Binuclear and polymeric Zn(II) and Cd(II) coordination compounds with chromophore N-((pyridin-4-yl)methylene)benzene-1,4-diamine obtained in situ: Preparation, structural and spectroscopic study

Article abstract of DOI:10.1016/j.ica.2019.03.034

Four coordination compounds, that include the discrete binuclear complex [Zn(H₂O)₄(bda4Py)]₂(SO₄)₂ (1), two isomorphous one-dimensional coordination polymers, {[Zn(NO₃)₂(bda4Py)₂]·2H₂O}_n (2) and {[Cd(NO₃)₂(bda4Py)₂]·2H₂O}_n (3), and one two-dimensional coordination polymer {[Cd(bda4Py)₂(dpa)₂]·2H₂O}_n (4) [where bda4Py = N-((pyridin-4-yl)methylene)benzene-1,4-diamine, H₂dpa = diphenic acid, as a potential anionic competitor ligand having two carboxylic groups] were obtained as the products of partial hydrolysis of the ligand N¹,N⁴-bis(pyridin-4-ylmethylene)-benzene-1,4-diamine (bda4bPy) in the reaction conditions. Single crystal X-ray data reveal that N-((pyridin-4-yl)methylene)benzene-1,4-diamine acts as a bidentate linker between two metal centers through nitrogen atoms of pyridino- and amino-groups. The additional stabilization of the crystalline solids 1–4 is provided via hydrogen bonds. N-((pyridin-4-yl)methylene)benzene-1,4-diamine (bda4Py) was also obtained by direct synthesis, and two ligands (bda4bPy and bda4Py) were characterized in the solid state and in solution by spectroscopic (FTIR, UV–vis, NMR) methods. Luminescence studies for the reported compounds are also documented.

Full text of DOI:10.1016/j.ica.2019.03.034

Accepted Manuscript
Binuclear and polymeric Zn(II) and Cd(II) coordination compounds with chro-
mophore N-((pyridin-4-yl)methylene)benzene-1,4-diamine obtained in situ:
preparation, structural and spectroscopic study
Vasile Lozovan, Victor Ch.Kravtsov, Eduard B. Coropceanu, Petre Rotaru,
Anatolii V. Siminel, Marina S. Fonari
PII:
S0020-1693(19)30228-2
https://doi.org/10.1016/j.ica.2019.03.034
ICA 18839
DOI:
Reference:
Inorganica Chimica Acta
To appear in:
Received Date:
Revised Date:
Accepted Date:
17 February 2019
17 March 2019
20 March 2019
Please cite this article as: V. Lozovan, V. Ch.Kravtsov, E.B. Coropceanu, P. Rotaru, A.V. Siminel, M.S. Fonari,
Binuclear and polymeric Zn(II) and Cd(II) coordination compounds with chromophore N-((pyridin-4-
yl)methylene)benzene-1,4-diamine obtained in situ: preparation, structural and spectroscopic study, Inorganica
Chimica Acta (2019), doi: https://doi.org/10.1016/j.ica.2019.03.034
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Binuclear and polymeric Zn(II) and Cd(II) coordination compounds with chromophore N-
((pyridin-4-yl)methylene)benzene-1,4-diamine obtained in situ: preparation, structural and
spectroscopic study
Vasile LOZOVAN,a,b Victor Ch.KRAVTSOV,c Eduard B. COROPCEANU,a,b
Petre ROTARU,d Anatolii V. SIMINELc and Marina S. FONARIc,*
a Institute of Chemistry, 3 Academiei str.,Chisinau, Republic of Moldova
b Tiraspol State University, 5 Iablocikin str., Chisinau, Republic of Moldova
E-mails: lozovanvasile90@gmail.com; ecoropceanu@yahoo.com
c Institute of Applied Physics, 5 Academiei str., Chisinau, Republic of Moldova
E-mails: kravtsov@phys.asm.md; ansi@inbox.ru; fonari.xray@phys.asm.md;
d University of Craiova, Faculty of Sciences, 13 A.I. Cuza str., Craiova, Romania
E-mail: petrerotaru@yahoo.com
Abstract. Four coordination compounds, that include the discrete binuclear complex [Zn(H2O)4(bda4Py)]2(SO4)2 (1),
two isomorphous one-dimensional coordination polymers, {[Zn(NO3)2(bda4Py)2]·2H2O}n (2) and
{[Cd(NO3)2(bda4Py)2]·2H2O}n (3), and one two-dimensional coordination polymer {[Cd(bda4Py)2(dpa)2]·2H2O}n
(4) [where bda4Py = N-((pyridin-4-yl)methylene)benzene-1,4-diamine, H2dpa = diphenic acid, as a potential anionic
competitor ligand having two carboxylic groups] were obtained as the products of partial hydrolysis of the ligand
N1,N4-bis(pyridin-4-ylmethylene)-benzene-1,4-diamine, (bda4bPy) in the reaction conditions. Single crystal X-ray
data reveal that N-((pyridin-4-yl)methylene)benzene-1,4-diamine acts as a bidentate linker between two metal centers
through nitrogen atoms of pyridino- and amino-groups. The additional stabilization of the crystalline solids 1-4 is
provided via hydrogen bonds. N-((pyridin-4-yl)methylene)benzene-1,4-diamine (bda4Py) was also obtained by
direct synthesis, and two ligands (bda4bPy and bda4Py) were characterized in the solid state and in solution by
spectroscopic (FTIR, UV–vis, NMR) methods. Luminescence studies for the reported compounds are also
documented.
Key words: Zn; Cd; coordination polymer; Schiff base ligand; crystal structure; spectroscopic studies
Introduction
Nowadays Schiff bases and their numerous azo derivatives are extensively studied owing to
their potential applicability as selective receptors in optical sensors [1-4]. Due to their high metal
affinity, these compounds demonstrate rich coordination chemistry acting as chelating and bridging
1

