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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]

In this manuscript, we have examined the CSD (Cambridge Structural Database) to investigate the relative ability of Te and I (in practice, the heaviest chalcogen and halogen atoms) in di- and tri-iododiorganyltellurium(IV) derivatives to establish σ-hole interactions. The geometry around the Te(IV) in this type of compound is trigonal bipyramidal where the stereoactive lone pair at Te(IV) occupies one of the equatorial positions. In the solid state, Te(IV) tends to form pseudo-octahedral coordination by establishing strong noncovalent interactions opposite to the two covalent bonds of the equatorial plane. Such contacts can also be classified as chalcogen bonds following the recommendation of the International Union of Pure and Applied Chemistry (IUPAC). Such contacts have been analyzed energetically in this work using density functional theory (DFT) calculations, rationalized using molecular electrostatic potential (MEP) surface analysis and characterized using a combination of the quantum theory of atoms in molecules (QTAIM) and noncovalent interaction plot (NCIplot) computational tools. Finally, the observation of halogen bonds and type I halogen···halogen contacts is also emphasized and compared to the chalcogen bonds. Energy decomposition analysis has also been performed to compare the physical nature of chalcogen, halogen and type I interactions. [ABSTRACT FROM AUTHOR]

In this manuscript we consider from a theoretical point of view the recently reported experimental quantification of anion-p interactions (the attractive force between electron deficient aromatic rings and anions) in solution using aryl extended calix[4]pyrrole receptors as model systems. Experimentally, two series of calix[4]pyrrole receptors functionalized, respectively, with two and four aryl rings at the meso positions, were used to assess the strength of chloride-π interactions in acetonitrile solution. As a result of these studies the contribution of each individual chloride-π interaction was quantified to be very small (<1 kcal/mol). This result is in contrast with the values derived from most theoretical calculations. Herein we report a theoretical study using high-level density functional theory (DFT) calculations that provides a plausible explanation for the observed disagreement between theory and experiment. The study reveals the existence of molecular interactions between solvent molecules and the aromatic walls of the receptors that strongly modulate the chloride-π interaction. In addition, the obtained theoretical results also suggest that the chloride-calix[4]pyrrole complex used as reference to dissect experimentally the contribution of the chloride-π interactions to the total binding energy for both the two and four-wall aryl-extended calix[4]pyrrole model systems is probably not ideal. [ABSTRACT FROM AUTHOR]

It has been proposed that late transition metals with low coordination numbers (square planar or linear) can act as nucleophiles and participate in σ-hole interactions as electron donors. This is due to the existence, in this type of metal complexes, of a pair of electrons located at high energy d-orbitals (dz2 or dx2-y2), which are adequate for interacting with antibonding σ-orbitals [σ*(X–Y)] where Y is usually an electron withdrawing element and X an element of the p-block. This type of d[M]→σ*(X–Y) interaction has been reported for metals of groups 9–11 in oxidation states +1 and +2 (d8 and d10) as electron donors and σ-holes located in halogen and chalcogen atoms as electron acceptors. To our knowledge, it has not been described for σ-holes located in pnictogen atoms. In this manuscript, evidence for the existence of pnictogen bonding involving the square planar Pt(II) metal as the electron donor and Sb as the electron acceptor is provided by using an X-ray structure retrieved from the Cambridge Structural Database (CSD) and theoretical calculations. In particular, the quantum theory of atoms in molecules (QTAIM), the noncovalent interaction plot (NCIPlot) and molecular electrostatic potential (MEP) methods were used. Moreover, to further confirm the nature of the Sb···Pt(II) contact, a recently developed method was used where the electron density (ED) and electrostatic potential (ESP) distribution were compared along the Sb···Pt(II) bond path. [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]

The chalcogen bond has been recently defined by the IUPAC as the attractive noncovalent interaction between any element of group 16 acting as an electrophile and any atom (or group of atoms) acting as a nucleophile. Commonly used chalcogen bond donor molecules are divalent selenium and tellurium derivatives that exhibit two σ-holes. In fact, the presence of two σ-hole confers to the chalcogen bonding additional possibilities with respect to the halogen bond, the most abundant σ-hole interaction. In this manuscript, we demonstrate that selenoxides are good candidates to be used as σ-hole donor molecules. Such molecules have not been analyzed before as chalcogen bond donors, as far as our knowledge extends. The σ-hole opposite to the Se=O bond is adequate for establishing strong and directional ChBs, as demonstrated herein using the Cambridge structural database (CSD) and density functional theory (DFT) calculations. Moreover, the effect of the metal coordination of the selenoxide to transition metals on the strength of the ChB interaction has been analyzed theoretically. The existence of the ChBs has been further supported by the quantum theory of atoms in molecules (QTAIM) and the noncovalent interaction plot (NCIPlot). [ABSTRACT FROM AUTHOR]

