Crystal structure of a complex between p-nitrophenol and 2-pyridone.

attracted considerable interest in recent years, especially in relation to homeostases of lifeforms. Among such recognitions, hydrogen bonding is the most frequently evaluated, since it is indispensable for nucleic acid derivatives to hybridize and function. The key components in hydrogen-bond formations of biomolecules are defined as amide (or lactam) structures. Previously, on the acylation of p-nitrophenol with 2trifluoroacetoxypyridine, we isolated complex 1 instead of obtaining the expected reaction products and found it to be composed of p-nitrophenol and 2-pyridone in a 1:1 ratio.1 Here, we wish to report the details of the crystal structure of complex 1. Solutions of 2-pyridone and p-nitrophenol in Et2O were prepared separately. Equimolar amounts of each were mixed and the mixture was kept for 2 h at room temperature to precipitate crude 1. The crude 1 was subjected to a slow recrystallization from its dilute solution in Et2O to give pure 1. Crystal and experimental data are listed in Table 1. The nonhydrogen atoms were refined anisotropically. All hydrogen atoms were located from a difference Fourier map and included in the final cycle of the full-matrix least-squares refinements. Positional parameters for non-hydrogen atoms are listed in Table 2. The crystal structure of complex 1 is shown in Fig. 1, together with the atomic labeling scheme. Selected intraand intermolecular bond distances and angles are listed in Table 3. In the crystal structure of 2-pyridone, C=O and N–H groups were linked by hydrogen bonds, the head-to-tail type repetition 619 ANALYTICAL SCIENCES MAY 2002, VOL. 18 2002 © The Japan Society for Analytical Chemistry