Quantum Chemical DFT study of the fulvene halides molecules (Fluoro, Chloro, Bromo, Iodo, and stato fulvenes)

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1 - - Quantum Chemical DFT study of the fulvene halides molecules (Fluoro, Chloro, Bromo, Iodo, and stato fulvenes) Jaafar.. Ali* Shaymaa Ibrahim Saeed Zuafurni Khulood Obaid Kzar Dept. of Chemistry, College of Science, Karbala University, Karbala-IRAQ. *Abosadg_@yahoo.com Key words:-dft method, Fluoro, Chloro, Bromo, Iodo, and statofulvenes Abstract:- DFT calculations, within Gaussian0 Program, have been done after complete optimization of geometry on X-monosubstituted halofulvenes, where X is F, Cl, Br, I, and At.It was found that all the substituents are stabilizing and all of them increasing the dipole moment and decreasing the LUMO and OMO energies. Geometrical parameters, total energy, electron charge densities, ionization energies, and the U o, o, S o, A o, and G o thermodynamics functions are reported.

2 - - F 0 F 0 F 0 0 Cl 0 Cl 0 Cl 0 0 Br 0 Br 0 Br 0 I 0 I 0 I 0 At 0 At 0 At 0 Fig.-The studied halofulvenes with their atomic numbering.

3 - - Introduction: Fulvenes are cross-conjugated molecules with some unique properties[-]. Their structure and electron distribution have been investigated theoretically [] and experimentally []. The parent fulvene and the effect of substituents on the fulvene and their radical anions and cations were theoretically reported[].. The halogenated substituted fulvenes were used to improve the octane quality of a fule for an internal combustion engines[].the fluorosubstituted fulvenes is relatively common ligand in organometalic; the low-valent titanium-pentafulvene complexes have been prepared[]. Computational Details The optimized geometry along with some of the physical properties of the title molecules were calculated using the Gaussian0 software package on a personal computer[ ]. The density functional theoretical (DFT) computations were performed at the BLYP/CEP-G level of theory to get the optimized geometry of the title molecules, Table. The DFT partitions the electronic energy E=ET+ EV + EJ +EXC, where ET, EV and EJ are electronic kinetic energy, electron nuclear attraction and electron electron repulsion terms, respectively. The electron correlation is taken into account in the DFT via the exchange-correlation term EXC, which includes exchange energy arising from the antisymmetry of quantum mechanical wavefunction and dynamic correlation in the motion of individual electrons, and it makes DFT dominant over the conventional artree Fock (F) procedure [0]. DFT calculations were carried out with Becke s threeparameter hybrid model using the Lee Yang Parr correlation functional (BLYP) method. Molecular geometries were fully optimized by Berny s optimization algorithm using redundant internal coordinates. All optimized structures were confirmed to be minimum energy conformations The optimum geometry was determined by minimizing the energy with respect to all geometrical parameters without imposing molecular symmetry constraints. Results and Dicussion -Dipole Moments The dipole moment character of fulvene can understood as resulting from intra molecular charge transfer from the exocyclic double bond to the five-membered ring acequiring pseudoaromatic cylopentadienide character[]. All the substituents are found to increase the dipole moment (Table ). This effect is more pronounced in case of F and Cl. -Structural details Introduction of a substituent into the fulvene molecule decreases the adjacent bond length (Table ). This effect is more pronounced for F and Cl which is in agreement with high dipole moment calculated (Table ).All the substituents are found to produce a small increase in the bond angle to which the substituent is attached. -Electron Densities It can seen from Table that the substituents, Cl, Br, I, and At increase the charge densities on the carbon atom to which the substituent is attached and decrease the charge density on the adjacent carbon atom, i.e. they act as electron releasing. The F shows an opposite effect to that found for the former, i.e.. act as electron with drawing.

4 - - -Stabilization by Substituents The stabilizing effect of a substituent is often assessed by using isodesmic reactions(conserved bond type) []. A positive energies indicates stabilization of the reactant by the sustituent, Table. The results show that all the substituents are stabilizing. It was found that the F stabilizes the fulvene molecule more than the other substituents due to its high dipole moment( Table ) -Orbital Energies According to Koopman s' theorem (the negative OMO is equal to the ionization potential). All the F, Cl, Br, I, and At substituents are found to decrease the energies of OMO and LUMO ( Table ) to a certain extend. The low energy of LUMO suggests a high reactivity. This is in agreement with the -Cl fulvene which has a high reactivity towards nucleophilic attack[]. -Thermodynamics Data It can be seen from Table that each one of the substituted fulvenes (-) has higher entropy, S o, than fulvene. The higher values are for At substituted fulvenes(- ).The reason is of course due to large number of electrons of At atom. Table :The geometric parameters of studied halofulvene molecules. R is bond length, in A o, and A is bond angle, degrees Bondlength(bond angle)* R(-) R(-) R(-) R(-) R(-) R(-) R(-) R(-) R(-0) R(-) R(-) R(-) A(--) A(--) A(--) A(--) A(--) A(--)

5 - - A(--) A(--) A(--) A(--) A(--) A(--) A(--0) A(--0) A(--) A(--).... A(--).... A(--)..0.. A(--) A(--) A(--) Table.-Cont

6 * The numbers,,, and 0 for molecule are replaced by,,0,and respectively for the all the remaining molecules except that number 0 is replaced by for the molecules,,,, and the number is replaced by for the molecules,,,, and. See Fig. Table.: Some physical properties of the halofulvene molecules involved in this study* Molec. no. E(RB+F- LYP], A.U Dipole moment, E OMO, A.U E LUMO, A.U Ionization Energy, A.U E OMO -LUMO, Debye A.U

7 *All the molecules belong to C s symmetry point group.see Fig. Table :The atomic electron densities of the studied halofulvene molecules.see Fig-for numbering. Atom Molecule no. no Table :Contd. Atom Molecule no. no

8 - - Table :Contd Atom Molecule no. no Table.Evaluation of substituent effects (energies are in A.U), * F Cl Br I At CC X X +CC X + CC * = products - reactants

9 - - Table. Thermodynamic Data for the fulvene and halofulvene molecules.see Fig. Molecule no. U o, o, S o, A o, G o, Kcal mol - Kcal mol - cal K - mol - Kcal mol - Kcal mol

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