Abstract

Time Dependent Density Functional Theory (TD-DFT/B3LYP/6-31G*) calculations have been performed on the optimized structure of 2, 3-diphenylcyclopropenone (DPCP) in the UV region of the spectra; giving energies, oscillator strength, dipole moment, µ and polarizability, α in solvents of different polarities. The study was also extended to the number of transitions, frontier orbital energy gaps (ELUMO - EHOMO) analysis of this strained ring donor–acceptor (D-A) molecular system to calculate its ionization potential (I), electron affinity (EA) and global hardness (η) in the solvent of choice. This aids in understanding the relationship between the structure and properties of this molecule.TD-DFT/B3LYP/6-31G* calculation results, when compared with the reported experimental studies results of the solvatochromic shift properties of this molecule, showed ten excited singlet states for DPCP in the UV region. This indicates minimum overlap of the electronic transition bands computationally. The increased ΔELUMO-HOMO (4.09 - 4.31eV), I and ƞ, the lower dipole moments and polarizability values as solvent polarity increased, suggests high stability of this compound in polar solvents. The excess polarizabilities obtained for its singlet excited states show that the excited state of this compound is more polar than its ground state, and that, the molecule is chemically active.

Highlights

  • 2, 3-diphenylcyclopropenone (DPCP), a highly basic amphiphilic, three-membered strained ring donor– acceptor (D-A) molecular system, have attracted significant attention due to its participation in a wide variety of synthetically useful reactions and its application in medicine (Ashraf, Alaa, Mohsen and ElSheref, 2007; Damian and Thompson, 2007)

  • Changes in dipole moment and polarizability usually alter the electrostatic interaction of molecules with the solvent in the ground and excited state, which causes a shift in the absorption maximum (Grozema, Telesca, Jonkman, Siebbeles and Snijders)

  • The Ultra violet (UV) stability, electron distribution and reactivity of this system, based on the Qualitative Structure Property Relationship (QSPR) parameters (Gerlings, De-Proft and Langeneaker, 2003; Shubing, 2005): energy gap, ionization potential (IP), electron affinity (EA), global hardness (ƞ), global electrophilicity (ɷ) and chemical potential (ϗ) which a measure of the escaping tendency of electrons from equilibrium are discussed; the results obtained are compared with earlier reports based on the modified

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Summary

Introduction

2, 3-diphenylcyclopropenone (DPCP), a highly basic amphiphilic, three-membered strained ring donor– acceptor (D-A) molecular system, have attracted significant attention due to its participation in a wide variety of synthetically useful reactions and its application in medicine (Ashraf , Alaa, Mohsen and ElSheref, 2007; Damian and Thompson, 2007) This molecule reacts readily with both nucleophilic and electrophilic reagents, forming a ring opening products with the possibility of carbonyl or conjugate addition. Accurate determination of its structural properties, such as; dihedral angles, bond angles bond length, molecular vertical excitation energies, dipole moment and polarizability in different solvent are essential (Ashraf , Alaa, Mohsen and El-Sheref, 2007). The UV stability, electron distribution and reactivity of this system, based on the Qualitative Structure Property Relationship (QSPR) parameters (Gerlings, De-Proft and Langeneaker, 2003; Shubing, 2005): energy gap, ionization potential (IP), electron affinity (EA), global hardness (ƞ), global electrophilicity (ɷ) and chemical potential (ϗ) which a measure of the escaping tendency of electrons from equilibrium are discussed; the results obtained are compared with earlier reports based on the modified

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