Influence of synthesis conditions on complexation of Cu (II) with O,N,O tridentate hydrazone ligand. X-ray diffraction and spectroscopic investigations

Article abstract of DOI:10.1016/j.molstruc.2017.05.140

Four novel Cu²⁺ coordination compounds with a (E)-N′-(2-hydroxybenzylidene)-2-phenylacetohydrazide (HBPAH, H₂L) have been synthesized and characterized by single crystal X-ray diffraction method, IR, UV–Vis and EPR spectroscopy. In a

Full text of DOI:10.1016/j.molstruc.2017.05.140

Accepted Manuscript
Influence of synthesis conditions on complexation of Cu (II) with O,N,O tridentate
hydrazone ligand. X-ray diffraction and spectroscopic investigations
H.H. Repich, S.I. Orysyk, V.V. Orysyk, Yu.L. Zborovskii, A.K. Melnyk, V.V.
Trachevskyi, V.I. Pekhnyo, M.V. Vovk
PII:
S0022-2860(17)30760-3
10.1016/j.molstruc.2017.05.140
MOLSTR 23881
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 24 April 2017
Revised Date: 30 May 2017
Accepted Date: 30 May 2017
Please cite this article as: H.H. Repich, S.I. Orysyk, V.V. Orysyk, Y.L. Zborovskii, A.K. Melnyk, V.V.
Trachevskyi, V.I. Pekhnyo, M.V. Vovk, Influence of synthesis conditions on complexation of Cu (II)
with O,N,O tridentate hydrazone ligand. X-ray diffraction and spectroscopic investigations, Journal of
Molecular Structure (2017), doi: 10.1016/j.molstruc.2017.05.140.
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.

ACCEPTED MANUSCRIPT

1
ACCEPTED MANUSCRIPT
Influence of synthesis conditions on complexation of Cu (II) with O,N,O
tridentate hydrazone ligand. X-ray diffraction and spectroscopic investigations.
H.H. Repich a*, S.I. Orysyk a, V.V. Orysyk b, Yu.L. Zborovskii b, A.K. Melnyk c,
V.V. Trachevskyi d, V.I. Pekhnyo a, M.V. Vovk b.
a Vernadsky Institute of General and Inorganic Chemistry, National Academy of
Sciences of Ukraine, Palladin Ave. 32/34, 03680 Kyiv, Ukraine
b Institute of Organic Chemistry, National Academy of Sciences of Ukraine,
Murmaska Str. 5, 02660 Kyiv, Ukraine
c Institute for sorption and problems of endoecology, National Academy of
Sciences of Ukraine, Generala Naumova Str. 13, 03164 Kyiv, Ukraine
d Technical centre, National Academy of Sciences of Ukraine, Pokrovska Str. 13,
04070 Kyiv, Ukraine
Abstract
Four novel Cu2+ coordination compounds with a (E)-N'-(2-hydroxybenzylidene)-
2-phenylacetohydrazide (HBPAH, H2L) have been synthesized and characterized by
single crystal X-ray diffraction method, IR, UV-Vis and EPR spectroscopy.
In all obtained compounds the ligand is coordinated in typical O,N,O-tridentate
chelate manner. It has been shown that synthesis conditions have a great influence on
a structure of resulting complex compounds. Depending on starting Cu2+ compounds,
concentration of reagents, pH and the presence of secondary ligands the HBPAH
coordinates as a neutral molecule, mono- or dianion with formation of four different
complexes: [Cu(HL)(H2L)]NO3 (I), [Cu(HL)Cl] (II), [Cu2(HL)2Cl2] (III) and
[Cu2(L)2Py2] (IV). Complex I is interesting by the presence of two differently
coordinated ligand molecules. Mononuclear complex compound II and its dimeric
analogue III were obtained from the same reagents: CuCl2 and HBPAH but in
different reaction conditions. In dimeric complex IV the HBPAH molecules are
coordinated as dianions in imidol tautomeric form, the pyridine molecules act as
secondary ligands complementing the coordination polyhedra of Cu2+ ions.
Study of UV-Vis and EPR spectra of complex compounds I-IV in solutions
showed that all the complexes undergo partial solvolysis upon dissolution.
Keywords: Copper complex, synthesis, X-ray structure, hydrazone, UV-Vis, EPR
*Corresponding author. Tel.: +380937046014; fax: +380 44 4243070.
E-mail address: glebrepich@gmail.com, (H.H. Repich).

2
ACCEPTED MANUSCRIPT
1. Introduction
High interest to chemistry of hydrazones is determined by their pronounced
biological activity. Hydrazone derivatives are known to possess high spectrum of
physiological effects as well as antimicrobial activities [1-5]. However functionally
substituted hydrazones containing additional donor groups can also act as effective
chelating ligands and form complexes with useful properties: catalytic [6-8],
magnetic [9], luminescence [10-12], anticancer activity [13,14] etc.
From complexation point of view, ones of the most interesting among hydrazone
derivatives are acyl hydrazones of salicylaldehyde (AHSA) (Fig. 1). The AHSA
provide fixed tridentate chelate O,N,O coordination mode for a wide variety of metal
ions with formation of enormous diversity of coordination compounds. The AHSA
readily forms complexes with M:L 1:2 [15,16] or even 1:3 [17,18] (with lanthanides).
But the most widespread for AHSA are complexes with M:L = 1:1 in which vacant
coordination sites in metal polyhedra are occupied by additional anionic or neutral
secondary ligands or solvent molecules [6-8,10-12,15,19,20]. Formation of mixed
ligand complex compounds provides an additional way to control structural
diversities of complexes through charges and shapes of the secondary ligands.
The special feature of acyl hydrazones is their amido-imidol tautomerism (Fig.
1). AHSA can coordinate as mono- (a) or dianion (b) and also in molecular form [21]
(c) that provides an additional possibility to control charge of complexes depending
on synthesis pH. Moreover, anionic form of AHSA provides high negative charge on
deprotonated oxygen atoms that often leads to polynucleation via ꢀ2 or ꢀ3 bridging
phenoxyl oxygen with formation of di- [10-12,15,19] or even tetrameric [22,23]
coordination compounds.
Fig. 1. Acyl hydrazones of salicylaldehyde (AHSA). Their tautomeric forms and
main types of coordination.

3
ACCEPTED MANUSCRIPT
Position of Cu2+ ion in Irving-Williams series shows the highest complexation
ability among 3d metals [24]. This fact along with a wide range of Cu2+ polyhedra
shapes from tetragonal bipyramidal to square-planar due to high Jahn–Teller effect
[25] for d9 configuration makes Cu2+ a very flexible object in coordination chemistry.
And from synthetic point of view it is very interesting to study factors which lead to
formation of different shapes of coordination polyhedra with AHSA.
So, in present work we investigated an influence of synthesis conditions on a
structure of Cu2+ complexes with AHSA derivative. Depending on starting Cu2+ salts,
solvents, concentration of reagents, and presence of secondary ligands four different
Cu2+ complexes with (E)-N'-(2-hydroxybenzylidene)-2-phenylacetohydrazide were
synthesized.
2. Experimental
2.1. Materials and measurements
Initial reagents Cu(NO3)2·3H2O, CuCl2·2H2O and solvents C2H5OH, pyridine,
chloroform and diethyl ether used in this work were of analytical grade and used as
purchased without further purification.
IR spectra were recorded on a Specord M80 in the range 4000–200 cm-1 in KBr
pellets. UV-Vis spectra of ethanol solutions of the ligand and its complexes (10-4 M)
were recorded on a Specord M40 spectrophotometer in a range of 40000–11000 cm-1
(250–900 nm) using a 1 mm quartz cell, d-d transition bands of the complex
compounds were recorded in higher concentrations (~0.05 M) using a 1 cm quartz
cell. Solid state reflectance spectra of the complexes were measured on a Specord
M40 in a range of 30000–11000 cm-1 (333–900 nm). Elemental analyses for carbon,
hydrogen, nitrogen were performed by Carlo Erba Elemental Analyzer (Model 1106).
The chlorine content was measured by Shoniger method.
Both solid state and frozen solution EPR spectra of the complexes were recorded
using X-band spectrometer Elexsys E580 (Bruker, Germany). Samples of Mn2+/MgO
and 2,2-diphenyl-l-picrylhydrazyl were used for the spectrometer calibration.
2.2 Preparation of HBPAH and complexes I-IV
Starting ligand N'-(2-hydroxybenzylidene)-2-phenylacetohydrazide (HBPAH)
was prepared by reaction of phenylacetic hydrazide with salicylaldehyde in boiling
ethanol according to known procedure [26]. The phenylacetic hydrazide was prepared

