Computation of electrical responsive properties and global reactivity descriptors along the proton transfer co-ordinate of donor–acceptor substituted pyrazole derivatives

Abstract

Ground and excited-state proton transfer and electrical responsive properties along the proton transfer co-ordinate of four donor–acceptor substituted pyrazole derivatives have been investigated using the density function-based range separated hybrid GGA functional ωB97XD with 6-311G(d) basis. Both intrinsic reaction coordinate (IRC) and distinguished co-ordinate (variation of O–H distance of the enol tautomer) have been chosen as a proton transfer co-ordinate of the titled compounds for comparison. Our study reveals that the various electrical responsive parameters like average polarizability (α_av), first hyperpolarizability (β_av) and global reactivity descriptors e.g., chemical hardness (η), electrophilicity index (ω) along the proton transfer co-ordinate are in conformity with the respective optimum principles. Maximum value of β_av is found in the case of nitro substituted pyrazole derivative. Variation of β_av along the proton transfer co-ordinate for all compounds have been correlated with the variation of Δµf₀/(S₁-S₀)³ using two-level approximation and electronic special extent (<R²>) along the proton transfer coordinate.

GRAPHICAL ABSTRACT

KEYWORDS:

• DFT
• polarizability
• first hyper-polarizability
• chemical hardness
• electrophilicity index

Acknowledgments

R.M and U.M thank UGC-BSR and UGC (ref. no. 188/(CSIR-UGC NET JUNE 2019) for their individual research fellowship. Departmental computational facilities from DST-FIST (Ref. No. SR/FST/CSI-235/2011) and UGC-SAP (Ref. No. F.5- 9/2015/DRS-11 (SAP-11) programmes are gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by DST SERB New Delhi [grant number SR/FST/CSI/2017/7(C)]; University Grants Commission [grant number F.5- 9/2015/DRS-11].