Nuovi materiali ibridi inorganici/organici basati sul legante triimidazolo optoelettronicamente attivo

Responsabili di progetto

Alessandra Forni, Marina Fonari

Accordo

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

Bando

CNR/ASM biennio 2018-2019 2018-2019

Dipartimento

Scienze chimiche e tecnologie dei materiali

Area tematica

Scienze chimiche e tecnologie dei materiali

Stato del progetto

Nuovo

Proposta di ricerca

In the past decade the interest in functional luminescent coordination polymers (CPs) or metal-organic frameworks (MOF) has received increasing attention due to their appealing properties for potential applications in material science such as light-emitting and display devices, chemical sensors and biomedical applications [1-2]. These hybrid materials can combine not only a wide range of emissive phenomena related to their inorganic and/or organic components, but their supramolecular organization could provide new emissive features and a different optical behaviour. For example, the permanent porosity in MOF could be exploited for the reversible storage and release of guest substrates while the luminescent properties may be affected by these guests, thus providing a way for their recognitions and sensing. Moreover. the rigidity imposed by the lattice in MOF constrains the ligands in ways that are not typically observed for a free complex in solution, which can lead to increased fluorescence lifetimes and quantum efficiencies.
In this context, the present proposal aims at the preparation of CPs or MOF based on a simple organic moiety, namely cyclic triimidazole (C9H6N6, 1), recently investigated by the Italian team by a combined experimental, structural and theoretical investigation for its outstanding properties of crystallization-induced and mechanochromic emission associated with an ultralong room temperature phosphorescence [3]. The presence of three nitrogen atoms with idealized D3h symmetry make 1 an appealing and still unexplored tecton for molecular design of luminescent CPs and MOF.
The present project will tackle first coordination of 1 to copper(I) halides which are known to give a variety of structural formats by simply changing reaction conditions [4]. Preliminary results on the reactivity with CuI evidenced that different structural motifs going from 1D to 3D coordination polymers can be simply obtained by changing solvents or reaction temperatures [5-6]. Within this proposal we plan to implement these results and to perform a systematic investigation on the synthesis of CPs or MOF based on 1 and Cu(I) by evaluating different synthetic procedures including traditional solution reactions (with different solvents, molar ratios, reagents, etc.) together with solvothermal and mecanochemical syntheses. Furthermore, due to the copper d10 electronic configuration, the emissive properties of the obtained materials might be affected by external stimuli [7-8], thus their thermochromic, vapochromic and mechanochromic behaviour will also be investigated. In particular, porous Cu(I) MOF will be tested as sensors for the detection of various volatile small molecules such as alcohols, ketones, halocarbons, benzene and formaldehyde on the basis of their luminescent responses of "turn-on" and "turn-off" [9-11]. A possible use as heterogeneous catalysts in Huisgen-type "click" cycloaddition reactions of Cu(I) compounds will be also envisaged [12].
Subsequently, the chemical modification of 1 with introduction of functional groups such as pyridine or bypiridine will be planned in order to provide additional linkers useful for the synthesis of CPs or MOF. Besides Cu(I), the project aims at developing synthetic routes for the preparation of emissive hybrid organic/inorganic materials based on transition metal centres of d6 Ru(II), d8 Pt(II) and d10 Zn(II) and Cd(II) electronic configurations by using as organic ligand triimidazole 1 or its functionalized derivatives. The syntheses will be coupled with a comprehensive evaluation of the spectroscopic and structural properties of the new compounds, together with a rationalization of the results by computational techniques.
The complementary expertise provided by the Moldavian and Italian teams are ideally suited for the accomplishment of the present proposal which requires competences in different fields spanning from computational chemistry, chemical synthesis and material science to analytical chemistry. The Italian team will be responsible for the synthesis of 1 and its derivatives, for the computational studies and spectroscopic characterization of the compounds, while the Moldavian team will perform the synthesis and X-ray analysis of the new CPs and MOF. The proposing ASM and CNR partners have an established and fruitful collaboration as proved by several common publications [6, 13-16]. Joined funding of this project by the CNR and ASM Institutions will help the consortium to participate in a very competitive way to future EU Horizon2020 calls, particularly the Future and Emerging Technologies Open call (FET Open), thanks to the very innovative nature of the proposed compounds and envisaged applications.

1) Cui, Y. et al., Chem. Rev. 2012, 112, 1126
2) Allendorf, M. D. et al., Chem. Soc. Rev. 2009, 38, 1330
3) Lucenti, E.; Forni, A.; Righetto, S.; Cariati E. et al., J. Phys. Chem. Lett. 2017, 8, 1894
4) Peng, R.; Li, M.; Li, D. Coord. Chem. Rev. 2010, 254, 1
5) Lucenti, E.; Cariati, E.; Forni, A. et al., MSCMP 2016, Chisinau, Moldova, September 12-16, 2016
6) Bold, V.; Kravtsov, V.; Lucenti, E.; Cariati, E.; Fonari, M. EEC - 2017, Chisinau, Moldova, March 2-3, 2017
7) Cariati, E.; Lucenti, E.; Righetto, S. et al., Coord. Chem. Rev. 2016, 306, 566
8) Ford, P. C.; Cariati, E.; Bourassa, J. Chem. Rev. 1999, 99, 3625
9) Kivi, C. E.; Song, D. Dalton Trans. 2016, 45, 17087
10) Yu, Y. et al., Inorg. Chem. 2015, 54, 11590
11) Yu, Y. et al., Chem. Commun. 2014, 50, 1444.
12) Fu, Q. et al., Chem. Commun. 2016, 52, 12226
13) Gradinaru, J.; Forni, A. et al. Inorg. Chem. 2007, 46, 884
14) Crisan, M. E.; Bourosh, P.; Forni, A.; Chumakov, Y. M. et al., PLOS ONE 2014, 9, e101892
15) Melnic, E.; Forni, A.; Cariati, E.; Kravtsov, V.; Fonari, M. S. et al., Cryst. Growth Des. 2016, 16, 6275.
16) Malaestean, I. L.; Kravtsov, V. Ch.; Lipkowski, J.; Cariati, E.; Righetto, S.; Marinotto, D.; Forni, A.; Fonari, M. S. Inorg. Chem. 2017, 56, 5141.

Obiettivi della ricerca

New luminescent CPs or MOF will be targeted according to the following intermediate objectives:
- Investigation of the reactivity of ligand 1 with Cu(I) salts (CuI, CuBr) via traditional reactions in solution or by solvothermal methods.
- Structural characterization of the products by X-ray diffraction studies (single crystal or powder) and evaluation of polymorphs formation under different reaction conditions
- Spectroscopical characterization to select the samples with the most promising luminescence response to be further investigated with time-resolved, variable temperature emission analysis
- Research and evaluation of thermochromic, vapochromic and mechanochromic behaviour
- Study of the reactivity of 1 with different metal centers (Ru2+, Pt2+, Zn2+, Cd2+) and full characterization of the obtained hybrid inorganic/organic materials.
- Synthesis of functionalized derivatives of 1 containing groups, such as pyridine or bipyridine, useful for the preparation of supramolecular CPs or MOF. Application to these new ligands of the best synthetic protocols individuated for 1.
- Computational studies by accurate quantum-mechanical techniques on both starting ligands and discrete models of CPs and MOFs to probe the mechanisms of their observed luminescent behaviour.

Ultimo aggiornamento: 01/05/2025