Mixed-ligand complexes of zinc(II) with 1,1-dicyanoethylene-2,2-dithiolate and N-donor ligands: A combined experimental and theoretical study

Abstract The fascinating structural chemistry of zinc(II) with 1,1-dicyanoethylene- 2,2-dithiolate [i-MNT 2-  = {S 2 C:C(CN) 2 } 2- ] ligand is presented. To elaborate, the reactivity of zinc(II) salt towards potassium salt of 1,1-dicyanoethylene-2,2-dithiolate (K 2 i-MNT) and 1,3-diaminopropane (dap) was studied in the presence of two distinct N-donor ligands, α-picoline (2-Methylpyridine) and γ-picoline (4-Methylpyridine), respectively. As a result, two different Zn(II) coordination complexes of formule [Zn 2 (dap) 2 (i-MNT) 2 ] ( 1 ) and {[Zn(dap)(i-MNT)(4-MePy)]·2H 2 O} n ( 2 ) were obtained. They were isolated as stable crystalline solids and fully characterized, including by single crystal X-ray diffraction. Complex 1 is a discrete 0D dimer, whereas 2 is a 1D coordination polymer. Although α-picoline was used during the synthesis of 1 , it is not involved in the metal coordination. Aiming at rationalizing the influence of the different noncovalent interactions, such as H-bonding, unconventional N H···π and anion–π, on the crystal packing of 1 and 2 , DFT calculations (M06-2X/def2-TZVP) were performed. Moreover, luminescence property of the complex 2 was investigated. Finally, in vitro antifungal activity of complex 2 was also screened against five fungi viz. Synchitrium endobioticum , Pyricularia oryzae , Helminthosporium oryzae , Candida albicans (ATCC10231) and Trichophyton mentagrophytes by the disc diffusion method and found to be effective when compared to K 2 i-MNT . H 2 O.