Structures and considerable static first hyperpolarizabilities: New organic alkalides (M⁺@n⁶adz)M′- (M, M′ = Li, Na, K; n = 2, 3) with cation inside and anion outside of the cage complexants

Eighteen structures of new organic alkalides (M⁺@n ⁶adz)M′^- (M, M′ = Li, Na, K; n = 2, 3) with the alkalimetal cation M⁺ lying near the center of the adz cage and the alkali-metal anion M′^- located outside are obtained with all real frequencies. They exhibit very large static first hyperpolarizabilities (ß₀) up to 3.2 × 10⁵ au, which exceeds the record value of ß₀ = 1.7 × 10⁵ au for nonlinear optical compounds [Chem. - Eur. J. 1997, 3, 1091], All potassides (M⁺@n⁶adz)K^- (M = Li, Na, K; n = 2, 3) have considerably large ß₀ values (1.6 × 10⁵-3.2 × 10⁵ au) much larger than the ß₀ value (3.6 × 10⁴ au) of the previously designed cuplike alkalide Li ⁺(calix[4]pyrrole)K^- [J. Am. Chem. Soc. 2006, 128, 1072]. This shows that the ²⁶adz and ³⁶adz cage complexants are preferable to cuplike calix[4]pyrrole complexant in enhancing the first hyperpolarizability. The effect of cage size of the complexant on the first hyperpolarizability is also presented here: in most cases, the smaller cage complexant corresponds to the larger ß₀ value. Moreover, the crucial role by the alkali-metal anion in the large first hyperpolarizability of these alkalides is revealed. These results may provide new means for designing high-performance nonlinear optical materials.