Synthesis, characterization and solvatochromism investigation of mixed ligand chelate copper(II) complexes with acetyleacetonate and three diamine ligands

Article abstract of DOI:10.1002/cjoc.201200368

The syntheses of three mixed ligand chelate copper(II) complexes of the type [Cu(L)(acac)(H₂O)]BPh₄ where acac=acetyleacetonate; L=N,N-dimethyl,N′-benzylethane-1,2-diamine (L¹), N,N-dimethyl, N′-2-methylbenzylethane-1,2-diamine (L²) or N,N-dimethyl,N′-2-chlorobenzylethane-1,2-diamine (L³) are reported and characterized by elemental analyses, spectroscopic and molar conductance measurements. The X-ray structure of complex 1 shows that the central copper atom is placed in a distorted square pyramidal geometry made by acac and diamine chelate in the base and a H₂O molecule on the apex. The prepared complexes are fairly soluble in a large number of organic solvents and show positive solvatochromism. Calculations of SMLR (stepwise multiple linear regression) method was utilized to find the best model explaining the observed solvatochromic behavior and showed that among different solvent parameters, donor number (DN) is a dominant factor responsible for the shift in the d-d absorption band of the complexes to the lower wavenumber with increasing its values. The importance of substituent effect in diamine ligand on the spectral and SMLR measurements is also discussed.

Full text of DOI:10.1002/cjoc.201200368

FULL PAPER
DOI: 10.1002/cjoc.201200368
Synthesis, Characterization and Solvatochromism
Investigation of Mixed Ligand Chelate Copper(II) Complexes
with Acetyleacetonate and Three Diamine Ligands
,
a
a
a
Golchoubian, Hamid*
Afshar, Zahra Mohseni
Moayyedi, Golasa
b
b
Bruno, Giuseppe
Rudbari, Hadi Amiri
a
Department of Chemistry, University of Mazandaran, Babol-sar, Postal Code 47416-95447, Iran
Dipartimento di Chimica Inorganica, Vill. S. Agata, Salita Sperone 31, Università di Messina
b
9
8166 Messina, Italy
The syntheses of three mixed ligand chelate copper(II) complexes of the type [Cu(L)(acac)(H
2
O)]BPh
4
where
1
acac＝acetyleacetonate; L＝N,N-dimethyl,N'-benzylethane-1,2-diamine (L ), N,N-dimethyl, N'-2-methylbenzyle-
2
3
thane-1,2-diamine (L ) or N,N-dimethyl,N'-2-chlorobenzylethane-1,2-diamine (L ) are reported and characterized
by elemental analyses, spectroscopic and molar conductance measurements. The X-ray structure of complex 1
shows that the central copper atom is placed in a distorted square pyramidal geometry made by acac and diamine
chelate in the base and a H O molecule on the apex. The prepared complexes are fairly soluble in a large number of
2
organic solvents and show positive solvatochromism. Calculations of SMLR (stepwise multiple linear regression)
method was utilized to find the best model explaining the observed solvatochromic behavior and showed that
among different solvent parameters, donor number (DN) is a dominant factor responsible for the shift in the d-d ab-
sorption band of the complexes to the lower wavenumber with increasing its values. The importance of substituent
effect in diamine ligand on the spectral and SMLR measurements is also discussed.
Keywords mixed-chelate, solvatochromism, X-ray crystal structure, SMLR method, diamine, copper(II), tetra-
phenylborate
Introduction
spectral studies of several copper(II) mixed ligand che-
[
19-23]
late complexes.
Previous studies showed that
Synthesis of copper(II) mixed ligand chelate com-
plexes and investigating their solvatochromic behavior
have greatly helped for understanding the behavior of
solute in various solvents and solute-solvent interac-
among different counter ions used, copper(II) complexes
－
containing BPh4 exhibited better solvatochromism
[23,24]
behavior (larger Δνmax
)
because of its non-
coordinating property and disinclination in ion-pair
formation which led to less competition between solvent
molecules and the anion for coordination to metal center.
On the other hand, it was found that the nature of sub-
stituent group in the diamine ligand could also affect the
[
1,2]
tions.
