Superhalogen doping: A new and effective approach to design materials with excellent static and dynamic NLO response


Excess electron generation through doping with alkali and superalkali metals is well-known to enhance NLO response. On the contrary, superhalogen doping is an unexplored dimension. Herein, we report ever-first examples where alone superhalogen doping is introduced as a new and effective approach to impart large NLO response. Density functional theory (DFT) calculations illustrate that superhalogen (BeF3 and BeCl3) doped cyclic oligofurans (nCF) possess exceptionally high NLO responses (first hyperpolarizability (βo), hyper-rayleigh scattering coefficient (βHRS), electro-optical Pockels effect (EOPE), second harmonic generation (SHG), and nonlinear refractive index (n2)) which is not trivial for organic compounds. Upon doping superhalogens, the first hyperpolarizability (βo) of nCF increases to 3×105 au in BeF3@6CF complex, whereas the βo values of BeF3@5CF, BeCl3@5CF and BeCl3@6CF complexes are 6×104, 3×104 and 4×104 au, respectively. Enormously large third order nonlinear optical response coefficient; electric field induced second harmonic generation (ESHG) value of 2.1×109 au is observed for BeCl3@6CF complex. The remarkable NLO response of superhalogen doped cyclic oligofuran complexes is due to the electron withdrawing nature of halogen atoms which are responsible to withdraw electrons from oxygen atoms of nCF to create poles. The significant hyperpolarizability (βo) of BeF3@6CF complex is due to the most electronegative nature of fluorine. Furthermore, these results are rationalized through two level model.Βvec values are calculated for these complexes because it gives more meaningful number from experimental point of view. The stability of the complexes is judged through interaction energies, whereas electronic properties are calculated by chemical reactivity descriptors, HOMO-LUMO gaps (Eg) and NBO charge transfer analysis. TD-DFT calculations reveals that the maximum absorbance for BeF3@6CF complex is shifted to longest wavelength.

DOI: 10.1039/D0NJ02291H