New Tetrafunctionalized Cone Calix[4]arenes as Neutral Hosts for Anion Recognition

The synthesis and anion binding properties of several new cone calix[4]arenes having different flexibility and tetrafunctionalized at the upper rim with various type of hydrogen bonding donor groups such as thioureas (1-3), trifluoroacetamides (4, 5) and perfluorinated alcohols (6) are reported. The results obtained show that thiourea receptors are the most effective in the complexation of all anions and that the rigid cone compound 2 is more efficient than the mobile cone analog 1 in the binding of spherical anions, whereas the reverse is true for the complexation of tetrahedral H2PO4- anion

Dynamic and Structural NMR Studies of Cavitand-Based Coordination Cages

The interionic structure, kinetic stability, and degree of anion encapsulation of coordination cages 1 were studied by PGSE, NOE, and EXSY NMR techniques. The rate constants for the formation/dissociation processes at 296 K were obtained independently via (1)H-NOESY and (19)F-NOESY experiments giving, respectively, k(obs) = 0.30 +/- 0.04 s(-1) in CDCl(3) and k(obs) = 5.2 +/- 0.8 s(-1) in CD(3)NO(2)/CDC(13) (7.1) mixture with the proton probe, and k(obs) = 0.33 +/- 0.06 s(-1) in CDCl(3) and k(obs) = 5.0 +/- 0.8 s(-1) in CD(3)NO(2)/CDC(13) (7/1 mixture) with the (19)F probe. PGSE experiments showed that in CDCl(3) not only the encapsuled anion but also the external anions translate with the same rate as the cage. (19)F,(1)H-HOESY experiments indicated that an average of five external triflate anions are located in the equatorial sites close to the palladium moieties, while two of them approach the polar pockets formed by the alkyl chains. In a CD3NO2/CDC13 (7/1) mixture only one or two anions are in close proximity with the cage, while the others are solvated. In all the considered solvents (benzene, chloroform, methylene chloride, and nitromethane) the inclusion of a single unsolvated triflate anion in the cage is quantitative. (19)F,(1)H-HOESY experiments indicated that the charged guest head points toward one metal center. Therefore, while the ionic aggregation level and kinetic stability of coordination cages 1 are solvent dependent, anion encapsulation is not

Propagazione in vitro di orchidee native di praterie aride: effetti delle condizioni colturali sulla germinazione, lo sviluppo delle plantule e la formazione di tuberi

Within the European Project LIFE 10/NAT/IT/000243 - Friuli Venezia Giulia Region - four orchid species distinctive of the habitat of Community Importance 62A0 (Eastern sub-Mediterranean dry grasslands) have been propagated by seeds. The main aim of the Project is plants reintroduction, with reinforcement of wild populations and biodiversity conservation. Two different culture media were compared for germination and protocorms growth: Basal Medium 1 and Basal Medium 1 added with coconut water. Results showed that coconut water stimulates the germination of Anacamptis coriophora, Anacamptis pyramidalis and Gymnadenia conopsea; a positive effect of this natural compound brought out also for Serapias vomeracea, during following protocorms development. Furthermore, culture medium enriched with coconut water promoted plantlets growth, evaluated as length of young leaves. within 6 – 9 months from seeding. Unlike the other species, Serapias vomeracea grew without distinction to growth medium. All orchid plants have been maintained in in vitro conditions until tubers production. These underground perennial organs gain an important role in nutrient storage and propagation, maintaining viable dormant buds during adverse environmental conditions. Consequently, their presence could provide a good response during plants transferring in greenhouse for the acclimatization

Design and Preparation of Mesogenic Cavitands

Mesogenic cavitands have been prepared for the first time. They form uniaxial disordered columnar mesophases (D-hd). The structure requirements for mesophase formation have been identified: (i) macrocyclic cores with thickness below 5 Angstrom and (ii) four large (3,4,5-tris{[4-(dodecyloxy)benzyl]oxy}benzoyl)oxy groups at the upper rim. The orientation of the molecules within the columns is random, excluding the formation of intracolumnar cavities of molecular dimensions in the mesophase

Synthesis and coordination chemistry of lower rim cavitand ligands

Four new cavitand ligands, modified at the lower rim with cyano and pyridyl functional groups, have been synthesized and their coordinative behaviour toward transition metal ions has been explored. The outcome of the self-assembly of these compounds in the presence of different metal precursors is biased toward the formation of intramolecular complexes, independent of the coordination geometry imposed by the metal centre. Dimeric species have been obtained by decreasing the number of ligands at the lower rim from four to two and by using a metal precursor capable of exchanging four ligands simultaneously

Dynamic Materials through Metal-Directed and Solvent-Driven Self-Assembly of Cavitands

A dual-coded dynamic material was created by the bimodal self-assembly protocol sketched in the scheme. The combination of two orthogonal and reversible interactions, namely solvophobic aggregation (SA) and metal coordination (MC), allows precise control at each step of the self-assembly cycle, leading to the formation of rodlike supramolecular architectures

Host-Guest Driven Copolymerization of Tetraphosphonate Cavitands

The outstanding complexing properties of tetraphosphonate cavitands towards N-methylpyridinium salts were exploited to realise a new class of linear and cyclic AABB supramolecular polymers through host-guest interactions. The effectiveness of the selected self-association processes was tested by 1HNMR studies, whereas microcalorimetric analyses clarified the binding thermodynamics and revealed the possibility of tuning entropic contributions by acting on the flexibility of the guest linker. Although the formation of linear polymeric chains for a rigid system was demonstrated by X-ray analysis, the presence of a concentration-dependent ring-chain equilibrium was indicated by solution viscosity measurements in the case of a very flexible ditopic BB guest co-monomer. Supramolecular alternating copolymers: Cyclic and linear AABB supramolecular copolymers were prepared by connecting complementary monomeric units through host-guest interactions. Thermodynamic and topological control of this process was achieved by controlling the flexibility of the ditopic guest spacer, solvent and concentration. The structure of the alternating copolymer formed by self-assembly of a bis(tetraphosphonate cavitand) and methyl viologen is shown