Synthesis of phosphine-containing novel Pd(II) and Ni(II) complexes: Electrochemical, photophysical and quantum chemical studies

Article abstract of DOI:10.1016/j.molstruc.2019.126889

Pd(ll) and Ni(ll) complexes of bis(diphenylphosphinemethyl) aminobutyl, ((Ph₂PCH₂)₂N(CH₂)₃(CH₃)₃), were synthesized using Schlenck techniques under nitrogen atmosphere. Synthesized complexes were characterized by using thermal analysis, elemental analyses, ¹H NMR, ³¹P NMR, FT-IR and UV–Vis techniques. Single crystal X-Ray diffraction analysis confirms the structure of the newly synthesized compounds. The electrochemical properties of complexes were studied by using cyclic voltammetry. All complexes exhibited intra-ligand (π→π*) fluorescence in CH₂Cl₂. Hartree Fock was used to determine the electronic structure and properties of the complexes. Band gaps of the newly synthesized complexes were calculated as 3.19eV and 3.15eV and showed good optical properties.

Full text of DOI:10.1016/j.molstruc.2019.126889

Journal of Molecular Structure 1198 (2019) 126889
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Synthesis of phosphine-containing novel Pd(II) and Ni(II) complexes:
Electrochemical, photophysical and quantum chemical studies
,
*
a
a
b
Gurbet Yerlikaya a , Eylül Büs¸ ra Tapanyigit , Bilgehan Güzel , Onur S¸ ahin ,
Gülfeza Kardas¸
ꢀ
a
a Çukurova University, Science and Letters Faculty, Chemistry Department, 01330, Adana, Turkey
b Sinop University, Scientific and Technological Research Application and Research Center, 57000, Sinop, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Pd(ll) and Ni(ll) complexes of bis(diphenylphosphinemethyl) aminobutyl, ((Ph2PCH2)2N(CH2)3(CH3)3),
were synthesized using Schlenck techniques under nitrogen atmosphere. Synthesized complexes were
characterized by using thermal analysis, elemental analyses, 1H NMR, 31P NMR, FT-IR and UVeVis
techniques. Single crystal X-Ray diffraction analysis confirms the structure of the newly synthesized
compounds. The electrochemical properties of complexes were studied by using cyclic voltammetry. All
Received 1 April 2019
Received in revised form
2 July 2019
Accepted 31 July 2019
Available online 5 August 2019
complexes exhibited intra-ligand (p/p*) fluorescence in CH2Cl2. Hartree Fock was used to determine
the electronic structure and properties of the complexes. Band gaps of the newly synthesized complexes
were calculated as 3.19eV and 3.15eV and showed good optical properties.
© 2019 Elsevier B.V. All rights reserved.
Keywords:
Bis(diphenylphosphinomethyl)aminobutyl
Electrochemistry
X-ray crystallography
Hartree Fock
Optical properties
1. Introduction
Due to the d10 configuration of group 10 metal complexes, they
exhibit longer excited-state existence [16]. According to the liter-
Phosphorus compounds are a group of very amazing ligands in
organometallic chemistry, which are also helpful mediators in
organic synthesis [1e4]. The synthesis of metal complexes carrying
a phosphine ligand with usual stability and reactivity is yet one of
the important research areas [5e7]. Like organometallic com-
pounds, they give a range of electronic properties and a wide sort of
structure adjusted by way of the coordinated metal center [8].
Metal complexes are likely to be formed from strong electron-
donating phosphine group and coordinatively unstable phopho-
nate group ligands [9]. Furthermore, phosphines of heteroleptic
group 10 metal complexes have displayed amazing photo-
luminescent properties and molecular electrical conducting [10]..
Also they have presented scarce CeH-M intramolecular in-
teractions [11,12]. Resulting from the low-lying metal d-d excited
states which allow nonradiative decay of the MLCT excited state,
study concerning first row transition metals has been restricted
because of their frequent intensely short-lived excited states
compared to 2nd and 3rd row transition metal complexes [13e15].
ature, studies on the photophysical properties and quantum
chemical calculations of PCN type phosphines are very rare.
The purpose of this work was to synthesize Pd(ll) and Ni(ll)
complexes of bis(diphenylphosphinomethyl)aminobutyl ligand.
The compounds were identified together with single X-ray
diffraction techniques and various spectroscopic techniques. Pho-
tophysical and electrochemical properties of the complex of Pd(ll)
and Ni(ll) have also been studied. Theoretical calculations help to
determine electronic structure and properties of complexes. It can
be used to successfully relate the molecular structure, selectivity
and chemical reactivity in the process, which further helps to un-
derstand the mechanism of a process on the molecular scale.
2. Experimental
2.1. Materials and methods
The synthesis was done under nitrogen atmosphere using
Schlenk glassware. EtOH, Et2O and CH2Cl2 were used as solvent.
Solvents were dried using conventional techniques and freshly
distilled under nitrogen atmosphere before use. Tetrabutyl
* Corresponding author.
E-mail address: gurbet.yerlikaya@gmail.com (G. Yerlikaya).
ammoniumperchlorate
(TBAP),
[PdCl2(COD)](COD:1,5-
https://doi.org/10.1016/j.molstruc.2019.126889
0022-2860/© 2019 Elsevier B.V. All rights reserved.

2
G. Yerlikaya et al. / Journal of Molecular Structure 1198 (2019) 126889
cyclooctadiene) and NiCl2 were purchased from Sigma-Aldrich. The
synthesis of bis(diphenylphosphinomethyl)aminobutyl were car-
ried out according to literature procedures. Elemental analyses
were studied using a Flash 2000 organic elemental analyzer. FT-IR
spectra were obtained as KBr pellets in a 4000e450 cmꢀ1 range
with a PerkinElmer RX1 FT-IR system. UVeVis spectra were taken
using CH2Cl21i3n a 200e800 cmꢀ1 range with a PerkinElmer system.
