Monosubstituted acetonitriles: Structure, spectroscopic characterization and hyperpolarizabilities

We have studied the structure, vibrational spectra, electronic absorption spectra and first and second hyperpolarizabilities (β and γ) of monosubstituted acetonitrile using quantum chemical methods. The substituents used here are F, Cl, Br, CH3 and NH2. Among different levels of theory used here for the calculations, the geometrical parameters, dipole moment and vibrational frequencies for the acetonitrile at B3LYP/aug-cc-pvdz level are in agreement with the experimental determinations. A large change in the vibrational and electronic absorption spectrum of acetonitrile is observed upon monosubstitution. The bromosubstituted acetonitrile shows the highest β and γ values and absorption intensities in electronic absorption spectrum among different molecules studied here. All the molecules show large HOMO–LUMO gap even for a strong applied field of 0.012 a.u. (>6 eV). The β and γ values of bromoacetonitrile are about 25 and 9 times higher respectively than those for the acetonitrile.

► Monosubstituted acetonitrile as nonlinear optical material.
► Bromoacetonitrile shows the highest β and γ values among the studied monosubstituted acetonitrile.
► Shifting of absorption maximum to the lower wavelength for all the monosubstituted acetonitrile studied.
► Potential application in area of photonics.