4
ACCEPTED MANUSCRIPT
by hydrazinolysis of ethyl phenylacetate. Synthesized organic molecules were
identified using 1H NMR spectroscopy.
2.2.1 Preparation of [Cu(H2L)(HL)]NO3·1.25H2O·0.25C2H5OH (I)
60.5 mg of Cu(NO3)2 ·3H2O (0.25 mmol) were dissolved in 15 ml of C2H5OH.
To the resulting solution was added dropwise warm H2L solution (127 mg, 0.5 mmol
in 15 ml of C2H5OH). The obtained green solution was stirred during 10 minutes and
left for crystallization in the dark by slow solvent evaporation. After few days fine
light-green prism-shaped crystals formed which were filtered off and washed with
cold C2H5OH, chloroform and diethyl ether.
Yield 103 mg (65%). Calculated for C30.5H31CuN5O8.5, %: C, 54.91; H, 4.68; N,
10.50. Found, %: C, 54.7; H, 4.36; N, 10.79.
2.2.2 Preparation of complex [Cu(HL)Cl]·H2O (II)
42.7 mg of CuCl2 ·2H2O (0.25 mmol) were dissolved in 15 ml of water-ethanol
1:4 mixture. To the resulting solution was added dropwise H2L solution (63.5 mg,
0.25 mmol in 15 ml of H2O-C2H5OH 1:4). The obtained green solution was stirred
during 10 minutes and then left for crystallization in the dark by slow solvent
evaporation. After few days fine dark green crystals formed which were filtered off
and washed with cold H2O-C2H5OH mixture and diethyl ether.
Yield 63.4 mg (72%). Calculated for C15H15ClCuN2O3, %: C, 48.65; H, 4.08; Cl,
9.57; N, 7.57. Found, %: C, 48.5; H, 3.95; Cl, 8.9; N, 7.45.
2.2.3 Preparation of complex [Cu2(HL)2Cl2](III)
85.5 mg of CuCl2 ·2H2O (0.5 mmol) were dissolved in 5 ml of warm C2H5OH.
To the resulting warm solution was added dropwise hot H2L solution (127 mg, 0.5
mmol in 10 ml of C2H5OH). Small brown needle-like crystals immediately began to
form in the obtained brown solution. The solution was left for crystallization for 1
hour and after that the crystals were filtered off and washed with cold C2H5OH and
diethyl ether. Suitable single crystals for the structure determination were obtained by
slow evaporation of the mother liquor.
Yield 142 mg (81%). Calculated for C30H26Cl2Cu2N4O4, %: C, 51.14; H, 3.72;
Cl, 10.06; N, 7.95. Found, %: C, 51.35; H, 3.95; Cl, 9.86; N, 8.05.
2.2.4 Preparation of [Cu2L2Py2]·H2O (IV)

5
ACCEPTED MANUSCRIPT
60.5 mg of Cu(NO3)2 ·3H2O (0.25 mmol) were dissolved in 10 ml of C2H5OH
and then 0.5 ml of pyridine was added. To the obtained mixture was added dropwise
H2L solution (63.5 mg, 0.25 mmol in 10 ml of C2H5OH). The resulting dark-green
solution was carefully evaporated on a steam bath until the volume was reduced to 10
ml. Then 20 ml of CHCl3 and 20 ml of distilled water was added. The complex
transferred into the chloroform layer which became dark-green. Then chloroform
layer was separated from the water using a separating funnel and washed with two
portions (20 ml) of water. Then the chloroform solution was dried with 2 g of
anhydrous Na2SO4, filtered off into a dry flask, added with 10 ml of cyclohexane and
left for crystallization by slow solvent evaporation.
After few days fine thin dark green crystals formed and after complete
evaporation of solvent. Yield 93 mg (94%). Calculated for C40H36Cu2N6O5, %: C,
58.17; H, 4.64; N, 10.18. Found, %: C, 57.9; H, 4.52; N, 10.34.
2.3 Single crystal X-ray diffraction
Crystal structures of complexes I–IV were determined by single crystal X-ray
diffraction. The measurements were performed on Bruker SMART APEX2
diffractometer (Mo Kα radiation, graphite monochromator, λ = 0.71073 Å). The data
were collected using ω- and φ-scans and integrated with SAINT program [27]. The
obtained intensities were corrected for Lorentz, polarization and absorption using
multi-scan technique in SADABS program [28]. All structures were solved by direct
methods and refined by full matrix least-square method against F2 using SHELXTL
program package [29]. Positions of hydrogen atoms were located from difference
Fourier maps and refined using a riding model with Uiso(H) = nUeq of carrier
nonhydrogen atom (n = 1.5 for methyl groups and water molecule and 1.2 for other H
atoms). The main crystallographic parameters and detailed experimental data are
given in Table 1.
In structure of complex I disorders of one nitrate ion, one water molecule and
the benzyl moiety of complex cation (d) were resolved by splitting of all atoms over
two positions with 50% occupancy of each one. All attempts to locate protons on
disordered water molecules were unsuccessful.
Table 1. Summary of crystallographic data for complexes I-IV
Compound
Complex I
Complex II
Complex III
Complex IV
Empirical formula C122H124Cu4N20 O34
C30H30Cl2Cu2N4O C30H26Cl2Cu2N4 O4 C40H35Cu2N6O5
6
Formula weight
Crystal system,
2666.55
Triclinic
740.56
Monoclinic
704.53
806.82
Monoclinic P2(1)/c Monoclinic

