Chemical and electrochemical synthesis, molecular structures, DFT calculations and optical properties of metal-chelates of 8-(2-tosylaminobenzilideneimino)quinoline

Article abstract of DOI:10.1016/j.poly.2015.12.048

Bis-chelate complexes with composition ML₂ (M²⁺ = Co, Ni, Cd and Zn) were synthesized on the basis of potential tridentate N, N, O donor Schiff base ligand - 8-(2-tosylaminobenzilideneimino)quinoline (HL) by both chemical (CS) and el

Full text of DOI:10.1016/j.poly.2015.12.048

Accepted Manuscript
Chemical and electrochemical synthesis, molecular structures, DFT calculations
and optical properties of metal-chelates of 8-(2-tosylaminobenzilideneimi-
no)quinoline
Anatolii S. Burlov, Valery G. Vlasenko, Nadezhda I. Makarova, Konstantin
А. Lyssenko, Vasiliy V. Chesnokov, Gennadii S. Borodkin, IgorS. Vasilchenko,
Ali I. Uraev, Dmitrii A. Garnovskii, Anatoly V. Metelitsa, Eugene L. Mukhanov,
Tat’yana V. Lifintseva, Ilya V. Pankov
PII:
S0277-5387(15)00798-6
DOI:
http://dx.doi.org/10.1016/j.poly.2015.12.048
POLY 11747
Reference:
Polyhedron
To appear in:
Received Date:
Accepted Date:
8 October 2015
26 December 2015
Please cite this article as: A.S. Burlov, V.G. Vlasenko, N.I. Makarova, K.A. Lyssenko, V.V. Chesnokov, G.S.
Borodkin, I.S. Vasilchenko, A.I. Uraev, D.A. Garnovskii, A.V. Metelitsa, E.L. Mukhanov, T.V. Lifintseva, I.V.
Pankov, Chemical and electrochemical synthesis, molecular structures, DFT calculations and optical properties of
metal-chelates of 8-(2-tosylaminobenzilideneimino)quinoline, Polyhedron (2015), doi: http://dx.doi.org/10.1016/
j.poly.2015.12.048
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CHEMICAL AND ELECTROCHEMICAL SYNTHESIS, MOLECULAR
STRUCTURES, DFT CALCULATIONS AND OPTICAL PROPERTIES OF
METAL-CHELATES OF 8-(2-
TOSYLAMINOBENZILIDENEIMINO)QUINOLINE
Anatolii S. Burlova, Valery G. Vlasenkob, Nadezhda I. Makarovaa,
Konstantin А. Lyssenkoc, Vasiliy V. Chesnokova, Gennadii S. Borodkina,
Igor S. Vasilchenkoa,∗, Ali I. Uraeva, Dmitrii A. Garnovskiia,d, Anatoly V.
Metelitsaa, Eugene L. Mukhanova, Tat’yana V. Lifintsevae, Ilya V. Pankova,e
aInstitute of Physical and Organic Chemistry of Southern Federal University, Stachki ave. 194/2, Rostov-on-
Don, Russian Federation
bInstitute of Physics of Southern Federal University, Stachki ave. 194, Rostov-on-Don, Russian Federation
cNesmeyanov Institute of Organoelement Compounds, Vavilova St. 28, 119991 Moscow, Russia
dSouthern Scientific Centre of Russian Academy of Sciences, Chekhova ave. 41, Rostov-on-Don, Russian
Federation
eSouthern Federal University, Sadovaya str. 105/42, Rostov-on-Don 344006, Russian Federation
ABSTRACT
Bis-chelate complexes with composition ML2 (M2+ = Co, Ni, Cd and Zn) were synthesized
on the basis of potential tridentate N, N, O donor Schiff base ligand - 8-(2-
tosylaminobenzilideneimino)quinoline (HL) by both chemical (CS) and electrochemical
synthesis (ES). CS of zinc complexes leads to obtaining the compounds with composition
ZnLCOOCH3. Structure and properties of the prepared compounds have been studied by
1
means of elemental analysis, IR, H NMR spectroscopy as well as quantum-chemical
computations. Electronic spectra of UV-vis absorption and photoluminescence for
cadmium and zinc complexes were studied in acetonitrile solution. Crystal structure of zinc
and cadmium complexes was determined by X-Ray analysis. In the zinc complex ZnN6
coordination site was realized due to involving the nitrogen atom of quinoline fragment in
coordination to the metal ion. Meanwhile due to X-Ray analysis data cadmium complex
∗ Corresponding author. Tel.: +7 8632434776.
E-mail address: vas@ipoc.sfedu.ru (I.S. Vasilchenko).

