We report here the synthesis and characterization of a few phenolate-based ligands bearing tertamino substituent and their Zn(II) and Cu(II) metal complexes. Three mono/binuclear Zn(II) and Cu(II) complexes [Zn(L1)(H₂O)].CH₃OH.H₂O (1) (H₂ L1 = 6,6′-(((2-dimethylamino)ethylazanediyl)bis(methylene))bis(2, 4-dimethylphenol), [Zn₂(L₂)₂] (2) (H₂L2 = 2,2′-(((2-dimethylamino)ethyl)azanediyl)bis(methylene)bis(4-methylphenol) and [Cu₂(L3)₂.CH₂ Cl₂] (3) (H₂L3 = (6,6′-(((2-(diethylamino)ethyl)azanediyl)bis(methylene)) bis(methylene))bis(2,4-dimethylphenol) were synthesized by using three symmetrical tetradendate ligands containing N₂O₂ donor sites. These complexes are characterized by a variety of techniques including; elemental analysis, mass spectrometry, ¹H, ¹³C NMR spectroscopic and single crystal X-ray analysis. The new complexes have been tested for the phosphotriesterase (PTE) activity with the help of ³¹P NMR spectroscopy. The ³¹P NMR studies show that mononuclear complex [Zn(L1)(H₂O)].CH₃OH.H₂O (1) can hydrolyse the phosphotriester i.e., p-nitrophenyl diphenylphosphate (PNPDPP), more efficiently than the binuclear complexes [Zn₂(L2)₂] (2) and [Cu₂(L3)₂.CH₂Cl₂] (3). The mononuclear Zn(II) complex (1) having one coordinated water molecule exhibits significant PTE activity which may be due to the generation of a Zn(II)-bound hydroxide ion during the hydrolysis reactions in CHES buffer at pH 9.0.

Thiazolidine-2-thione (L¹,NC₃H₅S₂) reacted with copper(I) bromide in CH₃CN under aerobic conditions and transformed through C-S bond cleavage into 3-(2-thiazolin-2-yl)thiazolidine-2-thione (L², C₃H₄S₂N-C₃H₄SN). This thio-ligand L² with Cu^I ion yielded a three coordinate complex, [3-(2-Thiazolin-2-yl)thiazolidine-2-thione]copper(I)bromide 1a which crystallized in the triclinic system with the space group P1 as reported earlier. Treatment of 1a with bis(diphenylphosphino)methane (dppm) in dichloromethane also formed [3-(2-thiazolin-2-yl)thiazolidine-2-thione]copper(I) bromide 1b but it crystallized into the triclinic system with a new space group, P-1: 296(2) K, a, 7.3890(19); b, 8.473(2); c, 9.491(2) Å; 𝛼, 70.273(5); 𝛽, 67.170(5); 𝛾, 84.949(5)°; R, 6.79%. Reactions of copper(II) nitrate with thiazolidine-2-thione followed by the addition of 2,2′-bipyridine or with 2,2′-bipyridine first followed by the addition of thiazolidine-2-thione, gave blue crystals in both the cases. The x-ray crystallography revealed stoichiometry of the complex formed as: [Cu($\kappa^2$-N,N′-bipy)₂($\kappa^1$-ONO₂)](NO₃) 2, which crystallized in monoclinic crystal system with space group, P2₁/n(14). Crystal data: 173(2) K, a, 11.318(1), b, 12.160(1), c, 14.967(1) Å; 𝛽 = 98.01(1)°, R, 3.99%; 296(2) K, a, 11.340(5), b, 12.249(5), c, 15.065(6) Å; 𝛽 = 98.04(2)◦, R, 4.09%.

Equimolar reaction of copper(I) bromide with 2-thiouracil (tucH₂) in acetonitrile-methanol formed a light yellow solid which on subsequent treatment with a mole of triphenyl phosphine (PPh₃) in chloroform has yielded a sulfur-bridged dinuclear complex, [Cu₂Br₂ (𝜇-S-tucH₂)₂ (PPh₃)₂]·2CHCl₃ 1. A reaction of copper(I) bromide with two moles of 2,4-dithiouracil (dtucH₂) in acetonitrile-methanol followed by addition of two moles of PPh 3 , designed to form [Cu(𝜇-S,S-dtuc)₂ (PPh₃)₄ Cu] 2a, instead resulted in the formation of previously reported polymer, {CuBr(𝜇-S,S-dtucH₂)(PPh₃)}_n 2. Reaction of copper(I) iodide with 2- thiouracil (tucH₂) and PPh₃ in 1:1:2 molar ratio (Cu:H₂ tuc:PPh₃) as well as that of copper(I) thiocyanate with pyridine-2-thione (pySH) or pyrimidine-2-thione (pymSH) and PPh₃ in similar ratio, yielded an iodo-bridged unsymmetrical dimer, [(PPh₃)₂ (𝜇-I)₂ Cu(PPh₃)] 3 and thiocyanate bridged symmetrical dimer, [(PPh₃)₂ Cu(𝜇- N,S- SCN)₂ Cu(PPh₃)₂] 4, respectively. In both the latter reactions, thio-ligands which initially bind to Cu metal center, are de-ligated by PPh₃ ligand. Crystal data: 1, P2₁/c: 173(2) K, monoclinic, a, 13.4900(6); b, 17.1639(5); c, 12.1860(5) Å; 𝛽, 111.807(5)° ; R, 5.10%; 2, Pbca: 296(2) K, orthorhombic, a, 10.859(3); b, 17.718(4); c, 23.713(6) Å; 𝛼 = 𝛽 = 𝛾 , 90° ; R, 4.60%; 3, P2 1 : 173(2) K, monoclinic, a, 10.4208(7); b, 20.6402(12); c, 11.7260(7) Å; 𝛽, 105.601(7)° ; R, 3.97%; 4, P-1: 173(2) K, triclinic, a, 10.2035(4); b, 13.0192(5); c, 13.3586(6) Å; 𝛼, 114.856(4); 𝛽, 92.872(4)° ; 𝛾 , 100.720(4) ° ; R, 3.71%. ESI-mass studies reveal different fragments of complexes.