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Journal of Molecular Structure 1185 (2019) 212e218
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DFT studies of disubstituted diphenyldithiophosphates of nickel(II): Structural and some spectral parameters Sandeep Kumar a, Anu Radha a, Mandeep Kour a, Rakesh Kumar b, Abdelkader Chouaih c, Sushil K. Pandey a, * a b c
Department of Chemistry, University of Jammu, Jammu, 180006, India Department of Chemistry, DAV University, Jalandhar, 144012, India Laboratory of Technology and Solid Properties (LTPS), Abdelhamid Ibn Badis University, BP 227, Mostaganem, 27000, Algeria
a r t i c l e i n f o
a b s t r a c t
Article history: Received 9 November 2018 Received in revised form 3 February 2019 Accepted 25 February 2019 Available online 27 February 2019
Three nickel(II) disubstituted diphenyldithiophosphate complexes corresponding to [{(ArO)2PS2}2Ni] [Ar ¼ 2,4-(CH3)2C6H3 (1), 3,5-(CH3)2C6H3 (2) and 4-Cl-3-CH3C6H3 (3)] were theoretically compared to the experimentally reported spectroscopic and X-ray diffraction data. The complexes were computationally studied by using density functional theory (DFT) in its hybrid form B3LYP. The complexes were optimized to calculate the different parameters, vibrational bands and NMR theoretically. The conformational analysis has been performed to determine the stable conformers of complexes. In theses complexes the ligands are coordinated to the nickel metal ion as a bidentate chelating agent via the two thiolate sulfur atoms leading to square planar geometry. The energy gaps of frontier orbital (HOMOeLUMO) have also been calculated along with the global reactivity descriptors quantum parameters. The calculated geometric and spectral results reproduced the experimental data with well agreement. Theoretical calculated molecular orbitals (HOMOeLUMO) and their energies have been calculated that suggest charge transfer occurs within the complexes. The electrophilic and nucleophilic sites are theoretically evaluated by molecular electrostatic potential. © 2019 Elsevier B.V. All rights reserved.
Keywords: Diphenyldithiophosphate DFT HOMO-LUMO
1. Introduction Dialkyldithiophosphoric acids [(RO)2PS2H] (R ¼ Me, Et, Prn, PriO, Bun, But or Ph) and alkylenedithiophosphoric acids [OGOPS2H] (G ¼ 1, 2- and 1, 3- glycols) and their metal and metalloid derivatives are well known [1e6]. The interesting bonding possibilities of these ligands have attracted considerable attention. The chemistry of metal-sulfur bond has been reviewed by several researchers during last four decades [1e7] highlighting various aspects of the bonding modes, in relevance to biochemical, industrial, agricultural and analytical applications. The sulfur containing compounds also shows nonlinear optical (NLO) effects [8,9]. The biological aspect of dithiophosphates has been well established in the rapidly growing field of phosphorus-sulfur chemistry [10,11]. The dithiophosphate ligands and their metal derivatives have been screened for in vitro antifungal and antibacterial activities [12e15]. The results are quite promising, so these complexes are candidates
* Corresponding author. E-mail address: [email protected] (S.K. Pandey). https://doi.org/10.1016/j.molstruc.2019.02.105 0022-2860/© 2019 Elsevier B.V. All rights reserved.
for exploration as specific antifungal and antibacterial drugs. The in vitro cytotoxic investigation of some titanium dithiophosphates complexes against the cultivated human cell has also been reported [16]. The dithiophosphates have received much attention for their extensive applications as biocides [17], analytical reagents [18], antiwear and antioxidant additives in motor oils [19]. In the hybrid form B3LYP density functional theory is the most accurate and efficient computational method for the quantum chemical modeling of coordination compounds [20,21]. The various properties of transition metal compounds can be computed and interpreted with DFT than ab intio and semi-empirical quantumchemical method. These computations are often based on known structural data [22]. The literature survey reveals only few reports as theoretical calculations on the structural and vibrational properties of dithiophosphates [23e28]. To the best of our knowledge, reports on theoretical calculations of ditolyl/diphenyldithiophosphates of nickel(II) have not been described so far. In order to comprehend and understand the experimental studies and to provide more insight into molecular parameters and vibrational spectra of the compounds, a comparison of computed structural and spectroscopic data with the previously reported experimental
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(crystallographic and spectroscopic) results has been investigated for the title compounds. The present work describes the crystal structures and DFT analyses of previously reported diphenyldithiophosphates of nickel(II) prepared in our laboratory [29]. In addition, HOMO-LUMO analysis, global chemical reactivity descriptors and molecular electrostatic potential investigation were performed with the same level of theory. The molecular electrostatic potential analysis was used to find the reactive sites of the studied compounds. 2. Results and discussion The quantum chemical DFT method is used to model the complexes 1e3 satisfactory. DFT calculations have been performed to get an insight in the molecular structures and explain bonding nature and spectral properties of complexes: [{2,4(CH3)2C6H3O}2PS2]2Ni (1), [{3,5-(CH3)2C6H3O}2PS2]2Ni (2) and [(4Cl-3-CH3C6H3O)2PS2]2Ni (3) and their comparison with experimental data is carried out [29]. The Ni(II) complexes are optimized, structural parameters are calculated. 2.1. Geometrical structures and conformational analysis According to the DFT calculations and reported [29] single crystal X-ray structures of the complexes 1e3 the nickel atom is four-coordinated by four sulfur atoms from two acyclic dithiophosphato ligands and bonded in bidentate chelating fashion to Table 1 Selected experimental and calculated bond lengths (Å) and angles (o) for complex 1.
a
Bond lengths/Bond angles
Experimental
Calculated
Deviation
Ni1eS1 Ni1eS2 P1eS1 P1eS2 P1eO1 P1eO2 S1eNi1eS1i S2eNi1eS2i S1eNi1eS2i S1eNi1eS2 S1eP1eS2 S1eP1eO1 S1eP1eO2 S2eP1eO1 S2eP1eO2 O1eP1eO2
2.229 (11) 2.229 (11) 1.984 (13) 1.984 (12) 1.583 (18) 1.580 (2) 180.00 (4) 180.00 (4) 91.96 (4) 88.04 (4) 102.65 (5) 115.52 (9) 115.74 (9) 115.21 (8) 115.73 (9) 92.85 (10)
2.228 2.229 1.984 1.984 1.579 1.583 180.00 180.00 91.98 88.02 102.61 115.61 115.52 115.73 115.23 92.85
0.001 0 0 0 0.004 0.003 0 0 0.02 0.02 0.04 0.09 0.22 0.52 0.5 0
Symmetry transformations used to generate equivalent atoms: (i) ex, ey, ez.
Table 2 Selected experimental and calculated bond lengths (Å) and angles (o) for complex 2.
