Elsevier

Inorganica Chimica Acta

Volume 360, Issue 3, 15 February 2007, Pages 728-740
Inorganica Chimica Acta

Review
Organized chromophores in layered inorganic matrices

Dedicated to professor Vincenzo Balzani.
https://doi.org/10.1016/j.ica.2006.07.048Get rights and content

Abstract

Recent studies on the intercalation of azoic and xanthenic dyes and of donor–acceptor couples into the interlayer region of hydrotalcite-like compounds (HTlc) will be reviewed. In particular, the synthetic strategy followed to optimize the intercalation of chromophores, together with the chemical, photophysical and photochemical characterization of the obtained materials are presented. The use of HTlc containing easily exchangeable counter-ions allowed to introduce in the interlayer region, anionic chromophores with large size and different shape; moreover, materials with tunable optical properties (emission spectra and lifetimes) have been obtained by the accurate control of synthetic procedures. The confinement of chromophores into the interlayer nanometer-space affords the control of the distance between the guest species and hence of their interactions. Confocal microscopy has been used to investigate the distribution of the fluorescent guests into the microcrystals and the host–guest interactions. Furthermore, the preparation and the fluorescence properties of new intercalation compounds formed between HTlc and xylenol orange anions and between 4-phenylazobenzoate and HTlc, in the presence and absence of an electric field, are reported and discussed with the aim to furnish a wider overview of the potentiality of this emerging class of hybrid materials.

Graphical abstract

Effect of the chromophore packing inside the interlayer region of Zn–Al–HTlc on the emission spectra of the chromophore as a consequence of co-intercalate removal water (anhydrous, close symbols and hydrated sample, open symbols) supported by the computer generated models for the same samples.

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Introduction

The preparation and characterization of properly functionalizable materials is a challenge that involves solid-state, materials chemistry and physical chemistry [1], [2], [3]. Furthermore, the use of hybrid strategy provides a promising way of producing innovative inorganic–organic materials with ordered nanostructure and tailored properties. Layered solids have interesting physical and chemical properties, because of their structural anisotropy, and because they can be easily functionalized by intercalation of species having specific properties [4], [5]. Among the layered solids, hydrotalcite-like compounds also known as layered double hydroxides (LDHs) or anionic clays, occupy a unique place because they are practically the only example of layered solids with positively charged layers and intercalated exchangeable interlayer anions to maintain charge neutrality. Their general formula is in fact [M(II)1−xM(III)x(OH)2](Ax/n) · mH2O, where M(II) can be Mg, Zn, Ni, Cu, Fe, Co, Mn and M(III) = Al, Cr, Fe, An is the layer charge compensating inorganic or organic anion, x ranges between 0.2 and 0.4 [6], [7]. Their great scientific and technological relevance stems from the rich intercalation chemistry as well as from the extensive applications in catalysis, [8], [9] adsorption, [10] separation, [11] medical science, [12], [13], [14] and polymeric nanocomposites [15], [16].

For example, intercalation of guest species possessing chromophoric groups into different layered host compounds gives rise to nanostructured materials with desired optical properties [17], [18], [19], [20]. The properties of the hybrid materials generally differ from those of the pure guest species, since the host–guest interactions that affect the distribution and orientation of guests in the host, and the guest–guest interactions [21], [22] allow to modulate the photophysical and photochemical properties of the guest, [23] whose thermal and photochemical stability can also be improved. The insertion and/or adsorption, by simple ion exchange procedure, of anionic dye into HTlc produces inorganic–organic nano-hybrid materials that exhibit photophysical properties which are strongly affected by the geometrical and chemical environment experienced by the dye [24]. The effects cited above, not only confirm the feasibility to fabrication of optical materials with LDHs and the chromophore anions but also bring a beneficial pathway to further develop such electronic and optical materials.

The idea beyond the present research project and the collaboration between two research groups with complementary competences in intercalation chemistry and photochemistry is to characterize the hybrid materials in order to obtain a deeper knowledge on the effects of the inorganic matrices and the constrained environment in the photophysical and photochemical behaviour of organic chromophores. Furthermore, information can be obtained on the arrangement of the organic moieties in the interlayer region and feedback to eventually modify the preparation procedure to have ordered materials.

In this paper, a brief review of the previous studies carried out on intercalation compounds formed by methyl orange (MO), [23] fluorescein (Fl), [25] phenolphthalein (Phe), [26] 2-naphthalene sulfonic acid (2NSA), [3] 4-benzoyl benzoic acid (4BBA) [3] and 9-anthracene carboxylic acid (9ACA) [3] will be presented in order to point out the strategy followed in the preparation and characterization of the hybrid materials. Moreover, the results obtained from new materials constituted by Zn–Al-hydrotalcite with xylenol orange or phenyl-azo-benzoate anions intercalated in the presence of an external electric field to produce materials with NLO properties, will also be presented and discussed.

