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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]

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]

Abstract: We report the synthesis and X-ray characterization of N1-hexylcytosine (1) and N1-hexylcytosinium nitrate (2). N1-hexylcytosine (1) does not follow the same behaviour previously described for N1-hexylthymine and N1-hexyluracil in the solid state. This different behavior has been analyzed by means of density functional theory (DFT) calculations including the latest available correction for dispersion (D3). In addition hydrophobic and anion–π noncovalent interactions play a key role in stabilizing the 3D architectures of the compounds, which have been energetically studied using theoretical calculations and compared with similar structures retrieved from the Cambridge Structural Database (CSD). The anion–π–anion binding mode observed for nitrate in compound 2 is also observed in several crystal structures involving cytosine ring coordinated to transition metals. [Copyright &y& Elsevier]

Graphical abstract DFT study have been employed to explore the contribution of conventional π⋯π and unconventional π(arene)–π(chelate ring) interactions in two copper(II) complexes with a naphthalene-based Schiff base. Abstract A N,N,O donor Schiff base blocking ligand, [ HL = (1-(2-(morpholinoethylimino)methyl)naphthalen-2-ol) ] has been used to synthesize one end-to-end thiocyanate bridged dinuclear complex { [Cu 2 (L) 2 (μ 1,3 -NCS) 2 ] ( 1 ) } and one end-to-end dicyanamide (dca) bridged polynuclear complex {[Cu(L)(μ 1,5 -dca)] n ( 2 )}. Both complexes have been characterized by elemental and spectral analysis. Their structures have been confirmed by single crystal X-ray diffraction studies. Copper(II) center in each complex is coordinated in an elongated square pyramidal fashion. Complex 1 is a centrosymmetric dimer, whereas complex 2 forms a one dimensional coordination polymer bridged by end-to-end dca bridges. The presence of an extended π-system (naphthalene-based ligand) facilitates the formation of C H∙∙∙π and π⋯π non-covalent interactions. DFT calculations have been performed to explore the contribution of conventional π⋯π and unconventional π(arene)–π(chelate ring) interactions using several computational tools. [ABSTRACT FROM AUTHOR]

The present report describes the synthesis and structural characterizations of six new manganese(III) complexes with redox-active tetrachlorocatecholate ligand in the presence of different ancillary ligands (pyridines and imidazole). X-ray crystal structure analysis reveals that the geometry of manganese(III) centres in 1 and 2 is essentially square pyramidal, while it is discrete octahedron in compounds 3 – 6 . These preferential structural diversities in these systems have been critically analysed by theoretical calculations. Remarkably, the characterization of both π ⋯ π stacking interactions and Mn Mn bonds in the supramolecular dimeric aggregates in the solid state in 1 and 2 by means of the Bader's theory of “atoms in molecules” (AIM) is quite interesting as that nicely corroborates the experimental fact. All the complexes are active toward the phenoxazinone synthase like activity and the detailed kinetic analysis was performed to get better insight into their catalytic efficiency. Electrochemical property of these complexes as well as different donor property of the ancillary ligands clearly establish that the ease of reduction of the metal centre i.e., the catalytic ability is favoured when the metal centre is bonded to the electron deficient pyridyl systems. EPR spectroscopy and theoretical study are further helpful to get insight into origin of the catalytic activity in these compounds. The present report overall highlights that tuning of the geometry and catalytic activity of manganese(III) complexes with tetrachlorocatecholate ligand can be attained by the introduction of different substitutions in ancillary pyridine ligands. [ABSTRACT FROM AUTHOR]

This study reports the synthesis of a new catenane Gd(III) complex using pyridine-2,6-dicarboxylic acid (H 2 pydc) as ligand. The structure of [Gd(pydc)(Hpydc)(H 2 O) 2 ] n ( 1 ) was characterized by IR spectroscopy, X-ray diffraction methods and the elemental analysis to check the purity of the compound. On the basis of crystallographic data, compound 1 contains a Gd(III) metal center that is coordinated to seven oxygen atoms of two tridentate and one monodentate H 2 pydc ligands and two coordinated water molecules. Other lanthanoid complexes involving this ligand are available in the literature; however, this is the first example where a combination of monoanionic (Hpydc − ) and dianionic (pydc 2 − ) forms of the ligand counterbalance the Gd 3 + metal center. The intermolecular interactions in this novel system consist of different kinds of H-bonding and π-stacking interactions in addition to antiparallel CO ⋯ CO interactions which have been analyzed using DFT calculations and the Bader's theory of “atoms in molecules”. [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]

The direct reaction between p -chlorobenzoic acid and metal nitrate salts resulted in the formation of a novel heterometallic μ 3 -oxo trinuclear cluster with the formula [Cr III 2 Mn II O(C 7 H 4 O 2 Cl) 6 (Py) 3 ]C 7 H 5 O 2 Cl ( 1 ), which has been characterized by elemental analysis, electronic and IR spectra, and single-crystal X-ray crystallography. The electronic spectrum of the complex exhibited two spin-allowed bands for Cr III in the regions 17 900 and 22 750 cm −1 , which could be assigned to the transitions from 4 A 2 g (F) to 4 T 2 g (F) and 4 T 1 g (F) , respectively. We have also examined the Cambridge Structural Database to investigate the abundance of this type of complex in terms of the trivalent/divalent metal ions and the hetero/homometallic nature of the trinuclear cluster. We have studied the relative stability of the different cluster situations, calculating the energetic costs of a series of metal substitution reactions by means of high level DFT calculations. Moreover, we have analyzed the effect of the p -chlorine substituent in benzoic acid, since the formation of halogen bonding interactions in the solid state are important in determining the crystal packing of 1. [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]

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]

Abstract: Potentially hexadentate N2O4 donor Schiff base ligands N,N′-bis(3-ethoxysalicylidenimino)-1,2-diaminoethane (L1H2) and N,N′-bis(3-methoxysalicylidenimino)-1,3-diaminopropane (L2H2) have been used to synthesize two manganese(III) compounds [MnL1(SCN)(H2O)].[MnL1(H2O)2](ClO4)·CH3CN (1) and [MnL2(SCN)(H2O)] (2). All the ligands and the complexes have been characterized by microanalytical and spectroscopic techniques. The X-ray structural characterization of all the complexes shows a tetragonally elongated octahedral geometry for the manganese coordination sphere. The octahedron entities are further connected in pairs through intermolecular hydrogen bonding to form μ-aquo dimers, which are further stabilized by π–π interactions occurring between the aryl rings of the Schiff base ligands. These noncovalent interactions have been investigated in terms of energies and geometries using theoretical calculations. The catalytic activity of compounds 1 and 2 on the oxidation of 3,5-di-tert-butylcatechol was determined spectrophotometrically by monitoring the increase of the 3,5-di-tert-butyl-o-benzoquinone characteristic absorption band at about 400nm over time in methanol saturated with O2. The complexes were able to oxidize 3,5-di-tert-butylcatechol to the corresponding o-quinone with distinct catalytic activity. [Copyright &y& Elsevier]