Theoretical and experimental studies on the structure and spectroscopic properties of Ni(II) complexes of the type [Ni(L)(PPh3)] [H 2L = 5-methyl-N-(2-mercaptophenyl)salicylideneimine and 5-chloro-N-(2-mercaptophenyl)salicylideneimin

Article abstract of DOI:10.1016/j.molstruc.2013.01.008

Comparison of experimental and theoretical parameters pertaining to structural and spectral properties of two nickel(II) complexes containing triphenylphosphine and 5-methyl-N-(2-mercaptophenyl)salicylideneimine (1) or 5-chloro-N-(2-mercaptophenyl)salicyl

Full text of DOI:10.1016/j.molstruc.2013.01.008

Accepted Manuscript
Theoretical and experimental studies on the structure and spectroscopic prop‐
erties of Ni(II) complexes of the type [Ni(L)(PPh )] [H L = 5-methyl-N-(2-
3 2
mercaptophenyl)salicylideneimine and 5-chloro-N-(2-mercaptophenyl)salicy‐
lideneimine]
M. Muthu Tamizh, K. Senthilkumar, B.F.T. Cooper, C.L.B. Macdonald, R.
Karvembu
PII:
S0022-2860(13)00019-7
DOI:
http://dx.doi.org/10.1016/j.molstruc.2013.01.008
MOLSTR 19478
Reference:
To appear in:
Journal of Molecular Structure
Received Date:
Revised Date:
Accepted Date:
13 August 2012
17 December 2012
3 January 2013
Please cite this article as: M. Muthu Tamizh, K. Senthilkumar, B.F.T. Cooper, C.L.B. Macdonald, R. Karvembu,
Theoretical and experimental studies on the structure and spectroscopic properties of Ni(II) complexes of the type
[Ni(L)(PPh )] [H L 5-methyl-N-(2-mercaptophenyl)salicylideneimine and 5-chloro-N-(2-
=
3
2
mercaptophenyl)salicylideneimine], Journal of Molecular Structure (2013), doi: http://dx.doi.org/10.1016/
j.molstruc.2013.01.008
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Theoretical and experimental studies on the structure and spectroscopic
properties of Ni(II) complexes of the type [Ni(L)(PPh3)] [H2L = 5-methyl-N-(2-
mercaptophenyl)salicylideneimine and 5-chloro-N-(2-
mercaptophenyl)salicylideneimine]
M. Muthu Tamizha, K. Senthilkumarb, B.F.T. Cooperc, C.L.B. Macdonaldc, R. Karvembua,*
a Department of Chemistry, National Institute of Technology, Tiruchirappalli 620 015, India
b Department of Physics, Bharathiar University, Coimbatore 641 046, India
c Department of Chemistry and Biochemistry, University of Windsor, Ontario N9B 3P4, Canada
ABSTRACT
Comparison of experimental and theoretical parameters pertaining to structural and spectral
properties of two nickel(II) complexes containing triphenylphosphine and 5-methyl-N-(2-
mercaptophenyl)salicylideneimine (1) or 5-chloro-N-(2-mercaptophenyl)salicylideneimine
(2) are presented. The calculated structural results of these complexes show that the DFT can
well reproduce the structure of title compounds. The UV, IR and NMR spectra of the title
compounds are calculated using both experimental and theoretical methods. The optical
absorption properties of the title compounds are calculated using time-dependent density
functional theory method (TD-DFT). The IR spectra are calculated from the harmonic
vibrational frequencies at the ground-state geometry of the title-compounds. The NMR
spectra are calculated using the gauge-independent atomic orbital (GIAO) method. The
results calculated using theoretical methods coincide well with the experimental
methods.
Keywords:
Nickel(II);
Schiff
base;
Triphenylphosphine;
X-ray
structure;
Density functional theory
* Corresponding author.
E-mail address: kar@nitt.edu (R. Karvembu)
1

1. Introduction
Although not recognized until the 1970s, nickel plays numerous roles in biology and
chemistry. For example, nickel is a key component in urease, an enzyme which assists the
hydrolysis of urea. The NiFe-hydrogenases contain a dinuclear nickel-iron complex in
addition to the ubiquitous iron-sulfur clusters [1]. Such NiFe-hydrogenases characteristically
oxidize hydrogen. A nickel-tetrapyrrole coenzyme, F430, is present in the methyl coenzyme
M reductase which powers methanogenic archaea [2]. One of the carbon monoxide
dehydrogenase enzymes contains a Fe-Ni-S cluster, and other nickel-containing enzymes
include a class of superoxide dismutases and a glyoxalase [3]. For the work presented herein,
it is important to note that urease contains nickel(II) which is surrounded by O and N donor
ligands from protein and in hydrogenases nickel is bonded to S atoms. Hence, the study of
well-characterized Ni(II) complexes containing O,N,S donor ligand may prove to be useful
models that can offer important fundamental insights into the chemistry of such biologically-
relevant nickel centers.
Furthermore, nickel complexes containing triphenylphosphine ligands play an
important role in small molecule catalysts used for the synthesis of fine chemicals and drug
molecules [4-8]. They are particularly useful for coupling reactions such as homocoupling of
aryl methanesulphonates [9], cross coupling of benzylic and allylic dithioacetals with alkyl
Grignard reagents [10], coupling of aryl iodide with thiourea [11], coupling of 3-methoxy-1-
phenylthio-1-propene with Grignard reagents [12], etc. It is understood from the foregoing
that the investigation of nickel complexes containing triphenylphosphine is similarly
worthwhile. Although there are many reports about nickel(II) complexes with O,N,S donor
ligands [13-15] and of nickel(II) complexes with triphenylphosphine ligands [14-18], there
are very few reports of nickel(II) complexes containing both O,N,S donor and
triphenlphosphine ligands [19-26]. In light of the chemistry outlined above, complexes of this
kind are interesting as both models of enzymes and for homogeneous catalysis. Hence, we
undertook experimental and theoretical investigations of the structural and spectroscopic
aspects of nickel(II) complexes composed of a simple ONS donor ligand and
triphenylphosphine (Scheme 1). Herein we report the crystal structures of two Ni(II)
complexes and compare their theoretical and experimental properties.
2

