Structure Elucidation of Schiff Base-Containing Compound by Quantum Chemical Methods

Abstract

Schiff bases, named after German chemist Hugo Schiff, are compounds with a central functional group containing an imine or azomethine (-C=N-) linkage. They have been extensively studied in various fields such as organic synthesis, coordination chemistry, and medicinal chemistry due to their diverse properties and wide range of applications. Schiff bases have been extensively utilized in scientific research since their discovery due to their multifaceted properties. The intense focus on Schiff bases in the literature stems from their versatile characteristics. This study aims to elucidate the theoretical physical and chemical properties of a compound containing a Schiff base, (Z)-4-(2,6-dichlorophenyldiazenyl)-6-{[1,3-dihydroxy-2-(hydroxymethyl)propan-2-ylamino]methyl}-2-methoxycyclohexa-2,4-dienone, whose structure was previously experimentally elucidated by X-ray diffraction. GaussView 4.1.2 and Gaussian 03W were employed to determine the compound’s physical and chemical properties. Based on experimental and theoretical geometric parameters, the compound was observed to possess a keto-amine tautomeric form and exhibit high aromaticity, as evidenced by computational HOMA indices. The compound’s electrophilic and nucleophilic regions were illuminated based on identified frontier molecular orbitals and electronic parameters derived from these orbitals, indicating its stability. These findings were supported by molecular electrostatic potential maps, revealing electrophilic and nucleophilic attack regions on the structure. Polarizability anisotropy (∆α) and hyperpolarizability (β) values were calculated as 73.3003Å3 and 5.46547x10-29 cm5 e.s.u.-1, respectively, indicating the structure’s high polarizability feature. Natural bond orbital analysis elucidated the nature of intramolecular hydrogen bonding and delocalization between electron-donor and acceptor-type orbitals. Finally, Mulliken charge analysis supported electrophilic and nucleophilic binding regions within the structure.

Keywords

• Schiff base
• physical and chemical properties
• quantum mechanical calculations

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