Molecular structure and linkage isomerization in copper(II) complexes containing N,N-dialkyl-N'-benzylethylenediamine and thiocyanate ligands: A combined crystallographic, spectroscopic and DFT study

Article abstract of DOI:10.1007/s11243-014-9805-1

A combined experimental and computational study of three thiocyanate-Cu(II) complexes with general formula [Cu(L ⁿ )₂(NCS)]ClO ₄, (L¹ = N,N-dimethyl,N'-benzyl-ethylenediamine, L ² = N,N-diethylyl,N'-b

Full text of DOI:10.1007/s11243-014-9805-1

Transition Met Chem
DOI 10.1007/s11243-014-9805-1
Molecular structure and linkage isomerization in copper(II)
complexes containing N,N-dialkyl-N0-benzylethylenediamine
and thiocyanate ligands: a combined crystallographic,
spectroscopic and DFT study
•
Hamid Golchoubian Sara Koohzad
Received: 8 December 2013 / Accepted: 6 February 2014
Ó Springer International Publishing Switzerland 2014
Abstract A combined experimental and computational study
of three thiocyanate-Cu(II) complexes with general formula
[Cu(Ln)2(NCS)]ClO4, (L1 = N,N-dimethyl,N0-benzyl-ethy-
lenediamine, L2 = N,N-diethylyl,N0-benzyl-ethylenediamine,
L3 = N,N-diisopropylyl,N0-benzyl-ethylenediamine) was car-
ried out. The compounds were synthesized and structurally
characterized by physico-chemical and spectroscopic methods.
X-ray crystallography of [Cu(L1)2(NCS)]ClO4 showed that the
copper atom achieves a distorted square pyramidal environment
through coordination of four amine N atoms and a N atom of the
terminal SCN- ion. To investigate the effect of steric crowding
on the coordination mode of thiocyanate at the copper(II)center,
DFT calculations are carried out on the complexes. Two dif-
ferentcaseswere considered, namely when nitrogen isthedonor
atom and when sulfur is the donor atom. In all cases, the
N-coordinated isomers were always more stable than the
S-coordinated ones. The electronic spectra of the complexes
were analyzed and assigned by means of DFT/TD-DFT, toge-
ther with molecular orbital analysis.
due to the diversity of the resulting complexes. When
thiocyanate ion is the only ligand present in a complex, its
mode of bonding generally follows the hard (M-NCS) or soft
(M-SCN) pattern. However, the steric and electronic prop-
erties of the co-ligands can play a crucial role in controlling
the coordination mode of thiocyanate. Several studies on the
linkage isomerism of thiocyanate and isothiocyanate have
been conducted for the third row (Pt(II) [1, 2], Re(V) [3, 4]
Re(IV) [5]), second row (Ru(III) [6], Pd(II) [7]) and first row
(Cu(II) [8], Co(III) [9] ) transition metals. Steric control of the
thiocyanate binding mode was first described in 1964 [10]. It
was demonstrated that [Pd(diethylenetriamine)(NCS)]? gives
the stable S-bonded complex, whereas the N-bonded form is
more stable with tetraethyldiethylenetriamine. An investiga-
tion of the effects of steric hindrance in [Pd(diamine)(NCS)2]
and [Pd(diamine)2](NCS)2 complexes demonstrated that
increase in steric hindrance created by the diamines tends to
promote N-bonding of the thiocyanate [11]. The combined
influence of electronic and steric factors upon thiocyanate
linkage isomerism has been investigated for bidentate ligands
[12] that have one r-donor functionality (e.g., amines) and
one p-bonding functionality (e.g., phosphines), where the
S-bonded thiocyanate is trans to amine and the N-bonded
isomer is trans to phosphine.
Introduction
The coordination chemistry of ambidentate ligands, espe-
cially thiocyanate which can coordinate via the sulfur or
nitrogen atom or both, has received considerable interest
Recently, quantum mechanical calculations have become
an important tool for prediction of the relative energies,
structures and vibrational spectra of fairly large molecules. It
has been already shown on many occasions that the results
obtained from hybrid DFT functional such as B3LYP are in
good agreement with experimental values. Furthermore, the
computational cost for this method is less than that of high-
level ab initio calculations [13].
Electronic supplementary material The online version of this
article (doi:10.1007/s11243-014-9805-1) contains supplementary
material, which is available to authorized users.
