Structural Studies of the Interaction between Indole Derivatives and Biologically Important Aromatic Compounds. I. The Crystal and Molecular Structure of the Indole-3-acetic Acid-Nicotinamide (1:1) Complex

The title complex crystallizes in the monoclinic space group P21/c. The unit-cell dimensions are a=11.287(5), b=5.110(3), c=26.391(3) Å, and β=107.07(2)°. The crystal structure was solved by a direct method. By block-diagonal least-squares refinements, the R-value dropped to 0.069. All the nitrogen and oxygen atoms in the complex participate in the hydrogen bonding. No prominent overlapping between pyridine and indole rings is observed in the crystal. Both molecules are hydrogen-bonded to form infinite-layered structures perpendicular to the c-axis; those structures are held together by van der Waals contacts.