): C, 62.14; H,
13
17
4
6
.82; N, 5.57. Found: C, 61.60; H, 7.13; N, 5.88.
2
.4 Synthesis of the complexes
2
.4.1. Synthesis of bis-(μ-hydrogen-N-benzyliminodipropionato-κO, κO)bis[triaquacopper(II)]
ditrifluoromethanesulfonate dihydrate [Cu (H O) (Hbzlidp) ](CF SO ) ·2H O (1)
2
2
6
2
3
3 2
2
H bzlidp (0.626 g, 1.17 mmol) and copper trifluoromethanesulfonate (0.307 g, 0.85 mmol) were dissolved
2
in 10 mꢂ of distilled water by addition of 1 M NaOH solution to pH 3. The blue solution was filtered
and the solvent was slowly evaporated at room temperature. ꢁfter a few days, blue crystals appeared
and were separated by filtration, washed with water and allowed to dry in the open air. In this manner,
0
.243 g of blue crystals were obtained. ꢃield 53% (based on copper trifluoromethanesulfonate). ꢁnal.
Calcd for C H CuNO F S (%): C, 31.43; H, 4.52; N, 2.62; S, 5.99. Found: C, 31.65; H, 4.54; N, 1.84; S, 6.65.
1
4
24
11 3
−1
Selected IR data (vmax/cm ): 3470, 3385, 3129, 1597, 1447, 1421, 1375, 1330, 1261, 1180, 1031, 745, 638.
TGꢁ (18–700 °C, N ) % weight loss: 10.9 (left limit 18 °C–right limit 100 °C), 32.6 (left limit 100 °C–right
2
limit 285 °C), 28.5 (left limit 285 °C–right limit 700 °C).
2
.4.2. Synthesis of catena-poly[nitratocopper(II)-μ-(hydrogen-N-benzyliminodipropionato-(κO,
(
κO′)] [Cu(NO )(Hbzlidp)] (2)
3 ∞
H bzlidp (0.626 g, 1.17 mmol) and copper nitrate trihydrate (0.411 g, 1.7 mmol) were dissolved in 10 mꢂ
2
distilled water by addition of 5 M NaOH solution to pH 3.0. The solvent was slowly evaporated at room
temperature. ꢁfter a few days, a green-blue solid appeared that was separated by filtration, washed
with a few drops of water and allowed to dry in the open air (0.288 g). ꢃield 65% (based on H bzlidp).
2

3654
E. BRꢁꢄꢁ ET ꢁꢂ.
Table 1. Cꢅꢍꢋꢁꢆꢌꢌꢃgꢅꢆpꢀꢄc ꢂꢆꢁꢆ ꢎꢃꢅ 1ꢏ3.
1
2
3
eꢉpꢄꢅꢄcꢆꢌ ꢎꢃꢅꢉꢈꢌꢆ
fꢃꢅꢉꢈꢌꢆ wꢇꢄgꢀꢁ
T (K)
Cꢅꢍꢋꢁꢆꢌ ꢋꢍꢋꢁꢇꢉ
spꢆcꢇ gꢅꢃꢈp
a (Å)
b (Å)
c (Å)
α (°)
β (°)
C h Cꢈno f s
C h Cꢈn o
C h nnꢄo
344.00
150(1)
1
4
24
11
3
13 16
2
7
13 19
6
534.94
200(1)
tꢅꢄcꢌꢄꢊꢄc
P −1
7.3233(3)
9.8634(4)
15.2034(7)
89.815 (4)
86.776(4)
88.033(4)
1095.80(8)
2
375.82
293(2)
mꢃꢊꢃcꢌꢄꢊꢄc
mꢃꢊꢃcꢌꢄꢊꢄc
P 2 /n
P 2 /c
1
1
9.2620(2)
11.2106(3)
14.5082(3)
90
90.298(2)
90
1506.40(6)
4
1.657
12.0502(5)
6.8629(3)
17.7884(7)
90
93.019(4)
90
1469.04(11)
4
1.555
γ (°)
V (Å )
3
Z
−3
DCꢆꢌcꢂ (g cꢉ )
1.621
3.053
550
−1
μ (Cꢈ Kα) (ꢉꢉ )
2.423
772
2.161
720
F (0 0 0)
Cꢅꢍꢋꢁꢆꢌ ꢂꢄꢉꢇꢊꢋꢄꢃꢊꢋ (ꢉꢉ)
0.286 × 0.191 × 0.147
8.97ꢏ134.16
0.090 × 0.062 × 0.053
9.972ꢏ134.12
−11 ≤ h ≤ 11
−13 ≤ k ≤ 13
−17 ≤ l ≤ 15
6220/2685/0.0183
2685/0/212
0.176 × 0.120 × 0.0940
7.346ꢏ134.146
−12 ≤ h ≤ 14
−5 ≤ k ≤ 8
−21 ≤ l ≤ 16
5071/2613/0.0204
2613/0/206
0.0289/0.0816
1.03
2
θ ꢅꢆꢊgꢇ ꢎꢃꢅ ꢂꢆꢁꢆ cꢃꢌꢌꢇcꢁꢄꢃꢊ (°)
lꢄꢉꢄꢁꢄꢊg ꢄꢊꢂꢄcꢇꢋ
−8 ≤ h ≤ 8
−
11 ≤ k ≤ 9
−
13 ≤ l ≤ 18
rꢇflꢇcꢁꢄꢃꢊꢋ (cꢃꢌꢌꢇcꢁꢇꢂ/ꢈꢊꢄqꢈꢇ, (rꢄꢊꢁ))
dꢆꢁꢆ/ꢅꢇꢋꢁꢅꢆꢄꢊꢁꢋ/pꢆꢅꢆꢉꢇꢁꢇꢅꢋ
7192/3902/0.0205
3902/0/297
0.0355/0.0915
1.04
ꢆ
2
2 b
R , wR [F > 2σ(F )]
0.0282/0.0736
1.06
0.41/−0.26
1
2
2
Gꢃꢃꢂꢊꢇꢋꢋ-ꢃꢎ-fiꢁ ꢃꢊ F
−3
lꢆꢅgꢇꢋꢁ ꢂꢄff. pꢇꢆk ꢆꢊꢂ ꢀꢃꢌꢇ (ꢇ Å )
CCdC
0.51/−0.45
1454769
0.38/−0.38
1454771
1454770
ꢆ
R = Σ||F | − |F ||/Σ|F |. wR = (Σ[w(F − F ) ]/Σ[w(F 2)2)1/2.