Fig. 1. Optimized structures of (a) [{2,4-(CH3)2C6H3O}2PS2]2Ni (1); (b) [{3,5(CH3)2C6H3O}2PS2]2Ni (2) and (c) [(4-Cl-3-CH3C6H3O)2PS2]2Ni (3).
a
Bond lengths/Bond angles
Experimental
Calculated
Deviation
Ni1eS1 Ni1eS2 P1eS1 P1eS2 P1eO1 P1eO2 S1eNi1eS1ii S2eNi1eS2ii S1ii eNi1eS2 S1eNi1eS2 O1eP1eS1 O2eP1eS1 O1eP1eS2ii O2eP1eS2ii S2ii eP1eS1 O2eP1eO1
2.2305 (6) 2.2370 (6) 1.9778 (8) 1.9770 (8) 1.5880 (18) 1.5813 (17) 180.00 (3) 180.00 (18) 88.79 (2) 91.21 (2) 114.20 (8) 114.19 (7) 115.02 (7) 109.98 (7) 104.43 (4) 99.34 (9)
2.245 2.239 1.991 1.992 1.607 1.599 179.98 179.97 91.04 91.05 115.15 110.06 114.31 114.38 104.08 99.19
0.015 0.002 0.014 0.015 0.019 0.086 0.02 0.03 2.25 0.16 0.95 4.13 0.71 4.4 0.35 0.15
Symmetry transformations used to generate equivalent atoms: (ii) 1ex, ey, ez.
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Table 3 Selected experimental and calculated bond lengths (Å) and angles (o) for complex 3. Bond lengths/Bond angles
Experimental
Calculated
Deviation
Ni2eS1 Ni2eS2 S1eP1 S2eP1 P1eO1 P1eO2 S1eNi2eS1ii S2eNi2eS2ii S1eNi2eS2 S1eNi2eS2ii O1eP1eO2 S2eP1eO2 S2eP1eO1 S1eP1eO2 S1eP1eO1 S1eP1eS2
2.2396 (5) 2.2438 (5) 1.9723 (7) 1.9776 (7) 1.5855 (14) 1.5917 (14) 180.00 (2) 180.00 (2) 89.142 (18) 90.86 (18) 98.78 (8) 113.95 (6) 115.38 (6) 114.37 (6) 108.91 (6) 105.61 (3)
2.239 2.243 1.977 1.978 1.586 1.591 179.97 179.98 89.15 90.86 98.74 114.37 115.40 113.93 108.90 105.63
0.0006 0.0008 0.0047 0.0004 0.0005 0.0007 0.03 0.02 0.008 0 0.04 0.42 0.02 0.44 0.01 0.02
form a spirocyclic ring leading to the square planar geometry. It is appropriate here to correlate the structural parameters obtained from the crystal structure studies with the computational data. Fig. 1 shows the optimized molecular structures for complexes 1e3. Comparisons of selected bond lengths and bond angles are given in Tables 1e3. It is important to mention here that the optimized structures are close to the experimental ones. With regards to bond lengths the maximum deviations is observed in the P1dO2 (0.086 Å) bond length of the complex 2, while for bond angles the maximum deviation is shown by the bond angle O2eP1eS1 (4.13 ) and of complex 2. The small discrepancies in bond lengths and bond angles are attributable to packing interactions within the lattice, which are not modeled during computational studies. The conformational analysis has been performed to determine the stable conformers of complexes 1e3 by using potential energy surface (PES) scan analysis with C1eO1eP1eO2 dihedral angle
aSymmetry transformations used to generate equivalent atoms: (ii) 1ex, ey, ez.
Fig. 2. Conformations with relative energies obtained at DFT/B3LYP level for (a) Complex 1, (b) Complex 2 and (c) Complex 3.
S. Kumar et al. / Journal of Molecular Structure 1185 (2019) 212e218
from 65 to 245 . The dihedral angle C1eO1eP1eO2 for the studied complexes is the relevant coordinate for conformational stability within the molecules. This dihedral angle was chosen by considering that the compounds contain two symmetric fragments in regards to the metal atom. The conformational analysis of complexes 1e3 was performed by using B3LYP level with 6-31G(d,p) and LANL2DZ bases sets. During the PES scan, all the geometrical parameters were simultaneously relaxed, while the dihedral angle C1eO1eP1eO2 was allowed to vary in the steps of 10 . The minimum and maximum energy conformers obtained from conformational analysis are given in Fig. 2.
215
Table 5 1 H spectral data of complexes 1e3 (in ppm). Complex
Assignments
Experimental
Calculated
1.
(s, 2eCH3) (s, 4eCH3) (d, H6) (d, H5) (s, H3) (s, 3,5e(CH3)2) (s, H2,6) (s, H4) (s, 3eCH3) (d, H6) (s, H2) (d, 4H, H3)
2.30 2.36 6.87 7.07 7.37 2.35 7.08 6.80 2.27 7.13 7.18 7.31
2.38, 2.48, 8.13 7.29 7.20 2.34, 6.23, 6.84 1.85, 6.94 6.91 6.26
2.
3.
2.2. Spectral data
1.56, 2.49 2.03, 2.02
2.14, 1.87, 2.36, 2.18, 1.85 6.90 2.38, 2.34, 2.31, 1.56, 2.39
s ¼ singlet, d ¼ doublet.
Vibrational spectroscopy has been widely used as a standard tool for structural characterization of molecular systems by DFT calculations. It is found that the calculated frequencies are close to the experimental values. Experimental and calculated vibration frequencies along with corresponding vibrational assignments are given in Table 4. The vibrational frequencies for optimized molecules were calculated at the same level of the theory. The theoretical IR spectra for the complexes 1e3 are shown in Fig. S1 (see electronic supplementary information). In the experimental spectra of the complexes 1e3, the appearance of new bands in the region 381e370 cm1 can be attributed to [vNiS] bands. These bands were calculated in the region 372353 cm1. Diphenyldithiophosphate moiety bands [vPS]asym and [vPS]sym are observed in the regions 704650 and 635557 cm1, while the corresponding theoretical values are in the regions 706633 and 658562 cm1, respectively. The NMR spectra were predicted for complexes 1e3 using B3LYP/6-31G**/DFT method and the spectral data was compared with experimental data (Fig S2-S5 and Scheme S1) reported in literature [29]. From 1H NMR results reported in Table 5, it can be concluded that the B3LYP functional with GIAO method and 631G(d,p) basis set predicted well the 1H NMR spectra. Some differences between experimental and theoretical 1H NMR results are due to the intermolecular interactions involving the hydrogen atoms and the environment of each H-atom. The computed NMR spectral data is fairly in agreement with experimental data (Tables 5 and 6). Small deviations are due to the fact that any type of lattice interactions are not modeled in theoretically computed structures. 2.3. HOMO-LUMO analysis and chemical reactivity The Frontier Molecular Orbitals (FMOs) play a crucial role on the reactivity of any chemical system. For instance, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) show the ability of donating and accepting an electron in any molecule, respectively [30]. Several chemical properties of a molecule including chemical hardness, chemical potential, reactivity, kinetic stability, optical polarizability, chemical
Table 6 13 C NMR spectral data of the complexes 1e3 (in ppm). Complex
Assignments
Experimental
Calculated
1.
(2eCH3), (4eCH3) C1 C2 C3 C4 C5 C6 (3,5e(CH3)2) C1 C2 C3 C4 C5 C6 (3eCH3) C1 C2 C3 C4 C5 C6
17.3, 20.8 146.8 127.4 135.4 132.1 129.9 120.8 21.3 149.6 118.9 139.5 127.7 139.5 118.9 19.7 151.3 123.9 135.4 127.1 128.7 120.6
19.52, 21.85 142.56 128.28 127.51 131.75 122.85 117.53 22.33, 22.27 150.16 115.46 136.21 124.02 136.07 115.17 22.16, 21.97 147.92 120.00 116.28 146.30 121.22 115.89
2.
