Bispidine molecule (based on the 3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate unit) has been chosen as a rigid and versatile scaffold to build a series of highly tunable organic ligands for the production of a novel family of Coordination Polymers (CPs). The implemented design, based on extensive pre-existing knowledge in bispidine molecular complexes, featured the introduction of divergent pyridine moieties to allow the coordinative polymerization. In this thesis work it will be shown that the selected design indeed allows to produce highly crystalline CP materials combining bispidine with divalent metal ions such as Mn(II), Cu(II), Zn(II) and Hg(II). They consist most frequently in 1D CPs, but also to a lesser extent to 2D. In total, 31 novel SCs structures have been obtained, whose X-ray characterization constitutes an important part of this work. Depending on the solvent crystallization mixture used it was possible to obtain mono- and bi-solvated CPs. Single Crystal structural characterization has been reported for all the CPs collected, evidencing mostly the weak interactions that control the overall packing of each system. Among all the CPs reported, a series of 1D Mn(II)-ribbon like systems build upon pyridine-based bispidine ligands possessing a different substitution in N7 position, were studied in detail in terms of their adaptable and dynamic features aiming at the collection of novel potential adsorbent materials. The extensive structural analysis showed that this class of N7-bispidine-based CPs are composed by non-interpenetrated robust 1D ribbon-chains assembled via weak inter-ribbon interactions, resulting in different packing orientation, mainly depending on the ligand and solvent identities. Reproduced in form of microcrystalline powder samples, characterized by PXRD, Thermogravimetric Analysis (TGA), NMR spectroscopy and ab initio PXRD, these materials showed a remarkable highly dynamic behavior once subjected to heterogeneous solid/vapor and solid/liquid solvent adsorption and exchange reactions. Several solid-state reactions, comprising crystalline-to-crystalline, crystalline-to-amorphous-to-crystalline, single crystal-to-single crystal (SC-to-SC), selective adsorption transformations have been reported demonstrating the significant structural reorganization that 1D ribbon chains can undergo. We have also demonstrated that the dynamic tendency of CPs could be correlated to the aggregation modes and efficiency evidenced by the bispidine ligand alone in the solid-state. Combined structural and theoretical calculations based on SC-X-ray structure of each N7-bispidine ligand showed indeed the possibility to have qualitative indications on the dynamic properties of their corresponding CPs. Preliminary results allowed also to envisage a way to control on whether the ligand/metal assembly leads towards a CP or rather to a molecular complex, simply by choosing among different N7 substituents having varying steric and electronic attributes. Finally by combining both divergent and convergent coordination sites within the bispidine unit into a novel ligand design it was possible to obtain CP structures having an additional functional metal center, not involved in the coordinative polymerization, and thus potentially active for wider applicative purposes. Indeed, after several crystallization efforts, the first 1D HETERO bi-metallic bispidine-based CP has been obtained, thus opening the way towards a further widening of the fields of application of these bispidine-based CP materials into catalysis.
Questa tesi di dottorato riporta una nuova serie di Polimeri di Coordinazione sintetizzati a partire da derivati bispidinici funzionalizzati con piridine divergenti e fatti reagire con ioni metallici divalenti come Mn(II), Cu(II), Zn(II) e Hg(II) in presenza di vari solventi. In particolare sono state studiate le caratteristiche strutturali e le proprietà dinamiche di una serie di Polimeri di Coordinazione ottenuti dalla reazione tra MnCl2 e una nuova classe di ligandi bispidinici che presentano una diversa sostituzione sull’ azoto in posizione 7 dello scheletro biciclico. Tramite processi di cristallizzazione lenta e veloce è stato possibile ottenere nuovi materiali in forma di cristallo singolo e polvere microcristallina rispettivamente. L’ analisi strutturale condotta attraverso la diffrazione su cristallo singolo, ha mostrato la formazione di Polimeri di Coordinazione monodimensionali costituiti da catene lineari a forma di nastro; sono state inoltre evidenziate le differenze di packing per ogni sistema, correlandole alla chimica del ligando e al tipo di solvente intrappolato come guest. Dopo la caratterizzazione con diffrazione a raggi X su polveri, analisi termo gravimetrica e spettroscopia NMR, le polveri microcristalline sono state sottoposte ad esperimenti di scambio di guest e di assorbimento selettivo condotti in fase solido/liquido e solido/vapore, con lo scopo di studiare il comportamento dinamico di questi sistemi. L’ abilità di scambiare il loro guest e in alcuni casi di mostrare un comportamento di adsorbimento selettivo, ha dimostrato un’ elevata adattabilità strutturale da parte di questa nuova serie di Polimeri di Coordinazione. E’ stato anche possibile correlare tale comportamento dinamico con il modo di aggregazione che i ligandi da soli hanno allo stato solido, combinando studi strutturali e calcoli computazionali. Da studi preliminari è inoltre emerso che le proprietà steriche ed elettroniche del ligando bispidinico possono controllare la formazione o meno del polimero di coordinazione. Infine, ispirandosi al ruolo dei complessi molecolari bispidinici in catalisi omogenea, con un attento design del ligando, è stato possibile ottenere il primo polimero di coordinazione etero bimetallico. La presenza di un ulteriore sito metallico diverso da quello che guida la formazione dello scheletro polimerico, rappresenta un interessante attributo funzionale per potenziali utilizzi di questi nuovi materiali in catalisi eterogenea.
