Aromaticity of 1,4-dehydrotropylium ion and its mono- and poly-phospha analogues

GRAPHICAL ABSTRACT

ABSTRACT

The tropylium ion and its mono- and poly-phospha analogues on removal of two hydrogen atoms from 1,4-positions accompanied by the formation of a σ C–C bond afford 1,4-dehydrotropylium ion and its mono- and poly-phospha analogues. Aromaticity of these compounds along with 3-aza-1,4-dehydrotropylium ion, 1,4-dehydrotropilidine and its 3-phospha-analogoue has been investigated at the DFT(B3LYP/6-31+G^*) level using geometry, ASE, ¹H NMR chemical shifts, NICS and magnetic susceptibility exaltation descriptors. 1,4-Dehydrotropylium ion and its mono- and poly-phospha analogues having up to four P atoms along with 3-aza-1,4-dehydrotropylium ion sustain aromaticity like their parent systems. However, 1,4-dehydrotropilidine and its 3-phospha-analogue are found to be nonaromatic.

KEYWORDS:

• 1,4-Dehydrotropylium ion
• 1,4-dehydrophosphatropy-lium ion
• 1,4-dehydrodiph-osphatropylium ion
• 1,4-deh-ydropolyphosphatropylium ion
• aromaticity
• DFT calculations

Supplemental materials

Cartesian coordinates of the optimized geometries (TS1), total energies (TS2), calculation of the magnetic susceptibility exaltation values (TS3) and second order perturbations (TS4) of all species can be found in Supplementary materials (Tables S 1–S 4).

Acknowledgment

Thanks are due to the authorities of the IIS University, Jaipur, India, for providing necessary facilities.