b
2
2 2
1
0
c
c
2
0
c
0
Green-blue crystals adequate for X-ray analysis were obtained from a water solution of the product by
slow diffusion of acetonitrile. ꢁnal. Calcd for C H CuN O (%): C, 41.55; H, 4.29; N, 7.45. Found: C, 41.52;
1
3
16
2
7
−
1
H, 4.70; N, 7.28. Selected IR data (vmax/cm ): 3073, 3009, 2961, 2895, 1636, 1416, 1373, 1360, 1321, 1227,
047, 702. TGꢁ (18–700 °C, 1.0 °C min , N ) % weight loss: 59.5 (left limit 100 °C–right limit 280 °C), 8.39
−1
1
2
(
left limit 280 °C–right limit 520 °C).
.4.3. Synthesis of bis(μ-benzyliminodipropionato)tetraaquadinickel(II) [Ni (H O) (bzlidp) ] (3)
2
2
2
4
2
H bzlidp (0.125 g, 0.5 mmol) and nickel acetate tetrahydrate (0.125 g, 0.5 mmol) were dissolved in
2
1
0 mꢂ distilled water at 80 °C. The pH was set to 4.2 by addition of 1 M NaOH solution. ꢁ 5 mꢂ portion
of this pale green solution was allowed to crystallize by slow diffusion of acetone vapors. ꢁfter five
days, pale green crystals were obtained from the acetone diffusion (12.3 mg). ꢃield 14%. ꢁnal. Calcd
for C H NNiO (%): C, 45.39; H, 5.57; N, 4.07. Found: C, 45.09; H, 5.79; N, 3.95. Selected IR data (vmax/
1
3
19
6
−
1
cm ): 3264, 3030, 2965, 2880, 1578, 1416, 1383, 1114, 894.
2
.5. X-ray crystallography
The X-ray diffraction data for all compounds were collected with an ꢁgilent SuperNOVꢁ diffractometer
with microfocus X-ray using Cu Kα radiation (λ = 1.54184 Å). CrysꢁlisPro [39] software was used to collect,
index, scale, and apply analytical absorption correction based on the faces of the crystal. The structure
was solved by a dual-space algorithm using the SHEꢂXT program [40]. Fourier recycling and least-
squares refinement were used for the model completion with SHEꢂXꢂ-2014 [41–43]. ꢁll non-hydrogen
atoms have been refined anisotropically and all hydrogens have been placed in geometrically suitable
positions and refined as riding with isotropic thermal parameters related to the equivalent isotropic
thermal parameter of the parent. Hydrogens were geometrically positioned with C–H = 0.93 Å and
ꢀiso(H) = 1.2 ꢀeq(C), except for hydrogens on N in 1 and 2 that were determined by Fourier differences

JOꢀRNꢁꢂ OF COORDINꢁTION CHEMISTRꢃ
3655
and refined freely. ꢁlso hydrogens from water molecules of 3 and one water molecule of compound 1
could be localized in this form and refined.
Crystal data, collection procedures, and refinement results are summarized in table 1.
3
. Results and discussion
.1. Solution studies
Values for the protonation equilibrium constants of bzlidp2− were required to study the metal com-
3
−1
H
plexation reactions. The obtained results at 20.0 °C in 0.50 mol ꢂ Me NCl are: log K = 8.856(3); log
4
1
H
H
ꢀ2
= 12.789(5); log ꢀ3 = 15.624(7); σ = 0.2. The titration curves of H bzlidp with base have three equivalent
2
points, the third one corresponding to the presence of the N-connecting atom. No previous reports
are available for comparison [35]. The first protonation constant shows lower basic character than that
reported for iminodipropionato ligand, due to the presence of the benzyl substituent on nitrogen, an
electron-withdrawing group [44]. N-benzyliminodiacetate also shows the same behavior. In fact, its first
H
protonation constant has a very similar value to that of bzlidp: log K = 8.87 at 25 °C and 0.1 M ionic
1
strength [35]. ꢁlso in line with previous reports, the protonation constants of the propionic carboxylate
groups in bzlidp are higher than those of the iminodiacetato ligand or N-benzyliminodiacetato, due to
2
−
the presence of longer chains. [45] These facts mean that, both for bzlidp and benzyliminodiacetate,
the amino group is expected to be predominantly protonated in aqueous solution below pH 8.8.
The following step was the study of the M(II)–bzlidp interaction. The divalent cations used for this
study were Mn, Co, Ni, Cu, Zn, Cd, and Pb, and the results are shown in table 2. Stability of complexes
containing 3d metal ions follows the Irving-Williams trend. The species detected were in all cases [Mꢂ]
+
2−
and [M(Hꢂ)] (ꢂ = bzlidp ). Complex species [Mꢂ] (Co, Ni, Cu) had been reported for various dipropionic
acid ligands [31, 44, 46]. In this work, we have additionally detected the protonated species, with a
stability constant value that is fairly independent of the identity of the metal ion.