[R = CH3 (1) or Cl (2)]
Scheme 1. Structure of Ni(II) complexes.
2. Experimental and computational details
2.1. Synthesis
Complexes 1 and 2 have been synthesized from the reaction between ethanolic
solution of [NiCl2(PPh3)2] and dichloromethane solutions of 5-methyl-N-(2-
mercaptophenyl)salicylideneimine or 5-chloro-N-(2-mercaptophenyl)salicylideneimine in a
1:1 molar ratio at 25–27C [19].
2.2. Xray crystallography
Single crystals of the Ni complexes used for Xray diffraction studies were grown at
room temperature from a dichloromethaneethanol solution by the diffusion of diethyl ether
vapour. Diffraction data were collected on a Bruker APEX CCD diffractometer using
graphite monochromated Mo K radiation ( = 0.71073 Å). The structures were solved by
direct methods (SHELXS97) [27] and refined by full-matrix least squares fitting based on
F2 using the program SHELXL97 [28] as implemented in WinGX [29]. All non-hydrogen
atoms were refined with anisotropic displacement parameters. All H atoms were located by
difference Fourier syntheses and were then included in the refinement at idealized geometries
riding on the atoms to which they were bonded. For complex 1, the SQUEEZE [30] routine in
PLATON was employed to remove a disordered and partial occupancy dichloromethane
solvent molecule proximate to an inversion center; the process improved the R1(obs) value
from ca. 0.060 to 0.039.
3

2.3. Computational details
Ground state geometry of the title compounds was optimized using density functional
theory (DFT) method employing Becke’s three parameter hybrid exchange functional (B3)
[31] combined with correlation functional of Lee, Yang and Parr (LYP) [32], together called
as B3LYP. The effective core potential (ECP) basis set LACV3P was employed for Ni and
the 6-311G(d,p) basis set was used for all other atoms (basis set A). The LACV3P basis set is
a triple-zeta contraction of the LACVP [33] ECP basis set available in the Jaguar program
[34]. Vibrational frequency calculations were performed at the same level of theory and the
results confirm that the optimized geometry is at stationary point of the potential energy
surface featuring zero imaginary frequencies. NMR shielding tensors for carbon and
hydrogen atoms in the title compounds were calculated using the Gauge-independent atomic
orbital (GIAO) method at the level of theory described above [35,36]. Optical spectra were
calculated using time-dependent density functional theory (TD-DFT) calculations which were
performed at B3LYP/A level of theory. These calculations used the ground state optimized
structure and solvent effects (for acetonitrile) were included through the use of the polarized
continuum model (PCM) [37,38] in the self-consistent reaction field (SCRF) approach. All
the calculations were carried out using the Gaussian 09 suite of programs [39].
3. Results and discussion
3.1. X-ray crystallographic studies
The crystallographic and measurement data are shown in Table 1 and pertinent
interatomic distances and angles are listed in Table 2. Figures 1A and 2A present thermal
ellipsoid plots of the molecular structures of complexes 1 and 2. Both the complexes
crystallize in the triclinic space group P-1 with one complex per asymmetric unit. In each
case, the nickel(II) atom exists in a four coordinate square planar geometry defined by the
tridentate Schiff bases and the monodentate triphenylphosphine ligands. The bond distances
between the nickel atom and coordinating atoms (i.e., Ni1P1, Ni1O1, Ni1N1 and
Ni1S1) are all in the ranges usually observed in Ni(II) complexes and require no further
discussion [19-26]. Likewise, all of the angles about the nickel atom indicate that there are
only minor deviations from the ideal square planar arrangement. Disregarding the aryl
substituents of the triphenylphosphine ligand (i.e. the (LM)NiP fragment), complex 1 is
essentially planar as illustrated by the r.m.s. deviation of 0.042 Å of the non-hydrogen atoms
from the best-fit least-squares plane; the sulfur atom features the largest deviation (0.119 Å)
4

