The transition metal complexes of Fe(II), Ni(II) and Cu(II) derived from phthalazine based ligands: Synthesis, crystal structures and biological activities

•Synthesis of pthalazine based ligands.•Synthesis of Fe(II), Cu(I) and Ni(II) complexes in 1:1 and 1:2 molar ratio.•Spectroscopic characterization: UV-visible and FT-IR, NMR spectroscopy.•Single crystal X-ray crystallographic studies of some metal complexes.•Studies of antibacterial, antifungal, antioxidant and DNA cleavage activities. Twelve metal complexes of Iron(II), Nickel(II) and Copper(II) have been synthesized in 1:1 and 1:2 molar ratio from new phthalazine based ligands (E)-2-(phthalazin-1-yl)-1-(1-(pyridin-2-yl)ethylidene)hydrazine (L1) and (E)-2-(phthalazin-1-yl)-1-((pyridin-2-yl)methylene)hydrazine (L2). The compounds have been characterized by UV-Visible, FT-IR, 1H-NMR, LC-MS/ESI-MS spectroscopic techniqueas well as conductivity measurements and finally structures of some of the compounds have been confirmed through single crystal X-ray crystallographic technique. Crystal data for [Cu(II)L1Cl](2) complex: C15H12ClCuN5, triclinic, Space group P-1, a = 10.5114(11) Å, b= 10.7962(11) Å, c = 13.7510(14) Å, α = 74.206(9)°, β = 71.981(9)°, γ = 84.122(8)° and Z = 1, final R1 was 0.0553(I > 2σ(I)) and wR2 was 0.1892(all data). Crystal data for [Ni(II)(L1)2](ClO4)2(7) complex: C30H26Cl2N10NiO8, monoclinic, Space group P21/n, a = 13.0740(7) Å, b = 19.1326(10) Å, c = 14.5808(9) Å, α = 90°, β = 104.511(6)°, γ = 90°, V = 3530.9(4) Å3, Z = 4, final R1 was 0.0778 (I > 2σ(I)) and wR2 was 0.2226 (all data). Crystal data for [(L2)2(μ-Cl)Cu2(II)]Cl(10) complex: C28H22Cl2Cu2N10, triclinic, Space group P-1, a = 7.7441(15) Å, b = 14.954(3) Å, c = 15.004(3) Å, α = 92.458(11)°, β = 96.234(11)°, γ = 96.291(12)° and Z = 2, final R1 was 0.0576(I > 2σ(I)) and wR2 was 0.1671(all data). Crystal data for [Ni(II)(L2)2](ClO4)2(14) complex: C28H22N10O8Cl2Ni, monoclinic, Space group P21/c, a = 13.1220(12) Å, b = 11.3216(10) Å, c = 23.982(2) Å, α = 90°, β = 104.621(4)°, γ = 90° and Z = 4, final R1was 0.0931(I > 2σ(I)) and wR2 was 0.3083 (all data). The compounds were investigated for their antimicrobial, antioxidant and DNA cleavage activities. [Display omitted]