Experimental

Experimental I - Materials: All chemicals were of analytical grade and were used with out further purification.

II - Measurements: 1- The electronic absorption spectra. The electronic absorption were recorded within the range 200-900 nm by the aid of Jasco V-530 uv/vis spectrophotometer and Shimadzu UV-160A uv/vis spectrophotometer using 1cm matched quartz cells at room temperature. 2- Infrared absorption spectra: The ir absorption spectra of the organic ligands as well as those of the corresponding complexes were recorded in the solid state on Basic Vector 22 FT-IR infrared spectrophotometer using the KBr disc technique. 3- 1Hnmr spectra: The proton nmr spectra were recorded with a (?) using tetramethyl silane ( TMS ) as an internal standerd and dimethyl sulphoxide was used as a solvent. 4- The thermogravimetric analysis of the solid metal complexes: These were carried out in an inert atmosphere (nitrogen) in a platinum cell by using Shimadzu TGA-50H instrument. 5- The magnetic susceptibility: The magnetic susceptibility of the solid complexes were recorded by using Johnson Matthey magnetic susceptibility balance. 1

6- Partial elemental analysis (C,H,): Partial elemental analysis (C,H,) were performed by Heraeus instrument. 7- Partial elemental analysis (Zr, Hf): Partial elemental analysis (Zr, Hf) were performed by Perkin Elmer OPTIMA3000.I.C.P. equipment.

III – Preparation of the organic ligands; The dehydroacetic acid 4N-substituted, 4N-disubstituted and 3-azacyclothiosemicabazones were prepared from 0.01 mol of dehydroacetic acid and the desired substituted thiosemicarbazide (0.01 mol) by refluxing for two hours in 40 cm3 of absolute ethanol with two drops of concentrated sulfuric acid. After reducing the volume by slow evaporation, the resulting solids were filtered, washed with cold isopropyl alcohol and anhydrous ether to apparent dryness(51). The thiosemicarbazides were prepared following the literature procedure(52). preparation of 4N-dimethyl thiosemicarbazide: 4.5 gm (0.1 mol) equal to 12.65 ml of 40% aqueous dimethyl amine was added to a sodium hydroxide solution (4gm of NaOH dissolved in 125 ml of bidistilled water to contain 0.1 mols) and stirred at room temperature for 30 minutes. 7.6 gm (0.1 mol) equal to 6 ml of 99.9 % of carbon disulfide was then added drop wise and the mixture was stirred for more than 12 hours which allowed the organic layer to disappear. A solution containing 0.1 mol of sodium chloroacetate freshly prepared by dissolving 9.45 gm (0.1 mol) of chloroacetic acid and 4 mg (0.1 mol ) of sodium hydroxide in 40 ml bidistilled water was then added with stirring of room temperature for one hour, then 10 ml of concentrated hydroloric acid was added drop wise and S-carboxymethyl N.N-dimethyl 2

[50]

dithiocarbamate [50] was precipitated out as white solid. The product was collected by vacuum filtration and washed with cold isopropyl alcohol and dried at 35ْ c overnight. 8.95 gm (0.05 mol) of S-carboxymethyl N.N-dimethyl dithiocarbamate was dissolved in 30 ml of hydrazine monohydrate (98% pure) and warmed to 40ْ c for about 20 minutes with

[51]

continuous stirring. The resulting 4N-dimethyl thiosemicarbazide [51] was diluted with 15 ml of water and then dried at 35ْ c overnight and being ready for condensation with dehydroacetic acid to produce dehydroacetic acid 4N-dimethylthiosemicarbazone [49-a]. The other substituted thiosemicarbazides were prepared in the same manner except the 4-methyl thiosemicarbazide which was commercial available of analytical grade. ``

+ Preparation of the other ligands: a-49

The dehydroacetic acid 4N-diethyl thiosemicarbazone [HDHA4DE][49-b] dehydroacetic acid 4N-ethyl thiosemicarbazone [HDHA4E][49-c] dehydroacetic acid 4N-methyl thiosemicarbazone 3

[HDHA4M][49-d] dehydroacetic acid 4N-phenylthiosemicarbazone [HDHA4Ph][49-e] dehydroacetic acid 3-piperidyl thiosemicarbazone [HDHA3pip][49-f] and dehydroacetic acid 3-hexamethyleneiminyl thiosemicarbazone [HDHAhexin] [49-g], were prepared in the same manner.