ligands that allows performing the targeted synthesis of chelate and molecular, mono-, bi- and
polynuclear, homo- and heterometallic structures [5]. The optical response of azo groups towards
Ni(II), Co(II), Cu(II), Pb(II), Hg(II), Zn(II) and Cd(II) metal ions was registered in DMSO
solution by UV–vis spectroscopy [6]. The Zn(II) complexes with azomethine ligands in different
solvents demonstrated excitation-dependent emission, which allowed tuning the emission color
in a wide range using the variation in the excitation light and in the solvents [7]. The
photoluminescent properties for these ligands and their metal complexes are successfully
combined with their antioxidant and cytotoxic activity, that explains another aspect of the
relentless interest to this class of organic compounds [6,8].
Being interested in the solid crystalline materials with the ligand-based emission properties
[9,10] alongside with the others [11-13] we have recently reported the crystal structures and
emissive properties for Zn(II) and Cd(II) one-dimensional (1D) coordination polymers (CPs)
with two azines of the N,N' type, 1,2-bis(pyridin-3-ylmethylene)-hydrazine, and 1,2-
bis(pyridin-4-ylmethylene)hydrazine as bridging ligands [14]. These long aromatic molecules
with the conjugated system of alternating С=N and N–N bonds can coordinate transition metal
ions by the nitrogen atoms of both terminal pyridine and azine fragments [15] and participate in
hydrogen bonds in the presence of strong proton–donor agents [16].
So far our interest is further focused on a longer rigid π-conjugated linker, N1,N4-bis(pyridin-
4-ylmethylene)-benzene-1,4-diamine (bda4bPy), whose luminescence properties in the pure
form and in the complexes have been reported [1,17]. The examination of the Cambridge
Structural Database (CSD version 5.40, November 2018) has revealed very few examples
containing bda4bPy ligand coordinated to the metal cations that include Pb(II) [17], Zn(II) [18-
20], and Co(II) [20]. The reported sources indicated that the CPs generated from bda4bPy may
display intense photoluminescence properties because of its structural rigidity that effectively
decreases internal conversion and radiationless deactivation [1, 17]. On the other hand,
Masoomi et al. have reported the unique to the best of our knowledge 3D network
.
[Zn(oba)(bda4bPy)0.5]n (DMF)z (TMU-6) (where oba = 4,4’-oxy-dibenzoate) with large pores
and improved catalytic activity achieved through functionalization of MOF pore walls with
azine groups enabled greater interaction between the walls and substrate molecules [19].
The scare information about CPs with the ligand bda4bPy, has motivated our research and
synthetic attempts have been undertaken to obtain new Zn(II) and Cd(II) CPs with this ligand.
However, instead, four coordination compounds [Zn(H2O)4(bda4Py)]2(SO4)2
{[Zn(NO3)2(bda4Py)2]·2H2O}n ), {[Cd(NO3)2(bda4Py)2]·2H2O}n ),
[Cd(bda4Py)2(dpa)2]·2H2O ( ) [where bda4Py=N-((pyridin-4-yl)methylene)benzene-1,4-
(
1),
(
2
(3
and
4
diamine, dpa = anion of diphenic acid] containing the ligand bda4Py were obtained as the
products of partial hydrolysis of the ligand bda4bPy in the reaction medium, that is in line with
2

the reported examples for this class of organic molecules [21-34]. A similar situation when the
reaction was accompanied by the partial hydrolysis of the ligand was documented for the
positional isomer of bda4Py, N-(2-pyridylmethylene)benzene-1,4-diamine [21].
Herein we report the synthesis, crystal structures and spectroscopic investigation of four
coordination compounds containing the chromophore bda4Py, obtained as the product of
hydrolization of chromophore bda4bPy in situ in the reaction medium. Our choice of
dicarboxylic diphenic acid as a competitive ligand to small inorganic anions was justified by its
excellent complexing ability towards the d10 metals in general and, in particular, by the reported
series of five mixed-ligand coordination polymers with the structural anlogues of bda4bPy,
bis(4-pyridylmethyl)piperazine and its positional isomer, bis(3-pyridylmethyl)piperazine [35].
Herein the direct synthesis of the ligand bda4Py is also reported together with the optical
properties of the solutions of both ligands. The coordination compounds 1-4 were characterized
by FTIR spectroscopy and single crystal X-ray diffraction, the limits of thermal stabilities for
bda4bPy, bda4Py and
1 were determined by TGA method.
Experimental
Materials and Methods. Starting inorganic salts, 1,4-phenylenediamine dihydrochloride, 4-
pyridinecarboxaldehyde and solvents were obtained from commercial sources (Sigma-Aldrich)
and were used without further purification. The IR spectra were obtained in ATR on a FTIR
Spectrum-100 Perkin Elmer spectrometer in the range of 650-4000 cm-1. Elemental analysis was
performed on a vario EL III Element Analyzer. The thermal analysis of the ligands bda4bPy,
bda4Py and complex
1 was performed on a PerkinElmer Analyzer derivatograf in the
temperature range of 20−1000 °C under a flow of air with a heating rate of 10 °C min-1. NMR-
1
spectra were recorded on a Bruker spectrometer at 400.13 MHz for H and 100.61 MHz for 13C
in DMSO-d6 using TMS as an internal reference. Chemical shifts (δ) are reported in parts per
1
million (ppm) and are referenced to the residual non-deuterated solvent peak (2.49 for H and
39.70 for 13C). UV-Vis measurements were carried out at T60 UV/Vis spectrophotometer. Solid
state emission spectra were recorded using a pulse nitrogen laser (λexc = 337.1 nm) at 300 K.
The excitation pulse duration was 15 ns, the repetition frequency was 50 Hz, and the pulse
energy was 0.2 mJ. The emission was detected with a FEU-79 instrument (multialkaline
photocathode Sb(Na2K) with the adsorbed cesium layer on the surface, characteristic of the S20
type). The intrinsic time of the detecting system was 20 ns. The afterglow duration (at 300 K)
for all studied compounds was shorter than the time resolution of the detecting system.
Crystallographic Studies. Diffraction measurements for 1-4 were carried out on an Xcalibur E
diffractometer equipped with CCD area detector and a graphite monochromator utilizing MoKα
radiation at room temperature. Final unit cell dimensions were obtained and refined on an entire data

set. All calculations to solve the structures and to refine the models proposed were carried out with the
programs SHELXS97 and SHELXL2014 [36,37]. Hydrogen atoms attached to carbon atoms were
positioned geometrically and treated as riding atoms using SHELXL default parameters with
Uiso(H)=1.2Ueq(C), the O- and N-bounded H–atoms were found from differential Fourier maps at the
intermediate stages of the refinement and their positions were constrained using the DFIX instructions
in SHELXL [d(O,N)-H=0.86 Å, d(H···H)=1.46 Å) for hydroxyl and amino-groups. Compounds 2 and
3 were refined as non-merohedral two-component twins with the twinning matrix [-1.0027 0.0019 -
0.8746 -0.0014 -1.0001 -0.0019 0.0017 -0.0021 1.0005] and the component ratio 0.6383 : 0.3617 for
2; and the twinning matrix [1.0064 0.0015 0.8745 -0.0003 -1.0035 0.0001 -0.0012 -0.0002 -1.0042]
and the component ratio 0.89997 : 0.10003 for 3. Compound 4 that crystallizes in the
noncentrosymmetric Iba2 space group was refined as a racemic twin with the component ratio 0.537 :
0.463. The pyridine ring in the bda4Py molecule is disordered over two positions which were refined
with the 0.64(2) and 0.36(2) probabilities. Three localised outer sphere water molecules are disordered
around a 2-fold rotation axis, two of them have site occupancy factor 0.5 and one of them was refined
with occupancy factor 0.250, for all three molecules the hydrogen atoms were not found. The X–ray
data and the details of the refinement for 1-4 are summarized in cif files. The Figures were produced
using Mercury [38]. The solvent accessible voids (SAVs) were calculated using PLATON [39].
Crystallographic data (cif files) for 1–4 have been deposited with the Cambridge
Crystallographic Data Center, CCDC Nos. 1893503-1893506.
Synthesis
Synthesis of N1,N4-bis(pyridin-4-ylmethylene)-benzene-1,4-diamine. Bda4bPy was first
synthesized by Grasso et (1981) [40]. 1,4-Phenylenediamine dihydrochloride (3.84 g, 21 mmol)
was dissolved in a beaker in 200 mL of water. Then 4-pyridinecarboxaldehyde (5 mL, 53 mmol)
was added under stirring. To this mixture was added Na2CO3 (≈ 2.3 g), until the pH reached 7-
8. The solution was further stirred for 3 hours at a temperature 70 °C. Then the sediment was
filtered off through a glass Buchner funnel, then stirred again in water and filtered for
purification. Reaction yield: 87 %. The reported analytical data correspond to the literature data
[1]. Anal. Calc. for C18H14N4: C, 75.50; H, 4.93; N, 19.57. Found: C, C, 75.49; H, 4.90; N, 19.54
%. IR-ATR (cm-1): 3054 m, 3031 m, 2889 m, 1631 m, 1619 m, 1599 s, 1551 s, 1487 s, 1411 s,
1324 s, 1192 s, 1100 m, 890 s, 834 vs, 814 vs, 796 s; 1H NMR: 8.76, 8.75, 7.87, 7.45; 13C NMR:
159.46, 150.94, 149.6, 142.9, 122.9, 122.69.
Synthesis of N-((pyridin-4-yl)methylene)benzene-1,4-diamine. Bda4Py was obtained under
the same conditions as bda4bPy ligand, except that the molar ratio of aldehyde to diamine was
1:1. As a result, an orange precipitate was obtained. Reaction yield: 85 %. The compound is
4