1H and 31P, C NMR spectra were taken at 25 ꢁC in CDCI3 with
Varian Mercury 200 MHz NMR spectrometer. Luminescence prop-
erties were determined in dichloromethane (DCM) at room tem-
perature with PerkinElmer LS 55 fluorescence spectrophotometer.
Thermogravimetric curves were taken on a PerkinElmer Pyris
Diamond TG/DTA at a heating rate of 10 ꢁC/min under nitrogen
atmosphere. Cyclic voltammetry measurements were carried out
by using a Gamry interface 1000 electrochemical analyzer. Three-
electrode configuration was used the cyclic voltammetry with Ag/
AgCl electrode, glassy carbon electrode, and platinum wire as the
reference, working, and auxiliary electrodes, respectively. 0.1M
TBAP was used as the supporting electrolyte, in CH2Cl2.
(Fig. S2). 13C NMR (CDCI3, 25 ꢁC)
d: 13.79 [P-CH2-N-CH2-CH2-CH2-
CH3], 20.27 [P-CH2-N-CH2-CH2-CH2], 27.55 [P-CH2-N-CH2-CH2],
56.62 [P-CH2-N-CH2], 62.80 [P-CH2-N], 128.58 [P-C-CH-CH-CH,
phenyl], 129.27 [P-C-CH-CH, phenyl], 131.52 [P-C-CH, phenyl],
134.04 [P-C-CH, phenyl] (Fig. S3). 31P NMR (CDCI3, 25 ꢁC)
d:7.99 ppm (Fig. S4). Anal. Calcd. for C30H33CI2NP2Pd (%) C, 55.66; H,
5.10; N, 2.17. Found (%): C, 55.46; H, 5.15; N, 2.08.
2.4. Synthesis of Ni (II) complexes of
Bis(diphenylphosphinomethyl)-aminobuthyl
[NiCl2(Ph2PCH2)2N(CH2)3(CH3)](2)
NiCl2 (0.34g, 1.46 mmol) in CH2Cl2 (10 mL) was added to stirred
solution of [(Ph2PCH2)2N(CH2)3(CH3)], (dppab), (0.69g, 1.48 mmol)
(Scheme 1). The mixture was stirred for 3 h and then solvent was
evaporated. The compound was recrystallized in CH2Cl2/Et2O.
Yield: 0.79g, %90. FT-IR (KBr, cmꢀ1): 3054(Ar, C-H), 2955(Aliphatic,
C-H), 1620(P-Ph), 1508, 1437 (P-C-N), 1307, 1194 (C-N-C), 736,
1
691(monosubstituted, Ph) (Fig. S5). H NMR (CDCI3, 25 ꢁC)
d:
7.91e7.53 [m, 20H, 4phenyl], 3.37 [d, J ¼ 36 Hz,4H, P-CH2-N], 2.49[t,
2H, N-CH2], 1.14[m, 2H, N-CH2CH2CH2CH3], 1.04 [m, 2H,
N(CH2)2CH2CH3], 0.80 ppm[t, J ¼ 32Hz., 3H, N-(CH2)3CH3)(Fig. S6).
2.2. Synthesis of bis(diphenylphosphinomethyl)aminobutyl
[(Ph2PCH2)2N(CH2)3(CH3)] ligand, (Dppab)
13C NMR (CDCI3, 25 ꢁC)
d: 13.76 [P-CH2-N-CH2-CH2-CH2-CH3], 20.03
Phosphonium salt ([Ph2P(CH2OH)2]CI) (1.2 g, 4.26 mmol) was
obtained using literature procedure [17] and dissolved in 2:1H2O/
MeOH (60 mL). Triethylamine (Et3N) (0.6 mL, 4.39 mmol) and n-
butylamine (0.22 mL, 2.23 mmol) were added respectively to the
solution of [Ph2P(CH2OH)2]CI) and stirred. The mixture was
refluxed for 2 h, and then the oily product was extracted with
[P-CH2-N-CH2-CH2-CH2], 27.75 [P-CH2-N-CH2-CH2], 53.97 [P-CH2-
N-CH2], 61.68 [P-CH2-N],128.62 [P-C-CH-CH-CH, phenyl],131,82 [P-
C-CH, phenyl], 137.16 [P-C-CH, phenyl] (Fig. S7). 31P- NMR (CDCI3,
25 ꢁC)
d: 27.46 ppm (Fig. S8). Anal. Calcd. for C30H33CI2NP2Ni (%) C,
60.14; H, 5.55; N, 2.34. Found (%): C, 60.30; H, 5.75; N, 2.21.
31P NMR data for ligand and metal complexes were given in
Table 1.
CH2CI2, and dried over MgSO4. 1H NMR (CDCI3, ppm)
d: 7.49e7.69
(m, 20H, phenyl), 3.88 (d, J ¼ 3.2 Hz, 4H, P-CH2-N), 2.84 (t, J ¼ 7.6 Hz,
2H, N-CH2), 1.30 (m, 2H, N-CH2CH2CH2CH3), 1.21 (m, 2H, N-
(CH2)2CH2CH3), 0.81 (t, J ¼ 7.2 Hz, 3H, N-(CH2)3CH3) 31P NMR
2.5. X-ray diffraction analysis
(DMSO‑d6, ppm)
d
: ꢀ28.46.