3.
softness, electronegativity, electrophilicity etc. can be explained by FMOs. The molecules having a large energy gap are known as hard, and those having a small energy gap are known as soft molecules. Soft molecules are more polarizable than the hard ones because they need only small amounts of energy for excitation [31]. Furthermore, the charge transfer interactions within a molecule can be deduced from the HOMO and LUMO energy gap. On the other hand, the stability of a molecule is related to hardness, which indicates that the molecule with low energy gap means high reactivity. The energy values HOMO and LUMO calculated at the B3LYP/6-31G(d,p) level are given in Table 7. In complexes 1e3, LUMO and HOMO (Fig. 3) are mainly distributed over the Ni, O and S atoms. The energy gap between the HOMO and the LUMO is a critical parameter in determining molecular electrical transport
Table 4 Selected experimental and calculated IR vibrational frequencies (cm1) for complexes 1e3. Assignment
[v(P)eOeC] [vPO(C)] [vPS]asym [vPS]sym [vNiS]
Complex 1
Complex 2
Complex 3
Experimental
Theoretical
Experimental
Theoretical
Experimental
Theoretical
1105 s 869 s 650 s 572 m 370 w
1116 867 633 562 372
1101 s 858 s 654 s 557 m 371 w
1116 867 633 562 372
1157 s 971 s 704 s 635 m 381 w
1154 990 706 658 353
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Table 7 Electronic properties of different conformers for complexes 1e3. Parameters
Complex 1
Dihedral angle ( ) EHOMO (eV) ELUMO (ev) Gap (eV)
Complex 2
Complex 3
C1
C2
C3
C1
C2
C3
C1
C2
C3
130.78 6.07 2.57 3.50
190.78 6.10 2.57 3.53
250.78 6.10 2.58 3.52
116.60 6.00 2.51 3.49
166.60 6.02 2.52 3.50
243.39 6.00 2.52 3.48
116.94 6.41 2.91 3.50
176.93 6.41 2.90 3.51
236.93 6.42 2.92 3.50
C1, C2 and C3 are conformer 1, conformer 2 and conformer 3, respectively.
Fig. 3. Frontier molecular orbital surfaces and energy gap for (a) [{2,4-(CH3)2C6H3O}2PS2]2Ni (1); (b) [{3,5-(CH3)2C6H3O}2PS2]2Ni (2) and (c) [(4-Cl-3-CH3C6H3O)2PS2]2Ni (3).
properties. The values of the energy gap for compounds 1, 2 and 3 were found to be 3.768, 3.685 and 3.702 eV, respectively. The results indicate that the studied compounds have good kinetic stability. In order to highlight the effect of complex conformers to the electronic properties, HOMO, LUMO and the gap energies are computed using the same level of theory as described above. The obtained results are summarized in Table 7. No change was observed for all the complexes which confirm that the calculated geometries are more stable. Recognizing the relationship between strength of structure and chemical reactivity can be achieved by the determination of global chemical reactivity descriptors (GCRD) parameters. These parameters were evaluated by using the following equations: h ¼ 1 ðE IþA ; S ¼ 1 ; c ¼ IþA ; u ¼ m2 . The m E Þ; ¼ LUMO HOMO 2 2 2h 2 2h ionization potential (I) and electron affinity (A) can be obtained as I ¼ EHOMO and A ¼ ELUMO . The calculated values of GCRD parameters are summarized in Table 8. The chemical hardness (h) values for complexes 1, 2 and 3 are 1.884, 1.842 and 1.415 eV, Table 8 Calculated energy values of the title compounds 1e3 by B3LYP/6-31G(d,p) method. Calculated energies DFT/B3LYP/6-31G(d,p)
1
2
3
EHOMO ELUMO Energy gap (DE) Ionization potential (I) Electron affinity (A) Electronegativity (c) Chemical potential (m) Chemical hardness (h) Chemical softness (s) Electrophilicity index (u)
6.187 2.419 3.768 6.187 2.419 4.303 4.303 1.884 0.265 4.913
6.041 2.356 3.685 6.041 2.356 4.198 4.198 1.842 0.271 4.783
6.539 2.837 3.702 6.539 2.837 4.688 4.688 1.415 0.353 7.765
respectively. Obtained small h value indicates that the charge transfer occurs in the complex [32]. As can be seen in Table 8, the global electrophilicity parameter (u) of complex 3 has a greater value of 7.765 eV confirming its electrophilic behaviour. The chemical potential (m) values vary between 4.688 and 4.198 eV indicating that the three compounds are more stable. 2.4. Molecular electrostatic potential (MEP) MEP is related to the electronic density and is a useful descriptor in understanding sites for electrophilic and nucleophilic reactions as well as hydrogen bonding interactions [33,34]. The MEP values can be determined experimentally by X-ray diffraction or by computational methods [35e37]. Furthermore, the MEP is used to predict the chemical reactivity of the molecules [38]. In the MEP representation, the regions of negative potential are expected to be sites of protonation or nucleophilic attack, whereas the regions of positive potential are submitted to electrophilic attack. In the present study, the MEP maps clearly suggest different values of electrostatic potential in the three molecules (Fig. 4). Negative regions are associated with Ni, S, P and O atoms and the most maximum positive regions are localized on hydrogen atoms of methyl groups. On the other hand, it can be suggested that the most preferred regions for electrophilic attack are around hydrogen atoms, while the preferred site for a nucleophilic attack is the metal atom. 3. Experimental 3.1. Computational details The quantum chemical calculations (DFT calculations) giving molecular geometries of minimum energies and molecular orbitals
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Fig. 4. Molecular electrostatic potential maps for (a) Complex 1; (b) Complex 2 and (c) Complex 3.
(HOMOeLUMO) were performed in gaseous phase using the Gaussian 03 package [39]. Molecular orbitals are visualized using ‘‘Gauss view’‘. The method used was Becke's three-parameter hybrid-exchange functional, the nonlocal correlation provided by the Lee, Yang and Parr expression, and the Vosko, Wilk, and Nuair 1980 local correlation functional (III) (B3LYP) [40]. The 6-31G(d,p) basis set was used for C, N, O, P and S atoms. The LANL2DZ basis set and pseudo potentials of Hay and Wadt were used for Ni atom [41]. Vibrational spectra of the three complexes were obtained by using the same level of theory. The vibrational frequencies were computed to confirm that the calculated structures are global
minimum energy geometries. The input coordinates are obtained from the X-ray crystal structure data. The structural parameters were adjusted until an optimal agreement between calculated and experimental structure obtained throughout the entire range of available structures. In addition, Highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO), global chemical reactivity descriptors (GCRD), and molecular electrostatic potentials (MEP) were also computed. DFT study of number of metal complexes and compounds have been carried out with this DFT/B3LYP/6-31G(d,p)/LANL2DZ method and found to be suitable for this study and to produce the experimental results [42].
