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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 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]

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]