Synthesis and characterization of a thioether Schiff base ligand and its metal complexes and crystal structure determination of the nickel(II) complex

Article abstract of DOI:10.1080/00958972.2015.1091925

Reactions of 1,2-di(o-aminophenylthio)ethane with 3-ethoxy-2-hydroxybenzaldehyde yield the new hexadentate N₂S₂O₂ donor thioether Schiff base 1,2-bis(2-((2-(thio)phenylimino)methyl)-6-ethoxyphenol)ethane (H₂L). Ni(II), Zn(II), Cd(II), and Hg(II) complexes of this ligand were prepared. Of these complexes, [NiL]·2H₂O has been structurally characterized by X-ray crystallography. The coordination geometry around Ni(II) was described as octahedral. Zn(II), Cd(II), and Hg(II) complexes and the Schiff base ligand have been characterized by CHN analyses, molar conductivity, UV-vis, FT-IR, ¹H, and ¹³C NMR spectroscopy.

Full text of DOI:10.1080/00958972.2015.1091925

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Synthesis and characterization of a thioether
Schiff base ligand and its metal complexes and
crystal structure determination of the nickel(II)
complex
Ahmad Ali Dehghani-Firouzabadi, Hadi Kargar, Safie Eslaminejad & Behrouz
Notash
To cite this article: Ahmad Ali Dehghani-Firouzabadi, Hadi Kargar, Safie Eslaminejad &
Behrouz Notash (2015): Synthesis and characterization of a thioether Schiff base ligand and
its metal complexes and crystal structure determination of the nickel(II) complex, Journal of
Coordination Chemistry, DOI: 10.1080/00958972.2015.1091925
To link to this article: http://dx.doi.org/10.1080/00958972.2015.1091925
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Date: 14 September 2015, At: 10:19

Publisher: Taylor & Francis
Journal: Journal of Coordination Chemistry
DOI: http://dx.doi.org/10.1080/00958972.2015.1091925
Synthesis and characterization of a thioether Schiff base ligand and its metal
complexes and crystal structure determination of the nickel(II) complex
AHMAD ALI DEHGHANI-FIROUZABADI∗†, HADI KARGAR‡, SAFIE ESLAMINEJAD‡ and
BEHROUZ NOTASH§
†Department of Chemistry, Faculty of Science, Yazd University, 89195-741 Yazd, Iran
‡Department of Chemistry, Payame Noor University, P.O. Box 19395-3697 Tehran, I. R. Iran
§Chemistry Department, Shahid Beheshti University, G. C., Evin, Tehran 1983963113, Iran
Reactions of 1,2-di(o-aminophenylthio)ethane with 3-ethoxy-2-hydroxybenzaldehyde yield the
new hexadentate N2S2O2 donor thioether Schiff base 1,2-bis(2-((2-(thio)phenylimino)methyl)-6-
ethoxyphenol)ethane (H2L). Ni(II), Zn(II), Cd(II) and Hg(II) complexes of this ligand were
prepared. Of these complexes, [NiL]·2H2O has been structurally characterized by X-ray
crystallography. The coordination geometry around Ni(II) was described as octahedral. Zn(II),
Cd(II) and Hg(II) complexes and the Schiff base ligand have been characterized by CHN
analyses, molar conductivity, UV-Vis, FT-IR, 1H and 13C NMR spectroscopy.
Keywords: Schiff base complex; Hexadentate ligand; Nickel(II) complex; Thioether ligand;
N2S2O2 Donor
1. Introduction
The complexation properties of thioether donor ligands have been studied [1-3]. Such ligands
usually form strong bonds with soft metals and more rarely with hard ones. They are considered
both poor σ-donor and poor π-acceptor ligands. This π-acceptor character can contribute to the
M-S bond strength. In addition, their trans influence is lower than that of phosphines and higher
than that of primary amines [4, 5]. One of the synthetic methods for preparation of thioethers
derivatives has been reported by the reaction of thiols with organic halides [6-8]; di-, tri- and
poly-thioether ligands have been obtained by this method [3, 9-13]. Thioether ligands with other
donors such as nitrogen and oxygen, due to the presence of hard and soft donors, are of special
∗Corresponding author. Email: aadehghani@yazd.ac.ir

