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Poly- and oligo(ethylene glycol)s are known to suppress the adsorption of biological material on surfaces. In this thesis is shown that when using these chains in either monolayers or polymeric architectures, fouling (undesired growth of biological material on surfaces) could be significantly reduced. First the synthesis of oligo(propylene glycol)s (OPG) is reported. Hybrids of oligo(ethylene glycol)s and oligo(propylene glycol)s were also prepared. The conformational properties of two (chiral) OEG/PG hybrids are assessed with 1H-NMR, spectral simulations and ab initio calculations. Monolayers of alkyl end-functionalised oligo(ethylene glycol)/oligo(propylene glycol) hybrids on either Si(100) (CAMs) or Au(111) SAMs were used as model surfaces to gain insight into the protein resistivity mechanism of the OEG chains. All monolayers were characterised by IR, static contact angle measurements, ellipsometry and protein resistivity studies. The CAMs did not show the same level of protein resistivity as comparable monolayers on Au (111). The SAMs on Au (111) neither adsorb fibrinogen or lysozyme. This is tentatively attributed to differences in intermolecular packing density of the respective monolayers, which for the CAMs is dependant on the preparation procedure. The packing density of CAMs is decisively lower than that of the corresponding SAMs. For the SAMs also a effect of chirality is observed. The synthesis of typical oligo(ethylene glycol) functionalised copolymethacrylates is then presented. Both random and block copolymers were synthesised, using free radical polymerisation techniques. The block copolymers were obtained by making use of the reversible addition-fragmentation transfer (RAFT) polymerisation method using cumyl dithiobenzoate. The copolymers were characterised using of 1H- and 13C-NMR spectroscopy, size-exclusion chromatography (SEC), Differential Scanning Calorimetry (DSC) and IR spectroscopy. The assembly behaviour of a block copolymer in aqueous solution was investigated using a fluorescence probe technique, light scattering and cryo-TEM experiments. After deposition of the random and block copolymers on either hydrophilic or hydrophobic Si (100) surfaces, their surface topology and morphology was studied using tapping-mode AFM. Biofilm formation on the copolymers was studied by following the growth of bacteria and diatoms and the production of (EPS) in time using CLSM. The results demonstrated that the coatings suppress deposition of the amount of biological material by almost 60%. Especially the block copolymer was found to possess the best antifouling properties; as a consequence of its assembly behaviour. It is concluded that the random and block copolymers of proper composition represent viable binder materials for the preparation of new benign anti-fouling coating systems. The adhesive properties of some typical oligo(ethylene glycol) containing polymethacrylates on a commercial primer (SigmaPrime) deposited on a steel substrate were evaluated for their use in long-term antifouling studies. It was found that the random copolymers adhered well to the SigmaPrime. The block copolymer gave a free-standing film during exposure to water. The ultimate test, application of our polymer materials on a ship’s hull, is still a future prospect, but the concept proved to be valuable as an alternative for the banned tributyl tin containing coating.

In this thesis, ion stability, ion-molecule reactions and reaction rates are studied using mass spectrometry and molecular modelling. In Chapter 2 the effect of functional group substitution on neutral and ionised ketene are studied. Electron-donating substituents show a stabilising positive induction effect on the ketene ion, while electron acceptor substituents destabilise it by a negative induction effect. There exists also resonance stabilisation of the product ion, caused by electron donation from the substituent to the product ion. This stabilisation is in some cases so strong that the existence of a covalently bound substituted ketene ion is not possible. The stabilisation effects on proton-bound complexes are studied in Chapter 3. An existing linear correlation method to estimate the stability of the formed complexes is extended by inclusion of a dipole moment factor in the method. This improves the accuracy of the stability estimates in general for a range of complexes. Especially in many cases where there is a strong ion-dipole interaction contributing to the stability of the complex, the estimations are improved. Chapter 4 focuses on the dissociation reactions of protonated oxalic acid. It is found from computations that the lowest-energy reaction proceeds to the dissociation into protonated water, carbon monoxide, and carbon dioxide. This happens via a unique ter-body complex. This ter-body complex is also argumented to be the reason for the main peak in a metastable ion mass spectrum of protonated oxalic acid. Reaction paths of the minor dissociation products were also obtained. The possibility of pyrimidine formation in interstellar dust clouds from an acrylonitrile radical cation dimer is discussed in Chapter 5. Metastable ion mass spectrometric experiments on acrylonitrile exhibit a small amount of pyrimidine formation, which results from a covalently bound adduct cation of neutral and ionized acrylonitrile. From experimental and computational studies this is found to be only a minor product, while the major product is self-protonation via proton-bound complexes. A related reaction of acrylonitrile with hydrogen cyanide is studied in Chapter 6 using solely computations. Pyrimidine formation is deemed possible, in terms of energy, although kinetic studies show the adduct formation to be very slow in comparison to proton-transport catalysis reactions. The latter reactions are identified as the most favourable reactions. Protonated hydrogen cyanide formation is found to be a possible minor process as well. Chapter 7 is focused on qualitative studies using semi-classical trajectory calculations on the dissociation rate of an ion-dipole complex with a deep potential well preceding the dissociation. To reduce required computational time, a qualitative interpolation method is developed to predict the behaviour of trajectories in cases where many vibrational modes are excited. It is shown that, on average, only one-tenth of the channels open to dissociation lead directly to dissociation products for moderate excess energies (less than 10 kcal mol-1). The rest of the open channels lead either to a very slowly progressing dissociation, or to semi-periodic behaviour of the trajectory.

