2-Chloro-4-fluorobenzoate vs. 2,4-dichlorobenzoate: A comparative study of non-covalent interactions in copper(II) 2-chloro-4-fluorobenzoate and copper(II) 2,4-dichlorobenzoate complexes with nitrogen-donor ligands

Abstract The coordination behavior of 2-chloro-4-fluorobenzoate and 2,4-dichlorobenzoate ligands towards copper(II) ion were investigated in the presence of different nitrogen ligands. Four new copper(II) complexes, [trans-Cu(2-Cl-4-FC 7 H 3 O 2 ) 2 (β-pic) 2 ] 1 , [trans-Cu(en) 2 (H 2 O) 2 ](2-Cl-4-FC 7 H 3 O 2 ) 2 , 2 , [trans-Cu(2,4-Cl 2 C 7 H 3 O 2 ) 2 (β-pic) 2 (H 2 O) 2 ], 3 and [trans-Cu(en) 2 (H 2 O) 2 ](2,4-Cl 2 C 7 H 3 O 2 ) 2 ·2H 2 O, 4 , (where β-pic = β-picoline, en = ethylenediamine) were synthesized by addition of β-picoline/ethylenediamine to the respective hydrated copper(II) arylcarboxylate suspended in methanol–water (4:1) mixture at room temperature. The newly synthesized complexes have been characterized by elemental analyses, TGA, spectroscopic techniques (FT-IR and UV–Vis), conductance, magnetic susceptibility studies. Single-crystal X-ray structure determination of the complexes revealed the presence of neutral structure in complexes 1 and 3 whereas complexes 2 and 4 possess ionic structure consisting of complex cation [trans-Cu(en) 2 (H 2 O) 2 ] 2+ and two 2-chloro-4-fluorobenzoate/2,4-dichlorobenzoate as counter anions. The crystal lattice in these copper(II) complexes is stabilized by various non-covalent interactions such as N H…O, O H…O hydrogen bonds and other weaker interactions including C H…π, C H…halogen and halogen…halogen ones. A comparison of non-covalent interactions in four copper(II) complexes is also discussed.