interest to chemists and bioinorganic chemists. These ligands have structural similarities with
natural biological systems and readily coordinate with a range of transition metal ions [14, 15].
Some thioether donor ligands are Schiff bases obtained by condensation of different types
of thioether amines with various ketones and aldehydes [8, 9, 16-18], and many of these are
hexadentate ligands [3, 19, 20]. N2S2O2 donor Schiff base ligands are hexadentate ligands that
have hard and soft donors in its structure. These ligands are promising from the view point of
coordination chemistry because of their ability toward complexation and involvement in a wide
range of biological and non-biological processes [21-23]. The presence of both hard and soft
donors in N2S2O2 donor Schiff base ligands allow coordination with a wide range of transition
metal ions and several metal complexes with N2S2O2 donor Schiff base ligands have been
reported [23-27].
The stability of metal complexes with polydentate ligands depends on factors such as the
number and type of donors present, their relative positions within the ligand, the nature of the
ligand backbone, and the number and size of chelate rings formed on complexation. Herein, we
present the synthesis and characterization of a N2S2O2 donor Schiff base derived from
1,2-di(o-aminophenylthio)ethane and 3-ethoxy-2-hydroxybenzaldehyde (scheme 1). This ligand
shows all of the previously mentioned properties and Ni(II), Zn(II), Cd(II), Hg(II) complexes of
this N2S2O2 donor thioether Schiff base ligand have been synthesized. 1H NMR data for Zn(II)
and 1H and 13C NMR data for Cd(II) and Hg(II) complexes are presented with correlations to
their structures and the X-ray structural analysis of Ni(II) complex displayed thioether
coordination. On the basis of X-ray crystallography we conclude that the ligand is hexadentate
and nickel(II) complex is assigned distorted octahedral structure.
S
S
O
NH2
S
H2N
S
OH
O
N
N
EtOH
Reflux
2
+
HO
OH
O
O
Scheme 1. Synthesis of H2L.

2. Experimental
2.1. Chemical and starting materials
2-Aminothiophenol, 1,2-dibromoethane, 3-ethoxy-2-hydroxybenzaldehyde,
Ni(CH3COO)2·4H2O, Zn(CH3COO)2·2H2O, Cd(CH3COO)2·2H2O and Hg(CH3COO)2 were
commercial products (from Merck, Aldrich and Fluka) and used without purification. Other
reagents and solvents were of analytical grade and purchased commercially.
2.2. Instrumentation
The elemental analyses were performed in a CHNS-O-2400 II Perkin-Elmer. Conductivity
measurements were carried out in 10-3 mol dm-3 CH3CN or DMF solutions at 25 °C using a
Metrohm 660 conductometer. The electronic spectra were taken in a GBC UV-Visible Cintra
101 spectrophotometer with 1 cm quartz cell in the range 200–1100 nm at 25 °C. Infrared spectra
were recorded in ATR using a Bruker FT-IR Equinax-55 spectrophotometer (4000–400 cm-1).
1H and 13C NMR spectra were taken in CDCl3 on Bruker NMR 500 and 400 MHz spectrometers
using Si(CH3)4 as an internal standard.
2.3. X-ray crystal structure determination
Single crystal of Ni(II) complex suitable for X-ray analyses was selected from those obtained by
open evaporation of ethanolic solution of the reaction mixture at 298 K. The details of the X-ray
crystal data and of the structure solution and refinement are given in table 1. The X-ray
diffraction measurements were made on a STOE IPDS-G diffractometer with graphite
monochromated Mo Kα radiation (λ = 0.71073 Å). Cell constants and an orientation matrix for
data collection were obtained by least-squares refinement of diffraction data from 3871 unique
reflections. The structure was solved by direct methods and refined on F2 by a full-matrix least-
squares procedure using anisotropic displacement parameters for all non-hydrogen atoms.
Hydrogens were located in their calculated positions and refined using a riding model.
2.4. Synthesis of the 1,2-di(o-aminophenylthio)ethane
The 1,2-di(o-aminophenylthio)ethane was prepared by reaction of 2-aminothiophenol and
sodium with 1,2-dibromoethane according to the procedure of Cannon et al. [28].