soluble in MeOH, EtOH, DMF, DMSO, insoluble in water. The crystalline product was also
obtained. To obtain it, 1,4-phenylenediamine dihydrochloride (0.5 g, 2.76 mmol) was dissolved
in 40 mL of EtOH, to which NaOH (0.22 g, 5.52 mmol) then was added. The solution was stirred
for 20 minutes, filtered off, then 4-pyridinecarboxaldehyde (0.2 mL, 2.1 mmol) was added
without stirring. Over ~ 5 min in solution, orange crystals were formed. Anal. Calc. for
C12H11N3: C, 73.07; H, 5.62; N, 21.30. Found: C, 73.02; H, 5.79; N, 21.28 %. IR-ATR (cm-1):
3434 m, 3315 m, 3179 m, 3080 m, 3030 m, 2879 m, 1635 s, 1618 s, 1574 vs, 1540 vs, 1507 vs,
1411 s, 1308 s, 1288 s, 1158 s, 1132 m, 941 m, 832 vs, 793 m; 1H NMR: 8.68, 8.65, 7.7, 7.23,
6.63, 5.44; 13C NMR: 152.02, 150.07, 149.57, 143.95, 139.7, 123.7, 122.06, 114.46.
The synthetic pathways to the bda4bPy and bda4Py ligands are shown in Scheme 1.
(a)
(b)
Scheme 1. Synthesis of the ligands bda4bPy and bda4Py (a) and view of their bulk (b) bda4bPy (up) and
bda4Py (down).
Synthesis of [Zn(H2O)4(bda4Py)]2(SO4)2 (1). A solution of ZnSO4·7H2O (28 mg, 0.1 mmol) dissolved in
5 mL of water was added to a test tube. Then carefully 2 mL of H2O/EtOH (1:1) solution were added
following the ethanolic solution of bda4bPy ligand (28.6 mg, 0.1 mmol) that was added carefully. After
about a week, crystals in the form of orange-red plates were precipitated from solution. Yield: 62 %. Anal.
Calc. for ZnC24H30N6O12S2: C, 39.81; H, 4.18; N, 11.61; O, 26.52; S, 8.86. Found: C, 39.80; H, 4.16; N,
11.60; O, 26.49; S, 8.84. %. IR-ATR (cm-1): 3236 vs, 3183 vs, 1667 m, 1623 m, 1615 s, 1588 s, 1549 m,
1507 m, 1423 m, 1264 m, 1107 vs, 1035 vs, 983 vs, 956 s, 839 s, 828 m, 787 w.
Synthesis of {[Zn(NO3)2(bda4Py)2].2H2O}n
mmol), then this solution was added to a test tube. Then carefully CH2Cl2/EtOH (1:1, 2 mL) solution was
(2). In 6 mL of CH2Cl2 was dissolved bda4bPy (28.6 mg, 0.1

added. Then 5 mL of ethanolic solution of Zn(NO3)2·6H2O (30 mg, 0.1 mmol) was carefully added. After
about a week, crystals in the form of pale red plates were formed in solution. Yield: 38 %. Anal. Calc. for
ZnC24H26N8O8: C, 46.50; H, 4.23; N, 18.08; O, 20.65. Found: C, 46.48; H, 4.20; N, 18.07; O, 20.63 %. IR-
ATR (cm-1): 3280 m, 3246 m, 3211 m, 3151 m, 2954 m, 2922 m, 2902 m, 1647 w, 1617 s, 1590 s, 1551 w,
1510 w, 1420 vs, 1312 vs, 1292 vs, 1254 vs, 1038 vs, 841 m, 814 s, 780 m.
Synthesis of {[Cd(NO3)2(bda4Py)2].2H2O}n
(3). The compound was also obtained by diffusion method,
but a barrier was used to separate the solution of the ligand from the salt solution. A porous membrane glass
filter was used for this. In a small chamber of the filter was added the solution of Cd(NO3)2·4H2O (18 mg,
0.6 mmol) in 8 mL of water then the hole was closed with a stopper. In the large chamber was added the
bda4bPy ligand solution (17 mg, 0.6 mmol) in 30 mL of EtOH after which it was covered with parafilm. The
filter was left in the horizontal position. After about two weeks, on the porous membrane pale red crystals
were formed. Yield: 52 %. Anal. Calc. for ZnC24H26N8O8: C, 43.22; H, 3.93; N, 16.80; O, 19.19. Found: C,
43.19; H, 3.90; N, 16.77; O, 19.16 %. IR-ATR (cm-1): 3454 w, 3305 m, 3249 m, 3157 m, 2953 m, 2924 m,
2854 m, 1651 w, 1623 m, 1614 m, 1593 s, 1550 w, 1510 m, 1428 vs, 1413 vs, 1316 vs, 1291 vs, 1258 vs,
1215 s, 1161 m, 1050 m, 1016 s, 987 s, 967 s, 839 s, 812 s, 782 s.
Synthesis of {[Cd(bda4Py)2(dpa)2].2H2O}n
diphenic acid (dpa, 22 mg) neutralized with NaOH were added to a test tube, then proceeded as in (
(4). 6 mL of Cd(NO3)2·4H2O solution (30 mg, 0.1 mmol) and
1
)
synthesis. After about one week, pale orange-red crystals were formed in solution. Yield: 32 %. Anal. Calc.
for CdC38H34N6O6: C, 58.28; H, 4.38; N, 10.73; O, 12.26. Found: C, 58.25; H, 4.37; N, 10.71; O, 12.23 %.
IR-ATR (cm-1): 3373 m, 3304 m, 3168 m, 2953 m, 2923 m, 2854 m, 1610 m, 1587 s, 1530 vs, , 1507 vs,
1455 s, 1439 s, 1405 vs, 1251 m, 1048 m, 859 s, 834 m, 748 vs, 683 s.
Results and discussion
Characterization of chromophores bda4bPy and bda4Py
The chemical purity of the chromophores bda4bPy and bda4Py was confirmed by IR and NMR spectra
(Figures S1-S5). NMR values (Figure 1) have been established on the basis of literature data [41] taking into
1
account the electronic effects of substitutes [41a, 41b]. In the H NMR spectrum of the bda4Py molecule
there are 6 signals. Four signals are doublets and belong to the protons in the pyridine and phenyl moieties.
Two signals are singlets and belong to the protons of the amino group δH(NH2) and the azomethine group
13
δH(CH=N) which is close to the signal of the protons neighboring to the pyridine nitrogen atom. The C
NMR spectrum shows 8 signals. The lower value of the chemical shift for the carbon nucleus of the
azomethine group δC(C=N) is due to the fact that this linkage is conjugated to the pyridine moiety, which is
also confirmed by the IR spectrum.
6

