Pierre Marsau

Photoinduced control of cation binding ability of non-conjugated bichromophoric receptors

Abstract Several receptors based on nonconjugated bichromophores displaying phototunable cation binding properties have been designed and studied. Some of these systems undergo a reversible photocyclisation to produce a crown ether or a cryptand; the photoswitching induces significant changes on a long time scale (hours to months after illumination) of the complexing ability of the material. Other bitopic receptors display a sudden and transitory change of cation concentration only during the singlet excited state lifetime.

A novel crown ether–cryptand photoswitch

A new photoactive bis-anthracenyl crown undergoes a reversible photocyclisation to form a cryptand, with the efficiency of the forward reaction and the rate of the thermal reverse reaction strongly affected by the presence of cation substrates.

Synthesis and fluorescence emission properties of a bis-anthracenyl macrotricyclic ditopic receptor. Crystal structure of its dinuclear rubidium cryptate

The new macrotricyclic ditopic bis-anthracenyl receptor (1) displays remarkable fluorescence properties (dual emission: ‘monomer’ and excimer type) which are strongly and selectively modified by binding RbClO4 and 1,7-diaminoheptane dihydrochloride.

Synthesis and cation complexing properties of a ne dissymmetrical fluorescent coronand

Abstract A dissymetrical coronand containing two different subunits (i.e. anthracene and naphthalene) has been synthesized and the crystalline structure established. 3 forms a 2:1 complex with Na + and a 1:1 complex with K + . A negative cooperativity has been revealed with Na + . Some spectroscopic properties of 3 are described.

Barium Cation Complexation by Flexible Mono- and Ditopic Receptors, Studied by UV Absorption and Fluorescence Spectroscopy

The metal cation (Ba++) binding ability of a family of designed nonconjugated bichromophoric [bis(para-phenylene)- or bis(para-diphenylene)]polyoxamacrocyclic coronands has been studied in acetonitrile in the ground state and in the singlet excited state. The association constants (K) at ambient temperature have been determined from UV absorption and fluorescence data, by use of the LETAGROP-SPEFO programme. The ground state complexes exhibit 1:1 or 1:1 and 2:1 (cation/ligand) stoichiometries and a large variety of association constants, as well as diverse cooperative effects. Remarkably, TTO5O5 {1,4,7,10,13,21,24,27,30,33-decaoxa[13.15]-(1,4)benzenophane} shows a strong binding ability (log β = 10.3) with a positive cooperativity. The apparent association constants measured from stationary fluorescence data were found to be lower in some cases than those observed in the ground state; these results strongly suggest that a transitory photodecomplexation between the metal cation and the phenolic oxygen atoms occurs in the S1 state. An X-ray structure analysis was performed on the barium complex of a related podand and the Ba++ coordination number was found to be 10.

Molecular and Crystal Structure of a Bisanthracene-9,10-diyl Macrocyclic Coronand AAO5O5 and of its Bis-1,4-endoperoxide, a Bistetraoxapaddlane ∗

AAO5O5 3, a bisanthracene macrocyclic cyclophane, is known to be an excimer-type fluorosensor for sodium cations and to encapsulate electron-deficient species such as paraquat. Its bis-1,4-endoperoxide 4 is a tetraoxapaddlane. The molecular and crystal structures of 3 and 4 are described.

Studies on aromatic trichromophore systems incorporating anthracene moieties. Part 1. Synthesis, fluorescence and photoreactivity

Trichromophoric molecules (A2A, A2Pyr, A2Phen), incorporating two anthryl moieties, linked by a three-membered chain, and a third chromophore (anthracene, pyrene and phenanthrene) attached by a longer ester chain, have been synthesized. Their electronic absorption spectra and their fluorescence emission were studied in very dilute solution at room temperature in comparison with models representing the different absorbing parts of the trichromophore. Careful examination of their photophysical properties has shown the existence of triple complexes in the ground and excited states. The photochemistry of these molecules is governed by the ‘4π+ 4π’ cyclomerization of the bisanthracene part linked by the three-membered chain. The involvement of the excited complex on the pathway of the cyclomerization is not readily explainable.

Synthesis and photophysical properties of fluorescent anthracenophanes incorporating two polyoxadioxoalkane chains

Anthracene macrolides In(n= 1–4) display dual fluorescence (‘monomer’/excimer) sensitive to the number of links of the chain n and temperature. The excimer fluorescence quantum yield is particularly high (0.24–0.39 in toluene) in comparison with those of related anthracenophanes or bichromophores. A thermodynamic study of the fluorescence emission has enabled us to evaluate the activation energy of excimer formation (25.1–27.2 kJ mol–1 for n= 1, 3, 4, and 15.0 kJ mol–1 for n= 2), its enthalpy of stabilization (–14.2 to –21.7 kJ mol–1), and the repulsive potential in the ground state between two anthracenes after radiative deactivation of the intramolecular excited complex (38.5–53.1 kJ mol–1). These values are discussed as a function of n and compared with literature data.The spectroscopic properties of In were found to be weakly cation dependent except for I4 and Sr2+ or Ba2+ where moderate effects were detected in UV absorption or fluorescence emission spectra. The failure to encapsulate the alkali and alkaline-earth cations is ascribable to the rigidity of the system which presumably hinders the formation of a stable co-ordinating sphere around the cation.The fluorescence emission of the single crystals is described and correlated with the molecular packing mode. The excimer-type emitting crystals (n= 2 and 4) contain pairs or stacks of aromatic rings whereas ‘monomer’-type emitting crystals do not show any important overlap between anthracenes.

The water inclusion complex of a fluorescent diprotonated anthracenocryptand

6,9,17,20-Tetraoxa-3,12-diaza[14.8 3,12 ](9,10)anthracenophane perchlorate monohydrate, A 22 .(HClO 4 ) 2 .H 2 O (C 30 H 42 N 2 O 4 2+ .2ClO 4 - .H 2 O), is a diprotonated form of a molecular receptor described previously. The N + -H bonds are oriented inside the cavity which encapsulates one molecule of water. The single-crystal fluorescence spectra of the free base (A 22 ) and of the title compound are reported.