2-Aminothiophenol (12.5 g, 0.1 mol) was added to ethanol (40 mL) containing sodium (2.31 g,
0.1 mol). 1,2-Dibromoethane (4.27 g, 0.05 mol) in ethanol (40 mL) was added during 30 min to
the refluxing solution. The mixture was cooled, poured into water (100 mL), filtered off, washed
well with water and dried in vacuo. Recrystallization from ethanol yielded 9.8 g (71%). IR
(ATR, cm-1) 3387, 3291, 1616 ν(NH2); 749 ν(C-S); 1H NMR (CDCl3, ppm): δH 2.83 (4H, s),
4.0-4.5 (4H, br), 6.68 (1H, t), 6.73 (1H, d), 7.12 (1H, t), 7.28 (1H, d); 13C NMR (CDCl3, ppm):
δC 34.6, 115.1, 118.7, 130.0, 136.2, 148.6, 154.7.
2.5. Synthesis of 1,2-bis(2-((2-(thio)phenylimino)methyl)-6-ethoxyphenol)ethane (H2L)
A solution of 1,2-di(o-aminophenylthio)ethane (1.38 g, 5 mmol) in ethanol (30 mL) was added
dropwise to a refluxing solution of 3-ethoxy-2-hydroxybenzaldehyde (1.66 g, 10 mmol) in
ethanol (20 mL). After refluxing for 8 h the solution was vacuum evaporated to yield the crude
product as a yellow precipitate (scheme 1). Yield: 2.4 g (84%). Anal. Calc. for C32H32N2O4S2: C,
67.11; H, 5.63; N, 4.89%. Found: C, 66.97; H, 5.53; N, 5.02%; IR (ATR, cm-1) 1608 ν(C=N);
735 ν(C-S); 1H NMR (CDCl3, ppm): δH 1.53 (6H, J = 6.8 Hz, t), 3.14 (4H, s), 4.18 (4H, J =
6.8 Hz, q), 6.87 (2H, t), 7.03 (4H, d), 7.20-7.33 (8H, m), 8.62 (2H, s), 13.45 (2H, s); 13C NMR
(CDCl3, ppm): δC 14.92, 31.54, 64.59, 116.32, 117.91, 118.57, 119.32, 123.94, 126.88, 127.56,
128.40, 131.60, 146.96, 147.80, 156.55, 162.23; UV-Vis in CH3CN (λ, nm) 308 (logε = 3.32),
362 (logε = 3.12); Λm (CH3CN) 3.42 Ω-1 cm2 mol-1.
2.6. General synthesis of the complexes
A solution of the corresponding metal salt (1 mmol) in ethanol (30 mL) was added dropwise to
the solution of N2S2O2 ligand (H2L) (0.573 g, 1 mmol) in ethanol (20 mL) and the reaction
mixture was stirred for 5 h. The solution was then concentrated in a rotary evaporator to
ca. 5-10 mL. The complexes were filtered off, washed with cold ethanol and air dried
(scheme 2). Crystal of [NiL]·2H2O suitable for X-ray work was obtained by slow evaporation of
ethanolic solution of the complex.

S
S
S
S
M2+
M2+=Ni, Zn, Cd, Hg
EtOH
N
N
N
N
O
O
HO
OH
O
O
O
O
Scheme 2. Synthesis of the complexes.
[Zn(L)]·2H2O
Yield: 407 mg (61%). Anal. Calc. for C32H34N2O6S2Zn: C, 57.18; H, 5.10; N, 4.17%. Found: C,
56.48; H, 4.94; N, 3.80%; IR (ATR, cm-1) 1608 ν(C=N); 752 ν(C-S); 1H NMR (CDCl3, ppm): δH
1.53 (6H, J = 8 Hz, t), 3.14 (4H, s), 4.16 (4H, J = 8 Hz, q), 6.86-7.37 (12H, m), 8.58 (2H, s);
13C NMR (CDCl3, ppm): δC 14.8, 31.5, 64.7, 116.3, 117.9, 118.6, 119.4, 124.0, 126.9, 127.6,
128.4, 131.6, 147.0, 147.9, 151.5, 162.2; UV-Vis in CH3CN (λ, nm) 310 (logε = 3.47), 422
(logε = 3.18); Λm (CH3CN) 3.95 Ω-1 cm2 mol-1.
[Cd(L)]·4H2O
Yield: 581 mg (77%). Anal. Calc. for C32H38CdN2O8S2: C, 50.89; H, 5.07; N, 3.71%. Found: C,
50.15; H, 4.72; N, 3.23%; IR (ATR, cm-1) 1609 ν(C=N); 751 ν(C-S); 1H NMR (CDCl3, ppm):
δH 1.53 (3H, J = 9 Hz, t), 1.54 (3H, J = 9 Hz, t), 3.15 (4H, s), 4.17 (2H, J = 9 Hz, q), 4.18 (2H,
J = 9 Hz, q), 6.87 (2H, J = 7 Hz, t), 7.03 (4H, J = 8 Hz, t), 7.20-7.30 (6H, m), 7.32 (2H, J = 9 Hz,
d), 8.62 (2H, s); 13C NMR (CDCl3, ppm): δC 14.9, 31.5, 64.6, 116.3, 117.9, 118.6, 119.3, 123.9,
126.9, 127.6, 128.4, 131.6, 146.9, 147.8, 151.4, 162.2; UV-Vis in CH3CN (λ, nm) 309 (logε =
3.40), 427 (logε = 3.01); Λm (CH3CN) 4.83 Ω-1 cm2 mol-1.
[Hg(L)]·H2O
Yield: 602 mg (76%). Anal. Calc. for C32H32HgN2O5S2: C, 48.69; H, 4.09; N, 3.55%. Found: C,
48.41; H, 4.10; N, 3.47%; IR (ATR, cm-1) 1608 ν(C=N); 751 ν(C-S); 1H NMR (CDCl3, ppm):
δH 1.53 (6H, J = 9 Hz, t), 3.14 (4H, s), 4.18 (4H, J = 9 Hz, q), 6.89 (2H, J = 7 Hz, t), 7.03 (4H,

