Coumarin-naphthohydrazone ligand with a rare coordination mode to form Mn(II) and Co(II) 1-D coordination polymers: synthesis, characterization, and crystal structure

Article abstract of DOI:10.1080/00958972.2018.1446083

The hydrazone (E)-3-hydroxy-N’-(1-(2-oxo-2H-chromen-3-yl)ethylidene)-2-naphthohydrazide (H₂L) was synthesized from the reaction of 3-acetylcoumarin and 3-hydroxy-2-naphthoic hydrazide in methanol. Compounds [Mn(H₂L)(NO₃)₂(CH₃OH)]?CH₃OH (1a), [Mn(HL)(NO₃)(CH₃OH)]_n (1b), [Co(HL)(NO₃)(CH₃OH)]_n (2), and [Cu(HL)(NO₃)] (3) were obtained by reaction of an equimolar amount of H₂L with nitrate salts of Mn(II), Co(II), or Cu(II) in methanol. The reaction of ligand and Mn(NO₃)₂·4H₂O was also carried out in the presence of sodium azide which led to the 1-D coordination polymer, [Mn(HL)(N₃)(CH₃OH)]_n (4). All of the synthesized compounds were characterized by elemental analyses and spectroscopic methods. Single-crystal X-ray analysis of 1–4 indicated that H₂L is neutral (in 1a) or mononegative ligand (in 1b, 2, 3 and 4). In 1b, 2 and 4 the 1-D polymeric chain is found by a rare coordination mode of this kind of hydrazone ligand since the naphtholic oxygen is coordinated to the neighboring metal ions while the NH moiety of hydrazone remains intact, also confirmed by FT-IR spectroscopic studies. The thermal stability of 2 and 4 were also studied from 30–1000?°C.

Full text of DOI:10.1080/00958972.2018.1446083

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Coumarin-naphthohydrazone ligand with a
rare coordination mode to form Mn(II) and
Co(II) 1-D coordination polymers: synthesis,
characterization, and crystal structure
Rahman Bikas, Hossein Farzaneh-Bonab, Nader Noshiranzadeh, Muhittin
Aygün, Marzieh Emami & Tadeusz Lis
To cite this article: Rahman Bikas, Hossein Farzaneh-Bonab, Nader Noshiranzadeh, Muhittin
Aygün, Marzieh Emami & Tadeusz Lis (2018): Coumarin-naphthohydrazone ligand with a rare
coordination mode to form Mn(II) and Co(II) 1-D coordination polymers: synthesis, characterization,
and crystal structure, Journal of Coordination Chemistry, DOI: 10.1080/00958972.2018.1446083
To link to this article: https://doi.org/10.1080/00958972.2018.1446083
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Journal of Coordination Chemistry, 2018
https://doi.org/10.1080/00958972.2018.1446083
Coumarin-naphthohydrazone ligand with a rare coordination
mode to form Mn(II) and Co(II) 1-D coordination polymers:
synthesis, characterization, and crystal structure
Rahman Bikasa, Hossein Farzaneh-Bonabb, Nader Noshiranzadehb, Muhittin Aygünc,
Marzieh Emamib and Tadeusz Lisd
afaculty of science, department of Chemistry, imam Khomeini international university, Qazvin, iran; bfaculty
c
of sciences, department of Chemistry, university of Zanjan, Zanjan, iran; faculty of science, department of
Physics, dokuz eylül university, İzmir, turkey; dfaculty of Chemistry, university of Wroclaw, Wroclaw, Poland
ABSTRACT
ARTICLE HISTORY
received 7 July 2017
accepted 18 January 2018
The
hydrazone
(E)-3-hydroxy-N’-(1-(2-oxo-2H-chromen-3-yl)
ethylidene)-2-naphthohydrazide (H2L) was synthesized from the
reaction of 3-acetylcoumarin and 3-hydroxy-2-naphthoic hydrazide in
methanol. Compounds [Mn(H2L)(NO3)2(CH3OH)]·CH3OH (1a), [Mn(HL)
(NO3)(CH3OH)]n (1b), [Co(HL)(NO3)(CH3OH)]n (2), and [Cu(HL)(NO3)] (3)
were obtained by reaction of an equimolar amount of H2L with nitrate
salts of Mn(II), Co(II), or Cu(II) in methanol. The reaction of ligand and
Mn(NO3)2·4H2O was also carried out in the presence of sodium azide
which led to the 1-D coordination polymer, [Mn(HL)(N3)(CH3OH)]n (4).
All of the synthesized compounds were characterized by elemental
analyses and spectroscopic methods. Single-crystal X-ray analysis
of 1–4 indicated that H2L is neutral (in 1a) or mononegative ligand
(in 1b, 2, 3 and 4). In 1b, 2 and 4 the 1-D polymeric chain is found
by a rare coordination mode of this kind of hydrazone ligand since
the naphtholic oxygen is coordinated to the neighboring metal ions
while the NH moiety of hydrazone remains intact, also confirmed by
FT-IR spectroscopic studies. The thermal stability of 2 and 4 were also
studied from 30–1000 °C.
KEYWORDS
hydrazone; coumarin schiff
base; crystal structure;
spectroscopic studies; tGa
CONTACT nader noshiranzadeh
nadernoshiranzadeh@znu.ac.ir
the supplemental data for this article can be accessed at https://doi.org/10.1080/00958972.2018.1446083.
© 2018 informa uK limited, trading as taylor & francis Group

