A mononuclear cobalt(II) salophen-type complex: Synthesis, theoretical and experimental electronic absorption and infrared spectra, crystal structure, and predicting of second- and third-order nonlinear optical properties.

A tetradentate Schiff base ligand, (4-nitro-N,N'-o-phenylene-bis(5-methoxysalicylideneimine)) (H2L), and its cobalt(II) complex (CoL•DMF) were synthesized. Elemental analysis, and FT-IR and 1H NMR spectra were used to confirm the molecular structure of H2L ligand. In addition, elemental analysis, molar conductance measurement, infrared and electronic absorption spectroscopies as well as single crystal X-ray diffraction were employed to distinguish the molecular structure of the complex that has a slightly distorted square-planar geometry around the cobalt(II) ion. The geometries of H2L and CoL were optimized by means of the DFT/(U)PBE0/Def2-TZVP level of theory. Good agreement of the optimized geometric parameters of the complex with the corresponding experimental ones and successfully reproduction of the FT-IR spectra of the ligand and complex validated the applied method. Based on the optimized structure of CoL, its electronic absorption spectrum was reproduced by using time-dependent density functional theory (TDDFT) at the same level. Its analysis was carried out to assign the observed electronic transitions and determine their characters. The computed nonlinear optical (NLO) parameters (ß, γ and < γ > values) of H2L and CoL by using TDDFT at the same level combined with the sum-over-states (SOS) method are considerable larger values than reference compound i.e. urea. The ligand and the complex in the absence of nitro and methoxy moieties referred to as H2L' and CoL' respectively were optimized to elucidate the effect of these moieties on hyperpolarizabilities values.

The [4†+†4] thermocyclization of 9-anthraldehyde: synthesis, crystal structure, experimental and theoretical UV spectra, natural bonding orbital analysis and prediction of third-order nonlinear optical properties.

The dimer of 9-anthraldehyde, namely heptacyclo[8.6.6.62,9.03,8.011,16.017,22.023,28]octacosa-3,5,7,11,13,15,17(22),18,20,23(28),24,26-dodecaene-1,9-carbaldehyde, C30H20O2, has been synthesized by refluxing an ethanol solution in the presence of M(ClO4)2 and 1,3-diaminopropan-2-ol (M = Co2+ or Cu2+). Its structure has been determined by single-crystal X-ray diffraction, showing it to be a new polymorph, referred to as polymorph II, in the monoclinic space group P21/n. It is compared with the previously reported triclinic modification [Ehrenberg (1968). Acta Cryst. B24, 1123-1125], which is referred to as polymorph I. The asymmetric unit of polymorph II contains two half molecules located on crystallographic centres, while the asymmetric unit of polymorph I includes one half molecule, also located on a crystallographic centre. Time-dependent density functional theory (TD-DFT) at the RB3LYP level using the 6-31G(d,p) basis set was applied. The predicted electronic absorption spectrum is in good agreement with the experimental one. The analysis of the calculated electronic absorption spectrum of polymorph II was carried out in order to assign the observed electronic transitions and to determine their character. A natural bonding orbital (NBO) analysis was executed at the same level to evaluate charge-transfer, intramolecular hydrogen-bonding interactions and hyperconjugative interactions. The third-order nonlinear optical (NLO) properties of the compound were appraised by the ZINDO/sum-over-states method in both static and dynamic states. The orientationally averaged (isotropic) value of γ for the compound is greater than the corresponding value of 4-nitroaniline (pNA).

2,2'-[(Disulfanediyl)bis{5-[(1E)-(2-hydroxybenzylidene)amino]-1,3-thiazole-4,2-diyl}]diphenol: synthesis, crystal structure and calculation of molecular hyperpolarizability.

The title Schiff base compound {systematic name: 2-[5-[(E)-(2-hydroxybenzylidene)amino]-4-(2-{5-[(E)-(2-hydroxybenzylidene)amino]-2-(2-hydroxyphenyl)-1,3-thiazol-4-yl}disulfanyl)-1,3-thiazol-2-yl]phenol}, C32H22N4O4S4, incorporating a disulfanediyl (dithio) linkage, was obtained from the condensation reaction between two equivalents of salicylaldehyde and one equivalent of dithiooxamide in dimethylformamide, and was characterized by elemental analysis, IR spectroscopic analysis and single-crystal X-ray diffraction. A one-dimensional chain is formed along the b axis via double intermolecular C-H...S hydrogen bonds. The HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energies and some related molecular parameters were calculated at the B3LYP/6-311G(d,p) level of theory. The molecular hyperpolarizability was also calculated.

The role of structural C--H compared with phenolic OH sites on the antioxidant activity of oleuropein and its derivatives as a great non-flavonoid family of the olive components: a DFT study.

Oleuropein and its derivatives are the main phenolic compounds of Olea europaea L. leaf and fruit. The structure-antioxidant activity relationship was considered for studying the radical scavenging activity of this non-flavonoid family of the olive components using density functional theory (DFT). The structure of these compounds were optimized employing the B3LYP/6-31G (d,p) and the role of some structural CH positions was compared with phenolic OH sites on radical scavenging. As a result, a radical unique position (C3) in the oleuropein, characterized by low BDE (Bond Dissociation Enthalpy), reasonable spin density and electron distribution, was identified. The experimental results of the previous publications of oleuropein for NO and OH scavenging confirmed the presence of this unique active site in its molecular structure. According to the results, 2,2-diphenylpicrylhydrazyl (DPPH) cannot find this non-marginal active site. Therefore, DPPH may not be a determinant assay for all antioxidant comparisons. Solvent effects were considered in all calculations using a Polarized Continuum Model (PCM) at the B3LYP/6-31G (d,p) level. Solvation calculations were carried out for benzene (ε=2.3) to simulate the oil environment compared to gas phase.

A one-pot catalyst-free synthesis of functionalized pyrrolo[1,2-a]quinoxaline derivatives from benzene-1,2-diamine, acetylenedicarboxylates and ethyl bromopyruvate.

The catalyst-free multicomponent reaction of 1,2-diaminobenzene, dialkyl acetylenedicarboxylates, and ethyl bromopyruvate forms pyrrolo[1,2-a]quinoxaline derivatives in good yields. Ethylenediamine also reacts under similar conditions to produce new pyrrolo[1,2-a]pyrazine derivatives.

PEG-mediated catalyst-free expeditious synthesis of polysubstituted anilines and benzenes via the reaction of malononitrile and ß-ketoester derivatives in the presence of activated acetylenes.

Poly(ethylene glycol) (PEG) has been used as a sustainable, non-volatile, and environmentally friendly reaction solvent for synthesis of functionalized anilines and benzenes via the reaction of malononitrile and ß-ketoester derivatives in the presence of activated acetylenes at 80° C. No additional solvent and catalyst are required.