Studio di nuovi materiali metallorganici acentrici multifunzionali per applicazioni in opto-elettronica

Responsabili di progetto

Alessandra Forni, Marina Fonari

Accordo

MOLDOVA - ASM-not in force - Academy of Sciences of Moldova

Bando

CNR/ASM 2015-2016

Dipartimento

Scienze chimiche e tecnologie dei materiali

Area tematica

Scienze chimiche e tecnologie dei materiali

Stato del progetto

Rinnovo

Relazione per il rinnovo

joint-reportfirmato.pdf

Proposta di ricerca

In the past decade, the rational design and synthesis of coordination polymers (CPs) and metalorganic materials (MOM) [1] including metal-organic frameworks (MOF) [2] have attracted great attention due to their fascinating structural motifs and potential exploitations for the synthesis of technologically important materials. From the crystal engineering viewpoint the coordination networks with desired topologies can be tuned by taking advantage of well-defined metal coordination geometries in combination with carefully chosen rigid bridging ligands [3]. From the materials science viewpoint these high stable and low soluble materials disclose practically infinite venue for multifunctional materials with combination of useful properties (adsorption & magnetism; adsorption & fluorescence; adsorption & biological activity) [4]. CPs could play a key role in the development of LED (light emitting diod) materials because one can tune the emission color and stability of the complex readily by manipulating the ligand, the coordination environment around the central atom, and by encapsulating the target dyes molecules in the polymeric matrix [5]. Recently, MOFs based on their superiorities in rational design and syntheses have become a hot research focus in the second harmonic generation (SHG) field due to significant success in the directed design of asymmetric coordination networks [6,7]. Although rather numerous examples of the crystalline acentric coordination networks including those built from achiral components are reviewed, coordination polymers, which display both very strong blue fluorescent emission and SHG response in the solid state, still remain, to the best of our knowledge, a few [8,9].
The proposal is aimed at the design, synthesis, structural study and comprehensive evaluation of optical properties of hybrid MOMs based on transition metals, Zn(II), Cd(II), Cu(II), Mn(II,III) and Co(II) with an emphasis on the non-centrosymmetric CPs having the advantages of the porosity of the coordination network, possibility to reveal a luminescence response to the guest inclusion, and high thermal stability. The Moldovan team is experienced in the directed design of CPs with pronounced luminescent properties that include the non-centrosymmetric ones built from achiral components. In the framework of this proposal the mixed-ligand blend approach will be used to manipulate by the ligands coordinated to the metal centers, taking the asymmetric carboxylates of different length and rigidity as the bridging ligands, and asymmetric pyridine-n-oximes and other N-donor-type molecules as the terminal ligands. The SHG response is expected to be attributed mainly to the electronic asymmetry (push-pull effect) enhanced by a synergistic effect of the donor -acceptor (D-A) system of the pyridine-n-oxime ligand, and electron-withdrawing effect of coordinated carboxylic group. The choice of Zn(II) and Cd(II) atoms in this series is further justified by the possibility of the acentric diamondoid or pseudo-diamondoid networks, and by avoiding of unwanted d-d transitions in the visible region. These metals can have tetrahedral (Zn) or pentagonal bipyramidal (Cd) coordination extensions, which intrinsically lack a center of symmetry. They can also form complicated clusters with various coordination ligands to form 1-D to 3-D MOFs. Due to the close-shell electronic configuration of the metals, neutral coordination networks are expected. The noncentrosymmetric solids based on 1D chains and related helical structures obtained by only varying the counterions are reported. This direction is planning to be developed for comparison on the base of Cu(II) structures, although the lower coordination number of Cu(II) against Zn/Cd can afford MOMs of lower dimensionality, which lessen the chance of acentric materials.
The project needs the presence of multidisciplinary competences encompassing different fields such as computational chemistry, chemical synthesis, material science and analytical chemistry. The Moldavian team will be engaged in synthesis, characterization and X-ray analysis of the designed compounds, while the Italian team will perform the second-order NLO response measurements and will tackle the molecular modelling study of the compounds.
The proposing ASM and CNR partners have already shown the fruitful collaborations in the borderline fields, on the design, synthesis and characterization of tetradentate Schiff bases complexes with optimized NLO response [10], and structure-property relationship for the multicomponent organic solids [11].


[1] L. Pan, M. B. Sander, X. Huang, J. Li, M. Smith, E. Bittner, B. Bockrath, J. K. Johnson, J Am Chem Soc 2004, 126, 1308.
[2] H. Li, M. Eddaoudi, M. O'Keeffe, O. M. Yaghi, Nat 1999, 402, 276.
[3] O. M. Yaghi, M. O'Keeffe, N. W. Ockwig, H. K. Chae, M. Eddaoudi, J. Kim, Nat 2003, 423, 705.
[4] Metal-Organic Frameworks: Applications from Catalysis to Gas Storage, First Edition. Edited by David Farrusseng. 2011 Wiley-VCH Verlag GmbH & Co. KGaA.
[5] J. Yu, Y. Cui, H. Xu, Y. Yang, Z. Wang, B. Chen, G. Qian, Nat Comm 2013, 4, Article number: 2719 doi:10.1038/ncomms3719
[6] O. R. Evans, W. Lin, Acc Chem Res 2002, 35, 511.
[7] C. Wang, T. Zhang, W. Lin, Chem Rev. 2012, 112, 1084.
[8] Ren-Gen Xiong, Jing-Lin Zuo, Xiao-Zeng You, Brendan F. Abrahams, Zhi-Ping Bai, Chi-Ming Che, Hoong-Kun Fun, Chem Commun 2000, 2061.
[9] J.-S. Guo, G. Xu, X.-M. Jiang, M.-J. Zhang, B.-W. Liu, G.-C. Guo, Inorg Chem 2014, 53, 4278.
[10] see e.g. J. Gradinaru, A. FornForni, V. Druta, F. Tessore, S. Zecchin, S. Quici, N. Garbalau, Inorg. Chem. 46, 884, 2007.
[11] M. E. Crisan, P. Bourosh, M. E. Maffei, A. Forni, S. Pieraccini, M. Sironi, Y. M. Chumakov, PLOS ONE, 2014, 9, e101892.

Obiettivi della ricerca

New non-centrosymmetric MOMs will be prepared through the following intermediate objectives:

- Design of non-centrosymmetric compounds with the expected architecture based on the crystal engineering approaches. The nature and location of asymmetric ligands, such as pyridine-n-oxime, isonicotineamide, sulfate anion, to be inserted in the complexes will be optimized in relation to their NLO response;


- Synthesis of the most promising complexes, as individuated in the previous analysis;


- Characterization of the synthesized compounds by elemental analysis, IR, UV-vis and X-ray diffraction; selection of the samples with the strongest luminescence response;


- 2nd order NLO measurements in solution (by EFISH generation technique) and on powder (by Kurtz-Perry method) of the synthesized compounds. Comparison of the EFISH measurements with the computed hyperpolarizability will allow to evaluate the possible presence of aggregation effects on the experimental NLO response.

Ultimo aggiornamento: 30/04/2025