2
R. BIKAS ET AL.
1. Introduction
Coordination polymers are still an attractive research field due to versatile structural diver-
sities and topologies, as well as interesting potential applications in fields such as optical,
electronic, magnetic, ion exchange, medicine, gas storage, luminescence, and catalysis [1].
Organic ligands with specific structural properties influence the diversity of structures and
structural dependent properties of coordination polymers [2]. Thus, several studies are done
to introduce new organic ligands and synthetic methods for obtaining coordination
polymers.
Hydrazone compounds play important roles in fields from organic synthesis, analytical
chemistry, and inorganic chemistry to medicinal chemistry [3]. In coordination chemistry,
hydrazone compounds are widely used flexible and versatile polydentate ligands [2, 4]. Due
to the facile keto-enol tautomerization in the −NH−C(=O)− moiety, hydrazones are able to
modulate the number of negative charges in coordination systems and form stable com-
plexes with metal ions in various oxidation states [1, 3, 5]. Due to high stability, hydrazone
complexes are good candidates for various catalytic reactions [6]. Hydrazones obtained by
condensation of salicyloyl hydrazide with ortho-hydroxy aldehydes/ketones are a class of
ligands that can bind to metal ions through two coordination sites including a ONO-donor
pocket and a NO-moiety (see Scheme 1(a)) [7]. The presence of an OH group in suitable
position with respect to the hydrazone moiety provides additional coordinating sites and
increases the denticity of the resulting ligand. In such conditions the amidic nitrogen can
also coordinate to metal ions and this increases the ability of these ligands to generate
polynuclear complexes and coordination polymers [8]. However, in some cases the NO-moiety
does not coordinate to metal ions. In this case, the ligands usually coordinate to metal ions
in enol form and the OH involves in intramolecular hydrogen bonding (see Scheme 1(b)) [9].
3-Hydroxy-2-naphthoic hydrazide derivatives can also act similar to salicyloyl hydrazones
due to their structural similarities (Scheme 1(c)). However, there are limited reports on
3-hydroxy-2-naphthoic hydrazide derivatives which can be attributed to its larger size and
lower solubility in most popular solvents making difficult preparation of suitable single
crystals from its derivatives. Deprotonation of amidic NH [9] or both amidic NH and phenolic
OH groups [8] of such ligands have been reported. However, coordination of phenolic group
without deprotonation of amidic NH group is quite rare. Although recently a limited number
of complexes with lanthanides (Y, Dy, Tb, Ho, or Er) [10], Zn [11], Cd [12] and alkaline metal
ions [13] were reported, this coordination mode is considered as unprecedented coordina-
tion mode [14].
Coumarin (Scheme 2(a)) is a fragrant organic compound in the benzopyrone chemical
class found in many plants [15]. Coumarin derivatives can be easily prepared by reactions
like the Perkin reaction [16] or the Pechmann condensation [17]. Coumarin compounds
display important biological activities such as antimicrobial, antifungal, anticoagulant, anti-
HIV, anticancer, and antioxidant properties and have been widely used in perfumes and
fabric conditioners [18]. They are also used in some dye lasers and as a sensitizer in photo-
voltaic technologies [19]. More specifically, 3-acetylcoumarins (Scheme 2(b)) can be useful
in coordination chemistry since it has acetyl functionality which can be involved in Schiff
base condensation with primary amines to form interesting ligands. In general, it can coor-
dinate similar to ligands derived from ortho-hydroxy aldehydes/ketones (Scheme 2(c)).
However, the oxygen in this case coordinates to metal ions as a neutral O-donor (Scheme 2(d)).

JOURNAL OF COORDINATION CHEMISTRY
3
Therefore, such ligands will have moderate negative character and may be safer than salic-
ylalidine derivatives by considering their occurrence in several biological systems and appli-
cations in various environments.
Although combination of 3-acetylcoumarin derivatives with aromatic/aliphatic hydrazides
could form interesting hydrazone ligands with specific coordination abilities, searching the
literature including Cambridge Structural Database (CSD) [20] indicates that there are only
two reports on Cu(II) [21] and Zn(II) [22] coordination compounds with coumarin-hydrazone
ligands. Thus, in order to increase knowledge about the coordination chemistry of such
ligands, our present investigation focuses on the synthesis and coordination behavior of a
hydrazone ligand obtained from condensation of 3-acetylcoumarin and 3-hydroxy-2-naph-
thoic hydrazide as an anchoring group that can also provide a well-defined binding envi-
ronment and coordination behavior. As a result of this study, here we report synthesis,
characterization, and crystal structure of three coordination polymers and two mononuclear
complexes obtained with this ligand.
2. Experimental
2.1. Materials and instrumentation
Manganese(II) nitrate tetrahydrate, cobalt(II) nitrate hexahydrate, copper(II) nitrate trihydrate,
3-hydroxy-2-naphthoic hydrazide, ethyl acetoacetate, salicylaldehyde, and other starting
1
materials were purchased from Merck and used as received. H and 13C NMR spectra of
organic compounds in DMSO-d6 solution were measured on Bruker 250 and 62.9 MHz spec-
trometers, respectively, and chemical shifts are indicated in ppm relative to tetramethylsilane.
FT–IR spectra were recorded as KBr disks with a Bruker FT–IR spectrophotometer. UV–Vis
spectra of solutions were recorded on a thermo spectronic, Helios Alpha spectrophotometer.
The electronic reflectance spectra of undiluted compounds were measured on a Cary 5
UV–vis–NIR spectrophotometer from 200–800 nm. Thermal gravimetric analysis (TGA) curves
were recorded with a SETSYS EvolutionTGA instrument from 25–1000 °C. The atomic absorp-
tion analysis was carried out using a Varian Spectra AA-220 equipment.
2.2. Synthesis of 3-acetylcoumarin
Ethyl acetoacetate (1.2 mL, 10 mmol) was added to a solution of salicylaldehyde (1.0 mL,
10 mmol) and the mixture was stirred for 5 min. Then, piperidine (1 mL, 10 mmol) was slowly
added to the reaction flask and the mixture was stirred for 3 h at room temperature giving
a large quantity of pale white solid (see Scheme 3). The solvent was decanted and the remain
-
ing solid residue was washed with cold ethanol and dried in air. Pale white solid was finally
obtained in a yield of 96% (1.79 g). M.p. 122–125 °C. Anal. Calcd for C11H8O3 (MW = 188.18):
C, 70.21; H, 4.29%. Found: C, 70.28; H, 4.26%. FT-IR (KBr, cm−1): 3428 (br,m), 3085 (w), 3094
(w), 2977 (w), 2853 (w), 1725 (vs), 1677 (s, 1654 (m), 1600 (s), 1560 (m), 1480 (w), 1450 (w),
1413 (w), 1366 (w), 1355 (w), 1297 (w), 1260 (w), 1226 (m), 1202 (s), 1162 (m), 1122 (w), 970 (w),
949 (w), 873 (w), 778 (m), 766 (m), 734 (w), 670 (w), 634 (m), 581 (m), 612 (w), 545 (w), 481
1
(w), 456 (m). H NMR (250 MHz, CDCl3, 25 °C, TMS): δ 8.48 (s, 1H), 7.26–7.63 (m, 4H, Ar–H),
2.69 (s, 3H) ppm. 13C NMR (62.90 MHz, CDCl3): δ = 195.5, 159.2, 155.2, 147.5, 134.4, 130.