In this study, Fe3O4 nanoparticles (FeNPs) decorated with halogenated perylene diimides (PDIs) have been used for capturing VOCs (volatile organic compounds) through noncovalent binding. Concretely, we have used tetrachlorinated/brominated PDIs as well as a nonhalogenated PDI as a reference system. On the other hand, methanol, ethanol, propanol, and butanol were used as VOCs. Experimental studies along with theoretical calculations (the BP86-D3/def2-TZVPP level of theory) pointed to two possible and likely competitive binding modes (lone pair–π through the π-acidic surface of the PDI and a halogen bond via the σ-holes at the Cl/Br atoms). More in detail, thermal desorption (TD) experiments showed an increase in the VOC retention capacity upon increasing the length of the alkyl chain, suggesting a preference for the interaction with the PDI aromatic surface. In addition, the tetrachlorinated derivative showed larger VOC retention times compared to the tetrabrominated analog. These results were complemented by several state-of-the-art computational tools, such as the electrostatic surface potential analysis, the Quantum Theory of Atoms in Molecules (QTAIM), as well as the noncovalent interaction plot (NCIplot) visual index, which were helpful to rationalize the role of each interaction in the VOC···PDI recognition phenomena. [ABSTRACT FROM AUTHOR]

In this manuscript, we combined DFT calculations (PBE0-D3/def2-TZVP level of theory) and a Cambridge Structural Database (CSD) survey to evaluate the ability of perchlorinated cyclopenta- and cyclohexatetrelanes in establishing tetrel bonding interactions. For this purpose, we used Tr5Cl10 and Tr6Cl12 (Tr = Si and Ge) and HCN, HF, OH− and Cl− as electron donor entities. Furthermore, we performed an Atoms in Molecules (AIM) analysis to further describe and characterize the interactions studied herein. A survey of crystal structures in the CSD reveals that close contacts between Si and lone-pair-possessing atoms are quite common and oriented along the extension of the covalent bond formed by the silicon with the halogen atom. [ABSTRACT FROM AUTHOR]

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]

Abstract: Noncovalent carbon bonding, a recently explored σ‐hole interaction, was hitherto supposed to be a weak and structure‐guided interaction. Here, its role in the intramolecular stabilization of the cis conformation of the amide moiety in acylhydrazones is described. The calculations reveal an electron donation from the lone pair of the nitrogen atom to the empty antibonding C−N orbital [LP(N)→BD*(C−N)] with a concomitant stabilization energy of E(2)=1.2 kcal mol−1. [ABSTRACT FROM AUTHOR]

Two new Co(II) and Cu(II) coordination polymers, {Co(HL1)2(μ-L2)(H2O)2}n (1) and {[Cu(HL1)2(μ-L2)H2O]·H2O}n (2) (H2L1 = Phthalic acid and L2 = 2-aminopyrazine), have been synthesized by slow evaporation of solvent and characterized by IR spectroscopic, elemental, single-crystal X-ray diffraction and thermal analysis. X-ray results indicate that in both the polymers, phthalate acts as a monodentate ligand and the aminopyrazine ligand is responsible for the formation of the infinite one-dimensional chain structure. The solid-state structures are stabilized through hydrogen bonds and N-H···π interactions by generating two-dimensional layered structures. Finally, the non-covalent interactions have been studied energetically and using Bader's theory of atoms in molecules by means of Density Functional Theory (DFT) calculations. The influence of the metal coordination on the strength of the interaction has been studied using molecular electrostatic potential surface calculations. [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]

A new inorganic–organic hybrid based on an aspartate functionalized polyoxomolybdate, [pentaaquacobalt(II)]‐μ‐aspartate‐[γ‐octamolybdate]‐μ‐aspartate‐[pentaaquacobalt(II)] tetrahydrate, [Co2(C4H6NO4)2(γ‐Mo8O26)(H2O)10]·4H2O (1), has been synthesized under hydrothermal conditions from the reaction of an Evans–Showell‐type polyoxometalate, (NH4)6[Co2Mo10H4O38], and l‐aspartic acid. The complex exhibits a supramolecular three‐dimensional framework structure in the crystal lattice. Compound 1 was structurally characterized by elemental analyses, IR and UV–Vis (diffuse reflectance) spectroscopy and single‐crystal X‐ray diffraction. In this compound, aspartic acid acts as a bridge between the two Co atoms and the Mo centres, with the –CH2COOH side chain directly linked to the Mo centre in γ‐[Mo8O26]4− and the α‐carboxylate side chain bound to the Co centre. Commonly, the binding of transition‐metal complexes to POMs involves coordination of the metal to a terminal O atom of the POM so that 1, with a bridging ligand between Mo and Co atoms, belongs to a separate class of hybrid materials. While the starting materials are both chiral and one might expect them to form a chiral hybrid, the decomposition of the chiral Evans–Showell‐type POM and its conversion to the centrosymmetric γ‐octamolybdate POM, plus the presence of two aspartate ligands centrosymmetrically placed on either side of the POM, leads to the formation of an achiral hybrid. We have studied energetically by means of density functional theory (DFT) calculations and using the Bader's 'atoms‐in‐molecules' analysis the electrostatically enhanced hydrogen bonds (EEHBs) observed in the solid state of 1, which are crucial for the formation of one‐dimensional supramolecular assemblies. We have studied energetically the electrostatically enhanced hydrogen bonds (EEHBs) observed in the solid‐state structure of [Co(AA)(H2O)5]2γ‐[Mo8O26] (where AA is aspartic acid) by means of DFT calculations and AIM analysis. These bonds are very strong due to the ionic nature of both the hydrogen‐bond donor and acceptor. [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]