Figure 2 shows the speciation diagrams for the copper and nickel containing systems. It is important
to note that protonated species are not predominant, but they are formed for pH values around 4. The
speciation diagrams for the rest of the metal ions that were analyzed can be found in the Supporting
Information, figures S1–S5.
3
.2. Synthesis of the complexes
The copper complexes were prepared by direct reaction of copper salts with H bzlidp in aqueous
2
solution at pH 3.0–4.0 and in different ligand to metal molar ratios. ꢁccording to the solution studies,
−
this pH, where the predominant form of the ligand is Hꢂ , should be adequate to favor formation of
+
complexes bearing the monoprotonated form of the ligand. [Cu(Hbzlidp)] was detected in this pH
interval. The nickel complex was prepared by reaction of nickel acetate with H bzlidp in a 1:1 metal
2
to ligand molar ratio, in aqueous solution at pH 4.2, followed by diffusion of acetone. Even though at
+
this acidic pH the species [Ni(Hꢂ)] is expected to be present, 3 was the only product obtained by this
synthetic procedure.
Table 2. ovꢇꢅꢆꢌꢌ ꢎꢃꢅꢉꢆꢁꢄꢃꢊ cꢃꢊꢋꢁꢆꢊꢁꢋ ꢎꢃꢅ m(ii)ꢏbzꢌꢄꢂp cꢃꢉpꢌꢇxꢇꢋ ꢂꢇꢁꢇꢅꢉꢄꢊꢇꢂ ꢆꢁ 20.0 °C ꢄꢊ 0.50 ꢉꢃꢌ l−1 mꢇ nCꢌ.
4
log K1
log β111
σ
mꢊ
Cꢃ
nꢄ
Cꢈ
Zꢊ
Cꢂ
Pb
2.42(2)
2.28(5)
2.76(2)
6.49(1)
10.26(4)
10.33(3)
10.43(2)
10.74(4)
10.61(1)
10.15(3)
10.86(1)
0.3
0.2
0.2
0.4
0.1
0.2
0.2

3656
E. BRꢁꢄꢁ ET ꢁꢂ.
−
1
2+
−1
Figure 2. spꢇcꢄꢇꢋ ꢂꢄꢋꢁꢅꢄbꢈꢁꢄꢃꢊ ꢂꢄꢆgꢅꢆꢉ ꢃꢎ ꢁꢀꢇ m(ii)ꢏbzꢌꢄꢂp ꢋꢍꢋꢁꢇꢉ ꢄꢊ 0.50 ꢉꢃꢌ l mꢇ nCꢌ ꢆꢁ 20.0 °C (ꢁꢃꢁꢆꢌ [m ] = 5 ꢉꢉꢃꢌ l ꢆꢊꢂ
4
−1
2−
ꢁ
ꢃꢁꢆꢌ [bzꢌꢄꢂp] = 5 ꢉꢉꢃꢌ l ). tꢀꢇ ꢎꢈꢌꢌꢍ ꢂꢇpꢅꢃꢁꢃꢊꢆꢁꢇꢂ ꢌꢄgꢆꢊꢂ ꢄꢋ ꢅꢇpꢅꢇꢋꢇꢊꢁꢇꢂ ꢆꢋ l . (ꢆ) m = Cꢈ; (b) m = nꢄ.
The crystalline solids were characterized by elemental analysis and infrared (IR) spectroscopy. IR
−1
spectra of 1 and 3 show broad bands at 2800–3600 cm , which suggests the presence of water in the
structures. This signal is absent in 2. The three complexes exhibit bands at 2800–2970 cm− that corre-
1
spond to the vC–H vibrations of the –CH – groups in the carbon chains on bzlidp ligands. The absence of
2
−
1
the characteristic absorption of v (COOH) near 1700 cm indicates that carboxylate groups of the ligand
are not fully protonated in the complexes. The v (COO ) vibrations occurred at ca. 1600 cm , while
those of v (COO ) appeared at ca. 1420 cm . The large difference in the v –v values (around 180 cm )
as
−
−1
as
−
−1
−1
s
as
s
excludes the presence of chelating bidentate coordination modes of the ligand [47]. The bands at 1261,
1
031, and 638 cm−1 account for the presence of theCF SO in 1 [48]. The coordinatedNO3 in 2 has bands
−
−
3
3
−1
at 1416 and 1321 cm which correspond to the asymmetric and symmetric stretching vibrations in a
monodentate coordination mode [49]. The TGꢁ curves for 1 and 2 show a decomposition process that
begins about 200 °C. For 1, a dehydration process (with a weight loss of 10.9%) is shown below 100 °C.
3
.3. Crystal structures
It was possible to obtain single crystals for 1 by slow evaporation of the solvent at room temperature,
while crystals of 2 and 3 were obtained by slow diffusion of acetonitrile or acetone, respectively.

