Synthesis and structural characterization of new N2O2-donor Schiff base macrocycles and their silver(I) coordination polymers

Article abstract of DOI:10.1016/j.ica.2015.07.016

Two N₂O₂-donor macrocyclic Schiff bases mD1 and mD2 (mD1 = 1,5-diaza-2,4:7,8:16,17-tribenzo-9,15-dioxa-cyclooctadeca-1,5-dien; mD2 = 1,5-diaza-2,4:7,8:15,16-tribenzo-9,14-dioxa-cycloheptadeca-1,5-dien) were prepared by the [1+1] cycl

Full text of DOI:10.1016/j.ica.2015.07.016

Inorganica Chimica Acta 435 (2015) 283–291
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Inorganica Chimica Acta
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Synthesis and structural characterization of new N O -donor Schiff base
2
2
macrocycles and their silver(I) coordination polymers
a
a,
⇑
b
c
ˇ
Tomislav Bali c´ , Berislav Markovi c´ , Jarosław Ja z´ wi n´ ski , Dubravka Matkovi c´ -Calogovi c´
a
Department of Chemistry, Josip Juraj Strossmayer University of Osijek, Cara Hadrijana 8/A, 31000 Osijek, Croatia
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-481 Warsaw, Poland
University of Zagreb, Faculty of Science, Department of Chemistry, Division of General and Inorganic Chemistry, Horvatovac 102a, 10000 Zagreb, Croatia
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Two N O -donor macrocyclic Schiff bases mD1 and mD2 (mD1 = 1,5-diaza-2,4:7,8:16,17-tribenzo-9,15-
2
2
Received 26 February 2015
Received in revised form 5 June 2015
Accepted 10 July 2015
dioxa-cyclooctadeca-1,5-dien; mD2 = 1,5-diaza-2,4:7,8:15,16-tribenzo-9,14-dioxa-cycloheptadeca-1,5-
dien) were prepared by the [1+1] cyclocondensation reaction of the corresponding dialdehyde and dia-
mine. The reactions of the prepared macrocycles with silver nitrate led to formation of unique (regarding
Available online 21 July 2015
2 2
the N O -donors) silver coordination polymers, AgmD1 and AgmD2. All synthesized compounds were
characterized by vibrational spectroscopy (IR), thermal methods (TG/DSC) and the ligands additionally
by NMR. The crystal and molecular structures of the macrocycles and the silver coordination polymers
were determined by the single crystal X-ray diffraction method. The molecular structure of the macrocy-
cles is found to be rather similar, but with significant differences in the crystal packing arrangement due
to slight deviations from planarity. In the complex AgmD1 each silver atom is coordinated by two imino
nitrogen atoms of the neighboring ligand molecules and, with an oxygen atom of the nitrate group, thus
producing an infinite zig-zag polymeric chain. The silver atoms in AgmD2 are tetrahedrally coordinated
with two N-bound ligand molecules and two nitrate anions. This form of coordination produces an addi-
tional metallacyclic ring. The polymeric structure is formed through connection of the metallacyclic rings
by bridging nitrate anions. Slight deviations in the conformation of the macrocyclic ligands have signif-
icant impact upon the coordination mode and topology of the silver coordination polymer structures.
Ó 2015 Elsevier B.V. All rights reserved.
Keywords:
N O -donor
2 2
Schiff base macrocycles
Silver(I) coordination polymers
Polymeric chain
Metallacyclic ring
1
. Introduction
The chemistry of macrocycles has been an attractive scientific
on unsymmetrical macrocyclic systems [5–7], particularly on com-
partmental macrocycles [8,9]. Another, much less investigated
binding mode is the exo-coordination, where the metal ion is
linked outside the macrocyclic ring. This type of coordination
mode is certainly interesting as a potential synthesis route for con-
struction of macrocyclic coordination polymers and metallo-
organic frameworks (MOFs). Consequently, these materials are
potentially very interesting as building blocks of porous and bi-
porous MOFs.
In the literature we can identify two major strategic approaches
for synthesis of exo-coordinated macrocyclic compounds: (i)
replacement of weakly coordinated apical ligands in existing
endo-macrocyclic complexes with stronger ligands that are ditopic
[10,11] and (ii) design of macrocyclic ligands with exo-oriented
electron donor atoms. Until now, the ii strategy was less common
and there have been only a few known examples of such com-
pounds. Most of the investigations are dedicated to thioether
macrocycles that are suitable for coordination of soft metals
field for almost five decades [1]. The quest for elucidation of natu-
rally occurring processes that involve metal centers is the main
driving force that motivates scientists for research in this particu-
lar area. The macrocycles are usually prepared for their use as
specific binding agents and for complexation of charged and neu-
tral species [1,2]. In addition, the unusual stability of macrocyclic
complexes, known as the macrocyclic effect, is one of the major
features of these compounds. This feature validates application of
macrocycles as sensing agents [3] and selective separating agents
[
4]. However, for this type of applications, due to the nature of
the macrocyclic ligands, endo-coordinated macrocyclic complexes
metal ion is bonded inside macrocyclic cavity) are almost exclu-
(
sively investigated. Considering this type of coordination and
donor set atoms (N, O), a large number of investigations were done
[
4,12,13].
⇑
Corresponding author. Tel.: +385 31 399 975; fax: +385 31 399 969.
E-mail address: bmarkovi@kemija.unios.hr (B. Markovi c´ ).
http://dx.doi.org/10.1016/j.ica.2015.07.016
020-1693/Ó 2015 Elsevier B.V. All rights reserved.
0

2
84
T. Bali ´c et al. / Inorganica Chimica Acta 435 (2015) 283–291
Herein, we report the synthesis of two N
2
O
2
-donor Schiff base
2.2. X-ray crystallography
macrocyclic ligands (Scheme 1) and their silver coordination poly-
mers. To our knowledge, the prepared silver coordination polymers
are unique examples of macrocyclic coordination polymers with
this type of donor set atoms (N, O).