Using a D8-QUEST diffractometer equipped with a graphite-
monochromatic Mo-Ka radiation at 296 K for data collection, suit-
able crystals of 1e2 were chosen. Refining was done by full-matrix
least-squares methods on F2 with SHELXL-2013 [18] after the
structures were solved by direct methods using SHELXS-97 [19]. All
non-hydrogen atoms were purified with anisotropic parameters.
The H atoms were identified from various maps and taken as
treated as riding atoms with C-H distances 0.93e0.97 Å. In 1-2,
because the refine_diff_density max and min values are so small,
2.3. Synthesis of Pd(II) complexes of
Bis(diphenylphosphinomethyl)- aminobutyl
[PdCl2(Ph2PCH2)2N(CH2)3(CH3)](1)
PdCl2(COD) (0.41g, 1.46 mmol) in CH2Cl2 (10 mL) was added to a
solution of [(Ph2PCH2)2N(CH2)3(CH3)], (dppab), (0.69 g, 1.48 mmol)
(Scheme 1.). The mixture was stirred for 3 h. The yellow solid
formed at the end of the reaction. The product was filtered, washed
with diethyl ether, and finally dried. X-ray quality crystals of the
compounds were obtained by slowly evaporating in a CH2Cl2/Et2O
solution. Yield: 0.94 g, %98. FT-IR (KBr, cmꢀ1): 3053(Ar, C-H), 2927
(Aliphatic, C-H), 1626 (P- phenyl), 1437(P-C-N), 1307, 1198 (C-N-C),
737, 690 (monosubstituted, phenyl) (Fig. S1). 1H NMR (CDCI3, 25 ꢁC)
Table 1
31P NMR data for ligand and metal complexes.
Compound
d
(ppm)
Dd(ppm)
[(Ph2PCH2)2N(CH2)3CH3]
[PdCl2(Ph2PCH2)2N(CH2)3CH3]
[NiCl2(Ph2PCH2)2N(CH2)3CH3]
ꢀ28.46
8.06
27.49
e
d
: 7.88e7.13 [m, 20H, 4phenyl], 3.39 [d, J ¼ 112Hz., 4H, P-CH2-N],
36.52
55.95
2.61 [t, J ¼ 72 Hz, 2H, N-CH2], 1.29 [m, 2H, N-CH2CH2CH2CH3], 1.04
[m, 2H, N(CH2)2CH2CH3], 0.77 [t, J ¼ 38.8 Hz, 3H, N-(CH2)3CH3)]
Scheme 1. Synthesis route of compounds of 1 and 2 (M: Pd, Ni).

G. Yerlikaya et al. / Journal of Molecular Structure 1198 (2019) 126889
3
the solvent molecules could not be located from Fourier map. For
this reason, these molecules were eliminated from the refinement
of the structure by means of the SQUEEZE subroutine of PLATON
[20] and the hkl intensities were modified accordingly. The
following procedures were used in our analysis: data collection:
Bruker APEX2 [21]; program was used for molecular graphics were
as follows: MERCURY programs [22]; software used to prepare
material for publication: WinGX [23] Details of data collection and
crystal structure determinations are given in Table 2.
2.6. Molecular structure evaluation
The structures of the complexes of 1 and 2 were investigated
using Hartree Fock as applied in the Gaussian 09W program [24].
Avogadro software was made use of for geometry optimizations of
the 1 and 2 molecule in the gas phase [25,26]. The geometries of the
compounds were improved using Hartree Fock, method with a
basis set of 3-21G for whole atoms lacking symmetry limits. The
molecules were described using a Gaussian 09W package available
with the Gaussian view 5.0 [27]. At a located constant point, the
optimization was due to finish. Electronic properties of the 1 and 2
were looked into with electronegativity (
global hardness ( ), softness(S), energy of the highest occupied
molecular orbital (EHOMO), the lowest unoccupied molecular orbital
c), dipole moment (m),
Fig. 1. The molecular structure of complexes 1-2 (M ¼ Pd(II) in 1 and Ni(II) in 2)
h
showing the atom numbering scheme.
(ELUMO) and the energy gap (DE) between LUMO and HOMO.
of metal complexes, it has been suggested that these complexes
have square planar geometry, as in those of notified studies [28,29].
Pd(ll) and Ni(ll) complexes were also characterized by FT-IR
spectra. According to FT-IR spectra, the complexes indicate
CeNeC stretching peaks around 1194e1198 cmꢀ1 for tertiary
amine. Aromatic C-H strecching band has been found at about
3053e3054 cmꢀ1; the peaks around 1620-1626 cmꢀ1 and 690-
737 cmꢀ1 are assigned for monosubstitue benzene whereas bands
in the range of 2927e2955 cmꢀ1 are for aliphatic C-H streching.
Elemental analysis for C, H, N shows the basic formulas of the
complexes. Based on analytical data, metal to ligan ratio has been
found as 1:1 for complexes [30e32].
3. Results and discussion
3.1. Characterization
The proton numbers calculated in the 1H NMR spectra were
found to be consistent with the integration values. In the spectra,
multiple substituted peaks of monosubstituted benzene are ex-
pected in the aryl-substituted phosphine compounds at about
d
¼ 7.91e7.13 ppm. The presence of doublets of
d
¼ 3.37 ppm
showed peaks of the P-CH2-N group [28,29]. Butyl peaks in the
butylamine group were observed in the range of 0.80e0.77 ppm.
According to 1H NMR spectra, no remarkable difference was
observed between the free phosphine ligand and metal complexes.
31P NMR spectra of the complexes indicated more shielded
signals than the dppab ligands, as shown in Table 1. The coordi-
3.2. X-ray crystal structures of 1e2
The molecular structure of 1e2, with the atom numbering
scheme, is shown in Fig. 1. The crystallographic analyses show that
nation shift values of the complexes (
D
), described by
D
¼
d (com-
plex) ꢀ
d (free ligand), shift depending on the metal centers and the
ligand itself (Table 1). On the basis of 31P NMR data for the geometry
Table 3
Selected bond distances and angles for complexes 1-2 (Å, º).
