Theoretical Functional Calculations (DFT) Studies of Structural Properties of 1-Benzoyl-3-[(2-benzyl Sulfanyl) phenyl]thiourea with Comparison of Experimental Data

 

Shima Siahgali*, Shahriar Ghammamy

                Department of Chemistry, Faculty of Science, Imam Khomeini International University, Qazvin, Iran.

*Corresponding Author E-mail: shghamamiii@yahoo.com

In this paper, we report an inter-comparison of various physical and electronic properties of C₂₁H₁₈N₂OS₂ The molecular geometry, vibrational frequencies, energies and natural bond orbital (NBO) in the ground state are calculated by using the DFT (B3LYP) methods with LANL2DZ.  The geometries and normal modes of vibrations obtained from B3LYP calculations are in good agreement with the experimentally observed data.

 

1.      INTRODUCTION:

In the title compound figuar1, C₂₁H₁₈N₂OS₂, a strong intermolecular N-H…Ohydrogen bond [N…O=2.642(3) Å] between the amid N atom and the benzoyl atom from an almost planer six-membered ring in the centeral part of the molecule.

 

Thiourea is an organosulfur compound with theformula SC(NH₂)₂ . It is structurally similar to urea, except that the oxygen atom is replaced by asulfur atom, but the properties of urea and thiourea differ significantly Thiourea is a reagent in organic synthesis. "Thioureas" refers to a broad class of compounds with the general structure (R1R2N)(R3R4N)C=S. Thioureas are related to thioamides, e.g. RC(S)NR2, where R is methyl,ethyl, etc.

 

Thiourea is a planar molecule. The C=S bond distance is 1.60 ±0.1 Å for thiourea (as well as many of its derivatives). The material has the unusual property of changing to ammonium thiocyanate upon heating above 130 °C. Upon cooling, the ammonium salt converts back to thiourea. Thioureas are used a building blocks to pyrimidine derivatives, Thiourea is a reagentin organic synthesis.

 

Substituted thioureas are useful catalysts for organic synthesis. Other industrial uses of thiourea include production of flame retardant resins, and vulcanizationaccelerators. It is also used to tone silver-gelatin photographic prints.[1-5]

 

We applied the DFT method to optimize and calculate molecular data of compound. The calculation was done by using the Gaussian 09 programs AD (1993), Becke For DFT, Becke’s three-parameter exchange functional CT (1988), Lee was used in combination with the Lee–Yang–Parr correlation functional (B3LYP) with LANL2DZbasis set.  Density functional theory methods were employed and determine the optimized structures of C₂₁H₁₈N₂OS₂ can be seen figuar 2. [6-7]

 

Figure-1 The molecular structure of the title compoundC₂₁H₁₈N₂OS_2.

 

2.   EXPERIMENTAL:

2.1   Computational method:       

All computational are carried out using Gaussian 09 program [7-8] which combines the exact Hartree-Fock exchange with Becke^,s and uses the Lee-Yang-Parr correlation function in order to include the most important correlation effects. The structures of the molecules were completely optimized without any symmetry in all the levels. The optimized structural parameters were used in the vibrational frequency calculations at the DFT levels to characterize all stationary points as minima. Infrared intensities (int) in Kilometer per mole of all compounds were performed at the same level on the respective fully optimized geometries.

 

Figure-2-Optimized geometries of C₂₁H₁₈N₂OS₂ at B3LYP/LanL2DZ level of theory.

 

2.2   Frontier molecular orbital

  Both the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are the main orbital take part in chemical stability. The HOMO represents the ability to donate an electron, LUMO as an electron acceptor represents the ability to obtain an electron. The HOMO and LUMO energy were calculated by B3LYP/LANL2DZ method. This electronic absorption corresponds to the transition from the ground to the first excited state and is mainly described by one electron excitation from the highest occupied molecular or orbital (LUMO). Therefore, while the energy of the HOMO is directly related to the ionization potential, LUMO energy is directly related to the electron affinity. Energy difference between HOMO and LUMO orbital is called as energy gap that is an important stability for structures. 3D plots of highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) are shown in (Figure 4).

 

 

Figure-3-Crystal packing diagram for the title compound. Hydrogen bonds are shown as dashed line

 

Figure-4 The atomic orbital of the frontier molecular orbital for C₂₁H₁₈N₂OS₂ at B3LYP/LanL2DZ level of theory.

 

 

2.3 NBO study on structures

Natural bond orbital (NBO) methods’ refers to a suite of mathematical algorithms for analyzing electronic wave functions in the language of localized Lewis-like chemical bonds. In these methods, molecular properties are expressed in terms of a ‘natural Lewis structure’ (NLS) depiction of the wave function, in direct correspondence to the elementary Lewis dot diagram of freshman chemistry. NBOs can be described as a ‘chemist’s basis set’ that allows any aspect of the wave function to be expressed in terms of L- versus NL-type contributions, thereby providing a bridge between modern wave function technology and elementary valency and bonding concepts   [9-10] . NBO analysis is carried out by examining all possible interactions between 'filled' (donor) Lewis-type NBOs and 'empty' (acceptor) non-Lewis NBOs, and estimating their energetic importance by 2nd-order perturbation theory. Since these interactions lead to loss of occupancy from the localized NBOs of the idealized Lewis structure into the empty non-Lewis orbitals (and thus, to departures from the idealized Lewis structure description), they are referred to as 'delocalization' corrections to the zeroth-order natural Lewis structure. For each donor NBO (i) and acceptor NBO (j), the stabilization energy E⁽²⁾ associated with delocalization ("2e-stabilization") is estimated.

