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José A. Campo

Other affiliations: CEU San Pablo University
Bio: José A. Campo is an academic researcher from Complutense University of Madrid. The author has contributed to research in topics: Pyrazole & Mesophase. The author has an hindex of 20, co-authored 81 publications receiving 1180 citations. Previous affiliations of José A. Campo include CEU San Pablo University.


Papers
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Journal ArticleDOI
TL;DR: A new family of Pt(II) luminescent metallomesogens based on dicatenar pyridyl pyrazolate ligands [Pt(pzR(n,n)py)2] has been prepared, and their mesomorphic and photophysical properties are described as mentioned in this paper.
Abstract: A new family of Pt(II) luminescent metallomesogens based on dicatenar pyridylpyrazolate ligands [Pt(pzR(n,n)py)2] (R(n,n) = C6H3(OCnH2n+1)2, n = 4–18) has been prepared, and their mesomorphic and photophysical properties are described. The compounds were isolated as red (n = 4–8) or yellow (n = 10–18) solids at room temperature, but the first ones were converted to yellow crystals by slow evaporation of a chloroform–acetone mixed solution. All of them behave as discotic liquid crystal materials, exhibiting hexagonal columnar mesophases (Colh) in a wide range of temperatures. Photoluminescence studies in the solid state at variable temperatures showed a high emission in the liquid crystalline phase, which was significantly red-shifted with respect to the yellow-green emission of the solid state. This photophysical change was attributed to the formation of aggregates through Pt(dz2)–Pt(dz2) interactions, thereby giving rise to the metal–metal-to-ligand charge transfers (3MMLCT) responsible for the luminescence observed. Taking advantage of these properties we have fabricated polymeric solid supports doped with the platinum complex [Pt(pzR(10,10)py)2], which can be used as temperature sensors for real technological applications. In addition, the Pt–bispyrazolate complexes and their corresponding pyrazole ligands have been proved to be useful as chemosensors towards Pd2+, Zn2+, Cd2+ and Hg2+ metal ions.

50 citations

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TL;DR: The luminescent behaviour of selected compounds as a function of the temperature indicates that the luminescence is maintained in the mesophase, and the new complexes are photoluminescent both in the solid state and in solution at room temperature.
Abstract: A series of ionic bis(pyrazole)-silver(I) and -gold(I) complexes [ML2][A] (M = Ag, Au; A = BF4−, PF6−, NO3−), prepared by coordination of the mesomorphic L = Hpz2R(n) or non-mesomorphic L = HpzR(n) pyrazole ligands (Hpz2R(n) = 3,5-bis(4-alkyloxyphenyl)pyrazole; HpzR(n) = 3-(4-alkyloxyphenyl)pyrazole), has been studied. The complexes exhibit enantiotropic behaviour, showing smectic A (SmA) mesophases. The choice of the ligands allows the achievement of ‘H’ or ‘U’ molecular shapes, which appear to be responsible for the attainment of liquid crystal mesophases, these not being dependent on the coordinating or non-coordinating nature of the A counteranions. The new complexes are photoluminescent both in the solid state and in solution at room temperature. In addition, the luminescent behaviour of selected compounds as a function of the temperature indicates that the luminescence is maintained in the mesophase.

48 citations

Journal ArticleDOI
TL;DR: New pyridine-functionalised pyrazole compounds and their corresponding silver complexes have been synthesised and characterised and it was observed that in both structures, the dimers are layer-like packed, their lamellar structures being related to that of the mesophases found in both kinds of compounds.
Abstract: New pyridine-functionalised pyrazole compounds [HpzR(n)py] (R(n) = C6H4OCnH2n+1; n = 12, 14, 16, 18; 1–4) and their corresponding silver complexes [Ag(HpzR(n)py)2][A] ([A] = NO3−, BF4−; 5–12) have been synthesised and characterised. All of them, with the exception of 1, are liquid crystal materials exhibiting monotropic or enantiotropic SmA mesophases, in contrast to the non-mesomorphic related R(n)-monosubstituted compounds. Because the molecular shape is a factor determinant in the organisation of molecules in the liquid crystal phase, we were interested in solving the crystal structure of representative examples of the mentioned compounds, such as 1 and 6. So, the X-ray crystal structure of [HpzR(12)py] 1 shows the presence of dimeric units through N–H⋯N hydrogen bonds, which conform to an elongated molecular shape containing a double chain length. On the other hand, the structure of [Ag(HpzR(14)py)2][NO3] 6 also evidenced Ag–Ag bonded dimers from ‘U’-shaped cationic entities. These dimers exhibit four chains, two by two alternated, so giving rise to a longer molecular length. Of particular interest was to observe that in both structures, the dimers are layer-like packed, their lamellar structures being related to that of the mesophases found in both kinds of compounds. Furthermore, the analysis of the optical data of the compounds 2 and 4 and the silver compounds 5, 6, 9 and 10 as representative examples pointed out their luminescent behaviour as well as their good ability to act as fluorescent probes for Zn2+, Cu2+ and Ag+. An increase in the fluorescence quantum yields is observed in the final complexes produced in the titrations, this fact being specially notable when 9 was used as the starting compound.