J = 7 Hz, t), 7.20-7.35 (8H, m), 8.62 (2H, s); 13C NMR (CDCl3, ppm): δC 14.9, 31.6, 64.6, 116.3,
117.9, 118.6, 119.3, 124.0, 126.9, 127.6, 128.4, 131.6, 147.0, 147.8, 151.6, 162.2; UV-Vis in
DMF (λ, nm) 308 (logε = 3.32), 383 (logε = 3.14); Λm (DMF) 60.94 Ω-1 cm2 mol-1.
[Ni(L)]·2H2O
Yield: 498 mg (75%). Anal. Calc. for C32H34N2O6S2Ni: C, 57.76; H, 5.15; N, 4.21%. Found: C,
58.46; H, 4.79; N, 4.33%; IR (ATR, cm-1) 3383 ν(O-H); 1598 ν(C=N); 766 ν(C-S); UV-Vis in
DMF (λ, nm) 307 (logε = 3.35), 455 (logε = 3.22), 562 (logε = 2.31), 754 (logε = 2.06); Λm
(DMF) 12.96 Ω-1 cm2 mol-1.
3. Results and discussion
The IR spectrum for 1,2-di(o-aminophenylthio)ethane shows bands at 3387, 3291 and 1616 cm-1
assignable to the aromatic primary amine vibrations and a band at 749 cm-1 due to the thioether
stretch. The IR spectrum for H2L confirms the presence of imine (1608 cm-1) and the absence of
carbonyl and amine functional groups of the starting materials. The vibration peak of C-S is
observed at 735 cm-1. In IR spectra of Cd(II), Zn(II) and Hg(II) complexes, the band at 1608 cm-1
or 1609 cm-1 is associated with ν(C=N) vibration and the vibrations of C-S are at 751 cm-1 or
752 cm-1. In the IR spectrum for Ni(II) complex, the band at 1598 cm-1 is associated with ν(C=N)
vibration and the vibration of C-S at 766 cm-1. The vibration of C-S is shifted relative to the
similar band of the ligand that shows the thioether sulfur coordinated to the metal ion. Also there
is an intense broad band centered at ~3383 cm-1 consistent with the presence of water as
observed from the X-ray data.
1H NMR and 13C NMR results, obtained for prepared compounds at ambient temperature
in CDCl3, are presented in Section 2. 1H and 13C NMR spectra of the amine indicate that this
compound was synthesized. The slightly broad signal at δH 13.45 ppm in the 1H NMR spectrum
of ligand is assigned to OH and CH=N protons of ligand exhibit a singlet at δH 8.62 ppm. The
1H NMR spectrum of ligand shows the aromatic ring protons from δH 6.87-7.33 ppm and the
aliphatic protons at δH 1.53-4.18 ppm. The 13C NMR spectrum of ligand features 16 signals, as
expected for the symmetry of the ligand. In this spectrum, azomethine carbon resonance is at
162.23 ppm and carbon resonances for CH3, SCH2 and OCH2 are at 14.92, 31.54 and 64.59 ppm,
respectively. The resonances for the aromatic ring carbons are from 116.32-156.55 ppm. The

