Awatef Ayadi

Tetrathiafulvalene-based azine ligands for anion and metal cation coordination.

Summary The synthesis and full characterization of two tetrathiafulvalene-appended azine ligands, namely 2-([2,2’-bi(1,3-dithiolylidene)]-4-yl)-6-((2,4-dinitrophenyl)hydrazono)methyl)pyridine (L1) and 5-([2,2’-bi(1,3-dithiolylidene)]-4-yl)-2-((2,4-dinitrophenyl)hydrazono)methyl)pyridine (L2) are described. The crystal structure of ligand L1 indicates that the ligand is completely planar with the presence of a strong intramolecular N3–H3···O1 hydrogen bonding. Titration experiments with inorganic anions showed that both ligands are suitable candidates for the sensing of fluoride anions. Ligand L2 was reacted with a Re(I) cation to yield the corresponding rhenium tricarbonyl complex 3. In the crystal structure of the newly prepared electroactive rhenium complex the TTF is neutral and the rhenium cation is hexacoordinated. The electrochemical behavior of the three compounds indicates that they are promising for the construction of crystalline radical cation salts.

All-Optical Switching and Two-States Light-Controlled Coherent-Incoherent Random Lasing in a Thiophene-Based Donor-Acceptor System

We describe herein the synthesis and characterization of a thiophene-based donor-acceptor system, namely (E)-2-(4-nitrostyryl)-5-phenylthiophene (Th-pNO2 ), which was prepared under Horner-Wadsworth-Emmons conditions. The UV/Vis absorption bands, including the intramolecular charge transfer (ICT) band, were fully assigned using DFT and TD-DFT computations. The results of both efficient third-order nonlinear optical properties and light-amplification phenomena are presented. Investigations of photoinduced birefringence (PIB) in optical Kerr effect (OKE) experiments showed a great potential for this particular compound as an efficient, fully reversible, and fast optical switch. Time constants for the observed trans-cis-trans molecular transitions are in the range of microseconds and give a competitive experimental result for the well-known and exploited azobenzene derivatives. Random lasing (RL) investigations confirmed that this organic system is potentially useful to achieve strong light enhancement, observed as a multimode lasing action. Both RL and OKE measurements indicate that this material is a representative of thiophene derivatives, which can be utilized to fabricate fast all-optical switches or random lasers (light amplifiers).

Effect of UV irradiation on nonlinear optical response of azo-based iminopyridine rhenium complexes

The nonlinear optical properties of conjugated rhenium containing azo-based iminopyridine complexes were studied by means of Maker fringe technique using 30 ps laser pulses at 1064 nm. The influence of UV irradiation of guest-host films on nonlinear optical response was investigated. The values of second and third order susceptibility before and after UV irradiation were extracted and analyzed. The nonlinear optical response of the rhenium containing complex which contain lateral dimethylamino group and forms a D-A π-conjugated structure was found to be more sensitive to UV treatment.

Nonlinear optical properties of some selected highly conjugated molecules based on TTF for optoelectronics applications

The derivatives based on tetrathiafulvalene (TTF) are among the molecules which are characterized by their high nonlinear optical properties and are electro-actives molecules. When the TTF molecules and their derivatives are bonded to electron acceptors in order to forming D -A system, the intermolecular charge transfer (ICT) can be induced under light excitation, because tetrathiafulvalene are known by their strong charge transfer as a strong electron donor and have been widely used in preparations of molecular materials with various applications in optoelectronic and photonic devices. We study the nonlinear optical properties of two new conjugated ligands based on TTF, which differ by the position of the TTF unit on the pyridine ring. We investigate the nonlinear optical properties of our films deposited by PLD technique , by using the THG (third harmonic generation).The measurements have been performed by means of Maker fringe technique using the laser generating at 1064 nm with 30 ps pulse duration, which allow to extract the third order NLO parameters of TTF-based compounds.

Analyses of electronic and optical properties of TTF-based azine derivatives

Structural, electronic and optical properties of four organic molecules named L1, L2, L3 and L4 were studied theoretically using DFT methodology. The UV-vis absorption spectra were investigated also experimentally when the molecules were dissolved in dicholoromethane. The calculations prove that for chosen molecules better results are obtained applying the LC-BLYP methodology due to the extended charge distribution and polarity of the molecules. The molecules L3 and L4 are characterised by the relatively high dipole moment and the low HOMO-LUMO energy gap splitting. It allows to suppose that these molecules may be useful for the nonlinear optical (NLO) applications. The solvent effect on the optical properties of the molecules was checked. The calculations were performed using polarisable continuum model and the data were compared to the experimental results.

Pyrene bisiminopyridine ligand and its zinc complex

ABSTRACT The synthesis of a pyrene bisiminopyridine ligand L was successfully accomplished by condensation between 1-aminopyrene and 2,6-pyridinecarboxaldehyde. The complexation of L with zinc triflate afforded a neutral metal complex formulated as [Zn(H2O)LCF3SO3)2].2Et2O. In the complex, the ligand is coordinated to zinc(II) through its three nitrogen atoms which form a distorted octahedral environment together with three oxygen atoms, two from the triflate anions and one from aqua ligand. Both compounds have been characterized using NMR, elemental analysis, mass spectrometry, electronic absorption (UV-Vis) and infrared. Luminescence properties of these compounds show an emission maxima at 412 nm, indicating a pyrene monomer emission.

Third order nonlinear optical response of conjugated photoactive ligands

Generally, organic and organometallic materials containing π-conjugated chains are considered as promising candidates for nonlinear optical applications. In this work, we report on the third order nonlinear optical response of π-conjugated azo-conjugated azo-iminopyridine photoactive ligands containing electron donating or electron accepting fragments in their structure. The nonlinear optical investigation is performed by means of the Z-scan technique well as the Maker Fringes Third Harmonic Generation technique employing a 30 ps mode-locked Nd-YVO4 laser with a repetition rate of 10 Hz.

Effect of metal complexation on the nonlinear optical response in conjugated ligands

Organic nonlinear optical materials are widely investigated materials for fabricating optoelectronic devices. Particularly organic π-conjugated systems as well as transition metal complex compounds are studied in this direction because of the strong electronic coupling between the ligand and the metal, their excellent chemical stability, and their rich photochemical and photophysical properties. In this work, comparative studies of the third-order nonlinear optical susceptibilities of a bipyridine ligand (4-(N,N-dibutylamino)-4′-(5-ethynyl-2,2′-bipyridine)-azobenzene (A) and of the corresponding heteroleptic ruthenium complex (Ru(bpy)2(La)(PF6)2 (B) (La signifies the ligand) are presented. The NLO properties were investigated by means of the Z-scan technique using a 30 ps mode-locked Nd-YVO4 laser at 532 nm with a repetition rate of 10 Hz. Our results show that the introduction of the metal in the organic complex results in a significant modification of the third-order nonlinear optical response.