Three new pseudopolymorphs of 6-aminouracil

Abstract

Since 6-aminouracil derivatives show diversified use in various fields of application, we crystallized 6-aminouracil to examine its preferred hydrogen-bonding frameworks. 6-Aminouracil shows two rigid hydrogen-bonding sites, viz. one acceptor-donor-acceptor (ADA) site and one donor-donor-acceptor (DDA) site. During various crystallization attempts, we obtained three structures, namely two dimethylacetamide monosolvates, C4H5N3O2·C4H9NO, and a 1-methylpyrrolidin-2-one monosolvate, C4H5N3O2·C5H9NO. In all three structures, R2(1)(6) N-H...O hydrogen-bonding patterns link the molecules to their respective solvent molecules. The formation of R2(2)(8) N-H...O hydrogen-bond motifs between 6-aminouracil molecules can only be found in two-dimensional frameworks, whereas R3(3)(14) N-H...O patterns are present when zigzag chzins of 6-aminouracil molecules are formed.

6-Aminouracil: Geometries and spectra in the isolated state and in the solid state simulation. A comparison with 5-aminouracil

“…The bond lengths reported by X-ray appear in general with lower values than in our tetramer simulation, especially for those involving the N1eH and NH 2 groups [50]. Also the angles around these groups appear with large differences comparing with our values.…”

“…In 6-aminoU molecule the optimized ring structure is planar, which is in accordance to that determined in uracil molecule (U). Table 1 compares the calculated bond lengths and angles for 6-aminoU with those experimentally available by X-ray [50]. Of the three crystal structures obtained for 6-aminoU with solvent molecules, that one with dimethylacetamide monosolvate form was selected and included in the last column of Table 1.…”

“…In the X-ray study, 6-aminoU and dimethylacetamide molecules appear within the asymmetric unit [50]. In the crystal structure the molecules are associated to form ribbons stabilized by H-bonds involving carbonyl oxygen atoms and the NH groups, NeH$$$O.…”

“…3. Optimized tetramer form of 6-aminoU at the B3LYP/6-31G(d,p) level according to the crystal unit cell [50].…”