ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Manipulation of planar structure of 1,2,5- and 1,3,4-triazoles and the pseudo Jahn–Teller effect in their 1-pnictogen derivatives

Ali Reza Ilkhani

Islamic Azad University, Yazd Branch, Yazd, Iran

E-mail: ilkhaniali@iauyazd.ac.ir

Abstract: The planar structure of 1,2,5- and 1,3,4-triazoles were manipulated through (i) the replacement of 1-nitrogen in the ring by other nitrogen family atoms, and (ii) joining two triazoles from the 1–1 position at the rings. Calculated geometrical parameters of those manipulated triazole derivatives in both planar and puckered configurations revealed that 1-nitrogen substituted triazole structures have lost their planarity. Due to adiabatic potential energy surface cross-section and electron configurations of the puckered compounds, electron excitation from the 1A₁ ground to low-lying 1B₁ excited states is the reason for planar instability in the series which was formulated as the PJTE (1A₁ + 1B₁ + 2A₁) ⊗b₁ problem. Moreover, joining two triazole rings via 1–1 ring positions affected the stability of 1,2,5- and 1,3,4-triazole rings and amplify the puckering in other bicyclic tripnigole series. Due to the biological activities of triazole, manipulation of its structure may help us to discover more potent and specific triazole drugs or consequently, reduce its side effects.

Keywords: PJTE ; Triazoles ring planarity ; Structure manipulation ; Vibronic coupling constant 

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-018-0567-7

Chemical Papers 73 (1) 85–94 (2019)