possesses CdN6O surroundings with additional coordination of oxygen atom of tosylamino
group from one of the ligand. Cobalt and zinc complexes were assigned to have the
octahedral structures on the basis of the physical chemical measurements.
1. Introduction
Among metal complexes of acyclic azomethine ligands there is special place for
chelates of zinc, cadmium and other metals with coordination sites MN4, MN2O2 that
were obtained on the basis of Schiff bases (I) derived from 2-hydroxy- or 2-
tosylaminobenzaldehydes possessing photo- (PL) and electroluminescent (EL)
properties. Zinc and cadmium chelate complexes with azomethine ligands are used as
emitting and electron-transport layers for OLED devices [1-7] due to their synthetic
availability, high PL and EL characteristics, high thermal stability, accessibility of
vacuum sublimation for obtaining the homogeneous films during production of OLED
layers.
Complexes containing quinoline moiety attract great interest despite more than 20
years of history for proposed by Tang and Van Slyke [8] usage of tris-(8-
hydroxyquinolinato) aluminum. This compound was firstly used for development of the
OLED device working with low voltage [9-14].
There are well known Schiff base ligands emitting in the blue spectral region
such as derivatives of salicylic aldehydes and 2,4-dimethyl-7-aminoquinolines and their
zinc complexes [15]. Emission maxima of PL ligands are located in the area λPL=476-
524 nm. For zinc complexes these maxima undergoes bathochromic shift and exhibits
in the area λРL=503-532 nm. Quantum yields of luminescence for ligands are minor
(φ=0.001-0.005), while they are increasing for complexes up to φ=0.15.
Complexes of bis{3-methyl-1phenyl-4-[(quinoline-3(or 6)-imino)-methyl]1-H-
pyrazol-5-onato}zinc(II) were synthesized [16, 17]. Bis{3-methyl-1-phenyl-4-
[(quinoline-3-imino)-methyl]1-H-pyrazol-5-onato}zinc (II) was used to obtain OLED
with configuration ITO/Cupc/2-TNTA/Spiro-TPD/Zn complex/BCP/BPhen/LiF/Al
emitting in the yellow spectral region (λEL = 600 nm) with a luminance of 800 Cd/m2 at
a voltage of 10 V that corresponds to luminous efficiency of 0.5 Lm/W. For the device

with electroluminescent layer of bis{3-methyl-1phenyl-4-[(quinoline-6-imino)-
methyl]1-H-pyrazol-5-onato}zinc (II) brightness characteristics are 200 Cd/m2 at a
voltage of 13 V.
The similar complexes of zinc and cadmium with 3- (or 6)-[2-(N-
tosylaminobenzilidene)]aminoquinoline were synthesized [17]. OLED device was
produced by using bis{[6-(2- tosylaminobenzilidene)]amino]quinolinato}zinc(II) for an
emitting layer. Device emitted yellow light with CIE (x=0.463, y=0.484), brightness
was150 Cd/m2 at a voltage of 10 V.
Here we report the chemical [20] and electrochemical [21] synthesis of novel
cobalt, nickel, zinc and cadmium complexes on the base of 8-(2-
tosylaminobenzilideneimino)quinoline aimed for searching new metal-chelates with PL
properties as potential materials for OLED[18, 19].
2. Experimental
2.1. Materials required and general methods
All starting materials and solvents were used as commercial products. 2-
tosylaminobenzaldehyde was prepared as described earlier [22]. C, H, N elemental
analysis was performed in the analytical laboratory of Institute of Physical and Organic
Chemistry (SFU, Rostov-on-Don, Russia). The metal content was determined
gravimetrically.
Infrared spectra were recorded on a «Varian Excalibur-3100» FT-IR
spectrophotometer by attenuated total internal reflection technique.
1
NMR H spectra were measured on a «Advance-600» (Bruker) spectrometer at
2
ambient temperature in DMSO-d6 with the signal of residual H of the solvent as the
internal reference.
The magnetic susceptibility of the solid state samples has been measured by the
Faraday's method at room temperature.
UV/vis spectra were registered on «Varian Cary 100» spectrophotometer. Spectra of
fluorescence were measured on a «Varian Cary Eclipse» grating spectrofluorometer.

Acetonitrile (Aldrich) of spectral grade were used for preparing the solutions. The
fluorescence quantum yield were determined by Parker-Reese technique [23] using 3-
methoxybenzathrone in toluene (ϕ = 0.1, λirr. =365 nm) as a standard luminophore [24].
2.2. Ligand synthesis
Synthesis of 8-(2-Tosylaminobenzilideneimino)quinoline I: A hot solution of
1.44 g (0.01 mol) 8-aminoquinoline in 10 ml of ethanol was added to the hot solution of
2.75 g (0.01 mol ) 2-tosylaminobenzaldehyde [22] in 50 ml of ethanol. Mixture was
refluxed for 2 hours. The formed yellow precipitate was filtered off and recrystallized
о
from ethanol-dioxane (3:1). Yellow crystals with Tm 190 – 192 С; yield 84%. Found,
%: С 68.15, Н 4.35, N 10.11. C23H19N3O2S calculated, %: С 68.81, Н 4.77, N 10.47.
2.3. Synthesis of complexes
2.3.1. Chemical synthesis
Solutions of cobalt(II) or nickel(II) acetate tetrahydrate (0.001 mol) or solution of
zinc(II), cadmium(II) acetate dihydrate (0.001 mol) in 10 ml of ethanol were added to
the warm solution of 0.8 g (0.002 mol) azomethine I in 40 ml of ethanol. Mixture was
refluxed for 2 hours. After cooling precipitate of complexes was filtered off and
recrystallized from chloroform-ethanol mixture (1:2).
2.3.2. Electrochemical synthesis
Electrochemical synthesis of complexes II was performed by standard method
[25] using the reaction of azomethine I with anode complex-former (Co, Ni, Zn, Cd)
dissolving in methanol.
Electrochemical cell could be described as below:
Cathode (Pt): 2HL + 2е → 2L-+H2
Anode (M= Co, Ni, Zn, Cd): M0 - 2е→ M2+
Solution: 2L- + M2+→ ML2

