Weak interactions involving organic fluorine: a comparative study of the crystal packing in substituted isoquinolines

Weak interactions involving fluorine have been analyzed in the structure of 6-methoxy-1,2-diphenyl-1,2,3,4-tetrahydroisoquinoline with fluorine substitution at para-, meta- and ortho- positions, respectively, on the 1-phenyl ring. The packing modes in the crystalline lattice as determined by X-ray diffraction techniques generate motifs via (FF)-F-..., C-(HF)-F-... and C-F(...)pi interactions. The three structures as compared to the parent compound depict conformational changes in the saturated tetrahydroisoquinoline moiety. The salient features of the four structures in terms of weak interactions involving fluorine suggest that organic fluorine does resemble the other halogens. (C) 2002 Elsevier Science B.V. All rights reserved.