6
ACCEPTED MANUSCRIPT
P2(1)/c
space group
Unit cell
dimensions (Ǻ)
P 1
C 2/c
a = 13.3692(4)
b = 14.0464(4)
c = 17.5753(5)
α = 70.904(2)
β = 76.542(2)
γ = 83.757(2)
3031.28(16)
1, 1.461
a = 8.4107(3)
b = 15.0354(5)
c = 24.4909(8)
β = 94.696(2)
a = 11.3687(5)
b = 13.2373(5)
c = 10.0177(5)
β = 99.034(2)
a = 25.3080(8)
b = 7.3162(2)
c = 19.0803(5)
β = 92.376(3)
Volume (Ǻ3)
Z, calculated
density (g/cm3)
ꢀ (mm-1)
3086.68(18)
4, 1.594
1488.87(11)
2, 1.572
3529.84(17)
4, 1.518
0.782
1.601
1.650
1.260
F(000)
1382
1512
716
1660
Crystal size (mm)
θ range for data
collection (˚ )
Limiting indices
0.641×0.094×0.034
1.535 to 28.708
0.42×0.34×0.14
1.67 to 26.00
0.62×0.17×0.06
2.38 to 25.99
0.84×0.11×0.05
1.61 to 26.00
-17≤ h ≤ 17,
-18≤ k ≤ 17,
-23≤ l ≤ 18
-10≤ h ≤ 10,
-18≤ k ≤ 18,
-29≤ l ≤ 30
43867 / 6075
-14≤ h ≤ 13,
-15≤ k ≤ 16,
-12≤ l ≤ 12
19565 / 2923
-31≤ h ≤ 31,
-8≤ k ≤ 9,
-23≤ l ≤ 23
Reflections
collected/unique
Completeness to
θmax (%)
48526 / 22845
24722 / 3451
0.997
0.999
0.999
0.999
Max/min
0.974 / 0.634
22845 / 45 / 1629
0.8069 / 0.5522
6075 / 4 / 501
1.078
0.9017 / 0.4296
2923 / 190 / 0
1.020
0.9374 / 0.4160
3451 / 240 / 0
1.045
transmission
Data/restrains/
parameters
Goodnes-of-fit on 1.071
F2
Final R indicies
[I>2σ(I)]
R indicies (all
data)
R1 = 0.0447,
R1 = 0.0251,
wR2 = 0.0653
R1 = 0.0333,
wR2 = 0.0680
0.370 / -0.301
R1 = 0.0418, wR2 = R1 = 0.0421,
0.0755 wR2 = 0.0832
R1 = 0.0745, wR2 = R1 = 0.0884,
wR2 = 0.1012
R1 = 0.0665,
wR2 = 0.1086
0.791 / -0.733
0.0827
wR2 = 0.0653
Largest diff. peak
0.263 / -0.521
0.541 / -0.680
and hole (e Ǻ-3)
3. Results and discussion
The complex compounds were synthesized according to the scheme (Fig. 2). It
should be noted that tetragonal bipyramidal Cu2+ complexes are not very common for
AHSA, because high Jahn–Teller effect for d9 electronic configuration favors
reducing of symmetry of Cu2+ coordination polyhedra. Indeed, search in Cambridge
Structural Database [30] showed only one tetragonal bipyramidal Cu2+ complex with
O,N,O coordinated AHSA derivative [31] among total 221 Cu2+ complexes with
AHSA. In general for Cu2+ with AHSA more common are M:L = 1:1 complexes with
tetragonal pyramidal, trigonal bipyramidal or square-planar polyhedra, in which
vacant coordination sites of Cu2+ polyhedra are occupied by various secondary
ligands.

7
ACCEPTED MANUSCRIPT
Fig. 2. Synthesis of complexes I–IV.
However, complexation of Cu(NO3)2 with HBPAH in 1:2 ratio leads to
formation of tetragonal bipyramidal complex I bearing two O,N,O coordinated
-
HBPAH molecules. It is because hard NO3 ion is a poor secondary ligand for Cu2+
and the HBPAH molecule does not contain any additional donor atoms which can
contribute fourth vacant coordination site in square-planar Cu2+ polyhedron.
This situation changes dramatically if any particles that can act as secondary
ligands are present in reaction mixture. Reaction of HBPAH with CuCl2 does not
result in any tetragonal bipyramidal bisligand complexes even if a huge excess of
HBPAH was used for synthesis.
Complexation of HBPAH with CuCl2 results in formation of two different
coordination compounds II and III (Fig. 2). In both complexes chloride ions occupy
the fourth vacant equatorial positions of Cu2+ polyhedra. Yield of the complexes
strongly depends on concentration of reagents and solvent used. Reaction in water-
ethanol 1:4 solution at low concentration (8 mM) leads to formation of square-planar
coordination compound II with M:L = 1:1. The same reaction but in 96% ethanol at
high concentration of reagents (25 mM) leads to dimerization of complex II via ꢀ2

8
ACCEPTED MANUSCRIPT
phenyl oxygens and formation of binuclear complex III. It should be noted that low
concentration of reagents (8 mM) but in 96% ethanol leads to formation of mixture of
II and III. Therefore, higher reagent concentrations favor formation of dimeric
complex III and lower reagent concentrations favor formation of monomeric
complex II. Also yield of dimeric or monomeric species can be influenced by
solvent. The 96% ethanol favors formation of binuclear complex III and water-
ethanol 1:4 mixture favors formation of mononuclear complex II. Such influence of
the solvent may be explained by better solvation of Cu2+ ions by water molecules
then by molecules of ethanol. Addition of water hinders dimerization and allows us to
obtain square-planar complexes in water-ethanol mixture. In support of this theory it
was noted that long term storage of complex II under 96% ethanol leads to its
transformation into complex III.
The complex IV was synthesized from Cu(NO3)2 in ethanol-pyridine mixture.
The pyridine increases pH of solution to ~ 9 that leads to imidol tautomeric form of
HBPAH and its coordination as dianion. Also pyridine acts as a neutral secondary
ligand supplementing the fourth equatorial coordination site of Cu2+ polyhedra. The
complex IV is dimeric. Dimerization occurs via ꢀ2 bridged phenyl oxygens similarly
to complex III.
3.1 X-ray structures of complexes I-IV
3.1.1 Crystal structure of complex I
Complex compound I crystallizes in noncentrosymmetric spaсe group P1 with
four independent complex molecules per unit cell. All four molecules have the same
structure, numbering scheme and labeled with a, b, c, d indexes respectively (Fig. 3a,
only one complex molecule with “a” index is shown). Atom labels mentioned below
without indexes refer to all four complex molecules. Selected bonds and angles are
tabulated in Table 2.
The polyhedron of Cu2+ is formed by O1/N1/O2 and O3/N3/O4 atoms of two
tridentate chelate coordinated HBPAH molecules/ One of the HBPAH molecules is
coordinated in an equatorial plane and the another one is in axial plane. Coordination
polyhedron of Cu2+ ions have elongated tetragonal-bipyramidal geometry with
tetragonality factor T = 0.88 (where T is average in plane Cu-L distance value
divided by average Cu-L out of plane one [32,33]). To obtain the most reliable T
value only the Cu-O(carbonyl) distances were considered. The adjacent angles
around Cu atoms are in range of 81.5−109.6˚.

9
ACCEPTED MANUSCRIPT
The main feature of this complex are two differently coordinated ligand
molecules. The “axial” ligand is coordinated in molecular form and the “equatorial”
ligand is coordinated as monodeprotonated phenolic anion, that leads to cationic
character of complex I. Such different coordination is also reflected in phenolic O(1)-
C(1), O(3)-C(16) bond lengths. The O(1)-C(1) bond in deprotonated molecule is
shorter than O(3)-C(16) bond in nondeprotonated one (Table 2). The N(2)-C(8),
N(4)-C(23), O(2)-C(8), O(4)-C(23) bond lengths values show that both ligand
molecules are coordinated in amide tautomeric form [34].
In crystal phase complex molecules form macrocyclic dimmers through
intermolecular charge enhanced O-H...O- hydrogen bonds between deprotonated and
nondeprotonated phenoxyl moieties of ligands (Fig. 3b). Outer coordination sphere of
complex I contains 4 nitrate ions, 4 water molecules and one molecule of C2H5OH
per 4 complex cations. In crystal structure molecular dimmers are bonded by
branched network of N-H…O, O-H…O hydrogen bonds.
Fig. 3. The molecular structure of complex I. Only one from the four
independent molecules is shown for clarity. Thermal ellipsoids are shown at 30%
probability level (a). The dimerization of the complex cations in crystal structure via
hydrogen bonding (b).
Table 2. Selected bonds and angles values of complex I. Only values for the
molecule “a” are shown.
Bond
distance, Å Angle
value, ˚
N(1A)-Cu(1A)-O(1A) 91.06(14)
N(1A)-Cu(1A)-O(2A) 81.59(15)
O(1A)-Cu(1A)-O(2A) 170.00(14)
N(1A)-Cu(1A)-N(3A) 168.62(16)
O(1A)-Cu(1A)-N(3A) 96.11(14)
Cu(1A)-O(1A) 1.946(3)
Cu(1A)-O(2A) 1.988(3)
Cu(1A)-O(4A) 2.261(3)
Cu(1A)-O(3A) 2.279(3)
Cu(1A)-N(1A) 1.927(4)

