Experimental observation of supramolecular carbonyl-π/π-π/ π-carbonyl and carbonyl-π/π-π/π-anion assemblies supported by theoretical studies

Somnath Ray Choudhury, Patrick Gamez, Arturo Robertazzi, Chih Yuan Chen, Hon Man Lee, Subrata Mukhopadhyay

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Abstract

Mononuclear nickel(II) and copper(II) complexes, namely, (C 6H9N2)2[Ni(ntaH)2] (1), (C5H7N2)2[Cu(mal)2(H 2O)2] (2), and (C5H7N 2)4[Ni(mal)2(H2O) 2](NO3)2 (3) [ntaH3 = nitrilotriacetic acid; C6H8N2H = protonated 2-amino-4-picoline; malH2 = malonic acid; C5H 7N2 = protonated 2-aminopyridine] have been synthesized in water and their crystal structures have been determined by single crystal X-ray diffraction. In all the complexes, robust bimolecular cyclic hydrogen bonding R22(8) motifs are observed between the protonated heteroaromatic N-rings and the metal-carboxylate complexes. Moreover, the aromatic molecules are engaged in carbonyl⋯ π and ⋯π interactions with the noncoordinated carbonyl moieties of the metal complexes and with a nitrate ion respectively, giving rise to remarkable carbonyl ⋯π/π⋯π/carbonyl⋯π and carbonyl ⋯π/π⋯π/π⋯-anion interactions having sandwich type topologies. In 1 and 3, the carbonyl ⋯π interactions are one of the weak forces responsible for the stabilization of the final assemblies, whereas in 2, it strongly contributes to the stabilization of the one-dimensional tape generated from monomeric [Cu(mal)2(H 2O)2]2- units. Density functional theory studies reveal a high stability of the unique lone pair ⋯π/ π⋯π/lone pair ⋯π supramolecular self-assembly observed in compound 2 and confirm the favorable formation of the lone pair ⋯π/π⋯π/π⋯anion array present in compound 3. Compounds 1-3 are compared in terms of synthetic aspects and supramolecular interactions with analogous complexes, that is, {[Cu(mal)2](picH) 2· 5H2O}n (4), {[Cu(mal) 2](picH)2· 2H2O}n (5), (picH)2[M(mal)2(H2O)2] ·4H2O (M = Ni/Co/Mn) (6-8), recently obtained with picoline (picH = protonated picoline). The self-assembly pathways involved in the recognition of the heterocyclic amines by the metal-carboxylate complexes and the occurrence of lone pair (l.p.)⋯π and anion ⋯π interactions are examined and related.

Original languageEnglish
Pages (from-to)3773-3784
Number of pages12
JournalCrystal Growth and Design
Volume8
Issue number10
DOIs
Publication statusPublished - 2008 Oct 1

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All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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