The compounds were identified by means of chemical analysis
and characterized by IR and NMR spectroscopy. The thermal prop-
erties of the compounds were investigated by TG/DSC method. The
molecular and crystal structures were determined by the single-
crystal X-ray diffraction.
The single-crystal X-ray diffraction data were collected at room
temperature (294 K) for the macrocyclic ligands (mD1 and mD2)
and at 190 K for the silver(I) coordination polymers (AgmD1 and
AgmD1) on an Oxford Diffraction Xcalibur 3 CCD diffractometer
with graphite-monochromated Mo-K
a
radiation (k = 0.71073 Å)
using –scans. Single-crystals of the coordination polymers
x
decomposed in contact with air and were therefore transferred
into mineral oil (Paratone N) and scooped with a plastic loop
whereas crystals of the macrocyclic ligands were glued to a thin
glass needle. The data reduction was performed using the
CrysAlis software package [15]. The structures were solved with
the SIR2004 program [16]. Refinement and analysis of the struc-
tures were done using the programs integrated within the
WinGX system [17]. The refinement procedure was performed by
2
. Experimental
2.1. General methods
All commercially available chemicals were of reagent grade and
used as purchased. IR spectra were recorded on Shimadzu FTIR
2
the full-matrix least-squares method based on F against all reflec-
tions using SHELXL-97 [18]. All non-hydrogen atoms were refined
anisotropically except the C atom of dichloromethane and chloro-
form molecules in AgmD1 which were disordered and were refined
isotropically. Restraints were used on these two disordered solvent
molecules. The occupation factor of disordered dichloromethane
and chloroform molecules refined to 0.75(1) and 0.25(1), respec-
tively. The studied crystal of AgmD1 is a racemic twin with the
twin ratio 0.55:0.45. Hydrogen atoms in the structures were placed
in calculated positions and refined using the riding model.
Geometrical calculations were done using PLATON [19,20] and
the structure drawings with ORTEP and MERCURY [21] programs.
The crystallographic data are summarized in Table 1.
8
4
400S spectrophotometer using the DRS 8000 attachment, in the
À1
000–400 cm
region. Approximately 3 mg of samples were
mixed with 100 mg of KBr (IR grade), placed in the sample cup
and FTIR data were collected using diffuse reflectance technique.
Thermogravimetric analyses were performed using a simultaneous
TGA-DSC analyzer (Mettler-Toledo TGA/DSC 1). The samples
(
approx. 20–30 mg) were placed in aluminum pans (100
lL) and
À1
heated in a nitrogen atmosphere (200 mL min ) up to 500 °C at
a rate of 10 °C min . Complex compounds (AgmD1 and AgmD2)
were heated in an oxygen atmosphere (200 mL min ) up to
5
tionally treated in oxygen atmosphere up to 150 °C and held at that
temperature for 10 min. The data collection and analysis was per-
formed using the program package STARe Software 10.0 [14].
Elemental analyses were performed on PerkinElmer 2400 Series
II CHNS/O system. All NMR measurements were performed on
Varian VNMRS 500 MHz and Varian VNMRS 600 MHz spectrome-
ters (Institute of Organic Chemistry PAS, Warsaw), using a broad
band 5 mm probe, equipped with a z-gradient coil. The measure-
À1
À1
À1
50 °C at a rate of 10 °C min . The compound AgmD1 was addi-
2.3. Synthesis
Synthesis of dialdehydes D1, D2 and the corresponding macro-
cyclic ligands (mD1 and mD2) was previously reported by Larikova
et al. [22]. Herein we report synthesis of the above mentioned
compounds under the procedure as follows.
ments were carried out in CDCl
3
, at room temperature. Signal
1
assignments were achieved on the basis of one-dimensional
H
2.3.1. Preparation of the dialdehydes
2.3.1.1. 2-[5-(2-Formylphenoxy)pentoxy]benzaldehyde (D1). 10.5 ml
(0.1 mol) of salicylaldehyde and 13.9 g (0.1 mol) of K CO , were
2 3
mixed in 50 ml of dimethylformamide and the mixture was heated
to boiling temperature (153 °C). 6.85 ml (0.05 mol) of 1,5-dibro-
mopentane were dissolved in 10 ml of dimethylformamide and
1
3
13
1
13
1
NMR and C NMR spectra, and 2D C, H HSQC and C, H
1
5
HMBC spectra. N NMR spectra have been acquired using 2D
1
5
1
1
13
inverse technique ( N, H HMBC). H and C chemical shifts were
1
13
15
given with respect to H and C signals of TMS (0 ppm). The
N
15
chemical shifts were given with respect to the N NMR signal of
1
5
1
13
nitromethane (d ( N) = 0 ppm). Prediction of the H and C chem-
ical shifts were performed using ChemDraw Ultra vs. 12.0.
Predicted chemical shifts agree satisfactorily with the experimen-
tal values. Experimental and predicted chemical shifts are collected
in Fig. S7. The powder X-ray diffraction data were collected by the
2 3
slowly added to the mixture of salicylaldehyde and K CO . The
mixture was refluxed at boiling temperature for 4 h and stirred
at room temperature for additional 3 h. After the reaction was
completed, approximately 500 ml of water were added and the
resulting precipitate was filtered and washed with water. The pro-
Philips 1840 X-ray diffractometer with CuK
at 295(2) K. Patterns were collected in the scan range 2h = 5–50°
with the step size of 0.03° and at 1.5 s per step.
a
radiation (1.54056 Å)
duct was recrystallized from absolute ethanol. Yield: 51%. IR
(cm ): 2947(m), 2873(m), 1678(s), 1600(s), 1242(s), 1012(m),
765(s). Melting point: 66 °C (DSC, from EtOH).
m
max
À1
Scheme 1. Representation of ligands mD1 and mD2.

