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Four new asymmetric Schiff bases, N - α -methylsalicylidene- N ′-2-hydroxynapthylidene-1,3-propanediamine (H 2 L 1 ), N - α -methylsalicylidene- N ΄-5-bromosalicylidene-1,3-propanediamine (H 2 L 2 ), N - α -methylsalicylidene- N ΄-3-methoxysalicylidene-1,3-propanediamine (H 2 L 3 ) and N -(3-methoxysalicylidene)- N΄ -(2-hydroxynapthylidene)-1,3-propanediamine (H 2 L 4 ) and their Cu(II) complexes [CuL 1 ] ( 1 ), [CuL 2 ] ( 2 ), [CuL 3 ] ( 3 ) and [CuL 4 ] ( 4 ) have been synthesized. All the complexes ( 1 – 4 ) have been structurally characterized by single crystal XRD. The Cu-atom is four coordinated square planar in complexes 1 – 3 but in 4 a water molecule coordinates to one of its axial positions making it penta-coordinated with square pyramidal geometry. The mononuclear complex molecules of 1 and 2 form infinite 1D columns that are arranged parallel forming 2D sheets where as in 3 they form self-assembled dimers that are inter-connected by weak van der Waals interactions and in 4 the molecules are packed in the form of infinite 1D ladders. The structure of a recently reported complex with a similar asymmetric ligand (H 2 L 5 ) N - α -methylsalicylidene- N ′-salicylidene-1,3-propanediamine where the phenoxido oxygen coordinates mutually to the axial position of another molecule to form a dimer is compared to the present complexes. The packing of the molecules in all the crystals are rationalized by theoretical molecular electrostatic potential surface (MEPS) calculations. DFT calculations show the significant role of CH·π (chelate ring) and π⋯π (chelate ring) interactions governing the crystal packing in all the complexes. Both the interactions are evaluated energetically by means of high level DFT calculations (M06-2X/def2-TZVP) and characterized using Bader's theory. Energetic differences between the monomeric and dimeric complexes in 1 and 5 have also been evaluated. [ABSTRACT FROM AUTHOR]

Two new dinuclear cadmium(II) complexes, [Cd(L 1 ) 2 Cd(SeCN-κ-Se) 2 ] ( 1 ) and [Cd(L 2 ) 2 Cd(SeCN-κ-Se) 2 ] ( 2 ), where HL 1 = {2-(3-(dimethylamino)propyliminomethyl)-6-methoxyphenol} and HL 2 = {2-(3-(dimethylamino)propyliminomethyl)-6-ethoxyphenol}, have been prepared and characterized by elemental and spectral analysis and single crystal X-ray diffraction studies. Both complexes contain cadmium-selenium bonds. Non-covalent interactions were also investigated using DFT calculations at the BP86-D3/def2-TZVP level of theory. Both complexes show florescence upon irradiation with visible light. [ABSTRACT FROM AUTHOR]

Herein we report the synthesis and X-ray characterization of a neutral mercury(II) complex of composition [Hg(L) 2 ] n ( 1 ), [L = N 1 -(3-hydroxypropyl)-5-fluorouracilate]. The Hg(II) is bound to the N(3) atoms of both ligands in an essentially linear geometry. Mercury also interacts through short contacts with the O(4) atoms of the uracil rings. The two bases are almost coplanar. Surprisingly, two hydroxyl groups from two different units are also weakly bound in apical positions. Single-crystal X-ray crystallography showed that the molecular complex aggregates into a coordination polymer. The packing assemblies observed in the solid state have been analysed and studied by means of theoretical DFT calculations. Unprecedented antiparallel C O⋯C–F interactions are described since they have a strong influence in the crystal packing of the complex. We have also used the Cambridge Structural Database to examine the occurrence of C O⋯C–F interaction in the solid state of X-ray structures. [ABSTRACT FROM AUTHOR]