JOꢀRNꢁꢂ OF COORDINꢁTION CHEMISTRꢃ
3657
Table 3. sꢇꢌꢇcꢁꢇꢂ bꢃꢊꢂ ꢂꢄꢋꢁꢆꢊcꢇꢋ (Å) ꢆꢊꢂ ꢆꢊgꢌꢇꢋ (°) ꢎꢃꢅ 1ꢏ3.ꢆ
Compound 1
Compound 2
Compound 3
Distances
Cꢈ1‒o1
1.9743(15)
1.9928(14)
1.9321(15)
2.2572(19)
1.9172(19)
Cꢈ1‒o1
#2
1.9588(15)
1.9630(15)
1.9616(13)
2.1429(16)
1.9765(13)
1.239(2)
nꢄ1‒o1
nꢄ1‒o3
2.0527(11)
#
1
Cꢈ1‒o3
Cꢈ1‒o2
Cꢈ1‒o3
2.0003(12)
2.0837(12)
2.0600(12)
2.1336(11)
2.1003(13)
#3
Cꢈ1‒o1W
Cꢈ1‒o2W
Cꢈ1‒o3W
nꢄ1‒o1W
nꢄ1‒o2W
Cꢈ1‒o5
#4
#5
Cꢈ1‒o4
nꢄ1‒o1
o5‒n2
nꢄ1‒n1
Angles
#
1
o3 ‒Cꢈ1‒o2W
94.80(7)
170.45(7)
94.29(7)
86.81(6)
90.14(7)
91.79(8)
93.28(7)
88.67(7)
96.04(10)
173.13(10)
o1‒Cꢈ1‒o5
93.97(9)
99.03(9)
166.90(7)
87.98(7)
89.65(7)
104.15(6)
88.73(7)
166.82(6)
89.03(6)
90.65(7)
o1 W‒nꢄ1‒o2 W
o1W‒nꢄ1‒o1
o1W‒nꢄ1‒n1
90.50(5)
84.05(5)
97.88(5)
84.54(5)
89.54(5)
94.32(5)
92.23(5)
168.40(5)
84.88(5)
169.87(5)
94.43(5)
80.57(5)
94.77(5)
90.44(5)
174.22(5)
#
1
#2
o1‒Cꢈ1‒o3
o2 ‒Cꢈ1‒o5
#2
o1‒Cꢈ1‒o2W
o1W‒Cꢈ1‒o3
o1W‒Cꢈ1‒o1
o2 ‒Cꢈ1‒o1
#
1
#2
#4
#5
o2 ‒Cꢈ1‒o4
o1W‒nꢄ1‒o1
#2
#3
o2 ‒Cꢈ1‒o3
o3‒nꢄ1‒o1
o3‒nꢄ1‒o2W
o3‒nꢄ1‒n1
#3
o1W‒Cꢈ1‒o2W
o3 ‒Cꢈ1‒o5
#
1
#3
o3W‒Cꢈ1‒o3
o3W‒Cꢈ1‒o1
o3 ‒Cꢈ1‒o1
#3
#4
o3 ‒Cꢈ1‒o4
o3‒nꢄ1‒o1W
#4
#5
o3W‒Cꢈ1‒o2W
o3W‒Cꢈ1‒o1W
o4 ‒Cꢈ1‒o5
o3‒nꢄ1‒o1
#4
o4 ‒Cꢈ1‒o1
o1‒nꢄ1‒o2W
o1‒nꢄ1‒n1
#
5
o1‒nꢄ1‒o1
o2W‒nꢄ1‒n1
#
5
o2W‒nꢄ1‒o1
#
5
n1‒nꢄ1‒o1
ꢆsꢍꢉꢉꢇꢁꢅꢍ cꢃꢂꢇꢋ ꢎꢃꢅ #1 = 1 − x, −y, 1 − z; #2 = −x, 1 − y, 1 − z; #3 = 1/2 − x, −1/2 + y, 3/2 − z; #4 = −1/2 + x, 3/2 − y, −1/2 + z;
5 = 2 − x, 1 − y, 1 − z.
#
2
+
Figure 3. mꢃꢌꢇcꢈꢌꢆꢅ ꢋꢁꢅꢈcꢁꢈꢅꢇ ꢃꢎ 1, ꢋꢀꢃwꢄꢊg [Cꢈ (h o) (hbzꢌꢄꢂp) ] , wꢄꢁꢀ ꢌꢆbꢇꢌꢄꢊg. tꢀꢇꢅꢉꢆꢌ ꢇꢌꢌꢄpꢋꢃꢄꢂꢋ ꢆꢅꢇ ꢋꢀꢃwꢊ ꢆꢁ 50% pꢅꢃbꢆbꢄꢌꢄꢁꢍ.
2
2
6
2
hꢍꢂꢅꢃgꢇꢊꢋ ꢆꢅꢇ ꢃꢉꢄꢁꢁꢇꢂ ꢎꢃꢅ cꢌꢆꢅꢄꢁꢍ. Cꢃꢌꢃꢅ cꢃꢂꢇ: cꢃppꢇꢅ, ꢃꢅꢆꢊgꢇ; ꢃxꢍgꢇꢊ, ꢅꢇꢂ; ꢊꢄꢁꢅꢃgꢇꢊ, bꢌꢈꢇ; cꢆꢅbꢃꢊ, gꢅꢆꢍ; ꢋꢈꢌꢎꢈꢅ, ꢍꢇꢌꢌꢃw; flꢈꢃꢅꢄꢊꢇ, gꢅꢇꢇꢊ.
Table 4. sꢇꢌꢇcꢁꢇꢂ bꢃꢊꢂ ꢌꢇꢊgꢁꢀꢋ (Å) ꢆꢊꢂ ꢆꢊgꢌꢇꢋ (°) ꢃꢎ ꢀꢍꢂꢅꢃgꢇꢊ bꢃꢊꢂꢋ ꢄꢊ 1.ꢆ
D–H⋯ꢁ
D–H (Å)
H⋯ꢁ (Å)
D⋯ꢁ (Å)
D–H⋯ꢁ (°)
n1h1⋯o2
0.86(3)
0.86(3)
0.78(3)
0.80(4)
2.24(2)
2.28(3)
2.16(3)
2.04(4)
2.831(2
2.887(2)
2.940(3)
2.826(3)
126(2)
128(2)
171(3)
169(4)
n1h1⋯o3
i
o2Wh2Wa⋯o6
o2Wh2WB⋯o5
ii
ꢆsꢍꢉꢉꢇꢁꢅꢍ cꢃꢂꢇꢋ: i = 2 − x, 1 − y, 1 − z; ii = 1 − x, 1 − y, 1 ꢏ z.