T. Bali ´c et al. / Inorganica Chimica Acta 435 (2015) 283–291
285
Table 1
Crystallographic data and structure refinement details for all compounds.
Compound
mD1
mD2
AgmD1
AgmD2
CCD number
Formula
Formula weight
Crystal system
Space group
T (K)
a (Å)
b (Å)
c (Å)
1039600
1039601
1039602
1039603
C
25
H
24
N
2
O
2
C
24
H
22
N
2
O
2
C
26
H25.75 Ag Cl2.25
N
3
O
5
C
48
H
44 Ag
2 7 13
N O
384.46
monoclinic
P 2 /n
370.44
monoclinic
P 2 /c
647.88
orthorhombic
1142.64
monoclinic
C 2/c
190(2)
12.0290(3)
19.8230(5)
18.9490(5)
91.619(2)
4516.6(2)
4
1
1
P 2 2 2
1 1 1
294(2)
15.493(1)
7.889(7)
16.783(1)
91.136(9)
2050.9(3)
4
294(2)
15.671(1)
7.4720(7)
33.315(2)
92.029(6)
3898.5(3)
8
190(2)
8.2540(4)
15.7340(6)
20.5940(8)
b (°)
3
V (Å )
2674.51(19)
4
1.609
Z
D
l
À3
calc (g cm
)
1.245
0.079
1.262
0.081
1.680
0.944
À1
(mm
)
1.020
F(000)
Total data
Number of unique data
Number of parameters
816
13174
4009
1568
26701
7634
1312
9834
5657
348
2316
16793
4877
262
536
317
Flack parameter
0.55(7)
0.0601
0.1555
1.065
a
R
wR
1
, [F
o
P 4
r
(F
o
)]
0.0654
0.1192
1.063
0.114; À0.134
0.0757
0.1170
1.072
0.161; À0.138
0.0378
0.0942
1.091
0.614; À0.811
b
2
2
Goodness of fit on F (S)
Minimum and maximum electron density (e Å
À3
)
1.070; À0.820
a
R =
wR = [
R
||F
R
o
| À |F
c
||/
R
|F
R
o
|.
w(F
b
2
2
2
2
)2]1/2.
(F
o
À F
c
) /
o
Table 2
Dihedral angles between benzene rings in mD1 and mD2.
2.3.2.2. Preparation of mD2. The macrocyclic ligand mD2 was pre-
pared by dropwise addition of m-phenylenediamine 0.243 g
(2.5 mmol) dissolved in 25 ml of absolute ethanol to the ethanol
solution of dialdehyde D2 0.625 g (2 mmol) and triethylamine
0.274 ml (2 mmol). The resulting solution was heated at the reflux
temperature for 3 h. After cooling, a pale yellow suspension was
formed. This suspension was left at room temperature for 2 weeks,
during which time larger crystals gradually formed. Single crystals
suitable for X-ray diffraction experiments were obtained directly
from the suspension mixture. Yellow product was recrystallized
from dichloromethane/methanol mixture to obtain pale yellow
Compound
A/B
A/C
B/C
mD1
53.1(1)° 59.4(1)° 56.1(1)°
16.6(1)° 26.2(1)° 21.3(1)°
mD2 (conformer 1)
mD2 conformer 2 (major part of disordered C 17.3(1)° 24.3(4)° 14.3(4)°
ring)
conformer 2 (minor part of disordered C ring)
30.4(4)° 26.7(6)°
2.3.1.2. 2-[4-(2-Formylphenoxy)butoxy]benzaldehyde (D2). K
2 3
CO
1
3.9 g (0.1 mol) and salicylaldehyde 10.5 ml (0.1 mol) were mixed
in 50 ml of dimethylformamide. The mixture was brought to the
reflux temperature and 5.97 ml (0.05 mol) of 1,4-dibromobutane
dissolved in 10 ml of dimethylformamide were then added. The
reaction mixture was refluxed for 5 h and then stirred at room
temperature for additional 3 h. Approximately 500 ml of water
was added to the reaction mixture. The resulting precipitate was
powder. Yield: 45%. Anal. Calcd for C24
N, 7.56; Found: C, 77.93, H, 5.96; N, 7.51%. IR
H
22
N
2
O
2
: C, 77.81; H, 5.99;
À1
m
max (cm ):
2955(m), 2875(m), 1615(m), 1600(s), 1574(s), 1240(s), 1456(s),
1041(m), 802(m), 755(s). Thermal decomposition: 405 °C (DSC,
from DCM/MeOH). NMR data are given in Figs. S7b, S13–S22.
filtered and washed with water. The product was recrystallized
2.3.3. Preparation of the silver(I) coordination polymers
À1
from absolute ethanol. Yield: 55%. IR
mmax (cm ): 2954(m),
2.3.3.1. Preparation of {Ag[mD1(NO )]-dichloromethane-chloroform
3
2
876(m), 1675(s), 1600(s), 1244(s), 1011(m), 754(s). Melting
(1/0.75/0.25)}n (AgmD1). The silver coordination polymer of mD1
point: 108 °C (DSC, from EtOH).
was obtained by mixing a dichloromethane solution of ligand
mD1 19.2 mg (0.05 mmol) with a methanol solution of silver
nitrate 8.45 mg (0.05 mmol). The reaction was performed at room
temperature in a U-shaped tube, using chloroform as the diffusion
reagent. After 24 h single crystals suitable for diffraction experi-
ments were obtained. The crystals decompose in contact with air.
The analysis was done for crystals without solvent molecules. Anal.