Fig. 1. Structural formula for compounds bda4bPy (left) and bda4Py (right) with indication of 1H NMR
(up) and 13C NMR (down) numerical values of the signals in the molecules.
The reactions between the synthesized ligand bda4bPy and zinc sulfate, and zinc and cadmium nitrate salts
were aimed to obtain the corresponding CPs with the bda4bPy in a function of the potential bidentate
mediator. However, in all cases the final crystalline products 1-4 whose crystal structures were unambigously
identified by single crystal X-ray diffraction method, contain the chromophore, 4-((pyridin-4-
ylmethylene)amino)aniline (bda4Py) as a product of hydrolysis of bda4bPy in the reaction conditions. The
hydrolysis of Schiff bases is an important reaction of biochemical and biological interest. The effect of
hydroxonium, hydroxide and metal ions on the hydrolysis of Schiff bases has been studied [24]. It has been
established that metal ion can play a determining role in stabilizing or destabilizing of the coordinated Schiff
base [26,27]. Nickel(II) and copper(II) were documented to catalyse the hydrolysis of the C=N bond of the
Schiff bases with the concomitant formation of the metal complex with the amine [23, 25]. This is explained
by the effect of chelation and formation of stable or less stable cycles involving the metal ion and the nitrogen
atom of the C=N group [23, 25,26]. The bda4bPy ligand can not form chelating cycles, otherwise, this
molecule can coordinate to the metal in bidentate-bridging or monodentate modes. It is worth noting that
stability of the azomethinic C=N bond represents an important factor in the synthesis of CPs with Schiff
base bridge ligands. For example, bridge ligands of the azide class of the bis N,N-donor type [31-33] have
been extensively used in the synthesis of CPs due to stability of the azine moiety (−HC=N−N=CH−). Upon
complexation to the metal, when the nitrogen of the Schiff base becomes coordinated, the electronic cloud
is reorientated in the direction of the metal ion and away from the C=N double bond. The azomethine bond
becomes polarized (>C+–N-–), so the reaction with a variety of nucleophilic reagents occurs easier [28, 29].
One class of such reactions is a hydrolysis of Schiff bases, those involving water as a nucleophilic agent [29,
30].
Single crystal structures and thermal stability.
Compound [{Zn(H2O)4(bda4Py)}2][SO4]2
Pbca (Table 1). The asymmetric unit comprises Zn(II) cation, sulfate anion, bda4Py and water ligands in the
1:1:1:4 molar ratio. The ionic crystal structure is built of the centrosymmetric binuclear aqua cations,
[{Zn(H2O)4(bda4Py)}2]4+ and outersphere sulfate-anions. In the centrosymmetric cation the metal centers
1 crystallizes in the centrosymmetric orthorhombic space group
1

are linked by the two bda4Py ligands coordinated to the metal in the head-to-tail mode, Zn(II) cation has a
distorted octahedral coordination surrounding with the N2O4 donors coming from two bda4Py ligands and
four water molecules, the range of Zn-O distances being 2.077(3)-2.148(3) Å, Zn-N distances are 2.148(3)
and 2.241(3) Å (Fig. 2a, Table 2). The bidentate-bridging bda4Py ligand adjusts the concave shape with the
bending angle between the pyridine and phenyl rings of 12.77 . The metal-metal separation in the binuclear
cation across the ligand is 13.272(1) Å. The sulfate anions display in the metal’s second coordination sphere
being linked with the binuclear cation through OH(H2O)···O(SO4)2- and NH(NH2) ···O(SO4)2- hydrogen
bonds with participation of the coordinated water molecules and amino-group of bda4Py ligand (Table 3).
Each Zn(II) cation is surrounded by five SO42- anions, and each anion is imprisoned in the aqua hydrophylic
cages from 5 neighboring cations (Fig. 2b); all four coordinated water molecules and amino group act as
double H-donors, while oxygen atoms of the SO42- anion act as the double (O2, O3) and triple (O1, O4) H-
acceptors and participate in the extended 3D H-bonded network in the crystal (Fig. 2c).
(a)
(c)
(b)
Fig. 2. Fragments of structure 1. (a) View for the formula unit in 1, thermal ellipsoids are shown with
the 50 % probabilities; (b) environment of the sulfate anion in the crystal; (c) fragment of crystal packing
with indication of hydrogen bonds.
Compounds {[Zn(NO3)2(bda4Py)2]·2H2O}n (
(Table 1) that crystallize in the same centrosymmetric monoclinic P2/c space group in the form of 1D
polymeric chains. Due to the similarities in the crystal structures, only will be further discussed in details.
The Zn(II) coordination environment in is shown in Fig. 3a. The metal atom resides on the two-fold axis,
2) and {[Cd(NO3)2(bda4Py)2]·2H2O}n (3) are isomorphs
2
2
and has an N4O2 octahedral coordination surrounding that originates from four bda4Py ligands and two
nitrate anions. Zn-O bond distance is equal to 2.185(2) Å, Zn-N distances are equal to 2.137(2) and 2.240(2)
Å. For compound
3 Cd-O bond distance is equal to 2.369(5) Å, Cd-N distances are equal to 2.328(5) and
2.405(5) Å (Table 2). Nitrate anion coordinates as a terminal monodentate ligand; bda4Py ligand coordinates
8

in a bidentate-bridging mode, via both pyridine and amino-group N-binding sites, thus providing the joining
of successive metal atoms in the coordination polymeric chain (Fig. 3b). Although the twisting of bda4Py
molecule in 2-3 is a bit larger than in
of 20.3 , the metal···metal separation remains virtually the same in
13.610 Å in . The coordination chain is running along the [201] direction in the crystal. The hydrogen-
1
as indicates the dihedral angle between the phenyl and pyridine rings

2
being 13.378 Å, and a bit longer as
3
bonding system includes two NH(NH2)···O(NO3) and two identical OH(H2O)···N(bda4Py-azine) hydrogen
bonds (Table 3). The coordinated nitro-group participates in the NH2···O hydrogen bonds between the
coordination chains packed along the crystalolographic c axis (Fig. 3b). The coordination chains are
additionally interlinked via bridging water molecules that reside on a two-fold axis (Fig. 3c, Table 3).
Table 1. Crystal data and structure refinement parameters for 1-4
Compound
1
2
3
4
Empirical formula
C24H38N6O16S2Z C24H24N8O7Z C24H24CdN8O C26H23.50CdN3O6.25
n2
861.46
Orthorhombic
Pbca
n
7
Formula weight
Crystal system
Space group
601.88
Monoclinic
P2/c
648.91
Monoclinic
P2/c
590.38
Orthorhombic
Iba2
Unit cell dimensions
a,Å
b,Å
c,Å
9.6998(6)
9.7516(6)
36.092(2)
90
3413.9(3)
4
13.7846(17)
8.2108(8)
11.7428(15)
111.784(13)
1234.2(3)
2
14.0355(10)
8.1396(4)
12.0004(9)
112.033(8)
1270.84(16)
2
9.1187(9)
23.567(3)
26.202(4)
90
5631.0(13)
8
β , °
Volume ,Å3
Z
3
1.676
1.620
1.696
1.393
Density (cald) Mg/m
-1
1.608
1.059
0.921
0.818
Absorption coefficient mm
F(000)
Reflections collected
Independent reflections
1776
7026
2992 [R(int) =
0.0325]
2354
620
3108
3108 [R(int)
= 0.0579]
2456
656
2651
2651 [R(int)
= 0.0513]
1914
2388
5792
3407 [R(int) =
0.0537]
1857
3407 / 326 / 360
1.010
Reflections with [I>2 (I)]
Data / restraints / parameters 2992 / 15 / 256 3108 / 4 / 192 2651 / 3 / 193
2
1.065
0.937
1.042
Goodness-of-fit on F
0.0441, 0.0847
0.0310,
0.0663
0.0420,
0.0682
0.0460,
0.1290
0.0678,
0.1353
0.0683, 0.1507
0.1290, 0.1832
1.043 / -0.462
Final R indices [I>2(I)], R1,
wR2
R indices (all data) R1, wR2
0.0615, 0.0917
0.416 / -0.934
Largest diff. peak and hole
0.251 / -0.356 0.910 / -0.97
-3
e.Å
Table 2. Bond lengths [Å] and angles [°] for 1-4
1