Table 2
1
2
Crystal data and structure refinement parameters for complexes 1-2.
M-P1
M-Cl1
2.1629(11)
2.1999(11)
95.16(6)
177.04(5)
86.38(5)
2.2388(13)
2.3558(13)
94.46(7)
177.46(5)
87.13(5)
Crystal data
1
2
P1-M-P1i
P1-M-Cl1
P1-M-Cl1i
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C30H33Cl2NP2Ni
599.12
Orthorhombic
Pnma
21.961 (8)
17.533 (7)
8.032 (3)
3093 (2)
4
1.287
2.9e24.8
0.92
22075
3133
C30H33Cl2NP2Pd
646.81
Orthorhombic
Pnma
21.956 (3)
17.853 (2)
8.0202 (8)
3143.7 (6)
4
1.367
2.9e26.0
0.88
34600
3183
Symmetry code: (i) x, -yþ1/2, z for 1e2 (M ¼ Ni(II) in 1 and Pd(II) in 2).
b (Å)
c (Å)
V (Å3)
Table 4
The C-H$$$p interaction parameters for complexes 1-2 (Å, º).
Z
Dc (g cmꢀ3
)
D-H$ $ $A
D-H
H$$$A
D$$$A
D-H$$$A
q
m
range (º)
(mmꢀ1
)
Complex 1
Measured refls.
Independent refls.
Rint
S
C10dH10$$$Cg(1)i
C12dH12$$$Cg(2)ii
Complex 2
0.93
0.93
2.86
2.98
3.613 (5)
3.837 (4)
139
153
0.001
1.04
0.001
0.99
C4dH4$$$Cg(1)i
0.93
2.86
3.613 (7)
139
R1/wR2
0.052/0.124
0.41/-0.31
0.053/0.121
1.09/-0.80
Symmetry codes: (i) 1/2-x, 1-y, ꢀ1/2 þ z; (ii) 1/2-x, 1-y, 1/2 þ z; Cg(1) ¼ C1-C6;
Cg(2) ¼ C7-C12 for 1; (i) 3/2-x, 1-y, 1/2 þ z; Cg(1) ¼ C7-C12 for 2.
Drmax/ )
Drmin (eÅꢀ3

4
G. Yerlikaya et al. / Journal of Molecular Structure 1198 (2019) 126889
the complexes 1-2 appear very alike. Each complex crystallizes in
the space group Pnma. Each M(ll) ion (M ¼ Pd(ll) in 1 and Ni(ll) in 2)
is located on a center of symmetry and is coordinated by two
chlorine atoms and two phosphorus atoms, thus displaying a
square planar coordination geometry. The M-P bond distance is
2.1629(11) Å in 1 and 2.2388(13) Å in 2, while the M-Cl bond dis-
tance is 2.1999(11) Å in 1 and 2.3558(13) Å in 2, respectively. The
bond angle of P-M-Pis 95.16(6)º in 1 and 94.46(7)º in 2 were given
maximized at 320 and 700 ꢁC (Fig. 3). The first clear peak at
250e400 ꢁC coming with a mass loss matching to 72.875% (calcu-
lated. 72.59%) may be due to the release of dppab. The second
decomposition stages at 400e850 ꢁC involve the loss of Cl
(observed ¼ 9.195%, calculated ¼ 10.976). The decomposition
finished at 850 ꢁC with Pd as a final residue (observed ¼ 15.20%,
calculated ¼ 16.45%). The TG/DTG curves of 2 show two decompo-
sition steps maximized at 300 and 600 ꢁC (Fig. 4). The first clear
peak at 150e350 ꢁC is coming with a mass loss matching to 77.097%
(calculated 77.85%) may be due to release of dppab. Other decom-
position stages at 380e850 ꢁC involve the loss of Cl
(observed ¼ 9.922%, calculated ¼ 11.85). The decomposition
finished at 850 ꢁC with Ni as a final residue (observed ¼ 11.00%,
calculated ¼ 9.80%).
(Table 3). The molecules of 1e2 are linked by C-H …
p interactions
(Table 4). The joining of C-H$$$ interactions produce 2D supra-
p
molecular network running parallel to the bc plane in 1e2 (Fig. 2).
3.3. Thermal analyses
Thermal stability was found by TG/DTG studies from 50 to
900 ꢁC for the complexes. The complexes were heated to 900 ꢁC, all
necessary weight loss was completed by 850 ꢁC. TG/DTG curves
drawn for phosphorus ligand [33] showed two endothermic mass
loss stages. The TG/DTG curves of 1 shows two decomposition steps
3.4. Electronic properties
Absorption spectra of 1 and 2 were ascertained in CH2Cl2 solu-
tion (10ꢀ3 M) at room temperature (Fig. 5). Absorption spectra of
Fig. 2. The C-H$$$
p
interactions in 1-2.
Fig. 3. TG and DTG curve of 1 complex.

G. Yerlikaya et al. / Journal of Molecular Structure 1198 (2019) 126889
5
Fig. 4. TG and DTG curve of 2 complex.
Pd(ll) and Ni(ll) complexes show a strong absorption band at
258e309 nm for 1e2 which are tentatively designated as phos-
phine centered intra-ligand transition. Additionally to high-energy
bands, a low-energy absorption band at 337e343 nm in 1e2 are
likely designated as a mixture of intra-ligand (p/p*) transition
with metal-ligand charge transfer (MLCT) transitions [34]. A weak
absorption at around 477 nm in the spectra of 2 is designated to the
spin allowed transition (1A1g/1A2g) for four coordinate square
planar geometry around Ni (ll).