3658
E. BRꢁꢄꢁ ET ꢁꢂ.
Figure 4. iꢊꢁꢇꢅ- ꢆꢊꢂ ꢄꢊꢁꢅꢆꢉꢃꢌꢇcꢈꢌꢆꢅ ꢀꢍꢂꢅꢃgꢇꢊ bꢃꢊꢂꢋ ꢄꢊ 1. Cꢃꢌꢃꢅ cꢃꢂꢇ: cꢃppꢇꢅ, ꢃꢅꢆꢊgꢇ; ꢃxꢍgꢇꢊ, ꢅꢇꢂ; ꢊꢄꢁꢅꢃgꢇꢊ, bꢌꢈꢇ; cꢆꢅbꢃꢊ, gꢅꢆꢍ;
ꢍꢂꢅꢃgꢇꢊ, wꢀꢄꢁꢇ.
ꢀ
Figure 5. Cꢃꢃꢅꢂꢄꢊꢆꢁꢄꢃꢊ ꢇꢊvꢄꢅꢃꢊꢉꢇꢊꢁ ꢃꢎ Cꢈ(ii) ꢄꢊ 2, wꢄꢁꢀ ꢌꢆbꢇꢌꢄꢊg. tꢀꢇꢅꢉꢆꢌ ꢇꢌꢌꢄpꢋꢃꢄꢂꢋ ꢆꢅꢇ ꢋꢀꢃwꢊ ꢆꢁ 50% pꢅꢃbꢆbꢄꢌꢄꢁꢍ. Cꢃꢌꢃꢅ cꢃꢂꢇ: cꢃppꢇꢅ,
ꢃꢅꢆꢊgꢇ; ꢃxꢍgꢇꢊ, ꢅꢇꢂ; ꢊꢄꢁꢅꢃgꢇꢊ, bꢌꢈꢇ; cꢆꢅbꢃꢊ, gꢅꢆꢍ. hꢍꢂꢅꢃgꢇꢊꢋ ꢆꢅꢇ ꢃꢉꢄꢁꢁꢇꢂ ꢎꢃꢅ cꢌꢆꢅꢄꢁꢍ.
3
.3.1. Crystal structure of [Cu (H O) (Hbzlidp) ](CF SO ) ·2H O (1)
2 2 6 2 3 3 2 2
Selected bond lengths and angles for 1 are presented in table 3. The structure is formed by a dinuclear
2+
[Cu (H O) (Hbzlidp) ] unit, two trifluoromethanesulfonate anions, and two crystallization water mole-
2 2 6 2
2
+
−
cules. The [Cu (H O) (Hbzlidp) ] units are built by two copper(II) ions joined through two Hbzlidp lig-
2
2
6
2
ands as shown in figure 3. The ligand is protonated at N, with a N1–H1 distance of 0.85(3) Å, avoiding the
direct union to the copper ions. Hence, this potentially tridentate ligand is ditopic, through two oxygens
of different carboxylate groups. Each Cu(II) is square pyramidal (τ = 0.08) [50], being the donor atoms
−
two oxygen from independent Hbzlidp ligands (Cu1–O1 1.9743(15) Å and Cu1–O3 1.9928(14) Å), and
three other oxygens from coordinated water. Of these water molecules, two are in the equatorial plane,

JOꢀRNꢁꢂ OF COORDINꢁTION CHEMISTRꢃ
3659
Figure 6. Cꢈ(ii) ꢂꢄꢊꢈcꢌꢇꢆꢅ ꢈꢊꢄꢁꢋ bꢅꢄꢂgꢇꢂ bꢍ cꢆꢅbꢃxꢍꢌꢆꢁꢇꢋ ꢄꢊ 2, ꢋꢀꢃwꢄꢊg ꢁꢀꢇ “pꢆꢂꢂꢌꢇ wꢀꢇꢇꢌ”cꢃꢊꢎꢃꢅꢉꢆꢁꢄꢃꢊ. hꢍꢂꢅꢃgꢇꢊꢋ ꢆꢅꢇ ꢃꢉꢄꢁꢁꢇꢂ ꢎꢃꢅ
cꢌꢆꢅꢄꢁꢍ. Cꢃꢌꢃꢅ cꢃꢂꢇ: cꢃppꢇꢅ, ꢃꢅꢆꢊgꢇ; ꢃxꢍgꢇꢊ, ꢅꢇꢂ; ꢊꢄꢁꢅꢃgꢇꢊ, bꢌꢈꢇ; cꢆꢅbꢃꢊ, gꢅꢆꢍ.
Figure 7. tꢀꢇ 2-d ꢆꢅꢅꢆꢍ ꢃꢎ Cꢈ(ii) ꢂꢄꢊꢈcꢌꢇꢆꢅ ꢈꢊꢄꢁꢋ ꢄꢊ 2. tꢀꢇ bꢇꢊzꢍꢌ gꢅꢃꢈpꢋ ꢆꢊꢂ ꢁꢀꢇ ꢀꢍꢂꢅꢃgꢇꢊꢋ ꢆꢅꢇ ꢃꢉꢄꢁꢁꢇꢂ ꢎꢃꢅ cꢌꢆꢅꢄꢁꢍ. Cꢃꢌꢃꢅ cꢃꢂꢇ: cꢃppꢇꢅ,
ꢃꢅꢆꢊgꢇ; ꢃxꢍgꢇꢊ, ꢅꢇꢂ; ꢊꢄꢁꢅꢃgꢇꢊ, bꢌꢈꢇ; cꢆꢅbꢃꢊ, gꢅꢆꢍ.
at an average Cu–O distance of 1.9247(19) Å. The third water occupies the apical position of the square
pyramid (Cu1–O2W distance 2.2572(19) Å). In the dimer, the Cu–Cu average distance is 4.8551(5) Å.