This paper describes the rheological effects observed after addition of (natural) polyols to several different types of heavy metal-free PVC formulations. It is found that addition of natural polyols, such as sorbitol, leads to changes in the rheology of the system comparable to the addition of external lubricants. Hence as suggested previously, addition of (natural) polyols may lead to the occurrence of undesirable plate-out phenomena. The magnitude of the effect on the rheology depends on the number of hydroxyl groups in the polyol and its propensity to undergo intramolecular cyclodehydration reactions. It is established that the undesirable rheological effects, which coincide with plate-out phenomena, can be suppressed by the addition of various types of inorganic as well as organic substances, most of which are known PVC additives. This will allow for the use of (natural) polyols as efficient and benign co-stabilisers in next generation stabiliser systems.

The B3LYP/DZP++ adiabatic electron affinity (AEA) of nine (non)-alternant polycyclic aromatic hydrocarbons are reported and discussed. Calculations became feasible for molecules this size by projecting out the near-linearly dependent part of the one-electron basis. Non-alternant PAH consisting of an alternant PAH core modified by peri-annulation with unsaturated five-membered rings (CP-PAHs) possess markedly enhanced AEAs.

The structure of the cross-conjugated compound 2,3-diphenylbutadiene was investigated by single-crystal X-ray diffraction and computational methods. In the crystal structure the central butadiene fragment adopts an s-gauche geometry [-55.6(2)° torsion angle φ around the essential single bond], whereas the styrene moieties are close to planarity. MP2/6-311G* calculations show that the s-gauche conformation represents the global minimum along the φ coordinate, but also revealed the existence of an s-trans local minimum. While the crystal structure seems to reflect dominance of styrene- like conjugation, the MP2/6-311G* calculations indicate that conjugation in both the styrene and butadiene π- systems is important. An NBO orbital deletion study shows that the structure is primarily determined by (hyper)conjugation and that steric effects play a minor role.

Calculations on members of the oligo(cyclohexylidene) series [1(n), n = 1-5)] and related tetrahydro-4H-thiopyran end-capped analogues [2(n), n = 1-4)] show a strong through-bond coupling between their π bonds and sulfur lone pairs (LpπS). This coupling is mediated by an interaction between the H(ax)-C-C-H(ax) structural sub-units and the π bonds connecting the cyclohexyl moieties. A comparison of the length dependency of the through-bond coupling via an oligo(cyclohexylidene) and an alkane bridge [divinyl alkanes 3(n)] shows that oligo(cyclohexylidenes) are more efficient in mediating through-bond couplings over large distances. Oligo(cyclohexylidene) bridges exhibit molecular wire characteristics

The 12π cation (3) and 14π anion (4) derived from the phenalenyl radical (2) support diatropic ("aromatic") perimeter ring currents, but isoelectronic replacement of the central atom by either boron (5) or nitrogen (6) leads to paratropic ("antiaromatic") current; the ipsocentric approach to molecular magnetic response accounts for all four patterns in terms of competition between translationally and rotationally allowed virtual π-π* excitations.