3.5. Optical band gap analysis
UV spectral results were utilized to figure out the optical energy
band gap of complexes 1 and 2. Optical energy band gap provides
information about the use of complexes in photonic devices. Hence,
it was calculated from equations (1) and (2).
The absorption coefficient (a) figure out according to the
following relation:
Fig. 5. UVevisible spectra of 1 and 2.
Fig. 6. Optical band gap spectra of complexes 1 (a), 2 (b).

6
G. Yerlikaya et al. / Journal of Molecular Structure 1198 (2019) 126889
Absorbance
d
a
¼ 2:303
(1)
where, d (¼ 1 cm) is the diameter of the tub. The Egopt was calcu-
lated with respect to the following equation [35e37].
ða
hn
Þ1=r ¼ Aðh
n
ꢀ EgÞ
(2)
where, the stationary such as h, A,
n
are having their canonical
senses, r is described as a sign value that discriminate the optical
absorption continuum and the value of it for direct allowed tran-
2
sitions,1/2 [38e40]. The (
a
hn
)
vs h
n, plots have been shown in
Fig. 6 and the value of the optical energy band gap was carried from
the point of interception on x(h
to be 3.19 eV and 3.15eV, respectively. These values indicate that the
compounds are within the visible region range.
n
) axis where (
a
h
n
)2 ¼ 0 and found
3.6. Fluorescence spectral studies
Fig. 8. The cyclic voltamogram of 1 mM (1, 2 complex and TBAP) at glassy carbon
electrode in 0.1M TBAP þ DCM solution at scan rate 100 mVsꢀ1
.
The emission spectra of Pd(ll) (1) and Ni(ll) (2) complexes in
CH2Cl2 at room temperature are illustrated in Fig. 7. The excitation
of Pd (ll) and Ni (ll) complex in DCM solution resulted in emission at
(3)e(5) respectively.
l
557 nm and l 583.5 nm, respectively. As shown in Fig. 7, the
excitation intensity of Pd (II) complex is higher than that of Ni (II)
complex. The emission peak observed in 1 and 2 was improved by a
tune of 6.5 and 2.5 nm, respectively. Emission spectra also proved
the formation of aminomethyldiphosphine metal complexes
resulting to an increased energy gap between ground state and
excited state. Emission spectra also prove an emission origin,
EHOMO ¼ ½ ꢀ eððEoxonsetðvs: Ag=AgCIÞ ꢀ ðEoxonsetðFc=Fc
þ vs: Ag=AgCIÞÞ ꢀ 4:8eVꢂ
(3)
ELUMO ¼ ½ ꢀ eððEredonsetðvs: Ag=AgCIÞ ꢀ ðEredonsetðFc=Fc
þ vs: Ag=AgCIÞÞ ꢀ 4:8eVꢂ
mainly not only due to p/p* intraligand transition but also with
some metal-ligand charge transfer (MLCT) character [41,42].
(4)
3.7. Electrochemical properties of complexes 1 - 2
D
EgCV ¼ HOMO ꢀ LUMO
The electrochemical parameters listed in Table 5 were deter-
(5)
The electrochemical properties of complexes 1e2 were inves-
tigated cyclic voltammetry (CV). The CV's of 1 mM compounds 1, 2
and TBAP in 0.1 M TBAP under an inert atmosphere are shown in
Fig. 8. The oxidation and reduction peaks of compounds 1e2 were
observed at ꢀ0.760 V,-0.750V and at ꢀ0.960V, ꢀ0.950V, the onset
potentials of oxidation and reduction of ferrocene were 0.298 V and
0.357 V (vs.Ag/AgCl) respectively.
mined from CVs. The results obtained from Table 5 showed that the
compounds were zero-valued and the minor
that the compounds were stable.
DEp value indicated
The magnitude of
ibility. When the Ep value increases, irreversibility increases.
HOMO, ELUMO and
ECgV are calculated according to equations
DEp value gives information about irrevers-
D
D
3.8. Theoretical calculations
E
Theoretical calculations help us understand the structure of 1
and 2. The complexes were analyzed by working structure models
(Figs. 9 and 10). Formation of the transition state linked to the
interaction between ELUMO and EHOMO of reactants were found with
the help of the molecular orbital theory [43]. The values of EHOMO
indicate the ability to donate electrons and emphasize the electron
acceptor ability of molecular orbitals [44]. The size of E shows the
stability of complexes of 1 and 2 [45]. Table 6 illustrates the cor-
responding EHOMO, ELUMO, DE, m, c, S and h values of the optimized
structures of complexes of 1 and 2 [46]. For a molecule, the high
D
E
means an electronic transition from the HOMO to the LUMO orbital
and gives information about stability.
Also, the higher dipole moment is related to polarity and the
dipole moments of the complexes of 1 and 2 are 16.18 and 27.94
Debye, respectively. According to these results, molecule 1 is more
polar than molecule 2.
DE ¼ ELUMO ꢀ EHOMO
(6)
Using equations (7)e(9) the quantum chemical parameters be-
Fig. 7. The Emission spectra of 1 and 2.
ing the exact , Ѕ and were calculated [45,47e49].
h
c

G. Yerlikaya et al. / Journal of Molecular Structure 1198 (2019) 126889
7
Table 5
Electrochemical parameters for 1e2 complexes (V).
