Giuseppe Consiglio

Supramolecular aggregation/deaggregation in amphiphilic dipolar Schiff-base zinc(II) complexes.

The synthesis, characterization, optical, and fluorescent properties of an amphiphilic Schiff-base bis(salicylaldiminato)zinc(II) complex are reported. Detailed (1)H nuclear magnetic resonance (NMR), diffusion-ordered spectroscopy (DOSY) NMR, optical absorption, and fluorescence spectroscopy studies indicate the existence of aggregate species in noncoordinating solvents. The degree and type of aggregation are related to the concentration and the polarity of the noncoordinating solvent. Dilute solutions are likely characterized by the presence of defined dimers, whereas larger oligomeric aggregates are conceivably formed at higher concentrations. The concentration needed to observe the formation of larger species depends upon solvent polarity. In coordinating solvents or in the presence of coordinating species, a complete deaggregation of the system occurs, because of the axial coordination to the Zn(II) ion, accompanied by considerable changes of (1)H NMR and optical absorption spectra. A dramatic enhancement of fluorescence emission is observed in dichloromethane solutions upon deaggregation with a coordinating agent. The formation of a defined 2:1 supramolecular structure is demonstrated in the case of a ditopic ligand as coordinating species. Overall, these complexes are promising systems for the development of new supramolecular architectures and supramolecular fluorescent probes.

Intramolecular Charge Transfer of Push–Pull Pyridinium Salts in the Singlet Manifold

The solvent effect on the photophysical and photochemical properties of the iodides of three trans (E) isomers of 2-D-vinyl,1-methylpyridinium, where D is a donor group (4-dimethylaminophenyl, 3,4,5-trimethoxyphenyl and 1-pyrenyl), was studied by stationary and transient absorption techniques. The results obtained allowed the negative solvatochromism and relaxation pathways of the excited states in the singlet manifold to be reasonably interpreted. Resorting to ultrafast absorption techniques and DFT calculations allowed information on the excited state dynamics and the role of the solvent-controlled intramolecular charge transfer (ICT) processes to be obtained. The structure-dependent excited state dynamics in nonpolar solvents, where the ICT is slower than solvent rearrangement, and in polar solvents, where an opposite situation is operative, was thus explained. The push-pull character of the three compounds, particularly the anilino-derivative, suggests their potential application in optoelectronics.

Syntheses, characterization, stereochemistry and complexing properties of acyclic and macrocyclic compounds possessing α-amino- or α-hydroxyphosphonate units: a review article

In this article we shall review the salient aspects concerning the syntheses, characterization, and complexing properties of variously substituted mono- and bis-(α-amino)- and (α-hydroxy)-phosphonates. Characterization of these compounds was mainly achieved by 1H, 13C, and 31P NMR spectroscopy, by FABMS techniques, and by X-ray diffraction analyses. Hydrolytic cleavage in alkaline solutions of the dialkyl esters gave the corresponding monoesters, which also show good complexing properties toward standard metals and lanthanides. The last section of this article is dedicated to a review of the synthesis, characterization and stereochemistry of cyclophanes, and macrocyclic compounds possessing phosphonate units.

Effect of the π Bridge and Acceptor on Intramolecular Charge Transfer in Push–Pull Cationic Chromophores: An Ultrafast Spectroscopic and TD‐DFT Computational Study

Three (donor-π-acceptor)(+) systems with a methyl pyridinium or quinolinium as the electron-deficient group, a dimethyl amino as the electron-donor group, and an ethylene or butadiene group as the spacer have been investigated in a joint spectroscopic and TD-DFT computational study. A negative solvatochromism has been revealed in the absorption spectra, which implies a solution color change, and interpreted by considering the variation in the permanent dipole moment modulus and orientation upon photoexcitation. The fluorescence efficiency decreases upon increasing solvent polarity, in agreement with the excited-state optimized geometries (planar in low-polarity media and twisted in high-polarity media). Femtosecond transient absorption has revealed the occurrence of a fast photoinduced intramolecular charge transfer (ICT) and the molecular factors that determine an efficient ICT. Considering the crucial role of the ICT in tuning the nonlinear optical (NLO) properties, these compounds can be considered promising NLO materials.