Zn(1)-O(5)
2.077(3)
Zn(1)-O(7)
2.148(3)
Zn(1)-O(6)
Zn(1)-O(8)
2.091(3)
2.100(3)
Zn(1)-N(3)
2.148(3)
2.241(3)
Zn(1)-N(1)i
O(5)-Zn(1)-O(6)
O(5)-Zn(1)-O(8)
O(6)-Zn(1)-O(8)
O(5)-Zn(1)-O(7)
O(6)-Zn(1)-O(7)
O(8)-Zn(1)-O(7)
O(5)-Zn(1)-N(3)
O(6)-Zn(1)-N(3)
87.89(12)
85.83(12)
91.80(12)
173.84(13)
90.17(11)
88.39(12)
95.42(12)
92.87(11)
O(8)-Zn(1)-N(3)
O(7)-Zn(1)-N(3)
O(5)-Zn(1)-N(1)i
O(6)-Zn(1)-N(1)i
O(8)-Zn(1)-N(1)i
O(7)-Zn(1)-N(1)i
N(3)-Zn(1)-N(1)i
175.21(12)
90.51(11)
92.61(12)
174.48(11)
82.75(12)
88.77(11)
92.56(11)
2
Zn(1)-N(1)
Zn(1)-O(1)
2.137(2)
2.185(2)
Zn(1)-N(3)
2.240(2)
83.00(11)
N(3)ii-Zn(1)-N(3)
N(1)ii-Zn(1)-N(1) 92.64(11)
N(1)ii-Zn(1)-O(1)ii 86.15(8)
N(1)-Zn(1)-O(1)ii 88.81(8)
N(1)ii-Zn(1)-N(3)ii 92.66(7)
N(1)-Zn(1)-N(3)ii
O(1)ii-Zn(1)-N(3)ii 84.43(8)
171.10(8)
N(1)-Zn(1)-O(1)
86.15(8)
O(1)-Zn(1)-N(3)ii
N(1)-Zn(1)-N(3)
101.10(8)
92.66(7)
O(1)ii-Zn(1)-O(1) 172.7(1)
3
Cd(1)-N(1)
Cd(1)-O(1)
2.328(5)
2.369(5)
Cd(1)-N(3)
2.405(5)
171.16(17)
N(1)-Cd(1)-N(3)ii
N(1)-Cd(1)-N(1)ii 92.2(2)
O(1)ii-Cd(1)-N(3)ii 82.8(2)
N(1)-Cd(1)-O(1)ii 90.62(19)
O(1)-Cd(1)-N(3)ii
N(1)-Cd(1)-N(3)
O(1)-Cd(1)-N(3)
N(3)ii-Cd(1)-N(3)
105.06(19)
92.78(17)
82.8(2)
N(1)-Cd(1)-O(1)
82.17(18)
N(1)ii-Cd(1)-O(1) 90.62(19)
O(1)ii-Cd(1)-O(1) 169.6(3)
83.2(2)
4
Cd(1)-O(5)
Cd(1)-O(4)
Cd(1)-O(3)
Cd(1)-N(2)
O(3)-Cd(1)-O(1)
O(4)-Cd(1)-O(1)
O(5)-Cd(1)-O(1)
O(3)-Cd(1)-O(2)
O(4)-Cd(1)-O(2)
O(5)-Cd(1)-O(2)
O(5)-Cd(1)-O(3)
O(5)-Cd(1)-O(4)
O(1)-Cd(1)-N(1)
2.268(10)
2.404(15)
2.402(17)
2.43(2)
177.7(6)
126.4(5)
89.0(6)
128.1(5)
85.1(4)
138.1(7)
89.1(6)
Cd(1)-O(1)
Cd(1)-N(1)
Cd(1)-O(2)
2.400(13)
2.409(18)
2.429(17)
160.1(14)
100.5(6)
104.7(7)
83.0(7)
84.9(10)
87.7(13)
117.1(13)
79.4(14)
93.3(13)
83.3(13)
N(1)-Cd(1)-N(2)
O(2)-Cd(1)-N(1)
O(3)-Cd(1)-N(1)
O(4)-Cd(1)-N(1)
O(5)-Cd(1)-N(1)
O(3)-Cd(1)-N(2)
O(4)-Cd(1)-N(2)
O(5)-Cd(1)-N(2)
O(1)-Cd(1)-N(2)
O(2)-Cd(1)-N(2)
136.7(8)
73.7(5)
Symmetry transformations: i : -x, -y, -z; ii : 1-x, y, 1/2-z
10

(a)
(b)
(c)
Fig. 3. Fragments of structure
2
. (a) fragment of coordination double chain showing the octahedral
environment of Zn(II) atom; (b) packing of the coordination tapes; view along the b axis; (c ) packing of
the coordination tapes; view along the c axis.
Table 3. Geometry of hydrogen bonds in 1-4
D-H...A, Å
d(H...A), d(D...A), Å
Å
Symmetry transformations
used to generate

(DHA), ˚
equivalent atoms
1
N(1)-H(1N)...O(3)
N(1)-H(2N)...O(2)
O(5)-H(5A)...O(3)
O(5)-H(5B)...O(1)
O(6)-H(6B)...O(1)
O(6)-H(6A)...O(4)
O(7)-H(7A)...O(4)
O(7)-H(7B)...O(2)
O(8)-H(8A)...O(1)
O(8)-H(8B)...O(4)
2.04(2)
2.12(2)
1.83(2)
1.96(2)
1.93(2)
1.86(2)
2.19(2)
1.92(2)
1.88(2)
1.89(2)
2.889(4)
2.982(4)
2.684(4)
2.806(4)
2.760(4)
2.699(4)
2.940(4)
2.772(4)
2.723(4)
2.718(4)
2
173(4)
172(4)
172(5)
164(4)
163(3)
173(4)
149(4)
166(4)
167(5)
164(4)
1-x, -y, -z
x-1/2, -y-1/2,-z
1/2-x, y-1/2, z
x-1, y, z
x-1/2, y, 1/2-z
x, y, z
x, y, z
1/2-x, y+1/2, z
1/2-x, y+1/2, z
x-1/2, y, 1/2-z
N(3)-H(3A)...O(3)
N(3)-H(3B)...O(2)
O(4)-H(4A)...N(2)
2.13(2)
2.29(2)
2.29(3)
2.928(3)
3.138(3)
3.195(4)
3
156(3)
167(3)
160(4)
x, 1-y, z-1/2
1-x, 1-y, 1-z
x+1, y+1, z
11