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4. Conclusions In this report three diphenyldithiophosphate complexes of nickel(II) were theoretically studied and compared with the experimental data. In the theoretically determined and reported single crystal X-ray structures of the complexes the nickel atom is four-coordinated by four sulfur atoms from two acyclic dithiophosphato ligands and bonded in bidentate chelating fashion to form a spirocyclic ring leading to the square planar geometry. The conformational analysis has been performed to determine the stable conformers of complexes by using potential energy surface (PES) scan analysis. The theoretical and experimental spectroscopic parameters are in good agreement with each other. The vibrational frequencies were computed to confirm that the calculated structures are global minimum energy geometries. The HOMOLUMO energy levels and the global chemical reactivity descriptors quantum parameters are also calculated. HOMOeLUMO gaps suggest that the charge transfer interactions occur within these complexes. The MEP evaluation has allowed to find the reactive sites for compounds 1e3 where Ni, S, P and O atoms are associated to the negative regions and the most maximum positive regions were localized on hydrogen atoms of methyl groups. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.molstruc.2019.02.105. References [1] R.C. Mehrotra, G. Srivastava, B.P.S. Chauhan, Coord. Chem. Rev. 55 (1984) 207. [2] A.A.S. Elkhaldy, A.M. Abushanabb, E.A. Alkhairc, Appl. Organomet. Chem. 25 (2011) 491. [3] U.N. Tripathi, G. Srivastava, R.C. Mehrotra, Transition Met Chem 19 (1994) 564. [4] S.C. Bajia, Synth React Inorg Met-Org Nano Met Chem 41 (2011) 746. [5] I. Haiduc, Rev. Inorg. Chem. 3 (1981) 353. [6] H.P.S. Chauhan, Coord. Chem. Rev. 173 (1998) 1. [7] A.A.S. Elkhaldy, A.R. Hussien, A.M. Abu Shanab, M.A. Wassef, J. Sulfur Chem. 33 (2012) 295. [8] A.A. Fedorchuk, Y.I. Slyvka, E.A. Goreshnik, I.V. Kityk, P. Czaja, M.G. Myskiv, J. Mol. Struct. 1171 (2018) 644. [9] H. Zheng, W. Tan, G. Jin, W. Ji, Q. Jin, X. Huang, X. Xin, Inorg. Chim. Acta 305 (2000) 14. [10] M.A. Kertesz, M.A. Cook, T. Leisinger, FEMS Microbiol. Rev. 15 (1994) 195. [11] X. Yang, E. Mierzejewski, New J. Chem. 34 (2010) 805. [12] S. Kumar, R. Khajuria, A.K. Jassal, G. Hundal, M.S. Hundal, S.K. Pandey, Acta Crystallogr. B 70 (2014) 761. [13] A. Syed, S.K. Pandey, Monatsh. Chem. 144 (2013) 1129. [14] M. Sajgotra, R. Khajuria, S. Kumar, A. Syed, S. Andotra, G. Kour, V.K. Gupta, R. Kant, S.K. Pandey, Phosphorus, Sulfur Silicon Relat Elem, vol. 190, 2015, p. 1658. [15] A. Syed, R. Khajuria, S. Kumar, A.K. Jassal, M.S. Hundal, S.K. Pandey, Acta Chim.
Slov. 61 (2014) 866. [16] A. Syed, R. Khajuria, S. Kumar, S.K. Pandey, J. Chem. Pharmaceut. Res. 7 (2015) 356. [17] F. Yuan, Y. Haung, Q. Xie, Appl. Organomet. Chem. 16 (2002) 660. [18] Y. Xu, F. Zhang, J. Hazard Mater. 137 (2006) 1636. [19] B. Kim, R. Mourhatch, P.B. Aswath, Wear 268 (2010) 579. [20] P.E.M. Siegbahn, M.R.A. Blomberg, Chem. Rev. 100 (2000) 421. [21] R.J. Deeth, A. Anastasi, C. Diedrich, K. Randell, Coord. Chem. Rev. 253 (2009) 795. [22] P. Comba, M. Kerscher, Coord. Chem. Rev. 253 (2009) 564. [23] M. Kour, S. Kumar, A. Feddag, S. Andotra, A. Chouaih, V.K. Gupta, R. Kant, S.K. Pandey, J. Mol. Struct. 1157 (2018) 708. [24] S. Andotra, S. Kumar, M. Kour, N. Kalgotra, Chayawan Vikas, S.K. Pandey, J. Mol. Struct. 1155 (2018) 215. [25] S. Kumar, A. Syed, S. Andotra, R. Kaur, Vikas, S.K. Pandey, J. Mol. Struct. 1154 (2018) 165. [26] S. Kumar, R. Khajuria, M. Kaur, R. Kumar, L.K. Rana, G. Hundal, V.K. Gupta, R. Kant, S.K. Pandey, J. Chem. Sci. 128 (2016) 921. € [27] H.H. Kart, S. Ozdemir Kart, M. Karakus, M. Kurt, Spectrochim. Acta, Part A 129 (2014) 421. [28] F. Billesa, A. Holmgren, H. Mikosch, Vib. Spectrosc. 53 (2010) 296. [29] S. Kumar, R. Khajuria, V.K. Gupta, R. Kant, S.K. Pandey, Polyhedron 72 (2014) 140. [30] S. Gunasekaran, R.A. Balaji, S. Kumaresan, G. Anand, S. Srinivasan, Can. J. Anal. Sci. Spectrosc. 53 (2008) 149. [31] B. Kosar, C. Albayrak, Spectrochim. Acta, Part A 78 (2011) 160. € Tamer, D. Avcı, Y. Atalay, J. Organomet. Chem. 797 (2015) 110. [32] S. Altürk, O. [33] S.J. Grabowski, J. Leszczynski, Unrevealing the nature of hydrogen bonds: p eelectron delocalization shapes H-bond features, in: J.S. Grabowski (Ed.), Hydrogen Bonding - New Insights, Kluwer, Academic Publishers, New York, 2006, pp. 491e495. [34] J. Tomasi, B. Mennucci, R. Cammi, Chem. Rev. 105 (2005) 2999. [35] H. Benaissi, M. Drissi, S. Yahiaoui, Y. Megrouss, A. Chouaih, F. Hamzaoui, J of Optoelectronics and Biomedical Materials 10 (2018) 73. [36] N. Boukabcha, A. Feddag, R. Rahmani, A. Chouaih, F. Hamzaoui, J. Optoelectron. Adv. Mater. 20 (2018) 140. [37] N. Boubegra, Y. Megrouss, N. Boukabcha, A. Chouaih, F. Hamzaoui, Rasayan J Chem 9 (2016) 751. [38] M. Drissi, N. Benhalima, Y. Megrouss, R. Rahmani, A. Chouaih, F. Hamzaoui, Molecules 20 (2015) 4042. [39] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, V.G. Zakrzewski, J.A. Montgomery, R.E. Stratmann, J.C. Burant, S.J.M. Dapprich, A.D. Millam Daniels, K.N. Kudin, M.C. Strain, O. Farkas, J. Tomasi, V. Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli, C. Adamo, S. Clifford, J. Ochterski, G.A. Petersson, P.Y. Ayala, Q. Cui, K. Monocular, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J. Kieslowski, J.V. Ortiz, A.G. Baboul, B.B. Stefano, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. John-son, ChenW, WongMW, J.L. Andres, C. Gonzalez, M. Head-Gordon, E.S. Replogle, J.A. Pople, Gaussian 03, Revision B.04, Gaussian, Inc, WallingfordCT, 2004. [40] (a) A.D. Becke, J. Chem. Phys. 98 (1993) 5648; (b) C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785. [41] (a) P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 270; (b) W.R. Wadt, P.J. Hay, J. Chem. Phys. 82 (1985) 284. [42] (a) R. Kumar, S. Obrai, J. Mitra, A. Sharma, Spectrochim. Acta, Part A 115 (2013) 244; (b) R. Kumar, S. Obrai, A. Kaur, M.S. Hundal, H. Meehnian, A.K. Jana, New J. Chem. 38 (2014) 1186; (c) R. Kumar, S. Obrai, A. Kaur, M.S. Hundal, J. Coord. Chem. 68 (2015) 2130.
