Once upon a time (May, 1988), I was presented with crystals of 7-azaindole:
A preliminary investigation indicated that the cell was triclinic with a=11.297(2), b=14.918(2), c=15.513(2)Å , a=76.98(1), b=108.71(1), g=89.28(1)° and V=2402(1)Å3 . This cell required that Z=16 (Dcalc=1.306 g/cm3). Never having seen a Z' of 8, I was reluctant to bother to collect data, but the crystals were very beautiful and it was a slow week, so data was collected on a CAD4 diffractometer using Cu radiation. All attempts to solve the structure with the direct methods programs I had then were unsuccessful . The data sat "on the shelf" for a year or so until I got a new version of MULTAN. In the course of testing this new software, I attempted the solution of 7-azaindole and, lo-and-behold, it worked. There WERE eight molecules in the asymmetric unit. The molecule forms tetramers due to hydrogen bonding between the pyrole N-H and the pyridine N. The asymmetric unit consists of two tetramers (hydrogen bonds are in red):
Unfortunately for me, at about the time I was solving the structure with my new MULTAN (Oct., 1989), A.L. Beauchamp and co-workers were submitting the structure determination of 7-azaindole for publication in the Canadian Journal of Chemistry (P. Dufour, Y. Dartiguenave, M. Dartiguenave, N. Dufour, A-M. Lebuis, F. Bélanger-Gariépy, and A.L. Beauchamp, Can.J.Chem., 68, 193, 1990.)
The next page displays a unit cell packing diagram of 7-azaindole.