Methanol solution (25 ml) containing 0.4 g (0.001 mol) of ligand I and 0.01 g of
Et4NClO4 as a conductive additive. Electrolysis was carried out during 2 hours under
constant electric current of 40 mA and voltage 15V.
Obtained precipitates of metal complexes were filtered off, washed three times
with 5 ml of methanol and dried in vacuum.
2.3.3. Bis[8-(2-tosylaminobenzylideneimino)quinolinato]nickel(II) (IIa).
Brown crystals with Tm > 250 оС, yield 62% (CS), 75% (ES).
CS: found, %: С 64.18, Н 4.28, N 9.82, Ni 6.79.
ES: found, %: С 64.25, Н 4.23, N 9.76, Ni 6.82.
For C46H38N6O4S2Ni calculated, %: С 64.27, Н 4.22, N 9.78, Ni 6.83.
2.3.4. Bis[8-(2-tosylaminobenzilideneimino)quinolinato]cobalt(II) (IIb).
Brown powder with Tm > 250 оС, yield 60% (CS), 65% (ES).
CS: found, %: С 64.37, Н 4.29, N 9.80, Cо 6.97.
ES: found,%: С 64.39, Н 4.25, N 9.87, Cо 6.94.
For C46H38N6O4S2Со calculated, %: С 64.25, Н 4.22, N 9.77, Cо 6.85.
2.3.5. Bis[8-(2-tosylaminobenzilideneimino)quinolinato]zinc(II) (IIc).
Yellow powder with Tm > 250 оС. Yield 55% (CS).
CS: found, %: C 63.71, H 4.25, N 9.82, Zn 7.59.
ES: found, %: C 63.68, H 4.22, N 9.77, Zn 7.62.
For C46H36N6O4S2Zn calculated, %: C 63.77, H 4.19, N 9.70 S 7.40 Zn 7.55.
2.3.6. [8-(2-tosylaminobenzylideneimino)quinolinato]zinc(II) acetate (IIIb).
Yellow powder with Tm > 250 оС. Yield 65% (ES).
ES: found, %: C 57.42, H 4.09, N 8.10, Zn 12.57.
For C25H21N3O4SZn calculated, %: C 57.21, H 4.03, N 8.00, Zn 12.46.

2.3.7. Bis[8-(2-tosylaminobenzilideneimino)quinolinato]cadmium(II) (IId).
Yellow crystals with Тm>250 оС, yield 56% (CS), 68% (ES).
CS: found, %: С 60.51, Н 3.68, N 9.25, Cd 12.42.
ES: found, %: С 60.56, Н 3.73, N 9.21, Cd 12.49.
For C46H38N6O4S2Сd calculated, %: С 60.49, Н 3.47, N 9.20, Cd 12.31.
1
13
Chemical shifts in NMR H and C spectra of solutions I, IIc, IId and IIIb in
DMSO-D6 are presented in table 1.
Table 1.
2.4. X-ray diffraction
X-ray diffraction of compounds IIc and IId was carried out on the diffractometer
«Bruker SMART APEX2» (MoKα-irradiation, graphite monochromator, θ-scanning).
Structure was solved by method of least squares with anisotropic full-matrix
approximation with F2 . Analysis of differential Fourier synthesis shown that in crystal
hkl
of IIc and IId there is disorder of solvent molecules: molecules of water in six positions
for Zn and dichloromethane in three positions for Cd. Impact of solvent molecules on
the dissipation was excluded by using Squeeze procedure [26] taking into consideration
complex type of their disordering. In both cases presence of solvent molecules was
accounted for calculation of all structural characteristics such as density, F (000) etc.
Positions of hydrogen atoms were calculated geometrically and refined in the isotropic
approximation by the riding model.
Main crystallographic data and parameters of refining are presented in table 2. All
calculations were carried out with SHELXTL PLUS software [27]. Crystals of IIc and
IId suitable for XRD were obtained by slow evaporation of chloroform-methanol (1: 1)
solutions.
Table 2