Copper(II) complexes with a strong Jahn-
Teller effect show simple changes in electronic spectra
causing different colors that originate from the strength
of the interaction between solvent molecules which ap-
proach to the axial sites of the complexes. This property
[22]
spectra of these types of complexes. With use of this
[
3-5]
leads to using them as solvent polarity indicators
and
background, in the present work we study the synthesis
and solvatochromic behavior of three tetraphenylborate
mixed ligand chelate copper(II) complexes of the type
[
6,7]
many other practical applications such as imaging,
[
8,9]
[10]
photo switching
and sensor materials.
In this re-
gard, extensive studies have been focused for different
kinds of mixed ligand chelate copper(II) complexes with
general formula of [Cu(dike)(diam)]X
easily soluble in a large number of organic solvents and
show solvatochromic behavior. In such complexes dif-
ferent diketonate ions (dike), ethylenediamine deriva-
tives (diam) and various equivalent anions (X) were
used. We have also reported the synthesis and electronic
[
Cu(L)(acac)(H O)]BPh , as shown in Scheme 1, where
2 4
acac is acetylacetonate ion and L is ethylenediamine
derivatives. It was interesting to investigate how the
steric or electronic factors of the substituent groups
might affect the solvatochromic behavior of these types
of complexes. The solvatochromism studies of the com-
plexes were developed by application of the stepwise
multiple linear regression (SMLR) method. In this
[
11-18]
which are
*
E-mail: h.golchobian@umz.ac.ir; Tel./Fax: (+98)-1125342350
Received April 16, 2012; accepted May 21, 2012.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201200368 or from the author.
Chin. J. Chem. 2012, 30, 1873—1880 © 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Golchoubian et al.
FULL PAPER
method six solvatochromism-related parameters such as
dichloromethane (15 mL×3). The combined CH
2 2
Cl
[
1,25-27]
DN, AN, ET(30), α, β and π*
were employed to
fractions were dried over anhydrous Na SO . Evapora-
2
4
derive the best model to explain the positive solvato-
chromic behavior of these complexes.
tion of the solvent under reduced pressure resulted in
desired product as yellow oil. The yield was 45%. Se-
lected IR (KBr) ν: 3297 (m, NH str.), 2817 (s, CH str.
Scheme 1 The complexes under study
aliphatic), 1459 (s, C＝C str. aromatic), 1043 (s, NCH
3
－
1 1
3
str. aliphatic) cm . H NMR (400 MHz, CDCl ) δ: 2.24
(
s, 6H, CH NCH ), 2.36 (s, 3H, CH Ph), 2.51 (t, J＝
3
3
3
1
2.4 Hz, 2H, CH
2
2 3 2
CH N(CH ) ), 2.79 (t, J＝12.4 Hz, 2H,
H O
2
X
NH
N
O
NHCH CH ), 3.82 (s, 2H, PhCH NH), 7.17—7.21 (m,
2 2 2
BPh4
13
Cu
4
H, arylH); C NMR (126.77 MHz in CDCl ) δ: 45.4
3
O
(
3 3 2 2 3 2 2
CH NCH ), 58.6 [CH CH N(CH ) ] 46.5 (NHCH -
Me Me
CH ), 19 (CH Ph), 51.3 (PhCH NH), 126.0, 127.1,
2
3
2
X = H, CH , Cl
128.6, 130.3, 136.3 (arylC).
N,N-Dimethyl,N'-2-chlorobenzylethane-1,2-di-
3
3
2
amine (L ) The same procedure as L was used for
Experimental
3
the preparation of ligand L , except that using
2
-chlorobenzaldehyde instead of 2-methyl benzaldehyde.
Materials and methods
The yield was 55%. Selected IR (KBr) ν: 3309 (m, NH
str.), 2817 (s, CH str. aliphatic), 1448 (s, C＝C str. aro-
matic), 1043 (s, NCH str. aliphatic). H NMR (400
MHz, CDCl ) δ: 2.17 (s, 6H, CH NCH ), 2.41 [t, J＝
1
The ligand L , N,N-dimethyl,N'-benzylethane-1,2-
diamine and complex 1 were prepared according to pub-
1
[20,24]
3
lished procedures,
respectively. All solvents were
3
3
3
spectro-grade and used without further purification. All
the samples were dried to constant weight under a high
vacuum prior to analysis. Conductivity measurements
were made at 25 ℃ with a Jenway 400 conductance
1
2 2 3 2
2.0 Hz, 2H, CH CH N(CH ) ], 2.67 (t, J＝12.0 Hz, 2H,
NHCH CH ), 3.87 (s, 2H, PhCH NH), 7.13—7.38 (m,
4
2
2
2
13
H, arylH); C NMR (126.77 MHz in CDCl ) δ: 45.4
3
(
3 3 2 2 3 2 2
CH NCH ), 59.0 [CH CH N(CH ) ], 46.5 (NHCH -
－
3
meter on 1.00×10 mol/L samples in selected solvents.