2
2
.3.2. Preparation of the ligands
.3.2.1. Preparation of mD1. 0.625 (2 mmol) g of dialdehyde D1
were dissolved in 40 ml of absolute ethanol and 0.274 ml (2 mmol)
of triethylamine were added to this solution. The solution was
heated to reflux temperature (78 °C) and 0.243 g (2.5 mmol) of
m-phenylendiamine dissolved in 25 ml of absolute ethanol were
gradually added. Resulting solution was heated at reflux tempera-
ture for 3 h. After the reaction was completed the suspension was
left at room temperature for 24 h. Needle-like crystalline product
was filtered. Single crystals suitable for X-ray diffraction experi-
ments were obtained directly from the reaction mixture. The pro-
duct was recrystallized from chloroform. Yield: 80%. Anal. Calcd for
Calc. for C25
H, 4.36; N, 7.42. IR
H
24AgN
3
O
5
: C, 54.17; H, 4.36; N, 7.58; Found: C, 54.24,
À1
mmax (cm ): 1601(m), 1383(s), 433(w).
2 2 3 3 n
2.3.3.2. Preparation of {Ag [(mD2) (NO ) ]} (AgmD2). 0.1 mmol
(37 mg) of mD2 was dissolved in a small amount of dichloro-
methane and heated. The resulting solution was added to a heated
methanol solution of silver nitrate 16.9 mg (0.1 mmol). The yellow
solution was cooled to room temperature and filtered. The filtrate
was placed in a 10 ml vial and diethylether was diffused into the
filtrate. After two weeks color of the solution changed into dark
red, and brown hexagonal crystals suitable for diffraction experi-
ments appeared on the edges of the vial. The crystals are unstable
C
6
1
25
H
24
N
2
O
2
: C, 78.1; H, 6.29; N, 7.29; Found: C, 77.7, H, 6.27; N,
À1
.84%. IR
m
max (cm ): 2933(m), 2883(m), 1614(m), 1600(s),
575(s), 1458(s), 1269(s) 1244(s), 1055(m), 804(m), 754(s).
3
Melting point: 272 °C (DSC, from CHCl ). NMR data are given in
Figs. S7a, S13–S18.

2
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T. Bali ´c et al. / Inorganica Chimica Acta 435 (2015) 283–291
À1
in contact with air, however more stable than AgmD2. Anal. Calc.
appear in the region 804–752 cm . Both spectra are free of vibra-
for: C48
H, 3.95; N, 8.22; IR
H
44Ag
2
N
7
O
13 C, 50.42; H, 3.88; N, 8.58. Found: C, 50.26,
tion bands related to the primary amino and aldehyde groups.
In comparison to the IR spectra of the ligands, spectra of the sil-
À1
mmax (cm ): 1601(m), 1383(s), 416(w).
ver complexes show very strong absorption maxima close to
À1
1
385 cm , corresponding to the stretching vibrations of the
nitrate anion. The stretching vibrations of the imino group in the
complexes are shifted to slightly lower values in comparison to
the ligand (red shift). This observation indicates that the imino
group is involved in the formation of metal–ligand bond. The Ag–
3
. Results and discussion
3.1. Synthesis
N
stretching vibrations in AgmD1 and AgmD2 appear at
The macrocycles were prepared by the [1+1] cyclocondensation
reactions of a dialdehyde and diamine, with a relatively high yield.
It should be noted that these reactions do not require employment
À1
À1
4
33 cm and 416 cm , respectively [23]. Other vibrations previ-
ously described in the uncoordinated ligands do not show any sig-
nificant changes. IR spectra of ligands and complexes can be found
in ESI (Figs. S1–S4).
In order to investigate influence of the nitrate anion on the
interactions within the polymeric structure, compound AgmD1
was thermally treated in an oxygen atmosphere up to 150 °C for
of the high dilution technique or presence of
a template.
Furthermore, the preliminary investigations indicate that the syn-
thesis of these macrocycles can be achieved by simple
mechanochemical synthesis or by simple mixing of the ethanolic
reactant solutions at room temperature.
Silver coordination polymers with the prepared macrocycles
were obtained by slow diffusion of the reactant solution through
a liquid membrane.
1
0 min. The IR spectrum of the thermally treated coordination
polymer AgmD1, represented in Fig. S5, indicates absence of the
vibrations typical for the nitrate anion (vibrations close to 1380,
À1
8
30 and 690 cm ). Other vibrations observed in the thermally
untreated AgmD1 are found to be present in the spectrum of the
3.2. IR spectroscopy
thermally treated compound.
The IR spectra of the prepared ligands are rather similar. The
3.3. NMR spectroscopy of the ligands
stretching vibrations of the imine group in the ligands mD1 and
À1
mD2 appears at 1614 and 1615 cm , respectively. The stretching
The assignment of NMR signals was performed on the basis of
1D and 2D NMR spectra. Some dubious assignments concerning
the signal order in the phenol ring were explained by chemical
shifts prediction using the ChemDraw module. Observed NMR data
fully confirmed the structures of the ligands. Unfortunately, we
were not able to acquire NMR spectra of the Ag complexes, due
vibrations of the aliphatic C–H are in the region 2945–
À1
À1
2
1
874 cm . Also, both spectra exhibit strong vibration bands at
À1
269 cm
(mD1) and 1240 cm
(mD2) that are assigned to
stretching vibration of the Caromatic–O–Caliphatic group. C–H bending
vibration bands of the meta and ortho substituted benzene rings
Fig. 1. TG (full lines) and DSC (dashed lines) curves of AgmD1 (red) and AgmD2 (blue) recorded in oxygen atmosphere. (For interpretation of the references to color in this
figure legend, the reader is referred to the web version of this article.)

T. Bali ´c et al. / Inorganica Chimica Acta 435 (2015) 283–291
287
to their decomposition in solution and precipitation of an insoluble
material. Additional information regarding the NMR results of the
ligands can be found in the Supplementary material (Figs. S13–
S22).
decomposition of the nitrate groups and therefore the structural
integrity of this compound is strongly dependent upon presence
of anionic species. In addition, the thermal analysis of these com-
pounds is in very good agreement with the crystal structure stud-
ies, i.e., silver–ligand bond lengths.