SYNTHESIS OF NEW ORTHO-HYDROXY ARYL PHOSPHONATE MONOMERS

Commercially available bridged bis-phenols react with diethylphosphite to give bis-phosphates, which are easily transformed by LDA, in good yields, to bis-ortho hydroxy aryl phosphonates. These new monomers are of great relevance for the synthesis of novel macrocycles and for thermal resistant polycondensates containing phosphonate moieties.

Modeling, design and synthesis of new heteroaryl ethylenes active against the MCF-7 breast cancer cell-line

A dataset of 50 compounds was used to generate a QSAR model and to design 9 new heteroaryl ethylenes. These compounds were synthesized, tested in vitro and a significant agreement with in silico predictions observed. Studies using Laser Scanning Confocal Microscopy pointed out that the compounds may act by different mechanisms.

Phosphorylated macrocycles: structures, complexing properties, and molecular recognition

Procedures were developed for functionalization of macrocycles by introducing a phosphonic group either directly linked to the aromatic rings (in the case of cyclophanes or calixarenes) or as a pendant arm. For these compounds to be used as artificial receptors for amino alcohols and amino acids, the host molecule must possess not only negative charges arising from the phosphonate moieties but also a hydrophobic binding site, such as electron-rich aromatic residues. We designed inter alia new dissymmetric macrocycles capable of being involved in three binding modes with guest molecules, viz., hydrogen bonding, electrostatic attraction, and π-cation interactions. The NMR characterization of the macrocycles, their stereochemistry in solution and in the solid state, and the use as chiral receptors for biologically relevant molecules are described.

A GENERAL SYNTHETIC APPROACH TO α-HYDROXY PHOSPHORYL COMPOUNDS

Abstract A general synthetic way for the preparation of a large variety of α-hydroxy phosphoryl compounds is here reported. In our approach, trialkyl phosphite is added in equimolar amount, at room temperature and under strong acidic conditions (HCI gas), to the corresponding carbonyl compound dissolved in anhydrous dioxane. The reaction is quite exothermic and cooling is often needed; 10–15 min reaction time is sufficient in order to assure almost quantitative yields in the desired product, which can be easily isolated as a white pure solid by concentration of the reaction mixture. The reaction works in an excellent way with all kind of aliphatic, aromatic and heteroaromatic aldehydes. The α-hydroxy phosphonates obtained were fully characterized by 1H- and 31P-NMR, by FAB-MS and IR spectroscopy. When o-carboxybenzaldehyde was used as a reagent, cyclic dialkyl phthalide-3-phosphonates were obtained in very good yields (≥90%).

Nanoscale uniform self-assembled monolayers of fluorescent zinc(II) complexes on the Si(100) surface

The synthesis of self-assembled monolayers on Si(100) substrates of a new fluorescent Zn(II) Schiff-base complex is reported. Chemisorbed species are characterized by the combination of fluorescence scanning near-field optical/atomic force microscopy (SNOM/AFM), and by fluorescence spectroscopy. Both SNOM/AFM results indicate the existence of a monolayer on the surface, while optical SNOM images highlight the contribution of the monolayer to the local fluorescence. While chemisorbed molecular monolayers exhibit a distinct fluorescence, analogous to that observed in solution, cast thin films do not show any emission. Photoluminescent properties of the monolayer can be related to its nanoscale uniform, ordered structure.

Synthesis and Characterization of New Organic Phosphonates Monomers as Flame Retardant Additives for Polymers

Commercially available polyphenols react with diethylphosphite to give polyphosphonates, which are easily transformed by LDA in good yields to polyorthohydroxy aryl phosphonates. Moreover, some bis-benzyl aminobenzyl phosphonates have been prepared in good yields. These new monomers are of great relevance for the synthesis of thermal resistant polycondensates containing phosphonate moieties.