Metal(II) coordination compounds of glycine and phenylalanine were synthesized and characterized using infrared and electronic spectroscopic, and magnetic susceptibility measurements. The complexes were tested for antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Methicillin Resistant Staphylococcus aureus (MRSA), Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris and Candida albicans. The stoichiometric reaction between the metal (II) ions and ligands in molar ratio M:L (1:3) [where M = Mn, Co, Ni, Cu and Cd; L= glycine; phenylalanine] resulted in the formation of five-coordinate square pyramidal dinuclear geometry for both copper complexes and six-coordinate octahedral geometry for the other complexes. The spectroscopic and magnetic moment data suggested that the ligands coordinated via both their amino and carboxylate ion moieties. The complexes demonstrated better activities against one or more of the tested microbes than acriflavine, the standard drug used.

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The reduction of chloro-, bromo-and iodopentacyanocobaltate(III) anions by aquatitanium(III) has been studied in aqueous solution with ionic strength, I = 1.0moldm -3 (LiC1, KBr or KI) at T= 25 ~ The dependence of the observed second-order rate constant, /Cobs, on IN +] has been investigated over the acid range 0.005-0.100 mol dm 3 and is of the general limiting form: kobs ~ ko + k[H +] 1, where k o is appreciable in all cases and k is a composite rate constant. Using values of K a (associated with the Ti m hydrolytic equilibrium constant), obtained from the kinetic data for the TiI"/Co nl redox reactions, and comparison of the rate constants obtained with those for the corresponding V II reductions of the same Co In complexes, it is concluded that the Ti m reductions of these halopentacyanocobaltate(III) complexes proceed via an outer-sphere mechanism.

The interaction of pyridine with four tetrakis(arylisocyanide)cobalt(II) complexes, [Co(CNR) 4 (ClO 4 ) 2 ] R = 2,6-Me 2 C 6 H 3 (A), 2,4,6-Me 3 C 6 H 2 (B), 2,6-Et 2 C 6 H 3 (C) and 2,6-iPr 2 C 6 H 3 (D), have been studied in 2,2,2-trifluoroethanol medium. The kinetics of the reactions were investigated over the 293-318 K temperature range. The reaction profile exhibited two distinct processes, proposed to be an initial fast substitution followed by a slow reduction, for each of the reactions. The pseudo first-order rate constants for both processes increased with increasing concentration of pyridine with the reduction processes exhibiting saturation kinetics at high pyridine concentrations. Steric hindrance plays a significant role in the rates of the reactions, as the rates decrease in the order k(A) > k(B) > k(C) > k(D). The activation enthalpies, DH à , increase from A to D while the activation entropies, DS à , are relatively similar for the four reactions, indicating similar transition states and hence similar mechanisms. Complex B was first synthesized and characterized in this study.

The substitution reactions between penta-ammineaquaruthenium(ii) and thiocyanato (SCN-), protonated acetato (CH,COOH), cyano (HCN), and oxalato (H,C,O,-HC,O,-) ligands (L) have been investigated in aqueous acidic solutions and at an ionic strength 0.20 mol dm-, (LiCI). All the reactions obey the simple second-order rate law (i) and are independent of acid concentration in the range [H ' 3 = 1 .O x 1 O-, t o 1.5 x lo-' mol dm-3. The observed second-order rate constants (1 02kobJdm3 mol-l s-l) measured at 25 "C [20.8 f 1.1 (SCN-), 11.3 & 0.7 (HCN), 2.2 & 0.2 ( H,C,O,-HC,O,-), and 0.36 f 0.03 (CH,COOH)] fall within the characteristic range of substitution rate constants for the substitution of many other ligands previously reported and are therefore insensitive to the nature of the ligand. The activation parameters measured for the substitution reactions between penta-ammineaquaruthenium(1i) and SCN-and HCN respectively are as follows: AH: = 88.00