title: Anion induced formation of supramolecular associations involving lone pair-π and anion-π interactions in Co(II) malonate complexes: experimental observations, Hirshfeld surface analyses and DFT studies.
abstract: Three Co(II)-malonate complexes, namely, (C(5)H(7)N(2))(4)[Co(C(3)H(2)O(4))(2)(H(2)O)(2)](NO(3))(2) (1), (C(5)H(7)N(2))(4)[Co(C(3)H(2)O(4))(2)(H(2)O)(2)](ClO(4))(2) (2), and (C(5)H(7)N(2))(4)[Co(C(3)H(2)O(4))(2)(H(2)O)(2)](PF(6))(2) (3) [C(5)H(7)N(2) = protonated 2-aminopyridine, C(3)H(4)O(4) = malonic acid, NO(3)(-) = nitrate, ClO(4)(-) = perchlorate, PF(6)(-) = hexafluorophosphate], have been synthesized from purely aqueous media, and their crystal structures have been determined by single crystal X-ray diffraction. A thorough analysis of Hirshfeld surfaces and fingerprint plots facilitates a comparison of intermolecular interactions in 1-3, which are crucial in building supramolecular architectures. When these complexes are structurally compared with their previously reported analogous Ni(II) or Mg(II) compounds, a very interesting feature regarding the role of counteranions has emerged. This phenomenon can be best described as anion-induced formation of extended supramolecular networks of the type lone pair-π/π-π/π-anion-π/π-lone pair and lone pair-π/π-π/π-anion involving various weak forces like lone pair-π, π-π, and anion-π interactions. The strength of these π contacts has been estimated using DFT calculations (M06/6-31+G*), and the formation energy of the supramolecular networks has been also evaluated. The influence of the anion (NO(3)(-), ClO(4)(-), and PF(6)(-)) on the total interaction energy of the assembly is also studied.
authors.affiliation: Department of Chemistry, Jadavpur University, Kolkata 700 032, India.
authors.forename: Prankrishna
authors.initials: P
authors.lastname: Manna
authors.forename: Saikat Kumar
authors.initials: SK
authors.lastname: Seth
authors.forename: Amrita
authors.initials: A
authors.lastname: Das
authors.forename: Joanna
authors.initials: J
authors.lastname: Hemming
authors.forename: Richard
authors.initials: R
authors.lastname: Prendergast
authors.forename: Madeleine
authors.initials: M
authors.lastname: Helliwell
authors.forename: Somnath Ray
authors.initials: SR
authors.lastname: Choudhury
authors.forename: Antonio
authors.initials: A
authors.lastname: Frontera
authors.forename: Subrata
authors.initials: S
authors.lastname: Mukhopadhyay