4
R. BIKAS ET AL.
(a)
(c)
(b)
(d)
Scheme 1. (a) ono- and no-donor coordination modes of salicyloyl hydrazones; (b) intramolecular
o−h⋯n hydrogen bond when salicyloyl hydrazones are ono-donor ligands; (c) general formula of
3-hydroxy-2-naphthoic hydrazones; (d) the rare coordination mode of salicyloyl hydrazones.
(a)
(b)
(c)
(d)
Scheme 2. General molecular structure of (a) coumarin, (b) 3-acetylcoumarins and (c) ortho-
hydroxy aldehydes/ketones; (d) comparing the coordination behavior of schiff bases obtained from
3-acetylcoumarins and ortho-hydroxy aldehydes/ketones.
(a)
(b)
Scheme 3. synthesis pathway of (a) 3-acetyl-2H-chromen-2-one; (b) h2l.

JOURNAL OF COORDINATION CHEMISTRY
5
2.3. Synthesis of (E)-3-hydroxy-N’-(1-(2-oxo-2H-chromen-3-yl)ethylidene)-2-
naphthohydrazide (H2L)
A methanol solution (10 mL) of 3-hydroxy-2-naphthoic hydrazide (0.404 g, 2 mmol) was
added to a methanol solution of 3-acetylcoumarin (0.376 g, 2 mmol). The mixture was
refluxed for 4 h at 60 °C. The resulting light yellow product was filtered after cooling and
washed with cooled methanol and dried under vacuum. Yield 85% (0.316 g). M.p. 262–267 °C.
Anal. Calcd for C22H16N2O4 (MW = 372.38): C, 70.96; H, 4.33; N, 7.52 %. Found: C, 71.05; H, 4.39;
N, 7.49 %. FT-IR (KBr, cm−1): 3412 (br, m), 3269 (m), 3049 (m), 2933 (w), 2855 (w), 1721 (s), 1708
(vs), 1658 (m), 1632 (m), 1624 (s), 1604 (s), 1572 (w), 1548 (m), 1516 (w), 1449 (w), 1430 (w),
1339 (w), 1365 (m), 1347 (w), 1322 (w), 1271 (w), 1239 (m), 1219 (s), 1178 (w), 1157 (w), 1132
(m), 1067 (w), 1029 (w), 1010 (w), 972 (m), 956 (w), 915 (w), 882 (m), 846 (w), 792 (w), 762 (m),
749 (s), 670 (w), 620 (w), 531 (w), 476 (w), 451 (w). 1H NMR (250 MHz, DMSO-d6, 25 °C, TMS):
δ 11.75 (s, OH), 11.59 (s, NH(Amide)), 8.62–7.15 (11CH, Aromatic), 2.29 (3H, CH3) ppm. 13C NMR
(62.90 MHz, DMSO-d6): δ = 162.05 (C=O(Amide)), 159.75 (C-OH), 153.92 (C=O(ester)), 153.01 (C=N),
150.95, 144.15, 142.19, 136.27, 133.36, 132.94, 132.45, 129.75, 128.82, 127.65, 126.96, 126.17,
125.28, 124.38, 121.05, 119.24, 116.85, 116.48, 111.12, 16.20 (CH3). UV–vis (in CH3OH,
c = 2.5 × 10−5 M, λmax [nm] with ε [M−1 cm−1]): 235 (40,880), 297 (15,440), 339 (63,500).
2.4. Synthesis of [Mn(H2L)(NO3)2(CH3OH)]·CH3OH·(1a)
H2L (0.372 g, 1 mmol) and Mn(NO3)2⋅4H2O (0.251 g, 1 mmol) were placed in the main arm of
a branched tube. Methanol was carefully added to fill the arms, the tube was sealed and the
reagents containing arm immersed in an oil bath at 60 °C while the other arm was kept at
ambient temperature. After one day, yellow crystals appeared in the cooler arm, which were
separated and washed by methanol. Yield 76% (0.468 g). Anal. Calcd for C24H24MnN4O12
(MW = 615.41): C, 46.84; H, 3.93; N, 9.10; Mn, 8.93 %. Found: C, 46.79; H, 3.88; N, 9.15; Mn,
8.97%. FT-IR (KBr, cm−1): 3392 (m, br), 3242 (w), 3063 (w), 2924 (w), 2856 (w), 1666 (vs), 1637
(m), 1608 (vs), 1562 (s), 1535(m), 1515 (m), 1455 (m), 1384 (vs), 1352 (m), 1272 (m), 1257 (w),
1220 (m), 1190 (w), 1149 (w), 1123 (w), 1085 (w), 1052 (w), 1040 (w), 1021 (w), 971 (m), 931
(m), 833 (w), 870 (w), 826 (w), 768 (m), 757 (m), 670 (w), 649 (w), 614 (m), 575 (w), 562 (w),
493 (m), 481 (m), 462 (w). UV–vis (2.5 × 10−5 M, CH3OH): λmax (ε, M−1 cm−1) = 234 (73,000), 303
(37,400), 332 (38,000).
2.5. Synthesis of [Mn(HL)(NO3)(CH3OH)]n (1b)
The compound was obtained from a similar reaction as 1a but time and temperature of
reaction were higher in this case. When the reaction temperature increased to 70 °C, small
amount of orange crystals also formed together with yellow crystals of 1a in the reaction
tube. The amount of red crystals increased after three days and the yellow crystals disap-
peared. After one week the orange crystals were isolated and washed with methanol. Yield
62% (0.322 g). Anal. Calcd for C23H19MnN3O8 (MW = 520.35): C, 53.09; H, 3.68; N, 8.08; Mn,
10.56 %. Found: C, 52.98; H, 3.61; N, 8.14; Mn, 10.63%. FT-IR (KBr, cm−1): 3420 (m, br), 3267
(w), 3041 (w), 2923 (m), 2853 (w), 1687 (vs), 1655 (w), 1629 (s), 1607 (vs), 1562 (w), 1525 (w),
1508 (w), 1458 (s), 1441 (m), 1423 (m), 1380 (w), 1355 (w), 935 (w), 1326 (s), 1321 (s), 1270
(m), 1238 (w), 1215 (w), 1171 (w), 1149 (w), 1118 (w), 1102 (w), 1039 (m), 1013 (s), 962 (w),

