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  • Final Report Summary - NANOCOORD (Design, study and development of novel functional hybrid nanomaterials, which consist of a nanoparticle core and an unconventional shell of coordination entities with synergetic properties.)

Final Report Summary - NANOCOORD (Design, study and development of novel functional hybrid nanomaterials, which consist of a nanoparticle core and an unconventional shell of coordination entities with synergetic properties.)

In many strategic research areas, particularly in electronics and medicine, nanochemistry-based technologies have recently grown considerably owing to the specific properties of the nanoscale (e.g. room temperature superparamagnetism, quantum effects), which are hardly accessible by traditional chemical approaches. In this context, the consideration of coordination entities such as transition-metal complexes to implement nanoobjects is hitherto rather limited and remains to be investigated in a systematic way. The project Nanocoord intends to exploit the distinctive attributes of nanochemistry and coordination chemistry with the development of novel multifunctional nanomaterials based on the hybrid combination of coordination entities (CE) and a nano-template (NP) core with complementary properties. The decisive goal is to design original NP@CE materials as a promising alternative to highly competitive technological and socio-economic research challenges while contributing also to the state of the art in valuable emerging fields. Thus, the investigations of NP@CE heterostructures for the project have been purposely initially restricted to two primary targeted applications, i.e. (i) data storage where the principle consists in triggering and tailoring the magnetic bistability of spin crossover (SCO) derivatives through the external stimulation (magnetic field, light irradiation) of the nano-core, and (ii) biomedicine where the resolve notably refers to confine - within a single material - two distinct therapeutic agents (e.g. antibacterial and anticancer combination therapy) to enhance the looked-for curative effectiveness.
The assignment preliminary implied the development of a research activity in nanochemistry within the host institute from the scratch, including the suitable technical setup of a laboratory. Although this initial milestone has been mainly addressed during the 1st reporting period, continuous improvements had to be undertaken during the second reporting period, particularly with regard to the synthetic strategies and characterization protocols.
Furthermore, significant and valuable milestones have been attained during this project. The investigations have been initiated with the development of NP@CE heterostructures involving the grafting of triazole-based SCO systems such as [Fe(Rtrz)3][A]2·xH2O (Rtrz = 4-substituted-1,2,4-triazole, and A = monovalent anion) onto nano-templates, with the triazole-based coordination molecules currently widely recognized as arguably the most challenging and high applied potential systems since the SCO properties are often accompanied by thermochromism, piezochromism, and photochromism which can be utilized in the construction of multifunctional molecular devices. The principle consists in developing dual-switchable multiproperties nanomaterials, with the notable possibility to trigger and/or tailor the magnetic bistability of SCO derivatives (CE) through the external stimulation (e.g. magnetic field, light irradiation or pressure) of the nano-core (NP), and/or reciprocally. During the 2nd reporting period and in a logical sequence prior to the grafting step onto nano-templates, complexation reactions - involving original combinations of triazole-based ligands with Fe(II) salts and anions which were not used so far within the so-called ’triazole family’ derivatives - have been conducted via a flexible atypical synthetic approach with the focus to access the corresponding [Fe(Rtrz)3][A]2·xH2O SCO materials. In this ongoing work, we have realized at an early stage that this flexible synthetic strategy involving these unusual building blocks tends to improve unprecedentedly the size, the quality and the robustness of the single crystals of the resulting original FeII/Rtrz systems, with the current approach positioned as an alternative that tends to prevail over the implicit crystallogenesis issue in the FeII/Rtrz systems. Taking advantage of this newly designed synthetic route, we reported a new triazole based SCO FeII 1D polymer leading to the first robust single crystals of high quality and relatively considerable size that withstand a first-order spin transition with exceptional mechanical resilience upon repeated SCO switching cycles. The follow-up investigations lead us notably to (i) an original triazole-based SCO FeII neutral complex defined to our knowledge as the first example of trinuclear complex exhibiting an unprecedented complete one-step spin transition above room temperature (T1/2 ≈ 318 K), and (ii) in a logical continuance, to the first three dimensional SCO metal organic framework (MOF) based on functionalized triazole-ligand, which has been in addition characterized structurally in LS and HS states. The ‘breakthrough’ character of these results is positioned as cogent advance in the field impact of triazole based systems. Besides, among the main achievements from the project can be also cited the NP@CE heterostructures resulting from the grafting of FeII/Rtrz SCO systems onto stimuli-responsive organic polymers nano-templates. With an impact ‘beyond the state of the art’ in the field of stimuli-responsive polymers and hybrid materials, this work fruitfully leads us to novel water-soluble SCO thermoresponsive polymers with reversible switchable assembling/disassembling processes of the FeII/Rtrz complexes upon the thermoresponsive behaviour - displayed around room temperature - from the polymer nano-matrix. Moreover, the decision to alternatively substitute FeII/Rtrz systems with simpler SCO systems came to fruition as a new flexible and selective synthetic platform has been successfully developed to generate a variety of atypical heteroleptic [Fe(Rbpp)(R’bpp)][A]2 (Rbpp, R’bpp = substituted-2,6-di(pyrazolyl)-pyridine derivatives with R≠R’, and A = monovalent anion) SCO complexes, distinguishable from the homoleptic analogues by electrochemistry, and the ensuing access to NP@CE heterostructures. As for the notable biomedical outcomes of the project and the related NP@CE heterostructures, hydrophobic surfactant-coated ZnO NP have been incorporated into water-soluble hydrogel (HG) polymeric matrices to form original biocompatible ZnO@HG hydrogelnanocomposites. The antibacterial investigations - which comprise comparisons between surfactant-free ZnO NP, surfactant-coated ZnO NP, and ZnO@HG nanocomposites - undoubtedly demonstrated that ZnO NP can specifically display some versatile antibacterial activity against both Gram positive and Gram negative bacterial strains of clinical relevance such as Methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, and Pseudomonas aeruginosa. This systematic study breaks new ground in the rational identification of the structure-properties correlations and optimization of the biomedical activity. By virtue of their innovation, the development and understanding of all these results - particularly the NP@CE heterostructures - can be defined as direct contributions to ‘knowledge gaps’, and can have eventually a significant impact on the future development of functional nanomaterials within the EU. Indeed, they already paved the way to some ideas for collaborative extensions/ramifications beyond this project.
Due to the highly multidisciplinary character of the project, another critical milestone - efficiently tackled from the very beginning of the project and expanded all the way - referred to the establishment of a collaborative network with the solicitation of local, European and (inter)national partners, including an efficient transfer of knowledge and communication process. Thus, the project has allowed for the strict creation and a strengthening of those complementary collaboration dynamics with internationally recognized research groups, contributing by the same to initiatives for research integration at a European level. In addition, the active networking has provided access to expertise and high quality facilities not locally available. This international multidisciplinary network - built within this project - is anticipated to be maintained beyond, and ultimately greatly beneficial to the host institute and the fellow.
In Fine, the EC funding has been and will be of decisive importance for the career development of the fellow, on a short-term and long-term perspective. It has been particularly critical during the 2nd reporting period as it has allowed for the recruitment of a postdoctoral researcher (12 months).

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