from this plane. The intermolecular interactions in [Ni(LM)(PPh3)] are characterized by π-π
stacks of complexes featuring alternating inter-plane distances of 3.376(6) Å and 3.641(6) Å
that are oriented approximately in the crystallographic [223] direction and that propagate
roughly along the crystallographic a-axis (Figure 3). Similarly, the (LC)NiP fragment of
complex 2 is essentially planar as illustrated by the r.m.s. deviation of 0.053 Å of the non-
hydrogen atoms from a common least-squares plane; the sulfur atom features the largest
deviation (0.128 Å) from this plane. The intermolecular interactions in [Ni(LC)(PPh3)] are
characterized by π-π stacks of complexes that also propagate roughly in the a-direction. The
molecular planes of the molecules in these stacks are oriented approximately in the
cystallographic [5-53] direction and exhibit alternating inter-plane distances of 3.426(6) and
3.447(6) Å. In contrast to complex 1, which has no additional donor functionalities, adjacent
molecules of 2 with the larger inter-plane separation with Ni•••Cl contacts of 3.6720(4) Å
(Figure 4). NiPPh3 group present in complexes 1 and 2 were found to be acceptable rotor as
all three torsion angles are in the range ~ 20-70° with the same sign [40].
3.2. Optimized structures
The electronic structure of two nickel complexes namely [Ni(LM)(PPh3)] (1) and
[Ni(LC)(PPh3)] (2) were also investigated using DFT methods. The starting coordinates
employed in each case were those obtained from the X-ray structure determination and these
were optimized by energy-minimization with the DFT method, B3LYP/A. The optimized
structure of the molecules 1 and 2 are illustrated in Figures 1B and 2B, respectively and
overlays of the calculated and experimental structures are presented in Figures 5 and 6.
Numerical comparisons of experimentally obtained and theoretically predicted values of
selected geometrical parameters of these two nickel complexes are presented in Table 2 and
demonstrate the satisfactory agreement between the calculated and observed metrical
parameters. The largest deviations between the observed and calculated bond distances and
bong angles are 0.069 Å and 2.68 for 1 and 0.07 Å and 3.44 for 2. The root mean square
deviation (RMSD) between experimental and theoretical results is found to be ca 0.026 Å for
the bond distances and ca 1.09 for the bond angles of complex 1. In the case of complex 2,
the RMSD value for the bond distances is ca 0.028 Å and that of the bond angles is ca 1.66.
The dihedral angle values given in Table 2 reveal small deviation between the experimental
and theoretical values. The overlay of each X-ray structure and its optimized geometry model
counterpart highlight the conformational discrepancies between the two (Figures 5 and 6).
The RMSD between the internal coordinates obtained using experimental and theoretical
5

methods is 0.399 and 0.298 Å for molecule 1 and 2, respectively. This result illustrates the
close agreement between the observed and model compounds. Note that the above RMSD
value between the internal coordinates includes the interactions between both bonded and
non-bonded atoms. The small deviations between the X-ray structures and DFT results are
likely due to the presence of intermolecular forces in the crystalline state that are absent in the
calculated structures.
3.3. Electronic absorption spectra
The electronic spectra for [Ni(LM)(PPh3)] (1) and [Ni(LC)(PPh3)] (2) in acetonitrile
were calculated using TD-DFT. The calculated absorption spectra transitions are summarized
in Table 3 in terms of their energies, wave lengths, corresponding orbital transitions and
oscillator strengths; these values are compared to the available experimental values. The
calculated absorption spectra for [Ni(LM)(PPh3)] (1) and [Ni(LC)(PPh3)] (2) are plotted with
respect to the normalized oscillator strength values in Figures 7 and 8. The weak features
with oscillator strength below 0.05 a.u were omitted. From the data presented in Table 3, one
can conclude that the experimental spectra were reproduced well by the calculations. The
lowest energy singlet excited state for [Ni(LM)(PPh3)] (1) at 444 nm and 422 nm for
[Ni(LC)(PPh3)] (2) are primarily due to the electronic transition from the highest occupied
molecular orbital to lowest unoccupied molecular orbital i.e., HOMO (H)  LUMO (L),
these values coincide well with the experimentally observed values of 429 and 431 nm.
3.4. Frontier molecular orbitals
The electronic and optical properties and chemical reactions of the complexes mainly
depend on frontier molecular orbitals [41]. Hence, the composition and energy levels of the
HOMO and LUMO orbitals may provide insight into the chemical behavior of such species;
those of 1 and 2 are depicted in Figures 9 and 10. The Ni(II) complexes 1 and 2 contain 141
and 145 occupied molecular orbitals, respectively. Figures 9 and 10 illustrate that the highest
occupied molecular orbital of 1 (and 2) is mainly delocalized in the atoms of Schiff base
ligand with some contributions from the Ni d(*) orbital. The lowest unoccupied molecular
orbital of 1 (and 2) possesses Ni–N, Ni-O, Ni-S and Ni-P  orbitals with minor contributions
from the * orbital of triphenylphosphine ligand. The energy separation between the HOMO
and LUMO for 1 and 2 is 2.793 and 2.726 eV respectively, which are in agreement with the
values obtained for other similar Ni(II) Schiff base complexes [42,43].
6

3.5. Infrared spectra
Infrared vibrational frequencies of the compounds 1 and 2 were calculated using the
DFT method described above at the optimized geometry. It is known that DFT potentials
systematically overestimate the vibrational wavenumbers. This discrepancy can be corrected
by directly scaling the calculated values with a proper factor. In this work, all the calculated
harmonic frequencies are scaled by a common factor of 0.9679 [44]. The vibrational
frequencies are then assigned on the basis of calculated wave numbers and the normal mode
analysis (Table 4). The Ni(II) complexes have 63 and 60 atoms for complex 1 and 2,
respectively. These complexes produce 183 and 174 normal vibration modes, at the
optimized structure of 1 and 2, respectively. The scaled calculated frequencies for 1 and 2
compare well with the corresponding experimental vibrational frequencies and the deviations
are typically less than 20 cm-1. The solid-state IR spectra in KBr of 1 and 2 and their
simulated spectra in the gas phase are depicted together in Figures 11 and 12, respectively,
which indicates that calculated frequencies are in good agreement with experimental
wavenumbers.
The experimental IR spectra of Ni(II) complexes contain some characteristic bands
corresponding to C–H, C=C, C=N, C–O and C–Cl stretching vibrations. In general, the
aromatic C–H stretching, in-plane bending and out-of-plane bending vibrational frequencies
appear in the range of 2900-3150, 1100-1500 and 750-1000 cm-1 respectively [45]. The
aromatic C–H stretching mode was appeared around 2853-3050 cm-1 experimentally and was
calculated in the range of 3128-3195 cm-1. In addition, the aliphatic C–H stretching mode was
observed in the experimental IR spectrum at 2956-2957 cm-1 and its calculated value is 3026-
3029 cm-1. The discrepancy in C–H stretching between experimental and calculated values is
due to the fact that intermolecular C–H•••π interactions are present in the solid state but not in
the gaseous state structure. The C–H in-plane bending vibrations that appeared usually weak
in its region 1590-1150 cm-1 are not assigned. The bands observed at 753/752, 742/743,
709/708 and 694 cm-1 in the IR spectra of complexes are assigned to the C–H out-of-plane
bending vibration for the Ni(II) complexes, which coincides very well with the calculated
wavenumbers. The azomethine C=N stretching vibration was observed at 1584 cm-1
experimentally in the Ni(II) complexes, which exactly matches with the calculated value .
The bands observed at 1622, 1573 and 1529 cm-1, which can be attributed to the C=C
stretching vibrations, were calculated at 1613, 1561 and 1509 cm-1 for complex 1. For
complex 2, experimental C=C stretching vibrations appeared at 1603, 1574 and 1519 cm-1,
7