H. Golchoubian (&) ꢀ S. Koohzad
Department of Chemistry, University of Mazandaran,
47416-95447 Babolsar, Iran
We recently investigated the electronic structures of cop-
per(II) complexes with general formula [Cu(Ln)2(NCX)]ClO4,
where L = N,N-dimethyl,N’-benzyl-1,2-diaminoethane and
e-mail: h.golchobian@umz.ac.ir
123

Transition Met Chem
X = O, S or Se, and the relative stabilities of the Cu-NCX/Cu-
XCN linkage isomers [14]. It was shown that there is a close
agreement between experimental and theoretical results
obtained with the DFT/B3LYP functional.
The main objective of the present study was to evaluate
the characteristics of the nitrogen and sulfur donor atoms in
the stability of thiocyanate complexes with increasing
steric hindrance around the copper center. We have con-
sidered the three complexes shown in Fig. 1. In these
complexes, the alkyl moiety of the diamine ligand is varied
between methyl, ethyl and isopropyl. To obtain detailed
insight into the electronic structure and spectroscopic
properties of these complexes, DFT and time-dependent
DFT (TD-DFT) calculations were performed.
Fig. 2 Experimental (black) and calculated (red) IR spectra of the
complex 3
Results and discussion
The diamine ligands were prepared by condensation of equi-
molar amounts of N,N-dimethyl-1,2-diaminoethane and
benzaldehyde and reduction of the resulting imines with
sodium borohydride. The complexes were synthesized by
mixing the diamine, Cu(ClO4)2ꢀ6H2O and KSCN in molar
ratios of 2:1:1, in ethanol as solvent. The IR spectra of the
complexesclearlyshowthepresenceofthethiocyanategroup.
The maxima mCN occur as strong bands at 2,075 cm-1 for 1,
2,084 cm-1 for 2 and 2,085 cm-1 for 3. These bands are
consistent with terminal coordination of thiocyanate through
the nitrogen atom [15]. The presence of ClO4- group is con-
with the N–H vibration and is observed as a broad feature at
around 3,350 cm-1 in the spectra of the free diamine ligands.
The calculated (non-scaled) vibrational spectra of all
these complexes are in good agreement with the experi-
mental data as shown in Fig. 2 (Table S1-S3 and Fig S3 in
the supplementary content). The calculated mCN vibration
of the thiocyanate ligand occurs at 2,060 cm-1 in 1,
2,064 cm-1 in 2 and 2,065 cm-1 in 3; these values are
lower than experimental ones by *1 %, which is a usual
feature of this approach [17]. Similarly, the calculated
absorption band due to the mN–H modes of the complexes
appears at 3,475–3,440 cm-1, deviating from the experi-
mental rang by *5 %.
The molar conductivity values of the complexes in
selected organic solvents have been studied, and the results,
along with the standard values for 1:1 electrolytes in the
respective solvents [18], are gathered in Table S4 (in the
supplementary content). The solution conductivity values of
the complexes are in good agreement with those expected for
1:1 electrolytes. As a result, the perchlorate ion is free from
coordination in solution.
firmed by two intense bands at around 1,100 and 622 cm-1
,
which are attributed to the antisymmetric stretching and
antisymmetric bending vibration modes, respectively [16].
Coordination of the diamine ligand is confirmed by an intense
and narrow band at 3,200 10 cm-1, which is associated
X-ray crystal structure
The structure of [Cu(L1)2(NCS)]ClO4, 1 is shown in Fig. 3,
and selected bond distances and angles are gathered in
Table 1.