A new solvated complex of the uranyl ion, [UO 2 (quin) 2 (H’quin)]·DMF ( 1 ), (Hquin = 8-hydroxyquinoline and H’quin = quinolinium-8-olate, i.e. the zwitterionic form of H quin ) was synthesized and investigated by means of elemental analysis, IR spectroscopy and X-ray crystallography. Interestingly one coordinated 8-hydroxyquinoline is protonated, thus provoking the simultaneous existence of an electron rich and electron poor ring in the same molecule. This clearly enhances the ability of this ring to form antiparallel stacking interactions that are responsible for the solid state architecture of compound 1 . This aspect has been analyzed by means of density functional theory calculations (DFT), molecular electrostatic potential (MEP) tool and Bader’s theory of “atoms in molecules”. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A centrosymmetric copper(II) Schiff base complex has been Synthesized. • The Schiff base is trapped in its zwitterionic form. • Supramolecular interactions lead to the formation supra-molecular architecture. • Anion⋯anion interaction between the perchlorate anions have been analyzed. Abstract A centrosymmetric square planar bis-ligand copper(II) complex, [Cu(HL) 2 ](ClO 4) 2 , with a potential tetradentate Schiff base, HL = 2-(2-(ethylamino)ethyliminomethyl)-6-ethoxyphenol, containing pendant side arm, has been prepared and characterized by elemental and spectral analysis and single crystal X-ray diffraction studies. The potential tetradentate Schiff base is trapped in its zwitterionic form and shows a bidentate bonding mode. Several weak forces like hydrogen bonding and C H∙∙∙π interactions lead to the formation of supra-molecular architecture. The existence of an anion⋯anion interaction between the perchlorate anions have been analyzed using DFT calculations, the Bader's theory of atoms-in-molecules (AIM) and the non-covalent interaction index (NCI plot). The O⋯O distance is 2.848(2) Å. [ABSTRACT FROM AUTHOR]

Our synthetic approach demonstrates that pyridine-2,6-dicarboxylic acid N -oxide can form a stable Fe III complex with the rare 1:3 metal-to-ligand ratio. This study provides more information about packing features of one crystalline compound, (H9a-acr) 3 [Fe(pydco) 3 ]·6H 2 O ( 1 ) (where H 2 pydco = pyridine-2,6-dicarboxylic acid N -oxide and 9a-acr = 9-aminoacridine) via proton transfer methodology. The structure of 1 was characterized by IR spectroscopy, X-ray diffraction methods and the elemental analysis was performed to check the purity of the compound. On the basis of crystallographic data, compound 1 contains a monomeric anion with distorted octahedral geometry. The metal center is coordinated to six oxygen atoms by three bidentate pyridine-2,6-dicarboxylic acid N -oxide ligands to form a ceiling fan-shaped entity in which only the N -oxide oxygen and one carboxylate oxygen generate a six-membered chelate ring as seen for other N -oxides. Furthermore, the [Fe(pydco) 3 ] 3− and (9a-acr) + units in 1 form 2D anionic and cationic layers. The intermolecular interactions in this novel system consist of electrostatic attraction between ion pairs, different kinds of H-bonding and π-stacking all of which join the 2D layers to create 3D supramolecular architectures. Since pyridine-2,6-dicarboxylic acid N -oxide and pyridine-2,6-dicarboxylic acid have similar frameworks, we also highlighted some areas of current interest in the coordination behavior of the latter ligand in mononuclear monomeric compounds in the reported structures up to now and investigated the influence of the N -oxide moiety on the coordination mode(s) in the crystal lattice as well. [ABSTRACT FROM AUTHOR]