Infrared spectra were recorded in KBr disks by a Bruker
FT-IR instrument. The electronic absorption spectra
were measured with a Braic2100 model UV-Vis spectro-
CH ), 51.3 (PhCH NH), 126.7, 128.2, 129.4, 130.1,
1
2
2
33.7, 137.6 (arylC).
2
[
Cu(L )(acac)(H
N,N-dimethyl,N'-2-methylbenzylethane-1,2-diamine, L
1.2 g, 6 mmol), acetylacetone (0.7 mL, 6 mmol) and
anhydrous Na CO (0.3 g, 3 mmol) in ethanol (30 mL),
2
O)]BPh
4
(2)
A mixture of
2
1
13
photometer using 1 cm quartz cells. H NMR and
C
(
NMR spectra for ligands were recorded on a Bruker 400
MHz Ultrashield avance III Spectrometer. Elemental
analyses were performed on a LECO 600 CHN elemen-
tal analyzer. The solvents used for the solvatochromic
study are dichloromethane (DCM), nitromethane (NM),
nitrobenzene (NB), benzonitrile (BN), acetonitrile (AN),
propionitrile (PN), acetone (Ac), tetrahydrofuran (THF),
ethanol (EtOH), methanol (MeOH), dimethylformamide
2
3
was added to an aqueous solution of Cu(OAc) •H O
2
2
(
[
1.2 g, 6 mmol). After removing the by-product of
Cu(acac) ], a saturated solution of NaBPh in ethanol
2
4
was added to the resultant clear blue solution. The dark
blue precipitate was gradually formed which was sepa-
rated by filtration. The blue solid was recrystallized
from acetonitrile. The yield was 48%. Selected IR (KBr)
ν: 3527 (m, OH str.), 3288 (m, NH str), 1585 (s, C＝O
str.), 1519 (s, C＝C str.), 738, 705 (s, CH bend.). Anal.
(DMF), dimethylsulfoxide (DMSO), pyridine (Py) and
hexamethylphosphorictriamide (HMPA).
2 3
calcd for C41H49BCuN O : C 71.14, H 7.14, N 4.05;
Synthesis
found C 71.60, H 6.83, N 3.88.
N,N-Dimethyl,N'-2-methylbenzylethane-1,2-
diamine (L ) A mixture of 2-methyl benzaldehyde (30
mmol), N,N-dimethylethylenediamine (30 mmol ) and a
few drops of acetic acid in ethanol (15 mL) was prepared
and refluxed for 10 min. The solvent was then evapo-
3
2
Preparation of [Cu(L )(acac)(H
2
O)]BPh
4
(3)
This compound was prepared according to the procedure
used for 2 except that N,N-dimethyl,N'-2-chloro-
benzylethane-1,2-diamine was used instead of N,N-
dimethyl,N'-benzylethane-1,2-diamine as diamine ligand.
A dark blue precipitation was obtained, recrystallized
from acetonitrile and dried at room temperature under
high vacuum. The yield was 40%. Selected IR (KBr) ν:
rated under reduced pressure. NaBH (45 mmol) was
4
added gradually to the resultant yellow oil that was dis-
solved in ethanol (30 mL). The resulting mixture was
allowed to stand overnight. After heating the solution
near the boiling point, HCl (10 mL, 17 mol/L) was
added to it while placing the solution in an ice bath and
was heated again to the boiling temperature. The mix-
ture was then made alkaline by NaOH (4 mol/L). The
sodium borate precipitate was removed by filtration.