Complexes
Epa
Epc
D
Ep
EHOMO
ELUMO
D
EgCV
[PdCl2(Ph2PCH2)2N(CH2)3CH3]
[NiCl2(Ph2PCH2)2N(CH2)3CH3]
ꢀ0.760
ꢀ0.750
ꢀ0.960
ꢀ0.950
0,200
0.200
ꢀ3.830
ꢀ3.820
ꢀ3.190
ꢀ3.090
ꢀ0.640
ꢀ0.730
Fig. 9. Optimized structure (a), Mulliken charge (b), HOMO (c) and LUMO (d) for neutral compound 1.
4. Conclusions
ELUMO þ EHOMO
Pd(II) and Ni(II) complexes with bis(diphenylphosphinomethyl)
aminobutyl (PCN) ligand were prepared and characterized using
spectroscopic techniques. The coordination of the (diphenylphos-
phinomethyl)aminobutyl ligand takes place via phosphorus atoms
according to X-ray diffraction analyses and 31P, 1H NMR spectra.
Cyclic voltamograms show that complexes display a reversible
redox behavior matching to Pd(II)/Pd(0), Ni(II)/Ni(0) and TBAP. In
addition, anodic and cathodic peak potentials and initial potentials
c
¼ ꢀ ð
Þ
(7)
(8)
(9)
2
ELUMO ꢀ EHOMO
h
¼
2
1
h
S ¼
of peaks were determined by voltamograms,
DE values, HOMO-
LUMO energies, band gap were calculated. The difference be-
tween HOMO-LUMO energy levels is very important in many re-
spects. It gives insight into the stability of the structure, its optical
properties, and in particular the electronic structure of matter.
These parameters provide information about the stability of
molecules. Hard acids choose to react with hard base and likewise,
soft acid selects a soft base according to hard, and soft acids and
bases (HSAB) theory [50]. In the process, complexes of Pd and Ni
behaved as a hard base. The results from Table 6 suggest that 2 is
harder than 1. Finally,
molecules. As formerly published [51], molecules with a rise in
electronegativity tend to draw electrons from the metal.
Complexes of 1 and 2 exhibit intra-ligand (p/p*) fluorescence in
CH2Cl2. The emission spectrum and optical band gap calculated
from UVeVis spectrum. According to these results; The lowest
optical band gap was observed in the compound Pd (II). Therefore,
c indicates electron attracting ability of

8
G. Yerlikaya et al. / Journal of Molecular Structure 1198 (2019) 126889
Fig. 10. Optimized structure (a), Mulliken charge (b), HOMO (c) and LUMO (d) for neutral compound 2.
Table 6
The quantum chemical parameters of 1e2 complexes.
Complexes
EHOMO (eV)
ELUMO (eV)
DЕ (eV)
c
h
S
m
1
2
ꢀ7.04
ꢀ7.94
þ1.08
þ2.07
þ8.12
þ2.98
þ2.94
þ4.06
þ5.01
þ0.25
þ0.20
þ15.06
þ13.04
þ10.01
reaction profile and diastereoselectivity in sulfur ylide promoted aziridination,
Chemistry 13 (17) (2007) 4805e4815.
lower energy is needed to stimulate the Pd (II) complex and it has
been found that Pd (II) compounds exhibit better photophysical
properties than Ni (II) compounds for optical applications. From the
theoretical calculations, as shown in Figs. 9 and 10 HOMO and
LUMO nodes were generally delocalized on phenyl rings.
[3] O.I. Kolodiazhnyi, Methods of preparation of-substituted phosphorus ylides
and their application in organic synthesis, Russ. Chem. Rev. 66 (3) (1997)
225e254.
€
[4] J. Heinicke, N. Peulecke, M. Kohler, M. He, W. Keim, Tuning of nickel 2-
phosphinophenolates e catalysts for oligomerization and polymerization of
ethylene, J. Organomet. Chem. 690 (10) (2005) 2449e2457.
[5] A. Vogler, H. Kunkely, Excited state properties of transition metal phosphine
complexes, Coord. Chem. Rev. 230 (2002) 243e251.
Acknowledgements
[6] L. Dahlenburg, P-Modular bis(phosphines) based on the 1,2-trans-disubsti-
tuted cyclopentane framework in synthesis, coordination chemistry, and
catalysis, Coord. Chem. Rev. 249 (24) (2005) 2962e2992.
[7] T.S. Lobana, P. Kumari, R. Sharma, A. Castineiras, R.J. Butcher, T. Akitsu,
Y. Aritake, Thiosemicarbazone derivatives of nickel and copper: the unprec-
edented coordination of furan ring in octahedral nickel(II) and of triphenyl-
phosphine in three-coordinate copper(I) complexes, Dalton Trans. 40 (13)
(2011) 3219e3228.
[8] B.G. Bharate, A.N. Jadhav, S.S. Chavan, Synthesis, characterization, photo-
luminescence and optical properties of heterobimetallic Cu/Ru hybrid com-
plexes composed of coordination and organometallic sites, Polyhedron 33 (1)
(2012) 179e184.
[9] H.M.S. Bischoff, A. Weigt, B. Lticke, Soluble and supported carbonylation cat-
alysts derived from rhodium-phosphonate-phosphane complexes, J. Mol.
Catal. A Chem. 107 (1996) 339e346.
We thank Çukurova University for financial support (project no.
FDK-2014-3517, FYL-2015-5201). We are grateful to Sinop Univer-
sity, The Scientific and Technological Research Application and
Research Center, for the use of the Bruker D8 QUEST diffractometer.
Appendix ASupplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.molstruc.2019.126889.
References
[10] D.D. Ellis, G. Harrison, A.G. Orpen, H. Phetmung, P.G. Pringle, J.G. deVries,
H. Oevering, Platinum(II), palladium(II) and rhodium(I) complexes of o-, m-
and p-Ph2PC6H4PO(OEt)2. PtCl2eSnCl2 Hydroformylation catalysts modified
with phosphonated triarylphosphines, J. Chem. Soc., Dalton Trans. 5 (2000)
671e675.