1H NMR spectra of Zn(II), Cd(II) and Hg(II) complexes exhibit a singlet at δH 8.58-8.62 ppm,
which has been assigned to the azomethine proton (CH=N) and these spectra exhibit the aromatic
ring protons at δH 6.86-7.37 ppm and the aliphatic protons from δH 1.53-4.18 ppm. Cd(II)
complex exhibits two triplets at 1.53 ppm and 1.54 ppm, corresponding to methyl protons and
two quartets at 4.17 ppm and 4.18 ppm, corresponding to methylene protons (figure 1). This
indicates that the two ethyl protons are in different magnetic environments. In the 13C NMR
spectra of Zn(II), Cd(II) and Hg(II) complexes, azomethine carbon resonances are at 162.2 ppm
and the carbon resonances for CH3, SCH2 and OCH2 are from 14.9-64.7 ppm. The resonances for
the aromatic ring carbons are from 116.3-151.6 ppm.
The electronic spectrum of H2L shows two absorptions at 308 nm (logε = 3.32) and
362 nm (logε = 3.12); the band at 362 nm is the n→π* transition, while the 280 nm band
involves a π→π* transition. The electronic spectrum in solution agrees well with the pseudo-
octahedral geometry for the nickel(II) complex. This complex shows a band at 307 nm (logε =
3.35, π→π*) and three bands at 455 nm (logε = 3.32) assigned as a metal→ligand charge transfer
band, 562 nm (logε = 2.31) and 754 nm (logε = 2.06) assigned as d→d transitions. The electronic
spectra of the Zn(II), Cd(II) and Hg(II) complexes show absorptions at 308-310 nm (logε = 3.32-
3.47) and 383-427 nm (logε = 3.01-3.18). The band at higher energy is attributable to π→π*
transition and the band at low energy arises from metal→ligand charge transfer band [3].
The molar conductance values for H2L, Zn(II) and Cd(II) complexes measured in CH3CN
solution (1×10-3 mol dm-3) are 3.42-4.83 Ohm-1 cm2 mol-1 and Hg(II) and Ni(II) complexes
measured in DMF solution (1×10-3 mol dm-3) are 12.97-60.94 Ohm-1 cm2 mol-1. These observed
values of the molar conductance are well within the expected range for non-electrolytes [29].
Also, the elemental analyses of the complex indicated the absence of counter ions in the formula.
3.1. Description of the crystal structure
The structure of [NiL], determined by single crystal X-ray diffraction, is shown in figure 2.
Selected bond lengths, bond angles and hydrogen bonds are given in tables 2 and 3. The
molecular structure of the complex has a distorted octahedral geometry around the Ni(II) center,
as can be judged from spread in its observed angles [84.89(10)-95.25(18)°] and the trans angles
[173.5(2)-176015(9)°]. The Schiff base ligand is a hexadentate ligand through both thioether
sulfurs (cis coordinated with a bond angle of 88.52(6)°), both imine N (trans coordinated with a

bond angle of 173.5(2)°) and both phenolic O (cis coordinated with a bond angle of 95.25(18)°).
Thus the Ni(II) is bound through N2O2S2 donors. The bond lengths found in the structure are
within the normal ranges for this geometry (Ni-S 2.4067(12) Å, Ni-N 2.045(3) Å and Ni-O
2.000(3) Å). Nickel is in the plane formed by the two oxygens and two sulfurs and the sum of
four angles in this plane is 360.06°. The angle between this plane and the plane including the
metal and the two axial nitrogens, N1 and N1a, is 87.16°. In each molecular unit of the complex,
two waters have hydrogen bond interactions with the Schiff base ligand through O(3)−
H(3)….O(1) and C(7)−H(7)…O(3). The phenolic oxygens have strong hydrogen bond
interactions with hydrogen from water and four units of [NiL]·2H2O are present in its unit cell
(figure 3).
4. Conclusion
We report the synthesis of a new hexadentate N2S2O2 donor thioether Schiff base (H2L) and
prepared Ni(II), Zn(II), Cd(II) and Hg(II) complexes of this ligand. The complexes have been
characterized by spectroscopic methods. In addition the solid state structure of [NiL]·2H2O
shows that the ligand is hexadentate with a distorted octahedral geometry around the Ni(II)
center.
Appendix A. Supplementary data
CCDC 1042129 contains the supplementary crystallographic data for [NiL]·2H2O. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: (+44)
1223-336-033; or E-mail: deposit@ccdc.cam.ac.uk.
Acknowledgements
We are grateful to the Department of Chemistry Yazd University, Payame Noor University,
Shahid Beheshti University and Ministry of Science, Research and Technology of Iran, for
financial support.