The evaporation of the solvent from the filtrate resulted
in a yellow oil which was subsequently extracted with
3
1
588 (m, OH str.), 3274 (m, NH str), 1585 (s, C＝O str.),
519 (s, C＝C str.), 738, 705 (s, CH bend.). Anal. calcd
for C H BClCuN O : C 67.42, H 6.51, N 3.93; found
4
0
46
2
3
C 67.81, H 6.12, N 4.14.
X-ray structure determination
Data were collected at room temperature with a
Bruker APEX II CCD area-detector diffractometer using
1874
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Chin. J. Chem. 2012, 30, 1873—1880

Synthesis, Characterization and Solvatochromism Investigation of Copper(II) Complexes
MoKα radiation (λ＝0.71073 Å). Data collection, cell
refinement, data reduction and absorption correction
were performed using multiscan methods with Bruker
SMLR analysis
In this report a multiple linear regression (MLR)
analysis was performed by SPSS/PC software (SPSS ver.
[28-30]
software.
The structures were solved by direct
16, SPSS Inc.) by using stepwise method for model
[
31]
[33]
methods using SIR2004.
building.
Stepwise-MLR is a popular technique that
The non-hydrogen atoms were refined anisotropically
has been used to select the most appropriate parameters
in solvent-solute interaction. After passing three main
2
[34]
by the full matrix least squares method on F using
[
32]
SHELXL. All the hydrogen (H) atoms were placed at
the calculated positions and constrained to ride on their
parent atoms. Details concerning collection and analysis
are reported in Table 1.
steps of SMLR method, identifying an initial model,
changing the model of previous step by adding or re-
moving a parameter and obtaining the best model at the
final step, the goodness of model can be analyzed by
considering closeness of the R (multiple correlation co-
efficients) value to one and high F-statistic values, low
standard errors (S.E), the least number of parameters
Table 1 Crystal data and structure refinement of complex 1
[
35]
Empirical formula
C
40
H
47BCuN
2
O
3
and high ability for prediction.
Formula weight
678.15
Results and Discussion
Color
Blue
Temperature/K
296(2)
To prepare the mixed ligand chelate complexes,
Wavelength/Å
0.71073
Monoclinic
Cu(OAc) •H O, acac, the diamines and NaCO with
molar ratios of 1∶1∶1∶0.5, respectively were mixed
in the solvent of ethanol. After removing the by-product
2
2
3
Crystal system
Space group
P2 /c
1
of [Cu(acac) ] from the dark mixture and addition of an
2
Crystal size/mm
0.86×0.45×0.23
ethanolic saturated solution of NaBPh to the clear re-
4
Unit cell dimensions
sultant solution, the desired complexes were obtained as
dark blue crystals with typical yield of 40%—60%.
Analytical data, molar conductivity, IR spectra and
X-ray crystallography indicated formation of the desired
mixed ligand chelate copper(II) complexes.
a/Å
b/Å
c/Å
α
9.678
31.586
12.755
90º
X-ray structure
β
103.349(4)°
90º
An ORTEP view of the cationic part of complex 1 is
depicted in Figure 1 together with the numbering
scheme. Selected bond distances and angles are pre-
sented in Table 2.
γ
3
Volume/Å
3794.1
4
Z
－
Calculated density/(Mg•m ) 1.184
3
－
1
Absorption coefficient/mm
0.613
1436
F(000)
θ range for data collection/(°) 2.09—30.10
13≤h≤13
－44≤k≤44
17≤l≤17
－
Index ranges
－
－
1
μ/mm
1.187
Reflections collected/unique
Completeness to θ＝30.10
Absorption correction
159628/11101 [R(int)＝0.0567]
99.5%
Multi-scan
1
＋
a
2
Figure 1 ORTEP view of [Cu(acac)(L )(H
2
O)] (1). Non
Refinement method
Full-matrix least-square on F
H-atoms represented as displacement ellipsoids are plotted at the
0% probability level, while H atoms are shown as small spheres
Data/restraints/parameters
11101/0/451
3
a
b
Final R indices [I＞2σ(I)]
R
1
＝0.0711, wR
1.112
2
＝0.1256, wR ＝0.1813
2
＝0.1600
of arbitrary radius.
