The research carried out during this PhD project and reported in this Thesis is focused on the design, preparation and characterization of multi-component supramolecular 3D architectures obtained by appropriate paneling multitopic pyridyl ligands with flat Zn-porphyrin metallacycles. The versatility of the synthetic approach pursued, allowed to efficiently construct libraries of elaborated 3D structures, tuning the shape and dimension of the target systems, modulating the inter-component photo-induced properties and/or introducing new functions deriving from the geometrical organization of a precise number of active metal centers, by cleverly tailoring the molecular building blocks. In Chapter 1, a general introduction on key role of porphyrins as functional and structural building unit for the assembly of artificial discrete supramolecular structures is presented, together with the main designing concepts of the metal mediated self-assembling synthetic strategy. Few examples of elegant multiporphyrin architectures and their application are reported. Finally, the modular synthetic approach pursued during this research project is described. In Chapter 2, a thourough investigation on the possibility to produce new hetero-multimetallic ordered discrete structures, by self-assembling of a zinc-porphyrin metallacycle (1Zn) with dipyridyl clathrochelate metalloligands (provided by the group of Prof. K. Severin, EPFL, Lausanne, CH), is discussed. In particular, linear FeII metal containing ligands with terminal 4-pyridyl groups, lengthes between 1.5 and 3.2 nm, and containing either one or two clatrochelate cores were chosen. The final aim is the easy access, by a modular approach, to higher order functional systems comprising defined numbers and spacial organizations of metal-active centers (e.g. magnetically, redox or catalytically active). Chapter 3 reports on the metal mediated assembling of a linear dipyridyl diazadioxa[8]circulene (Circ, provided by the group of Prof. M. Pittelkow, University of Copenhagen, DK) with either 1Zn and of a cis-protected diphosphines PtII complex. Circ is a flat and conjugated compound presenting a central antiaromatic cyclooctatetraene core. The designing idea was to endow the ligand in structures, enforcing conformations which could enable, to find experimental evidences of the antiaromaticity, by observation of deshielding effect due to the diatropic ring current of the COT core. Discussion of their structural analysis in solution and in the solid state is described. The work described in Chapter 4 focused on the synthesis of giant 3D discrete supramolecular architectures, with tuned dimensions, geometry and varied number of porphyrin units, obtained by simple mixing different (metallo)porphyrin modules. By appropriate tailoring of the meso-4’pyridylporphyrin connectors, i.e. increasing the number of basic donor sites and/or playing on their relative disposition, larger molecular architectures become easily available. Cleverly designed molecular building units, in terms of lability/inertness and hard/soft metal-to-ligand discriminations, quantitatively self-connect by formation of mutual coordination bonds. The obtained discrete multi-porphyrin structures constitute a spatially-ordered lattice of chromophores featuring photoinduced antenna-effect and charge transfer processes. Pursuing a modular synthetic approach, a library of fascinating In Chapter 5, Is reported the work performed during a six-month internship in the laboratories of Dr. Romain Ruppert, University of Strasbourg (FR), is devoted at investigating and tackling the possibility to employ a PdII-linked Zn(II)-porphyrin dimer (ZnPdZn), as alternative photo-active platforms for the assembling of discrete supramolecular sandwich structures.

il progetto di ricerca descritto nel presente lavoro di tesi si è focalizzato sulla progettazione, sintesi e caratterizzazione di strutture 3D supramolecolari ottenute mediante appropriata combinazione di leganti piridinici con pannelli metallaciclici di zinco porfirine. La versatilità dell'approccio sintetico perseguito, ha permesso, a seguto di un astuto e pensato design delle unità di base molecolari, di ottenere efficientemente una libreria di elaborate strutture supramolecolari tridimensionali, di modulabile forma e dimensione del sistema desiderato, regolandone le proprieta fotoindotti inter-componente e/o introducendo nuove funzionalità derivanti dall'organizzazione geometrica di un preciso numero di centri metallici attivi. Parte del lavoro è stato dedicato ad una approfondita investigazione sulla possibilità di ottenere strutture eterometalliche di ordine discreto, mediante autoassemblaggio di un metallaciclo di zinco porfirine in combinazione con appropriati leganti clatrochelati piridinici, tramite una collaborazionecon il gruppo di Prof. K. Severin (EPFL di Losanna). Lo scopo finale è di ottenere facilmente, mediante un approccio sintetico modulare, sistemi funzionali di ordine superiore contenenti un definito numero di ben organizzati centri metallici attivi (cioè magneticamente, cataliticamente o redox attivi). Ci si è inoltre concentrati sulla sintesi di architetture supramolecolari discrete aventi dimensioni e geometria modulabile e recanti un numero variabile di unità porfiriniche, ottenute per semplice mescolamento di due o tre diversi moduli porfirinici. Scegliendo in modo appropriato i connettori piridinici, cioè variandone il numero di centri basici donatori e/o giocando sulla loro posizione relativa, strutture molecolari di dimensioni implememntate diventano facilmente ottenibili. Progettando in modo studiato le unità molecolari di base, in termini di lablità/inerzia e discriminazione di tipo hard/soft, queste si autoassembleranno a formare in modo quantitativo tramite la formazione di legami di coordinazione complementari. Le strutture multi-porfiriniche così ottenute costituiscono un telaio ben ordinato di unità cromoforiche coinvolti in processi fotoindotti di trasferimento di energia e di trasferimento di carica. Infine parte del lavoro di ricerca è stato svolto durante un periodo di 6 mesi trascorsi presso il laboratorio del Dr. Romain Ruppert dell’Università di Strasburgo. Il progetto aveva lo scopo di sintetizzare dei dimeri di zinco porfirine connesse mediante coordinazione a un catione di Pd(II), e di studiare la loro possibile applicazione ed utilizzo come piattaforme fotoattive alternative per l’autoassemblaggio di sistemi discreti suprmaolecolari a forma di sandwich. Da un punto di vista fotofisico il nuovo dimero presenta interessanti proprietà in quanto è presente una forte comunicazione elettroinica fra le due porfirne attraverso il ponte metallico di Pd(II). D’altro canto, da un punto di vista di sintesi supramolecolare, il dimero presenta le caratteristiche richieste: due punti di ancoraggio costituiti dai due centri di Zn(II), un buon grado di inerzia del legame esociclico e una sufficiente coplanarità a disposizione rigida delle componenti.