Intramolecular H-bonds are present (table 4) between the protonated N and the O of the carboxylate
groups and also between the equatorial water molecules and the carboxylates (figure 4). The packing
of 1 is supported by a hydrogen bond network involving water molecules, trifluoromethanesulfonates,
and carboxylate groups (table S1, Supplementary Material).

3660
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Figure 8. mꢃꢌꢇcꢈꢌꢆꢅ ꢋꢁꢅꢈcꢁꢈꢅꢇ ꢃꢎ 3, wꢄꢁꢀ ꢌꢆbꢇꢌꢄꢊg. tꢀꢇꢅꢉꢆꢌ ꢇꢌꢌꢄpꢋꢃꢄꢂꢋ ꢆꢅꢇ ꢋꢀꢃwꢊ ꢆꢁ 50% pꢅꢃbꢆbꢄꢌꢄꢁꢍ. hꢍꢂꢅꢃgꢇꢊꢋ ꢆꢅꢇ ꢃꢉꢄꢁꢁꢇꢂ ꢎꢃꢅ cꢌꢆꢅꢄꢁꢍ.
Cꢃꢌꢃꢅ cꢃꢂꢇ: ꢊꢄckꢇꢌ, gꢅꢇꢇꢊ; ꢃxꢍgꢇꢊ, ꢅꢇꢂ; ꢊꢄꢁꢅꢃgꢇꢊ, bꢌꢈꢇ; cꢆꢅbꢃꢊ, gꢅꢆꢍ.
Figure 9. uꢊꢄꢁ cꢇꢌꢌ ꢃꢎ ꢁꢀꢇ ꢋꢁꢅꢈcꢁꢈꢅꢇ ꢃꢎ 3. hꢍꢂꢅꢃgꢇꢊꢋ ꢆꢅꢇ ꢊꢃꢁ ꢋꢀꢃwꢊ ꢎꢃꢅ cꢌꢆꢅꢄꢁꢍ. Cꢃꢌꢃꢅ cꢃꢂꢇ: ꢊꢄckꢇꢌ, gꢅꢇꢇꢊ; ꢃxꢍgꢇꢊ, ꢅꢇꢂ; ꢊꢄꢁꢅꢃgꢇꢊ, bꢌꢈꢇ;
cꢆꢅbꢃꢊ, gꢅꢆꢍ.
3
.3.2. Crystal structure of [Cu(NO )(Hbzlidp)] (2)
3 ∞
−
Selected bond lengths and angles for 2 are presented in table 3. Cu(II) centers are connected by Hbzlidp
in the structure. Each Cu(II) is five coordinate with a slightly distorted square pyramidal geometry
−
(
τ = 0.05) [50], the donors are four oxygens of four different Hbzlidp anions (average Cu–O distance
1
.9650(15) Å) and O of a nitrate in the apical position of the square pyramid (figure 5) with a Cu–O5
distance of 2.1429(16) Å. ꢁgain, the organic ligand is protonated at N (the N1–H1 distance is 0.92(2) Å),
avoiding direct union to copper ions and acting as bridging ligand. The ligand connects four different
Cu(II) ions through oxygens of two carboxylate groups, resulting in pairs of Cu(II) centers bridged
by four syn,syn carboxylate groups to generate dinuclear “paddle wheel” units (figure 6) [51–54]. The

JOꢀRNꢁꢂ OF COORDINꢁTION CHEMISTRꢃ
3661
Figure 10. mꢃꢌꢇcꢈꢌꢆꢅ ꢋꢁꢅꢈcꢁꢈꢅꢇ ꢃꢎ 3 ꢋꢀꢃwꢄꢊg ꢁꢀꢇ ꢄꢊꢁꢅꢆꢉꢃꢌꢇcꢈꢌꢆꢅ ꢀꢍꢂꢅꢃgꢇꢊ bꢃꢊꢂ bꢇꢁwꢇꢇꢊ cꢆꢅbꢃxꢍꢌꢆꢁꢇ o ꢆꢊꢂ wꢆꢁꢇꢅ ꢉꢃꢌꢇcꢈꢌꢇꢋ. Cꢃꢌꢃꢅ
cꢃꢂꢇ: ꢊꢄckꢇꢌ, gꢅꢇꢇꢊ; ꢃxꢍgꢇꢊ, ꢅꢇꢂ; ꢊꢄꢁꢅꢃgꢇꢊ, bꢌꢈꢇ; cꢆꢅbꢃꢊ, gꢅꢆꢍ; ꢀꢍꢂꢅꢃgꢇꢊ, wꢀꢄꢁꢇ.
Cu–Cu distance in the dimer is 2.6776(5) Å. The dinuclear copper units are arranged in a rhombus
type grid (figure 7) in a 2-D layer structure. Intramolecular and intermolecular hydrogen bonds
are present in the structure and relevant distances and angles are included in table S2 (Supplementary
Material).
