Crystal Engineering and Structural Solutions of Organic Molecular Materials

Pugh, CJ
(2019) Crystal Engineering and Structural Solutions of Organic Molecular Materials. PhD thesis, University of Liverpool.

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Organic molecular materials have been studied for decades, with a strong focus on their application within gas uptake and selective separations. Porous organic molecules can come in multiple forms, whether a discrete molecule such as a macrocycle or cage, or an infinite framework, such as a hydrogen bonded organic framework (HOF). In this thesis, we will examine the benefits of crystal engineering as an alternative route towards the formation of new organic molecular structures. The molecular structures discussed in this thesis include organic molecular cages, hydrogen bonded organic frameworks and organic co-crystals. Crystal engineering has been posed as an impressive method for the discovery of new materials, without the time costly effort of finding alternative precursors, or finding the best possible reaction conditions. There are multiple routes towards recrystallisation, which are suitable whether soluble or insoluble, which can be utilised to direct alternative crystal packing, hence, alternative functionality. The dynamic nature of organic molecular cages, which are synthesised via reversible imine condensation reactions, is discussed in detail in chapter 2. TCC1[3+6], a trigonal prismatic cage underwent re-equilibration in solution to the truncated tetrahedron cage, stoichiometrically twice the equivalent, TCC1[6+12]. The cage formation was optimised synthetically, and furthermore experimental observations were rationalised through computational analyses. A series of organic molecular cages were synthesised via high throughput techniques using robotics, which were then fully characterised and their crystal structures determined. From this, a series of discoveries were made, including further illustration of re-equilibration in C21, from a [3+2] cage to a [6+4]. The formation of a new topology for C18 was also discovered, a bridged catenane with a novel topology not previously seen in literature. High throughput methods were also used in Chapter 4. However as opposed to the modelling the potential structure in silico, as in Chapter 3, the cages were chosen based on precursors capable of hydrogen bonding or organic salt formation. We showed it is possible to synthesised porous co-crystals from small organics, and furthermore discuss the benefits of using a bespoke high throughput infra-red kit, capable of determining the isosteric heat of adsorption. Porous structures by strategic design are also discussed in chapter 4, focusing on an alternative method using both crystal structure prediction (CSP) and energy-structure-function maps (ESFs) to increase the rate of porous material discovery. T1 and T2 are both triptycene-based hydrogen bonding tectons, which are capable of forming hydrogen-bonded organic frameworks. The ESFs enabled rationalisation of the experimental findings, and furthermore provided insight into the importance of hydrogen bond donors and acceptors through comparison of T1 and T2.

Item Type: Thesis (PhD)
Divisions: Faculty of Science and Engineering > School of Physical Sciences > Chemistry
Depositing User: Symplectic Admin
Date Deposited: 26 Mar 2019 12:22
Last Modified: 19 Jan 2023 01:04
DOI: 10.17638/03032463