Intramolecular Cooperative Effects in Multichromophoric Cavitands Exhibiting Nonlinear Optical Properties

We report on the design, synthesis, and characterization of a new class of multichromophoric cavitands based on resorcin[4]arenes. The novel compounds have exhibited high values of second-order nonlinear optical (NLO) properties, as evidenced by electric-field-induced second harmonic generation (EFISHG) measurements. Theoretical calculations indicate the presence of edge-to-face T-shaped interactions between the aromatic building blocks within these multichromophoric systems, which is further supported by the detection of hypsochromic shifts in UV-vis and upfield aromatic chemical shifts in 1H NMR. We proved for the first time that the gain in the quadratic hyperpolarizabilities of multichromophoric NLO macrocycles, originating from the near parallel orientations of the subchromophores, can be partially suppressed if the distance between the dipolar subunits falls into a specific range, where intramolecular cooperative and/or collective effects are operative. Our finding will contribute to the better understanding of the phenomenon of cooperativity in new molecular materials with promising NLO properties. (Figure Presented). © 2015 American Chemical Society

Synthesis of 5-Carboxamidotriazoles via Azide-Alkyne Cycloaddition–Aminocarbonylation Sequence

5-Carboxamidotriazoles were prepared in the palladium-catalyzed aminocarbonylation of the corresponding iodotriazole using various amines as N-nucleophiles under mild reaction conditions. The iodoheteroarene substrates were obtained in good yields in copper-catalysed azide-alkyne cycloaddition of iodoalkynes (2’-iodophenylacetylene and ethyl iodopropiolate) and benzyl azide

Efficient synthesis of alkynyl amides via aminocarbonylation of iodoalkynes

Iodoethynylbenzene as iodoalkyne model compound was aminocarbonylated with tert-butylamine under carbon monoxide atmosphere in the presence of in situ palladium(0) catalysts. The formation of the unsaturated carboxamide (alkynyl amide) is always accompanied by that of the Glaser coupling product, diphenylbutadiyne. The yield of the amide-forming reactionwas optimised by the systematic variation of the phosphine ligand, carbon monoxide pressure and temperature. The scope of the reaction was investigated by using various primary and secondary amines including amino acid methyl esters as Nnucleophiles. 17a-(Iodoethynyl)-testosterone was also functionalised by using this methodology providing the corresponding 17a-(carboxamidoethynyl)-testosterone derivatives in up to 96% yields. The reaction was extended to 1-(iodoethynyl)cyclohex-1-ene and 1-iodohex-1-yne. Ethyl iodopropiolate gave the enamine type product by the addition of amine to the alkyne functionality which was formed from the iodoalkyne via deiodination under standard minocarbonylation conditions. The bromo analogue, bromoethynylbenzene has shown lower reactivity than the corresponding iodo derivative

Facile, High-Yielding Synthesis of 4-Functionalised 1,2,3- Triazoles via Amino- and Aryloxycarbonylation

4-Iodo-1,2,3-triazoles were synthesised via azide-alkyne cycloaddition of alkynyl Grignard reagent and benzyl azide followed by iodination reaction. The aminocarbonylation and aryloxycarbonylation of 4-iodo-1,2,3-triazoles were carried out in the presence of various N- and O-nucleophiles, resulting in the corresponding triazole-based 4-carboxamides and 4-esters, respectively. Both high-yielding reactions were carried out under mild conditions (atmospheric CO pressure, 70°C)

Fluorescence quenching studies on the interaction of a novel deepened cavitand towards some transition metal ions

A novel 'three-level' deepened cavitand featuring a significantly sizable portal has been synthesized and its interaction with some transition metal ions has been investigated in THF/H2O binary solvent using fluorescence quenching technique. The results suggest that among the used transition metal ions including Ag+, Cd2+, Cu2+, Fe3+, Cr3+, Hg2+, La3+, Mn2+, Ni2+, Zn2+ and Co2+, only Fe3+ and Cu2+ show good quenching ability. In order to interpret the quenching mechanism, the Stern-Volmer kinetics, and the presence of both the dynamic and static quenching have been discussed. It was found that the simultaneous presence of the sphere-of-action static quenching and dynamic quenching model agrees very well with the experimental results. The limits of detection for Fe3+ and Cu2+ were found to be 2.1 x 10(-6) mol L-1 (3 sigma) and 3.6 x 10(-6) mol L-1 (3 sigma), respectively. Cations with potential interference, such as K+, Na+, Mg2+, Ca2+, Co2+, La3+ and Mn2+ do not have significant effects on the determinations of Fe3+ and Cu2+. This cavitand can be potentially applied as optical sensor for the detection of Fe3+ and Cu2+