Trifluralin and two of its photodegradation products: crystal structures and phase solubility/UV studies with cyclodextrins

ARGÜELLO, GUSTAVO A.; CAIRA, MINO R.; LOBATTO, VIRGINIA L.; BUJAN, ELBA I.

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY

JOHN WILEY & SONS LTD

Lugar: LOndres; Año: 2019 vol. 32 p. 1 - 11

0894-3230

The crystal structures of the herbicide trifluralin (1), and two of itsphotodegradation products, namely N-n-propyl-2,6-dinitro-4-trifluoromethylaniline (2)and 2-ethyl-7-nitro-5-trifluoromethyl-1H-benzimidazole 3-oxide (3) were determinedby single crystal X-ray diffraction. The presence of the N-hydroxy tautomer of 3 wasdetected in the solid state both by X-ray diffraction and infrared spectroscopy (IR),while in dimethyl sulfoxide-d6 ((CD3)2SO) solution the N-oxide tautomer wasobserved by Hydrogen-1 Nuclear Magnetic Resonance (1H NMR).In order to determine whether 1, 2, and 3 form complexes with cyclodextrins inaqueous solutions as well as in the solid state, the interaction of 1-3 with β-cyclodextrin in aqueous solutions containing 1% acetonitrile (ACN), and theinteraction of 1-3 in the solid state with both native and derivatized cyclodextrins wereinvestigated. In aqueous solutions containing 1% ACN, the association constants forthe formation of 1:1 complexes were calculated for 1 and 2 as (25 ± 7) × 101 M?1 and(18 ± 2) × 101 M?1, respectively, whereas that for 3 could not be determined.Extensive trials aimed at obtaining solid complexes of 1-3 with both native andselected crystalline derivatized cyclodextrins using different methods failed toproduce inclusion complexes.