In this thesis, the synthesis, characterization, and application of two new dendrimers have been reported through two different projects. In the first project, the first generation dendrimer was obtained from the reaction of hexakis(bromomethyl) benzene, vanillin, and potassium carbonate. TheFT-IRand 1 H-NMRdata confirmed the successful synthesis of the first generatiodendrimer. The second generation dendrimer was prepared by reaction of the first generation dendrimer with ortho -aminopyridine. Then, the final product was characterized byFT-IRand 1 H-NMR techniques. The second generation dendrimer and ruthenium(III) chloride hydrate were used for the synthesis of [Ru 6 (hexpyd)(DMF) 12 Cl 18 ]. Finally, the prepared Ru(III) complex was immobilized on a silica support. The silica-supported Ru(III) dendrimer was reduced by NaBH 4 in 2-methoxyethanol. The prepared nanoparticles (silica-supported dendrimer-encapsulated ruthenium metal nanoparticles) were characterized by ATR-IR, BET, XRD, FE-SEM, TEM, and ICP. According to the results, the size of dendrimer- encapsulated ruthenium metal nanoparticles was found to be 10-15 nm. The silica-supported dendrimer containing ruthenium metal nanoparticles were used as a catalyst for the hydrogenation of citral to 3, 7- dimethyl octanol in a temperature range of 85-110 o C and a H 2 pressure of 14 bar in an autoclave reactor. The reaction progress was monitored by gas chromatography and mass spectrometry (GC/MS). The results show that by increasing the reaction temperature at a constant pressure, the yield of the desired product (3, 7- dimethyl octanol) increases. In the second project, the first generation dendrimer was obtained from the reaction of hexakis(bromomethyl)benzene, vanillin, and potassium carbonate. Then, the second generation dendrimer was prepared by reaction of the first generation dendrimer with para -aminobenzoic acid. Then, the final dendrimer was characterized byFT-IRand 1 H-NMR techniques. In the next step, [Cu 6 (hexcard)(DMF) 18 ](TFA) 12 was synthesized by reaction of copper(II) chloride hydrate with the second generation dendrimer in DMF. The complex was characterized by FT-IR and CHN elemental analysis. For preparation of the copper metal nanoparticles, the Cu(II) dendrimer was reduced by NaBH 4 in 2-methoxyethanol. The dendrimer-encapsulated copper metal nanoparticles were characterized by FT-IR, BET, XRD, FE-SEM, HR-TEM, and ICP. According to the results, the size of dendrimer-encapsulated copper metal nanoparticles was found to be 4-10 nm. Finally, the dendrimer-encapsulated copper metal nanoparticles were used as a catalyst for the reduction of 4-nitrophenol to 4-aminophenol in 2-methoxyethanol. The reaction progress was monitored by UV-Vis spectroscopy. The UV-Vis spectra show an increase in the concentration of 4-aminophenol along with a decrease in the concentration of 4-nitrophenol. The presence of an isosbestic point at ? = 320 nm shows the reduction reaction proceeds through a one-step reaction without any detectable intermediate.