Aplicación de la Gestión de los suministros en la hotelería

Scheme 2. Synthesis of Pd SCS pincer functionalised PAA, 2.09 and non Pd functionalised SCS pincer PAA, 2.10

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Polymerisation of tbutyl acrylate, 2.06

Figure 30.1H NMR spectrum for 2.06 in CDCl3. Butylated hydroxyltoluene (BHT)

is a stabiliser added to THF. Note: the last step in the polymer synthesis is removal of THF under vacuum, consequently BHT appears throughout the synthesis until it is

removed in the last step by dialysis. BHT peaks appear at 6.98, 5.0, 2.27 and 1.43 ppm.

Polymerisation of tbutyl acrylate (tBuA) at 65 °C in dioxane, followed by precipitation into MeOH:H2O 9:1 v/v resulted in a well-defined PtBuA

homopolymer with high end group fidelity. Figure 30 shows the 1H NMR spectrum for 2.06, the peaks for the pincer end group (Hg, Hh, Hi and Hj) and the RAFT end

group (Hf) integrated well with respect to each other, indicating good end group

fidelity. This is backed up by an overlay of the differential refractive index (DRI) and UV (at 309 nm) trace form SEC analysis of the polymer. As shown in

Figure 29, the trithiocarbonate group absorbs strongly at 309 nm and therefore overlaying this with the DRI trace indicates that the trithiocarbonate end group is present throughout the molecular weight distribution of polymer chains.

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Figure 31. SEC traces using DRI (red) and UV (at 309 nm) (blue) detectors for the

2.06 in THF.

SEC was performed in tetrahydrofuran (THF), and calibrated against narrow poly(methyl methacrylate) standards (PMMA). Analysis gave Mn = 8.1 kDa and Ð =

1.07. End group analysis by 1H NMR spectroscopy gives DP = 50.

End group removal of PtBuA, 2.07

It has been previously shown that the trithiocarbonate group is a competitive binder to palladium and therefore it is necessary to remove it prior to complexation of the pincer ligand.45 This was achieved by heating the polymer to 100 °C for ca. 12 hours in the presence of AIBN and ethylpiperidine hypophosphite (EPHP).46 End group removal could be seen in both the 1H NMR spectrum and by SEC analysis.

Figure 32 shows the 1H NMR spectrum for 2.07, complete disappearance of the peak Hf can be seen while the peaks Hh, Hi and Hj still integrate well with respect to

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Figure 32. 1H NMR spectrum for 2.07 in CDCl3.

A comparison of the UV309 traces before and after end group removal (normalised with respect to the DRI traces to account for concentration differences in the samples) shows complete end group removal of the trithiocarbonate group.

Figure 33. SEC traces using a UV detector for (at 309 nm) 2.06 (red) and 2.07

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Complexation of PtBuA, 2.08

Figure 34. crude 1H NMR spectrum for 2.08 in CDCl3.

Polymer 2.07, was then stirred in acetonitrile under N2 (g) and at room temperature

with the palladium precursor complex, [Pd(NCMe)4]2[BF4], for two days. Removal

of the acetonitrile in vacuo resulted in an orange solid which was used without further purification. The crude 1H NMR spectrum shows complete disappearance of the aromatic proton (Hj) where Pd insertion has taken place. The spectrum also

shows a shift and broadening for the methylene bridge protons (Hg) on complexation

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Deprotection of PtBuA to form PAA-Pd, 2.09

Figure 35.1H NMR spectrum for 2.09 in d6-DMSO

Deprotection of the hydrophobic PtBuA with trifluoroacetic acid (TFA) afforded a hydrophilic poly(acrylic acid) (PAA). After purification by dialysis the complexed homopolymer was analysed by 1H NMR and IR spectroscopy. The NMR spectrum shows the complete loss of the protons Hc (at 1.43 ppm) and the appearance of the

acidic Hk protons. The pincer end groups discussed in the previous section are still

present and integrate well with respect to each other indicating that the palladium pincer end group is still present. The IR spectra (Figure 36) shows a carbonyl peak shift from 1724 cm-1 to 1698 cm-1 upon deprotection; the latter peak being much broader and indicative of acidic functionality. Acidic functionality can also be inferred from the broad peak at ca. 3000 cm-1 (OH stretch). There is also a loss of the peak at 1143 cm-1 associated with the C-O stretching of the ester. All assignments match those found in the literature.44, 49, 50

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Figure 36. IR spectrum for 2.06 and 2.09 showing the conversion from tbutyl acrylate to acrylic acid.

Deprotection of non-pallidated PtBuA to form PAA, 2.10

The deprotection step was performed analogous to above, but using polymer 2.07.

2.10 was then analysed by 1H NMR and IR spectroscopy to confirm the loss of

tbutyl groups and appearance of acid functionality analogous to 2.09 (see experimental section for details).

Synthesis of alkyl pincer complex, 2.12

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In order to compare the activity and reactivity of the Pd functionalised amphiphiles to a small molecule analogue, it was necessary to synthesise the small molecule equivalent. Dibromo-m-xylene was converted to the alkyl SCS pincer ligand by reaction with dodecane thiol in THF. The SCS pincer ligand was then complexed using the same conditions as the polymer complexation in the previous section. The

1

H NMR spectrum (Figure 37) shows the loss of the aromatic proton, the shift (from 3.68 – 4.22 ppm) and broadening of Hg protons and the appearance of the acetonitrile

protons He. High resolution mass spectrometry gave m/z = 611.2945, which matches

the molecular ion minus the acetonitrile ligand (expected m/z = 611.2936) and the expected palladium isotope pattern was observed.

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