2.5. Quantum-chemical calculations
All geometries I-III in the ground state were fully optimized at the DFT level
using GAUSSIAN-03 computer program [28]. For calculations the hybrid three-
parameter functional B3LYP [29] and the standard split-valence polarization basis set 6-
31G(d) [30] were chosen. Simulations of UV-vis absorption spectra for these molecules
were accomplished in the framework of Dependent Density Functional Theory (TD-
DFT) using optimized atomic structure parameters with account of solvent effects by
the standard polarizable continuum model (PCM) with integral equation formalism
method [31].
3. Results and discussion
As it was shown previously [10, 18] for complexes СuL2 the reaction between the
potentially tridentate azomethine I (LH, X=NTs) and copper(II) acetate dehydrate leads
to mononuclear CuLCOOCH3 complex (IIIа) preserving acetate group instead of
expected bis-chelate II (Scheme 1). Bis-chelate CuL2 complexes (II) are obtained in the
case of ES.
25CH3
24
25CH3
24
25CH3
24
26
'
23
22
23
'
23
22
23
CH3
'
23
22
23
'
22
'
22
21
'
CS, ES
22
CS
21
O
O S O
N3
21
O
O S O
N3
5
8
O S O
N3
Zn2
5
8
4
2
4
19
5
8
6
7
18
19
4
6
7
H
18
M/2
N
19
1N 11
10
6
7
18
N
1N 11
10
20
17
16
N
1N
10
20
17
16
9
9
20
17
16
11
9
H
15
14
12
H
15
14
12
H
15
14
12
13
13
13
III
I
II
M2+= Ni (IIa), Co (IIb), Zn (IIc), Cd (IId)
Scheme 1
All complexes II synthesized by CS and ES methods possess ML2 composition
due to elemental analysis. The only exception is zinc complex IIIb obtained by CS

method. According to data of elemental analysis IIIb possess ZnLCOOCH3
composition.
3.1. Spectroscopic properties and magnetochemical measurements
NH-group proton signals have been registered in the spectra of azomethine I at
δ=13.22 ppm and they were shown to disappear in NMR 1H spectra of IIc,d and IIId
(M = Zn, Cd) that indicates deprotonation of ligand and obtaining the chelate
complexes.
1
Comparative analysis of H, 13C, 15N NMR spectra for compound I and its
metallochelates IIc,d and IIIb has been presented in table 1. Chemical shift for 113Cd
nuclei is -525.51 ppm. Signals were assigned by using the correlation of COSY, HSQC,
HMBS techniques.
13
13
Positions of C signals change insignificantly (for C signals scale) both for
atoms located on the periphery of ligands system as well as for atoms close to the
coordination site (specifically C(5-8), C(10-18), C(20-25), atoms numeration is on the
scheme 1). On the other side shift of the protons signals for H(10), H(18), H(22) and
H(23) in the high field region in comparison with azomethine I spectra (table 1) could
be related to the closeness with electron-donor atoms forming coordination sphere.
Involving the N(3) atom into coordination is confirmed by the disappearance of
proton’s signal of H(3) in tosylamino-group near the 13.22 ppm region.
Involving the N(1) and N(19) atoms into coordination is directly proved by 30-50
ppm shift of their signals in the high-field region. Also it is proved by the spin – spin
3
coupling through coordinated nitrogen atoms with constants JH(10)-Cd = 20.65 Hz and
3JH(18)-Cd = 13.85 Hz. Unfortunately we were not able to find signals of N(3) nitrogen
atom in the 15N NMR spectra but its involving in the coordination is of no doubt.
IR spectral and magnetic properties for compounds I, II and IIIb are presented in
table 3. All IR-spectra of IIa-d complexes are identical (table 3). Disappearance of the
νNH absorption band (near 3040 cm-1) is observed as well as reducing of the frequency
of valent vibrations for СН=N (at 3-15 cm-1), νasSO2 (at 45-50 cm-1) and νsSO2 (at 24-28
cm-1) that indicates the formation of chelate structures. In IR spectrum of IIIb
absorption band at 1644 см-1 corresponding to νСО of acetate group is registered.