Section snippets

Materials

The layered hosts, commonly used for the dye uptake, were Zn–Al and Mg–Al hydrotalcites in carbonate form with the formula [M(II)1-xAlx(OH)2]CO3x/2·mH2O, prepared by homogeneous precipitation of Mg(Zn)–Al hydroxycarbonates accomplished by urea hydrolysis at 100 °C [27]. After precipitation, the recovered solids were dispersed in 0.1 mol/dm3 solution of Na2CO3 and stirred for one day at room temperature to exchange the residual chloride anions, derived from the metal chlorides used in the

Results and discussion

In this paper, the work carried out in our laboratories during the last few years on the topic will be reviewed and some original not yet published results will be reported. The studies carried out allowed to deeply characterize new organic–inorganic materials with specific and tunable optical properties and to achieve information on the arrangement of guests into the host nanometer-size interlayer region. This combined inorganic and photophysical investigation has been extended to dyes

Conclusions

The results of an extensive investigation on HTlc-intercalation compounds with azoic and xanthenic dyes and donor–acceptor couples, prepared by ion-exchange or memory-effect procedures, have been presented. The azoic dyes, MO and FAB were intercalated using the Zn–Al–HTlc in cloride form. The xanthenic dyes (Fl, XO and Phe) having high steric hindrance were exchanged from perchlorate-HTlc or introduced taking advantage of the memory-effect procedure. The fluorescence spectra of the

Acknowledgements

The authors thank the Ministero per l’Università e la Ricerca Scientifica e Tecnologica (Rome) for the financial support through the project FIRB (RBNE017MB5).

Loredana Latterini received her PhD in chemistry at the University of Perugia (1995); she was visiting Research Staff Member at the Center for Photochemical Science – Bowling Green State University, Bowling Green, OHIO, USA in the laboratory of prof. M.A.J. Rodgers and at the Katholieke Universiteit Leuven, Leuven – Belgium, in the laboratory of prof. F.C. De Schryver where she gained experience with ultra-fast time-resolved techniques and optical and scanning probe microscopies. Currently she

References (38)

  • G. Ferey

    J. Solid State Chem.

    (2000)
  • G. Schulz-Ekloff et al.

    Micropor. Mesopor. Mater.

    (2002)
  • A. Vaccari

    Appl. Clay Sci.

    (1999)
  • M. Turco et al.

    J. Catal.

    (2004)
  • L. Perioli et al.

    J. Phys. Chem. Solids

    (2006)
  • V. Ambrogi et al.

    Int. J. Pharm.

    (2001)
  • U. Costantino et al.

    Polym. Degrad. Stab.

    (2005)
  • G.G. Aloisi et al.

    J. Mater. Chem.

    (2002)
  • G. Alberti et al.
  • Vincente Rives (Ed.), Layered Double Hydroxides: Present and Future, Nova Science Publishers, New York,...
  • F. Leroux et al.

    J. Mater. Chem.

    (2005)
  • K.P. de Jong

    J. Phys. Chem. B

    (2006)
  • I. Fujita et al.

    Chem. Mater.

    (2005)
  • U. Costantino, M. Nocchetti, Layered Double Hydroxides and their intercalation compounds in Photochemistry and...
  • L. Tammaro et al.

    J. Polym. Sci., Part A: Polym. Chem.

    (2005)
  • M. Ogawa et al.

    Chem. Rev.

    (1995)
  • R. Kaito et al.

    J. Phys. Chem. B

    (2003)
  • M.B.J. Roeffaers et al.

    Chem. Phys. Chem.

    (2005)
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    Loredana Latterini received her PhD in chemistry at the University of Perugia (1995); she was visiting Research Staff Member at the Center for Photochemical Science – Bowling Green State University, Bowling Green, OHIO, USA in the laboratory of prof. M.A.J. Rodgers and at the Katholieke Universiteit Leuven, Leuven – Belgium, in the laboratory of prof. F.C. De Schryver where she gained experience with ultra-fast time-resolved techniques and optical and scanning probe microscopies. Currently she has a post-Doc at the University of Perugia. The scientific activities of dr. Latterini deals with photophysical and photochemical characterization of systems in solution and in solid phase. The properties of the electronic excited states of simple and complex compounds have been investigated by use of steady-state and pulsed techniques. Microscopy techniques have been used to relate the optical properties of complex systems to their structure. In particular, this investigation methods has been applied in the study of intercalation compounds formed between layered double hydroxides and organic chromophores. She is author and co-author of more than 50 scientific papers, 3 monographs in scientific books, and more than 70 communications to national and international conferences.