3
.3.3. Crystal structure of [Ni (H O) (bzlidp) ] (3)
2 2 4 2
Selected bond lengths and angles for 3 are presented in table 3. The structure is formed by
2
−
[
Ni (H O) (bzlidp) ] neutral dinuclear units, built by two nickel ions joined through two bzlidp lig-
2 2 4 2
2
−
ands as shown in figure 8. The bzlidp are tridentate ligands, coordinating through two oxygens of the
carboxylate groups, one of which is bridging and coordinated to the other Ni(II) of the molecule. Each
2
−
Ni(II) is octahedral, and the coordination sphere is completed by nitrogen of bzlidp and two water
molecules (average Ni–OW distance 2.0719(12) Å) in a cis position. The intramolecular Ni–Ni average
distance is 3.1938(5) Å. The unit cell of 3 is shown in figure 9. The units present intramolecular hydro-
gen bonds, between the free carboxylate oxygen O2 of one half of the molecule, and one of the water
molecules in the other half, and between carboxylic O3 and the O1W of a coordinated water (figure 10
and table S3, Supplementary Material).
4. Conclusion
The dicarboxylic acid compound H bzlidp showed interesting versatility as a ligand. It can assemble
2
metal ions into polynuclear systems with different patterns of connection. In this way, it was possible
to synthesize and determine the structure of three different polynuclear complexes, in which the ligand
was a bridge, although with different coordination modes. Control of the coordination abilities of
bzlidp was achieved by appropriate selection of the reaction conditions. In particular, acidic pH values
led this tridentate ligand to be ditopic due to the N protonation, and a dinuclear, cyclic structure was
obtained. When an excess of copper was employed, a more extended system was obtained, with each
carboxylate group connecting two copper centers. Finally, in the case of nickel, which favors octahedral
geometries, a dinuclear, more compact structure was formed, with the deprotonated N also coordinated
to the metal center.
Supplementary material
CCDC 1454769–1454771 contains the supplementary crystallographic data for 1–3. These data can be obtained free of
charge from The Cambridge Crystallographic Data Center via www.ccdc.cam.ac.uk/data_request/cif.

3662
E. BRꢁꢄꢁ ET ꢁꢂ.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported partially by CSIC (ꢀruguay) through Programa de ꢁpoyo a Grupos de Investigación; C.M. thanks
ꢁ
NII (ꢀruguay) [grant number FCE_2_2011_1_Nº 6638]; Supported partially by the Spanish MINECO [grant number
MꢁT2013-46649-C4-4-P], [grant number MꢁT2015-71070-REDC]; the Eꢀ-FEDER funds.
References
[
[
[
[
[
[
[
[
[
1] ꢂ. Ma, C. ꢁbney, W. ꢂin. Chem. Soc. Rev., 38, 1248 (2009).
2] M.ꢃ. Masoomi, ꢁ. Morsali. Coord. Chem. Rev., 256, 2921 (2012).
3] J.-R. ꢂi, R.J. Kuppler, H.-C. Zhou. Chem. Soc. Rev., 38, 1477 (2009).
4] D. Farrusseng, S. ꢁguado, C. Pinel. Angew. Chem. Int. Ed., 48, 7502 (2009).
5] Z. Ma, B. Moulton. Coord. Chem. Rev., 255, 1623 (2011).
6] M. Kurmoo. Chem. Soc. Rev., 38, 1353 (2009).
7] H.-ꢂ. Jiang, Q. Xu. Chem. Commun., 47, 3351 (2011).
8] ꢂ.J. Murray, M. Dincă, J.R. ꢂong. Chem. Soc. Rev., 38, 1294 (2009).
9] R. Robson. Dalton Trans., 38, 5113 (2008).
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
10] Q. Zhang, C. ꢂu, W. ꢃang, ꢃ. ꢃu. Inorg. Chem. Commun., 7, 277 (2004).
11] ꢁ. Mateescu, C. Gabriel, R.G. Raptis, P. Baran, ꢁ. Salifoglou. Inorg. Chim. Acta, 360, 638 (2007).
12] T.-F. ꢂiu, J. ꢂü, R. Cao. CrystEngComm, 12, 660 (2010).
13] ꢁ. Karmakar, I. Goldberg. CrystEngComm, 13, 339 (2011).
14] ꢁ. Karmakar, I. Goldberg. CrystEngComm, 13, 350 (2011).
15] ꢁ. Karmakar, C.ꢂ. Oliver, S. Roy, ꢂ. Öhrström. Dalton Trans., 44, 10156 (2015).
16] ꢂ.-ꢃ. ꢂai, Z. ꢂiu, G.-C. Han, Z. Chen. J. Cluster Sci., 26, 1845 (2015).
17] W.-H. Huang, ꢃ.-ꢃ. Wang, ꢃ.-N. Zhang, T. ꢂiu, S.-ꢃ. ꢂiu, ꢃ.-X. Wang, ꢂ.-ꢃ. Pang, ꢃ.-F. Kang. Inorg. Chim. Acta, 433, 52 (2015).
18] H.-ꢃ. ꢂi, ꢂ.-H. Cao, ꢃ.-ꢂ. Wei, H. Xu, S.-Q. Zang. CrystEngComm, 17, 6297 (2015).
19] M. ꢃu, ꢂ. Xie, S. ꢂiu, C. Wang, H. Cheng, ꢃ. Ren, Z. Su. Inorg. Chim. Acta, 360, 3108 (2007).
20] T. ꢂiu, J. ꢂü, ꢂ. Shi, Z. Guo, R. Cao. CrystEngComm, 11, 583 (2009).
21] R. Carballo, B. Covelo, M.S. El Fallah, J. Ribas, E.M. Vázquez-ꢂópez. Cryst. Growth Des., 7, 1069 (2007).
22] H. ꢂi, H. Tian, M. Guo, F.ꢃ. He, C. Hu. Inorg. Chem. Commun., 9, 895 (2006).