2
c
Goodness-of-fit on F
R indices (all data)
The compound crystallizes in the monoclinic space
group P2 /c. The geometry about the copper can be re-
garded as a distorted square-pyramid with the N O do-
nor atoms of diamine and acetylacetonate chelates on
the base and water oxygen at the apex. The geometric
R
1
1
Largest diff. peak and hole/
0
.504 and －0.381
2 2
－
e•Å )
3
(
a
b
2
2 2
2 2 1/2
o c o o c o
R＝(∑||F |－|F ||)/∑|F |; wR＝[∑(F －F ) ]/∑[w(F ) ] ;
S＝∑[w(F
c
2
2 2
c
1/2
[
36]
o
－F
) /(Nobs－Nparam)]
.
discrimination parameter τ
between squarepyramid
Chin. J. Chem. 2012, 30, 1873—1880
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1875

Golchoubian et al.
FULL PAPER
Table 2 Selected bond distances (Å) and angles (°) for complex
1
axis stabilize the crystal packing. Also the crystal pack-
ing shows two-dimensional sheet with zigzag structures
along crystallographic b axis as shown in Figure 2.
Bond distance/Å
Bond angle/(°)
O(1)-Cu-O(2)
Cu—O(1)
1.905(2)
1.924(3)
2.047(3)
2.011(3)
2.391(3)
93.84(12)
169.78(14)
89.57(12)
89.85(11)
172.40(11)
85.71(12)
IR spectra
Cu—O(2)
Cu—N(1)
Cu—N(2)
Cu—O(3)
O(1)-Cu-N(2)
O(2)-Cu-N(2)
O(1)-Cu-N(1)
O(2)-Cu-N(1)
N(2)-Cu-N(1)
The IR spectra of Schiff-base imines show a sharp
－
1
and strong band around 1640 cm due to C＝N stretch-
[37,38]
ing vibration.
Disappearing of these bands in IR
spectra of diamine ligands along with emergence of the
－
1
N—H stretching vibrations at 3300 cm , indicates re-
duction of the C＝N bond and formation of the desired
ligands. Other characteristic bands in the spectra of dia-
(τ＝0) and trigonal-bipyramid (τ＝1) is 0.04. The cop-
－1
－1
mines, are observed at 1040 cm and 1450 cm that
per(II) ion is displaced by 0.135(4) Å from the basal
least square plane toward the water oxygen atom.
Such a coordination has been observed previously in a
can be assigned to the vibrations of the C—N bond and
[39]
2
CH phenyl groups, respectively. Upon coordination
[
23]
of diamine ligand to the copper(II) center and formation
of the mixed ligand chelate complexes, the N—H bond
of the free diamines shifts to the lower wavenumber in
comparison to the free ligand. As the lone pair of elec-
trons of the donor nitrogen atoms become involved in
the metal-ligand bond, the transfer of electron density to
the metal and the subsequent polarization of the ligand
involves electron depopulation of the N—H bond,
which culminates in a shift to lower frequencies. The
presence of acetylacetonate (acac) ligand in the com-
plexes is confirmed by two intense and sharp bands
Cu(II) complex including Cl-acac as dike ligand. The
basal Cu—O(1) and Cu—O(2) distances are 1.905(2) Å
and 1.924(3) Å, respectively with a bite angle of
O(1)-Cu-O(2) 93.84(12)°. The mean Cu—N distance of
the diamine ligand and the bite angle N(1)-Cu-N(2) are
2
.029 Å and 85.71°, respectively and close to the related
[22,23]
values of the analogous copper(II) complexes.
The
axial Cu—O(3) (water) bond is elongated [2.391(3) Å]
9
owing to Jahn-Teller effect for d electronic configura-
tion. As a result, the water molecule is weakly coordi-
nated to the copper(II) center and can be easily replaced
by solvent molecules in solution leading to the observed
solvatochromism. The asymmetric nitrogen N(2) has a
configuration of R in the Figure 1; the benzyl substituent
on the amine nitrogen and water molecule are situated
cis to each other and are axially oriented with respect to
mean molecular plane (N O ). The packing of the struc-
－
1
around 1520 and 1580 cm that can be assigned to the
[40-42]
C＝C and C＝O vibrational modes, respectively.