42 citations

Journal ArticleDOI
TL;DR: In this paper, four new 3,5-disubstituted pyrazoles HpzR2 containing long-chain 4-n-alkyloxyphenyl substituents [R=C6H4OCnH2n+1; n=4 (1), 6 (2), 12 (5), 14 (6) and 14(6)] have been prepared and characterised, all of them showed mesomorphic behavior, the stability and the range of the mesophases increasing with the length of the chain on the pyrazole

40 citations

Journal ArticleDOI
TL;DR: In this article, the luminescent properties of β-diketone pyridine ligands and boron derivatives were investigated both in the solid state and in solution and it was proved that the liquid crystal state does not quench the fluorescence emission.
Abstract: Pyridine-functionalized β-diketone ligands of the type 1-(2-pyridyl)-3-(4-n-alkyloxyphenyl)propane-1,3-dione [HLR(n)py] (R = C6H4OCnH2n + 1, n = 12 (1), 14 (2)) were carried to react with the BF2 fragment giving rise to the corresponding adducts [BF2(LR(n)py)] (n = 12 (5), 14 (6)) which were characterized and their luminescent and thermal behaviour studied. All the ligands and boron derivatives are photoluminescent both in the solid state and in solution. The related compounds 2-[3-(4-n-alkyloxyphenyl)propane-1,3-dion-1-yl]pyridinium chloride [HLR(n)pyH]Cl (n = 12 (3), 14 (4)) were also proved to have luminescent properties. On the other hand the organometallic compounds [Pd(η3-C3H5)(HLR(14)py)][PF6] (7) and [Pd(η3-C3H5)(LR(14)pyH)][PF6] (8), based on the coordination of the [Pd(η3-C3H5)]+ fragment to the above neutral 2 or ionic 4β-diketone derivatives, respectively, were also established to be luminescent materials, compound 8 exhibiting liquid crystalline properties. The luminescent behaviour of all compounds was also investigated as a function of the metal addition of Zn2+ and Cu2+ ions. As a result it is proven that the free β-diketone pyridine ligands [HLR(n)py], the related chloride salts [HLR(n)pyH]Cl and their palladium(II) complexes behave as fluorescence chemosensors for Zn2+ and Cu2+. The luminescent behaviour of the allyl-palladium complex 8, which exhibits enantiotropic liquid crystalline properties, was also studied as a function of the temperature. As a consequence it is established that the liquid crystal state does not quench the fluorescence emission.

35 citations


Cited by
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TL;DR: A comparison study of 3D Networks Based on Polypyrazolates, Metal 1,2,4-Triazolate Frameworks, and Univalent Coinage-Metal Tetrazolate Framework 1025.
Abstract: 2.1.2. Low Topology/Framework Density 1003 2.1.3. Side Group Directed Superstructures 1003 2.2. Synthesis Considerations 1003 2.3. Special Properties 1004 3. Metal Imidazolate Frameworks 1004 3.1. Chains and Rings 1004 3.2. Zeolitic and Zeolite-like Frameworks 1006 3.2.1. SOD-Type Zinc(II) 2-Methylimidazolate 1007 3.3. Nonporous 4-Connected Networks 1010 3.4. Polyimidazolates 1011 4. Metal Pyrazolate Frameworks 1011 4.1. Clusters and Chains 1011 4.2. 3D Networks Based on Polypyrazolates 1012 5. Metal 1,2,4-Triazolate Frameworks 1014 5.1. Simple 3-Connected Networks 1015 5.2. Quasi-Imidazolates 1018 5.3. With Coordinative Substituents 1019 5.4. With Secondary Counterions and/or Ligands 1021 6. Metal 1,2,3-Triazolate Frameworks 1023 7. Metal Tetrazolate Frameworks 1025 7.1. Univalent Coinage-Metal Tetrazolate Frameworks 1025

1,433 citations

Journal ArticleDOI
TL;DR: The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionIC liquid crystals and particularly to ionic liquids will also be provided.
Abstract: This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.

563 citations