6
R. BIKAS ET AL.
946 (w), 921 (w), 908 (w), 872 (m), 844 (w), 815 (w), 779 (m), 750 (s), 726 (w), 671 (w), 618 (w),
590 (w), 568 (w), 509 (w), 476 (w), 459 (w). UV–vis (2.5 × 10−5 M, CH3OH): λmax (ε, M-1 cm−1) =
234 (69,100), 306 (29,000), 349 (31,000).
2.6. Synthesis of [Co(HL)(NO3)(CH3OH)]n (2)
Compound 2 was synthesized by reaction of Co(NO3)2·6H2O (0.291 g, 1 mmol) and H2L
(0.372 g, 1 mmol) in methanol with a procedure similar to that of 1a. Dark brown crystals of
2 formed after three days, were filtered off and washed with methanol. Yield 84% (0.440 g).
Anal. Calcd for C23H19CoN3O8 (MW = 524.34): C, 52.68; H, 3.65; N, 8.01; Co, 11.24 %. Found: C,
52.60; H, 3.60; N, 8.12; Co, 11.31 %. FT-IR (KBr, cm−1): 3406 (m, br), 3235 (m), 2920 (m), 2849
(m), 1684 (vs), 1628 (m), 1608 (vs), 1521 (w), 1483 (w), 1459 (m), 1445 (m), 1318 (w), 1384 (m),
1353 (w), 1334 (m), 1317 (s), 1269 (w), 1260 (w), 1218 (w), 1185 (w), 1174 (w), 1147 (w), 1139
(w), 1043 (w), 1014 (m), 973 (w), 946 (w), 907 (m), 873 (w), 851 (w), 819 (w), 790 (w), 775 (m),
754 (s), 671 (w), 631 (w), 619 (w), 568 (w), 515 (w), 478 (w), 463 (w), 442 (w). UV–vis (2.5 × 10−5 M,
CH3OH): λmax (ε, M−1 cm−1) = 234 (71,400), 272 (51,400), 387 (38,500). Solid UV–vis: 209, 252,
412 nm.
Table 1. Crystal data and structure refinement parameters for 1–4.
Compound
1a
1b
2
3
4
net formula
C
24h24mnn4o12
615.41
C23h19mnn3o8
520.35
0.03×0.08×0.32
100
C23h19Con3o8
524.34
0.05×0.06×0.08
90
C22h15Cun3o7
496.91
0.08×0.15×0.26
293
C23h19mnn5o5
500.37
0.08×0.14×0.35
293
Mr/g mol−1
Crystal size/mm
T/K
0.06×0.08×0.51
100
radiation
diffractometer
Crystal system
Crystal shape, color
moKα
moKα
moKα
moKα
moKα
Xcalibur, ruby
monoclinic
needle, yellow
P21/c
Xcalibur, ruby
triclinic
needle, orange
P1
Xcalibur, ruby
triclinic
Block, brown
P1
Xcalibur, eos
triclinic
Prism, brown
P-1
Xcalibur, eos
triclinic
Prism, orange
P1
space group
a/Å
b/Å
c/Å
α/°
β/°
8.150(2)
15.082(4)
20.993(6)
90
99.18(3)
90
2547.4(12)
4
1.605
7.346(2)
7.965(2)
10.507(3)
82.64(5)
74.46(5)
63.92(5)
532.0(4)
1
7.249(2)
7.882(2)
10.542(3)
82.38(5)
73.04(5)
64.25(5)
518.9(3)
1
7.8027(5)
8.2566(5)
15.7698(11)
80.827(5)
81.891(5)
86.052(5)
991.81(11)
2
7.4445(6)
7.7865(7)
10.7981(5)
79.493(8)
74.761(7)
62.308(9)
533.42(8)
1
γ/°
V/Å3
Z
Calc. density/g cm−3
1.624
0.68
1.678
0.89
1.664
1.16
1.558
0.67
μ/mm−1
0.59
F(000)
θ range/°
h
k
1268
267
269
506
257
2.9–28.8
−7→10
−20→19
−27→28
0.063
2.9–30.8
−9→10
−11→10
−14→11
0.049
2.9–30.7
−10→10
−6→11
−13→14
0.059
3.7–26.8
−9→9
−9→10
−16→19
0.021
3.7–23.3
−9→9
−9→9
l
−13→13
0.038
Rint
R(Fobs
)
0.060
0.163
0.067
0.178
0.066
0.101
0.042
0.107
0.055
0.08
Rw(F2)
S
1.00
1.00
0.97
1.00
1.00
abs. correction
measured reflections
independent
reflections
reflections with I
>2σ(I)
analytical
16,640
5970
analytical
6575
3770
analytical
4580
3533
analytical
5205
3739
analytical
5970
4001
4162
375
3205
322
2603
296
2956
303
3142
313
Parameters