[1] C.G. Kokotos, V.K. Aggarwal, Aminals as substrates for sulfur ylides: a syn-
thesis of functionalized aziridines and -heterocycles, Org. Lett. 9 (11) (2007)
2099e2102.
[2] D. Janardanan, R.B. Sunoj, Computational investigations on the general

G. Yerlikaya et al. / Journal of Molecular Structure 1198 (2019) 126889
9
[11] N. Singh, B. Singh, S.K. Singh, M.G.B. Drew, Syntheses, crystal structures and
properties of sterically congested heteroleptic complexes of group 10 metal
ions with p-tolylsulfonyl dithiocarbimate and 1,2-bis (diphenylphosphino)
ethane, Inorg. Chem. Commun. 13 (12) (2010) 1451e1454.
[12] N. Singh, B. Singh, K. Thapliyal, M.G.B. Drew, Synthesis, X-ray crystal struc-
tures and properties of complex salts and sterically crowded heteroleptic
complexes of group 10 metal ions with aromatic sulfonyl dithiocarbimates
and triphenylphosphine ligand, Inorg. Chim. Acta 363 (13) (2010) 3589e3596.
[13] S. Ferrere, B.A. Gregg, Photosensitization of TiO2 by [FeII(2,20-bipyridine-4,40-
dicarboxylic acid)2(CN)2]: band selective electron injection from ultra-short-
lived excited states, Am. Chem. Soc. 120 (1998) 843e844.
[14] D.G.C. Shan-Ming Kuang, David R. McMillin, Phillip E. Fanwick, Richard
A. Walton, Synthesis and structural characterization of Cu(I) and Ni(II) com-
plexes that contain the bis[2-(diphenylphosphino)phenyl]ether ligand. Novel
emission properties for the Cu(I) species, Inorg. Chem. 41 (2002) 3313e3322.
[15] C.L. Linfoot, P. Richardson, T.E. Hewat, O. Moudam, M.M. Forde, A. Collins,
F. White, N. Robertson, Substituted [Cu(I)(POP)(bipyridyl)] and related com-
plexes: synthesis, structure, properties and applications to dye-sensitised
solar cells, Dalton Trans. 39 (38) (2010) 8945e8956.
coordination in anti-tumour copper (I) diphosphine complexes: synthesis of
[Cu (dppe) 2] Cl and analogous complexes (dppe¼ 1, 2-bis (diphenylphos-
phino) ethane), Polyhedron 17 (4) (1998) 513e517.
ꢀ
ꢀ
[33] S. Urus¸ , O. Serindag, M. Digrak, Synthesis, characterization, and antimicrobial
activities of Cu(I), Ag(I), Au(I), and Co(II) complexes with [CH3N(CH2PPh2)2],
Heteroat. Chem. 16 (6) (2005) 484e491.
€
[34] S¸ . Güveli, N. Ozdemir, A. Koca, T. Bal-Demirci, B. Ülküseven, Spectroscopic,
electrochemical and X-ray diffraction studies on nickel(II)-complexes of ace-
tophenone thiosemicarbazones substituted six-carbon groups, Inorg. Chim.
Acta 443 (2016) 7e14.
[35] J. Tauc, R. Grigorovici, A. Vancu, Optical properties and electronic structure of
amorphous germanium, Phys. Status Solidi 15 (2) (1966) 627e637.
[36] J. Tauc, Optical properties and electronic structure of amorphous Ge and Si,
Mater. Res. Bull. 3 (1) (1968) 37e46.
[37] M. Shkir, H. Abbas, Z.R. Khan, Effect of thickness on the structural, optical and
electrical properties of thermally evaporated PbI2 thin films, J. Phys. Chem.
Solids 73 (11) (2012) 1309e1313.
[38] M. Shkir, S. Aarya, R. Singh, M. Arora, G. Bhagavannarayana, T. Senguttuvan,
Synthesis of ZnTe nanoparticles by microwave irradiation technique, and their
characterization, Nanosci. Nanotechnol. Lett. 4 (4) (2012) 405e408.
[39] F. Urbach, The long-wavelength edge of photographic sensitivity and of the
electronic absorption of solids, Phys. Rev. 92 (5) (1953) 1324.
[40] M. Shakir, B. Singh, R. Gaur, B. Kumar, G. Bhagavannarayana, M. Wahab,
Dielectric behaviour and ac electrical conductivity analysis of ZnSe chalco-
genide nanoparticles, Chalcogenide Lett. 6 (12) (2009) 655e660.
[41] M. Shkir, P.S. Patil, M. Arora, S. AlFaify, H. Algarni, An experimental and
theoretical study on a novel donor-pi-acceptor bridge type 2, 4, 5-trimethoxy-
4'-chlorochalcone for optoelectronic applications: a dual approach, Spec-
trochim. Acta A Mol. Biomol. Spectrosc. 173 (2017) 445e456.
[16] N. Robertson, CuI versus RuII: dye-sensitized solar cells and beyond, Chem-
SusChem 1 (12) (2008) 977e979.
[17] M. Keles¸ , O. Altan, O. Serindaǧ, Synthesis and characterization of bis(diphe-
nylphosphinomethyl)amino ligands and their Ni(II), Pd(II) complexes: appli-
cation to hydrogenation of styrene, Heteroat. Chem. 19 (2) (2008) 113e118.
[18] G.M. Sheldrick, Crystal structure refinement with SHELXL, Acta Crystallogr C
Struct Chem 71 (Pt 1) (2015) 3e8.