The cationic complex is comprised of two diamine ligand
a SCN- anion and one Cu(II) center. The perchlorate ion is
free from coordination. This complex has a distorted square
pyramidal structure, in which the Cu(II) is coordinated by
four nitrogen atoms of chelating diamine ligands and one
nitrogen atom of a SCN ligand. The trigonality index (s) was
calculated with the help of the definition s = (a-b)/60 [19],
Fig. 1 The complexes used in this study
123

Transition Met Chem
Fig. 3 ORTEP view of the
complex 1
˚
Table 1 The selected experimental and optimized bond lengths (A) and angles (°) for 1
Bond length
Bond angle
Experimental
Cu–NCS
Cu–SCN
Experimental
Cu–NCS
Cu–SCN
N(1)–Cu(1)
S(1)–Cu(1)
N(3)–Cu(1)
N(2)–Cu(1)
N(5)–Cu(1)
N(4)–Cu(1)
C(1)–N(1)
C(1)–S(1)
1.969 (3)
–
1.984
–
–
N(1)–Cu(1)–N(5)
N(1)–Cu(1)–N(2)
N(1)–Cu(1)–N(3)
N(1)–Cu(1)–N(4)
N(4)–Cu(1)–N(5)
N(4)–Cu(1)–N(2)
N(2)–Cu(1)–N(5)
N(3)–Cu(1)–N(4)
C(1)–N(1)–Cu(1)
C(1)–S(1)–Cu(1)
89.90 (15)
90.12 (14)
172.89 (14)
95.35 (14)
83.42 (11)
103.66 (13)
157.99 (14)
106.64 (11)
167.9 (4)
–
87.6
90.1
166.4
97.9
80.8
110.9
168.29
95.5
150.1
–
–
2.494
2.235
2.160
2.124
2.414
1.182
1.729
–
2.113 (3)
2.063 (3)
2.062 (3)
2.329 (3)
1.133 (5)
1.603 (4)
2.150
2.160
2.128
2.489
1.201
1.661
–
–
81.8
110.5
166.39
70.0
–
109.2
where a and b are the largest and second largest angles,
respectively, between the central metal atom and its sur-
rounding donor atoms. The s values are zero for a regular
square pyramidal geometry and unity for a regular trigonal
bipyramidal one. The N(2)–Cu(1)–N(5) and N(1)–Cu(1)–
N(3) angles in the basal plane of the complex are 157.99(14)°
(a) and 172.89(14)° (b), respectively. Thus, the s value of
0.25 confirms a distorted square pyramidal structure. The
apical nitrogen atom N(4). The Cu–N bond lengths in the
basal plane are in the ranges observed for the other com-
plexes [14, 20, 21]. The NCS group of the complex is
almost linear, i.e., the N–C–S angle is 177.9(4)°. Both N–C
and C–S bonds should have a multiple-bond character to a
certain extent. The slight bending can be explained simply in
terms of packing requirements and steric influence [22–24].
It can be expected that the bond distances of N–C and C–S
and the bond angles of Cu–N–C are interrelated by hybrid-
ization between forms (I) and (II) in the copper thiocyanate
˚
copper(II) center is displaced 0.253(5) A from the basal
plane [constituted by N(1), N(2), N(3) and N(5)] toward the
123

Transition Met Chem
Table 3 Results of natural population analysis for Cu–NCX and Cu–
XCN isomers
Cu
N
C
S
NCS
Cu–N
Complex 1
Scheme 1 Resonance structures of Cu–NCS bond
0.981
1.014
1.040
-0.687
-0.697
-0.732
0.106
0.110
0.108
-0.115
-0.125
-0.107
-0.696
-0.712
-0.731
Complex 2
Complex 3
Cu–S
Table 2 Differences between total molecular energies (DEN-S
,
kJ mol-1) for N–Cu/and S–Cu bonded isomers of the complexes
Complex 1
Complex 2
Complex 3
0.855
0.896
0.843
-0.332
-0.332
-0.340
0.033
0.037
0.033
-0.227
-0.247
-0.255
-0.526
-0.542
-0.562
Complex 1
E
(kJ/mol)
Complex
2
E
(kJ/mol)
Complex
3
E
(kJ/mol)
Cu–NCS-
Cu–SCN
a
0.0
Cu–NCS-
Cu–SCN
0
Cu–NCS
0
50.0
58.07
Cu–SCN 61.94
N-bonded isomers appear more stable than the S-isomers in
all complexes.
The molecular energy of N-bound isomer was taken as a reference
in each complex
ꢀ
ꢀ
N
S
DENꢁS ¼ E ꢁ E
ð1Þ
ꢀ
ꢀ
The interaction between the ligands and the metal man-
ifests itself in the charges on the complex metal ions. In
order to elucidate the origin of the observed variation in
relative energies more quantitatively, atomic charge anal-
yses were carried out. Table 3 summarizes the results of
natural bond population (NPA) calculations for the Cu–
NCS and Cu–SCN structures. Taking two fragments,
[Cu(L)2]2? and SCN-, as references, the value of the
transferred charge can be calculated. The copper ions in all
the studied complexes are formally in the ?2 oxidation
state, but the calculated natural charges are lower than ?2.
From Table 3, the charges transferred from the SCN-
moiety to the metallic moiety are in the ranges of 0.7–0.73
and 0.53–0.56 |e-| for Cu–N and Cu–S bonding, respec-
tively. Hence, the natural charges indicate that the nitrogen
atoms are better electron donor to copper than the sulfur
atom, and donation from the ligands to the metal is more
prominent than back donation from the metal to the ligands.
The UV–Vis spectra of the complexes in acetonitrile
solution are given in Fig. 4. The electronic spectra of the
compounds display a broad absorption band in the visible
complexes as shown in Scheme 1. It has been observed from
crystallographic data for some M–N–C–S complexes that the
distances of N–C and C–S bonds usually decrease and
increase, respectively, with an increase in M–N–C angle
[18]. From this comparison, we conclude that the N–C bond
distances are in accord with the theoretical results [25].
