428 A.A. E1-Asmy, A. S. Babaqi and A. A. A1-Hubaishi Transition Met. Chem., 12, 428-431 (1987) Table 1. Conditional formation constants and molar absorptiv- ity values of the Com-dipeptide complexes measured at pH = 2.2 and 20~C. (glycylglycine 2m, x = 500nm, glycylthreonine 2,~,x = 500 nm, glycylaspartic acid 2max = 500 rim, glycyltyrosine2max = 500 rim, and glycylproline 2max = 540 nm) complexes. The higher stability of the cobalt(III)- glycylaspartic acid complex with respect to those of other dipeptides with a comparable bulk, can be explained by ascribing weaker chelation to the second carboxylate group. Ligand Species ft. e L/M ( x 104) 1 x mol - 1 x cm- 1 References gly-gly 2:1 7.7 165 gly-thr 2:1 4.8 170 gly-asp 2:1 8.3 140 gly-tyr 2:1 5.4 160 g/y-pro 3:1 1.5 112 centration molar ratio (CL/CM)< 1.5 in the case of dipeptides, whereas a ratio equal to 1 was reached in the case of aminoacids. The system was studied at the wavelength corresponding to the absorption maximum lowest energy band of the cobalt(III) for each system (Table 1). A pH value of 2.2 was chosen as previously ~5). At this pH it is possible to work in the absence of the oxygenated species. In the pH range at ca. 2.2, we verified that slight uncertainties in the pH value do not produce variations in the absorbance measurements (Figure 3). Moreover, the self-buffering power of the ligands keeps the pH stable and external buffers which could interfere with the complex- ation equilibria are not required. The measured values for the concentration ratios at equilibrium are shown in Table 1. They are in accordance with the hypothesis advanced for the cobalt(III)-aminoacids complexes ts), which suggests that the carboxylate group is the donor in all the systems considered. Comparing the reported values, it seems that the bulk of the ligand influences strongly the stability of the (I)A. Bondoli and V. Carunchio, J. Inorg. Nucl. Chem., 34, 3491 (1972). (2) U. Biader Ceipidor and V. Carunchio, J. Inorg. Nucl. Chem., 37, 375 (1975). (3)R. Bedetti, U. Biader Ceipidor, V. Carunchio and A. Messina, Rend. Atti Acc. Naz. Lintel, 56, 942 (1974). (4)R. Bedetti, U. Biader Ceipidor, V. Carunchio and M. Tomassetti, J. Inorg. Nucl. Chem., 38, 1391 (1976). (5)S. Balzamo, R. Bucci, V. Carunchio and G. Vinci, Transition Met. Chem., 11, 316 (1986). (6)R. Yalman, J. Phys. Chem., 65, 556 (1961). (7)R. D. Jones, D. A. Summerville and F. Basolo, Chem. Rev., 79, 139 (1979). ts) S. Fallab and P. R. Mitchell, Adv. Inorg. Bioinorg. Mech., 3, 311 (1984). 19) B. S. Tovrog, D. J. Kikto and R. S. Drago, J. Am. Chem. Soc., 98, 5144 (1976). (I~ Sigel and R. B. Martin, Chem. Rev., 82, 385 (1982). ~11)W. R. Harris, G. McLendon and A. E. Martell, J. Am. Chem. Soc., 98, 378 (1976). I~z)M. T. Barnet, H. C. Freeman, D. A. Bukingham, I-Nan Hsu and D. Van der Helm, Chem. Comm., 367 (1970). (13)O. Yamauchi, K. Tsujide and A. Odani, J. Am. Chem. Soc., 107, 659 (i985). (14)M. S. Michailidis and R. B. Martin, J. Am. Chem. Soe., 91, 4683 (1969). (15) R. D. Gillard and A. Spencer, J. Chem. Soc. (A), 27t8 (1969). (~6)W. R. Harris, R. C. Bess, A. E. Martell and T. H. Ridgeway, J. Am. Chem. Soc., 99, 2958 (1977). (Received 11 May 1987) TMC 1706 Ligational, corrosion inhibition and antimicrobial properties of 4-phenyl- 1-benzenesulphonyl-3-thiosemicarbazide Ahmed A. EI-Asmy* Chemistry Department, Faculty of Science, Mansoura University, Mansoura, Egypt Abdallah S. Babaqi and Ahmed A. AI-Hubaishi Faculty of Science, Sana'a University, Sana'a, Yemen A R Summary Complexes of transition metal ions with 4-phenyl-1- benzenesulphonyl-3-thiosemicarbazide (HPBST) have been prepared and characterized and attempts have been made to elucidate their structures by elemental analysis, molar conductivities, n.m.r., i.r. and reflectance spectra and by magnetic measurements. The i.r. spectra show that the ligand is mononegative bidentate, coordinating via * Author to whom all correspondence should be directed at: Sana'a, P. O. Box 11503, Yemen A R NH and C--S groups. Thioenolization is confirmed by the pH-titration of HPBST and its metal(II) complexes against 0.01M NaOH. The stereochemistry of the cobalt(II), nickel(II) and copper(I) complexes is discussed and confirmed by the magnetic and spectral studies. The crystal field parameters of the cobalt(II) complex were also evaluated. The antibacterial and antifungal activities of HPBST and of its metal(II) complexes are investigated. The results reveal that HPBST exhibits greater antimicro- bial activities than its complexes. Also, the corrosion inhibition of aluminium in trichloroacetic acid using HPBST was studied by weight loss and corrosion potent- 0340-4285/87 $03.00 + .12 9 1987 Chaoman and Hall +tel