while its calculated values are 1591, 1563 and 1500 cm-1. The phenolic C–O stretching
vibration normally appears in the region 1100-1400 cm-1. In complexes 1 and 2, it was
observed at 1327 and 1326 cm-1, respectively. Their calculated values are 1316 and 1318 cm-1
respectively for 1 and 2. For simple organic chlorine compounds, C–Cl bond absorption is in
the region 1129-480 cm-1 [46,47]. In the experimental FT-IR spectrum of complex 2, the C–
Cl absorption appeared as a shoulder at 688 cm-1. The theoretically calculated value of 671
cm-1 for C–Cl stretching of 2 by the B3LYP method correlates well with the experimental
observation.
3.6. NMR chemical shifts
In the present investigation the chemical shift for carbon and hydrogen atoms of the
title compounds were calculated using the DFT method. The chemical shielding (σ) values
for each of the nuclei were converted into the corresponding chemical shift (δ) values using
the equation:
δ = Shielding for hydrogen/carbon atom in TMS (σTMS) − σ
in which the calculated shielding value for carbon and hydrogen atoms in tetramethylsilane
(TMS) is 179.19 and 31.77 ppm, respectively as calculated at the same level of theory. The
calculated chemical shift values are summarized in Table 5 along with the experimental
values.
1
In the H NMR spectra of complexes 1 and 2, the chemical shift of the azomethine
hydrogen (CH=N) resonates at 8.8 and 9.2 ppm respectively. The chemical shift value for the
same hydrogen was calculated as 8.9 and 9.2 ppm respectively for 1 and 2. The chemical
shift for the carbon atom of the same group (CH=N) in 1 and 2 resonates at 154.25 and
13
155.96 ppm in the experimental C NMR spectra, which is predicted well by the theoretical
values (155.96 for 1 and 155.23 ppm for 2). The carbon resonances attributable to the C–O,
C–N, C–S and C–P groups are at 162.45-162.54, 149.43-149.99, 143.93-144.25 and 129.05-
129.38 ppm respectively in the 13C NMR spectra of 1 and 2. These values coincide well with
the corresponding calculated carbon chemical shift values. Similarly, the calculated chemical
shift values for the remaining carbon and hydrogen atoms agree well with the experimental
results.
4. Conclusions
Single crystal X–ray analysis of the Ni(II) complexes has revealed the presence of
square planar coordination geometry (ONSP) about nickel. To support the solid state
8

1
structure, the geometric parameters, vibrational frequencies and H & 13C NMR chemical
shifts of 1 and 2 were calculated using the density functional theory method B3LYP with 6–
311G(d,p) (main group) and LACV3P (Ni) basis sets, and compared with the experimental
results. As a consequence, it is found a good correlation between the experimental and
computed values. It is noted here that the experimental results belong to solid phase and
theoretical calculations belong to gaseous phase. In the solid state, the existence of the crystal
field along with the intermolecular interactions have connected the molecules together, which
result in the differences of bond parameters between the calculated and experimental values.
The absorption and infrared spectrum of Ni(II) complexes in acetonitrile has been modelled
by TD–DFT calculations using the same basis set. Good agreement was observed between
the computed and experimental absorption and infrared spectra.
Appendix. A Supplementary material
CCDC 873835 and CCDC 873836 contain the supplementary crystallographic data
for complexes [Ni(LM)(PPh3)] (1) and [Ni(LC)(PPh3)] (2). These data can be obtained free of
charge from www.ccdc.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
Acknowledgements
R.K. and M.M. gratefully acknowledge CSIR [01(2137)/07/EMR-II] for financial
support. We also thank SAIF, IIT-Madras for NMR measurements.
9

