M@[12-crown-4] and M@[15-crown-5] where (M=Li, Na, and K); the very first examples of non-conventional one alkali metal-containing alkalides with remarkable static and dynamic NLO response

Abstract

Excess electron compounds , such as alkalides, were shown to be promising nonlinear optical (NLO) materials with higher static and frequency-dependent nonlinearities. The intriguing alkalides are obtained after doping the alkali metals with crown ethers M@[12-crown-4] and M@[15-crown-5] (where M=Li, Na, and K). The studied complexes are thermodynamically stable and their interactions energies range from −66.51 to −3.51 kcal mol −1 . The geometric, electronic, and nonlinear optical properties are validated through density functional theory at the CAM-B3LYP/6-31+G(d,p) level of theory. The significant (negative) NBO charge present on alkali metals reveals their alkalide characteristics. Furthermore, reduced HOMO-LUMO gaps for the designed complexes show their excellent electronic and conductive properties. Being excess electron candidate the significant static first hyperpolarizability value increased up to 1.2 × 10 7 au where the β vec response recorded up to 1.1 × 10 7 au. The total hyperpolarizability nicely correlates with hyperpolarizability ( β tl ) which suggests their excellent NLO properties. Besides, the dynamic hyperpolarizability response for electro-optical pockel's effect β(-2ω;ω,0) increases up to 3.5 × 10 7 au at dispersion frequency of 1064 nm. The dynamic hyperpolarizability responses for SHG are much pronounced at the larger dispersion frequency. The dynamic second hyperpolarizability response for the dc-Kerr effect increases up to 6.4 × 10 9 au. The frequency-dependent NLO response of M@[12-crown-4] alkalides is slightly larger than those of M@[12-crown-4]. Moreover, the hyper Rayleigh scattering hyperpolarizability (β HRS ) value is calculated up to 3.4 × 10 6 au. • Single alkali metal based non-conventional alkalides are proposed as excess electron compounds. • These shows better thermodynamic stabilities and significant interactions energies for M@[15-crown-5] complexes. • The higher hyperpolarizability response for Li@[15-crown-5] rose up to 1.2 × 10 7 au. • The remarkable frequency-dependent NLO properties at ω = 1064 nm.