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DFT studies of disubstituted diphenyldithiophosphates of nickel(II): Structural and some spectral parameters Sandeep Kumar a, Anu Radha a, Mandeep Kour a, Rakesh Kumar b, Abdelkader Chouaih c, Sushil K. Pandey a, * a b c
Department of Chemistry, University of Jammu, Jammu, 180006, India Department of Chemistry, DAV University, Jalandhar, 144012, India Laboratory of Technology and Solid Properties (LTPS), Abdelhamid Ibn Badis University, BP 227, Mostaganem, 27000, Algeria
a r t i c l e i n f o
a b s t r a c t
Article history: Received 9 November 2018 Received in revised form 3 February 2019 Accepted 25 February 2019 Available online 27 February 2019
Three nickel(II) disubstituted diphenyldithiophosphate complexes corresponding to [{(ArO)2PS2}2Ni] [Ar ¼ 2,4-(CH3)2C6H3 (1), 3,5-(CH3)2C6H3 (2) and 4-Cl-3-CH3C6H3 (3)] were theoretically compared to the experimentally reported spectroscopic and X-ray diffraction data. The complexes were computationally studied by using density functional theory (DFT) in its hybrid form B3LYP. The complexes were optimized to calculate the different parameters, vibrational bands and NMR theoretically. The conformational analysis has been performed to determine the stable conformers of complexes. In theses complexes the ligands are coordinated to the nickel metal ion as a bidentate chelating agent via the two thiolate sulfur atoms leading to square planar geometry. The energy gaps of frontier orbital (HOMOeLUMO) have also been calculated along with the global reactivity descriptors quantum parameters. The calculated geometric and spectral results reproduced the experimental data with well agreement. Theoretical calculated molecular orbitals (HOMOeLUMO) and their energies have been calculated that suggest charge transfer occurs within the complexes. The electrophilic and nucleophilic sites are theoretically evaluated by molecular electrostatic potential. © 2019 Elsevier B.V. All rights reserved.
Keywords: Diphenyldithiophosphate DFT HOMO-LUMO
1. Introduction Dialkyldithiophosphoric acids [(RO)2PS2H] (R ¼ Me, Et, Prn, PriO, Bun, But or Ph) and alkylenedithiophosphoric acids [OGOPS2H] (G ¼ 1, 2- and 1, 3- glycols) and their metal and metalloid derivatives are well known [1e6]. The interesting bonding possibilities of these ligands have attracted considerable attention. The chemistry of metal-sulfur bond has been reviewed by several researchers during last four decades [1e7] highlighting various aspects of the bonding modes, in relevance to biochemical, industrial, agricultural and analytical applications. The sulfur containing compounds also shows nonlinear optical (NLO) effects [8,9]. The biological aspect of dithiophosphates has been well established in the rapidly growing field of phosphorus-sulfur chemistry [10,11]. The dithiophosphate ligands and their metal derivatives have been screened for in vitro antifungal and antibacterial activities [12e15]. The results are quite promising, so these complexes are candidates
* Corresponding author. E-mail address: [email protected] (S.K. Pandey). https://doi.org/10.1016/j.molstruc.2019.02.105 0022-2860/© 2019 Elsevier B.V. All rights reserved.
for exploration as specific antifungal and antibacterial drugs. The in vitro cytotoxic investigation of some titanium dithiophosphates complexes against the cultivated human cell has also been reported [16]. The dithiophosphates have received much attention for their extensive applications as biocides [17], analytical reagents [18], antiwear and antioxidant additives in motor oils [19]. In the hybrid form B3LYP density functional theory is the most accurate and efficient computational method for the quantum chemical modeling of coordination compounds [20,21]. The various properties of transition metal compounds can be computed and interpreted with DFT than ab intio and semi-empirical quantumchemical method. These computations are often based on known structural data [22]. The literature survey reveals only few reports as theoretical calculations on the structural and vibrational properties of dithiophosphates [23e28]. To the best of our knowledge, reports on theoretical calculations of ditolyl/diphenyldithiophosphates of nickel(II) have not been described so far. In order to comprehend and understand the experimental studies and to provide more insight into molecular parameters and vibrational spectra of the compounds, a comparison of computed structural and spectroscopic data with the previously reported experimental
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213
(crystallographic and spectroscopic) results has been investigated for the title compounds. The present work describes the crystal structures and DFT analyses of previously reported diphenyldithiophosphates of nickel(II) prepared in our laboratory [29]. In addition, HOMO-LUMO analysis, global chemical reactivity descriptors and molecular electrostatic potential investigation were performed with the same level of theory. The molecular electrostatic potential analysis was used to find the reactive sites of the studied compounds. 2. Results and discussion The quantum chemical DFT method is used to model the complexes 1e3 satisfactory. DFT calculations have been performed to get an insight in the molecular structures and explain bonding nature and spectral properties of complexes: [{2,4(CH3)2C6H3O}2PS2]2Ni (1), [{3,5-(CH3)2C6H3O}2PS2]2Ni (2) and [(4Cl-3-CH3C6H3O)2PS2]2Ni (3) and their comparison with experimental data is carried out [29]. The Ni(II) complexes are optimized, structural parameters are calculated. 2.1. Geometrical structures and conformational analysis According to the DFT calculations and reported [29] single crystal X-ray structures of the complexes 1e3 the nickel atom is four-coordinated by four sulfur atoms from two acyclic dithiophosphato ligands and bonded in bidentate chelating fashion to Table 1 Selected experimental and calculated bond lengths (Å) and angles (o) for complex 1.
a
Bond lengths/Bond angles
Experimental
Calculated
Deviation
Ni1eS1 Ni1eS2 P1eS1 P1eS2 P1eO1 P1eO2 S1eNi1eS1i S2eNi1eS2i S1eNi1eS2i S1eNi1eS2 S1eP1eS2 S1eP1eO1 S1eP1eO2 S2eP1eO1 S2eP1eO2 O1eP1eO2
2.229 (11) 2.229 (11) 1.984 (13) 1.984 (12) 1.583 (18) 1.580 (2) 180.00 (4) 180.00 (4) 91.96 (4) 88.04 (4) 102.65 (5) 115.52 (9) 115.74 (9) 115.21 (8) 115.73 (9) 92.85 (10)
2.228 2.229 1.984 1.984 1.579 1.583 180.00 180.00 91.98 88.02 102.61 115.61 115.52 115.73 115.23 92.85
0.001 0 0 0 0.004 0.003 0 0 0.02 0.02 0.04 0.09 0.22 0.52 0.5 0
Symmetry transformations used to generate equivalent atoms: (i) ex, ey, ez.
Table 2 Selected experimental and calculated bond lengths (Å) and angles (o) for complex 2.
Fig. 1. Optimized structures of (a) [{2,4-(CH3)2C6H3O}2PS2]2Ni (1); (b) [{3,5(CH3)2C6H3O}2PS2]2Ni (2) and (c) [(4-Cl-3-CH3C6H3O)2PS2]2Ni (3).
a
Bond lengths/Bond angles
Experimental
Calculated
Deviation
Ni1eS1 Ni1eS2 P1eS1 P1eS2 P1eO1 P1eO2 S1eNi1eS1ii S2eNi1eS2ii S1ii eNi1eS2 S1eNi1eS2 O1eP1eS1 O2eP1eS1 O1eP1eS2ii O2eP1eS2ii S2ii eP1eS1 O2eP1eO1
2.2305 (6) 2.2370 (6) 1.9778 (8) 1.9770 (8) 1.5880 (18) 1.5813 (17) 180.00 (3) 180.00 (18) 88.79 (2) 91.21 (2) 114.20 (8) 114.19 (7) 115.02 (7) 109.98 (7) 104.43 (4) 99.34 (9)
2.245 2.239 1.991 1.992 1.607 1.599 179.98 179.97 91.04 91.05 115.15 110.06 114.31 114.38 104.08 99.19
0.015 0.002 0.014 0.015 0.019 0.086 0.02 0.03 2.25 0.16 0.95 4.13 0.71 4.4 0.35 0.15
Symmetry transformations used to generate equivalent atoms: (ii) 1ex, ey, ez.