References
[1]
[2]
C.T. Walsh, W.H. Orme-Johnson, Biochemistry 26 (1987) 4901.
A. Sigel, H. Sigel, R.K.O. Sigel, Metal Ions in Life Sciences, Vol. 2, John Wiley &
Sons Ltd, England, 2005.
[3]
U. Ermler, W. Grabarse, S. Shima, M. Goubeaud, R.K. Thauer, Curr. Opin. Struct.
Biol. 8 (1998) 749.
[4]
[5]
[6]
G. Myagmarsuren, O.Y. Jeong, S.K. Ihm, Appl. Catal. A: Gen. 275 (2004) 271.
G.Q. Lin, R. Hong, J. Org. Chem. 66 (2001) 2877.
I.N. Houpis, J. Lee, I. Dorziotis, A. Molina, B. Reamer, R.P. Volante, P.J. Reider,
Tetrahedron 54 (1998) 1185.
[7]
[8]
[9]
E. Negishi, D.E. Van Horn, J. Am. Chem. Soc. 99 (1977) 3168.
T. Nishiguchi, A. Kurooka, K. Fukuzumi, J. Org. Chem. 39 (1974) 2403.
V. Percec, J.Y. Bae, M. Zhao, D.H. Hill, J. Org. Chem. 60 (1995) 176.
[10] T.Y. Luh, Pure Appl. Chem. 68 (1996) 105.
[11] G.M.a.J.F.H. David Barañano, Curr. Org. Chem. 1 (1997) 287.
[12] H.T. Sugimura, Chem. Lett. (1984) 1505.
[13] N. Ajellal, M.C.A. Kuhn, A.D.G. Boff, M. Hörner, C.M. Thomas, J.F. Carpentier,
O.L. Casagrande, Organometallics 25 (2006) 1213.
[14] E.M. Jouad, A. Riou, M. Allain, M.A. Khan, G.M. Bouet, Polyhedron 20 (2001) 67.
[15] N. Goswami, D.M. Eichhorn, Inorg. Chem. 38 (1999) 4329.
[16] T.A. Huber, F. Belanger-Gariepy, D. Zargarian, Organometallics 14 (1995) 4997.
[17] A.K. List, M.R. Smith, G.L. Hillhouse, Organometallics 10 (1991) 361.
[18] C. Bianchini, C.A. Ghlardi, A. Meli, S. Midollini, A. Orlandini, J. Chem. Soc. Chem.
Commun. (1983) 753.
[19] M. Muthu Tamizh, K. Mereiter, K. Kirchner, B.R. Bhat, R. Karvembu, Polyhedron
28 (2009) 2157.
[20] R. Prabhakaran, R. Karvembu, T. Hashimoto, K. Shimizu, K. Natarajan, Inorg. Chim.
Acta 358 (2005) 2093.
10

[21] M. Muthu Tamizh, B. Varghese, A. Endo, R. Karvembu, Spectrochim. Acta A 77
(2010) 411.
[22] S. Guveli, N. Ozdemir, T. Bal-Demirci, B. Ulkuseven, M. Dincer, O. Andac,
Polyhedron 29 (2010) 2393.
[23] B. Ulkuseven, T. Bal-Demirci, M. Akkurt, S.P. Yalcin, O. Buyukgungor, Polyhedron
27 (2008) 3646.
[24] S. Guveli, B. Ulkuseven, Polyhedron 30 (2011) 1385.
[25] P.X. Garcia-Reynaldos, S. Hernandez-Ortega, R.A. Toscano, J. Valdes-Martinez,
Supramol. Chem. 19 (2007) 613.
[26] R. Prabhakaran, P. Kalaivani, R. Huang, M. Sieger, W. Kaim, P. Viswanathamurthi,
F. Dallemer, K. Natarajan, Inorg. Chim. Acta 376 (2011) 317.
[27] G.M. Sheldrick, Acta Cryst 64A (2008) 112.
[28] G.M. Sheldrick, Bruker AXS Inc., Madison, WI, 2001.
[29] L.J. Farrugia, J. Appl. Cryst. 32 (1999) 837.
[30] P. van der Sluis, A.L. Spek, Acta Cryst. 46A (1990) 194.
[31] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
[32] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[33] P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 299.
[34] Jaguar 6.5, V Edition, Schroedinger, LLC, New York, 2005.
[35] R. Ditchfield, Mol. Phys. 27 (1974) 789.
[36] K. Wolinski, J.F. Hinton, P. Pulay, J. Am. Chem. Soc. 112 (1990) 8251.
[37] S. Miertus, E. Scrocco, J. Tomasi, J. Chem. Phys. 55 (1981) 117.
[38] V. Barone, M. Cossi, J. Tomasi, J. Chem. Phys. 107 (1997) 3210.
[39] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
G. Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M. Caricato, X.
Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg, M. Hada,
M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O.
Kitao, H. Nakai, T. Vreven, J.A. Montgomery, J.E. Peralta, F. Ogliaro, M. Bearpark,
11

J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, R. Kobayashi, J. Normand, K.
Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M. Cossi, N. Rega,
J.M. Millam, M. Klene, J.E. Knox, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R.
Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W.
Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth, P. Salvador, J.J.
Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman, J.V. Ortiz, J.
Cioslowski, D.J. Fox, Gaussian 09, Revision B.01, Wallingford CT, 2009.
[40] I. Dance, M. Scudder, J. Chem. Soc. Dalton Trans. (2000) 1579.
[41] I. Fleming, Frontier Orbitals and Organic Chemical Reactions, Wiley, London, 1976.
[42] P.J. Blower, J.R. Dilworth, R.I. Maurer, G.D. Mullen, C.A. Reynolds, Y. Zheng, J.
Inorg. Biochem. 85 (2001) 15.
[43] S. Guveli, N. Ozdemir, T. Bal-Demirci, B. Ulkuseven, M. Dincer, O. Andac,
Polyhedron 29 (2010) 2393.
[44] M.P. Andersson, P. Uvdal, J. Phys. Chem. A 109 (2005) 2937.
[45] C. Albayrak, G. Kastas, M. Odabasoglu, R. Frank, Spectrochim. Acta A 81 (2011) 72.
[46] A.U. Rani, N. Sundaraganesan, M. Kurt, M. Cinar, M. Karabacak, Spectrochim. Acta
A 75 (2010) 1523.
[47] V.K. Rastogi, M.A. Palafox, R.P. Tanwar, L. Mittal, Spectrochim. Acta A 58 (2002)
1987.
12