However, the C–S bond lengths were smaller than the
predicted values. For complex 1, the Cu–N–C angle is
167.9(4)° and the N–C and C–S bond distances are
˚
1.133(5) and 1.603(4) A, respectively. These values indi-
cate that the Cu–NCS bonding in complex 1 has a domi-
nant contribution from resonance form (I).
Theoretical considerations
The geometries of the complexes were optimized in the
doublet state using the B3LYP functional in the gas phase,
followed by a single-point calculation using the PCM
(polarizable continuum model) implicit solvent method.
The calculated geometries of 1–3 are summarized in
Tables 1, S5 and S6 (in the supplementary content),
respectively. The optimized geometry for compound 1 (as
shown in Fig. S4) displays a distorted square pyramidal
environment, and general trends observed in the experi-
mental data are satisfactorily reproduced in the calcula-
tions. The minor divergence between the experimental and
calculated geometries may come from limitations in the
calculations or may indicate the effects of the crystal
packing or both. Table 2 summarizes the relative energy
according to the Eq. 1, where EN and Es are the energies of
the N-coordinated and S-coordinated complexes, respec-
tively, and DEN–S is difference in their energies. According
to the present DFT calculations in the gas phase, the
region with a maximum at 638 nm (e = 139 M-1 cm-1
)
for 1, 682 nm (e = 123 M-1 cm-1) for 2, and 652 nm
(e = 127 M-1 cm-1) for 3. These absorptions are attrib-
uted to ligand-field transitions. For more qualitative
description of the electronic absorption spectra, the natures
of electronic transitions were investigated by the time-
dependent density functional theory (TD-DFT). Tables 4,
S7 and S8 (in the supplementary content) present the most
important electronic transitions calculated with the TD-
DFT method for the N-bonded isomers of complexes 1–3.
The assignments of the calculated orbital excitations to the
experimental bands are based on an overview of the con-
tour plots and the relative energy to the occupied and
123

Transition Met Chem
Fig. 4 The experimental
(black) and calculated (red)
electronic absorption spectra of
1–3 in acetonitrile
unoccupied orbital involved in the electronic transitions.
The simplified molecular orbital diagrams of 1–3 are pre-
sented in Figs. 5, S5 and S6 (in the supplementary content).
The TD-DFT/PCM calculations show that the longest
wavelength in the experimental absorptions of the com-
plexes originates in the transitions between some lowest
b-spin HOMO and b-spin LUMO. As can be seen from
Fig. 5, the LUMO with b-spin is constructed mainly from
the dx2-y2 copper orbital, whereas the lowest b-spin HOMO
orbitals are localized on thiocyanate with admixture of dCu
orbitals. Accordingly, the transitions assigned to these
absorptions can be seen as mixed d ? d (LF) and
SCN ? d (LMCT). The absorption bands at 380 nm (e =
1,280 M-1 cm-1), and 244 nm (e = 2,750 M-1 cm-1) for 1,
123

Transition Met Chem
Table 4 The electronic
transition calculated with the
TD-DFT method and the
calculated transition to the
experimental absorption bands
of 1
Experimental
k (nm) [E (eV)]
TD-DFT calculation
k (nm)
E (eV)
f
Major contribution
Character
4/638
688.09
683.21
571.86
505.15
483.49
441.23
428.70
425.74
411.18
364.75
328.50
303.02
272.77
227.77
80/1
81/1
17/2
54/2
56/2
81/2
89/2
91/2
02/3
39/3
77/3
09/4
4.54
5.45
0001/0
0014/0
0064/0
0048/0
0016/0
0030/0
0036/0
0168/0
0003/0
1485/0
0006/0
1670/0
0.0045
0.0108
H(b) ? L(b)
p(SCN)/d ? d
p(SCN) ? d
d ? d
H-1(b) ? L(b)
H-16(b) ? L(b)
H-13(b) ? L(b)
H-1(b) ? L(b)
H-4(b) ? L(b)
H-6(b) ? L(b)
H-3(b) ? L(b)
H-2(b) ? L(b)
H-7(b) ? L(b)
H-5(b) ? L ? 4(b)
H-8(b) ? L(b)
H-9(b) ? L(b)
H(b) ? L ? 2(b)
d ? d
p(SCN) ? d
p (Ph) ? d
p (Ph) ? d
380
p (Ph) ? d
p (DMEN) ? d
p (DMEN) ? d
p (Ph) ? d
p(DMEN)/d/p(Ph) ? d
p (DMEN)/d ? d
p (SCN)/d ? p*(Ph)
f—oscillator strength; H—
highest occupied molecular
orbital; L—lowest unoccupied
molecular orbital
244
392 nm (e = 1,330 M-1 cm-1) and 295 nm (e = 3,090
M-1 cm-1) for 2, and 291 nm (e = 3,120 M-1 cm-1) for
3 involve a multitude of electronic transitions calculated
in the 450–200 nm region, but the primary contributions
are from transitions of character p (Ph) ? d and p
(SCN)/d ? *(Ph).