JOURNAL OF COORDINATION CHEMISTRY
7
2.7. Synthesis of [Cu(HL)(NO3)] (3)
Dark green crystals of 3 were formed from reaction of Cu(NO3)2·3H2O and H2L in methanol
after two days by a procedure similar to that of 1a. Yield 88% (0.437 g). Anal. Calcd for
C22H15CuN3O7 (MW = 496.91): C, 53.18; H, 3.04; N, 8.46; Cu, 12.79 %. Found: C, 53.08; H, 2.94;
N, 8.52; Cu, 12.85%. FT-IR (KBr, cm−1): 3435 (m, br), 2923 (vs), 2853 (s), 1699 (s), 1643 (m), 1600
(m), 1558 (w), 1479 (w), 1460 (w), 1384 (w), 1310 (w), 1288 (w), 1243 (w), 1218 (w), 1170 (w),
1150 (w), 1118 (m), 1107 (w), 1079 (w), 1040 (m), 1013 (m), 990 (w), 929 (w), 876 (w), 857 (w),
773 (w), 759 (w), 746 (w), 659 (w), 612 (w), 590 (w), 526 (w), 489 (w), 476 (w), 423 (w).UV–vis
(2.5 × 10−5 M, CH3OH): λmax (ε, M−1 cm−1) = 233 (62,960), 300 (20,280), 384 nm (42,800).
2.8. Synthesis of [Mn(HL)(N3)(CH3OH)]n (4)
The complex was synthesized by a procedure similar to previous complexes in the branched
tube by a mixture of H2L (0.372 g, 1 mmol), Mn(NO3)2⋅4H2O (0.245 g, 1 mmol) and NaN3
(0.130 g, 2 mmol) in methanol. After three days, orange crystals appeared which were sep-
arated and washed by cold methanol. Yield 84% (0.420 g). Anal. Calcd for C23H19MnN5O5
(MW = 500.37): C, 55.21; H, 3.83; N, 14.00; Mn, 10.98. Found: C, 55.18; H, 3.81; N, 14.08; Mn,
11.03%. FT-IR (KBr, cm−1): 3428 (br,m), 3127 (w), 2924 (w), 2849 (w), 2049 (vs), 1687 (s), 1631
(m), 1607 (s), 1585 (w), 1562 (m), 1515 (w), 1451 (w), 1489 (w), 1455 (m), 1441 (m), 1417 (w),
1375 (w), 1354 (w), 1338 (w), 1319 (w), 1274 (w), 1257 (w), 1232 (w), 1218 (w), 1182 (w), 1143
(w), 1020 (m), 960 (w), 946 (w), 920 (w), 872 (w), 842 (w), 776 (w), 760 (s), 673 (w), 631 (m),
618 (w), 562 (w), 511 (w), 478 (w), 462 (w), 442 (w). UV–vis (in CH3OH, c = 2.5 × 10−5 M, λmax
[nm] with ε [M−1 cm−1]): 237 (54,400), 273 (13,300), 315 (5550), 363 nm (4000). Solid UV–vis:
248, 285, 405 nm.
2.9. X-ray crystal structure determination
Data collections for X-ray structure determination for 1a, 1b, and 2 were performed on an
Xcalibur R four-circle diffractometer with a Ruby CCD detector with graphite monochromated
MoKα radiation. Data were collected at 100(2) K (1a and 1b) or 90 K (2) using an Oxford
Cryosystems cooler. X-ray diffraction data of 3 and 4 were collected on an Xcalibur, Eos dif-
fractometer using Mo-Kα radiation at room temperature (293 K). Data collection, cell refine-
ment, data reduction, and absorption corrections were carried out with Xcalibur R software,
CrysAlisPro [23]. The structures were solved by direct methods with SHELXS/T [24] and refined
by full-matrix least-squares on F2 using SHELXL-2015 [24] with anisotropic thermal param-
eters for the non-H-atoms (except for some positions of disordered atoms). The hydrogens
were found in difference Fourier maps, but in the final refinement cycles they were
Table 2. selected ft-ir bands (cm−1) of h2l, 1a, 1b, 2, 3, and 4.
Compound
C=N
NH
C=O (amide)
C=O (ester)
OH
h2l
1a
1b
2
1604
1608
1607
1608
1600
1607
3269
3242
3267
3235
–
1658
1637
1629
1628
1643
1631
1708
1666
1687
1684
1699
1687
3412
3392
3420
3406
3435
3428
3
4
3127

8
R. BIKAS ET AL.
Figure 1. uV–vis spectra of h2l, 1a, 1b, 2, 3 and 4 in methanol.
repositioned in their calculated positions and refined using a riding model, with C–H = 0.95–
0.99 Å, and with Uiso(H) = 1.2Ueq(CH) or 1.5Ueq(CH3), except for amidic NH and methanol OH,
which were located in Fourier maps, refined isotropically and then were constrained to ride
on their parent atoms (AFIX 3 instruction in SHELXL-2015). The structure plots were prepared
with DIAMOND [25]. Details of structure refinements are given in Table 1.
3. Results and discussion
3.1. Synthesis and spectroscopy
The reaction of 3-hydroxy-2-naphthoic hydrazide with 3-acetyl-2H-chromen-2-one in meth-
anol gave a hydrazone Schiff base, H2L, in good yield and purity (Scheme 1). The formation
of H2L has been confirmed by elemental analysis, FT-IR and NMR spectroscopic studies. In the
FT-IR spectrum of H2L (Figure S3) bands at 1604, 1658, and 1708 are due to C=N, amidic C=O
and esteric C=O functionalities of the ligand [26]. The band at 3269 cm−1 is due to NH and
the broad band at 3412 cm−1 can be assigned to υ(–OH) of the naphtholic group involved in
intermolecular hydrogen bonding [27]. In the 1H NMR spectrum of H2L (Figure S4) two broad
singlets at δ 11.75 and 11.59 ppm are due to the naphtholic O–H and amidic N–H hydrogens.
The methyl hydrogens appear at δ 2.29 ppm and the peaks at δ 7.1–8.6 ppm are due to the
aromatic hydrogens. In the 13C NMR spectrum of H2L (Figure S5) the peaks at δ 162.05 and
153.92 ppm are related to amidic and ester C=O groups, respectively. The peaks of azomethine
carbon (C=N) and methyl (–CH3) are at δ 153.01 and 16.20 ppm, respectively.
Compounds 1a, 1b, 2, 3, and 4 were characterized by elemental analysis, spectroscopic
methods (FT-IR, UV–vis) and single crystal X-ray studies. Comparison of FT-IR spectra of com-
plexes (Figures S6–S10) with free ligand (Figure S3) provides some evidence for coordination
mode of ligand in complexes (see Table 2). In the FT-IR spectra of complexes the shifts in the
C=N vibration confirm coordination of azomethine nitrogen to the metal ions [28]. The shifts
in the position of esteric C=O band in the FT-IR spectrum of complexes relative to the free

