-
[show abstract]
[hide abstract]
ABSTRACT: Solid-state CPL measurements were performed for the first time on hybrid, laminar materials based on γ-ZrP pillared with organic diphosphonates. Ad hoc optically pure diphosphonates were synthesized and the luminescence properties of their complexation with Tb(III) were verified in solution. CD and CPL measurements showed that the bistriazolylpyridine chromophores bonded to the metal provided an effective chiral environment that produced significant signals. In the case of the γ-ZrP-derived materials, experimental evidence and simple molecular modeling hinted to the occurrence of supramolecular chirality in the particles, induced by the intrinsic dissymmetry of the organic diphosphonates or by the intercalation of chiral species such as 1-phenethylamine. Chirality at the supramolecular level was revealed in the solid state by the CPL signals measured from reporter Tb(III) ions intercalated in the hybrid matrix.
Microporous and Mesoporous Materials 03/2013; 169:222-234. · 3.29 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Two layered zirconium phosphates containing Ru(bpy)(3)(2+) mono- or diphosphonates and diquat, {Ru(bpy)(3)(2+)[]/ZrP/DQ(++)} and Ru(bpy)(3)(2+)[]/ZrP/DQ(++), covalently attached to the phosphate layers exhibit notable photovoltaic response (the maximum V(OC), J(SC), and FF were 0.093 V, 16.8 microA cm(-2) and 0.33, respectively). The photocurrent spectra indicate that the photovoltaic response is due predominantly to direct photoexcitation of gamma-ZrP host, Ru(bpy)(3)(2+) and diquat acting as hole and electron traps, respectively, for the charge separated state of the semiconductor.
Physical Chemistry Chemical Physics 05/2009; 11(16):2922-7. · 3.57 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The laser flash photolysis of material 1 (layered γ-ZrP containing covalently attached Ru(bpy)3- and C60-phosphonates), dyad 2, and material 3 (amorphous solid Zr(n-BuO) derivative of dyad 2) was accomplished. Zirconium salts, regardless of their amorphous or layered structures, appear to be excellent hosts for developing long-lived charge-separated states between C60 and Ru(bpy)3 derivatives. Moreover, the presented evidence points to the important fact that the inorganic scaffolding acted as a semiconductor, harvesting the electrons and/or holes produced at the active organic components. These findings suggest that the studied materials could be suitable for the building of practical solar cells.
02/2008;
-
Angewandte Chemie International Edition 11/2006; 45(41):6918-20. · 13.45 Impact Factor
-
Chemistry 01/2006; 2(12):1578 - 1584. · 5.93 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The construction of organic−inorganic scaffolds based on γ-zirconium phosphate and polyethylenoxa diphosphonates is described. Microcrystalline materials with a controlled, low degree of pillaring are synthesized and characterized by elemental analysis, X-ray powder diffraction, solid-state NMR, and thermogravimetric analysis. The mechanism for the topotactic polyethylenoxa-pillaring reaction is proposed and confronted with previous ones suggested for the reaction of nonpolar organic diphosphonates. The affinity among the polyethylenoxa chains and the superficial acidic phosphates of the layered salt is thus clearly evidenced. The work shows how the inner structure of the pillared microcrystals may be easily modified by a second exchange of the remaining superficial phosphates by other phosphorus species as the low-polar hypophosphite. The rigidity of the layers and the wedge-like effect of intercalated amines at the edges of the microcrystals cause them to increase the interlayer distance, and hence porosity, in a flash fashion.
02/2005;
-
[show abstract]
[hide abstract]
ABSTRACT: The synthesis of three novel pyrazole-containing complexing acids, N,N,N′,N′-{2, 6-bis[3-(aminomethyl)pyrazol-1-yl]-4-methoxypyridine}tetrakis(acetic acid)(1), N,N,N′,N′-{2, 6-bis[3-(aminomethyl)pyrazol-1-yl]pyrazine}-tetrakis(acetic acid) (2), and N,N,N′,N′-{6, 6′-bis[3-(aminomethyl)pyrazol-1-yl]-2, 2′-bipyridine}tetrakis(acetic acid) (3) is described. Ligands 1–3 formed stable complexes with EuIII, TbIII, SmIII, and DyIII in H2O whose relative luminescence yields, triplet-state energies, and emission decay lifetimes were measured. The number of H2O molecules in the first coordination sphere of the lanthanide ion were also determined. Comparison of data from the EuIII and TbIII complexes of 1–3 and those of the parent trisheterocycle N,N,N′,N′-{2, 6-bis[3-(aminomethyl)pyrazol-l-yl]pyridine}tetrakis(acetic acid) showed that the modification of the pyridine ring for pyrazine or 2, 2′-bipyridine strongly modify the luminescence properties of the complexes. MeO Substitution at C(4) of 1 maintain the excellent properties described for the parent compound and give an additional functional group that will serve for attaching the label to biomolecules in bioaffinity applications.
