Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The first part of this study describes the synthesis of new porous materials from basic building
blocks. Five structurally related ligands namely: N,N'-bis(3-pyridylmethyl)-naphthalene diimide
(L1), N,N'-bis(4-pyridylmethyl)-naphthalene diimide (L2), N,N'-bis(4-pyridylmethyl)-
pyromellitic diimide (L3), N,N'-bis(3-pyridylmethyl)-pyromellitic diimide (L4) and 2-(pyridin-4-
ylmethyl)-benzene tricarboxylic anhydride (L5) were synthesised. Ligands L1 and L2 were
reacted with metal nitrates and carboxylates as co-ligands in a systematic manner with a view to
obtaining potentially porous 3–D coordination polymers. Ten structurally diverse coordination
polymers were obtained and they were characterised by single-crystal X-ray diffraction, powder
X-ray diffraction and thermogravimetric analysis. Four of these compounds absorb moderate
amounts of CO2 and, in addition, show sorption selectivity towards CO2 over N2. The reaction of
L3 and L4 with transition metal halides yielded two 1–D chains, while the reaction of L5 with
transition metal nitrates yielded seven coordination polymers of which four are 2–D and three are
1–D. Of the 2–D structures three are isostructural.
The second part of this work describes a variable pressure study of a flexible metal-organic
framework [Zn2(BDC)2(BPY)] (BPY = 4,4 -bipyridine and BDC = 1,4-benzene dicarboxylic
acid). [Zn2(BDC)2(BPY)] is one of the few examples of a flexible metal-organic framework that
undergoes phase transformations in response to gas pressure. The high pressure sorption
recorded for this metal-organic framework displays two inflection steps in the pressure range 0 to
30 bar, possibly indicating two phase transformations. The gas-loaded structures for each phase
transformation were determined by means of single-crystal X-ray diffraction. High-pressure
differential scanning calorimetry was also carried out on the system in order to determine
accurate gate-opening pressures, as well as the energies involved with each phase transformation.
The results correlate with those obtained from single-crystal X-ray diffraction and high-pressure
sorption.
The final section reports the mechanochemical synthesis of two Werner complexes [NiCl2(4-
PhPy)4] (1), [CoCl2(4-PhPy)4] (2) and their corresponding solid solution [Ni0.5Co0.5Cl2(4-PhPy)4]
(3) (PhPy = phenyl pyridine). The solid solution could only be formed by mechanochemical
synthesis and not by conventional solution crystallisation methods. The solid solution exhibits
sorption properties that differ from those of the pure compounds. / AFRIKAANSE OPSOMMING: Die eerste deel van hierdie studie beskryf die sintese van nuwe poreuse stowwe uit basiese
boublokke. Vyf struktureel verwante ligande naamlik: N,N'-bis(3-piridielmetiel)-naftaleen
diimied (L1), N,N'-bis(4-piridielmetiel)-naftaleen diimied (L2), N,N'-bis(4-piridielmetiel)-
piromellitien diimied (L3), N,N'-bis(3-piridielmetiel)-piromellitien diimied (L4) en 2-(piridiel-4-
ielmetiel)benseen trianhidried (L5) is gesintetiseer. Ligande L1 en L2 is gereageer met metaal
nitrate en karboksielsure as mede-ligande in 'n sistematiese wyse met 'n oog op die verkryging
van potensieel poreuse 3–D koördinasie polimere. Tien struktureel diverse koördinasie polimere
is verkry en hulle is gekarakteriseer deur enkel-kristal X-straal-diffraksie, poeier X-straal
diffraksie en termo-analise (thermal analysis). Vier van hierdie verbindings het matige
hoeveelhede CO2 geabsorbeer en, bykomend, wys sorpsie selektiwiteit van CO2 oor N2. Die
reaksie van L3 en L4 met oorgangsmetaalhaliede het twee 1–D kettings gevorm, terwyl die
reaksie van L5 met oorgangsmetaal nitrate sewe koördinasie polimere opgelewer het, waarvan
vier 2–D en drie 1–D polimere is. Van die 2–D polimere het drie vergelykbare strukture.
Die tweede deel van hierdie werk beskryf 'n veranderlike druk studie van 'n buigsame metaalorganiese
raamwerk [Zn2(BDC)2(BPY)] (BPY = 4,4-bipiridien en BDC = 1,4-benseen
dikarboksielsuur). [Zn2(BDC)2(BPY)] is een van die min voorbeelde van 'n buigsame metaalorganiese
raamwerk wat fase transformasies (phase transformations) ondergaan in respons op ‘n
verandering in gas druk. Die hoë-druk sorpsie aangeteken vir hierdie metaal-organiese raamwerk
vertoon twee infleksie stappe in die gebestudeerde druk gebied (0 tot 30 bar), wat moontlik op
twee fase transformasies dui. Die gas-gelaaide strukture vir elke fase transformasie is bepaal deur
middel van enkel-kristal X-straal-diffraksie. Hoë-druk differensiële skandeer kalorimetrie
(differential scanning calorimetry) is ook uitgevoer op die stelsel ten einde dié akkurate hekopenings
druk, sowel as die energie betrokke by elke fase transformasie te bepaal. Die resultate
stem ooreen met dié verkry vanaf enkel-kristal X-straal diffraksie en hoë-druk sorpsie.
Die finale afdeling bespreek die meganochemiese sintese van twee Werner komplekse
[NiCl2(4-PhPy)4] (1) en [COCl2(4-PhPy)4] (2) en hul ooreenstemmende vaste oplossing (solid
solution) [Ni0.5Co0.5Cl2(4-PhPy)4] (3). Die vaste oplossing kan slegs gevorm word deur
meganochemiese sintese en nie deur konvensionele oplossing kristallisasie metodes. Die vaste
oplossing vertoon sorpsie eienskappe wat verskil van dié van die suiwer verbindings.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/79803 |
| Date | 03 1900 |
| Creators | Batisai, Eustina |
| Contributors | Barbour, L. J., Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xii, 135 pages : illustrations (some colour) |
| Rights | Stellenbosch University |
Page generated in 0.0027 seconds