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Table 1. Crystal data and structure refinement for [NiL]·2H2O.
Empirical formula
Formula weight
Temperature
C32H34N2NiO6S
665.44
120(2) K
0.71073 Å
Monoclinic
C 2/c
Wavelength
Crystal system
Space group
Unit cell dimensions
a = 20.855(4) Å
b = 8.0536(16) Å β = 94.17(3)°
c = 17.285(3) Å
Volume
2895.5(10) Å3
Z
4
Density (calculated)
Absorption coefficient
F(000)
1.526 Mg/m3
0.864 mm-1
1392
Crystal size
0.20 × 0.15 × 0.08 mm3
θ range for data collection
Limiting indices
2.71 to 29.21°
-24≤h≤28, -11≤k≤10, -23≤l≤23
11465 / 3871 [R(int) = 0.1114]
29.21, 98.8 %
Reflections collected / unique
Completeness to θ =
Absorption correction
Max. and min. transmission
Refinement method
Data / restraints / parameters
Goodness-of-fit on F2
Final R indices [I>2σ(I)]
R indices (all data)
Largest diff. peak and hole
Numerical
0.9341 and 0.8461
Full-matrix least-squares on F2
3871 / 2 / 211
1.055
R1 = 0.0719, wR2 = 0.1226
R1 = 0.1197, wR2 = 0.1370
0.479 and -0.503 e.Å-3

Table 2. Selected bond lengths (Å) and angles (deg) for [NiL]·2H2O.
Bond lengths
d (Å)
Bond angles
a (°)
Ni(1)-O(1)
Ni(1)-O(1a)
Ni(1)-N(1)
Ni(1)-N(1a)
Ni(1)-S(1)
Ni(1)-S(1a)
S(1)-C(1)
2.000(3)
2.000(3)
2.045(3)
2.045(3)
2.4067(12)
2.4066(12)
1.770(4)
1.827(5)
1.305(4)
1.295(5)
1.417(5)
1.380(4)
1.509(9)
1.437(5)
1.438(5)
O(1)-Ni(1)-O(1a)
O(1)-Ni(1)-N(1)
O(1a)-Ni(1)-N(1)
O(1)-Ni(1)-N(1a)
O(1a)-Ni(1)-N(1a)
N(1)-Ni(1)-N(1a)
O(1)-Ni(1)-S(1)
O(1a)-Ni(1)-S(1)
N(1)-Ni(1)-S(1)
N(1a)-Ni(1)-S(1)
O(1)-Ni(1)-S(1a)
O(1a)-Ni(1)-S(1a)
N(1)-Ni(1)-S(1a)
N(1a)-Ni(1)-S(1a)
S(1)-Ni(1)-S(1a)
95.25(18)
93.20(12)
91.19(12)
91.19(12)
93.20(12)
173.5(12)
176.15(9)
88.14(9)
S(1)-C(16)
O(1)-C(13)
N(1)-C(7)
84.89(10)
90.44(10)
88.15(9)
N(1)-C(6)
O(2)-C(12)
C(16)-C(16a)
O(12)-C(13)
C(7)-C(8)
176.15(9)
90.44(10)
84.89(10)
88.52(6)

Table 3. Hydrogen bonds (Å and deg) for [NiL]·2H2O.
(D-H…A)
d (D-H)
d (H…A)
d (D...A)
< (DHA)
O(3)-H(3A)…O(1)#2
C(7)-H(7)…O(3)#3
0.855(19)
0.95
1.96(2)
2.55
2.807(4)
3.460(5)
171(5)
159.8

Figure 1. Methyl and methylene protons of ethyl groups in Cd(II) complex.

Figure 2. Crystal structure of [NiL]·2H2O showing 50% displacement ellipsoids.

Figure 3. Crystal packing of [NiL]·2H2O showing the hydrogen bonds (Å).

Graphical abstract