3.4. Thermal analysis (TG/DSC)
3
.5. Crystal structure of ligands mD1 and mD2
The samples of ligands mD1 and mD2 were heated from 25 to
00 °C in a nitrogen atmosphere. The silver coordination polymers
5
The single crystals of both ligands were obtained directly from
were heated in reactive atmosphere of oxygen from 25 to 550 °C.
Thermoanalytical data for the ligands are represented in
Table S1. The TG curve of mD1 indicates that the compound is
stable up to 336 °C. Thermal decomposition occurs in one step
which is accompanied by a 68% mass loss. The DSC curve of mD1
shows two distinctive peaks. The endothermic peak at 272 °C can
be attributed to the melting point of the compound. The second,
exothermic peak at 407 °C is related to thermal decomposition of
the compound. The TG curve of mD2 reveals a continuous mass
loss between 345 and 500 °C. Furthermore, the DSC curve of the
same compound shows a broadened exothermic peak at 405 °C
that is related to thermal decomposition.
Thermoanalytical data for the complexes (AgmD1 and AgmD2)
are given in Table S1 and the corresponding curves are presented
in Fig. 1. Measurements of AgmD1 were done on decomposed crys-
tals of since the solvent molecules leave the crystals upon standing
at room temperature. The TG curve of AgmD1 shows thermal
degradation in three steps. The first step is accompanied by a mass
loss of 2.6% and a sharp exothermic peak on the DSC curve. The
second step occurs in the temperature interval from 150 to
the reaction mixture. Conformation of the free oxa-aza macrocy-
cles can be described by considering the orientation of the poten-
tial donor atoms, torsion angles associated with these atoms,
distance between donor atoms etc. [25]. The above mentioned fac-
tors can have a strong effect upon the complexation abilities of the
macrocyclic system and thus can influence stability of the derived
complexes [4,26]. Theoretical studies [27] have shown that the
most stable conformation of donor atoms in the oxa-aza macrocy-
cles is when the oxygen atoms are oriented in an endodentante
manner and the nitrogen in an exodentante. This, energetically
favorable state can occasionally be altered by coordination of the
metal cation, through conformational switching [28,29].
Furthermore, macrocycles can be described in terms of the shape
of the molecule and ring puckering. Also it is convenient to
describe a macrocyclic ligand by considering the number of atoms
in the inner macrocyclic ring and the approximate inner hole size.
Selected bond lengths, valence angles and torsion angles for the
synthesized ligands are listed in Table S2, and the molecular
2
70 °C with a mass loss of 8.5%. The mass loss of the first two ther-
mal events can be attributed to the loss of the nitrate group (calc.
1.6; found 11.1%). Afterwards, the TG curve shows continuous
1
weight loss between 273 and 550 °C accompanied by a strong
broad exothermic peak on the DSC curve corresponding to thermal
decomposition of the ligand. The residual mass (22.4%) is elemen-
tal silver as found by powder diffraction (calc. 19.5%, assuming that
the remaining solid is elemental Ag) [24]. The TG curve of AgmD2
exhibits thermal degradation in two steps. First step shows mass
loss of 12.6% and is accompanied by a sharp exothermic peak on
the DSC curve. This step can be attributed to the thermal decompo-
sition of two loosely bound nitrate anions (calc. 10.8%). The second
step occurs in the temperature range of 247–550 °C, with several
broad exothermic peaks detected on the DSC curve. This step cor-
responds to the thermal decomposition of the ligand and the third
(
bridging) nitrate group. The residual mass (18.2%) is elemental sil-
ver (calc. 18.6%). The melting points of the coordination polymers
were not observed and individual TG/DSC curves are given in ESI
(Figs. S8–S11).
The results of thermal analysis indicate importance of the
nitrate anion in the structure of the coordination polymers. As it
can be seen (Fig. 1), the nitrate group in AgmD1 decomposes at a
significantly lower temperature then the nitrate group in AgmD2.
The results of thermal analysis of thermally treated AgmD1, repre-
sented in Fig. S12, indicate absence of the nitrate anion in the ther-
mally treated compound. Thermal decomposition of the ligand is
shifted to a lower temperature (242–458 °C) in comparison to
the untreated compound, which may be caused by weaker connec-
tivity of the polymeric chains due to absence of the nitrate group.
From the results of IR spectroscopy of treated AgmD1 it can be sup-
posed that the polymeric structure of the compound is present (at
least partially) even without presence of the nitrate anion.
However, the powder diffraction data of thermally treated
AgmD1 display only diffraction maxima that are assigned to ele-
mental silver (Fig. S25) indicating that crystallinity of the complex
is lost and that partial decomposition occurs. In the case of AgmD2,
the polymeric structure is most probably destroyed upon thermal
Fig. 2. ORTEP plot of mD1 and mD2 with displacement ellipsoids of non-hydrogen
atoms drawn at the 50% probability level. A, B and C represent aromatic rings.

2
88
T. Bali ´c et al. / Inorganica Chimica Acta 435 (2015) 283–291
Fig. 3. Representation of crystal packing in mD2. Blue colored molecules are conformer 1 and red conformer 2.
with violet ellipses. Hydrogen atoms are omitted for clarity. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this
article.)
pÁ Á Áp interactions of benzene rings in conformer 2 is denoted
structures are represented in Fig. 2 (molecular structure of the con-
former 2 molecule is represented on Fig. S6).