10
ACCEPTED MANUSCRIPT
Cu(1A)-N(3A) 2.048(4)
O(1A)-C(1A) 1.335(5)
O(3A)-C(16A) 1.344(5)
O(2A)-C(8A) 1.244(6)
O(4A)-C(23A) 1.227(6)
N(2A)-C(8A) 1.334(6)
N(3A)-C(22A) 1.292(5)
N(1A)-C(7A) 1.290(5)
N(4A)-C(23A) 1.349(5)
O(2A)-Cu(1A)-N(3A) 92.23(14)
N(1A)-Cu(1A)-O(4A) 95.39(14)
O(1A)-Cu(1A)-O(4A) 90.19(14)
O(2A)-Cu(1A)-O(4A) 97.21(13)
N(3A)-Cu(1A)-O(4A) 75.82(14)
N(1A)-Cu(1A)-O(3A) 109.59(14)
O(1A)-Cu(1A)-O(3A) 89.57(13)
O(2A)-Cu(1A)-O(3A) 86.54(13)
N(3A)-Cu(1A)-O(3A) 79.37(14)
O(4A)-Cu(1A)-O(3A) 155.02(12)
3.1.2 X-ray crystal structure of complex II
The asymmetric unit of the complex compound II includes two [Cu(HL)Cl]
complex molecules of and two water molecules (Fig. 4a). Selected bond lengths and
angle values are shown in Table 3. Both complex molecules have the same molecular
structure, numbering scheme but labeled with a, b indexes. Atom labels mentioned
below without the indexes refer to both molecules simultaneously.
In both complex molecules the central Cu2+ ions form a slightly distorted square-
planar coordination polyhedra. The polyhedra are formed by O1/N1/O2 atoms of
tridentate chelate coordinated HBPAH molecules, the fourth vacant positions of
polyhedra are occupied by Cl(1) chloride ions. The mean least square deviation from
plane for Cu(1)/O(1)/O(2)/N(1)/Cl(1) polyhedron is 0.0538 Ǻ and 0.0534 Ǻ for “a”
and “b” molecules respectively. The polyhedra are coplanar to each other with
dihedral angle between the planes of 6.3˚. Coordinated Cl(1a) ion is located right
under Cu(1b) atom of the second independent molecule with Cu(1a)/Cl(1a)/Cu(1b)
angle value of 89.73°. But the Cu(1b)…Cl(1a) distance value of 3.193 Ǻ shows no
coordination interactions between these atoms.
The adjacent angles around the Cu atoms are in a range of 80.12(6)–95.33(4)˚.
Lengths of the O(1)-C(1) bonds together with absence of hydrogens on O(1) atoms
show that in both complexes ligands are coordinated as phenolate ions. Lengths of
the N(2)-C(8), O(2)-C(8) bonds together with the presence of protons on N(2)
nitrogens clearly demonstrate that ligands in both complexes coordinated as amido
tautomers [34].
In crystal phase molecules of complex II form stacks along [100]
crystallographic direction due to hydrogen bonds and stacking interactions between
planar fragments of ligands. Complexes of neighboring stacks are bonded by

11
ACCEPTED MANUSCRIPT
hydrogen bonds and weak π–π stacking interactions between benzyl fragments of
ligand molecules (Fig. 4b).
Fig. 4. The molecular structure of complex II, thermal ellipsoids are shown at
50% probability level (a). Packing diagram of complex II, projection along [100]
crystallographic axis (b).
Table 3. Selected bonds and angles values of complex II.
Bond
distance, Å Angle
value, ˚
Cu(1A)-O(1A) 1.9012(13) O(1A)-Cu(1A)-N(1A) 91.95(6)
Cu(1A)-N(1A) 1.9272(15) O(1A)-Cu(1A)-O(2A) 172.65(5)
Cu(1A)-O(2A) 1.9884(13) N(1A)-Cu(1A)-O(2A) 80.95(6)
Cu(1A)-Cl(1A) 2.2094(5) O(1A)-Cu(1A)-Cl(1A) 93.03(4)
O(1A)-C(1A) 1.323(2)
O(2A)-C(8A) 1.254(2)
N(2A)-C(8A) 1.324(2)
N(1A)-C(7A) 1.286(2)
N(1A)-Cu(1A)-Cl(1A) 170.68(5)
O(2A)-Cu(1A)-Cl(1A) 93.75(4)
Cu(1B)-O(1B) 1.8960(13) O(1B)-Cu(1B)-N(1B) 92.80(6)
Cu(1B)-N(1B) 1.9405(15) O(1B)-Cu(1B)-O(2B) 172.91(5)
Cu(1B)-O(2B) 1.9949(13) N(1B)-Cu(1B)-O(2B) 80.12(6)
Cu(1B)-Cl(1B) 2.2236(5) O(1B)-Cu(1B)-Cl(1B) 95.33(4)
O(1B)-C(1B)
O(2B)-C(8B)
N(2B)-C(8B)
N(1B)-C(7B)
1.319(2)
1.262(2)
1.322(2)
1.294(2)
N(1B)-Cu(1B)-Cl(1B) 169.35(5)
O(2B)-Cu(1B)-Cl(1B) 91.65(4)
3.1.3 X-ray crystal structure of complex III

12
ACCEPTED MANUSCRIPT
Molecule of complex III is a centrosymmetric dimer (Fig. 5a). Selected bonds
and angles values are shown in Table 4. The coordination polyhedron of Cu2+ can be
described as a strongly distorted tetragonal pyramid with a degree of trigonality
parameter τ = 0.475, where τ = (β – α)/60º and β and α are the two largest angles (β >
α) [35]. According to the τ value the polyhedron shape lies almost on the edge
between tetragonal pyramid and tetragonal bipyramid. Equatorial positions of the
tetragonal pyramid are occupied by O1/N1/O2 of tridentate chelate coordinated
HBPAH molecule and Cl(1) chloride anion. Axial position of tetragonal pyramid is
occupied by ꢀ2–O(1) oxygen of symmetrically equivalent ligand molecule which acts
as a bridge forming the dimmer. The axial Cu(1)-O(1a) bond is much longer than
equatorial Cu(1)-O(1) one (tetragonality factor T = 0.871 [32,33]) due to Jahn–Teller
effect for d9 electronic configuration of Cu2+ (Table 4).The Cu(1)-O(1) bond is a little
shorter than the Cu(1)-O(2) because of anionic character of O(1) atom. Lengths of the
O(1)-C(1) bonds together with absence of hydrogen on O(1) atom and lengths of the
N(2)-C(8), O(2)-C(8) bonds together with proton on N(2) nitrogen atom clearly
demonstrate that the ligand molecules are coordinated as phenolate ions in amido
tautomeric form [34].
Analysis of the crystal structure of complex III reveals layered structure along
the (100) crystallographic plane. Complexes in the layers are bonded by network of
hydrogen bonds. Neighboring layers are bonded by weak π–π interactions between
benzyl fragments of ligand molecules (Fig. 5b).
Fig. 5. The molecular structure of complex III, thermal ellipsoids are shown at
30% probability level (a). The packing diagram of complex III, view along [100]
crystallographic axis (b).
Table 4. Selected bonds and angles values for complex III.
Bond
distance, Å Angle
value, ˚
Cu(1)-O(1)
1.9169(19) O(1)-Cu(1)-N(1)
90.05(9)

