Theoretical study of structural effects on reactivity and stability of isomeric pyrano-, thiopyrano-, and selenopyranopyrroles
In this study, global and local DFT reactivity descriptors for isomeric pyrano-, thiopyrano- and selenopyranopyrroles have been calculated. The geometric optimization of the obtained structures was realized with the density functional theory (DFT, B3LYP) at the level of 6-31G(d) and show these isomers have planar configurations. The structural properties such as dipole moments, bond lengths and bond angles of these isomers were calculated. The heats of formation have also been calculated based on the optimized geometry. The energies of HOMO and LUMO molecular orbitals are used to determine several global descriptors as a measure of their electronic properties, relative stabilities and chemical reactivities. These include total energy (E), ionization potential (I), electron affinity (A), chemical hardness (η), chemical softness (S), electronic chemical potentials (μ) and electrophilicity (ω). Selenopyrano[2,3-c]pyrrole possesses the highest electrophilicity and minimum chemical hardness among the calculated isomeric structures. The largest calculated dipole moment belongs to pyrano[3,2-b]pyrrole, while thiopyrano[3,4-b]pyrrole has the lowest.
DFT calculations; Fused pyrrole; Electrophilicity; Energy gap; Azaheterocycle; Global descriptor.
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