Proton signals for CH3 moiety of acetate group are presented in NMR 1Н spectra of IIIb
complex in the high field region at 1.73 ppm that indicates the formation of complex
with preserving the acetate anion.
Values of the effective magnetic moment for chelates IIа (3.07 MB) and IIb
(4.85 MB) (table 3) are typical for Ni(II) and Co(II) ions with octahedral surroundings.
Table 3.
1
13
IR and Н, С spectra of compounds obtained by ES method coincide with data
for complexes obtained by CS.
3.2. Molecular structures of IIc and IId
Molecular structure of complexes IIc,d was determined by X-Ray analysis and
shown on Fig. 1. Both organic ligands in the complex are tridentate-coordinated to zinc
ion by quinoline (N(1), N(1′)), azomethine (N(2), N(2′)) and amine (N(3), N(3′))
nitrogen atoms. Coordination polyhedron of Zn(1) is distorted octahedral. Ligands in
complex possess almost the similar structure. Both ligands are non-planar: dihedral
angles between average planes of atoms from benzene and quinoline cycles are 45.97
and 44.68º correspondingly.
Six-membered metal-chelate rings of Zn(1)N(2)C(10)С(11)C(12)N(3) and
Zn(1)N(2′)C(10′)С(11′)C(12′)N(3′) have chair conformations and Zn(1) ion is
significantly displaced from average plane of other atoms (on 1.030 and 0.911 Å
correspondingly).
Five-membered rings of Zn(1)N(1)C(5)C(6)N(2) и Zn(1)N(1′)C(5′)C(6′)N(2′)
have envelope conformations with Zn(1) as a flap atom that displaced from average
plane of other atoms on 0.575 and 0.601 Å correspondingly.
Fig. 1.

There is weak stacking interaction in single crystal of complex IIc between
quinoline cycles of two nearby molecules; cycles are strictly coplanar, distance between
average planes is 3.326 Å, distance between centers - 3.616 Å (Fig. 2).
Fig. 2.
Structure of cadmium complex IId (Fig. 3) exhibits the number of significant
distinctions. One ligand is tridentate-coordinated to cadmium ion by N(1), N(2) and
N(3) atoms; second ligand has additional coordination of oxygen atom of tosyl group
O(1′) (d Cd(1)–O(1′) 2.665(2) Å). Coordination polyhedron of cadmium ion could be
described as distorted pentagonal bipyramidal with N(2), N(1′), N(2′), N(3′) and O(1′)
atoms lying in the basis while N(1) and N(3) atoms occupied axial positions.
Fig. 3.
Coordination of oxygen atoms of tosyl group to cadmium ion leads to noticeable
flattening of the tetradentate-coordinated structure of the ligand.
Dihedral angle between average planes of atoms from benzene and quinoline
cycles is 28.87º, whereas it is equal to 41.41º for tridentate-coordinated structure. It
leads to significant inequality as concerns to structure of metallochelate rings. Both six-
membered rings have chair conformation, but Cd(1) ion is displaced from average plane
of other atoms on 0.470 Å for tridenate-coordinated ligand and on 0.998 Å for the
second ligand
Five-membered
metallochelate
rings
Cd(1)N(1′)C(5′)C(6′)N(2′)
and
Cd(1)N(1)C(5)C(6)N(2) possess envelope conformations with Cd(1) as a flap atom that
displaced from average plane of other atoms on 0.621 and 0.477 Å, correspondingly.
Structure of complex IId also contains 0.5 molecule of water forming hydrogen
bond O(1W)-H(1WB)...O(1′) in crystal with following characteristics: d(D–H) 0.90,
d(H...A) 2.05, d(D...A) 2.947(9) Å, ∠(DHA) 174º.

Select interatomic distances and bond angles for IIc,d coordination compounds are
presented in tables 4 and 5.
table 4
table 5
3.3. Photoluminescent properties
The study of optical and photoluminescent behavior of 8-(2-
tosylaminobenzilideneimino)quinoline I as well as cadmium (IId) and zinc (IIIb)
complexes obtained on its base has been carried out in acetonytrile solution.
Obtained data are presented in table 6. Electronic absorption spectrum and
photoluminescent of solutions I, IId, IIIb are presented in figure 4 as an illustration.
Table 6
Fig. 4.
The structural analogues of azomethine I were previously investigated by methods
of absorption and luminescent spectroscopy [31] and it was shown that azomethine
molecules could exist in at least two tautomeric forms - benzoid Ia and quinoid Ib
(scheme 2). The equilibrium between the forms depends on temperature and solvent
properties.
The structural and electronic properties of the tautomeric forms Ia and Ib have
been calculated in the frame of density functional theory both in gas phase and DMSO
solution. The most stable isomer is Ia due to results of quantum-chemical modeling and
its energy is on 6.22 kcal/mol lower than that for Ib both in gas phase and acetonytrile
solutions.
Molecules of aniles of ortho-tosylaminoaldehydes as well as aniles of ortho-
hydroxyaldehydes undergo intermolecular proton transfer in excited state under UV
irradiation. This process is responsible for appearing the fluorescence with anomalous
Stokes shifts at 77 K and obtaining the fluorescent keto-structures.