    Morena Nocchetti was born in 1968. She graduated in chemistry at the Perugia University, Italy in 1994. In 1999, she obtained the Ph.D degree in chemistry in the same University with the thesis “Studies on the intercalation chemistry of the synthetic anionic clays and lamellar phosphates”. Since 2005 she is a researcher of “General and Inorganic Chemistry” at Faculty of Pharmacy, University of Perugia. The scientific activity involves the preparation, the structural characterization and the study on the reactivity of hydrotalcite-like compounds and zirconium phosphates and phosphonates. Many materials have been prepared and functionalized with species having specific properties as chromophores, drugs and polymers. This intercalation compounds have been tested as catalysts, as inorganic fillers for polymeric nanocomposites, and studied for their photophysical and photochemical properties.

    Prof. Gian Gaetano Aloisi is Full Professor of Physical Chemistry at the Faculty of Sciences of the University of Perugia since July 2001, he is author of about 80 scientific publications and 70 congress communications in the field of Photochemistry and Photophysics. His scientific interest was in particular directed to the study of the properties of the lowest excited singlet and triplet states of organic molecules (diarylethenes, furocoumarins, dyes, drugs, etc.) in order to characterize their various decay pathways. He gained particular experience in the study of the photoinduced charge and electron transfer processes by means of steady-state and pulsed fluorometry and by laser flash photolysis. In the last years, its interest was directed to the study of photodamages produced by drugs (phenotiazines, quinolones and antimalarials) towards several biological targets (lipids, proteins, DNA, etc.) and to the photophysical characterization of intercalation complexes of different dyes with layered solids through absorption, emission and flash photolysis techniques.

    Prof. Umberto Costantino is Full Professor of “General and Inorganic Chemistry” at the Faculty of Pharmacy, University of Perugia, since 1986. He is national coordinator of a PRIN project and he is one of the proposer of the Excellence Research Centre “Innovative Nanostructured Materials for Chemical, Phisycal and Medical Applications”. Prof. Costantino is known to be an expert of the intercalation chemistry of layered solids. He has a large and documented scientific experience on tetravalent metal phosphates and phosphonates and on layered double hydroxides. He contributed to spread the knowledge of these compounds getting ready original methods of synthesis, carrying out fundamental research on layer rigidity and on exfoliation processes, studying the ion exchange and intercalation mechanisms of species belonging to different classes of organic compounds, including amino acids, dyes and polymers. Many of intercalation compounds obtained have been studied for potential applications on heterogeneous catalysis, electrochemistry, photochemistry and polymeric composites. He is author and co-author of more than 165 scientific papers, 15 monographs in scientific books, 14 industrial patents and more than 200 communications to national and international conferences. He is the author of two chapters on the intercalation chemistry and layered phosphates chemistry of the book ”Comprehensive Supramolecular Chemistry” (J. M. Lehn, Ed.), Vol. VII, and of a chapter of the book “Layered Double Hydroxides: Present and Future” (V. Rives, Ed.).

    Fausto Elisei, was born in Spoleto (PG) in 1955, full professor of Physical Chemistry at the University of Perugia. Teacher of courses of Physical Chemistry (degree in Chemistry and Biotechnology). He is member of the Rector Cabinet, delegated of the Rector for the “Prevention and Safety Service” of the University of Perugia, member of the Standing Committee of the Division of Physical Chemistry (Italian Chemical Society), member of the Co-ordination Committee of the Interfaculty Degree Program in Biotechnological Sciences, coordinator of the Master in “Biotechnological methodologies for the environmental depollution”.

    His research activity has been mainly devoted to subjects of Photophysics and Photochemistry. In particular, the properties of the electronic excited states of aromatic and ethero-aromatic compounds have been mainly investigated by steady-state and transient techniques, sometimes also by quantum mechanical calculations. Such investigations, carried out on several classes of aromatic compounds, have generally been devoted to a complete description of the mechanisms of the reactive and non-reactive processes induced by light absorption and to look at the molecular properties and experimental conditions able to control the reaction yields and directions. Recently, he is involved in the preparation and photophysical characterization of new hydrid (organic/inorganic) nanostructured materials (hydrotalcites and nanoparticles).

    The results of the research work were the subject of more than 100 scientific papers published in international journals.

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