Pt(II) Uptake by Dendrimer Outer Pockets:  1. Solventless Ligand Exchange Reaction

Tarazona-Vasquez, Francisco; Balbuena, Perla B.

doi:10.1021/jp0761517

Cited by 12 publications

(18 citation statements)

References 29 publications

(42 reference statements)

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“…The broad absorption peak of CPAMAM at 301 nm is converted to a narrow and strong peak at 292 nm after 24 h, which is consistent with the phenomenon of Pd 2+ complexes with the fourth-generation dendrimer in the aqueous phase . This change may result from ligand exchange, including chloride, the internal amine groups in CPAMAM, and water . The new strong peak at 292 nm is caused by ligand–metal charge transfer and is related to the formation of metal ion/hyperbranched polymer macromolecules. , …”

Section: Resultssupporting

confidence: 73%

“…38 This change may result from ligand exchange, including chloride, the internal amine groups in CPAMAM, and water. 55 The new strong peak at 292 nm is caused by ligand−metal charge transfer and is related to the formation of metal ion/hyperbranched polymer macromolecules. 56,57 The addition of 10 equiv of NaBH 4 results in the reduction of CPAMAM (Pd 2+ ) to Pd@CPAMAM, and the solution turns dark brown (Figure 2a).…”

Section: Resultsmentioning

confidence: 99%

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New Strategy for High-Performance Integrated Catalysts for Cracking Hydrocarbon Fuels

Zhao

Bai

et al. 2019

ACS Appl. Mater. Interfaces

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In this study, we described the synthesis, characterization, and application of hyperbranched polymer-encapsulated metal nanoparticles (HEMNs) as integrated catalysts for the supercritical cracking of hydrocarbon fuels. The metal precursor was extracted into the organic phase using a hydrocarbon-soluble hyperbranched poly(amidoamine) (CPAMAM) and then reduced in situ by NaBH4 to produce HEMNs with virtually a single-size distribution. The monitoring of the preparation process by UV–vis demonstrated the feasibility of this encapsulation approach, and the successful synthesis of three different types of HEMNs, metal (Pd, Pt, Au)@CPAMAM, reflected the universality of this method. Compared with the existing catalyst octadecylamine-stabilized Pd nanoparticle, Pd@18N, HEMNs were superior in every aspect. The new encapsulation method allowed metal NPs to have a smaller particle size beneficial to their overall specific surface area and a higher proportion of active surface atoms for a better catalytic activity. Moreover, the space-limiting effect of the polymer allowed the three HEMNs to be highly dispersed in decalin and exhibited admirable stability under storage tests for up to 12 months and high-temperature stability tests at 180 °C. During the supercritical cracking of decalin, Pd@CPAMAM possessed a much better catalytic performance than Pd@18N and CPAMAM (which can also be used as a macroinitiator). To obtain the same heat sink of 3.02 MJ/kg, the temperature could be lowered from 725 to 701, 693, and 699 °C for Pd, Pt, and Au HEMNs, respectively. Pt HEMN turned out to be the best due to its excellent catalytic dehydrogenation/cracking performance, with the conversion of decalin increasing from 22.3 to 50.7% and the heat sink rising from 2.18 to 2.62 MJ/kg with the existence of 50 ppm Pt@CPAMAM, at 675 °C. The significant enhancements were ascribed to the synergistic catalysis through the remarkable abilities of nanometals to catalyze dehydrogenation/cracking of fuel, the supercritical stabilization effects from CPAMAM, and the initiation effects of the hyperbranched polymer CPAMAM.

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Section: Resultssupporting

confidence: 73%

Section: Resultsmentioning

confidence: 99%

New Strategy for High-Performance Integrated Catalysts for Cracking Hydrocarbon Fuels

Zhao

Bai

et al. 2019

ACS Appl. Mater. Interfaces

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“…Most of the experimental work has been devoted to elucidate aspects of the ligand substitution reaction, also called ligand exchange reaction (LER). 4,7,8 Our previous study 9 on solventless ligand exchange reaction (LER) of tetrachloroplatinate anion and its mono-and diaquated species revealed that binding of Pt(II) to one dendrimer site (monodentate binding) is thermodynamically feasible in agreement with previous NMR experiments. 8 Notwithstanding the combined NCB (noncovalent binding) + LER free energy of PtCl 4 2to bind directly to a tertiary amine N (N3) site is greater than the NCB free energy of any other competitor ion, 9 its activation energy toward direct binding with the N3 site was found to be higher than its activation energy toward aquation.…”