Ts
H
Ts
H
N
N
N
N
hν
N
N
Ib
Ia
Scheme 2
Wide absorption band at the 300 - 400 nm region with maximum at 337 nm that
is typical for the benzoid Ia form is observed in the electronic absorption spectra of
azomethine I in acetonitrile solution at 293 K (Table 6, Fig 4).
PL properties were not observed in the solution as it was the case for previously
studied aniles of ortho-tosylaminobenzaldehydes which were non fluorescent in benzoid
form at room temperature [33].
Electronic absorption spectra of solutions of Cd complex (IId) and Zn complex
(IIIb) (Table 6, Fig 4) in acetonytrile solution are characterized by the longwave
absorption bands with maxima at 398 nm (IId) and 399 nm (IIIb) as well as molar
extinction coefficient equal to 28400 and 14900 mol-1cm-1 correspondingly.
As it is shown on the Fig. 4 intensity of the absorption of bis-chelate complex
with composition CdL2 (IId) is approximately twice as large as the absorption of
complex with ZnLCOOCH3 composition (IIIb).
According to experimental data (Table 6) emission bands for zinc and cadmium
IIIb and IId complexes undergo bathochromic shift on 127 nm (λРС =524-527 nm) in
comparison with the absorption bands.
Emission bands in fluorescent spectra of IIIb and IId are bathochromically
shifted on approximately 30 nm in comparison with previously obtained complexes
have being synthesized on the base of 3- or 6-(2-tosylaminobenzilideneimino) quinoline
ligands [17].

Complexes exhibit fluorescent properties in solution (green light was observed):
metal complexes (Fig. 4) are characterized by wide band of fluorescence at the 420 –
750 nm region with maxima at 527 (IId) and 524 nm (IIIb).
PL band’s maxima undergo bathochromic shift of about 27 nm compared to PL
peaks of previously studied zinc (II) and cadmium (II) bis[3- or 6-
(tosylaminobenzilideneimino)quinoline] [32] that have λPL = 495-497 nm.
Comparing of PL properties of zinc and cadmium bis[8-(2-
tosylaminobenzilideneimino)quinoline]
complexes
with
zinc
bis[8-(2-
hydroxybenzilideneimino)quinoline] complex (λPL = 540 nm, φ= 0.39) [33] reveals that
replacing hydroxy group at the 2-tosylamino group leads to insignificant (about 11-12
nm) hypsochromic offset of PL bands maxima and about two order of magnitude
reduction of the quantum yield of PL.
The excitation spectra were also registered as dependence between wave length
of the exiting radiation and intensity of luminescence at a fixed wave length.
Fluorescent excitation spectrum combined with absorption spectrum of Cd complex
(IId) is shown at Figure 5 as an illustration.
Figure 5
Fluorescent excitation spectrum is in a good agreement with absorption spectrum
that indicates the validity of assignment of fluorescence to complex compound of the
identified structure. Quantum yields of fluorescence of Cd and Zn complexes (IId) and
(IIIb) are low and equal to 0.007 and 0.003 correspondingly, which is more than two
orders of magnitude less than the quantum yield of similar complexes containing 3- or
6-aminoquinoline fragment [32]. Therefore the EL properties of cadmium (IId) and
zinc (IIIb) complexes have not been studied in this work.
3.4. DFT study of UV-vis spectra and molecular structures of IId and IIIb
Calculations of absorption spectra of the IIIb and IId complexes have been
accomplished in the present work using the time-dependent density functional theory
(TD-DFT) method. The assignment of the excitation energies to the experimental bands

was performed on the basis of the energy values and oscillator strengths. The B3LYP
functional and 6-31(d) basis set were chosen because it was proved to provide accurate
structures and reasonable UV-vis spectra for a variety of organometallic complexes.
Experimental and theoretical absorption spectra for IIIb and IId are compared on
Fig. 4. Quantitative characteristics of absorption bands of the theoretical electronic
absorption spectra and their interpretations are presented in Tables 6, 7.
Table 7
In electronic absorption spectra of IIIb absorption band at 329 nm reveals the high
value of oscillator strength and is determined by single electronic transition from π-
bonding orbital (HOMO) up to π* - antibonding orbital (LUMO) of ligands. HOMO and
LUMO of IIIb is presented on Fig. 6. As it is shown HOMO has maximal contribution
of π MO of benzilideneimine part of the ligand while π* LUMO is mostly localized on
quinoline moiety.
Figure 6
Electronic absorption spectra of Cd complex reveals longwave absorption band at
401 nm which is determined by the series of electronic transitions HOMO → LUMO,
HOMO → LUMO+1, HOMO-1→ LUMO. Oscillation strength for the most longwave
transition HOMO → LUMO is insignificant and electronic transition HOMO-1→
LUMO makes main contribution into appearing of the absorption band. HOMO for IId
makes the maximal contribution of π MO of quinoline fragment while π* LUMO is
mostly localized on benzilidenimime moiety in contrast to Zn complex IIIb. The bands
at 329 nm (IIIb) and 341 nm (IId) in the electronic absorption spectra correspond to
electronic transitions HOMO-2 → LUMO and HOMO-3 → LUMO, HOMO-3 →
LUMO, HOMO-2 → LUMO+1, correspondingly (Table 7).
4. Conclusion
Thus, the present results and the data [17] show that the implementation of different
composition and structure of the metal complexes depend on the position of the amino