Calculation and visualisation of induced current density are important aids to the study of both aromaticity and observable molecular magnetic response properties. The ipsocentric method offers an accurate and economical approach to calculation of induced current density, and a physical interpretation in terms of occupied-orbital contributions. In monocyclic systems, these contributions allow rationalisation of the existence, sense, and strength of ring current using simple symmetry and node-counting arguments. Here we show maps computed with the model pseudo-π version of the ipsocentric theory for large polycyclic aromatic hydrocarbons (PAH) of the Clar type. Maps are presented for D6h- symmetric systems with up to 438 carbon centres; a full ab initio calculation for an isomer of C114H30 confirms that the success of the pseudo-π method for small PAH carries over to these larger systems. The computed maps follow a generic overall pattern that can be understood with a natural extension of the orbital arguments to a ‘band theory’ of totally resonant PAH. All show π current densities that combine a Clar-sextet structure of localised benzenoid diatropic ring currents (contributed by just four HOMO electrons) with a global perimeter diatropic ring current contributed by the remaining π electrons. Both currents are explained in the ipsocentric model: the localised currents arise from excitations from the HOMO; the perimeter current from excitations from the rest of the HOMO-band.

The synthesis of a topologically new type of dendrimer is presented in which a permanently positively charged core is decorated with a shell that is apolar and aliphatic in nature. The novel polyionic dendrimers were successfully applied as hosts for a predefined number of anionic guests, as is shown for the dye methyl orange. The aliphatic periphery of the dendrimers efficiently shields the ion pairs and renders the dendrimers fully soluble in organic solvents that are as apolar as hexane and, furthermore, provides them with an interesting phase behavior that appears not to be sensitive to the type of anion associated with it.

A series of novel 4,4'-disubstituted organic-organometallic stilbenes were synthesized, that is, the 4'-substituted stilbenoid- NCN-pincer platinum(II) complexes [PtCl(NCN-R-4)] (NCN-R-4 = [C6H2(CH2NMe2)2-2,6-R-4]- in which R = C2H2C6H4-R'-4' with R' = NMe2, OMe, SiMe3, H, I, CN, NO2) (1-7). In these compounds the PtCl grouping can be considered to be present as a donor substituent. Their synthesis involved a Horner-Wadsworth-Emmons reaction of [PtCl(NCN-CHO-4)] (9) with the appropriate phosphonate ester derivatives (8a-g). Under these reaction conditions, the C-Pt bond in aldehyde 9 was not affected, and the platinated stilbene products were obtained in 53-90% yield. The solidstate structures of complexes 1, 2 and 5-7 were determined by single-crystal X-ray diffraction, which revealed interesting bent conformations for 2, 5 and 7. Linear correlations were found between both the 13C{1H} (C ipso to Pt) and the 195Pt{1H} NMR chemical shift and the Hammett σp value of the R' substituent; therefore, these NMR shifts can be used as a qualitative probe for the electronic properties of the delocalized π-system to which it is connected. The platinum-stilbene complexes were investigated for charge-transfer properties in solvents of different polarity. The luminescent properties, shown by donor-acceptor complexes 1, 6 and 7, were investigated by fluorescence spectroscopy, and the complexes showed positive solvatochromism, which indicates dipolar character of the excited state. The excited state lifetimes, which were in the picosecond range, and the quantum yields (ranging from 0.002 to 0.2) were also determined for these complexes. It was established that the presence of the transition metal favours nonradiative decay from the excited state to the ground state.

ECE-pincer palladium(II) complexes {ECE=[C6H3(CH2E)2-2,6]-, E=PPh2 and SPh} thered to a trialkoxysilane moiety through a carbamate linkage were immobilized on ordered mesoporous silicas SBA-15 and MCM-41 using a grafting process. The resulting hybrid materials were characterized by IR spectroscopy, solid-state CP/MAS NMR (13C, 31P, and 29Si), and elemental analyses. These analyses showed the integrity of the pincer-metal complexes on the supports, which highlights their stability under the applied immobilization conditions. An H-bonding interaction between the carbamate carbonyl group of the complex and free silanol groups on the silica surface was also established. The hybrid materials were found to act as Lewis acid catalysts in the aldol reaction between methyl isocyanoacetate and benzaldehyde. SBA-15 modified with the PCP-pincer Pd complex was used in up to five runs without loss of activity. Control experiments showed the true heterogeneous nature of the catalyst in this reaction. Nitrogen physisorption data, XRD, and TEM/EDX analyses of the hybrid materials revealed that the mesoporous structure of these materials was retained during the immobilization process as well as during catalysis.

Complete ¹H and ¹³HC NMR assignments of the (di-)cyclopenta-fused pyrene congeners, cyclopenta[cd]- (2), dicyclopenta[cd,fg]- (3), dicyclopenta[cd,jk]- (4) and dicyclopenta[cd,mn]pyrene (5), respectively, are archieved using two-dimensional (2D) NMR spectroscopy. The experimental ¹³C chemical shift assignments are compared with computed ab initio CTOCD-PZ2/6-31G** ¹³C chemical shifts; a satisfactory agreement is found. Substituent-induced chemical shifts in the pyrene core induced by annelation of cyclopenta moieties are discussed. Effects of dicyclopenta topology on electric structure are illustrated for 3-5.

