Pyrene?p-tert-butylcalixarenes inclusion complexes formation: a surface photochemistry study (original) (raw)
Related papers
Surface Photochemistry: Organic Molecules within Nanocavities of Calixarenes
Current Drug Discovery Technologies, 2007
In order to gain more information regarding photochemical processes in heterogeneous environments (opaque or powdered samples) laser induced time resolved luminescence and diffuse reflectance transient absorption spectroscopies were used for the study of benzophenone (and other neutral organic molecules) as guests and p-tert-butylcalix[n]arenes with n = 4, 6 and 8 (H n CLX[n]) and partially or totally O-propylated p-tert-butylcalix[4]arenes (H n Pr m CLX[4], n = 2, 1 and 0; m = 2, 3 and 4, respectively) were used as hosts. One of the main conclusions was that the solid support can deeply affect or even control the photochemistry of an adsorbed probe. A simple new methodology for lifetime distribution analysis of the decay of the probes included into calixarenes and other nanocavities was applied with success for decay data obtained with the use of intensified charge couple devices, i.e. intensified charge couple devices, ICCDs. Diffuse reflectance laser flash photolysis and gas chromatography-mass spectrometry techniques also provided complementary information, the former about transient species and the latter regarding the final products formed after light absorption.
Quenching of Pyrene Fluorescence by Calix[4]arene and Calix[4]resorcinarenes
Journal of Fluorescence, 2008
Interactions involving calixarene and its derivatives are of major importance due to their widespread applications as unique hosts. Fluorescence from a common probe pyrene is used to study interactions involving calix[4] resorcinarene [1a] and its tetra-morpholine derivative [1b] in 1 M aqueous NaOH. These compounds efficiently quench the pyrene fluorescence. A comparison with the fluorescence quenching behavior of N-methylmorpholine clearly indicates the presence of long-range interactions involving 1a and 1b; the interactions are specific to the calixarene molecular framework. This is not the case for a tetra-nitro-substituted calix[4]arene [2b], an electron/charge acceptor quencher, as p-nitrophenol also shows similar interactions with pyrene. Effectiveness of cesium as the quencher of pyrene fluorescence is reduced in the presence of electron/charge donating 1b; fluorescence enhancement is observed upon addition of cesium as the concentration of 1b is increased in the solution. The role of calixarene framework in interactions involving such compounds is established.
ChemistrySelect, 2019
The photophysical behaviour of a single pyrene substituted calix[4]arene derivative (MPCX4) has been investigated, as a function of pH, using steady state fluorescence and timeresolved emission spectroscopic techniques. An interesting dimer emission band has been observed exclusively in the alkaline solution (pH > 8) which has been attributed to the hydrophobic and stacking interaction between the pyrene moieties of the adjacent MPCX4 molecule. The self-assembled MPCX4 is disrupted by the introduction of another calixarene based host, p-sulfonatocalix[6]arene (SCX6), which eventually leads to the 1:1 complex formation between MPCX4 and SCX6, which is further characterised by 1 H NMR, FT-IR and HR-MS techniques. This complexation between MPCX4 and SCX6 also leads to the modulation of the prototropic equilibrium of MPCX4.
Calix[4]arenes bearing a tropylium substituent as hosts for organic cations
Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2007
Four novel calix[4]arenes bearing one cycloheptatrienyl substituent and two calix[4]arenes with one tropylium substituent at the wider rim were synthesized. Cycloheptatrienyl-and tropylium-calixarenes represent two states of a potentially photoswitchable calixarene host. The complexation of selected hosts with organic cations such as quinolinium, ammonium and tropylium ions was studied. It was found that the complexation of organic cations by the tropylium-substituted host was much stronger in CDCl 3 solution than by the related cycloheptatrienyl-host. Aryltropylium ions are bound by tropylium hosts. Accordingly, dimers of the host itself are formed both in CDCl 3 solution and in the gas phase. Because of the intramolecular charge transfer tropyliumcalix[4]arenes are qualified as chromogenic hosts. These undergo two acid-base equilibriums depending on the concentration and the solvent.
