Fig. 1. (a) Structure of the zwitterion in 1 (ellipsoids in 50% probability). (b) A 2D hydrogen-bonded layer with intermolecular interactions. (c) Three-dimensional organic network. Symmetry code: A = x, 0.5 – y, 0.5 + z; B = x, 0.5 – y, –0.5 + z; C = 1 + x, 0.5 – y, 0.5 + z.