Ab initio valence bond (VB) calculations give direct evidence for the stabilistaion and closed-shell character formation of formal diradicals by neighbouring group interactions. By allowing the singly occupied p-orbitals to delocalise during the orbital optimisation, neighbouring group effects are implicitly included in the wavefunction. By constraining the orbitals in the wavefunction to remain strictly atomic, through-bond effects are excluded from the wavefunction. These effects can then be included in the wavefunction by expanding the wavefunction using more valence bond structures. The choice of these structures used to built the wavefunction determines which interactions will be accounted for. For the compounds considered here, 2,4-dioxo-1,3-cyclobutanediyl (1), 2,4-bis(methylene)-1,3-cyclobutanediyl (2), 1,3-cyclobutanediyl (3), and 1,1,3,3-tetrahydro-1,3,2,4-diphosphadiboretane-1,3-diyl (4), the calculations show that the most important VB structures for mediating interactions between the opposing radical centres are those that withdraw electrons from the ring, thereby creating an aromatic, 2pi-electron four-membered ring. For the 1,3-cyclobutanediyl analogues (3 and 4), the PH2 group functions similar to the C=O group, and is a better electron-accepting substituent than the CH2 group. The energy differences between the strictly atomic and delocal orbital optimisation models show that the molecules with less diradical character are stabilised more by through-bond orbital interactions.

Surprisingly, the anti-aromatic paratropic ring current of the planar D4h transition state of 1,3,5,7-cyclooctatetraene (COT) survives almost all the way to the equilibrium tub-shaped D2d COT structure (plane-to-plane distance, d = 0.76 A); the current vanishes at ca. 80% of the geometric change and ca. 90% of the energy change from planar to tub geometry.

An extension of the CEPA1 method to the multi-reference case is presented, the MR-CEPA1 approach. The method takes the variationally included terms into account as in MRDCEPA and corrects for the exclusion principle violating terms as in closed shell CEPA1. It is shown that this method yields potential energy curves that are close to those of the multi-reference coupled cluster method and parallel the full CI results quite well. The size consistency of the method is as good as the MRDCEPA method and much beter than approaches that ignore the VI terms like MR-ACPF and MR-AQCC. A simpler method, where the EPV terms are not corrected on an individual basis for the doubly occupied orbitals, dubbed the multi-reference averages CEPA1 method (MR-ACEPA), which is akin to methods previously suggested by Szalay et al., is comparable in performance.

To probe the effect of external cyclopenta-fusion on a naphthalene core, ab initio valence bond (VB) calculations have been performed, using strictly atomic benzene p-orbitals and p-orbitals that are allowed to delocalize, on naphthalene (1), acenaphthylene (2), pyracylene (3), cyclopenta[b,c]-acenaphthylene (4), fluoranthene (5), and cyclopenta[c,d]fluoranthene (6). For the related compounds 1-4 and 5,6 the total resonance energies (according to Pauling's definition) are similar. Partitioning of the total resonance energy in contributions from the possible 4n+2 and 4n pi-electron conjugated circuits shows that only the 6 pi-electron conjugated circuits (benzene-like) contribute to the resonance energy. The results show that cyclopenta-fusion does not extend the pi system in the ground state; the five-membered rings act as peri-substituents. As a consequence, the differences in (total) resonance energy do not coincide with the differences in thermodynamic stability. Notwihstanding, the relative energies of the Kekule structures can be estimated using Randic's conjugated circuits model.

Valence bond (VB) theory and ring-current maps have been used to study the electronic structure of inorganic benzene analogues X6H6 (X = C (1), Si (2)), X6 (X = N (3), P (4)), X3Y3H6 (X,Y = B,N (5), B,P (6), Al,N (7), Al,P (8)), and B3Y3H3 (Y = O (9), S (10)). It is shown that the homonuclear compounds possess benzene-like character, with resonance between two Kekule-like structures and induced diatropic ring currents. Heteronuclear compounds typically show localization of the lone pairs on the electronegative atoms; Kekule-like structures do not contribute. Of the heteronuclear compounds, only B3P3H6 (6) has some benzene-like features with a significant contribution of two Kekule-like structures to its VB wave function, an appreciable resonance energy, and a discernible diatropic ring current in planar geometry. However, relaxation of 6 to the optimal nonplanar chair conformation is accompanied by the onset of localization of the ring current.