Palladium-Mediated Catalysis Leads to Intramolecular Narcissistic Self-Sorting on a Cavitand Platform

Palladium-catalyzed aminocarbonylation reactions have been used to directly convert a tetraiodocavitand intermediate into the corresponding carboxamides and 2-ketocarboxamides. When complex mixtures of the amine reactants are employed in competition experiments, no ‘mixed’ products possessing structurally different amide fragments are detected either by 1H or 13C NMR. Only highly symmetrical cavitands are sorted out of a large number of potentially feasible products, which represents a rare example of intramolecular, narcissistic self-sorting. The reactivity order of the amine reactants and the changes in the Gibbs energies calculated using the semiempirical PM6 model suggest that this self-sorting process is kinetically controlled

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

Influence of base additives on the selectivity of palladium-catalysed aminocarbonylation: Highly selective functionalization of a cavitand scaffold

Tetracarboxamides and tetrakis(2-ketocarboxamides) of resorcinarene-based cavitands have been synthesised in palladium-catalysed aminocarbonylation of the corresponding tetraiodocavitand. In this way, deepened cavitands with the same functionalities at the upper rim were obtained even in the simultaneous application of two primary amines as N-nucleophiles. The influence of base additives on the unexpectedly high chemoselectivity towards tetra-functionalised products, i.e. tetrakis(2- ketocarboxamides) and tetracarboxamides, has been investigated in details

Szupramolekuláris kémia, homogén katalízis: Nagy szelektivitású reakciók kavitand alapvázakon

Az átmenetifém katalizált homogén kataliti- kus karbonilezési, kapcsolási reakciók a szin- tetikus kémia fontos eszközeivé váltak. A szerzők a szupramolekuláris kémia egyik új vegyületcsaládjának, a kavitandoknak a szin- tézisét valósították meg e reakciók segítségé- vel. A kavitand alapváz felső peremén új szin- tek kialakításával nagyméretű befogadó („gaz- da”) molekulák szintézisére nyílt lehetőség. A kiemelkedő kemoszelektivitás és hozamok elérését a felső peremen található négy funk- ciós csoport összehangolt reakciója tette le- hetővé

Temperature-dependent fluorescence quenching of a cavitand derivative by copper ions

Temperature dependence of fluorescence quenching of a cavitand derivative by Cu2+ ion has been studied in dimethylformamide solution. Results derived from PL studies highlighted two temperature regions where the formation of cavitand–Cu2+ complexes is based on significantly different molecular processes. From the experimental results and the comparison of the calculated interaction energies of the possible complex structures obtained by density functional calculations, it is assumed that at lower temperatures the Cu2+ ion takes place in the cavity while at higher temperature region Cu2+ is coordinated to the outer part of the cavitand with its almost retained solvation shell

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+

Synthesis of elongated cavitands via click reactions and their use as chemosensors

A very efficient modular reaction protocol was developed to attach various functionalities to a rigid cavitand scaffold. In this way, aryl, iodoaryl, benzyl, pyrrolidylmethyl groups, as well as a polyethyleneglycol chain were attached to the 'triazol-level' of the cavitand. The palladium-catalyzed ethynylation of the iodoarene moieties, followed by the copper(I)-catalyzed azide-alkyne cycloaddition produced novel cavitands with significantly elongated binding pockets. The dimensions of these molecules are calculated to be at least 9 angstrom x 18 angstrom, which place them amongst the largest unimolecular hosts obtained by pure covalent synthesis. A cavitand-based click conjugate is used for selective complexation of Cu2+ and Fe3+, providing significant fluorescent quenching