23] ꢃ. Xie, F.-ꢃ. Bai, ꢃ.-H. Xing, Z. Wang, H.-ꢃ. Zhao, Z. Shi. Z. Anorg. Allg. Chem., 636, 1585 (2010).
24] C.-ꢂ. Chen, J.-ꢃ. Zhang, C.-ꢃ. Su. Eur. J. Inorg. Chem., 2007, 2997 (2007).
25] C. Janiak, J.K. Vieth. New J. Chem., 34, 2366 (2010).
26] R.-W. Huang, B. ꢂi, ꢃ.-Q. Zhang, ꢃ. Zhao, S.-Q. Zang, H. Xu. Inorg. Chem. Commun., 39, 106 (2014).
27] X. Chai, H. Zhang, S. Zhang, ꢃ. Cao, ꢃ. Chen. J. Solid State Chem., 182, 1889 (2009).
28] Z. Pan, H. Zheng, T. Wang, ꢃ. Song, ꢃ. ꢂi, Z. Guo, S.R. Batten. Inorg. Chem., 47, 9528 (2008).
29] C. Kremer, P. Morales, J. Torres, J. Castiglioni, J. González-Platas, M. Hummert, H. Schumann, S. Domínguez. Inorg.
Chem. Commun., 11, 862 (2008).
[30] E. Braña, C. Mendoza, P. Vitoria, J. González-Platas, S. Domínguez, C. Kremer. Inorg. Chim. Acta, 417, 192 (2014).
[31] ꢃ.ꢁ. Skorik, C.ꢁ.R. Gomes, N.V. Podberezskaya, G.V. Romanenko, ꢂ.F. Pinto, ꢃ.G. ꢃatluk. Biomacromolecules, 6, 189 (2005).
[32] ꢃ.ꢁ. Skorik, G.V. Romanenko, ꢂ.K. Neudachina, ꢁ.ꢁ. Vshivkov. Russ. J. Coord. Chem., 27, 796 (2001).
[33] ꢃ.ꢁ. Skorik, G.V. Romanenko, C.ꢁ.R. Gomes, ꢂ.K. Neudachina, ꢁ.ꢁ. Vshivkov. Polyhedron, 21, 2719 (2002).
[34] ꢃ.ꢁ Skorik, N.V. Podberezskaya, G.V. Romanenko, E.V. Osintseva, ꢂ.K. Neudachina, ꢁ.ꢁ. Vshivkov. Russ. J. Inorg. Chem.,
4
8, 199 (2003).
[
[
[
[
[
[
[
[
[
[
[
[
35] IUPAC Stability Constants Database: SC-Database and Mini-SCDatabase, ꢁcademic Software (2007).
36] P. Gans, B. O’Sullivan. Talanta, 51, 33 (2000).
37] P. Gans, ꢁ. Sabatini, ꢁ. Vacca. Talanta, 43, 1739 (1996).
38] ꢂ. ꢁlderighi, P. Gans, ꢁ. Ienco, D. Peters, ꢁ. Sabatini, ꢁ. Vacca. Coord. Chem. Rev., 184, 311 (1999).
39] CrysAlisPro Software System, Version 1.171.38.41, Rigaku Corporation, Oxford (2016).
40] G.M. Sheldrick. Acta Crystallogr. A, 71, 3 (2015).
41] G.M. Sheldrick. Acta Crystallogr. C, 71, 3 (2015).
42] G.M. Sheldrick. SHELXL 2014/7, ꢀniversity of Gottingen, Germany (2014).
43] G.M. Sheldrick. Acta Crystallogr. A, 64, 112 (2008).
44] J. Cologne, G. Descotes, G. Frenay. Bull. Soc. Chim. Fr., 2264 (1963).
45] J. Torres, C. Kremer, S. Domínguez. Pure Appl. Chem., 80, 1303 (2008).
46] D.K. ꢂaing, ꢂ.D. Pettit. J. Chem. Soc., Dalton Trans., 2297 (1975).

JOꢀRNꢁꢂ OF COORDINꢁTION CHEMISTRꢃ
3663
[47] K. Nakamoto. Infrared and Raman Spectra of Inorganic and Coordination Compounds, B, 5th Edn, Wiley – Interscience,
New ꢃork (1997).
[
[
48] ꢁ.ꢂ. ꢁrduini, M. Garnett, R.C. Thompson, T.C.T. Wong. Can. J. Chem., 53, 3812 (1975).
49] K. Nakamoto. Infrared and Raman Spectra of Inorganic and Coordination Compounds, A, 5th Edn, Wiley – Interscience,
New ꢃork (1997).
[
[
[
[
[
50] ꢁ.W. ꢁddison, T.N. Rao, J. Reedijk, J. van Rijn, G.C. Verschoor. J. Chem. Soc., Dalton Trans., 1349 (1984).
51] ꢁ. Schneemann, V. Bon, I. Schwedler, I. Senkovska, S. Kaskel, R.ꢁ. Fischer. Chem. Soc. Rev., 43, 6062 (2014).
52] J. Seo, C. Bonneau, R. Matsuda, M. Takata, S. Kitagawa. J. Am. Chem. Soc., 133, 9005 (2011).
53] H. Chun, D.N. Dybtsev, H. Kim, K. Kim. Chem.–Eur. J., 11, 3521 (2005).
54] S. ꢃoungme, ꢁ. Cheansirisomboon, C. Danvirutai, C. Pakawatchai, N. Chaichit, C. Engkagul, G.ꢁ. van ꢁlbada, J.S. Costa,
J. Reedijk. Polyhedron, 27, 1875 (2008).