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

Abstract A previously unobserved crystalline precipitate in an extract of crude 1-(aminomethyl) pyrene was shown to be 1-(isopropylideneaminomethyl)pyrene. The identity of this compound was established by a single crystal X-ray determination that revealed an overall planar arrangement for the non-hydrogen atoms. The molecule crystallized in the monoclinic space group P 2 1 / c , with the following unit cell dimensions: a=11.6650(10) A , b=8.2850(9) A , c=16.0220(9) A , β =108.297(6)°, V=1470(2) A 3 , and Z =4. The structure was refined to R =0.059 ( R w =0.150) for 2576 data points with F o 2 >2 σ ( F o 2 ). The results of ab-initio-calculations at the STO-3G level suggest that the difference in rotational conformer energy for rotation about the C–N single bond varied by less than 1 kcal/mol between the maximum (−30°) and minimum (90°) values. Packing forces in the solid state arrangement are believed to be responsible for the difference between this result and experiment, since an AM1 calculation with 1 constrained between two molecules of 1 at the experimental distances led to the planar structure as the one with lowest energy.