A new specifically designed calix[8]arene for the synthesis of functionalized, nanometric and subnanometric Pd, Pt and Ru nanoparticles

Abstract

A new thioester functionalized calix [8]arene derivative is used for the synthesis of metallic Pd, Pt and Ru nanoparticles, exhibiting several interesting features such as stability and remarkable surface functionalization. Crystalline particles of very small dimensions and good dispersion have been obtained. Keywords: Calixarenes; Nanoparticles; Surface functionalizationThere is presently a considerable interest for the study and the use of metallic or semiconducting nanoparticles because of their novel and attractive physical [1][2][3][4][5] and chemical properties [6,7]. In most cases, the solutionphase synthesis of metallic nanoparticles involves the controlled self-condensation of reduced metal centers in the presence of a suitable ligand. This ligand usually acts a stabilizer for the coordinatively unsaturated metal centers, prevents the agglomeration of the nanoparticles and controls the particle's size [8][9][10][11][12][13][14][15][16][17]. The stabilization of nanoparticles by ligands containing multiple anchoring groups is interesting, as it may improve the stability of the ligand shell due to the cooperative binding of all these groups. Moreover, this cooperativity-based strategy may also open the possibility to use individually weakly bonded ligands, without compromising the stability of the nanoparticles. The lability of each individual weak bond between the anchoring group and the surface of the metal may allow for a much greater reactivity of these nanoobjects in catalysis, along with a good stability due to these cooperative effects. Some examples of nanoparticles with ligands containing multiple anchoring groups such as veratrole or calixarene derivatives [18] have been already described.Most of the interesting properties of calixarenes are directly related to their conformational behavior. The grafting of calixarenes onto nanoparticles may ultimately lead to a better conformational control and thus to new properties for these molecules. New properties may also be expected for these nanoparticles/calixarene nanocomposites, for example, in catalysis, where the reactivity of metallic surfaces may be combined with the molecular recognition properties of calixarenes. We show here that a conformationally very flexible calix [8]arene derivative alone leads to the formation of very stable palladium, platinum and ruthenium nanoparticles of small dimensions. This calix [8]arene is functionalized with both thioester and hydroxyl groups. The former allows for the anchoring of the molecules onto the metallic surfaces, the later may be used for an easy post-derivatization of these nanoobjects. A stability test showed that the nanoparticles are not affected by heating for hours in strongly acidic organic solutions.

Solid State Morphology and Size Tuning of Nanostructured Platinum Using Macromolecular Complexes

“…the (111) , (200) , (200) and (311) planes [15]. Although several solution preparation of Pt° nanoparticles have been reported [14][15][16][17][18][19][20][21][22][23][24][25][26][27] no solid state methods for to prepare Pt° nanoparticles are available. The first way, solution methods, in spite of that to allow the size and morphology control, their incorporation to a solid state device could be not easy.…”

“…H 2 PtCl 4 or H 2 PtCl 6 ) in presence of a reducer such as an alcohol, NaBH 4 or H 2 and polymer stabilizers (also CO or other ligand) [16][17][18][19][20]. The use of Pt(acac) 2 or Pt(dba) 2 as a metallic forerunner with various reducers and stabilizers has also been reported [21][22][23][24].…”

Synthesis, Langmuir and Langmuir–Blodgett films of a calix[7]arene ethyl ester

“…Calix [4]arenes are the most widely studied compounds in the calixarene family [4][5][6][7][8][9][10][11][12][13][14][15][16], although applications of calix [8]arenes [17,18], calix [6]arenes [18] or calix [3]arenes [19] have also been reported. The Langmuir technique has been used to study the response of calixarene derivative monolayers at metal ions present in the subphase [20][21][22][23][24][25][26][27], to amino acids [28] or for the molecular recognition of nucleosides [29].…”

C3v (Trimethyl) p‐(Benzyloxy)calix[6]arene: A Versatile Platform for the Synthesis of Functionalized C3v Calix[6]arenes

“…[1][2][3][4] (Let us consider, for example, ions and/or molecule recognition phenomena, [5][6][7][8][9][10][11][12][13] supramolecular assemblies, [14,15] nanoparticles synthesis, [16][17][18][19][20] etc.) Trimethylated C 3v p-(tBu)calix [6]arene derivatives (Figure 1) were shown to be especially interesting, as they are easily converted into conformationally rigid cone derivatives, showing exceptional characteristics for the selective formation of inclusion complexes.…”

“…Second, new possibilities are opened for easy derivatization of these positions after Pd-catalyzed hydrogenolysis, as already demonstrated for other p-(benzyloxy)-functionalized calixarenes. [7,15,20,38] …”