Experimental
Materials and measurements
N,N-dimethyl,N’-benzyl-ethylenediamine (L1) and [Cu(L1)2
(NCS)]ClO4, 1 were prepared according to previously pub-
lished procedures [14]. All solvents were spectral grade and
all other reagents were used as received. Caution! Perchlo-
rate salts are potentially explosive and should be handled
with appropriate care.
Conclusion
Elemental analyses were obtained on a LECO CHN-600
Elemental Analyzer. Absolute metal percentages were deter-
mined using a Varian-spectra A-30/40 atomic absorption flame
spectrometer. All the samples were dried to constant weight
under a high vacuum prior to analysis. Conductance measure-
ments were made at 25 °C with a Jenway 400 conductance
meter on concentrations of 1.00 9 10-3, 6.00 9 10-4, 4.00 9
10-4 and 2.00 9 10-4 M of samples in selected solvents. For
each solvent, a curve was obtained by plotting the molar con-
ductance versus concentration of sample. The curve was then
extrapolated to infinite dilution to obtain the molar conductance
value. Infrared spectra (potassium bromide disk) were recorded
using a Bruker FTIR instrument (400–4,000 cm-1). 1H NMR
spectra were measured with a Bruker 400 DRX Fourier
Transform spectrometer at room temperature (0–20 ppm
(TMS)). The electronic absorption spectra were measured using
a Braic2100 model UV–Vis spectrophotometer (200–400 nm).
To assess the effect of steric crowding on the stability of the
linkage isomers of thiocyanate copper(II) complexes, a series
of unsymmetrical diamine ligands with different bulky alkyl
groups and their complexes were synthesized and character-
ized. The X-ray crystal structure of [Cu(L1)2(NCS)]ClO4, 1
reveals that the copper(II) center is located in a distorted
square pyramidal environment and that the thiocyanate is
terminally coordinated through nitrogen. The results of the
calculations are consistent with the crystallographic and
spectroscopic data, the N-bonded linkage isomer being more
stable than the S-bonded isomer for all three complexes. The
B3LYP/6-31 ? G(d,p) calculations suggest that the coor-
dination environment around copper is the same for three
complexes. Comparison of the calculated IR and UV–Vis
spectra of the complexes with the experimental data allowed
the assignment of the most characteristic bands. These results
show the ineffectiveness of the bulky groups to change iso-
thiocyanate (Cu-NCS) to thiocyanate (Cu-SCN) coordination
in this system, hence other parameters such as hard and soft
acid–base and electronic factors appear to be more important
in such complexes. These are currently under investigation in
our laboratory.
Synthesis of N,N-diethyl,N’-benzyl-ethylenediamine
(L2)
A typical procedure was as follows: A mixture of benzal-
dehyde (30 mmol) and N,N diethyl-1,2-diaminoethane
123

Transition Met Chem
Fig. 5 The energy (eV),
character and some contours of
the molecular orbitals of 2.
Positive values of the orbital
contour are represented in
yellow and negative values in
blue
(30 mmol) in ethanol (50 mL) was stirred for 24 h. The
solvent was then removed under reduced pressure. The
resultant yellow oil was dissolved in methanol (50 mL) and
dried over anhydrous Na2SO4. Concentration under
reduced pressure gave the diimine product as yellow oil.
To the stirred solution of the diimine (6.1 g) in methanol
(60 mL) at room temperature was gradually added NaBH4
(45 mmol) over 0.5 h. The resulting mixture was allowed
to stand overnight, then acetic acid (20 mL) was added.
The mixture was made alkaline with NaOH (4 M) and
extracted with dichloromethane (7 9 10 mL). The com-
bined CH2Cl2 fractions were dried over anhydrous Na2SO4.
Evaporation of the solvent under reduced pressure resulted
in the desired product as an orange oil (4.95 g, 80 %).
