Modulation of coordination in pincer-type isonicotinohydrazone Schiff base ligands by proton transfer

We present here two different coordination polyhedra of pincer type N2O hydrazone based ligands supplemented with thiocyanate ions. The compounds namely [Hg(SCN)2(HL1)] (1) and [Hg(SCN)2(HL2)] (2) have a common isonicotinohydrazone fragment and have been prepared by using a coordination driven self-assembly of the Hg(SCN)2 with two different ligands including 2-benzoylpyridine-isonicotinoylhydrazone (HL1), and 2-acetylpyridine-isonicotinoylhydrazone (HL2). In compound 1 the ligand coordinates to the mercury center in the keto form (N-NHCO) whereas, in compound 2, the proton at the hydrazine group has been shifted to the uncoordinated pyridine ring and the ligand acted as a zwitterion. The structures provide a complementary system for proton transfer within the ligand molecule involving the keto-enol tautomerization of the amide group and 4-pyridyl N protonation. As a result, the relative location of orbitals and ligands in the complexes are different as well as the bonding strength and the coordination polyhedra. We have also studied electrostatically enhanced π⋯π (either conventional or involving the chelate ring) interactions observed in the solid state of both compounds and analyzed them using DFT calculations, molecular electrostatic potential surface and Bader's theory of atoms in molecules. © 2019 The Royal Society of Chemistry.

Mahmoudi G. 1 , Khandar A.A.2 , Afkhami F.A.2 , Miroslaw B.3 , Gurbanov A.V. 4, 5 , Zubkov F.I. 6 , Kennedy A.7 , Franconetti A.8 , Frontera A.8
Royal Society of Chemistry
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  • 1 Department of Chemistry, Faculty of Science, University of Maragheh, P.O. Box 55181-83111, Maragheh, Iran
  • 2 Department of Inorganic Chemistry, Faculty of Chemistry, University of Tabriz, P.O. Box 5166616471, Tabriz, Iran
  • 3 Department of Crystallography, Faculty of Chemistry, Maria Curie-Sklodowska University, Pl. Marii Curie-Sklodowskiej 3, Lublin, 20-031, Poland
  • 4 Department of Organic Chemistry, Baku State University, Z. Khalilov str. 23, Baku, AZ 1148, Azerbaijan
  • 5 Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa, 1049-001, Portugal
  • 6 Organic Chemistry Department, Faculty of Science, Peoples' Friendship University of Russia (RUDN University), 6 Miklukho-Maklaya St., Moscow, 117198, Russian Federation
  • 7 Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow, G1 1XL, United Kingdom
  • 8 Departament de Química, Universitat de les Illes Balears, Crta. de Valldemossa km 7.5, Palma de Mallorca, Baleares, 07122, Spain
Ключевые слова
Amides; Geometry; Mercury compounds; Molecules; Proton transfer; Self assembly; Atoms in Molecules; Complementary systems; Coordination polyhedra; Coordination-driven self assembly; Ligand coordinates; Molecular electrostatic potentials; Relative location; Schiff-base ligands; Ligands
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