Crystal structure of 5-iodouracil

Abstract

Crystals of 5-iodouracil are monoclinic, space group P21, with a= 14.210 (1), b = 4"458 (1), c= 4"899 (3) A, and r= 92.31 (1) °. There are two formula units per cell. Observed and calculated densities are 2-54 and 2.548 g cm -3, respectively. Intensity data for 591 reflections were collected on an automatic diffractometer. The structural parameters were refined by full-matrix least-squares calculations to an R index of 0.044. The molecules form planar, hydrogen-bonded ribbons, which are stacked with an inter-ribbon spacing of 3" 15 A and an 1. • • C(6) distance of 3"76/l, that is slightly shorter than a normal van der Waals contact. 1393

Simulation of a tetramer form of 5-iodouracil: The vibrational spectra and molecular structure in the isolated and in the solid state by using DFT calculations

“…Nevertheless small deviations of the planarity [41,42] have been reported in the crystal due to the intermolecular H-bonds. Our simulations in the tetramer form also show these deviations, in general with values slightly higher than in the crystal.…”

“…1. Although X-ray data of complexes of 5-IU with metal transitions [39] and with dihydropyrimidine dehydrogenase [40] have been reported, few data appears for the crystal of 5-IU [41,42], the recent one is included in the Table. For comparison purposes, the experimental values obtained by X-ray in U [43][44][45] are also collected in the last column.…”

“…This fact was not observed in our simulation, and in the three tetramers the iodine atom appears always oriented out-of the other 5-IU molecules, with a distance higher than 4.6 Å from a carbon atom of an adjacent 5-IU molecule. It has been reported [41] that in the crystal the iodine atom affects the solid state base-stacking patterns, and it has been suggested that stacking interactions involving this atom may contribute to the unusual physical and biological properties of this molecule.…”

Assessment of electron irradiation damage to biomolecules using the Patterson function

“…l(a) with Fig. 2 which was drawn using the known atomic coordinates of 5-iodouracil (Sternglanz et al, 1975), using an autocorrelation technique (Buerger, 1959). Since there are a total of eighteen non-hydrogen atoms in the unit cell, each iodine atom should give rise to a total of seventeen non-origin peaks.…”

5-Iodouracil: structure of a reflection twin

“…The crystal structure of 5-iodouracil, (I), is known from the literature (Sternglanz et al, 1975;Portalone, 2008). The achiral molecule crystallizes in the noncentrosymmetric space group P2 1 .…”