Both molecules crystallize in the monoclinic crystal system
with Z = 4 and Z = 8 for mD1 and mD2, respectively. Both mole-
cules are tetradentante N
mD1) and 17 (mD2) atoms in the inner macrocyclic ring. The aver-
age hole size in mD1 is in the interval of 2.44–2.61 Å and 2.35–
.44 Å for mD2. The asymmetric unit of mD2 is composed of two
2 2
O macrocyclic Schiff bases with 18
(
2
symmetrically independent conformers, denoted as conformer 1
and conformer 2. The two conformers are different regarding the
orientation of the aliphatic chain and dihedral angles between
the benzene rings. Also, in conformer 2, the C18-C23 benzene ring
is disordered over two positions with an occupancy factor of
0
.52(2). In regard to the orientation of donor atoms the nitrogen
atoms are exo-oriented and oxygen atoms endo-oriented, in both
molecules. The distances between nitrogen atoms are almost iden-
tical in both macrocyles due to the rigidity of the m-phenylenedi-
amine precursor. As it can be seen from dihedral angles between
the benzene rings (Table 2), there is a more pronounced deviation
from planarity in mD1 then in mD2. The mD1 molecule is in the
partial-cone (saddle) conformation that is typical for some other
1
8-membered macrocyclic compounds [30]. The deviations from
planarity can also be seen from analysis of the puckering ampli-
tude of mD1 and mD2 (1.843(3) Å and 1.299(4), respectively)
[
31]. In both ligands the aliphatic chain is arranged in the trans
conformation.
In the crystal, the macrocyclic molecules are primarily linked
through
p
Á Á Á
p
, C–HÁ Á Á
p
and C–HÁ Á ÁN interactions. The described
deviations of the overall planarity in mD1 and mD2 have a signif-
icant impact upon the crystal structure arrangement. In mD1, the
molecules are linked along the crystallographic axis b by weak
C14–H14AÁ Á Á
p
(centroid of C) and C18–H18BÁ Á Á
p (centroid of B)
Fig. 4. (a) ORTEP plot of AgmD1 with displacement ellipsoids of non-hydrogen
atoms drawn at 50% probability level. Only the major dichloromethane solvent
molecule is shown. (b) Local coordination geometry of AgmD1 (T-shaped).
interactions. Due to flattening of the macrocyclic ring in mD2
(see dihedral angles in Table 2), the benzene rings are connected

T. Bali ´c et al. / Inorganica Chimica Acta 435 (2015) 283–291
289
via strong
p
Á Á Á
p
interactions along the crystallographic axis a.
Ag-N bond distances are identical (2.185(5) and 2.186(5) Å), thus
indicating strong coordination of the ligand to the metal center.
The nitrate group is loosely bound to the silver center with the
Ag-O distance of 2.537(6) Å. Oxygen atoms of ligand remain
endo-oriented and do not participate in coordination. There are
no significant changes in the conformational or geometrical
parameters of the macrocyclic ligand in comparison to free mD1.
Due to a slight deviation of the N1-Ag1-N2 angle from linearity
and a bowl shape of the macrocyclic ligand the polymeric chain is
not linear and can be described as a 1D zig-zag chain typical for
some other silver coordination polymers (Fig. 5a) [34].
These interactions are primarily observed between conformer 2
molecules (benzene ring C). Furthermore, conformer 1 molecules
are linked by weak C-HÁ Á ÁN interactions (C17-H17AÁ Á ÁN1) along
axis b. The same type of C-HÁ Á ÁN interaction is observed in con-
former 2 (C14A-H14DÁ Á ÁN2A). Conformer 1 and conformer 2 mole-
cules are linked through a series of weak van der Waals contacts
along the c-axis (Fig. 3). Hydrogen bond interactions of macrocyclic
ligand molecules are summarized in Table S3.
The Cambridge Structural Database [32] was searched for related
derivatives containing uncoordinated Schiff base macrocyclic
ligands containing benzene rings in order to compare crystal
packing peculiarities of the ligands. The search resulted with only
Two neighboring polymeric chains are connected through
nitrate group via a series of weak C–HÁ Á ÁO interactions along the
a-axis (light blue lines in Fig 5b). These interactions form a 2D rib-
bon-like network with empty spaces in which dichloromethane or
chloroform molecules are incorporated. The solvent molecules are
linked by C–HÁ Á ÁO and ClÁ Á ÁO interactions to the nitrate ion and
2
relevant hits [27,33] in which the molecules exhibit similar weak
C–HÁ Á Á and C–HÁ Á ÁN interactions as in mD1 and mD2.
p
3
3
.6. Crystal structure of the silver coordination polymers
ClÁ Á Á
p interactions (C1–C6 benzene ring) to the ligand molecule.
The hydrogen bond interactions in AgmD1 are given in Table S6.
.6.1. Crystal structure of AgmD1
X-ray analysis of AgmD1 has shown that the compound crystal-
lizes in monoclinic crystal system, non-centrosymmetric space
group P 2 . The crystal structure of AgmD1 is shown in
Fig. 4a and the selected bond lengths and angles are presented in
Table S4. The asymmetric unit is comprised of one silver atom,
one ligand, a coordinated nitrate anion molecule and disordered
dichloromethane and chloroform molecules in the ratio of
3.6.2. Crystal structure of AgmD2
2
1 1
2
1
The crystal structure of AgmD2 is shown in Fig. 6 and the
selected bond lengths and angles are presented in Table S5. The
asymmetric unit is composed of the Ag atom, one ligand molecule,
the monodentate nitrate anion and half of the bridging bidentate
nitrate anion. Each silver atom is coordinated by two ligand mole-
cules and two nitrate anions. The second ligand molecule is gener-
ated by symmetry of the inversion center ((i) Àx, Ày, Àz). This
symmetry related molecules form a metallacyclic ring along with
the two silver atoms. The metallacyclic ring is comprised of two
symmetrically related silver atoms, four imino nitrogen atoms
(donor atoms) and two m-phenylenediamine moieties. The separa-
0
.75:0.25 (Fig. 4a).