As an extension of our continued interest in the preparation of inorganic-organic hybrids, we report the successful hydrothermal synthesis of sodium tris[triaqua(μ-1,10-phenanthroline-2,9-dicarboxylato)dysprosium(III)] silicododecatungstate dodecahydrate, {[DyNa(C14H6N2O4)3(H2O)9(SiW12O40)]·12H2O}n or Na[Dy(PDA)(H2O)3]3[SiW12O40]·12H2O (1), and sodium aqua tris[tetraaqua( μ-4-hydroxypyridine-2,6-dicarboxylato)praseodymium(III)] silicododecatungstate dodecahydrate, {[NaPr(C7H3NO5)3(H2O)13(SiW12O40)]·12H2O}n or Na(H2O)[Pr(pydc-OH)(H2O)4]3[SiW12O40]·12H2O (2) (in which H2PDA is 1,10-phenanthroline-2,9-dicarboxylic acid and H2pydc-OH is 4-hydroxypyridine-2,6-dicarboxylic acid or chelidamic acid). Both compounds have been characterized using elemental analysis, IR spectroscopy and X-ray diffraction methods. Structural characterization by single-crystal X-ray diffraction reveals that these compounds consist of [SiW12O40]4- Keggin-type polyoxometalates (POMs), where a single {W3O13} triad is decorated with a trinuclear Ln complex. Moreover, the decorated polyanions are involved in a series of intermolecular interactions, such as hydrogen bonds and anion-л interactions, resulting in three-dimensional supramolecular architectures. Density functional theory (DFT) studies were conducted to support these intermolecular interactions in both 1 and 2, and have been rationalized using molecular electrostatic potential (MEP) surface calculations. [ABSTRACT FROM AUTHOR]

A Cu(II)-methylmalonate complex, (C3H7N6)4[Cu(II)(C4H4O4)2](H2O)4Cl2(1) (where C3H7N6 = protonated melamine, C4H4O4 = methylmalonic acid), has been synthesized from aqueous media and its crystal structure was determined by single-crystal X-ray diffraction. The anionic Cu(II)-methylmalonate complex mediated formation of interesting supramolecular assemblies in the solid state by means of ionic interactions with protonated melamine. Moreover, other forces such as antielectrostatic H-bonding andπ+–π+interactions also play a crucial role in defining the final 3-D architecture of1. An interesting stacking among protonated melamine molecules is studied by DFT calculations. Lattice water molecules and chlorides form various hydrogen bonds to take part in the self-assembly processes. [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]

Two new dinuclear zinc(II) complexes, [Zn2(µ1,3-OAc)(L1)2]I·MeOH (1) and [Zn2(µ1,3-OAc)(L2)(NCS)] (2), (where HL1 = 2-(((3-(dimethylamino)propyl)amino)methyl)-6-methoxy-phenol and H2L2 = 2,2′-[(1-Methyl-1,2-ethanediyl)bis(iminomethylene)]bis[6-ethoxyphenol]) have been synthesized and characterized by elemental and spectral analysis. Their X-ray solid state structures have been determined, revealing the existence of intramolecular Zn···O spodium bonds in both complexes due to the presence of methoxy (1) or ethoxy (2) substituents adjacent to the coordinated phenolic O-atom. These noncovalent interactions have been studied using density functional theory (DFT) calculations, the quantum theory of "atoms-in-molecules" and the noncovalent interaction plot. Moreover, a search in the Cambridge structure database (CSD) has been conducted in order to investigate the prevalence of intramolecular spodium bonds in Zn complexes. To our knowledge this is the first investigation dealing with intramolecular spodium bonds. [ABSTRACT FROM AUTHOR]