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

Abstract

We present here two different coordination polyhedra of pincer type N 2 O hydrazone based ligands supplemented with thiocyanate ions. The compounds namely [Hg(SCN) 2 (HL 1 )] (1) and[Hg(SCN) 2 (HL 2 )] (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 (HL 1 ), and 2-acetylpyridineisonicotinoylhydrazone (HL 2 ). In compound 1 the ligand coordinated to the mercury center in the keto form (=N-NH=C=O) whereas, in compound 2, the proton at the hydrazine group have 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 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, MolecularElectrostatic Potential surface and the Bader's theory of atoms in molecules.

Crystal structure and Hirshfeld surface analysis of 3-amino-1-oxo-2,6,8-triphenyl-1,2,7,8-tetrahydroisoquinoline-4-carbonitrile

“…For many decades, considerable interest in organic and medicinal chemistry has been directed toward the synthesis of various biologically valuable nitrogen heterocycles (Mamedov et al, 2019;Naghiyev, 2019;Kerru et al, 2020). They are prevalent structural motifs in many compounds, also having applications in coordination chemistry and material science (Zubkov et al, 2018;Mahmoudi et al, 2019;Velá squez et al, 2019). The majority of tetrahydroisoquinoline moieties containing antitumor antibiotics, such as saframycins, renieramycins, safracins, ecteinascidins, tetrazomine, lemonomycin, dnacins and aclindomycins, have already been isolated from natural sources and reproduced applying different effective techniques (Scott & Williams, 2002).…”

Crystal structure and Hirshfeld surface analysis of 4,5-dibromo-6-methyl-2-phenyl-2,3,3a,4,5,6,7,7a-octahydro-3a,6-epoxy-1H-isoindol-1-one

“…It can on the one hand be the halogen-initiated Wagner-Meerwein cationic rearrangement (Jung et al, 1985;Ciganek et al, 1995;Zubkov et al, 2004Zubkov et al, , 2018Zaytsev et al, 2020), or on the other hand we can observe electrophilic addition of halogens to multiple bonds (Berson et al, 1954;Barlow et al, 1971;Kobayashi et al, 1976;Solov'eva et al, 1984). Halogenated organic compounds are of interest because of their photoactivity in the solid state, high solubility in halocarbons, high thermal and oxidative stability, etc., to which non-covalent halogen bonding can contribute (Afkhami et al, 2017;Maharramov et al, 2018;Mahmoudi et al, 2017Mahmoudi et al, , 2019Shixaliyev et al, 2014). In view of its higher directionality, the halogen bond can be better suited than the hydrogen bond for the building of functional materials by non-covalent self-assembly via specific molecular interactions Kopylovich et al, 2011;Ma et al, 2017aMa et al, ,b, 2020Mahmudov et al, 2012Mahmudov et al, , 2013Mahmudov et al, , 2019Mahmudov et al, , 2020.…”

Crystal structure and Hirshfeld surface analysis of 4,5-dibromo-2-(4-methoxyphenyl)-2,3,4,4a,5,6,7,7a-octahydro-1H-4,6-epoxy-1H-cyclopenta[c]pyridin-1-one

“…(Asadov et al, 2016;Gurbanov et al, 2017Gurbanov et al, , 2018Karmakar et al, 2017;Kopylovich et al, 2011;Ma et al, 2017a,b;2020;Mahmudov et al, 2010Mahmudov et al, , 2012Mahmudov et al, , 2013Mahmudov et al, , 2019Mahmudov et al, , 2020Mizar et al, 2012;Sutradhar et al, 2015Sutradhar et al, , 2016. Halogen bonding is a rather spread phenomenon since halogen atoms or ions can form short non-bonding contacts with electron acceptors, electron donors or be interconnected due to anisotropic charge distribution in halogen atoms (Afkhami et ISSN 2056-9890 al., 2017Maharramov et al, 2018;Mahmoudi et al, 2017Mahmoudi et al, , 2019Shixaliyev et al, 2014). In fact, functionalization of isoindoles with donor or acceptor sites for non-covalent bonding greatly affects their supramolecular arrangements (Gurbanov et al, 2021).…”