13
ACCEPTED MANUSCRIPT
Cu(1)-N(1)
Cu(1)-O(2)
1.944(2)
2.016(2)
O(1)-Cu(1)-O(2)
N(1)-Cu(1)-O(2)
166.24(9)
80.36(9)
Cu(1)-O(1)#1 2.200(2)
O(1)-Cu(1)-O(1)#1 82.17(8)
Cu(1)-Cl(1)
O(1)-C(1)
O(2)-C(8)
N(2)-C(8)
N(1)-C(7)
2.2933(9) N(1)-Cu(1)-O(1)#1 119.62(9)
1.332(3)
1.250(3)
1.324(4)
1.289(4)
O(2)-Cu(1)-O(1)#1 93.95(8)
O(1)-Cu(1)-Cl(1)
N(1)-Cu(1)-Cl(1)
O(2)-Cu(1)-Cl(1)
96.26(6)
137.71(8)
97.47(7)
O(1)#1-Cu(1)-Cl(1) 102.67(6)
#1 -x+1,-y+1,-z+1
3.1.4 X-ray crystal structure of complex IV
Molecule of complex IV is also a centrosymmetric dimer (Fig. 6a). Selected
bonds and angles are shown in Table 5. Coordination environment of Cu2+ ion forms
a slightly distorted tetragonal pyramidal polyhedron with parameter τ = 0,074.
Equatorial positions of the tetragonal pyramid are occupied by O1/N1/O2 tridentate
chelate coordinated HBPAH ligand and N(3) nitrogen of pyridine molecule. Axial
position is occupied by ꢀ2–O(1) oxygen of symmetrically equivalent ligand
molecules which acts as a bridge forming the dimmer. The axial Cu(1)-O(1a) bond is
much longer than equatorial Cu(1)-O(1) (Table 5). The tetragonality factor T = 0.75
value indicates much stronger axial distortion than in complexes I and III.
Length of O(1)-C(1) bond and absence of proton on O(1) oxygen shows anionic
character of the phenoxyl oxygen. Unlike the complexes I-III, in complex IV the
N(2)-C(8), O(2)-C(8) bonds lengths and the absence of proton on N(2) atom clearly
indicate imidol tautomeric form of HBPAH molecules [34].
Molecules of complex IV form stacks in crystal structure along [010]
crystallographic direction due to weak interactions between benzyl fragments of
neighboring complex molecules. The stacks are bonded by hydrogen bonds along
[001] axis (Fig. 6b).

14
ACCEPTED MANUSCRIPT
Fig. 6. The molecular structure of complex IV, thermal ellipsoids are shown at
30% probability level (a). Packing diagram of complex IV, projection along [010]
crystallographic axis (b).
Table 5. Selected bonds and angles values of complex IV.
Bond
distance, Å Angle
value, ˚
Cu(1)-N(1)
Cu(1)-O(1)
Cu(1)-O(2)
Cu(1)-N(3)
1.917(2)
1.9192(18) N(1)-Cu(1)-O(2)
1.9451(19) O(1)-Cu(1)-O(2)
N(1)-Cu(1)-O(1)
92.41(8)
81.04(9)
173.43(8)
169.58(9)
93.67(9)
92.73(9)
1.999(2)
N(1)-Cu(1)-N(3)
Cu(1)-O(1)#1 2.5580(19) O(1)-Cu(1)-N(3)
O(1)-C(1)
O(2)-C(8)
N(2)-C(8)
N(1)-C(7)
1.325(3)
1.288(3)
1.313(4)
1.283(3)
O(2)-Cu(1)-N(3)
N(1)-Cu(1)-O(1)#1 98.12(8)
O(1)-Cu(1)-O(1)#1 83.91(7)
O(2)-Cu(1)-O(1)#1 97.48(7)
N(3)-Cu(1)-O(1)#1 90.94(7)
#1 -x,-y,-z
3.2 IR spectroscopy of HBPAH and complexes I-IV
The high-frequency region of IR spectrum of free HBPAH contains a set of
characteristic absorption bands (AB) which correspond to ν(O-HPh) of phenoxyl core
(3207 cm-1) involved into formation of intramolecular hydrogen bonds and ν(N-H) of
hydrazo-group at 3181 см-1 (Fig. 7, Table 6)

15
ACCEPTED MANUSCRIPT
Fig. 7. IR-spectra of free HBPAH and complexes I-IV
Table 6. Main characteristic absorption bands of free HBPAH and complexes I-
IV.
Compound ν(OHPh) ν(NH) ν(C=O)
ν(C=N)
ν(C=N) ν (C-OPh) ν(Cu-N) ν(Cu-Cl)
azomethine imidol
+ (C-C)Ar
HBPAH
3207
3219−3165 wide
3181
1665
1617, 1602
-
-
-
-
1363
1383
1390
1380
1375
-
324
322
322
331, 321
-
-
I
II
III
IV
1600 broad
1600 broad
1595 broad
-
-
-
3182
3137
-
288
275
-
-
1608
1525
As well as in free HBPAH, in the spectrum of complex I the absorption band of
ν(O-HPh) is also present as a wide shoulder-like band at 3219−3165 cm-1 which
correspond also to ν(N-H). In contrast to free HBPAH and complex I, IR spectra of
complexes II, III, IV do not contain any ABs of ν(O-HPh) due to deprotonation of
phenoxyl OH group upon complex formation.
Unlike free HBPAH and complexes I-III, the high-frequency region of
spectrum of complex IV do not contain any ABs of ν(О-НPh) and ν(N-H) due to
coordination of the ligand as bideprotonated imidol tautomer.
The strong absorption band at 1668–1654 cm-1 in IR spectrum of HBPAH
belongs to valence vibrations of (C=O) group. The doublet band with maxima at
1617, 1602 cm-1 corresponds to valence vibrations of azomethine moiety (C=N) and
skeletal (C-C) vibrations of aromatic rings. The AB at 1363 belongs to valence
vibrations of phenoxyl (C–О).
In spectra of complexes I-III ABs of ν(С=О) are shifted to a low-frequency
region for 50–58 cm-1 that indicates elongation of (C=O) bonds because of their