N(3)-H(3A)...O(3)
N(3)-H(3B)...O(2)
O(4)-H(4A)...N(2)
2.09(3)
2.41(3)
2.3(1)
2.925(7)
3.243(8)
3.179(9)
4
157(6)
161(6)
157(9)
x, 1-y, z-1/2
1-x, 1-y, 1-z
x+1,y+1,z
O(5)-H(5A)...O(1)
O(5)-H(5B)...O(3)
2.21
2.13
2.69(2)
2.64(2)
110.9
113.5
x-1/2, 3/2-y, z
x+1/2, 3/2-y,z
(a)
(b)
(c)
(d)
Fig. 4. Fragments of structure 4. (a) View for the Cd(II) coordination environment with thermal ellipsoids
of 50% probabilities; (b) view of the coordination layer along the crystallographic b axis; (c) schematic
representation of two interwoven coordination layers, top and side views; (d) packing of the layers with
the voids shown by yellow color
Compound [Cd(bda4Py)2(dpa)2]·2H2O (4) crystallizes in the noncentrosymmetric orthorhombic space group
Iba2 (Table 1). The Cd(II) atom is 7-coordinated (distorted pentagonal bipyramid), and the coordination
surrounding comprises an N2O5 set of donor atoms going from two chelate carboxylate groups of dpa ligand
and one water molecule in the equatorial plane, and two bda4Py ligands in two apical positions (Fig. 4a).
12

Cd-O distances are in the range 2.268(9)-2.431(17) Å, Cd-N distances adjust the values 2.43(2) and
2.448(18) Å (Table 3). Both ligands are in the twisted conformations with the dihedral angles between the
cyclic fragments of 14.58
 in bda4Py and 46.23  in dpa. Each ligand acts as a bridge. Similar to 1-3, in 4
bda4Py ligand coordinates in a bidentate-bridging mode, via N-binding sites of pyridine cycle and amino-
group, thus providing the joining of successive metal atoms along the crystallographic c axis, Cd···Cd
separation across bda4Py ligand being 14.363 Å; the dicarboxylate anion dpa also works as a mediator
between the successive Cd(II) atoms along the crystallographic a axis, providing Cd···Cd separation of 9.119
Å; these mediators provide the linking of the components in the layer of 4,4 topology parallel to the ac
crystallographic plane (Fig. 4b). Herein, the incorporation of the bulky dicarboxylic ligand dpa reduces the
number of bda4Py ligands coordinated to the same metal from 4 in 2-3 to 2 in 4. The layers stack along the
crystallographic b axis with each two layers, that are related by the glide plane a, and interconnected via
OH(H2O)···O(COO) hydrogen bonds, being interwoven with formation of double sheet (Fig. 4c). These
double-layered aggregates meet by their hydrophobic surfaces that form the phenyl rings of dpa. The
interlayer space in the crystal occupy the disordered water molecules, since the loosely packed double sheets
provide the channels running along the crystallographic c axis in the crystal that constitute 10.4% or 586 Å3
of the unit cell volume (Fig. 4d).
The attempts for the counter synthesis of 1-4 starting directly from bda4Py were succeeded only for
compound
1 for now. For the other reaction mixtures, the oxidation of the ligand was observed indicated by
the cloudy, dark in color solutions. The impossibility to directly reproduce compounds with the similar
ligand, N-(2-pyridylmethylene)benzene-1,4-diamine, is reported [21, 42, 43].
To explore the stability of the ligand bda4Py and compound
(Fig. 5, Fig.S7).
1, the thermogravimetric analysis was performed
Fig. 5. Thermal behavior of
1

Ligand bda4Py melts at 208 °C, then decomposes oxidatively in two steps. The complex
53 oC, then decomposes in 6 steps (Fig. 5). The first stage between 53-142 oC is endothermic, where
(calcd = 16.7%) of the mass assigned to the coordinating water is lost. The following oxidative
decomposition steps are carried out between 330-530 oC involving ligand decomposition and
43% loss of
1
is stable up to
∼
16%
∼
mass (calcd = 45.7%). The remaining 41% of the mass can be attributed to zinc sulfate (calcd =
37.5%) that decomposes in the range of 538-635 °C with the formation of SO3, and the residue
ZnO, 15.66% (calcd = 18.9%) (Fig. S8, Fig. S9).
Optical properties
IR characterization of the ligand bda4Py and coordination compounds 1-4
The IR spectroscopic investigation of 1-4 also confirmed the presence of the ligand with terminal amino-
group. The comparative IR specroscopic investigation has been undertaken for ligands and compounds 1-4
(Fig. S5). In the ligand bda4Py itself, the availability of amino (-NH2) group is confirmed by the νas(NH)
3434 cm-1 and νs(NH) 3315 cm-1 characteristic bands. The band at 3179 cm-1 represents a shoulder originated
from the overtone of the N–H bending band. These bands are also present in compounds 1-4 shifted to the
lower values. These shifts to smaller wavelengths are explained by coordination of amino group to the metal
with the formation of NH···O hydrogen bond [44]. Ligand bda4Py has two δ(CH) bands at 832 and 793 cm-
1 which can be attributed to p-disubstituted aromatic structure. In compounds 1-4 these δ(CH) bands are also
present in the range 841-780 cm-1. For compound
that can be attributed to the o-disubstituted diphenic acid.
In compound
, the SO42- anion that is not bonded to the metal, reveals a very strong ν3(SO) band at 1035
4
there are also two strong bands, δ(CH) 770, 748 cm-1
1
cm-1. Due to the formation of hydrogen bonds between the sulfate ion and the water molecules, the symmetry
of the sulfate ion decreases [44-46], so in the spectrum some specific bands of lower intensity appear for this
group. For this compound, there is a broad and intense ν(OH) characteristic band in the 3500-3100 cm-1
region that indicates the formation of OH···O hydrogen bonds. An additional band of medium intensity for
-
coordinated water molecules δ(H2O) is present at 1667 cm-1 [45, 46]. In
2
and
3
the NO3 anion is monodentate
coordinated to the metal (C2υ symmetry). To this group is assigned a strong ν3(A’1) band at 987 cm-1 for
and 1038 cm-1 for . The ν3(E’) band is split in the two bands νas(NO) 1413 cm-1 for , 1420 cm-1 for 2, and
, the bands characteristic for the carboxylate
3
2
3
νs(NO) 1316 cm-1 respectively 1312 cm-1 [46]. For compound
anion νas(CO) 1530 cm-1 and νs(CO) 1405 cm-1 are present.
4
Absorption and emission properties
To monitor the limits of stability of the ligands bda4bPy and bda4Py in the acidic medium, the absorption
curves for EtOH solutions of both ligands in the UV-Vis range of spectrum were recorded. All experiments
were carried out at room temperature (292 K). The solutions were prepared in EtOH solvent with a ligand
concentration of 3.3 x 10-5 M. Ligand bda4bPy has four absorption peaks, λmax, centered at 202, 234, 279
and 365 nm, while bda4Py revealed three absorption peaks centered at 203, 242 and 386 nm. Ligands
14