Table 1
Crystal data, data collection and structure refinement parameters.
Parameters
[Ni(LM)(PPh3)] (1)
[Ni(LC)(PPh3)] (2)
Empirical formula
C32H26NNiOPS
C31H23ClNNiOPS
Formula weight
Colour
562.28
582.69
Dark brown
Block
Dark brown
Block
Habit
Crystal dimension (mm)
Crystal system
Space group
a (Å)
0.400.200.10
Triclinic
P-1
0.500.400.30
Triclinic
P-1
8.9044(7)
12.0033(9)
14.1993(10)
72.7140(10)
83.2850(10)
70.7540(10)
1367.81(18)
2
9.1026(14)
9.8987(15)
15.267(2)
101.3730(10)
96.772(2)
98.2230(10)
1319.5(3)
2
b (Å)
c (Å)
(°)
(°)
(°)
Volume (Å3)
Z
Temperature
DC (Mg/m3)
Abs. coefficient (mm-1)
F000
173(2)K
1.365
173(2)K
1.467
0.870
1.002
584
600
0.71073
0.71073
1.38–27.50
(Mo Kα) (Å)
range (deg)
Scan type
Index ranges
1.50–27.50
, 
, 
-11≤h≤11,
-15≤k≤15,
-18≤l≤18
-11≤h≤11,
-12≤k≤12,
-19≤l≤19
Reflections collected/unique
Rint
15351/6041
0.0268
14934/5854
0.0173
Refinement method
Diffractometer
Full-matrix least-squares on F2
Bruker APEX CCD
Absorption correction
Multi-scan SADABS
13

Final R indices R1/wR2[I>2s(I)]
0.0385/0.1074
0.0443/0.1122
1.109
0.0311/0.0839
0.0351/0.0918
1.106
R1/wR2 (all data)
Goodness-of-fit (GOF) on F2
max and min (eÅ-3)
0.617 and -0.401
6041/0/338
0.585 and -0.558
5854/0/338
Data/restraints/parameters
14

Table 2
Experimental and optimized geometrical parameters of 1 and 2.
Structural parameters
[Ni(LM)(PPh3)] (1)
XRD DFT
[Ni(LC)(PPh3)] (2)
XRD
DFT
Bond length (Å)
Ni(1)-O(1)a
1.8545(15) 1.870
1.9178(18) 1.925
1.8422(19)
1.9155(2)
2.1359(5)
2.2123(5)
1.298(2)
1.880
Ni(1)-N(1)
1.927
2.193
2.283
1.296
1.306
1.425
1.760
1.841
1.840
1.845
1.421
1.426
1.403
1.764
0.028
0.070
Ni(1)-S(1)
2.1515(6)
2.2240(6)
1.304(3)
1.302(3)
1.433(3)
1.754(2)
1.821(2)
1.826(2)
1.832(2)
1.413(3)
1.418(3)
1.393(3)
1.511(3)
2.211
2.293
1.297
1.308
1.425
1.762
1.846
1.841
1.844
1.422
1.427
1.404
1.509
0.026
0.069
Ni(1)-P(1)
O(1)-C(1)
N(1)-C(7)
1. 305(2)
1. 426(2)
1.754(18)
1.823(17)
1.817(18)
1.823(17)
1.407(3)
N(1)-C(8)
S(1)-C(13)
P(1)-C(14)
P(1)-C(20)
P(1)-C(26)
C(1)-C(6)
C(6)-C(7)
1.425(2)
C(8)-C(13)
1.396(2)
C(4)-C(4’)/Cl(1)
RMSDb
Max. diff.c
1.742(19)
Bond angle ()
O(1)-Ni(1)-S(1)
N(1)-Ni(1)-P(1)
O(1)-Ni(1)-N(1)
N(1)-Ni(1)-S(1)
S(1)-Ni(1)-P(1)
O(1)-Ni(1)-P(1)
Ni(1)-O(1)-C(1)
Ni(1)-N(1)-C(7)
Ni(1)-N(1)-C(8)
Ni(1)-S(1)-C(13)
175.00(5)
176.14(6)
95.37(7)
88.67(6)
88.25(5)
87.82(5)
174.7
174.9
94.9
88.5
88.6
87.5
173.88(5)
176.44(4)
95.16(6)
176.1
177.3
94.8
89
89.73(4)
92.65(2)
92.1
84.1
128.1
122.2
118
82.64(4)
128.17(14) 128.1
122.72(15) 122.4
118.50(14) 118.1
128.74(12)
123.03(12)
117.62(11)
98.24(6)
98.90(8)
97.2
97.4
15

Table 2 Continued
Ni(1)-P(1)-C(14)
Ni(1)-P(1)-C(20)
Ni(1)-P(1)-C(26)
C(14)-P(1)-C(20)
C(14)-P(1)-C(26)
C(20)-P(1)-C(26)
C(1)-C(6)-C(7)
114.08(7)
114.01(7)
116.62(7)
111.4
114.9
116.4
112.70(6)
119.75(6)
108.44(6)
105.64(8)
104.97(8)
104.05(8)
122.15(16)
127.13(16)
119.34(14)
118.60(13)
114.2
119.3
108.2
106.3
104.7
103.1
122.4
127.7
115.9
119
103.96(10) 105.7
103.42(10) 104.1
103.23(10) 103.2
122.40(2)
127.60(2)
122.1
127.8
C(6)-C(7)-N(1)
C(7)-N(1)-C(8)
118.69(10) 116.1
118.62(17) 118.8
1.095
S(1)-C(13)-C(8)
RMSDb
1.66
Max. diff.c
2.68
3.44
Dihedral angle ( )
Ni(1)-O(1)-C(1)-C(6)
Ni(1)-S(1)-C(13)-C(8)
O(1)-Ni(1)-S(1)-C(13)
N(1)-Ni(1)-S(1)-C(13)
N(1)-Ni(1)-O(1)-C(1)
N(1)-Ni(1)-P(1)-C(14)
N(1)-Ni(1)-P(1)-C(20)
N(1)-Ni(1)-P(1)-C(26)
-2.5
2.1
3.3
6.6
2.7
5.7
-0.5
2.5
-146.7
-2.7
-138.8
-8.4
145.6
2.6
-168.8
-5.6
-0.6
-10.3
-11.4
108.7
-129.3
-1.9
-12.4
9.7
-43.2
76
15.4
130.1
-105.8
127.8
-109.7
-163.8
a for labeling of atoms see Figures 1 and 2.
b root mean square deviation between the bond lengths or bond angles computed by
the theoretical methods and those obtained from X-ray diffraction.
c
maximum differences between the bond lengths or bond angles computed by the
theoretical methods and those obtained from X-ray diffraction.
16

