Segregated aromatic π–π stacking interactions involving fluorinated and non-fluorinated benzene rings: Cu(py)2(pfb)2 and Cu(py)2(pfb)2(H2O) (py=pyridine and pfb=pentafluorobenzoate)

The syntheses, physical characterization and crystal structures of two new molecular copper(II) complexes of composition [Cu(C 5 H 5 N) 2 (C 7 F 5 O 2 ) 2 ] ( 1 ) and [Cu(C 5 H 5 N) 2 (C 7 F 5 O 2 ) 2 (H 2 O)] ( 2 ) (C 5 H 5 N = py = pyridine and C 7 F 5 O 2 −  = pfb = pentafluorobenzoate) are reported. Single-crystal X-ray structure determinations revealed that in 1 , the Cu 2+ ion, which lies on a crystallographic inversion centre, is coordinated to two py molecules and two oxygen atoms from two monodentate pfb anions, resulting in a trans -CuN 2 O 2 square planar geometry. In 2 , the Cu 2+ ion is also coordinated to two py and two pfb species in addition to a water molecule in the apical site of a distorted CuN 2 O 3 square pyramid. In the crystal packing, both 1 and 2 show segregated aromatic π–π stacking interactions in which (py + py) and (pfb + pfb) ring-pairings are seen, but no (py + pfb) pairings occur. Crystal data: 1 : C 24 H 10 CuF 10 N 2 O 4 , M r  = 643.88, space group P 1 ¯ , a  = 8.0777 (3) A, b  = 8.0937 (3) A, c  = 10.5045 (5) A, α  = 90.916 (3)°, β  = 93.189 (2)°, γ  = 118.245 (3)°, V  = 603.36 (4) A 3 , Z  = 1. 2 : C 24 H 12 CuF 10 N 2 O 5 , M r  = 661.90, space group P 1 ¯ , a  = 7.5913 (5) A, b  = 15.6517 (6) A, c  = 21.1820 (14) A, α  = 95.697 (4)°, β  = 94.506 (2)°, γ  = 91.492 (4)°, V  = 2495.2 (3) A 3 , Z  = 4.