 

Table 1:Comparative experimental and DFT study of geometrical parameters of 1-Benzoyl-3-[(2-benzyl Sulfanyl)phenyl]thiourea some selected bond lengths (Å) Crystal data of1-Benzoyl-3-[(2-benzyl Sulfanyl)phenyl]thiourea

 

 

 

 

 

Table 2: Comparative experimental and DFT study of geometrical parameters of 1-Benzoyl-3-[(2-benzyl Sulfanyl)phenyl]thiourea some selected bond angles (◦)Crystal data of1-Benzoyl-3-[(2-benzyl Sulfanyl)phenyl]thiourea

Table3:

Crystal data of 1-Benzoyl-3-[(2-benzyl Sulfanyl)phenyl]thiourea

 

Table 4:  The NBO Calculated Hybridizations for C₂₁H₁₈N₂OS₂ at the B3LYP/LanL2DZ.

 

TABLE-5-Second order perturbation theory analysis of Fock matrix in NBO basis for C₂₁H₁₈N₂OS₂ E(2)^a means energy of hyper conjugative interaction (stabilization energy); ^b Energy difference between donor and acceptor i and j NBO orbital's; ^c F(i, j) is the Fock matrix element between i and j NBO orbital's

 

 

TABLE-6- Comparative experimental and DFT study of geometrical parameters of 1-Benzoyl-3-[(2-benzyl Sulfunyl)phenyl]thiourea some selected Torsion Crystal data of1-Benzoyl-3-[(2-benzyl Sulfanyl)phenyl]thiourea

 

 

 

3.      RESULTS AND DISCUSSION:              

Comparative experimental and DFT study of the interatomic distances and the bond angles and structures of C₂₁H₁₈N₂OS₂.  (Table 1, 2)  Comparing  the DFT data and experimental data show that data are similar .

 

The crystal data are given in (Table 3). The molecular structural backbones and the crystal packing of these compound are shown in ( Figure.3). 

 

The NBO method is preferred to Mulliken charges, because the former provides an orbital picture that is closer to the classical Lewis structure. The NBO analysis involving atomic charges, bond orders as well as hybridizations of selected bonds are calculated at B3LYP/LANL2DZ level. The NBO calculated hybridization for C₂₁H₁₈N₂OS₂ shows that all of compounds have SP^X hybridization and non planar configurations (Table4). Second order perturbation theory analysis of Fock matrix in NBO basis for C₂₁H₁₈N₂OS₂ is shown in( Table 5). Comparative experimental and DFT study of the interatomic Torsion structures of C₂₁H₁₈N₂OS₂ (Table 6).

 

4.      CONCLUSION:

Experimental data have been taken from the article 1-benzoyl-3-[(2-benzyl sulfanyl)phenyl]thiourea. [11]

 

The molecular geometry, vibrational frequencies, energies and natural bond orbital (NBO) in the ground state are calculated by using the DFT (B3LYP) methods with LANL₂DZ.

                                                                                                                                                   

We gratefully acknowledge the financial support from the Research Council of Imam Khoemieni International University by Grant No, 751387-91 and many technical supports that provided by Tarbiat Modaress University .

 

5. REFERENCES:  

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2.        Miyabe, H.; Takemoto, Y. "Discovery and application of asymmetric reaction by   multifunctional thioureas" Bull Chem Soc Jpn (2008), vol. 81, p785ff

3.        Gupta, D., Soman, G., and Dev, S.. "Thiourea, a convenient reagent for the reductive  cleavage of olefin ozonolysis products". Tetrahedron 38 (20): 3013(1982). doi:10.1016/0040-4020 (82) 80187-7.

4.        Anthony Esposito. "Peñoles, UAM unveil pilot thiourea Au-Ag leaching plant - Mexico". Business News Americas (July 13, 2007).

5.        Peter R. Schreiner, "Metal-free organocatalysis through explicit hydrogen bonding interactions" Chem. Soc. Rev., (2003), vol. 32, 289-296.

6.        Becke, Density-functional thermochemistry. III. The role of exact   Exchange J. Chem Phys(1993), A.D., 98: 5648-565 

7.        Sundaraganesan, N.,S. Ilakiamani, B. Dominic Joshua, Vibrational Spectroscopy   investigation using ab initio and density functional theory analysis on  the   structure of 3, 4-dimethylbenzaldehyde.SpectrochimicaActa(2007) partA,68:680

8.        Roland, A., Seppelt.K. Sundermeyer, W. ¹⁹F-Kernresonanzen an Imidoschwefeloxiddfluoriden, Z. anorg.allg . Chem(1972)., 393, 149-151.                    

9.        Seppelt, K. Arsenpentachlorid, Angew. Chem(1976). 88, 410-41 WIREs Comput Mol Sci, Natural bond orbital methods(2012), 2: 1–42 doi:   10.1002/wcms.51

10.     Bahttacharjee ,P. Gogi, V.G. Puranik, R.L. Gawadeand .Barman(2012). Acta  Cryst.C68,0485-0487

 

 

 

Received on 09.11.2013         Modified on 10.12.2013

Accepted on 15.12.2013         © AJRC All right reserved