Table 3
Experimental and theoretical optical absorption energies (in eV and nm) along with orbital
transitions and calculated oscillator strength.
Experimental
Assignment
Complex
Orbital
Energies
Oscillator
Strength (a.u)
0.05
Transitions eV
nm
429
dd
H→L
2.79
444
400
1
LMCT
H-1→L
H-1→L+1
H-2→L
H-5→L
H-4→L
H-5→L+1
H→L+6
H-1→L+8
H→L+9
3.1
0.17
3.89
4.23
321
293
0.13
0.13
267
253
n*
*
4.5
276
252
0.13
0.17
4.91
216
431
*
dd
H-1→L+10 5.18
239
422
400
0.14
0.06
0.16
H→L
2.94
3.1
2
LMCT
H-1→L
H-1→L+1
H→L+2
H→L+4
H→L+6
H→L+7
H→L+10
3.92
4.27
4.52
317
290
274
0.06
0.09
0.14
267
253
n*
*
4.92
252
236
0.17
0.15
216
*
H-1→L+10 5.25
17

Table 4
Comparison of the experimental and calculated vibrational frequencies (cm-1).
[Ni(LM)(PPh3)] (1)
Calc.(s)b Calc.
[Ni(LC)(PPh3)] (2)
Calc.(s) b Calc.
Assignmenta
ring(C-H)
Exp.
3046
3009
2923
2853
1622
1584
1573
1529
1461
1436
1370
1327
1248
950
Exp.
3049
2956
2925
2851
1603
1583
1574
1519
1456
1437
1372
1326
1242
937
3090
3043
2919
3026
1613
1582
1561
1509
1446
1446
1366
1316
1234
933
3193
3144
3016
3126
1666
1634
1613
1559
1493
1468
1412
1360
1275
974
3085
3195
3186

3029
1591
1579
1563
1500
1439
1439
1366
1309
1225
920
3128
1644
1631
1614
1549
1486
1441
1412
1353
1266
952
(C-H)aliphatic
(C=C) + (C=N)
(C=C) + ring(C-H)
(C=C) + ring(C-H)
ring(C-H)
(C-H)
(C-H)
(C-O)
(C-N)
δring(C-H)
742
738
762
753
742
766
ring(C-H)
694
688
711
694
691
714
ring(C-H)(PPh3)
-
-
690
671
694
(C-Cl)
a , stretching; , scissoring; , rocking; , wagging. δ, twisting.
b scaled.
18

Table 5
Experimental and theoretical 13C and 1H isotropic chemical shifts (ppm) for the title compounds.
Atom
[Ni(LM)(PPh3)]
[Ni(LC)(PPh3)]
Atom [Ni(LM)(PPh3)]
Expt.
[Ni(LC)(PPh3)]
Expt.
Theory
Expt.
Theory
Theory
---
Expt.
Theory
---
C1
162.45
121.35
135.95
124.23
20.23
167.11
123.00
135.94
124.26
17.43
162.54 165.72
123.08 123.10
133.94 134.80
119.90 128.31
---
---
---
C2
H2
H3
---
6.33 (d, J = 8.5 Hz, 1H)
6.90 - 7.05 (m, 3H)
---
6.72
6.93
---
6.31 (d, J = 9 Hz, 1H)
6.24
6.78
---
C3
7.07 (dd, J = 9, 3 Hz, 1H)
C4
---
C4'
C5
---
---
H4'
H5
---
2.25 (s, 3H)
2.11
6.87
---
---
---
132.73
118.84
154.25
149.99
114.76
121.83
126.50
128.62
143.89
133.70
119.96
155.96
152.61
113.07
120.00
126.17
130.32
151.37
131.80 133.21
119.54 120.43
153.45 155.23
149.43 151.41
114.93 113.24
122.02 120.07
127.06 127.16
128.67 130.62
144.30 153.42
7.21 (br. s., 1H)
---
Overlapped with Hm
---
6.94
---
C6
C7
H7
---
8.82 (d, J = 10 Hz, 1H)
---
8.89
---
8.79 (d, J = 10 Hz, 1H)
---
9.22
---
C8
C9
H9
H10
H11
H12
---
7.67 (d, J = 7.5 Hz, 1H)
Overlapped with H3
Overlapped with H3
7.35 (d, J = 7 Hz, 1H)
---
7.35
6.69
6.75
7.14
---
7.66 (d, J = 8 Hz, 1H)
6.94 - 7.04 (m, 2H)
Overlapped with H10
7.35 (dd, J = 7.5 Hz, 1H)
---
7.30
6.67
6.76
7.13
---
C10
C11
C12
C13
19

