Synthesis, H-1 NMR, single crystal X-ray determined and ab-initio molecular structural analyses on 1-(isopropylideneaminomethyl)pyrene

A previously unobserved crystalline precipitate in an extract of crude 1-(a minomethyl) pyrene was shown to be 1-(isopropylideneaminomethyl)pyrene. The identity of this compound was established by a single crystal X-ray determ ination that revealed an overall planar arrangement for the non-hydrogen at oms. The molecule crystallized in the monoclinic space group P2(1)/c, with the following unit cell dimensions: a = 11.6650(10) Angstrom. b = 8.2850(9) Angstrom, c = 16.0220(9) Angstrom, beta = 108.297(6)degrees, V = 1470(2) A ngstrom (3), and Z = 4. The structure was refined to R = 0.059 (R-W = 0.150 ) for 2576 data points with F-0(2) > 2 sigma (F-0(2)). The results of ab-in itio-calculations at the STO-3G level suggest that the difference in rotati onal conformer energy for rotation about the C-N single bond varied by less than 1 kcal/mol between the maximum (-30 degrees) and minimum (90 degrees) values. Packing forces in the solid state arrangement are believed to be r esponsible for the difference between this result and experiment. since an AM1 calculation with 1 constrained between two molecules of 1 at the experi mental distances led to the planar structure as the one with lowest energy. (C) 2001 Elsevier Science B.V. All rights reserved.