16
ACCEPTED MANUSCRIPT
coordination to metal ion. That also leads to their overlapping with the ABs of
ν(C=N) and skeletal (C-C) vibrations of aromatic rings with formation of strong wide
AB at ~ 1600 cm-1.
In the IR spectra of all complexes ABs of ν(C–ОPh) of phenoxyl moiety undergo
high frequency shift for ∆ν=12-27 cm-1 that shows shortening of (C–ОPh) bond due to
deprotonation of (OHPh) group with formation of phenoxyl anion.
In contrast to the complexes I-III, in the IR spectra of complex IV the AB of
ν(С=О) is absent while a new AB at 1217 cm-1 appears which may correspond to
valence vibrations of single bond (C–О) of imidol tautomeric form of coordinated
hydrazone. In addition, spectrum of complex IV have a quite intensive band at 1524
cm-1 which indicates the newly formed (N=C) bond of imidol tautomeric form of the
ligand. At the same time, a wide and intensive AB appears in a range of 1615–1600
cm-1 in the spectrum of complex IV which combines valence vibrations of (C=N) and
skeletal vibrations of aromatic rings [36-38].
Low-frequency area of complexes I-IV contains ABs which correspond to ν(Cu-
N) and ν(Cu-Cl) bonds (Table 7). The ν(Cu-O) vibrations can not be identified due to
their overlapping with δ(CH)Ar of aromatic rings.
3.3 UV-Vis spectroscopy of HBPAH and complexes I-IV
Electronic spectra of diffuse reflection of complexes I-IV recorded in a range of
30000-11000 cm-1 have forms of broad, poorly separated absorption bands with
maxima corresponding to dz2→dx2-y2 (the lowest frequency band), dxy→dx2-y2, dxz,dyz
→dx2-y2 transitions in Cu2+ ion (14100–18500 cm-1) and ligand-to-metal O→Cu and
Cl→Cu charge-transfer bands (LMCTBs) in a range of 24500-27100 cm-1 [32,33].
(Table 7, Fig. 1S).
Table 7. UV-Vis spectra data for HBPAH and complexes I-IV
Complex d–d transitions (solid state)
LMCTBs
(solid state)
25250–27100
dz2→dx2-y2
(solution)
14250
LMCTBs
(solution)
26340
I
14100 (dz2→dx2-y2
20600 (dxy→dx2-y2, dxz,dyz →dx2-y2
14600 (dz2→dx2-y2
)
)
II
)
24600
24500
14150
14150
25900
25900
III
13350 (dz2→dx2-y2),
18500 (dxy→dx2-y2, dxz,dyz →dx2-y2
)
IV
16750 (dz2→dx2-y2
)
26400
16550
26725

17
ACCEPTED MANUSCRIPT
UV-Vis spectra of ethanol solutions of complexes I-IV can be classified into
three regions (Fig. 8). The high-frequency region 27000-50000 cm-1 includes group
of intensive absorption bands corresponding to π→π*, n→π* electronic transitions in
ligand molecule. The second group corresponds to ligand-to-metal charge-transfer
bands (LMCTBs) in a range of 20000-27000 cm-1. And the third region of 11000-
20000 cm-1 contains ABs corresponding to dz2→dx2-y2 transitions in Cu2+ ion which
were registered at higher 0.05M concentrations of complex compounds (Table 7, Fig.
8).
It should be noted that UV-Vis spectra of complexes II and III in solution are
absolutely identical although in solid state complex II is mononuclear and complex
III is binuclear. This fact clearly indicates that in solution both complexes II and III
have identical structure with the same coordination environment of Cu2+ due to
dissociation of binuclear complex III in solution.
In general the high-frequency regions of free HBPAH and complexes I-III
spectra are very similar. The main difference is hypochromic shift of AB at 30800
cm-1 (HBPAH) to 33300 cm-1 (complexes II and III). In complex I the ligands are
coordinated in the same tautomeric form and in the same O,N,O manner as in the
complex II and III. Consequently their spectra should be very similar. But in fact the
UV-Vis spectrum of complex I looks like a superposition of free HBPAH and
complex II spectra (dotted line). This fact may evidence dissociation of complex I in
ethanol solution with release of one ligand molecule. The fact of dissociation of
complex I in ethanol solution will be confirmed by EPR spectroscopy (Section 3.4).
The spectrum of complex IV significantly differs from spectra of complexes I-
III and free ligand due to coordination of HBPAH in imidiol tautomeric form and
formation of new (–C=N−C=N−) conjugated bond system.
Also the spectra of I-IV contain expected ligand-to-metal charge-transfer bands
(LMCTBs) and in solutions with concentrations of the complexes of ~0.05 M the
bands of metal d-d transitions are observed (Fig. 8). Wavelength values of the d-d
transition bands in solution differ from d-d bands of solid complexes that indicates
changing of coordination environment of Cu2+ ions due to additional coordination of
solvent or substitution of ligands by solvent molecules (Table 7).

18
ACCEPTED MANUSCRIPT
Fig. 8. UV-Vis spectra of HBPAH and complexes I-IV in a range of 40000-
20000 cm-1, the dotted curve shows a sum of complex II + HBPAH spectra (a). The
d-d transition bands at 0.05M concentration of complexes I-IV (b).
3.4 EPR spectroscopy of complexes I-IV
To clarify results of the UV-Vis spectroscopy, all complexes were studied by
EPR spectroscopy in solid state and in solutions. Solid state EPR spectra of
complexes I-IV are shown in Fig. 9. As usual for Cu(II) polycrystalline samples, the
spectral lines are rather broad and only the g values can be extracted (Table 8). The
solid-state spectrum of complex II has well-defined axial symmetry with gII = 2.23,
g⊥ = 2.054 (giso=2.116). The EPR spectrum of complex I also shows axial anisotropy
but it is significantly broadened in comparison with complex II due to electron spin
exchange interactions between Cu (II) centers in macrocyclic dimers [39]. In the
spectrum of compound I the gll component is not well resolved and the spectrum has
a shape of asymmetric band with gll > g⊥=2.054 and isotropic giso value of 2.105. The
g-tensor parameter values for complexes I and II with gll > g⊥ > 2.0023 indicate that
the copper sites have dx2-y2 ground state which is characteristic for square-planar,
square-pyramidal or tetragonal-bipyramidal geometry.

19
ACCEPTED MANUSCRIPT
In contrast to complexes I and II, the solid state EPR spectra of binuclear
complexes III and IV represent very broad isotropic lines (geff = 2.127, ꢁH = 650 G
for complex III and geff = 2.097, ꢁH = 135 G for complex IV), such parameters
indicate significant exchange interactions between metal centers in binuclear
complexes and do not allow to determine anisotropic parameters of spectra.
The solid state EPR spectra confirm that complexes I, II, IV do not contain
another paramagnetic impurities. Only complex III contains a trace amount of
complex II. This is confirmed by presence of a little sharp additional signal of
complex II in the broad signal of complex III (Fig. 9).
Fig. 9. Solid state EPR spectra of complexes I-IV.
Table 8. Main parameters of EPR spectra of complexes I-IV
Complex
g-factor (solid state)
С, M
g-factor, solution (form 1) / (form 2)
g1 g2 g3
2.116 6.2 · 10-3 2.285 / 2.225 2.065 / 2.065 2.027 / 2.039
1.55 · 10-3
2.27 / - 2.065 / - 2.024 / -
All, G
g ll
g ⊥
giso*
I
2.24
(approx.)
2.23
2.054
165
165
165
165
165
165
175
II
2.043
2.105 6.2 · 10-3 2.285 / 2.225 2.065 / 2.065 2.027 / 2.039
1.55 · 10-3 2.285 / 2.225 2.065 / 2.065 2.027 / 2.039
6.2 · 10-3 2.285 / 2.225 2.065 / 2.065 2.027 / 2.039
1.55 · 10-3 2.285 / 2.225 2.065 / 2.065 2.027 / 2.039
III
geff =2.127, dH≈650 G
IV
geff =2.097, dH≈135 G
6.2 · 10-3
2.24
2.055
2.008
* giso=(gII+2g┴)/3
The complexes I–IV were also studied by EPR spectroscopy in frozen solutions
at 77 K (Fig. 10, Fig. S2, Table 8). The complexes I–III were dissolved in ethanol
with formation of clear green solutions. In contrast to this, complex IV slowly
undergo solvolysis in ethanol that leads to formation of insoluble particles in solution

