Chemistry Letters, Vol.30, No.10, 988-989, 2001
Polar assembly of 2,6-diethynylpyridine through C(sp(2))-H center dot center dot center dot N, C(sp)-H center dot center dot center dot pi and pi-pi stacking interactions: Crystal structure and nonlinear optical properties
The crystallization of 2,6-diethynylpyridine 1 leads to C(sp(2))-H . . .N hydrogen bonded head-to-tail tapes which are held together by C(sp)-H . . . pi hydrogen bridges to form 2D polar sheets; further assembly through pi-pi stacking interaction results in 3D polar crystals which show intense powder SHG response, 5-fold stronger than crystalline urea.