Table 5 Continued
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
C25
C26
C27
C28
C29
C30
C31
129.38
134.79
128.13
130.54
128.13
134.79
129.38
134.79
128.13
130.54
128.13
134.79
129.38
134.79
128.13
130.54
128.13
134.79
136.38
142.14
129.04
131.22
127.64
135.62
134.40
138.86
128.23
131.25
127.80
133.41
134.80
134.05
127.54
130.08
126.55
140.31
129.05
134.73
128.21
130.68
128.13
134.79
129.05
134.79
128.13
130.54
128.13
134.79
129.05
134.79
128.13
130.54
128.13
134.79
134.72
140.90
128.95
131.42
127.78
136.24
134.77
133.93
127.52
130.43
127.87
136.70
136.07
139.07
128.74
130.73
128.51
133.21
---
---
---
---
---
H15
H16
H17
H18
H19
---
7.77  7.93 (m, 6H)
7.37 - 7.44 (m, 6H)
7.44 - 7.53 (m, 3H)
7.37 - 7.44 (m, 6H)
7.77  7.93 (m, 6H)
---
9.98
7.57
7.47
7.31
7.05
---
7.78 - 7.88 (m, 6H)
7.38 - 7.45 (m, 7H)
7.46 - 7.53 (m, 3H)
7.37 - 7.44 (m, 7H)
7.78 - 7.88 (m, 6H)
---
9.22
7.49
7.46
7.32
7.05
---
H21
H22
H23
H24
H25
---
7.77  7.93 (m, 6H)
7.37 - 7.44 (m, 6H)
7.44 - 7.53 (m, 3H)
7.37 - 7.44 (m, 6H)
7.77 - 7.93 (m, 6H)
---
8.7
7.78 - 7.88 (m, 6H)
7.37 - 7.44 (m, 7H)
7.46 - 7.53 (m, 3H)
7.37 - 7.44 (m, 7H)
7.78 - 7.88 (m, 6H)
---
6.70
7.15
7.36
7.40
7.58
---
7.59
7.45
7.21
6.95
---
H27
H28
H29
H30
H31
7.77 - 7.93 (m, 6H)
7.37 - 7.44 (m, 6H)
7.44 - 7.53 (m, 3H)
7.37 - 7.44 (m, 6H)
7.77  7.93 (m, 6H)
6.77
7.21
7.40
7.45
7.78
7.78 - 7.88 (m, 6H)
7.37 - 7.44 (m, 7H)
7.46 - 7.53 (m, 3H)
7.37 - 7.44 (m, 7H)
7.78 - 7.88 (m, 6H)
9.12
7.50
7.41
7.31
7.15
20

A
B
Fig. 1. Molecular geometry of [Ni(LM)(PPh3)] from X-ray crystal structure (A) and DFT
calculation (B) (where C = gray, H = white, Ni = lime green, N = blue, O = red, S = yellow, P
= purple).
A
B
Fig. 2. Molecular geometry of [Ni(LC)(PPh3)] from X-ray crystal structure (A) and DFT
calculation (B) (where C = gray, H = white, Ni = blue, N = lime green, O = red, S = yellow,
Cl = green, P = purple).
21

Fig. 3. Schematic drawing of the crystal packing of [Ni(LM)(PPh3)] (1) showing the offset π-
π stacking; the molecular planes are oriented approximately parallel to the crystallographic
[223] direction and the complexes stack along the a-axis. Hydrogen atoms omitted for
clarity.
22

Fig. 4. Schematic drawing of the crystal packing of [Ni(LC)(PPh3)] (2) showing the offset π-
π stacking that occurs roughly parallel to the a-axis; the molecular planes are oriented
approximately in the cystallographic [5-53] direction and featuring alternating inter-plane
distances of 3.426(6) and 3.447(6) Å. Adjacent molecules with the larger inter-plane
separation also feature Ni···Cl contacts of 3.6720(4)Å. Hydrogen atoms omitted for clarity.
23

Fig. 5. Atom-by-atom superimposition of the structures calculated (blue) over the X-ray
structure (lime green) for [Ni(LM)(PPh3)]. Hydrogen atoms omitted for clarity.
Fig. 6. Atom-by-atom superimposition of the structures calculated (red) over the X-ray
structure (lime green) for [Ni(LC)(PPh3)]. Hydrogen atoms omitted for clarity.
24

Fig. 7. UV–Vis spectrum for [Ni(LM)(PPh3)] (1) in acetonitrile. Inset shows simulated
absorption spectrum based on TD-DFT calculations.
Fig. 8. UV–Vis spectrum for [Ni(LC)(PPh3)] (2) in acetonitrile. Inset shows simulated
absorption spectrum based on TD-DFT calculations.
25

HOMO
LUMO
Fig. 9. HOMO, LUMO plots of [Ni(LM)(PPh3)] (1).
HOMO
LUMO
Fig. 10. HOMO, LUMO plots of [Ni(LC)(PPh3)] (2).
26

Fig. 11. FT-IR spectrum (KBr) and calculated spectrum of [Ni(LM)(PPh3)] (1) in the gas
phase using B3LYP/6-311G(d,p).[LACV3P for Ni atom] method.
Fig. 12. FT-IR spectrum (KBr) and calculated spectrum of [Ni(LC)(PPh3)] (2)in the gas
phase using B3LYP/6-311G(d,p).[LACV3P for Ni atom] method.
27

Highlights (for review)
 Structure of two complexes of the formula [Ni(L)(PPh3)] (L = tridentate Schiff base)
were studied by X-ray crystallography
 DFT reproduced the calculated structural results
 The UV, IR and NMR spectra of the complexes were calculated using experimental as
well as theoretical methods
 Theoretical spectral data coincide well with the experimental data