20
ACCEPTED MANUSCRIPT
overtime probably due to elimination of pyridine molecules from coordination
environment. Thus, complex IV was studied in chloroform-pyridine (9:1) solution
because presence of pyridine suppresses solvolysis. The initial concentration of all
complexes was 6.2· 10-3 M.
The EPR spectra of frozen solutions of complexes I–IV show rhombic
symmetry with well-defined hyperfine structure in parallel orientation of the
spectrum due to interaction of unpaired electron with two 63,65Cu nuclei. Analysis of
frozen solutions EPR spectra of complexes I–III showed the presence of two sets of
signals with different integral intensity in the spectra (Fig. 10a, Fig. S2, Table 8).
Four times dilution of the solutions from 6.2 · 10-3 M to 1.55· 10-3M lead to change
in integral intensity ratio of the signal sets and shift of gII values in the spectra, which
confirm that two sets of signals belong to equilibrium mixture of two individual
complexes. This is quite common for Cu2+ complex compounds [40,41] and indicates
that the complexes undergo partial dissociation in solutions.
Unlike complexes I–III, the spectrum of complex IV in frozen chloroform-
pyridine solution has possess well defined g1, g2, g3 and AII parameters which belongs
to individual complex compound (Fig. 10b) because the presence of pyridine in
solution suppress dissociation of the pyridine ligand.
Fig. 10. The frozen ethanol (77 K) EPR spectrum of complex III in different
concentrations. The AII (1) and (2) from two species in solution is shown (a). The
frozen chloroform-pyridine (77 K) EPR spectrum of complex IV in concentration of
6.2 · 10-3 M (b).
It is known from literature, that typical frozen solution EPR spectra of binuclear
complexes in which two Cu2+ atoms are connected via small bridges usually have a
hyperfine structure consisting of 7 lines with AII constant two times lower than for

21
ACCEPTED MANUSCRIPT
common mononuclear Cu2+ complexes. This unusual hyperfine structure is caused by
interaction of unpaired electron with two 63,65Cu nuclei in binuclear complex
[39,42,43]. But frozen solution EPR spectra of complexes III and IV have typical 4
lines hyperfine structure. Obtained results clearly indicate that complexes III and IV
do not retain binuclear structure in solution. Dimeric complexes III and IV undergo
dissociation of [Cu-O-Cu] bonds upon dissolution with formation of monomeric
compounds. The presence of signals from two different complexes in solutions of
complexes I-III and decomposition of complex IV in pure ethanol clearly evidence
that all the complexes easily undergo stepwise dissociation in solution. This is in
good agreement with UV-Vis spectroscopy (Section 3.3).
In case of complexes II, III and IV solvolysis is followed by substitution of
weakly bonded monodentate chloride or pyridine ligands for solvent molecules. But
in case of bisligand complex I, solvolysis must undergo via elimination of one
tridentate chelate coordinated HBPAH molecule, that is also confirmed by the UV-
Vis spectroscopy (Section 3.3, Fig. 8). Such easy dissociation of tridentate chelate
coordinated ligand may be caused by nonequivalent coordination of two HBPAH
ligands. One HBPAH ligand is coordinated in equatorial position and another one is
in axial position. Due to strong Jahn-Teller effect the axial Cu-O bonds are much
longer and weaker than equatorial ones (Table 2). Axial oxygens of HBPAH can be
easily substituted for solvent molecules and in fact the axial ligand is strongly
coordinated only by one azomethine nitrogen atom and therefore can be easily
substituted too (Fig. 11).

22
ACCEPTED MANUSCRIPT
Fig. 11. Proposed scheme of solvolysis of complex I in solution.
4. Conclusions
Four novel Cu2+ coordination compounds involving the (E)-N'-(2-
hydroxybenzylidene)-2-phenylacetohydrazide (HBPAH, H2L) have been synthesized
and characterized by single crystal X-ray diffraction method, IR, UV-Vis and EPR
spectroscopy. In all obtained compounds ligand molecules are coordinated in typical
for acyl hydrazones of salicylaldehyde O,N,O-tridentate chelate manner. It has been
shown that synthesis conditions such as different starting Cu2+ compounds, solvent
type, concentration of reagents, pH of reaction mixture and presence of secondary
ligands have a great influence on a structure of resulting complex compounds:
-
Complexation of Cu(NO3)2 with HBPAH in the ratio 1:2 resulted in tetragonal-
bipyramidal bisligand coordination compound I in which one molecule is coordinated
in molecular form and another one as monodeprotonated phenolic anion;
-
Using of CuCl2 as starting compound led to formation of two different
coordination compounds depending on starting reagents concentration and type of
solvent. Diluted solutions and water-ethanol solvent favor formation of mononuclear
complex II, increasing of reagent concentrations and 96% ethanol lead to dimeric
complex III;

23
ACCEPTED MANUSCRIPT
-
Complexation in ethanol-pyridine solution (pH ≈ 9) resulted in HBPAH
coordination in imidol tautomeric form and formation of neutral binuclear complex
IV in which the fourth vacant equatorial position of Cu2+ polyhedron is occupied by
coordinated pyridine molecule.
UV-Vis and EPR study of complexes I-IV in solutions showed that all binuclear
complexes do not retain their binuclear structure upon dissolution. Moreover, despite
the fact that Cu2+ complexes usually positioned as very stable, complexes II-IV
readily undergo solvolysis in solution due to substitution of monodentate chloride and
pyridine secondary ligands by solvent molecules. Furthermore, the complex I which
contains two tridentate chelate coordinated HBPAH molecules undergo dissociation
of one HBPAH molecule upon dissolution.
Acknowledgements
All authors thank the Ukrainian Academy of sciences for financial support
(grant 35/17H of National Academy of Sciences of Ukraine).
Appendix A. Supplementary data
Crystallographic data for all structures have been deposited in the Cambridge
Crystallographic Data Centre. CCDC 1518631-1518634 contain the supplementary
crystallographic data for complex compounds I-IV. Copies of the data can be
obtained free of charge by an application to the Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: +44 1223 336 033; E-Mail:
deposite@ccdc.cam.ac.uk; internet: http://www.ccdc.ac.uk).
Diffuse reflection spectra of complexes I-IV and frozen solutions EPR spectra
of complexes I and II are given as Fig. S1, S2 in the supplementary data.
References
[1] S. Rollas, S.G. Küçükgüzel, Molecules 12 (2007) 1910-1939,
doi:10.3390/12081910.
[2] B.K. Kaymakçıoğlu, S. Rollas, Il Farmaco 57 (2002) 595–599,
doi:10.1016/S0014-827X(02)01255-7.
[3] M.V. Pillai, K. Rajeswari, T. Vidhyasagar, J. Mol. Struct. 1076 (2014) 174–182,
doi:10.1016/j.molstruc.2014.07.050.
[4] A.A.R. Despaigne, F.B. Da Costa, O.E. Piro, E.E. Castellano, S.R.W. Louro, H.
Beraldo, Polyhedron 38 (2012) 285–290, doi:10.1016/j.poly.2012.03.017.