The absorption－ band occurring in the region
1
1
525—1585 cm in IR spectra of all the mixed ligand
chelate complexes is associated with coordination of
water molecule to the axial position of copper(II) ion
which is confirmed by X-ray crystallography. The two
2
2
ture in the unit cell is shown in Figure 2. This arrange-
ment shows that tetaphenylborate, as the counter ion,
has no any interaction with copper(II) center probably
due to non-coordinative ability and its large size and is
located far-off from this center. However, inter molecu-
lar interactions between the ligand moieties of the cation
and tetraphenylborate anions along crystallographic c
－
1
intense absorption bands at 705 and 735 cm observed
in all complexes correspond to tetraphenylborate ion
[43]
which exists as counter ion.
The difference in sub-
stituent of diamine ligands can be observed in spectra of
3
6
, in this case a moderate band that appears at around
－
1
00 cm [ is probably due to the C—Cl bond stretching
44]
vibration that is absent in spectra of 1 and 2.
Conductometric data
The molar conductances of three mixed ligand che-
late complexes in some organic solvents with different
polarities are presented in Table 3. The standard values
for 1∶1 electrolyte for solvents are given in the same
[45]
table. It can be observed that the values in all solvents
are lower than the expected values. These results arise
from the nature of counter ion in mixed ligand chelate
complexes; tetraphenylborate is a bulky ion so that its
[
45]
ionic mobility in the solution is low.
Solvatochromism
The prepared mixed ligand chelate complexes are
soluble in a large number of organic solvents. The posi-
tion of the νmax values of the complexes with the molar
absorptivities and their respective solvent parameter
values are collected in Table 4. As shown in Figure 3 the
1
Figure 2 Crystal packing of [Cu(acac)(L )(H O)]BPh . For
clarity, H atoms have been omitted.
2
4
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Chin. J. Chem. 2012, 30, 1873—1880

Synthesis, Characterization and Solvatochromism Investigation of Copper(II) Complexes
－
) of the complexes (Ω •
cm •mol ) at 25 ℃ in different solvents.
1
Table 3 Molar conductivities data (Λ
m
2
－1
Complex
NM
52
NB
17
16
15
AC
84
60
53
ACN
93
MeOH
54
a
1
2
3
51
88
58
39
85
63
1
∶1 electrolytes 75—95 20—30 100—140 120—160 80—115
a
Taken from reference 24.
absorption spectra of the complexes exhibit a broad
－
1
structureless band in the range of 11000—25000 cm
that is attributed to the promotion of an electron from
2
2
lower orbitals to the hole of d
ion (d ).
－y
orbital of copper(II)
x
9
In order to ascertain presence of a trend for the ob-
served solvatochromism behavior of the complexes,
solvatochromism parameters containing DN (negative
ΔH value for a 1∶1 adduct formation between SbCl
5
and solvent molecules in a dilute solution of 1,2-
dichloroethane or dichloromethane), AN (derived from
3
1
P NMR of triethylphosphine oxide in different sol-
vents), E (30) (molar electronic transition energy of
T
dissolved negatively solvatochromic pyridinium N-phe-
nolate betaine dye), α [solvatochromic parameter of a
solvent’s HBD (hydrogen-bond donor) acidity], β [sol-
vatochromic parameter of solvent’s HBA (hydrogen-
bond acceptor) basicity] and π* (solvatochromic pa-
rameter index of a solvent’s polarity/polarizability,
which measures the ability of the solvent to stabilize a
charge or a dipole by virtue of its dielectric effect) were
used to generate the best model with using SMLR
method. The choice of parameters is crucial in order to
Figure 3 Absorption spectra of complexes 1—3 in selected
solvents. Absorption spectra in other solvents are omitted for
clarity.
[46]
set up a reasonable model. To reach our aim we used
these parameters along with the absorption frequencies
plexes. The R values near unity and also high F-statis-
tics values prove existence of an appropriate inter corre-
lation between DN parameters and wavenumbers.
Cross validation is a well-known technique to esti-
(
νmax) of the complexes to the solvatochromism Eq. (1).
The νmax values were obtained experimentally by visible
spectroscopy. The parameter values were taken directly
from literature
[
47-49]
[52]
which are collected in Table 4.
mate the reliability of a statistical model. In this re-
These parameters are independent to each other, but
port the cross validation technique was utilized to de-
termine the accuracy of the proposed SMLR model.