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Table 3 Selected experimental and calculated bond lengths (Å) and angles (o) for complex 3. Bond lengths/Bond angles
Experimental
Calculated
Deviation
Ni2eS1 Ni2eS2 S1eP1 S2eP1 P1eO1 P1eO2 S1eNi2eS1ii S2eNi2eS2ii S1eNi2eS2 S1eNi2eS2ii O1eP1eO2 S2eP1eO2 S2eP1eO1 S1eP1eO2 S1eP1eO1 S1eP1eS2
2.2396 (5) 2.2438 (5) 1.9723 (7) 1.9776 (7) 1.5855 (14) 1.5917 (14) 180.00 (2) 180.00 (2) 89.142 (18) 90.86 (18) 98.78 (8) 113.95 (6) 115.38 (6) 114.37 (6) 108.91 (6) 105.61 (3)
2.239 2.243 1.977 1.978 1.586 1.591 179.97 179.98 89.15 90.86 98.74 114.37 115.40 113.93 108.90 105.63
0.0006 0.0008 0.0047 0.0004 0.0005 0.0007 0.03 0.02 0.008 0 0.04 0.42 0.02 0.44 0.01 0.02
form a spirocyclic ring leading to the square planar geometry. It is appropriate here to correlate the structural parameters obtained from the crystal structure studies with the computational data. Fig. 1 shows the optimized molecular structures for complexes 1e3. Comparisons of selected bond lengths and bond angles are given in Tables 1e3. It is important to mention here that the optimized structures are close to the experimental ones. With regards to bond lengths the maximum deviations is observed in the P1dO2 (0.086 Å) bond length of the complex 2, while for bond angles the maximum deviation is shown by the bond angle O2eP1eS1 (4.13 ) and of complex 2. The small discrepancies in bond lengths and bond angles are attributable to packing interactions within the lattice, which are not modeled during computational studies. The conformational analysis has been performed to determine the stable conformers of complexes 1e3 by using potential energy surface (PES) scan analysis with C1eO1eP1eO2 dihedral angle
aSymmetry transformations used to generate equivalent atoms: (ii) 1ex, ey, ez.
Fig. 2. Conformations with relative energies obtained at DFT/B3LYP level for (a) Complex 1, (b) Complex 2 and (c) Complex 3.
S. Kumar et al. / Journal of Molecular Structure 1185 (2019) 212e218
from 65 to 245 . The dihedral angle C1eO1eP1eO2 for the studied complexes is the relevant coordinate for conformational stability within the molecules. This dihedral angle was chosen by considering that the compounds contain two symmetric fragments in regards to the metal atom. The conformational analysis of complexes 1e3 was performed by using B3LYP level with 6-31G(d,p) and LANL2DZ bases sets. During the PES scan, all the geometrical parameters were simultaneously relaxed, while the dihedral angle C1eO1eP1eO2 was allowed to vary in the steps of 10 . The minimum and maximum energy conformers obtained from conformational analysis are given in Fig. 2.
215
Table 5 1 H spectral data of complexes 1e3 (in ppm). Complex
Assignments
Experimental
Calculated
1.
(s, 2eCH3) (s, 4eCH3) (d, H6) (d, H5) (s, H3) (s, 3,5e(CH3)2) (s, H2,6) (s, H4) (s, 3eCH3) (d, H6) (s, H2) (d, 4H, H3)
2.30 2.36 6.87 7.07 7.37 2.35 7.08 6.80 2.27 7.13 7.18 7.31
2.38, 2.48, 8.13 7.29 7.20 2.34, 6.23, 6.84 1.85, 6.94 6.91 6.26
2.
3.
2.2. Spectral data
1.56, 2.49 2.03, 2.02
2.14, 1.87, 2.36, 2.18, 1.85 6.90 2.38, 2.34, 2.31, 1.56, 2.39
s ¼ singlet, d ¼ doublet.
Vibrational spectroscopy has been widely used as a standard tool for structural characterization of molecular systems by DFT calculations. It is found that the calculated frequencies are close to the experimental values. Experimental and calculated vibration frequencies along with corresponding vibrational assignments are given in Table 4. The vibrational frequencies for optimized molecules were calculated at the same level of the theory. The theoretical IR spectra for the complexes 1e3 are shown in Fig. S1 (see electronic supplementary information). In the experimental spectra of the complexes 1e3, the appearance of new bands in the region 381e370 cm1 can be attributed to [vNiS] bands. These bands were calculated in the region 372353 cm1. Diphenyldithiophosphate moiety bands [vPS]asym and [vPS]sym are observed in the regions 704650 and 635557 cm1, while the corresponding theoretical values are in the regions 706633 and 658562 cm1, respectively. The NMR spectra were predicted for complexes 1e3 using B3LYP/6-31G**/DFT method and the spectral data was compared with experimental data (Fig S2-S5 and Scheme S1) reported in literature [29]. From 1H NMR results reported in Table 5, it can be concluded that the B3LYP functional with GIAO method and 631G(d,p) basis set predicted well the 1H NMR spectra. Some differences between experimental and theoretical 1H NMR results are due to the intermolecular interactions involving the hydrogen atoms and the environment of each H-atom. The computed NMR spectral data is fairly in agreement with experimental data (Tables 5 and 6). Small deviations are due to the fact that any type of lattice interactions are not modeled in theoretically computed structures. 2.3. HOMO-LUMO analysis and chemical reactivity The Frontier Molecular Orbitals (FMOs) play a crucial role on the reactivity of any chemical system. For instance, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) show the ability of donating and accepting an electron in any molecule, respectively [30]. Several chemical properties of a molecule including chemical hardness, chemical potential, reactivity, kinetic stability, optical polarizability, chemical
Table 6 13 C NMR spectral data of the complexes 1e3 (in ppm). Complex
Assignments
Experimental
Calculated
1.
(2eCH3), (4eCH3) C1 C2 C3 C4 C5 C6 (3,5e(CH3)2) C1 C2 C3 C4 C5 C6 (3eCH3) C1 C2 C3 C4 C5 C6
17.3, 20.8 146.8 127.4 135.4 132.1 129.9 120.8 21.3 149.6 118.9 139.5 127.7 139.5 118.9 19.7 151.3 123.9 135.4 127.1 128.7 120.6
19.52, 21.85 142.56 128.28 127.51 131.75 122.85 117.53 22.33, 22.27 150.16 115.46 136.21 124.02 136.07 115.17 22.16, 21.97 147.92 120.00 116.28 146.30 121.22 115.89
2.