24
ACCEPTED MANUSCRIPT
[5] P. Vicini, F. Zani, P. Cozzini, I. Doytchinova, Eur. J. Med. Chem. 37 (2002)
553–564, doi:10.1016/S0223-5234(02)01378-8.
[6] H.H. Monfared, S. Sadighian, M.-A. Kamyabi, P. Mayer, J. Mol. Catal. A:
Chemical 304 (2009) 139–146, doi: 10.1016/j.molcata.2009.02.004.
[7] O. Pouralimardan, A.-Ch. Chamayou, C. Janiak, H. Hosseini-Monfared, Inorg.
Chim. Acta 360 (2007) 1599–1608, doi: 10.1016/j.ica.2006.08.056.
[8] H.H. Monfared, R. Bikas, Peter Mayer, Inorg. Chim. Acta 363 (2010) 2574–2583,
doi: 10.1016/j.ica.2010.04.046.
[9] M.U. Anwar, L.N. Dawe, S.S. Tandon, S.D. Bunge, L.K. Thompson, Dalton
Trans. 42 (2013) 7781-7794, doi: 10.1039/C3DT32732A.
[10] F. Borbone, U. Caruso, M. Causà, S. Fusco, B. Panunzi, A. Roviello, R. Shikler,
A. Tuzi, Eur. J. Inorg. Chem. (2014) 2695–2703, doi:10.1002/ejic.201400095.
[11] M. Argeri, F. Borbone, U. Caruso, M. Causà, S. Fusco, B. Panunzi, A. Roviello,
R. Shikler, A. Tuzi, Eur. J. Inorg. Chem. (2014) 5916–5924, doi:
10.1002/ejic.201402717.
[12] F. Borbone, U. Caruso, S. Concilio, S. Nabha, B. Panunzi, S. Piotto, R. Shikler,
A. Tuzi, Eur. J. Inorg. Chem. (2016) 818–825, doi: 10.1002/ejic.201501132.
[13] J. Deng, Y. Gou, W. Chen, X. Fu, H. Deng, Bioorg. Med. Chem. 24 (2016)
2190–2198, doi.org/10.1016/j.bmc.2016.03.033.
[14] E.A. Saad, M.M. Hassanien, F.W. El-lban, Biochem. Biophys. Res. Comm. 484
(2017) 579–585, doi: 10.1016/j.bbrc.2017.01.137.
[15] M.U. Anwar, K.V. Shuvaev, L.N. Dawe, L.K. Thompson, Inorg. Chem. 50
(2011) 12141–12154, doi: 10.1021/ic201891h.
[16] K.B. Gudasi, S.A. Patil, R.P. Bakale, M. Nethaji, J. Mol. Struct. 1065-1066
(2014) 179–185, doi: 10.1016/j.molstruc.2014.03.001.
[17] X.-H. Bu, M. Du, L. Zhang, X.-B. Song, R.-H. Zhang, T.Clifford, Inorg. Chim.
Acta 308 (2000) 143–149, doi: 10.1016/S0020-1693(00)00215-2.
[18] M. Albrecht, I. Latorre, G. Mehmeti, K. Hengst, I.M. Oppel, Dalton Trans. 40
(2011) 12067-12074, doi: 10.1039/C1DT10775E.
[19] E.W. Ainscough, A.M. Brodie, A.J. Dobbs, J.D. Ranford, J.M. Waters, Inorg.
Chim. Acta. 267 (1998) 27–38. doi: 10.1016/S0020-1693(97)05548-5.
[20] S. Das, S. Pal, J. Mol. Struct. 753 (2005) 68–79,
doi: 10.1016/j.molstruc.2005.05.037.
[21] L.-F. Zou, X.-Y. Yang, D.-X. Wang, Y. Gao, Y. Wang, Y.-H. Li, Asian J. Chem.
24, 7 (2012) 2909–2912.
[22] M. Sutradhar, M.V. Kirillova, M. Fátima C.G. da Silva, C.-M. Liu, A.J.L.
Pombeiro, Dalton Trans. 42 (2013) 16578-16587, doi: 10.1039/C3DT52453A.

25
ACCEPTED MANUSCRIPT
[23] J. Chakraborty, S. Thakurta, G. Pilet, D. Luneau, S. Mitra, Polyhedron 28 (2009)
819–825, doi: 10.1016/j.poly.2008.12.018
[24] H. Irving, R.J.P. Williams, J. Chem. Soc. (1953) 3192-3210,
doi: 10.1039/JR9530003192.
[25] H. A. Jahn , E. Teller, Proc. Roy. Soc. A, 161, 905 (1937) 220–235,
doi: 10.1098/rspa.1937.0142.
[26] F. Wilde, H. Lemmerhirt, T. Emmrich, P.J. Bednarski, A. Link, Mol. Divers. 18
(2014) 307-322, doi: 10.1007/s11030-013-9501-7
[27] Bruker, SAINT. Bruker AXS Inc. Madison, Wisconsin, USA, 2002.
[28] G.M. Sheldrick, SADABS. University of Gottingen, Germany, 2003.
[29] Bruker. SHELXTL. Bruker AXS Inc. Madison, Wisconsin, USA, 2001.
[30] F.H. Allen, Acta Cryst. B58 (2002) P. 380–388.
doi: 10.1107/S0108768102003890.
[31] C.-G. Yan, J. Han, L. Li, D.-M. Liu, J. Coord. Chem. 62 (2009) 825-832,
doi:10.1080/00958970802314985.
[32] B.J. Hathaway, D.E. Billing, Coord. Chem. Rev. 5 (1970) 143-207, doi:
10.1016/S0010-8545(00)80135-6
[33] A. B. P. Lever, A. Yu. Tsivadze (editor), Electronic Spectroscopy of Inorganic
Compounds, Part 2, Mir, Moscow, 1987, p. 201-216 (in Russian).
[34] Structure Correlation, Volume 1, H.-B. Burgi, J. D. Dunitz (Eds.), VCH,
Weinheim, 1994, p. 767-784.
[35] A.W. Addison, T.N. Rao, J. Reedijik, J.V. Rijn, G .C. Verschoor, J. Chem.
Soc.,Dalton Trans. (1984) 1349-1356, doi: 10.1039/DT9840001349.
[36] L.A. Kazitsina, N.B. Kupletskaya, Application of UV, IR and NMR
spectroscopy in organic chemistry (Russ.), High School, Moscow, 1971.
[37] V.P. Daniel, B. Murukan, B.S. Kumari, K. Mohanan, Spectrochimica Acta Part
A 70 (2008) 403–410. doi:10.1016/j.saa.2007.11.003.
[38] A.A. El-Sherif, T.M.A. Eldebss, Spectrochim. Acta Part A 79 (2011) 1803–
814. doi:10.1016/j.saa.2011.05.062.
[39] T.D. Smith, Y.R. Pilbrow, Coord. Chem. Rev. 13 (1974) 173-278,
doi:10.1016/S0010-8545(00)80255-6.
[40] E. Manoj, M.R.P. Kurup, A. Punnoose, Spectrochim. Acta Part A 72 (2009)
474–483, doi:10.1016/j.saa.2008.10.030.
[41] B. Viossat, F.T. Greenaway, G. Morgant, J.-C. Daran, N.-H. Dung, J.R.J.
Sorenson, J. Inorg. Biochem. 99 (2005) 355–367,
doi:10.1016/j.jinorgbio.2004.10.001.
[42] G.M. Larin, V.F. Shul’gin, Russ. J. Inorg. Chem. 51, (2006) S28-S48,
doi: 10.1134/S003602360613002X.

26
ACCEPTED MANUSCRIPT
[43] V.F. Shul’gin, E.A. Zamnius, A.N. Gusev, O.V. Konnik, E.B. Rusanov,
V.Ya. Zub, V.V. Minin, Russ. J. Inorg. Chem. 56 (2011) 1598–1602,
doi: 10.1134/S0036023611100226

Highlights
ACCEPTED MANUSCRIPT
1.
Synthesis of four Cu(II) complexes with O,N,O tridentate hydrazone of
salicyaldehyde
2.
3.
4.
5.
Influence of synthesis conditions on structure of resulted compounds
Structure determination by single-crystal X-ray diffraction
Additional characterization by IR, UV-Vis and EPR spectroscopy
Partial solvolysis of obtained complex compounds upon dissolution