Synthesis, characterization and magnetic properties of dinuclear double end-on azido bridged Ni(II) complex with the condensation product of 2-quinolinecarboxaldehyde and Girard’s T reagent. DFT-BS explanation of ferromagnetic exchange coupling in dinuclear Ni(II) complex. Display omitted A dinuclear double end-on azido bridged Ni(II) complex Ni2L2(μ-1,1-N3)2(N3)2 (1) with the condensation product of 2-quinolinecarboxaldehyde and trimethylammonium acetohydrazide chloride (Girard’s T reagent) (HLCl) has been synthesized and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction, magnetic measurements and DFT studies. In complex 1 intra-dimer ferromagnetic coupling between Ni2+ ions (J=+12.0(2)cm−1) and inter-dimer antiferromagnetic interaction (δ=−0.8(3)cm−1) were observed. DFT-BS calculations provided explanation of ferromagnetic exchange coupling in complex 1.