JOURNAL OF COORDINATION CHEMISTRY
9
Figure 2. the structure of 1a with atom numbering scheme.
notes: Green dashed lines shows n−h⋯o and o−h⋯o hydrogen bonds.
Table 3. selected bond lengths (Å) and angles (°) for 1–4.
1a
1b
4
2
3
Bond
length/Å
2.212(2)
2.177(2)
length/Å
2.177(5)
2.140(5)
2.063(5)
2.181(5)
2.199(6)
2.342(6)
length/Å
2.151(6)
2.129(4)
2.092(5)
Bond
Co−o1
Co−o3
Co−o4i
Co−o1a
Co−o1m
Co−n1
length/Å
2.094(5)
2.086(4)
2.032(6)
2.105(5)
2.111(6)
2.184(7)
Bond
Cu−o1
Cu−o3
Cu−o1a
Cu−n2
length/Å
1.918(2)
1.889(2)
1.938(2)
1.924(2)
mn−o1
mn−o3
mn−o4i
mn−o1a
mn−o1m
mn−n1
mn−o1B
mn−o2B
mn−n3
C1−o1
2.265(2)
2.214(2)
2.349(3)
2.243(2)
2.408(2)
2.206(6)
2.349(7)
2.158 (7)
1.203 (8)
1.247 (7)
1.338 (8)
1.218(4)
1.248(4)
1.353(4)
1.224 (9)
1.239(9)
1.324(10)
1.210(7)
1.254(7)
1.335(8)
1.938(2)
1.280(3)
1.327(4)
C11−o3
C11−n2
angle
deg/°
deg/°
deg/°
angle
deg/°
angle
deg/°
n1−mn−o1
n1−mn−o3
n1−mn−o4i
o1−mn−o3
o1−mn−o4i
o3−mn−o4i
o1m−mn−
o1a
74.07(8)
71.79(8)
74.7(2)
72.1(2)
168.5(2)
144.88(19)
109.85(19)
104.9(2)
170.3(2)
75.2(2)
n1−Co−o1 79.1(2)
n1−Co−o3 76.0(2)
n1−Co−o4i 171.7(3)
o1−Co−o3 153.01(17)
o1−Co−o4i 101.6(2)
o3−Co−o4i 104.6(2)
o1−Cu−n2 92.92(10)
o3−Cu−n2 83.35(9)
o3−Cu−o1a 94.39(9)
o1−Cu−o1a 89.50(10)
n2−Cu−o1a 177.24(10)
72.79(2)
168.9(3)
147.63(16)
101.68(19)
110.7(2)
172.0(3)
140.73(8)
161.61(8)
o1m−Co−
174.4(3)
o1a
o1−mn−o1B
o3−mn−o2B
87.42(8)
77.06(8)
o1B−mn−o2B 55.12(8)
symmetry code: (i) x + 1, y, z.
ligand shows coordination of esteric oxygen to the metal ions. In the FT-IR spectra of 1a, 1b,
2, and 4 the band of NH and amidic C=O groups are seen at 3250 and 1640 cm−1, respectively,
confirming coordination of hydrazone to the metal in keto form. In the FT-IR spectrum of 3
the NH band is eliminated but the amidic C=O band is at 1643 cm−1. Elimination of NH and
the presence of C=O is frequently seen in our previous reports on naphthohydrazone-based
ligands [29]. This is related to the intramolecular O−H⋯N hydrogen bond which can affect

10
R. BIKAS ET AL.
Figure 3. (a) Pseudo-dinuclear unit formed by hydrogen bond interactions with uncoordinated methanol
in 1a. (b) 1-d polymeric chain formed by intermolecular hydrogen bonds (dashed lines) in the crystal
structure of 1a.
tautomerization [26]. In the FT-IR spectrum of all complexes a broad band is seen at 3400 cm−1
which can be attributed to υ(OH) and confirms the presence of methanol in the crystal
structures. There is a very strong band at 2049 cm−1 in the FT-IR spectrum of 4 which is due
to υ(N3) [30]. This is a new band in the FT-IR spectrum of complex and is not present in the
FT-IR spectrum of free ligand and shows azide is coordinated to manganese.
The electronic spectrum of H2L in methanol (Figure 1) displays bands at 235, 297, and
339 nm. Based on their extinction coefficients they are assigned to intraligand π→π* (235 nm)
and n→π* (297 and 339 nm) transitions. Electronic spectra of all complexes in methanol at
room temperature are shown in Figure 1. For all complexes intraligand transitions were
observed from 220–300 nm. Ligand to metal charge transfer (LMCT) transitions are observed
from 361–408 nm in the UV–vis spectrum of complexes. Solid-state UV–vis spectra of 2 and

JOURNAL OF COORDINATION CHEMISTRY
11
Table 4. hydrogen-bond geometry (Å, °) of 1a, 1b, 2, 3, and 4.
D–H⋯A
D–H
H⋯A
D⋯A
D–H⋯A
1a
o1m−h1m⋯o3ai
C1m−h1m1⋯o1
C1m−h1m2⋯o2ai
o2m−h2m⋯o1a
o4−h1⋯o2mii
n2−h2⋯o4
1b
0.84
0.98
0.98
0.84
0.84
0.91
2.09
2.50
2.53
1.93
1.76
1.88
2.925(3)
3.046(4)
3.119(4)
2.767(3)
2.590(3)
2.587(3)
173
115
118
173
171
133
o1m−h1m⋯o3aiii
o1m−h1m⋯n1aiii
C20−h20⋯o3i
C22−h22B⋯o1i
n2−h2⋯o4
2
0.84
0.84
0.95
0.98
1.97
2.59
2.40
2.50
2.745(8)
3.358(9)
3.247(9)
3.016(9)
2.584(8)
152
152
149
113
0.92(1)
1.80(6)
141(8)
n2−h2⋯o4
C20−h20⋯o3ii
C22−h22a⋯o1ii
C1m−h1mB⋯o4i
o1m−h1m⋯o3aiii
o1m−h1m⋯n1aiii
3
o4−h2⋯n1
C3−h3⋯o3av
4
n2−h2⋯o4
o1m−h1m⋯n5iii
C20−h20⋯o3i
C22−h22a⋯o1i
0.88
0.95
0.98
0.98
0.84
0.84
1.92
2.28
2.44
2.52
1.88
2.55
2.607(8)
3.139(10)
2.936(9)
3.155(9)
2.709(9)
3.325(9)
133
150
111
122
168
154
0.84
0.93
1.86(2)
2.40
2.601(3)
3.331(5)
146(3)
179
0.86
0.85(2)
0.93
1.86
1.92(3)
2.44
2.559(7)
2.748(9)
3.299(10)
3.101(9)
138
166(10)
154
0.96
2.53
118
symmetry codes: (i) x−1, y, z; (ii) −x, −y, −z; (iii); (v) x−1, y−1, −z.
4 (see Figure S11) are expected to show modest shifts in intra-ligand transition and LMCT
bands relative to those recorded in solution spectra, due to absence of solvent interaction
effects [31]. These compounds show similar solution intra-ligand and LMCT spectra, but in
solid state spectra the absorption bands are broad especially in the case of LMCT bands at
400 nm. Such broadness can be attributed to the high concentration and strong interaction
between molecules in the solid state.
3.2. Crystal structure of 1a
The structure of [Mn(H2L)(NO3)2(CH3OH)]·CH3OH (1a) is shown in Figure 2 and selected bond
lengths and angles are collected in Table 3. X-ray studies indicated that yellow crystals of
the reaction between H2L and Mn(NO3)2·4H2O are related to a neutral mononuclear manga-
nese(II) complex. In 1a the Schiff base ligand is a neutral tridentate ONO-donor ligand which
adopts both five- and six-member chelate rings when coordinated to the manganese core.
As shown in Figure 2, Mn(II) has a distorted pentagonal bipyramidal MnNO6 coordination
environment which is created by coordination of azomethine nitrogen, ester and amidic
oxygens from the hydrazone ligand, three oxygens from two nitrates, and an oxygen from
methanol. Two oxygens provided by a nitrate (O1A) and a coordinated methanol (O1 M)
occupy the axial positions. The equatorial plane is created by three ONO-donor atoms of the
hydrazone ligand and two oxygens from the second nitrate. The amidic N−H of hydrazone
forms intramolecular N−H⋯O hydrogen bonds and the naphtholic OH group (as a donor)