Based on this technique, the most popular cross-
validation procedure LOO (leave one-out) technique
[
50,51]
relevant to the case under study.
max＝ν˚max＋þaDN＋þbAN＋cE
fπ*
ν
T
(30)＋dβ＋eα＋
[53]
(1)
was used. The predictive abilities of the models were
2
determined by the cross validation coefficient (Q )
In this equation νmax is the value of the absorption
energy in the solvent under study and ν˚max is the value
of the absorption energy in an inert solvent. DN, AN,
which is based on PRESS (predicted residual sum of
2
squares), PRESS＝Σ(Ypred.－Yexp.) and SSY (total sum
2
of squares derivations), SSY＝Σ(Yexp.－Ymaen) , and can
T
E (30), β, α and π* represent independent but comple-
be calculated by Eq. 2.
mentary solvent parameters. The a, b, c, d, e and f val-
ues are the regression coefficients describing the sensi-
tivity of the property νmax to the different solute/solvent
interaction mechanisms. The SMLR results were col-
lected in Table 5.
According to observed results the dominant parame-
ter responsible for solvatochromism behavior of the
complexes is DN; so that the higher DN value the more
shift to the lower wavenumber in the spectra of the com-
2
Q ＝1－PRESS/SSY
(2)
where Ypred.; the predicted wavenumbers of the solvents
by the best SMLR model, Yexp.; the experimental meas-
ured wavenumbers, Ymaen; mean values of the predicted
2
wavenumbers. Using this model showed that the Q pa-
rameters of the complexes are in an acceptable range
2
(Q ＞0.5), and also the PRESS values are much less
Chin. J. Chem. 2012, 30, 1873—1880
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
1877

Golchoubian et al.
FULL PAPER
3
－1
－1
－1
Table 4 The solvent parameter values and electronic spectra of the complex in various solvents: νmax/(10 cm ) [ε/(L•mol •cm )]
b
Solvent
DCM
NM
DN
0.0
AN
20.4
20.5
14.8
15.5
18.9
16.0
12.5
8.0
E
T
(30)
β
α
π*
Complex 1
18.71 (107)
18.26 (107)
17.82 (103)
17.36 (105)
17.17 (119)
17.30 (120)
17.31 (103)
17.19 (110)
16.99 (106)
16.80 (112)
16.45 (105)
16.09 (115)
15.57 (110)
15.38 (117)
Complex 2
18.76 (95)
17.83 (90)
18.08 (136)
17.33 (88)
17.12 (92)
16.98 (74)
17.15 (80)
16.95 (90)
16.72 (80)
16.81 (94)
16.39 (100)
16.21 (106)
15.50 (98)
15.38 (104)
Complex 3
18.52 (95)
18.05 (122)
18.02 (102)
17.06 (100)
17.01 (110)
17.18 (96)
17.01 (90)
17.01 (104)
16.69 (71)
16.89 (106)
16.23 (102)
16.13 (100)
15.29 (96)
15.53 (105)
40.7
46.3
41.5
41.5
45.6
43.6
42.2
37.4
51.9
55.4
43.8
45.1
40.5
40.9
0.10
0.06
0.30
0.37
0.40
0.39
0.43
0.55
0.75
0.66
0.69
0.76
0.64
1.05
0.13
0.22
0.00
0.00
0.19
0.00
0.08
0.00
0.86
0.98
0.00
0.00
0.00
0.00
0.82
0.85
1.01
0.90
0.75
0.71
0.71
0.58
0.54
0.60
0.88
1.00
0.87
0.87
2.7
NB
4.4
BN
11.9
14.1
16.1
17.0
20.0
22.9
23.3
26.6
29.8
33.1
38.8
AN
PN
Ac
THF
EtOH
MeOH
DMF
DMSO
Py
37.1
41.3
16.0
19.3
14.2
HMPA
10.6
a
b
－3
Taken from reference [24]. The spectrum taken at 0 ℃ at concentration of 1.00×10 mol/L.
a
Table 5 The equations resulting from the linear correlation of the νmax values with the DN of the solvents
－
1
Complex
Equation
F
R
S.E.