Selected IR data (v/cm-1 using KBr): 3,411 (m, N–H str.),
2,975 (s, C–H str. aliphatic), 1,415 (s, Ph–C str.). 1H NMR
(400 MHz, CDCl3), d: 1.05 (t, J = 4.0 Hz, 6H, CH3); 2.66
(q, J = 4.0 Hz, 4H, CH2); 2.77 (t, J = 6.0 Hz, 2H, CH2);
2.85 (t, J = 6.0 Hz, 2H, CH2); 3.89 (s, 2H, CH2–Ph);
7.28–7.35 (m, 5H, Ar–H).
Preparation of N,N-diisopropyl,N0-benzyl-
ethylenediamine (L3)
This ligand was prepared by a similar method to that used
for L2 except that N,N-diisopropyl-1,2-diaminoethane was
used instead of N,N-diethyl-1,2-diaminoethane. The yield
was 82 %. Selected IR data (m/cm-1 using KBr): 3,354 (m,
N–H str.), 2,971 (s, C–H str. aliphatic), 1,407 (s, Ph–C str.).
1H NMR (400 MHz, CDCl3), d: 0.97 (d, J = 4.0 Hz, 12H,
CH3); 2.93 (m, 2H, CH) 2.68 (t, J = 3.0 Hz, 2H, CH2);
2.75 (t, J = 3.0 Hz, 2H, CH2); 3.80 (s, 2H, CH2–Ph);
7.28–7.35 (m, 5H, Ar–H).
123

Transition Met Chem
Preparation of [Cu(L2)2(NCS)]ClO4, 2
Table 5 Crystal data and structure refinement of complex 1
Empirical formula
Formula weight
Color
C23H36ClCuN5O4S
A typical procedure was as follows: to a solution of diamine
ligand (0.412 g, 2 mmol) and KNCS (0.08 g, 1 mmol) in
ethanol (30 mL) was slowly added Cu(ClO4)2ꢀ6H2O (0.37 g,
1 mmol) in ethanol (10 mL). The resultant mixture was
stirred for 1 h at room temperature, whereupon the desired
compound precipitated as a green solid. The crude compound
was recrystallized by diffusion of diethyl ether into an ace-
tonitrile solution, yielding green crystals (0.26 g, 41 %).
Selected IR data (v/cm-1 KBr disk): 3,204 (m, N–H str.),
2,084 (s, SCN- str.), 1,423 (s, CH2 - Ph str.), 1,089 (s, ClO4
str.), 748, (w, C–N str.), 629 (m, ClO4 bend). Anal. calcd. for
C27H44CuN5ClO4S (MW = 633.73 g mol-1): C, 51.3; H,
6.7; N, 11.1; Cu, 10.1 %; found: C, 51.2; H, 6.9; N, 11.2; Cu,
10.2 %.
574.59
Prismatic, green
295(2)
Temperature (K)
˚
Wavelength (A)
0.71073
Crystal system
monoclinic
P21
Space group
Crystal size (mm)
Unit cell dimensions
0.40 9 0.35 9 0.19
˚
a (A)
10.2415(4)
˚
b (A)
9.1760(3)
˚
c (A)
14.6941 (4)
b
94.7300 (10)°
1376.19 (8)
3
˚
Volume (A )
Z
2
Preparation of [Cu(L3)2(NCS)]ClO4, 3
Calculated density
1.390 Mg/m3
F(0 0 0)
600
˚
h range for data collection ()
2.34 – 27.49
This complex was prepared by a similar method to that used
for [Cu(L2)2(NCS)]ClO4, except that L3 was used instead of
L2. The compound was obtained as a green solid (0.152 g,
53 %). Selected IR data (v/cm-1 using KBr): 3,204 (s, N–H
str.), 2,086 (s, SCN- str.), 1,424 (m, CH2 - Ph str.), 1,076 (s,
ClO4 str.), 805 (w, C–N str.), 624 (m, ClO4 bend). Anal.
calcd. for C31H50CuN5ClO4S (MW = 687.82 g mol-1): C,
54.1; H, 7.3; N, 10.2; Cu, 9.2 %; found: C, 54.3; H, 7.2; N,
10.0; Cu, 9.3 %.