As part of ongoing studies of the effects of O - donor ligands based on pyridine-2,6-dicarboxylic acid N-oxide on the geometry, topology and dimensionality of their metal complexes, the salt (H9a-acr) 2 (pydco)·2H 2 O ( 1 ) and two new coordination complexes with formulas, {(H9a-acr) 2 [Cu(pydco) 2 (H 2 O) 2 ]·4H 2 O} ( 2 ), and {(H9a-acr) 2 [Ni(pydco) 2 (H 2 O) 2 ]·4H 2 O} ( 3 ) (where H 2 pydco = pyridine-2,6-dicarboxylic acid N-oxide and 9a-acr = 9-aminoacridine) have been synthesized by proton transfer from H 2 pydco to 9a-acr. The structures of 1 – 3 were characterized by elemental analysis, infrared spectroscopy and X-ray diffraction methods. Thermogravimetric analysis (TGA) was also carried out on compounds 1 and 2 . All three compounds have similar crystal packing, features, namely alternating 2D cationic and anionic layers which are held together by an extensive network of hydrogen bonds and π-stacking interactions to create three-dimensional supramolecular architectures. Despite the different conditions of temperature and stoichiometric ratio in the synthesis of complexes 2 and 3 , the products are isostructural and Cu 2+ and Ni 2+ have distorted octahedral geometry with two (pydco) 2− ions coordinated as chelating bidentate ligands. In all three compounds, protonated 9-aminoacridiunium cations are arranged in an anti-parallel stacking mode. This behavior is described and analyzed via density functional theory (DFT) calculations, molecular electrostatic potential (MEP) tools and the NCI method. [ABSTRACT FROM AUTHOR]

Three new manganese(II) complexes, namely [Mn(NCS) 2 (L) 2 (CH 3 OH) 2 ]·2CH 3 OH ( 1 ), [Mn(NCS) 2 (L) 2 (C 2 H 5 OH) 2 ]·2C 2 H 5 OH ( 2 ) and [Mn(NCS) 2 (μ-L) 2 ] n ( 3 ) (L = 4-acetylpyridine nicotinoylhydrazone) have been synthesized and characterized by elemental analysis, IR spectra, single-crystal and powder X-ray diffraction analysis. In order to investigate the effect of solvent, methanol, ethanol and acetonitrile have been used in the synthesis of complexes 1 – 3 , respectively. When using methanol as solvent, complex 1 was obtained. Complex 2 was synthesized under the similar synthetic conditions of complex 1 using ethanol instead of methanol as a solvent. To further examine the effect of solvent on the structure, we used CH 3 CN as a solvent instead of the ethanol. Unlike the complexes 1 and 2 , complex 3 was formed with 1D chain structure. The energetic features of the noncovalent interactions observed in the solid state of compounds 1 and 2 have been studied by means of DFT calculations. [ABSTRACT FROM AUTHOR]

Nickel(II), cobalt(II) and zinc(II) mononuclear Schiff base complexes of general formula [M II L(H 2 O) 3 ]·2H 2 O (where M = Ni, Co and Zn) have been synthesized using a new Schiff base ligand (LH 2 = 2-((Pyridin-2-yl)methyleneamino)benzene-1,4-dioic acid). All the complexes and the ligand have been characterized by various physical measurements such as elemental analyses, FT-IR and UV–Vis spectroscopic techniques. The crystal structure analyses of the complexes revealed that extensive supramolecular interactions such as hydrogen bond and π – π stacking results 3D array of packing. The hydrogen bonding interaction distances are very similar in all complexes and are around 2.0 Å and for the π – π interactions the values are close to 3.8 Å. The interaction energies are comparable for Ni and Co complexes and is somewhat stronger for Zn complex. The strength of the aforementioned interactions have been evaluated by means of DFT calculations. For in vitro antimicrobial activity study, the complexes were screened against some bacteria and fungi. This study shows that the zone of inhibition against growth of microorganisms is much larger for Zn complex due to strong binding energy. The Hirshfeld surfaces of Ni, Co and Zn complexes were also analyzed to clarify the nature of the intermolecular interactions. Thermogravimetric analyses were performed to investigate the thermal stability of the complexes. [ABSTRACT FROM AUTHOR]