Helvetica Chimica Acta 10/2004; 80(1):86 - 96. · 1.48 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Pillared γ-zirconim phosphate at low level with a diphosphonic acid resulting from the addition of pentaethyleneglycol to diethyl vinyl phosphonate was prepared and used as a porous matrix to intercalate LnCl3 (Ln = Eu, Tb) and 2,2-bipyridyl (bpy). The uptake levels of both species in mild conditions were 0.35 and 0.10 equivalents per Zr, respectively. Strong interactions between the lanthanide ion and the polyethylenoxa chains were evidenced. Although powder XRD of the composite showed two interlayer distances (1.7 and 2.2 nm) indicating that the material was not homogeneous, excitation luminescence spectra confirmed strong lanthanide bpy-sensitized emission which was more than 50 times higher than that in nonpillared γ-zirconium phosphate.
03/2004;
-
Angewandte Chemie International Edition 03/2004; 43(5):619-21. · 13.45 Impact Factor
-
02/2003;
-
[show abstract]
[hide abstract]
ABSTRACT: The title complexes displayed a marked dependence of their luminescence properties upon pyridine substitution. The ligand with the 4-carbamoyl-substituted pyridine showed a long-lived luminescence of near-unity quantum yield for Tb3- and quite reasonable values for Eu3+, Sm3+ and Dy3-, thus making it an excellent candidate for a luminescent probe to be attached to biomolecules by a peptide-like linkage.
Photochemical and Photobiological Sciences 09/2002; 1(8):613-8. · 2.58 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: [structure: see text] New macrocyclic chelates based on bis-pyrazolylpyridine and diethylenetriaminepentaacetic acid are synthesized, and the remarkable luminescence properties of their lanthanide chelates are reported.
Organic Letters 02/2002; 4(2):213-6. · 5.86 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The hydrophilic oxygen atoms of polyethylenoxide chains inserted as pillars in γ-zirconium phosphate form hydrogen bonds with the acid groups of the host. As a result the pillars are almost perpendicular to the γ layers. Upon changing the pH level of the supernatant solution the hydrogen bonds are broken and the pillars become almost perpendicular to the layers (shown schematically). Thus there is a reversible enlargement–shortening of the interlayer space.
Angewandte Chemie International Edition 11/1999; 38(22):3351 - 3353. · 13.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Several new ionophores derived from crown ethers and iminodiacetic subunits attached to 3-aroylcoumarins have been synthesized and fully characterized. The alkaline-earth complexes of these new ligands were studied from their UV–visible and fluorescence data. Some systems displayed strong bathochromic shifts upon complexation with Mg2+ that may make them useful signaling devices of this cation. The corresponding Eu3+ and Tb3+ chelates were easily formed and their photophysical properties were measured. In all the cases, lanthanide emission lifetimes were in the range of milliseconds albeit quantum yields were low. Possible energy-transfer mechanisms are discussed.
Journal of Photochemistry and Photobiology A: Chemistry.
-
[show abstract]
[hide abstract]
ABSTRACT: Good afternoon to everyone. I'm going to talk about the important topic of hydrogen storage, the role of porous materials to accomplish it and our modest contribution to this field.
-
[show abstract]
[hide abstract]
ABSTRACT: Using molecular shape for the functional control of multicomponent systems is one of the challenges in the field of supramolecular chemistry. The well-known emission in the visible region of certain lanthanide (III) salts has found a new dimension by the controlled assembly of supramolecular architectures to enshroud and excite the metal. The emission properties of these systems find applications as luminescent probes in sensing schemes, interaction with bio-molecules, or light conversion systems. Complexes of Tb(III) and Eu(III) can in some cases be highly luminescent and typically exhibit emission lifetimes in the millisecond range. These long lifetimes provide a facile means to detect biomolecules labeled with lanthanide from the short-lived background emission of biosystems. The strongly ionic nature of the bonding in solid lanthanide complexes results in coordination geometries that reveal a balance between electrostatic and steric demands. The inclusion of lanthanide guests into macrocycles, cryptands, cavi-tands and spherands had the purpose of shielding the metals from solvent molecules whose OH, NH or CH groups are able to heavily quench lanthanide luminescence (intensity and lifetime) by deactivation of their emissive levels by vi-bronic coupling. The literature on the various chemical systems, based on nitrogen heteroaromatic rings, used to sensitize lanthanides will be thoroughly reviewed including those molecules synthesized by the authors which displayed high quantum yield of lan-thanide emission.
-
Tetrahedron Letters 49(18):2911-2915. · 2.68 Impact Factor
-
Tetrahedron Letters 48(7):1091-1094. · 2.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The preparation of organic–inorganic materials based on the topotactic exchange reactions of the γ phase of zirconium phosphate and polyphenyl bisphosphonates is reported. The treatment of these materials with hypophosphoric, phosphorous and methylphosphonic acids easily led to an isomerization of the γ phases to their α allotropes. These reactions rendered finely engineered supramolecular structures by means of mild, simple processes performed in the solid–liquid interface. This kind of clean γ-to-α transformations described in our work has few precedents in the literature and allows for the effortless preparation of libraries of similar materials in which the testing of a given set of properties versus subtle structural changes may be easily performed. Using this rationale we have produced materials able to store up to 1.7% (w/w) of H2 at 77 K and 1 atm with such high ultramicroporosity that the DOE-goal H2 densities established for 2010 could be complied at pressures well below 5 atm.
Chemical Engineering Journal.
