Solid-state structure of free base guanidine achieved at last.

"Crystal structure of the free base guanidine determined 148 years after the first synthesis": A prototype structure unveiled--despite its provocative simplicity, the crystal structure of guanidine has not been previously described. 148 years after the first synthesis of guanidine, we now find two Y-shaped symmetry-independent molecules in the unit cell that are interconnected by a hydrogen-bonding network, which results in a fascinating layered structure (see picture).