group (3, 6 or 8) in the quinoline moiety of azomethine I, the nature of the metal and the
method of synthesis. Five-coordinated chelate complexes of copper (II) CuL2 and
CuLCOOCH3 [18] were synthesized from potentially tri-dentate ligand - 8-(2-
tosylaminobenzilideneimino)quinoline. Chemical synthesis from metal acetates leads to
obtaining of the complexes ML2 (M=Ni, Co, Cd) and ZnLCOOCH3 for zinc. Chelates
ML2 were obtained with nitrogen atom of quinoline fragment participating in the
coordination under the conditions of electrochemical synthesis. Additional coordination
of the nitrogen atom of quinoline fragment is realized only in the case of 8-
aminoquinoline based ligands.
PL and EL properties of zinc and cadmium complexes depend on the position of
the amino group in 3, 6 or 8-quinoline moiety. PL band’s maxima of zinc and cadmium
bis[8-(2-tosylaminobenzilideneimino)quinolines] undergo bathochromic shift by about
27 nm compared to PL peaks of previously studied zinc(II) and cadmium(II) bis[ 3- or
6-(2-tosylaminobenziledeneimino)quinoline] complexes, and fluorescence quantum
yields are two orders of magnitude smaller.
Spectral properties of zinc and cadmium complexes are determined by the
position (3, 6 or 8) of quinoline moiety in azomethine ligand. Additional coordination to
metal
atom
by
nitrogen
atom
of
quinoline
moiety
of
8-(2-
tosylaminobenzilideneimino)quinoline ligand leads to the obtaining of more rigid
structures of Zn and Cd complexes that appears in more significant bathochromic shift
of the fluorescent bands. Quantum yields of the fluorescence are insignificantly affected
by the position of amino group in the quinoline moiety.
Acknowledgements
IR and NMR spectra were obtained using facilities of the "Molecular
Spectroscopy" Multi-user Center of the Southern Federal University. This work was
performed in the framework of the Project Part of the State Assignment in Academic
Areas (Project No. 4.742.2014/K).

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Fig. 1. Molecular structure of IIc complex (thermal ellipsoids are presented with 30 %
possibility, hydrogen’s atoms are not shown).

Fig. 2. Packing of molecules of complex IIc in single crystal (view along
crystallographic axis c, hydrogen’s atoms are not shown )

Fig 3. Molecular structure of IId complex (thermal ellipsoids are presented with
30 % possibility , hydrogen’s atoms are not shown).

3
2,0
1,5
1,0
0,5
0,0
I Abs (1)
2,0
1,6
1,2
0,8
0,4
0,0
III Abs (2)
IId Abs (3)
IId Fl (4)
III Fl (5)
2
1
4
5
300
400
500
600
700
Wavelength (nm)
Fig. 4. UV-vis (1 - 3) and fluorescence emission (λex=400 nm) (4, 5) spectra of
compounds I (1), IId (3, 4) and III (2, 5) in acetonitrile (с = 2·10-5 M, l = 1 cm) at 293
K. For comparison UV–Vis spectra of IId and III calculated by TD-DFT (dash line).
The spectra have been broadened using a Lorentzian function.

Fig. 5. UV-vis (1), fluorescence emission (λex=400 nm) (2) and fluorescence excitation
(λobs=530 nm) (3) spectra of IId in acetonitrile (с = 2·10-5 M, l = 1 cm) at 293K.

III
IId
LUMO -2.01 eV
LUMO -2.32 eV
HOMO -5.66 eV
HOMO -5.15 eV
Fig.6. Visualization of HOMO and LUMO distributions and the calculated frontal
orbital energies for III and IId.

Table 1. Chemical shifts in NMR 1H, 13C, 15N spectra of compounds I, IIc, IId and III (DMSO-d6)
Compound
1(15N) 2(113Cd) 3(1H,15N)
13.22
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18 19(15N) 20
21
22
23
24
25
26
Nucl.
1
7.68 7.46 7.19 7.72
8.86
7.56 7.67 7.91
8.43 7.63 9.00
7.95 7.31
2.29
H
I
13
C/
15
N
309.69
122.13 138.79 117.86 132.14 122.92 134.02 121.94 163.64 146.17 117.83 126.60 126.12 128.46 135.91 121.91 150.10 307.10 141.60 136.54 126.82 129.47 143.36 20.66
1H
7.23 7.31 7.01 7.68
7.50 7.21 6.82 7.68
9.23
8.92
8.27 7.84 8.12
7.84 7.60 7.70
8.77 7.89 9.04
8.20 7.34 8.72
7.71 7.18
7.57 7.00
2.18
2.21
IIc
1
H
IId
III
13
15
274.61 -525.51
255.83
150.42 119.76 132.51 117.95 139.22 122.72 169.28 144.24 118.64 127.55 126.09 127.69 137.75 121.82 148.56 273.04 138.84 140.83 126.86 128.73 130.22 20.69
7.23 7.31 7.00 7.68 9.23 8.27 7.85 8.11 8.75 7.89 9.01 7.71 7.18 2.26 1.73
147.63 122.12 133.23 120.57 136.70 124.00 164.89 139.49 116.98 127.96 127.50 128.62 139.87 123.23 150.48 254.60 139.67 140.97 126.69 129.05 141.20 20.77
C/
N
1H
13C/15
N