bda4bPy and bda4Py have characteristic absorption band C=N that corresponds to transitions n→π*. For
bda4bPy λmax = 365 nm, A = 0.64 and bda4Py at λmax = 386 nm, A = 0.48. (Fig. 7).
Fig. 7. UV-Vis absorption spectra of bda4bPy and bda4Py in the EtOH solution upon gradual increase of
acidity.
To the bda4bPy chromophore solution, 0.1 M HCl solution was added, gradually increasing the molar ratio
of acid to chromophore. The UV-Vis spectra for all solutions were measured 5 minutes after acid addition.
Starting from the ligand to acid molar ratio of 1: 0.25, the color of solution changed from yellow to orange,
and the recorded curve becomes identical with the curve for bda4Py chromophore but lower intensity, A =
0.38. This demonstrates that hydrolysis of bda4bPy has taken place with bda4Py ligand formation. According
to these measurements it was found that compound bda4bPy has a hydrolytic propensity in the acidic
medium, so that at the molar ratio of 1 : 3 the virtually total amount of compound bda4bPy is hydrolysed.
The stability of chromophores bda4bPy and bda4Py was also elucidated in the presence of Cd(II) cation. To
study this, the cadmium nitrate Cd(NO3)2·4H2O salt was used in admixture with the bda4bPy ligand in
various molar ratios. All measurements were recorded in DMF solvent. To record the absorption curves the
solutions were used with the concentration of ligand of 3.3 x 10-5 M, varying only the molar ratio of cadmium
nitrate. First, the curves for the bda4bPy ligands λmax = 366, A = 0.60 and bda4Py λmax = 392, A = 0.54 were
recorded. Then the curve for the solution of the mixture of cadmium nitrate and bda4bPy in the molar ratio
of 1: 1, λmax = 368, A = 0.55. It can be seen that these values do not differ much from bda4bPy. When this
solution was heated to the boiling temperature of DMF for 10 min, the color of solution was changed to
intense orange, and after the cooling the spectrum was recorded λmax = 390, A = 0.53 (Fig. 8). The obtained
values are characteristic for the bda4Py ligand which proves that the hydrolysis of the bda4bPy ligand has
taken place. The following solutions were measured with the gradual increase of the ion concentration of
Cd(II). Thus, it has been found that increasing the concentration of the metal ions (e.g., the last measured
curve, the molar ratio of salt to ligand, 15:1) does not cause hydrolysis of the second azomethine group,
C=N. The solution color remains constant, orange.

Fig. 8. UV-Vis absorption spectra of bda4bPy and bda4Py gradual increase of concentration of Cd(NO3)2
l, nm
700
600
500
400
5
4
3
2
1
0
bda4Py
(1)
(4)
2,0
2,4
hn, eV
2,8
3,2
Fig. 9. Solid state emission spectra of free bda4Py ligand,
1 and 4 at room temperature.
The luminescent properties of free bda4Py chromophore and coordination compounds
1 and 4 were
investigated in the solid state at room temperature. As shown in Fig. 9, upon excitation at λexc = 337.1 nm,
the free Schiff-base bda4Py displays an emission band at 545 nm, which can probably be attributed to the
intraligand π*···π transitions [47]. For the complex
bathochromic shift of an intense and broad emission maximum centered in the interval 620-650 nm; no
pronounced signal was registered for , the emission quenching is most probably explained by the significant
1, the solid-state luminescent spectrum shows the
4
structure disorder and availability of big voids in this solid.
Conclusions
In summary, four coordination compounds [Zn(H2O)4(bda4Py)]2(SO4)2 (
1
), {[Zn(NO3)2(bda4Py)2].2H2O}n
), {[Cd(NO3)2(bda4Py)2].2H2O}n ( ), and {[Cd(bda4Py)2(dpa)2].2H2O}n (
(2 3 4) with the generated in situ
Schiff-base ligand bda4Py=N-((pyridin-4-yl)methylene)benzene-1,4-diamine have been isolated and
structurally characterized. Everywhere this chromophore acts as a bidentate linker between two metal centers
16

through nitrogen atoms of pyridino- and amino-groups. The additional stabilization of the crystalline solids
can be achieved via hydrogen bonds with participation of the ligand’s amino-group. The tuning structures
and emissive properties is possible by the metal and second ligand variations.
Acknowledgements
Authors thank the project CSSDT 15.817.02.06F for support.
References
[1] D. Sek, M. Siwy, K. Bijak, M. Grucela-Zajac, G. Malecki, K. Smolarek, E. Schab-Balcerzak, J. Phys.
Chem. A. 117 (2013) 10320–10332.
https://pubs.acs.org/doi/abs/10.1021/jp407623u
[2] D. Sek, M. Siwy, K. Bijak, M. Filapek, G. Malecki, E. M. Nowak, J. Sanetra, A. Jarczyk-Jedryka, K.
Laba, M. Lapkowski, E. Schab-Balcerzak, J. Electroanal. Chem. 751 (2015) 128-136.
https://doi.org/10.1016/j.jelechem.2015.05.040
[3] B.-B. Ma, H. Zhang, Y. Wang, Y.-X. Peng, W. Huang, M.-K. Wang, Y. Shen, J. Mater. Chem. C 3 (2015)
7748-7755. https://doi.org/10.1039/C5TC00909J
[4] C. Niu, L. Zhao, T. Fang, X. Deng, H. Ma, J. Zhang, N. Na, J. Han, J. Ouyang, Langmuir. 30(9) (2014)
2351–2359. https://pubs.acs.org/doi/abs/10.1021/la404436v
[5] A. D. Garnovskii, I. S. Vasil'chenko, Russ. Chem. Rev. 71(11) (2002) 943-968.
https://doi.org/10.1070/RC2002v071n11ABEH000759
[6] Z. Shaghaghi, Spectrochim. Acta A Mol. Biomol. Spectrosc. 131 (2014) 67-71.
https://doi.org/10.1016/j.saa.2014.04.026
[7] A. Gusev, V. Shul’gin, E. Zamnius, G. Starova, K. Lyssenko, I. Eremenko, W. Linert, J. Luminescence.
202 (2018) 370-376. https://doi.org/10.1016/j.jlumin.2018.05.077
[8] M. Sarigul, A. Sari, M. Kose, V. McKee, M. Elmastas, I. Demirtas, M. Kurtoglu, Inorg. Chim. Acta. 444
(2016) 166-175. https://doi.org/10.1016/j.ica.2016.01.042
[9] E. Cariati, A. Forni, E. Lucenti, D. Marinotto, A. Previtali, S. Righetto, C. Botta, V. Bold, V. Kravtsov,
M. S. Fonari, Chem. Asian J. 14 (2019) 853-858.
https://doi.org/10.1002/asia.201801604
[10] D. Chisca, L. Croitor, O. Petuhov, O.V. Kulikova, G. F. Volodina, E. B. Coropceanu, A.E. Masunov,
M. S. Fonari, CrystEngComm. 20 (2018) 432-447.
https://doi.org/10.1039/C7CE01988B
[11] G. Zhang, G. Yang, and J. S. Ma, Cryst. Growth Des. 6 (2006) 1897-1902.
https://pubs.acs.org/doi/abs/10.1021/cg060173l
[12] A. J. Calahorro, E. San Sebastian, A. SalinasCastillo, J. M. Seco, C. Mendicute-Fierro, B. Fernández,
A. Rodríguez-Diéguez, CrystEngComm. 17 (2015) 3659-3666.
https://doi.org/10.1039/C5CE00010F