Index ranges
-13 B h B 13
-11 B k B 11
-14 B I B 19
1.002
l (mm-1
)
Reflections collected/unique
Completeness to h = 27.49
Absorption correction
7,153/2,509 [R(int) = 0.0159]
99.6 %
Multi-scan
Full-matrix least-square on F2 a
Refinement method
Data/restraints/parameters
Final R indicesa [I [ 2r (I)]b
Goodness of fit on F2c
R indices (all data)
5,609/1/320
X-ray structure determination
R1 = 0.0345, wR2 = 0.1000
0.804
The X-ray measurement of [Cu(L1)2(NCS)]ClO4 was made
on a Bruker-Nonius X8 ApexII diffractometer equipped with
a CCD area detector using graphite-monochromated Mo–Ka
R1 = 0.0433, wR2 = 0.1084
0.485 and -0.301
-0.009(12)
-3
˚
Largest diff. peak and hole, e A
Flack parameter
P
˚
P
radiation (k = 0.71,073 A) generated from a sealed tube
a
b
c
R ¼ ðjjFoj ꢁ jFcjjÞ=j jFo
source. Data were collected and reduced by SMART and
SAINT software [26] in the Bruker packages. The structure
was solved by direct methods [27, 28] and then developed by
least-squares refinement on F2 [29]. The complete condi-
tions for data collection and structure solution are given in
Table 5. All hydrogen atoms were refined by isotropic
approximation in a riding model with Uiso(H) parameters
equal to 1.2Ueq(Ci), for methyl groups equal to 1.5Ueq(Cii),
where U(Ci) and U(Cii) are, respectively, the equivalent
thermal parameters of the carbon atoms to which corre-
sponding hydrogen atoms are bonded. Refinement of F2 was
against all reflections.
nh
i
h
io
1=2
ꢁ
ꢂ
P
P
2
2
wR ¼
ð
Þ
=
w
Fo2
ꢁ
ꢂ
ꢁ
ꢂ
P
S ¼ ½ w F2o ꢁ Fc2 2= Nobs ꢁ Nparam
s
gas phase. Optimization in solvent was then performed by a
single-point calculation using implicit solvent method. The
solvent effect was simulated using the polarizable contin-
uum model with the integral equation formalism (CPCM).
The electronic structures of the calculated molecules were
analyzed utilizing the natural bond orbital (NBO) method
and the associated natural population analysis (NPA) [33].
It should be mentioned that the NBO method is particularly
valuable for inorganic complexes, because the approach
provides a good description of the charge distribution
which is less sensitive to the computational parameters
such as choice of basis set [34]. The X-ray crystallographic
structure for [Cu(L1)2(NCS)]ClO4 was used to generate
Computational methods
The DFT calculations were performed with Gaussian09
software [30]. Optimization methods were carried out ini-
tially at the B3LYP/6-31G** [31, 32] level of theory in the
123

Transition Met Chem
7. Cusumano M, Guglielmo G, Marricchi P, Ricevuto V (1978)
Inorg Chim Acta 30:29
8. Machura B, Switlicka A, Penkala M (2012) Polyhedron 45:221
9. Cavichiolo LJ, Hasegawa T, Nunes FS (2006) Spectrochim Acta
A 64:161
10. Basolo F, Baddly WH, Burmeister JL (1964) Inorg Chem 3:1202
11. Burmeister JL, MacDougall JJ, Nelson JH (1982) Inorg Chim
Acta 63:75
12. Meek DW, Nicpon PE, Meek VI (1970) J Am Chem Soc 92:5351
13. Fu A-P, Du D-M, Zhou Z-Y (2004) J Mol Struct 676:133
14. Golchoubian H, Koohzad S, Ramzani M, Farmanzadeh D (2013)
Polyhedron 51:1
15. Burmeister JL (1966) Coord Chem Rev 1:205
16. Tsiamis C, Themeli M (1993) Inorg Chim Acta 206:105
17. Foresman JB, Fisch A (1996) Exploring chemistry with electronic
structure method, 2nd edn. Gaussian Inc, Pittsburgh, PA
18. Geary WJ (1971) Coord Chem Rev 7:81
initial complex geometries. In the computational models,
the perchlorate anion was ignored and the monocationic
charge of all complexes was taken into account. The
optimized geometries were verified as two minima by
performing a frequency calculation; all of the vibrations in
the calculated vibrational spectra were real number. The
electronic spectra of the compounds were calculated with
the TD-DFT method. Calculations were carried out using
mixed basis sets; the LANL2DZ basis set including
effective core potential (ECP) of Hay and Wadt [35–37]
was used for Cu and 6-31 ? G(d,p) for all other atoms.