3.
softness, electronegativity, electrophilicity etc. can be explained by FMOs. The molecules having a large energy gap are known as hard, and those having a small energy gap are known as soft molecules. Soft molecules are more polarizable than the hard ones because they need only small amounts of energy for excitation [31]. Furthermore, the charge transfer interactions within a molecule can be deduced from the HOMO and LUMO energy gap. On the other hand, the stability of a molecule is related to hardness, which indicates that the molecule with low energy gap means high reactivity. The energy values HOMO and LUMO calculated at the B3LYP/6-31G(d,p) level are given in Table 7. In complexes 1e3, LUMO and HOMO (Fig. 3) are mainly distributed over the Ni, O and S atoms. The energy gap between the HOMO and the LUMO is a critical parameter in determining molecular electrical transport
Table 4 Selected experimental and calculated IR vibrational frequencies (cm1) for complexes 1e3. Assignment
[v(P)eOeC] [vPO(C)] [vPS]asym [vPS]sym [vNiS]
Complex 1
Complex 2
Complex 3
Experimental
Theoretical
Experimental
Theoretical
Experimental
Theoretical
1105 s 869 s 650 s 572 m 370 w
1116 867 633 562 372
1101 s 858 s 654 s 557 m 371 w
1116 867 633 562 372
1157 s 971 s 704 s 635 m 381 w
1154 990 706 658 353
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S. Kumar et al. / Journal of Molecular Structure 1185 (2019) 212e218
Table 7 Electronic properties of different conformers for complexes 1e3. Parameters
Complex 1
Dihedral angle ( ) EHOMO (eV) ELUMO (ev) Gap (eV)
Complex 2
Complex 3
C1
C2
C3
C1
C2
C3
C1
C2
C3
130.78 6.07 2.57 3.50
190.78 6.10 2.57 3.53
250.78 6.10 2.58 3.52
116.60 6.00 2.51 3.49
166.60 6.02 2.52 3.50
243.39 6.00 2.52 3.48
116.94 6.41 2.91 3.50
176.93 6.41 2.90 3.51
236.93 6.42 2.92 3.50
C1, C2 and C3 are conformer 1, conformer 2 and conformer 3, respectively.
Fig. 3. Frontier molecular orbital surfaces and energy gap for (a) [{2,4-(CH3)2C6H3O}2PS2]2Ni (1); (b) [{3,5-(CH3)2C6H3O}2PS2]2Ni (2) and (c) [(4-Cl-3-CH3C6H3O)2PS2]2Ni (3).
properties. The values of the energy gap for compounds 1, 2 and 3 were found to be 3.768, 3.685 and 3.702 eV, respectively. The results indicate that the studied compounds have good kinetic stability. In order to highlight the effect of complex conformers to the electronic properties, HOMO, LUMO and the gap energies are computed using the same level of theory as described above. The obtained results are summarized in Table 7. No change was observed for all the complexes which confirm that the calculated geometries are more stable. Recognizing the relationship between strength of structure and chemical reactivity can be achieved by the determination of global chemical reactivity descriptors (GCRD) parameters. These parameters were evaluated by using the following equations: h ¼ 1 ðE IþA ; S ¼ 1 ; c ¼ IþA ; u ¼ m2 . The m E Þ; ¼ LUMO HOMO 2 2 2h 2 2h ionization potential (I) and electron affinity (A) can be obtained as I ¼ EHOMO and A ¼ ELUMO . The calculated values of GCRD parameters are summarized in Table 8. The chemical hardness (h) values for complexes 1, 2 and 3 are 1.884, 1.842 and 1.415 eV, Table 8 Calculated energy values of the title compounds 1e3 by B3LYP/6-31G(d,p) method. Calculated energies DFT/B3LYP/6-31G(d,p)
1
2
3
EHOMO ELUMO Energy gap (DE) Ionization potential (I) Electron affinity (A) Electronegativity (c) Chemical potential (m) Chemical hardness (h) Chemical softness (s) Electrophilicity index (u)
6.187 2.419 3.768 6.187 2.419 4.303 4.303 1.884 0.265 4.913
6.041 2.356 3.685 6.041 2.356 4.198 4.198 1.842 0.271 4.783
6.539 2.837 3.702 6.539 2.837 4.688 4.688 1.415 0.353 7.765
respectively. Obtained small h value indicates that the charge transfer occurs in the complex [32]. As can be seen in Table 8, the global electrophilicity parameter (u) of complex 3 has a greater value of 7.765 eV confirming its electrophilic behaviour. The chemical potential (m) values vary between 4.688 and 4.198 eV indicating that the three compounds are more stable. 2.4. Molecular electrostatic potential (MEP) MEP is related to the electronic density and is a useful descriptor in understanding sites for electrophilic and nucleophilic reactions as well as hydrogen bonding interactions [33,34]. The MEP values can be determined experimentally by X-ray diffraction or by computational methods [35e37]. Furthermore, the MEP is used to predict the chemical reactivity of the molecules [38]. In the MEP representation, the regions of negative potential are expected to be sites of protonation or nucleophilic attack, whereas the regions of positive potential are submitted to electrophilic attack. In the present study, the MEP maps clearly suggest different values of electrostatic potential in the three molecules (Fig. 4). Negative regions are associated with Ni, S, P and O atoms and the most maximum positive regions are localized on hydrogen atoms of methyl groups. On the other hand, it can be suggested that the most preferred regions for electrophilic attack are around hydrogen atoms, while the preferred site for a nucleophilic attack is the metal atom. 3. Experimental 3.1. Computational details The quantum chemical calculations (DFT calculations) giving molecular geometries of minimum energies and molecular orbitals
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Fig. 4. Molecular electrostatic potential maps for (a) Complex 1; (b) Complex 2 and (c) Complex 3.
(HOMOeLUMO) were performed in gaseous phase using the Gaussian 03 package [39]. Molecular orbitals are visualized using ‘‘Gauss view’‘. The method used was Becke's three-parameter hybrid-exchange functional, the nonlocal correlation provided by the Lee, Yang and Parr expression, and the Vosko, Wilk, and Nuair 1980 local correlation functional (III) (B3LYP) [40]. The 6-31G(d,p) basis set was used for C, N, O, P and S atoms. The LANL2DZ basis set and pseudo potentials of Hay and Wadt were used for Ni atom [41]. Vibrational spectra of the three complexes were obtained by using the same level of theory. The vibrational frequencies were computed to confirm that the calculated structures are global
minimum energy geometries. The input coordinates are obtained from the X-ray crystal structure data. The structural parameters were adjusted until an optimal agreement between calculated and experimental structure obtained throughout the entire range of available structures. In addition, Highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO), global chemical reactivity descriptors (GCRD), and molecular electrostatic potentials (MEP) were also computed. DFT study of number of metal complexes and compounds have been carried out with this DFT/B3LYP/6-31G(d,p)/LANL2DZ method and found to be suitable for this study and to produce the experimental results [42].