Table 2. Crystal data and structure refinement parameters for IIc and IId
Parameter
Formula
IIc
IId
C46H36N6O4S2Zn, 0.5 C46H36CdN6O4S2, 0.5 (H2O),
(H2O)
875.31
CH2Cl2
1009.28
Molecular weight
T, K
120
Triclinic
P-1
120
Triclinic
P-1
Crystal system
Space group
Z
2
2
a, Å
12.0859(13)
13.3355(15)
15.5460(17)
70.291(2)
67.365(2)
68.573(2)
2095.6(4)
1.387
13.5684(8)
13.7208(8)
14.1257(8)
68.8299(10)
79.2373(11)
66.1039(10)
2239.6(2)
1.497
b, Å
c, Å
α, degree
β, degree
γ, degree
V, Å3
ρвыч, г·см-3
µ, cm-1
7.39
7.53
F(000)
906
1030
2θmax, °
60
58
Number of measured
reflections
Number of independent
reflections
25118
12132
6157
534
20627
11811
9879
543
Number of reflections
with I>2σ(I)
Number of parameters
refined
R1
0.0550
0.1129
0.953
0.0391
0.0894
0.864
wR2
GOF
Residual electron density,
0.698/-0.552
1.857/-0.616
(∆ρmin/∆ρmax), e·Å-3
Data CCDC
CCDC 1415982
CCDC 1415987

Table 3. Physical-chemical characteristics of azomethine I and complexes II, III
№ М νNH,cm1 νСО,cm-1 νCH=N,cm-1 νasSO2,cm-1 νsSO2,cm-1 µэфф, MB
3040 br.
-
1620
1615
1617
1620
1605
1619
1334
1289
1268
1280
1283
1280
1157
1129
1133
1129
1133
1130
-
I
IIa Ni
-
-
-
-
-
3.07
Co
Zn
Cd
Zn
-
4.85
IIb
IIc
IId
III
-
-
-
-
-
1644

Table 4. Selected bond lengths d and angles α in coordination polyhedron of zinc
atom in molecule IIc
Bond
d, Å
Bond
d, Å
Zn(1)–N(2′)
Zn(1)–N(2)
Zn(1)–N(3′)
2.062(2)
2.088(2)
2.112(2)
Zn(1)–N(3)
Zn(1)–N(1)
Zn(1)–N(1′)
2.138(2)
2.275(2)
2.313(2)
Angle
Angle
α, degree.
α, degree.
N(2')Zn(1)N(2)
N(2')Zn(1)N(3')
N(2)Zn(1)N(3')
N(2')Zn(1)N(3)
N(2)Zn(1)N(3)
N(3')Zn(1)N(3)
N(2')Zn(1)N(1)
N(2)Zn(1)N(1)
161.74(9)
86.51(8)
107.55(8)
105.80(8)
85.24(9)
94.03(9)
90.41(8)
76.00(9)
N(3')Zn(1)N(1)
N(3)Zn(1)N(1)
N(2')Zn(1)N(1')
N(2)Zn(1)N(1')
N(3')Zn(1)N(1')
N(3)Zn(1)N(1')
N(1)Zn(1)N(1')
99.79(8)
159.33(8)
75.61(8)
89.05(8)
161.40(8)
95.69(8)
75.66(8)

Table 5. Selected bond lengths d and angles α in coordination polyhedron of
cadmium atom in molecule IId
Bond
d, Å
Bond
d, Å
Cd(1)–N(3)
Cd(1)–N(3′)
Cd(1)–N(2′)
2.3072(19)
2.3575(19)
2.3678(19)
Cd(1)–N(2)
Cd(1)–N(1)
Cd(1)–N(1′)
2.4017(18)
2.4059(19)
2.433(2)
Angle
Angle
α, degree
α, degree
N(3)Cd(1)N(3')
N(3)Cd(1)N(2')
N(3')Cd(1)N(2')
N(3)Cd(1)N(2)
N(3')Cd(1)N(2)
N(2')Cd(1)N(2)
N(3)Cd(1)N(1)
N(3')Cd(1)N(1)
110.79(7)
118.78(7)
78.00(7)
77.44(7)
123.58(7)
148.66(7)
146.52(7)
87.94(7)
N(2')Cd(1)N(1)
N(2)Cd(1)N(1)
N(3)Cd(1)N(1')
N(3')Cd(1)N(1')
N(2')Cd(1)N(1')
N(2)Cd(1)N(1')
N(1)Cd(1)N(1')
91.51(7)
69.09(6)
91.21(7)
146.74(7)
69.44(7)
84.47(6)
86.35(7)