Each silver atom is coordinated by imino nitrogen atoms of two
neighboring ligand molecules and, in addition, with the oxygen
atom of the nitrate group (Fig. 4b). This mode of coordination pro-
duces an infinite, polymeric structure along the crystallographic
axis b. The coordination geometry around the silver atom can be
described as T-shaped (Fig. 4b), with the N1-Ag-N2 angle slightly
deviating from linearity (170.6(2)°) and with the N1-Ag1-O3 and
N2-Ag1-O3 angles almost orthogonal (96.4(2)° and 92.4(2)°). The
i
tion of two silver atoms (Ag1Á Á ÁAg1 , 7.5316(4) Å) is far beyond any
argentophilic interactions [35]. The polymeric structure is gener-
ated by connection of two metallacyclic rings through the bridging
Fig. 5. (a) Representation of 1D zig-zag chain in AgmD1 (dichloromethane, chloroform and hydrogen atoms are omitted for clarity). (b) Representation of C–HÁ Á ÁO and ClÁ Á ÁO
intermolecular interactions (light blue lines) of two neighboring polymeric chains and dichloromethane solvent molecules in AgmD1 (chloroform molecules are not
represented). View down the c-axis. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

2
90
T. Bali ´c et al. / Inorganica Chimica Acta 435 (2015) 283–291
Fig. 6. ORTEP plot of AgmD2 with displacement ellipsoids of non-hydrogen atoms
drawn at 50% probability level. (i) Àx, Ày, Àz; (ii) Àx, y, ½ À z.
Fig. 7. (a) Representation of 1D sinusoidal chain in AgmD2 (hydrogen atoms are
omitted for clarity) (b) Representation of C–HÁ Á ÁO intramolecular interactions
nitrate ion, approximately along the [1–1–3] crystallographic
direction. The local coordination environment around each silver
center is distorted tetrahedral, with the angles around the silver
atom ranging from 76.6(1)° to 123.0(1)°. The Ag-N (Ag1-N1
(
black lines) of neighboring polymeric chains in AgmD2. Silver atoms are
represented by spheres in 7a and 7b.
2
.316(2), Ag1-N2 2.349(3) Å) bond distances are considerably
elongated and the Ag-O(nitrate) (Ag-O3 2.4122(9), Ag-O5
.473(3) Å) are somewhat shorter in comparison to AgmD1 thus
Considering the intermolecular interactions, the oxygen atoms
of the nitrate anion act as hydrogen acceptors, and usually form
weak intra/intermolecular C–HÁ Á ÁO interactions with aromatics
that stabilize the 3D structure of the coordination polymers
[40–44], as the nitrate anion in AgmD1 and AgmD2.
2
indicating stronger binding of the nitrate anion to the metal center.
Nevertheless, both bond distances and angles are within the nor-
mal range and comparable to other tetrahedral silver complexes
[
36]. It should be noted that only conformer 2 of mD2 is present
in the structure of the silver complex. There are no significant
changes in geometrical parameters of the ligand in comparison
to the free conformer.
3.7. PXRD studies of the silver coordination polymers
The Ag-O(bridging)-Ag angle is 147.9(1)° and, therefore, the poly-
meric chain can be described as non-linear. As it is represented in
Fig. 7a the polymeric chain propagates in a 1D sinusoidal manner
The powder diffraction pattern of AgmD2 is consistent with
the simulated one based on the solved crystal structure thus
confirming the purity of sample (Fig. S23). The crystals of
AgmD1 decompose at room temperature since the solvent mole-
cules leave the crystal. This is further enhanced by grinding the
single crystals for powder diffraction, therefore the diffraction
pattern is poorly resolved with low intensity peaks and it was
not possible to confirm purity of the bulk material by this
method (Fig. S24).
[
37].
Within the crystal structure, the two neighboring sinusoidal
chains are interconnected by a series of weak C–HÁ Á ÁO interactions
along the crystallographic c axis that involve monodentate nitrate
groups. Furthermore, the bridging nitrate groups and ether oxygen
atoms also participate in the intermolecular arrangement by a ser-
ies of C–HÁ Á ÁO interactions along the crystallographic b-axis
(Fig. 7b, Table S7). These interactions are stacking molecules in
the crystal rather densely, so there are no solvent accessible voids,
unlike in the case of AgmD1.
4. Conclusions
In addition, it is appropriate to describe the role of the nitrate
anion in long-range structural order of the coordination polymers.
Nitrate anion has the ability to act as a monodentate and a poly-
dentate ligand, as in AgmD1 and AgmD2, respectively. It can also
function as an intermolecular linkage between discrete polymeric
chains that can influence long-range order and properties (i.e.,
porosity) of coordination polymers and MOFs [38]. Recently, it
was reported that the nitrate anion can build polymeric structures
via hydrogen bond interactions which additionally expand its role
in design of coordination polymers [39].
2 2
Two N O -donor macrocyclic Schiff bases mD1 and mD2 were
prepared and their reactions with silver nitrate led to the forma-
tion of silver coordination polymers, AgmD1 and AgmD2. The pre-
pared polymers are unique examples of coordination polymers
with macrocycles containing this type of donor set atoms. The sin-
gle crystal structure studies revealed different mode of coordina-
tion around silver atoms, linear and tetrahedral for AgmD1 and
AgmD2, respectively. The differences in coordination behavior
and conformation of the ligands subsequently influence the topol-
ogy of the polymeric chains.

T. Bali ´c et al. / Inorganica Chimica Acta 435 (2015) 283–291
291
[
[
16] M.C. Burla, R. Caliandro, M. Camalli, B. Carrozzini, G.L. Cascarano, L. DeCaro, C.
Giacovazzo, G. Polidori, R. Spagna, J. Appl. Crystallogr. 38 (2005) 381.
17] L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837.
Appendix A. Supplementary material
CCDC 1039600–1039603 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
http://www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.ica.2015.07.016.
[18] G.M. Sheldrick, Acta Crystallogr. A 64 (2008) 112.
[19] A.L. Spek, Acta Crystallogr. A 46 (1990) 34.
