Sonochemical synthesis of cadmium(II) coordination polymer nanospheres as precursor for cadmium oxide nanoparticles

Nanospheres of a new coordination polymer {[Cd 2 (µ-HL)(µ-L)(NO 3 ) 3 (H 2 O)]·H 2 O} n (1) were easily prepared by a sonochemical method from cadmium(II) nitrate and HL (HL, pyridine-2-carboxaldehyde isonicotinoyl hydrazone) in ethanol. Single crystals of 1 were also obtained using a branched tube method. The crystal structure of 1 indicates that the µ-HL/µ-L − blocks act as linkers between the Cd(II) centers, assembling them into 1D tooth-shaped interdigitated chains, which are further interlinked into a complex 3D H-bonded network with a rare hms(3,5-conn) topology. Nanoparticles of 1 were characterized by elemental analysis, FT-IR spectroscopy, and powder X-ray diffraction (XPRD), while their spherical morphology was confirmed by transmission electron microscopy (TEM). Furthermore, in the presence of a surfactant, the thermolysis of sonochemically generated nanoparticles of 1 led to the formation of cadmium oxide nanospheres (cubic CdO) with an average diameter of 10 nm. This study extends the application of sonochemical synthetic methods for the generation of phase pure nanoparticles of coordination polymers and their thermolysis products. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Effect of Fe3+–MMT nanocomposite content on thermal, mechanical and water resistance behavior of PVP/amylose films

Novel nanocomposite films based on amylose (AM) and Fe3+–montmorillonite (Fe3+–MMT) in the matrix of poly(vinyl pyrrolidone) (PVP) were fabricated using a solution casting method. X-ray diffraction indicated that an ion exchange process occurred between Fe3+–MMT and PVP/AM. Thermogravimetric analysis and differential scanning calorimetry results hinted to PVP/AM films forming a more stable network through the dispersion of Fe3+ cations. An increase in the loading of Fe3+–MMT improved the hydrophilic properties of PVP/AM films, which lead to the high degree of resistance against the water absorption. Mechanical properties of PVP/AM films influenced by the uniform dispersion of Fe3+–MMT in the polymer network established strong covalent interactions between PVP/AM and Fe3+–MMT. This interaction not only improved the mechanical properties of the films, but also enhanced the thermal stability of them through the facilitation of the MMT dispersion within the polymer matrix. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature

Chelate ring stacking interactions in the supramolecular assemblies of Zn(ii)and Cd(ii) coordination compounds: a combined experimental and theoretical study

The self-assembly of Zn(ii) and Cd(ii) ions with two isomeric tetradentate ligands, 2-pyridyl-isonicotinoylhydrazone (HL1) and 2-benzoylpyridyl-picolinoylhydrazone (HL2), was studied by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction. The reaction of zinc(ii) and cadmium(ii) salts with HL1 and HL2 in methanol under solvothermal conditions produced six monomer and one tetranuclear zinc(ii) complexes, namely, Zn(HL1)Br2 (1), Zn(HL1)Cl2 (2), [Cd(HL1)2](NO3)2·H2O (3), Cd(HL2)Br2(4), Zn(HL2)Cl2 (5), Zn(HL2)Br2 (6) and [Zn4(L2)4I2][ZnI4]·2H2O (7). The structure of 7 includes a cationic tetranuclear cluster of four zinc ions, four ligands, and two anions, counterbalanced by ZnI4 2− ions. However, the reaction of zinc(ii) and cadmium(ii) salts with HL1 under the same conditions produced monomer compounds. Herein, the ligand effects on the complex structures were studied. Hirshfeld surface analysis and fingerprint plots facilitate the comparison of intermolecular interactions in compounds 1-7, which are crucial in building supramolecular architectures. © The Royal Society of Chemistry

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

Polar protic solvent-trapping polymorphism of the HgII-hydrazone coordination polymer: Experimental and theoretical findings

A novel series of HgII coordination polymers with a general formula [HgL(N)3]n·n(solv) (HL = 2-pyridinecarbaldehyde isonicotinoylhydrazone; n(solv) = 0.5H2O (1), 2MeOH (2), EtOH (3), PrOH (4) and 0.5BuOH (5)) was prepared and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. The crystal structure of HL, elucidated by X-ray diffraction, comprises two independent molecules in the asymmetric unit cell, each of which is stabilized by an intramolecular hydrogen bond formed between the carbohydrazide hydrogen atom and the 2-pyridyl nitrogen atom. Crystal structures of 1-5 each reveal a similar 1D zigzag metal-organic chain [HgL(N)3]n, where the organic ligands bridge metal centers. These chains are extended into distinct 2D supramolecular nets by strong hydrogen bonds with the solvent molecules and/or short Hg⋯N supramolecular contacts. These networks were topologically classified as the hcb in 1 and fes in 2-5 underlying nets. On comparing the H-bonding patterns, it can be concluded that the lattice water molecules in 1 and methanol molecules in 2 form H-bonding interactions with the O and amide N atoms of L in the former structure and the O atom of L in the latter structure. In the remaining coordination compounds, the lattice solvent prefers the azide N atom for H-bonding. Furthermore, the existence of Hg⋯N interactions in 2-5 and their absence in 1 clearly highlights the importance of the size and polarity of the solvents on the self-assembly generation of HgII coordination polymers. A broad network of intermolecular π⋯π stacking interactions, formed between the pyridyl fragments, provide further reinforcement of crystal packing patterns in the structures of HL and 2-5. DFT based charge and energy decomposition scheme (ETS-NOCV) was applied to characterize the obtained polymers. © 2017 The Royal Society of Chemistry

Chelate ring stacking interactions in the supramolecular assemblies of Zn(ii)and Cd(ii) coordination compounds: a combined experimental and theoretical study