2007
Calixarenes are macrocyclic compounds which can be produced with different sizes and functionalities. They are mainly synthesized by 'one-pot' base-induced condensation reactions of the corresponding phenol(s) with paraformaldehyde. For example, the most accessible and commonly-used calixarene, tetra-p-tert-butylcalix[4]arene is produced by such a reaction, of p-tertbutylphenol with para-formaldehyde. The well-defined "calix"- or "cup"-like shape in most of these compounds have made them attractive targets for host-guest and/or supramolecular studies and many other applications. -- The work described in this thesis concerns the synthesis and a study of the properties of some new modified calix[4]arenes and calix[4]naphthalenes which were synthesized using different methods. Among the topics dealt with are the following: (a) An attempt to develop a new methodology for the wide-rim modification of calix[4]naphthalene by using a suitably pre-functionalized p...
Synthesis of meso-2,2’-bipyridyl-substituted calix[4]arenes and their response to metal cations
Chimica Techno Acta
A convenient synthetic approach to meso-substituted with 2,2’-bipyridine and 1-(pyridin-2-yl)isoquinoline residues calix[4]arenes is reported. This approach involves the reaction of generated in situ 2-lithio-calix[4]arene with 1,2,4-triazine precursor with the following aromatization of the obtained adduct, and the aza-Diels-Alder reaction of the 1,2,4-triazinyl-substituted calix[4]arene with 2,5-norbornadien or in-situ generated 1,2-dehydrobenzene. The UV/fluorescence response of thus obtained meso-pyridyl-substituted calix[4]arenes to metal cations is studied.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2003
A calix[4]arene derivative containing ethoxycarbonylmethoxy groups in the coordination sphere and an iminopyridinium indicator group was studied by FT-IR spectroscopy in acetonitrile solution. The characteristic changes of n (C Ä/O) stretching vibration offered an opportunity for the improvement on selectivity of the ion recognition process of this ligand. The shift of the carbonyl stretching vibration band depended on complex formation as well as on the equilibrium constants of complex formation. In the case of sodium complex, a well-defined isobestic point was detected in the n (CÄ/O) region while altering the sodium concentration. The affinity of thallium(III) to form complex with calixarene 1 was found comparable with those of lithium, sodium or calcium. The complex was found to be an M 2 L type supramolecule, whereas one molecule of triethylamine was necessary for the formation of each complex.
Reductive and oxidative reactions of calix[4]arene derivatives
Tetrahedron Letters, 1991
Reductive cleavage of 25,26,27,28-tetramethoxy-p-tert-butykalix[4]arene with K results in the formation of 26,28-dimethoxy-p-t-butylcalix[4]arene. The reaction of 25,27dihydroxycalix[4]arene with NOzBF4 in acetonitrile results in its oxidation to calixdiquinone 6. Calixarenes are cyclic phenol-formaldehyde oligomers capable of including small organic molecules into their cavities.1 During the last years considerable synthetic efforts have been invested on improving the binding capabilities of the calixarenes by modifying the ligating groups at the intraannular (lower rim) positions.2 We have shown3 that the complete array of OH groups of pt-Bu-calix[4]arene (1) and of pt-Bu-calix[8]arene can be removed in a two-step process using the method developed by Kenner and Williams.4 In the first step, the OH groups are derivatized into diethyl phosphate esters which are cleaved in the second step by their treatment with K in liquid NHs. More recently we5 and Reinhoudt and coworkers.6 have shown that the method is applicable for the preparation of partially OH-depleted calixarenes such as 2. t-Bu t-Bu Bu-t 4 R=OHR'=OMe 5 R = OH R' = OpO(OEt)2 t-Bu
Optical Spectroscopy and Theoretical Studies in Calixarene Chemistry
Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2007
This review summarizes different applications of optical spectroscopic methods in calixarene chemistry including UV/Vis spectrometry, vibrational spectroscopic techniques (FTIR and Raman spectroscopy), luminescence spectroscopy (including fluorescence and phosphorescence), ellipsometry and various optical microscopic methods. Moreover, the results of theoretical studies (AM1, PM3, DFT, ab initio, etc.) are summarized based on selected papers in the field of conformational studies, thermodynamics and complexation features. About 300 references are processed systematically from the results reported mainly in the recent years with emphasis on the potential of practical application of these molecules.