[
20] A.L. Spek, PLATON: A Multipurpose Crystallographic Tool, Ultrecht University,
Ultrecht, The Netherlands, 1998.
21] C.F. Macrae, P.R. Edgington, P. McCabe, E. Pidcock, G.P. Shields, R. Taylor, M.
Towler, J. Van der Streek, J. Appl. Crystallogr. 41 (2008) 466.
22] G.A. Larikova, VINITI 575–82 (1981) 315.
23] C.J. Lin, W.S. Hwang, M.Y. Chiang, Polyhedron 20 (2001) 3275.
24] S. Hamamci, V.T. Yilmaz, W.T.A. Harrison, Z. Naturforsch. 60b (2005) 978.
25] K.M. Park, I. Yoon, Y.H. Lee, S.S. Lee, Inorg. Chim. Acta 343 (2003) 33.
[
[
[
[
[
References
[26] R.D. Hancock, Chem. Rev. 89 (1989) 1875.
[
27] V. Reyes-Márquez, M. Sánchez, H. Höpf, K.O. Lara, J. Inclusion Phenom.
Macrocyclic Chem. 65 (2009) 305.
[
1] L.F. Lindoy, The Chemistry of Macrocyclic Ligand Complexes, Cambridge
University Press, 1989.
[
[
28] L.F. Lindoy, Pure Appl. Chem. 61 (1989) 1575.
29] K.R. Adam, K.P. Dancey, A.J. Leong, L.F. Lindoy, B.J. McCool, M. McPartlin, P.A.
Tasker, J. Am. Chem. Soc. 110 (1988) 8471.
[
[
2] P.A. Vigato, S. Tamburini, Coord. Chem. Rev. 248 (2004) 1717.
3] F. Faridbod, M.R. Ganjali, R. Dinarvand, P. Norouzi, S. Riahi, Sensors 8 (2008)
[
[
[
[
[
[
[
[
30] K. Cottet, P.M. Marcos, P.J. Cragg, Beilstein J. Org. Chem. 8 (2012) 201.
31] D. Cremer, J.A. Pople, J. Am. Chem. Soc. 97 (1975) 1354.
32] F.H. Allen, Acta Crystallogr. Sect. B 58 (2002) 380.
1
645.
[
[
[
[
[
[
4] L.F. Lindoy, G.V. Meehan, I.V. Vasilescu, H.Y. Kim, J.E. Lee, S.S. Lee, Coord. Chem.
Rev. 254 (2010) 1713.
5] I.M. Vasilescu, D.S. Baldwin, D.J. Bourne, J.K. Clegg, F. Li, L.F. Lindoy, G.V.
Meehan, Dalton Trans. 40 (2011) 8675.
33] T. Hokelek, E.E. Kaya, Z. Kilic, Online 57 (2001) 309.
34] A.Y. Robin, K.M. Fromm, Coord. Chem. Rev. 250 (2006) 2127.
35] P. Pyykko, F. Mendizabal, Chem. Eur. J. 3 (1997) 1458.
36] S.M. Cortez, R.G. Raptis, Coord. Chem. Rev. 169 (1998) 363.
37] A.N. Khlobystov, A.J. Blake, N.R. Champness, D.A. Lemenovskii, A.G. Majouga,
N.V. Zyk, M. Schroder, Coord. Chem. Rev. 222 (2001) 155.
38] L. Hashemi, A. Morsali, O. Buyukgungorb, New J. Chem. 38 (2014) 3187.
39] G.A. Santillan, C.J. Carrano, Dalton Trans. 33 (2009) 6599.
40] K. Pandurangan, S. Gallagher, G.G. Morgan, H. Muller-Bunz, F. Paradisi
Metallomics 2 (2010) 530.
6] H. Zhou, Z.H. Peng, Z.Q. Pan, Y. Song, Q.M. Huang, X.-L. Hu, Polyhedron 26
(
2007) 3233.
7] I.M. Vasilescu, D.J. Bourne, J.K. Clegg, F. Li, L.F. Lindoy, G.V. Meehan, Supramol.
Chem. 24 (2012) 448.
8] M. Thirumavalavan, P. Akilan, P. Amudha, M. Kandaswamy, Polyhedron 23
[
[
[
(
2004) 519.
9] P.A. Vigato, V. Peruzzo, S. Tamburini, Coord. Chem. Rev. 256 (2012) 953.
[
[
10] K. Zhang, C. Jin, Y. Sun, F. Chang, W. Huang, Inorg. Chem. 53 (2014) 7803.
11] W. Huang, S. Gou, D. Hu, S. Chantrapromma, H.K. Fun, Q. Ming, Inorg. Chem. 40
[
[
[
[
41] S.L. Kuang, H.Y. Li, D.B. Dang, X.J. Pan, Synth. React. Inorg. Met.-Org.,Nano-
Met.Chem. 42 (2012) 59.
42] G.A. Bowmaker, E.S. Marfuah, B.W. Skelton, A.H. White, Inorg. Chim. Acta 358
(
2001) 1712.
[
[
[
[
12] S. Park, S.Y. Lee, K.M. Park, S.S. Lee, Acc. Chem. Res. 45 (2012) 391.
13] S. Kim, E. Lee, S.Y. Lee, S.S. Lee, L.F. Lindoy, Inorg. Chim. Acta 417 (2014) 171.
14] STARe, Software 10.0, 2009, Mettler-Toledo GmbH.
15] Oxford Diffraction, Oxford Difraction Ltd., Xcalibur CCD system, CRYSALIS
Software system, Version 1.171.34.44, 2010.
(
2005) 4371.
43] G.A. Bowmaker, E.M. Nitiatmodjo, B.W. Skelton, A.H. White, Inorg. Chim. Acta
58 (2005) 4327.
44] S.M.J. Wang, T.C.W. Mak, Polyhedron 28 (2009) 2684.
3