The self-assembly of Zn(ii) and Cd(ii) ions with two isomeric tetradentate ligands, 2-pyridyl-isonicotinoylhydrazone (HL1) and 2-benzoylpyridyl-picolinoylhydrazone (HL2), was studied by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction. The reaction of zinc(ii) and cadmium(ii) salts with HL1 and HL2 in methanol under solvothermal conditions produced six monomer and one tetranuclear zinc(ii) complexes, namely, Zn(HL1)Br2 (1), Zn(HL1)Cl2 (2), [Cd(HL1)2](NO3)2·H2O (3), Cd(HL2)Br2(4), Zn(HL2)Cl2 (5), Zn(HL2)Br2 (6) and [Zn4(L2)4I2][ZnI4]·2H2O (7). The structure of 7 includes a cationic tetranuclear cluster of four zinc ions, four ligands, and two anions, counterbalanced by ZnI4 2− ions. However, the reaction of zinc(ii) and cadmium(ii) salts with HL1 under the same conditions produced monomer compounds. Herein, the ligand effects on the complex structures were studied. Hirshfeld surface analysis and fingerprint plots facilitate the comparison of intermolecular interactions in compounds 1-7, which are crucial in building supramolecular architectures. © The Royal Society of Chemistry

Spodium bonds and metal–halogen···halogen–metal interactions in propagation of monomeric units to dimeric or polymeric architectures

In this work we report on crystal structures of a heteroleptic coordination polymer [Hg2(HL)Cl4]n (1) where the nitrogen atom of the peripheral pyridine fragment is linked to another HgCl2 molecule and two discrete mononuclear heteroleptic complexes [Hg(HL)I2] (2) and [Mn(HL)Cl2]·MeOH (3·MeOH), which were obtained through self-assembling of N'-(1-(pyridin-2-yl)ethylidene)isonicotinohydrazide (HL) with HgCl2, HgI2 or MnCl2, respectively. HL coordinates the HgII salts in its keto-form, while MnCl2 is chelated by a zwitterionic form of HL confirmed by the solid state IR spectroscopy. The studied here ligand molecule has a tendency to involve the 4-pyridyl nitrogen atom in coordination bonding which is correlated with the ability to transfer the electric charge and production of a zwitterionic form. The crystal structure and Hirshfeld surface data analysis show a great importance of spodium bonds and metal–halogen⋯halogen–metal interactions. A prominent consequence of lack of σ- or π-hole interactions in case of MnII ion is the isolation of metal center from the external contacts. Apart form this in 3·MeOH the halogen⋯halogen interactions are absent. It seems that the σ- or π-hole regions formed at the HgII cation in 1 and 2 favor the participation of coordinated Cl or I atoms in the M–Hal⋯Hal'–M' halogen⋯halogen interactions, whereas in complex 3·MeOH there are no metal or halogen centered σ-hole interactions. Thus, the 1D coordination polymer in 1 is stabilized by the Hg⋯Cl spodium bonding. Additionally, the observed intermolecular halogen⋯halogen interactions in 1 provide cross-linking of the 1D coordination polymers, yielding a 2D supramolecular double-layered sheet. In 2 an additional contact between halogen and mercury atoms results in a dimeric unit. These dimers are linked into a 1D polymer by halogen⋯halogen interactions between metal bounded iodine atoms. The DFT theoretical studies were applied to analyze the Hg⋯X non-covalent spodium interactions that govern the formation of the 1D polymeric structure in 1 and self-assembled dimers in 2. © 202

Polar protic solvent-trapping polymorphism of the HgII-hydrazone coordination polymer: Experimental and theoretical findings

A novel series of HgII coordination polymers with a general formula [HgL(N)3]n·n(solv) (HL = 2-pyridinecarbaldehyde isonicotinoylhydrazone; n(solv) = 0.5H2O (1), 2MeOH (2), EtOH (3), PrOH (4) and 0.5BuOH (5)) was prepared and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. The crystal structure of HL, elucidated by X-ray diffraction, comprises two independent molecules in the asymmetric unit cell, each of which is stabilized by an intramolecular hydrogen bond formed between the carbohydrazide hydrogen atom and the 2-pyridyl nitrogen atom. Crystal structures of 1-5 each reveal a similar 1D zigzag metal-organic chain [HgL(N)3]n, where the organic ligands bridge metal centers. These chains are extended into distinct 2D supramolecular nets by strong hydrogen bonds with the solvent molecules and/or short Hg⋯N supramolecular contacts. These networks were topologically classified as the hcb in 1 and fes in 2-5 underlying nets. On comparing the H-bonding patterns, it can be concluded that the lattice water molecules in 1 and methanol molecules in 2 form H-bonding interactions with the O and amide N atoms of L in the former structure and the O atom of L in the latter structure. In the remaining coordination compounds, the lattice solvent prefers the azide N atom for H-bonding. Furthermore, the existence of Hg⋯N interactions in 2-5 and their absence in 1 clearly highlights the importance of the size and polarity of the solvents on the self-assembly generation of HgII coordination polymers. A broad network of intermolecular π⋯π stacking interactions, formed between the pyridyl fragments, provide further reinforcement of crystal packing patterns in the structures of HL and 2-5. DFT based charge and energy decomposition scheme (ETS-NOCV) was applied to characterize the obtained polymers. © 2017 The Royal Society of Chemistry

Correction: Structural versatility of the quasi-aromatic Möbius type zinc(ii)-pseudohalide complexes-experimental and theoretical investigations (RSC Advances (2019) 9 (23764-23773) DOI: 10.1039/C9RA05276C)

The authors regret that the affiliations of Maria G. Babashkinah and Damir A. Sa?n were incorrectly shown in the original manuscript. The corrected list of affiliations is as shown herein. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. © The Royal Society of Chemistry 2019