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4. Conclusions In this report three diphenyldithiophosphate complexes of nickel(II) were theoretically studied and compared with the experimental data. In the theoretically determined and reported single crystal X-ray structures of the complexes the nickel atom is four-coordinated by four sulfur atoms from two acyclic dithiophosphato ligands and bonded in bidentate chelating fashion to form a spirocyclic ring leading to the square planar geometry. The conformational analysis has been performed to determine the stable conformers of complexes by using potential energy surface (PES) scan analysis. The theoretical and experimental spectroscopic parameters are in good agreement with each other. The vibrational frequencies were computed to confirm that the calculated structures are global minimum energy geometries. The HOMOLUMO energy levels and the global chemical reactivity descriptors quantum parameters are also calculated. HOMOeLUMO gaps suggest that the charge transfer interactions occur within these complexes. The MEP evaluation has allowed to find the reactive sites for compounds 1e3 where Ni, S, P and O atoms are associated to the negative regions and the most maximum positive regions were localized on hydrogen atoms of methyl groups. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.molstruc.2019.02.105. References [1] R.C. Mehrotra, G. Srivastava, B.P.S. Chauhan, Coord. Chem. Rev. 55 (1984) 207. [2] A.A.S. Elkhaldy, A.M. Abushanabb, E.A. Alkhairc, Appl. Organomet. Chem. 25 (2011) 491. [3] U.N. Tripathi, G. Srivastava, R.C. Mehrotra, Transition Met Chem 19 (1994) 564. [4] S.C. Bajia, Synth React Inorg Met-Org Nano Met Chem 41 (2011) 746. [5] I. Haiduc, Rev. Inorg. Chem. 3 (1981) 353. [6] H.P.S. Chauhan, Coord. Chem. Rev. 173 (1998) 1. [7] A.A.S. Elkhaldy, A.R. Hussien, A.M. Abu Shanab, M.A. Wassef, J. Sulfur Chem. 33 (2012) 295. [8] A.A. Fedorchuk, Y.I. Slyvka, E.A. Goreshnik, I.V. Kityk, P. Czaja, M.G. Myskiv, J. Mol. Struct. 1171 (2018) 644. [9] H. Zheng, W. Tan, G. Jin, W. Ji, Q. Jin, X. Huang, X. Xin, Inorg. Chim. Acta 305 (2000) 14. [10] M.A. Kertesz, M.A. Cook, T. Leisinger, FEMS Microbiol. Rev. 15 (1994) 195. [11] X. Yang, E. Mierzejewski, New J. Chem. 34 (2010) 805. [12] S. Kumar, R. Khajuria, A.K. Jassal, G. Hundal, M.S. Hundal, S.K. Pandey, Acta Crystallogr. B 70 (2014) 761. [13] A. Syed, S.K. Pandey, Monatsh. Chem. 144 (2013) 1129. [14] M. Sajgotra, R. Khajuria, S. Kumar, A. Syed, S. Andotra, G. Kour, V.K. Gupta, R. Kant, S.K. Pandey, Phosphorus, Sulfur Silicon Relat Elem, vol. 190, 2015, p. 1658. [15] A. Syed, R. Khajuria, S. Kumar, A.K. Jassal, M.S. Hundal, S.K. Pandey, Acta Chim.
Slov. 61 (2014) 866. [16] A. Syed, R. Khajuria, S. Kumar, S.K. Pandey, J. Chem. Pharmaceut. Res. 7 (2015) 356. [17] F. Yuan, Y. Haung, Q. Xie, Appl. Organomet. Chem. 16 (2002) 660. [18] Y. Xu, F. Zhang, J. Hazard Mater. 137 (2006) 1636. [19] B. Kim, R. Mourhatch, P.B. Aswath, Wear 268 (2010) 579. [20] P.E.M. Siegbahn, M.R.A. Blomberg, Chem. Rev. 100 (2000) 421. [21] R.J. Deeth, A. Anastasi, C. Diedrich, K. Randell, Coord. Chem. Rev. 253 (2009) 795. [22] P. Comba, M. Kerscher, Coord. Chem. Rev. 253 (2009) 564. [23] M. Kour, S. Kumar, A. Feddag, S. Andotra, A. Chouaih, V.K. Gupta, R. Kant, S.K. Pandey, J. Mol. Struct. 1157 (2018) 708. [24] S. Andotra, S. Kumar, M. Kour, N. Kalgotra, Chayawan Vikas, S.K. Pandey, J. Mol. Struct. 1155 (2018) 215. [25] S. Kumar, A. Syed, S. Andotra, R. Kaur, Vikas, S.K. Pandey, J. Mol. Struct. 1154 (2018) 165. [26] S. Kumar, R. Khajuria, M. Kaur, R. Kumar, L.K. Rana, G. Hundal, V.K. Gupta, R. Kant, S.K. Pandey, J. Chem. Sci. 128 (2016) 921. € [27] H.H. Kart, S. Ozdemir Kart, M. Karakus, M. Kurt, Spectrochim. Acta, Part A 129 (2014) 421. [28] F. Billesa, A. Holmgren, H. Mikosch, Vib. Spectrosc. 53 (2010) 296. [29] S. Kumar, R. Khajuria, V.K. Gupta, R. Kant, S.K. Pandey, Polyhedron 72 (2014) 140. [30] S. Gunasekaran, R.A. Balaji, S. Kumaresan, G. Anand, S. Srinivasan, Can. J. Anal. Sci. Spectrosc. 53 (2008) 149. [31] B. Kosar, C. Albayrak, Spectrochim. Acta, Part A 78 (2011) 160. € Tamer, D. Avcı, Y. Atalay, J. Organomet. Chem. 797 (2015) 110. [32] S. Altürk, O. [33] S.J. Grabowski, J. Leszczynski, Unrevealing the nature of hydrogen bonds: p eelectron delocalization shapes H-bond features, in: J.S. Grabowski (Ed.), Hydrogen Bonding - New Insights, Kluwer, Academic Publishers, New York, 2006, pp. 491e495. [34] J. Tomasi, B. Mennucci, R. Cammi, Chem. Rev. 105 (2005) 2999. [35] H. Benaissi, M. Drissi, S. Yahiaoui, Y. Megrouss, A. Chouaih, F. Hamzaoui, J of Optoelectronics and Biomedical Materials 10 (2018) 73. [36] N. Boukabcha, A. Feddag, R. Rahmani, A. Chouaih, F. Hamzaoui, J. Optoelectron. Adv. Mater. 20 (2018) 140. [37] N. Boubegra, Y. Megrouss, N. Boukabcha, A. Chouaih, F. Hamzaoui, Rasayan J Chem 9 (2016) 751. [38] M. Drissi, N. Benhalima, Y. Megrouss, R. Rahmani, A. Chouaih, F. Hamzaoui, Molecules 20 (2015) 4042. [39] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, V.G. Zakrzewski, J.A. Montgomery, R.E. Stratmann, J.C. Burant, S.J.M. Dapprich, A.D. Millam Daniels, K.N. Kudin, M.C. Strain, O. Farkas, J. Tomasi, V. Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli, C. Adamo, S. Clifford, J. Ochterski, G.A. Petersson, P.Y. Ayala, Q. Cui, K. Monocular, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J. Kieslowski, J.V. Ortiz, A.G. Baboul, B.B. Stefano, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. John-son, ChenW, WongMW, J.L. Andres, C. Gonzalez, M. Head-Gordon, E.S. Replogle, J.A. Pople, Gaussian 03, Revision B.04, Gaussian, Inc, WallingfordCT, 2004. [40] (a) A.D. Becke, J. Chem. Phys. 98 (1993) 5648; (b) C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785. [41] (a) P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 270; (b) W.R. Wadt, P.J. Hay, J. Chem. Phys. 82 (1985) 284. [42] (a) R. Kumar, S. Obrai, J. Mitra, A. Sharma, Spectrochim. Acta, Part A 115 (2013) 244; (b) R. Kumar, S. Obrai, A. Kaur, M.S. Hundal, H. Meehnian, A.K. Jana, New J. Chem. 38 (2014) 1186; (c) R. Kumar, S. Obrai, A. Kaur, M.S. Hundal, J. Coord. Chem. 68 (2015) 2130.