In this thesis, three mononuclear complexes of lanthanum(III), yttrium(III) and scandium(III), [M(H 2 O) 2 (MO) 3 (DMF) 3 ] (M= La(III) and Y(III)) and [Sc(H 2 O) 3 (MO) 3 ].DMF have been prepared and characterized by elemental analysis, FT-IR and UV/Vis spectroscopy. The orange crystals of [La(H 2 O) 2 (MO) 3 (DMF) 3 ] and [Y(H 2 O) 2 (MO) 3 (DMF) 3 ] were grown by diffusion of ether into a DMF solution of the complexes. The solid state structure of these complexes was determined using single crystal X-ray crystallography. These complexes are eight-coordinate and have a triclinic crystal system with space group of P? . The M(III) center is coordinated by three oxygen atoms of the anionic methyl orange ligands in the monodentate fashion, three oxygen atoms of the neutral DMF ligands, and two oxygens of H 2 O ligands. The Electronic spectra of the complexes were taken in DMF and shown the intense absorption bands seen in the UV region due to the intraligand n ? ? * and ? ? ? * transitions of the MO ligands. The FT-IR spectra of complexes show a sharp and strong absorption bands for the S–O, S=O, C=C, N=N and C–N stretching vibrations in the coordinated methyl orange ligands. Also, the bands at 3430 and 1652 cm -1 are assigned to the stretching vibration of the O–H bond of the coordinated water molecules and coordinated DMF ligands. The packing of the structure is stabilized by medium-strong intermolecular O–H···O hydrogen bonds (a) and intramolecular O–H???O hydrogen bonds (b) that have been formed between the H atoms of the water molecules and the free O atoms of the sulfonate group in the methyl orange ligands. Then the lanthanum oxysulfate (La 2 O 2 SO 4 ), yttrium oxysulfate (Y 2 O 2 SO 4 ), and scandium oxide (Sc 2 O 3 ) nanoparticles were prepared by the calcination method of these three complexes as the precursors. A series of further experiments were carried out to investigate the reaction conditions.The nanoparticles were characterized by FT-IR, X-ray diffraction analysis (XRD), and field emission scanning electron microscopy (FE-SEM). Finally, the hydrogen adsorption and desorption of the complexes and their nanoparticles at a glassy carbon electrode (GCE) and carbon paste electrode (CPE) in H 2 SO 4 were investigated by cyclic voltammetry (CV). The modified CPE was obtained by adding powder of the precursor complex or nanoparticles to the carbon graphite powder, then, the pastes were carefully hand-mixed with mortar and pestle for 10 min, finally paraffin oil added to the mixture. A portion of these resulting pastes was packed into the end of a plastic syringe tube to form different electrodes, respectively. Electrical contact to the paste was established by forcing a copper wire down the glass tube and into the back of mixture. The voltammograms showed a pair of peaks corresponding to the adsorption/desorption of hydrogen for all compounds. Also, the electrocatalytic activity of these compounds for hydrogen adsorption and hydrogen evolution reaction (HER) was investigated by linear sweep voltammetry (LSV).