12
R. BIKAS ET AL.
Figure 4. (a) structure of 1b with atom numbering scheme (symmetry codes: (i): x + 1, y, z; (ii): x−1, y, z).
(b) 1-d polymeric chain of 1b along the a axis.
notes: Green dashed lines show n−h⋯o hydrogen bonds.
creates intermolecular O−H⋯O hydrogen bonds. A second methanol is located beside the
complex and acts as a linker between two molecules of complex by creating two strong
O−H⋯O hydrogen bonds. A pseudo-dimer forms by these hydrogen bonds (see Figure 3(a),
Table 4). The coordinated methanol also forms intermolecular O−H⋯O hydrogen bonds
with the oxygen of coordinated nitrate of the neighboring molecule. A 1-D polymeric chain
containing pseudo-dimer units forms by these interactions (Figure 3(b)). Moreover, there
are several C−H⋯O hydrogen bond interactions in the crystal structure of 1a which are
shown in Figure S12.

JOURNAL OF COORDINATION CHEMISTRY
13
Figure 5. 2-d polymeric network formed by intermolecular hydrogen bonds (dashed lines) in the crystal
structure of 1b.
3.3. Crystal structure of [Mn(HL)(NO3)(CH3OH)]n (1b)
The structure of 1b and its 1-D polymeric chain are shown in Figures 4(a) and (b), respectively,
and selected bond lengths and angles are collected inTable 3. According to structural studies
it is clear that the naphtholate OH deprotonates at higher temperature (or with time) and
replaces the equatorial nitrate in the structure of 1a. Coordination polymer 1b is generated
by this replacement. Mn(II) has a distorted octahedral coordination environment which is
generated by coordination of a nitrogen and three oxygens from hydrazone ligand and two
oxygens from coordinated nitrate and methanol. The hydrazone acts as both chelating and
bridging ligand in the formation of 1-D polymeric chain. Three ONO-donor pockets of ligand
(ester oxygen, azomethine nitrogen, and amidic oxygen) coordinate to one Mn(II) ion and
the naphtholate oxygen coordinates to the neighboring Mn(II) to form the polymeric chain
(Figure 4(b)). In 1b the hydrazone ligand remained in keto form and the hydrogen on the
nitrogen takes part in intramolecular hydrogen bonds with the deprotonated phenolic oxy-
gen, N2−H2⋯O4 (see Table 4). Therefore, the hydrazone is a tetradentate mononegative
ligand, (HL)−. Four donors of HL− form the equatorial plane of octahedral geometry around
Mn(II) and the axial positions are occupied by oxygens of methanol and nitrate. The OH of
methanol involves an intermolecular hydrogen bond with the oxygen of the nitrate from
the neighboring polymeric chain. Consequently, the 1-D polymeric chain converts to a 2-D
polymeric network in the ab crystallographic plane by these O−H⋯O hydrogen bond inter-
actions (Figure 5). Mn−N and Mn−O bond lengths in both 1a and 1b are in the normal range
reported for other Mn(II)–hydrazone complexes [32].
3.4. Crystal structure of [Co(HL)(NO3)(CH3OH)]n (2)
Crystallographic analyses reveal that the crystal structure of 2 is similar to the crystal structure
of 1b and is a 1-D coordination polymer of Co(II). The main difference of 2 and 1b is that the

14
R. BIKAS ET AL.
Figure 6. (a) the structure of 2 with atom numbering scheme (symmetry codes: (i): x + 1, y, z; (ii): x−1, y,
z). (b) 1-d polymeric chain of 2 along the a axis.
notes: Green dashed lines show n−h⋯o hydrogen bonds.
Co(II) is in 2 while Mn(II) is in 1b; the other features are very close to each other in these
compounds. Molecular structure and polymeric chain of 2 are shown in Figures 6(a) and (b),
respectively. Selected bond lengths and angles are given in Table 3 and the 2-D polymeric
network obtained by intermolecular hydrogen bond interactions is shown in Figure S13.
Like 1b, the Schiff base ligand is coordinated to Co(II) as a tetradentate mononegative ligand,
(HL)−, and forms the equatorial plane of octahedral geometry around the metal ions. The
axial positions are occupied by oxygen of coordinated nitrate and methanol. The structure
is stabilized by intramolecular N−H⋯O and intermolecular O−H⋯O hydrogen bond inter-
actions (see Table 4). The Co−N and Co−O bond lengths are in the normal range reported
for other Co(II) complexes [33].

JOURNAL OF COORDINATION CHEMISTRY
15
Figure 7. (a) molecular structure of 3 with atom numbering scheme. (b) the π⋯π interactions in the
crystal structure of 3 shown as pink dashed lines. Green dashed lines show o−h⋯n hydrogen bonds.
3.5. Crystal structure of [Cu(HL)(NO3)] (3)
The structure of 3 is shown in Figure 7(a) and selected interatomic distances and angles are
collected in Table 3. Complex 3 is a mononuclear complex of Cu(II) with a distorted square
planar coordination geometry. Three donors from the hydrazone (azomethine nitrogen,
ester oxygen and enolate oxygen) together with oxygen of a nitrate form the coordination
environment of Cu(II). The amidic N−H of the hydrazone ligand is eliminated during the
formation of complex. Due to this, the hydrogen of the O−H group of naphtholate is oriented
to the inside part of the ligand to form an intramolecular O−H⋯N hydrogen bond. Therefore,
the Schiff base is coordinated to Cu(II) as a tridentate mononegative ligand, (HL)−. In 3 the
negative charge is provided by removing the hydrogen of amidic N−H. The crystal structure
of 3 is stabilized by intermolecular C–H⋯O hydrogen bonds (see Figure S14) and π⋯π
(Figure 7(b)) interactions.