Supplementary data:
19. Addison AW, Rao TN (1984) J Chem Soc Dalton Trans 7:1349
20. Golchoubian H, Afshar ZM, Moayyedi G, Bruno G, Rudbari HA
(2012) Chin J Chem 30:1873
21. Golchoubian H, Moayyedi G, Bruno G, Rudbari HA (2011)
Polyhedron 30:1027
22. Hall AC (1963) J Chem Soc 1963:5745
23. Konex JR, Eriks K (1968) Inorg Chem 7:84
24. Ferrari A, Braibanti A, Bigliardi G, Lanfredi AM (1965) Acta
Crystallogr 18:367
25. Pauling L (1960) The nature of the chemical bond. Cornell
University Press, Ithaca, New York
26. Bruker AXS Inc (2007) SMART (Version 5.060) and SAINT
(Version 6.02), Madison, Wisconsin
27. Burla MC, Caliandro R, Camalli M, Carrozzini B, Cascarano GL,
De Caro L, Giacovazzo C, Polidori G, Spagna R (2005) J Appl
Cryst 38:381
CCDC 941976 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/conts/retrieving.html or from the
Cambridge Crystallographic Data Centre, 12, Union Road,
Cambridge CB2 1EZ, UK; fax: (?44) 1223 336033; or
e-mail: deposit@ccdc.cam.ac.uk. Supplementary content:
IR spectra of the ligands, experimental and calculated IR
spectra of the complexes, The optimized structure of the
complexes, the molecular orbitals of complexes 1 and 3, the
calculated and experimental frequency for complexes 1-3,
the molar conductivities data of the complexes, the selected
optimized bond lengths and angles for complexes 2 and 3 and
the electronic transition calculated with the TD-DFT method
and the calculated transition to the experimental absorption
bands of two and three.
28. Sheldrick GM (2008) SHELXL97, Program for Crystal Structure
¨
Refinement. University of Gottingen, Germany
29. SHELXT LN (2008) Version 5.10, Bruker Analytical X-ray Inc,
Madison, WI
30. Frisch MJ, Trucks GW, Schlegel HB, Scuseria GE, Robb MA,
Cheeseman JR, Scalmani G, Barone V, Mennucci B, Petersson GA,
Nakatsuji H, CaricatoM, Li X, HratchianHP, Izmaylov AF, BloinoJ,
Zheng G, Sonnenberg JL, Hada M, Ehara M, Toyota K, Fukuda R,
Hasegawa J, Ishida M, Nakajima T, Honda Y, Kitao O, Nakai H,
Vreven T, Montgomery JA, Peralta JE, Ogliaro F, Bearpark M, Heyd
JJ, Brothers E, Kudin KN, Staroverov VN, Kobayashi R, Normand J,
Raghavachari K, Rendell A, Burant JC, Iyengar SS, Tomasi J, Cossi
M, Rega N, Millam JM, Klene M, Knox JE, Cross JB, Bakken V,
AdamoC, Jaramillo J, Gomperts R, StratmannRE, Yazyev O, Austin
AJ, Cammi R, Pomelli C, Ochterski JW, Martin RL, Morokuma K,
Zakrzewski VG, Voth GA, Salvador P, Dannenberg JJ, Dapprich S,
Daniels AD, Farkas O, Foresman JB, Ortiz JV, Cioslowski J, Fox DJ
(2009) Gaussian 09, revision A. 02. Gaussian Inc., Wallingford, CT
31. Becke AD (1993) J Chem Phys 98:5648
Acknowledgments We are grateful for the financial support of
university of Mazandaran of the Islamic Republic of Iran.
References
1. Buda C, Kazi AB, Dinescu A, Cundari TR (2005) J Chem Inf
Model 45:965
2. Khan AR, Socol SM, Meek DW, Yasmeen R (1995) Inorg Chim
Acta 234:109
3. Chowdhury S, Koshino N, Canlier A, Mizuoka K, Ikeda Y (2006)
Inorg Chim Acta 359:2472
´
4. Gancheff JS, Acosta A, Armentano D, De Munno G, Chiozzone R,
32. Lee C, Yang W, Parr RG (1988) Phys Rev B37:785
33. Feed AE, Weinhold F (1985) J Chem Phys 83:1736
34. Feed AE, Curtiss LA, Weinhold F (1988) Chem Rev 88:899
35. Hay PJ, Wadt WR (1985) J Chem Phys 82:270
36. Wadt WR, Hay PJ (1985) J Chem Phys 82:284
37. Hay PJ, Wadt WR (1985) J Chem Phys 82:299
´
Gonzalez R (2012) Inorg Chim Acta 387:314
´
5. Gonzalez R, Barboza N, Chiozzone R, Kremer C, Armentano D,
Munno De, Faus GJ (2008) Inorg Chim Acta 361:2715
6. Brewster TP, Ding W, Schley ND, Hazari N, Batista VS, Crab-
tree RH (2011) Inorg Chem 50:11938
123