[19] G.M. Sheldrick, A short history of SHELX, Acta Crystallogr. A 64 (Pt 1) (2008)
112e122.
[20] A.L.S. PLATON, A Multipurpose Crystallographic Tool, Utrecht, Utrecht Uni-
versity, The Netherlands, 2005.
[21] APEX2, Bruker, AXS Inc Madison Wisconsin USA, 2013.
[22] Mercury, version 3.3; CCDC, available online via ccdc.cam.ac.uk/products/
mercury.
[23] L.J. Farrugıa, Computer program abstracts, J. Appl. Crystallogr. 32 (1999)
837e838.
[24] M. Frisch, G. Trucks, H. Schlegel, G. Scuseria, M. Robb, J. Cheeseman,
G. Scalmani, V. Barone, B. Mennucci, G. Petersson, Gaussian 09 Revision D. 01,
2009, Gaussian Inc., Wallingford CT, 2009.
[42] D. Gudeika, V. Zilinskaite, J.V. Grazulevicius, R. Lytvyn, M. Rutkis, A. Tokmakov,
4-(Diethylamino)salicylaldehyde-based twin compounds as NLO-active ma-
terials, Dyes Pigments 134 (2016) 244e250.
ꢁ
ꢁ
[43] M. Finsgar, A. Lesar, A. Kokalj, I. Milosev, A comparative electrochemical and
quantum chemical calculation study of BTAH and BTAOH as copper corrosion
inhibitors in near neutral chloride solution, Electrochim. Acta 53 (28) (2008)
8287e8297.
[44] D. Daoud, T. Douadi, S. Issaadi, S. Chafaa, Adsorption and corrosion inhibition
of new synthesized thiophene Schiff base on mild steel X52 in HCl and H2SO4
solutions, Corros. Sci. 79 (2014) 50e58.
[45] R.G. Pearson, Absolute electronegativity and hardness: application to inor-
ganic chemistry, Inorg. Chem. 27 (4) (1988) 734e740.
[25] M.D. Hanwell, D.E. Curtis, D.C. Lonie, T. Vandermeersch, G.R.H.E. Zurek, Avo-
gadro: an advanced semantic chemical editor, visualization, and analysis
platform, J. Cheminf. 4 (17) (2012).
[26] F. Tezcan, G. Yerlikaya, A. Mahmood, G. Kardas¸ , A novel thiophene Schiff base
as an efficient corrosion inhibitor for mild steel in 1.0 M HCl: electrochemical
and quantum chemical studies, J. Mol. Liq. 269 (2018) 398e406.
[27] R. Dennington, T. Keith, J. Millam, GaussView, Version 5, Semichem Inc.,
Shawnee Mission, KS, 2009.
[46] B. Xu, W. Yang, Y. Liu, X. Yin, W. Gong, Y. Chen, Experimental and theoretical
evaluation of two pyridinecarboxaldehyde thiosemicarbazone compounds as
corrosion inhibitors for mild steel in hydrochloric acid solution, Corros. Sci. 78
(2014) 260e268.
ꢀ
[47] O. Altan, O. Serindag, K. Sayın, D. Karakas¸ , Pd (II) complexes of novel phos-
[28] J. Fawcett, R.D. Kemmitt, D.R. Russell, O. Serindag, Zerovalent palladium and
platinum complexes of aminomethylphosphines. Crystal structure of the
palladium (0) dibenzylideneacetone complex [Pd (PhCH- CHCOCH- CHPh)
{((C6H11) 2PCH2) 2NMe}], J. Organomet. Chem. 486 (1e2) (1995) 171e176.
[29] A.M. LaPointe, Parallel synthesis of aminomethylphosphine ligands, J. Comb.
Chem. 1 (1) (1999) 101e104.
phine ligands: synthesis, characterization, and catalytic activities on Heck
reaction, Phosphorus, Sulfur, Silicon Relat. Elem. 191 (7) (2016) 993e999.
[48] N. Karakus, K. Sayin, The investigation of corrosion inhibition efficiency on
some benzaldehyde thiosemicarbazones and their thiole tautomers: compu-
tational study, J. Taiwan Inst. Chem. Eng. 48 (2015) 95e102.
€
[49] E. Arslan, A.A. Gürten, H.Z. Gok, M. Farsak, Electrochemical study of self-
[30] M.J. McKeage, L. Maharaj, S.J. Berners-Price, Mechanisms of cytotoxicity and
antitumor activity of gold (I) phosphine complexes: the possible role of
mitochondria, Coord. Chem. Rev. 232 (1e2) (2002) 127e135.
[31] S.J. Berners-Price, R.J. Bowen, P. Galettis, P.C. Healy, M.J. McKeage, Structural
and solution chemistry of gold (I) and silver (I) complexes of bidentate pyridyl
phosphines: selective antitumour agents, Coord. Chem. Rev. 185 (1999)
823e836.
assembled aminothiol substituted phthalonitrile layers for corrosion protec-
tion of copper, ChemistrySelect 2 (27) (2017) 8256e8261.
[50] D. de la Fuente, I. Díaz, J. Simancas, B. Chico, M. Morcillo, Long-term atmo-
spheric corrosion of mild steel, Corros. Sci. 53 (2) (2011) 604e617.
[51] A. Dutta, S.K. Saha, P. Banerjee, D. Sukul, Correlating electronic structure with
corrosion inhibition potentiality of some bis-benzimidazole derivatives for
mild steel in hydrochloric acid: combined experimental and theoretical
studies, Corros. Sci. 98 (2015) 541e550.
[32] J.S. Lewis, J. Zweit, P.J. Blower, Effect of ligand and solvent on chloride ion