Zn(II)-porphyrin metallacyles: versatile building units for the self-assembling of discrete 3D multi-component systems with tunable geometries and properties / Amati, Agnese. - (2019 Mar 08).

Zn(II)-porphyrin metallacyles: versatile building units for the self-assembling of discrete 3D multi-component systems with tunable geometries and properties

AMATI, AGNESE
2019-03-08

Abstract

The research carried out during this PhD project and reported in this Thesis is focused on the design, preparation and characterization of multi-component supramolecular 3D architectures obtained by appropriate paneling multitopic pyridyl ligands with flat Zn-porphyrin metallacycles. The versatility of the synthetic approach pursued, allowed to efficiently construct libraries of elaborated 3D structures, tuning the shape and dimension of the target systems, modulating the inter-component photo-induced properties and/or introducing new functions deriving from the geometrical organization of a precise number of active metal centers, by cleverly tailoring the molecular building blocks. In Chapter 1, a general introduction on key role of porphyrins as functional and structural building unit for the assembly of artificial discrete supramolecular structures is presented, together with the main designing concepts of the metal mediated self-assembling synthetic strategy. Few examples of elegant multiporphyrin architectures and their application are reported. Finally, the modular synthetic approach pursued during this research project is described. In Chapter 2, a thourough investigation on the possibility to produce new hetero-multimetallic ordered discrete structures, by self-assembling of a zinc-porphyrin metallacycle (1Zn) with dipyridyl clathrochelate metalloligands (provided by the group of Prof. K. Severin, EPFL, Lausanne, CH), is discussed. In particular, linear FeII metal containing ligands with terminal 4-pyridyl groups, lengthes between 1.5 and 3.2 nm, and containing either one or two clatrochelate cores were chosen. The final aim is the easy access, by a modular approach, to higher order functional systems comprising defined numbers and spacial organizations of metal-active centers (e.g. magnetically, redox or catalytically active). Chapter 3 reports on the metal mediated assembling of a linear dipyridyl diazadioxa[8]circulene (Circ, provided by the group of Prof. M. Pittelkow, University of Copenhagen, DK) with either 1Zn and of a cis-protected diphosphines PtII complex. Circ is a flat and conjugated compound presenting a central antiaromatic cyclooctatetraene core. The designing idea was to endow the ligand in structures, enforcing conformations which could enable, to find experimental evidences of the antiaromaticity, by observation of deshielding effect due to the diatropic ring current of the COT core. Discussion of their structural analysis in solution and in the solid state is described. The work described in Chapter 4 focused on the synthesis of giant 3D discrete supramolecular architectures, with tuned dimensions, geometry and varied number of porphyrin units, obtained by simple mixing different (metallo)porphyrin modules. By appropriate tailoring of the meso-4’pyridylporphyrin connectors, i.e. increasing the number of basic donor sites and/or playing on their relative disposition, larger molecular architectures become easily available. Cleverly designed molecular building units, in terms of lability/inertness and hard/soft metal-to-ligand discriminations, quantitatively self-connect by formation of mutual coordination bonds. The obtained discrete multi-porphyrin structures constitute a spatially-ordered lattice of chromophores featuring photoinduced antenna-effect and charge transfer processes. Pursuing a modular synthetic approach, a library of fascinating In Chapter 5, Is reported the work performed during a six-month internship in the laboratories of Dr. Romain Ruppert, University of Strasbourg (FR), is devoted at investigating and tackling the possibility to employ a PdII-linked Zn(II)-porphyrin dimer (ZnPdZn), as alternative photo-active platforms for the assembling of discrete supramolecular sandwich structures.
8-mar-2019
IENGO, ELISABETTA
31
2017/2018
Settore CHIM/03 - Chimica Generale e Inorganica
Università degli Studi di Trieste
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/2957166
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