Δνmax/cm
3
ν
max/10 ＝－0.079DNsolv＋18.502
1
231.17
0.97
0.21 3326
0.21 3380
0.24 3230
DNsolv＝－11.997νmax＋222.91
3
ν
max/10 ＝－0.078DNsolv＋18.395
2
3
231.314
173.490
0.975
0.967
DNsolv＝－10.967νmax＋205.21
3
ν
max/10 ＝－0.077DNsolv＋18.333
DNsolv＝－12.166νmax＋224.24
a
The number of variables, n＝14.
2
than SSY, indicating the models predict better than
chance and are considered statistically important. In this
case, PRESS/SSY ranges between 0.049 and 0.089, in-
dicating the DN parameter plays the most important role
in solvatochromism behavior of the complexes. The ob-
tained νmax values versus the predicted νmax values were
plotted by using Eq. 1 to confirm our findings. The re-
sults are shown in Table 6.
These results revealed that in all complexes the
slopes are near unity (Table 6) with good correlation
coefficient. Considering the DN parameter of different
solvents the complexes show a color change from violet
via blue to green as the polarity of solvent increases
from DCM (DN＝0) to HMPA (DN＝38.8). This ob-
servation demonstrates the donor-acceptor interactions
between Cu(II) ion and solvent molecules are responsi-
ble in solvatochromic behavior of the complexes. This is
Table 6 The quality of the obtained models by means of Q ,
PRESS and PRESS/SSY and predictive correlation coefficient
a
(Rpre
)
2
Complex
Q
PRESS
0.56
PRESS/SSY
0.049
0
.95
1
νmax experimental＝1.004νmax predicted－0.077
Rpre＝0.975
0
.94
0.65
0.058
2
ν
max experimental＝1.0203νmax predicted－0.337
Rpre＝0.9698
0
.91
0.98
0.089
3
ν
max experimental＝0.9865νmax predicted－0.2282
Rpre＝0.9544
a
The number of variables, n＝14.
as a result of the weak axial bond of H O molecule to
levels of these orbitals become closer to each other and
therefore, the required energy for electron transition is
lowered and a red shift is observed. The results demon-
strate that all complexes are solvatochromic and show
2
the copper(II) center that can be easily replaced by sol-
vent molecules and also occupation of another vacant
axial site by solvent molecule which results in change in
2
2
2
the energy gap between d and d
－y
orbitals. As shown
larger Δνmax＝(ν
)
－(ν
max HMPA
values in com-
)
z
x
max DCM
[24]
in Figure 4 the νmax values decrease nearly linear with
the increasing DN of solvents. Increasing Lewis basicity
of solvents causes more interaction between solvent
molecules and the copper center. As a result, the energy
parison with the analogous perchlorate complexes.
This difference is associated with the fact that tetra-
phenylborate is a large, bulky anion in comparison with
－
－
－
[23,24]
ClO , PF and BF4 anions
with lack of coor-
4
6
1878
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© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2012, 30, 1873—1880

Synthesis, Characterization and Solvatochromism Investigation of Copper(II) Complexes
dinating ability. Thus the solvent molecules can ap-
proach more easily to the axial sites of the complexes.
This phenomenon causes the higher Δνmax values. It was
also expected that the steric or electronic factors might
affect the shift in the d-d band of the copper(II)
Supplementary Data
CCDC 851370 for 1 contains the supplementary
crystallographic data. These data can be obtained free of
charge from The Cambridge Crystallographic Data Cen-
tre via http://www.ccdc.cam.ac.uk/data_request/cif.
[19,22]
mixed-chelate complexes,
but as shown in Figure 4
the spectra of compounds 1—3 with different substitu-
ents on the phenyl ring of diamine ligand were nearly
similar to each other. This might suggest that varying
the substituent attached to the phenyl ring could not in-
fluence the ligand field strength around copper(II) center
so no direct correlation between the presence of elec-
tron-withdrawing or electron-releasing groups was ob-
served. This could be due to the far-off distance of sub-
stituent groups from the coordination center. This inter-
pretation is confirmed with regard to X-ray crystallog-
raphy, so that the solvatochronism behaviors of the
mentioned complexes were independent to the nature of
the substituent groups on the phenyl ring of the diamine
ligand.
Acknowledgement
We are grateful for the financial support of Univer-
sity of Mazandaran of the Islamic Republic of Iran.
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