16
R. BIKAS ET AL.
Figure 8. (a) the structure of 4 with atom numbering scheme (symmetry codes: (i): x + 1, y, z; (ii): x−1, y,
z). (b) 1-d polymeric chain of 4 along the a axis.
notes: Green dashed lines show n−h⋯o hydrogen bonds.
Figure 9. 2-d polymeric network formed by intermolecular hydrogen bonds (dashed lines) in the crystal
structure of 4.

JOURNAL OF COORDINATION CHEMISTRY
17
3.6. Crystal structure of [Mn(HL)(N3)(CH3OH)]n (4)
Since the azide has high potential to bridge between transition metal ions to form multinu-
clear complexes or coordination polymers, the reaction of H2L with Mn(NO3)2·4H2O was car-
ried out in the presence of sodium azide in order to investigate the changes in coordination
behavior of H2L in the presence of azide. The structure of crystals obtained by this reaction
is shown in Figure 8(a) and selected bond lengths and angles are given in Table 3. The struc-
tural studies revealed that the product is a 1-D coordination polymer of Mn(II) (Figure 8(b))
which generally is similar to 1b, just the nitrate of 1b is replaced by azide. This reaction reveals
that the 1-D polymeric chain is quite stable with mononegative ligands (like azide) and only
the nitrates are replaced by the azide ligands. Similar to 1b, the coordinated methanol in the
axial position involves an intermolecular hydrogen bond interaction to form the 2-D poly-
meric network. In 4 the nitrogen of the azide is a hydrogen bond acceptor (see Figure 9). The
N3−N4−N5 angle in azide is 178.9(9)° and the N3−N4 and N4−N5 bond lengths are 1.166(8)
Å and 1.168(8) Å, respectively, which are in the normal range for azide ligands [30].
Comparing the bond lengths of ester C=O bonds in the crystal structure of 1–4 (≈ 1.22
Å) with free 3-acetyl-2H-chromen-2-one (1.207–1.211 Å) [34] indicates that they are longer
in 1–4, attributed to coordination of oxygen to the metal core. This is also in agreement with
the red shift of υ(C=O) in the FT-IR spectrum of complexes in comparison to the free ligand.
Moreover, the N2−C11 and C11−O3 bond lengths in 1a, 1b, 2, and 4 are ≈ 1.34 Å and ≈ 1.245
Å, respectively. Comparison of these bond lengths with free hydrazone (C−N ≈ 1.34 Å and
C=O ≈ 1.23 Å) [35] shows that they are quite close to each other and confirms the coordina-
tion of ligand to metal in keto form without elimination of NH. The C11−N2 and C11−O3
bond lengths in 3 are 1.280(3) Å and 1.327(4) Å, respectively. In 3 the C−N bond length is
shorter while the C−O bond length is longer in comparison to 1a, 1b, 2, and 4, confirming
elimination of NH and the presence of keto-enol tautomerization in the N2−C11−O3 moiety
of hydrazone ligand when coordinated to Cu(II). However, the C−N and C=O bond lengths
are not so close to the C−N and C=O bond lengths in coordinated hydrazone ligands in enol
form [36]. This can be attributed to intramolecular O−H⋯N hydrogen bond interaction in
the crystal structure of 3 which can affect the keto-enol tautomerism and is also confirmed
by FT-IR spectrum. This is in agreement with our previous observations on 3-hydroxy-2-naph
thohydrazone-based ligands [29].
-
3.7. Thermal studies
The thermal stabilities of 2 and 4 were studied by heating the samples at a control rate of
10 °C per minute under nitrogen. The thermal decomposition patterns for 2 and 4 are close
to each other and have three decomposition steps. The thermogravimetric curve of 2 (Figure
S15) shows the loss of coordinated methanol at 80–207 °C (Calcd 0.295 mg, 6.10%; Obs.
0.303 mg, 6.25%). The thermogram further shows decomposition at 210–285 °C which can
be attributed to the loss of nitrate (Calcd 0.573 mg, 11.82%; Obs. 0.576 mg, 11.89%). The final
decomposition in the region 320–450 °C is due to loss of hydrazone ligand (Calcd 71.02%
and Obs. 69.02%) and the final product is estimated to be Co3O4 (Calcd remaining
mass = 0.741 mg, 15.29% and Obs. 0.727 mg, 15.00%). The thermogram curve of 4 (Figure
S16) shows that the complex starts decomposing at 80 °C by removing the coordinated

18
R. BIKAS ET AL.
methanol at 80–250 °C (Calcd 0.695 mg, 6.40%; Obs. 0.704 mg, 6.48%). In the next step the
azide is lost at 290–310 °C (Calcd 0.911 mg, 8.39%; Obs. 0.961 mg, 8.84%). The decomposition
between 300 and 440 °C shows loss of hydrazone ligand and finally the coordination polymer
is converted into metal oxide, estimated to be Mn2O3 (Calcd remaining mass = 1.72 mg,
15.83% and Obs. 1.75 mg, 16.11%).
4. Conclusion
A coumarin-naphthohydrazone ligand was synthesized and characterized by elemental
analysis and spectroscopic methods. The coordination behavior of ligand was investigated
by its reaction with Mn(II), Co(II), and Cu(II) nitrates in methanol. The coordination compounds
were characterized by elemental analysis and spectroscopic methods and were further stud-
ied by single crystal X-ray analysis. The ligand showed a rare coordination mode, acting as
both chelating and bridging ligand to form 1-D coordination polymers with Mn(II) and Co(II)
ions. Mononuclear Mn(II) and Cu(II) complexes were also obtained by this ligand. Employing
azide as a potentially bridging ligand did not change the coordination mode of ligand and
a similar 1-D coordination polymer was obtained by replacing nitrate anion with azide.
Supplementary material
CCDC 1548163–1548167 contain the supplementary crystallographic data for 1a, 1b, 2, 3 and 4, respec-
tively. These data can be obtained free of charge from the Cambridge Crystallographic Data Center
via http://www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can
be found in the online version.
Acknowledgements
The authors are grateful to Imam Khomeini International University, the University of Zanjan and
Dokuz Eylül University for support of this study. M. Aygün acknowledges Dokuz Eylül University for
the use of the Oxford Rigaku Xcalibur Eos Diffractometer (purchased under University Research [grant
number 2010.KB.FEN.13].
Disclosure statement
No potential conflict of interest was reported by the authors.
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