“…Planarity, together with the rather short C(2)-N(11) distance (see Figure 1, C(2)-N(11) = 1.347(4)), attest to the contribution of the lone electron pair of N(11) into the purine π-system, a finding consistent with crystal structures of other 2-or 6-(dimethylamino)purines described in the literature. [20,21] The most closely related known structure, though, is 6-amino-2-(dimethylamino)-7-methylpurine (BIFFAX), [20] in which the corresponding distance was significantly longer (C(2)-N(11) = 1.381Å). At the same time, the N(7)-C(8) and C(8)-N(9) bond lengths in 10 are significantly closer to each other then in BIFFAX, confirming delocalization of electrons in the charged purine moiety (N(7)-C(8) = 1.325(4), 1.354; C(8)-N(9) = 1.343(4), 1.311 Å for 10 and BIFFAX, respectively).…”