Design and synthesis of novel 1D bispidine-based coordination polymers for adsorption applications
Lippi, Martina
2020/2021
Abstract
Bispidine molecule (based on the 3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate unit) has been chosen as a rigid and versatile scaffold to build a series of highly tunable organic ligands for the production of a novel family of Coordination Polymers (CPs). The implemented design, based on extensive pre-existing knowledge in bispidine molecular complexes, featured the introduction of divergent pyridine moieties to allow the coordinative polymerization. In this thesis work it will be shown that the selected design indeed allows to produce highly crystalline CP materials combining bispidine with divalent metal ions such as Mn(II), Cu(II), Zn(II) and Hg(II). They consist most frequently in 1D CPs, but also to a lesser extent to 2D. In total, 31 novel SCs structures have been obtained, whose X-ray characterization constitutes an important part of this work. Depending on the solvent crystallization mixture used it was possible to obtain mono- and bi-solvated CPs. Single Crystal structural characterization has been reported for all the CPs collected, evidencing mostly the weak interactions that control the overall packing of each system. Among all the CPs reported, a series of 1D Mn(II)-ribbon like systems build upon pyridine-based bispidine ligands possessing a different substitution in N7 position, were studied in detail in terms of their adaptable and dynamic features aiming at the collection of novel potential adsorbent materials. The extensive structural analysis showed that this class of N7-bispidine-based CPs are composed by non-interpenetrated robust 1D ribbon-chains assembled via weak inter-ribbon interactions, resulting in different packing orientation, mainly depending on the ligand and solvent identities. Reproduced in form of microcrystalline powder samples, characterized by PXRD, Thermogravimetric Analysis (TGA), NMR spectroscopy and ab initio PXRD, these materials showed a remarkable highly dynamic behavior once subjected to heterogeneous solid/vapor and solid/liquid solvent adsorption and exchange reactions. Several solid-state reactions, comprising crystalline-to-crystalline, crystalline-to-amorphous-to-crystalline, single crystal-to-single crystal (SC-to-SC), selective adsorption transformations have been reported demonstrating the significant structural reorganization that 1D ribbon chains can undergo. We have also demonstrated that the dynamic tendency of CPs could be correlated to the aggregation modes and efficiency evidenced by the bispidine ligand alone in the solid-state. Combined structural and theoretical calculations based on SC-X-ray structure of each N7-bispidine ligand showed indeed the possibility to have qualitative indications on the dynamic properties of their corresponding CPs. Preliminary results allowed also to envisage a way to control on whether the ligand/metal assembly leads towards a CP or rather to a molecular complex, simply by choosing among different N7 substituents having varying steric and electronic attributes. Finally by combining both divergent and convergent coordination sites within the bispidine unit into a novel ligand design it was possible to obtain CP structures having an additional functional metal center, not involved in the coordinative polymerization, and thus potentially active for wider applicative purposes. Indeed, after several crystallization efforts, the first 1D HETERO bi-metallic bispidine-based CP has been obtained, thus opening the way towards a further widening of the fields of application of these bispidine-based CP materials into catalysis.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/171230