Theoretical study of borazine and substituted borazines using density functional theory method

•Borazine and substituted borazines are studied using DFT method.•Substituted borazines show higher hyperpolarizabilities than borazine.•Vibrational frequencies from this work are in agreement with the experiment.•Large hyperpolarizabilities for substituted borazines have potential application in photonics.

Borazine and donor-acceptor substituted borazines have been studied by density functional theory method. We have used NH2 as a donor and NO2, CN, COCl and NMe2 as acceptor groups. The geometrical parameters, vibrational frequencies, NLO properties and electronic absorption spectra have been obtained at B3LYP/6-311++G** level of theory. Calculated structural parameters and vibrational frequencies for borazine at this level of theory are in excellent agreement with the available experimental determinations. The BN stretching mode is the most intense vibrational mode observed in vibrational spectra of borazine and substituted borazines. The vibrational frequency for this mode is observed in a range of 1435 to 1585 cm− 1. For the calculations of first (β) and second (γ) hyperpolarizabilities, the finite field approach has been used. Direction of applied field, method and basis set dependent hyperpolarizabilities are obtained. The hyperpolarizabilities are found to be enhanced upon donor and acceptor substitution in borazine. For all the substituted borazines, the β and γ values are higher than those for the unsubstituted borazine.