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

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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 Δµf 0/(S 1-S 0)3 using two-level approximation and electronic special extent (<R 2>) along the proton transfer coordinate.