J. Indian Chern. Soc., Vol. 79, March 2002, pp. 219-221 Synthesis and spectral studies on transition metal complexes with 'Costa type' of ligands containing aromatic motifs K. Hussain Reddy* and M. Radhakrishna Reddy Department of Chemistry, Sri Krishnadevaraya University, Anantapur-515 003, India Fax : 091-08554-29043 Manuscript received 27 November 2000, revised 17 April 2001, accepted 4 August 2001 Macrocyclic nickel(ll) and copper(ll) complexes have been prepared using preformed ligands, viz. bis(diacetylmonoxime)-1,2- phenylenediimine and bis(diacetylmonoxime)-3,4-tolylenediimine. ESR spectral data of copper complexes suggest that the unpaired electron lies predominantly in the dxl-yl orbital. Various electronic and ESR parameters have been calculated and discussed. Electrochemical behavior of these complexes has been investigated by cyclic voltammetry. Costa type 1 ofligands derived using diacetylmonoxime and aliphatic diamines have been frequently employed for the preparation of cobalt complexes (to derive model compounds for vitamin 8 12 ) 2 • However, metal complexes with costa type of ligands containing aromatic motifs are scarce. Re- cently we have reported 3 organometal complexes with these modified ligands. We report herein the synthesis, character- ization, spectral and electrochemical studies on macrocy- clic nickei(II) and copper(ll) complexes of bis(diacetyl- monoxime)-1 ,2-phenylenediimine, (DOH) 2 Pn and bis(di- acetylmonoxime)-3,4-tolylenediimine, (DOHh Tn. Results and Discussion All the complexes (Table 1) are stable at room tempera- ture, non-hygroscopic, insoluble in water and readily soluble in methanol, ethanol, DMF and DMSO. The molar conduc- tivity data (1.5-2.4 n- 1 cm 2 mol- 1 ) suggest that the com- plexes are non-electrolytes. Table 1. Analytical data of nickel and copper complexes (_) -4) • Compd. Molecular formula Colour M.p. no. ·c [Ni(C 1 4H 17N4 02)(Cl)(H20)] Reddish brown 280d 2 [Cu(C 14 H 17 N 4 0 2 )(Cl)(H 2 0)] Greenish black 310d 3 [Ni(C ISH 19N402)(Cl)(Hp)] Reddish brown 290d 4 [Cu(C 1 sH 19 N 4 0 2 )(CI)(H 2 0)] Greenish black 209-211 • All compounds gave satisfactory C, H and N analyses. Magnetic susceptibillity and electronic spectra : -. The magnetic moments of 1 and 3 (2.91 and 3.32 B.M.) are indicative of octahedral structure for nickel( II) complexes. The magnetic moments of the copper( II) complexes 2 and 4 (1.69 and 1.72 B.M.) correspond to the presence of one unpaired electron. R=H, M=Ni 2 R= H. M =Cu 3 R = Cl-1 3 , M = Ni 4 R = CH 3 , M = Cu The electronic spectra (DMF) of nickel(ll) complexes I and 3 exhibit three bands at 9950, 1 0582; 16129, 17699; 27397,23810 cm- 1 , assigned to 3 A 2 g(F) 3 T 2 g(F), 3 A 2 g(F) 3 T 1 g(F) and 3 A2g(F) 3 T 1 g(P) transitions, respectively, as expected for octahedral geometry. The spectral param- eters like ligand field splitting energy ( 10 Dq), Racah inter- electronic repulsion parameter (B), covalent factor (8 35 ) and ligand field stabilization energy (LFSE) are presented in Table 2. The Band 8 35 values have been calculated for nickel complexes following standard equations 4 . The 8 35 values obtained for the present complexes are less than unity sug- gesting considerable amount of covalent character of the metal-ligand bonds. The electronic spectra of copper( II) com- plexes 2 and 4 in DMF show a broad maxima at 16230 and 17479 cm-1, respectively, with a shoulder on the low en- ergy side at 13650 and 15625 cm- 1 , respectively, suggest- ing that these complexes have distorted octahedral struc- ture. In addition, another band observed above 24000 cm- 1 is assigned to. charge transfer transitions 5 . 219