Unusual reverse face-to-face stacking in propylene linked pyrazole system: perspective of organic materials

Flexible dimers 1, 2, and 3 of pyrazole derivatives linked with propylene spacer are synthesized and conformational stability in solid, solution, and gaseous states is studied through single crystal X-ray diffraction, 2D NOESY ,and DFT, respectively. The folded conformation of compound 2 is stable in all three states and X-ray diffraction evince that molecule is intramolecularly stacked in reverse face-to-face manner. TEM image of compound 2 exhibits rigid hollow nanospikes with high tendency to form agglomerates.