Role of non-covalent interactions in three copper(II) 5-chloro-2-nitrobenzoate complexes with N-donor ligands: Syntheses, characterization and packing analyses of trans-[Cu(β-pic)2(H2O)2(5-chloro-2-nitrobenzoate)2], trans-[Cu(γ-pic)2(5-chloro-2-nitrobenzoate)2] and [trans-Cu(en)2(H2O)2](5-chloro-2-nitrobenzoate)2·2H2O

Abstract

Three new copper(II) complexes trans-[Cu(β-pic)2(H2O)2(5-chloro-2-nitrobenzoate)2] 1, trans-[Cu(γ-pic)2(5-chloro-2-nitrobenzoate)2], 2 and [trans-Cu(en)2(H2O)2](5-chloro-2-nitrobenzoate)2·2H2O, 3 (where β-pic=β-picoline, γ-pic=γ-picoline and en=ethylenediamine) were prepared by the addition of β-pic, γ-pic and en, respectively, to the hydrated copper(II) 5-chloro-2-nitrobenzoate, suspended in methanol–water mixture (4:1, v/v). The newly synthesized complexes have been characterized by elemental analyses, TGA, spectroscopic techniques (FT-IR, UV–Vis and EPR), conductivity measurements, magnetic susceptibility studies and single crystal X-ray structure determination. Complex 1 crystallizes in monoclinic crystal system with P21/c space group whereas the complexes 2 and 3 crystallizes in triclinic crystal system with P1¯ space group. Single crystal X-ray structure determination revealed the presence of elongated octahedral geometry in all three complexes. Cu(II) center is covalently coordinated by two 5-chloro-2-nitrobenzoate, two β-pic moieties and two water molecules in complex 1, two bidentate 5-chloro-2-nitrobenzoate and two γ-pic moieties in complex 2. In complex 3, the copper ion is coordinated to two chelating en ligands, two water molecules; with two 5-chloro-2-nitrobenzoate as counter anions and two water molecules of crystallization. The crystal lattice in complexes 1–3 is stabilized by an intricate network of hydrogen bonding interactions (C–H…O, O–H…O in complex 1, C–H…O in complex 2 and O–H…O, N–H…O and C–H…O in 3). Besides this, π…π stacking interactions in complex 1 and C–H…π interactions in complex 2 also contribute towards stability of the crystal lattice.