Section: Introductionsupporting

confidence: 73%

Pt(II) Uptake by Dendrimer Outer Pockets: 2. Solvent-Mediated Complexation

Tarazona-Vasquez

Balbuena

2008

J. Phys. Chem. B

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We study the effect of the solvent (water) on the ligand exchange reaction (LER) step of Pt(II) complexation to PAMAM dendrimers. The results suggest that aquation of tetrachloroplatinate anion (PtCl(4)(2-)) inside PAMAM outer pockets occurs prior to its reaction with dendrimer atom binding sites. Thus, the active involvement of water opens up several pathways by which Pt(II) can bind to tertiary amine sites (N3). Monodentate binding pathways by which a PtCl(3)(-) moiety is obtained as a final product rather than PtCl(2)(H(2)O) are considered to be the predominant routes due to their smaller degree of complexity, including aspects such as less number of intermediates and lower energy barriers. Monodentate binding of Pt(II) to the secondary amide site (N2) is found to be feasible, in agreement with previous NMR experiments, once aquation of the tetrachloroplatinate anion has occurred. For this type of binding to occur, the dendrimer branch amide group configuration would have to switch from its equilibrium position (trans) to a cis position. It is also found that outer pockets aid Pt(II) complexation with the dendrimer mainly by making the noncovalent binding (NCB) step more favorable than that in branchless environments. Finally, our results predict that competitive monodentate binding of Pt(II) to either N3 or N2 is thermodynamically rather than kinetically driven.

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“…Previously dendrimers have been examined sporadically as delivery vehicles for several different types of platinum drugs and complexes [15][16][17][18][19][20][21][22]. These dendrimers have included PAMAM, polyglycerol [22], poly(propyleneimine) [23], and thiol-yne derived [21] dendrimers with the active components of both cisplatin [17] and oxaliplatin [16] and a novel DNA intercalating platinum complex [15].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of anionic half generation 3.5–6.5 poly(amidoamine) dendrimers as delivery vehicles for the active component of the anticancer drug cisplatin

Kirkpatrick

Plumb

Sutcliffe

et al. 2011

Journal of Inorganic Biochemistry

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Title: Evaluation of anionic half generation 3.5-6.5 poly(amidoamine) dendrimers as delivery vehicles for the active component of the anticancer drug cisplatin Article Type: Regular Paper Keywords: cancer; platinum; PAMAM dendrimer; cisplatin; guanosine; cytotoxicity; diffusion NMR. Abstract: Aquated cisplatin was added to half-generation PAMAM dendrimers and the resultant complexes were purified by centrifuge. The drug-dendrimer complexes were then characterised by 1-D and diffusion 1H NMR y and ICP-AES. The amount of drug bound was found to increase in proportion with dendrimer size: G3.5, 22 cis-{Pt(NH3)2}molecules per dendrimer; G4.5, 37; G5.5, 54; and G6.5, 94, which represent only a fraction of the available binding sites on each dendrimer (68, 58, 42 and 37%, respectively). Drug release studies showed that some drug remains bound to the dendrimer even after prolonged incubation with 5'GMP at temperatures of 60 oC for over a week (percentage of drug released 18, 30, 35 and 63%, respectively). Attachment of the drug was found to decrease the radius of the dendrimers. Finally, the effect of the dendrimer on drug cytotoxicity was determined using in vitro assays with the A2780, A2780cis and A2780cp ovarian cancer cell lines. The free dendrimers display no cytotoxicity whilst the drug-dendrimer complexes showed moderate activity. In vivo activity was examined using an A2780 tumour xenograft. Cisplatin, at its maximum tolerated dose of 6 mg/kg, reduced tumour size by 33% compared to an untreated control group. The G6.5 cisplatin-dendrimer complex was administered at two doses (6 and 8 mg/kg equivalent of cisplatin). Both were well tolerated by the mice. The lower dose displayed comparable activity to cisplatin with a tumour volume reduction of 32%, but the higher dose was significantly more active than free cisplatin with a tumour reduction of 45%. We have revised the manuscript taking into account all your listed corrections and stylistic requirements.As siDNA and PBS were used only once in the manuscript we have now written these in full and not used them as abbreviations.For simplicity, we have made figure 5 just black and white and have changed the figure caption to reflect this. G4.5, 37; G5.5, 54; and G6.5, 94, which represent only a fraction of the available binding sites on each dendrimer (68, 58, 42 and 37%, respectively). Drug release studies showed that some drug remains bound to the dendrimer even after prolonged incubation with 5'GMP at temperatures of 60 o C for over a week (percentage of drug released 18, 30, 35 and 63%, respectively). Attachment of the drug was found to decrease the radius of the dendrimers. Finally, the effect of the dendrimer on drug cytotoxicity was determined using in vitro assays with the A2780, A2780cis and A2780cp ovarian cancer cell lines. The free dendrimers display no cytotoxicity whilst the drug-dendrimer complexes showed moderate activity. In vivo activity was examined using an A2780 tumour xenograft. Cisplatin, at its maximum tolerated dose of 6 mg/kg, reduced tu...

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Pt(II) Uptake by Dendrimer Outer Pockets: 1. Solventless Ligand Exchange Reaction

Cited by 12 publications

References 29 publications

New Strategy for High-Performance Integrated Catalysts for Cracking Hydrocarbon Fuels

New Strategy for High-Performance Integrated Catalysts for Cracking Hydrocarbon Fuels

Pt(II) Uptake by Dendrimer Outer Pockets: 2. Solvent-Mediated Complexation

Evaluation of anionic half generation 3.5–6.5 poly(amidoamine) dendrimers as delivery vehicles for the active component of the anticancer drug cisplatin

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