IV Preparation of the solid complex: Zirconium and hafnium complexes of dehydroacetic acid 4Nsubstituted, 4N-disubstituted and 3-azacyclo thiosemicarbazones were prepared as follows: 1-Zirconium complexes: An absolute ethanol solution (~20 ml) containing 0.3223 gm (0.001 mol) of ZrOCl2. 8H2O was added to an absolute ethanol solution (~20 ml) containing 0.001 mol . of the desired ligand and 1 ml of diethyl amine the resulting mixture was refluxed for 2 hours with continuous stirring . The resulting crystals formed were filtered while hot, and washed with absolute ethanol several times to remove any excess diethyl amine or unreacted reactants. 2- Hafnium complexes: The hafnium complexes were prepared in the same manner by reacting 0.3203 gm (0.001 mol ) of HfCl4 with 0.001 mol of the desired ligands.

V Preparation of solutions: 1- Spectral measurements of the ligands in different solvents: The solvents used were of analytical grade and was used without further purification. The ligands are soluble in DMF, ethanol, methanol and acetone making it possible to prepare 10-3 M solution . Any required lower concentration is 4

obtained by appropriate dilution in 10ml calibrated measuring flasks, while the ligands are sparingly soluble in benzene and carbon tetrachloride, hence saturated solutions were firstly prepared, left to obtain equilibrium and insoluble portions were then filtered off so as to obtain clear solution. The resulting solutions were used as such or diluted to give a measurable absorbance. 2- Spectral measurement of the ligands at different pH values: a- Preparation of buffer solutions. Universal buffer solutions were prepared as follows:  0.01M solution of each of phosphoric and acetic acid was prepared by

accurate dilution of a concentrated stock with bidistilled water.  0.01M boric acid solution was prepared by dissolving the appropriate

weight of the recrystallized acid in bidistilled water.  A stock acid mixture was prepared by mixing equal volumes of the three acids in a large bottle.  0.01 M sodium hydroxide stock solution was prepared.  A series of buffer solutions of pH = 3 to pH = 11 were prepared as

recommended by Britton(53) by mixing 75 ml of the acid mixture in 250 ml measuring flask with the appropriate volume of sodium hydroxide solution. The pH value of the buffer solutions was checked using a pH meter. b- Preparation of the ligands at different pH values: An accurate volume (5ml) of the buffer solution of the desired pH value was placed in a 10 ml calibrated measuring flask followed b 5 ml of 10-3 solution of desired ligand in absolute ethanol with constant shaking at 103

5

rpm for five minutes. The resulting solutions were used as such or diluted to give a measurable absorbance. 3- Spectral measurements of Zr and Hf complexes: 2.5 ml of 10-3 M solution of Zr standerd was added to 2.5 ml of 10-3 M solution of the desired ligand in absolute ethanol and one drop of diethyl amine in a 5 ml measuring flask. The solutions of Hf complexes were prepared in the same manner using 10-3 M solution of Hf stander. 4- Absorption measurements of Zr and Hf complexes : The absorption spectra of Zr and Hf complexes were compared with the absorption spectra of the corresponding ligands and the wave lengths concerning Zr and Hf complexes with each ligand were assigned, then a series of Zr and Hf standard solutions with different Zr and Hf concentrations were mixed with the equivalent concentration of each ligand and the absorbance recorded at the previously assigned wave lenthes, the absorbance recrded in tables vs. Concentration and checked for Beer's low.

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EXPERIMENTAL

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