[13] B. Manna, S.Singh, S.K. Ghosh, J. Chem. Sci. 126(5) (2014) 1417-1422.
https://doi.org/10.1007/s12039-014-0704-y
[14] V. Lozovan, E. B. Coropceanu, P. N. Bourosh, A. Micu, M. S. Fonari, Russ. J. Coord. Chem. 45(1)
(2019) 11–21.
https://doi.org/10.1134/S0132344X19010079
[15] G. Mahmoudi, A. V. Gurbanov, S. Rodriguez-Hermida, R. Carballo, M. Amini, A. Bacchi, M. P.
Mitoraj, F. Sagan, M. Kukułka, D. A. Safin, Inorg. Chem. 56 (2017) 9698-9709.
https://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.7b01189
[16] A. R. Kennedy, F. R. N. Waterson, Acta Crystallogr. C 59 (2003) o613-o615.
https://doi.org/10.1107/S010827010302050X
[17] N. Rad-Yousefnia, B. Shaabani, M. Kubicki, M. S. Zakerhamidi, A. M. Grzeskiewicz, Polyhedron 129
(2017) 38-45. https://doi.org/10.1016/j.poly.2017.03.022
[18] Y. Diskin-Posner, G.K. Patra, I. Goldberg, Dalton Trans. (2001) 2775-2782.
https://doi.org/10.1039/B104961P
[19] M. Y. Masoomi, S. Beheshti, A. Morsali, J. Mat. Chem. A 2 (2014) 16863-16866.
https://doi.org/10.1039/C4TA04001E
[20] M. Zahedi, B. Shaabani, M. Aygun, C. Kazak Inorg. Chim. Acta. 469 (2018) 461-468.
https://doi.org/10.1016/j.ica.2017.09.023
[21] N. M. Shavaleev, Z. R. Bell, G. Accorsi, M. D. Ward, Inorg. Chim. Acta. 351 (2003) 159-166.
https://doi.org/10.1016/S0020-1693(03)00202-0
[22] G. L. Eichhorn, J. C. Bailar Jr., J. Am. Chem. Soc. 75(12) (1953) 2905-2907.
https://pubs.acs.org/doi/abs/10.1021/ja01108a034?journalCode=jacsat
[23] M. Das, S. E. Livingstone, Inorg. Chim.Acta. 19 (1976) 5-10.
https://doi.org/10.1016/S0020-1693(00)91065-X
[24] D. V. Prabhu, N. B. Laxmeshwar, Asian J. Chem. 9(1) (1997) 70-74.
[25] R. K. Y. Ho, S. E. Livingstone, Austral. J. Chem. 18 (1965) 659-671.
https://doi.org/10.1071/CH9650659
[26] L. F. Lindoy, Q. Rev. Chem. Soc. 25 (1971) 379-391.
https://doi.org/10.1039/QR9712500379
[27] A. C. Dash, R. K. Nanda, J. Am. Chem. Soc. 91(25) (1969) 6944–6947.
https://pubs.acs.org/doi/abs/10.1021/ja01053a010?journalCode=jacsat
[28] K. Koehler, W. Sandstrom, E. H. Cordes., J. Am. Chem. Soc. 86(12) (1964) 2413-2419.
https://pubs.acs.org/doi/abs/10.1021/ja01066a024?journalCode=jacsat
[29] S. D. Barton, W. D. Ollis, I. O. Sutherland, Comprehensive organic chemistry, Vol. 2, Oxford, New
York: Pergamon Press, 1979.
[30] M. B. Smith, J. March, March’s Advanced Organic Chemistry, 6th Edition, New Jersey 2007.
18

[31] B. Bhattacharya R. Haldar, R. Dey, T. K. Maji, D. Ghoshal, Dalton Trans. 43 (2014) 2272–2282.
https://doi.org/10.1039/C3DT52266K
[32] D. Singh, C. M. Nagaraja, Cryst. Growth Des. 15(7) (2015) 3356-3365.
https://pubs.acs.org/doi/abs/10.1021/acs.cgd.5b00450
[33] B. Bhattacharya, R. Haldar, D. K Maity, T. K. Maji, D. Ghoshal, CrystEngComm. 17 (2015) 3478-
3486. https://doi.org/10.1039/C5CE00143A
[34] E. H. Cordes, W. P. Jencks, J. Am. Chem. Soc. 84 (5) (1962) 832–837.
https://pubs.acs.org/doi/abs/10.1021/ja00864a031?journalCode=jacsat
[35] G. A. Farnum, J. S. Lucas, C. Y. Wang, R. L. LaDuca, Inorg. Chim. Acta 368 (2011) 84–95.
doi:10.1016/j.ica.2010.12.053
[36] G. M. Sheldrick, Acta Crystalogr. A64 (2008) 112-122
https://doi.org/10.1107/S0108767307043930
.
[37] G. M. Sheldrick, Acta Crystallogr. C71 (2015) 3-8.
https://doi.org/10.1107/S2053229614024218
[38] C. F. Macrae, I. J. Bruno, J. A. Chisholm, P. R. Edgington, P. McCabe, E. Pidcock, L. Rodriguez-
Monge, R. Taylor, J. van de Streek, P. A. Wood, J. Appl. Crystallogr. 41 (2008) 466-470.
https://doi.org/10.1107/S0021889807067908
[39] A. L. Spek, Acta Crystallogr. D65 (2009) 148-155.
https://doi.org/10.1107/S090744490804362X
[40] D. Grasso, G. Buemi, S. Fasone, C. Gandolfo, Croatica Chemica Acta. 54(1) (1981) 85-90.
[41] M. Badertscher, P. Bühlmann, E. Pretsch, Structure Determination of Organic Compounds, fourth ed.,
Springer, 2009, DOI 10.1007/978-3-540-93810-1 (a) pp. 189, 178; (b) pp.104, 95, 118, 120.
[42] N. Chanda, B. Mondal, V. G. Puranik, G. K. Lahiri Polyhedron. 21 (2002) 2033-2043.
https://doi.org/10.1016/S0277-5387(02)01131-2
[43] K. Marjani, J. Asgarian, M. Mousavi, V. Amani, Z. Anorg. Allg. Chem. 635 (2008) 1633-1637.
https://doi.org/10.1002/zaac.200801312
[44] L. Bellamy, Infrared Spectra of Complex Molecules, Springer, 1975.
[45] H. H. Adler, P. F. Kerr, Am. Mineral. 50 (1965) 132-147.
https://pubs.geoscienceworld.org/msa/ammin/article-abstract/50/1-2/132/540022
[46] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, fourth ed.,
Hoboken, 1986.
[47] Y.-W. Dong, R.-Q. Fan, X.-M. Wang, P. Wang, H.-J. Zhang, L.-G. Wei, W. Chen, Y.-L. Yang, Cryst. Growth
Des. 16 (2016) 3366−3378. https://pubs.acs.org/doi/abs/10.1021/acs.cgd.6b00347

GRAPHICAL ABSTRACT
Synopsis:
The chromophore, N-((pyridin-4-yl)methylene)benzene-1,4-diamine, obtained as the product of partial hydrolysis
of the known ligand, N1,N4-bis(pyridin-4-ylmethylene)-benzene-1,4-diamine demonstrates promising potential for
crystal engineering of emissive coordination polymers.
20

Highlights
 Chromophore N-((pyridin-4-yl)methylene)benzene-1,4-diamine obtained in situ

Hydrolytic transformation of N1,N4-bis(pyridin-4-ylmethylene)-benzene-1,4-diamine


Spectroscopic study of organic chromophores and coordination compounds
Crystal structures of Zn and Cd new coordination compounds.