Analysis of supramolecular interactions directing crystal packing of a trans,trans,trans-[diaquabis(4-quinolin-3-yl)-4H-1,2,4-triazole)bis(tricyanomethanide)iron(II)] complex: A combination of XRD, MEP, NBO, QTAIM, and NCI analyses

Abstract

The synthesis and structural characterization of a hydrated high-spin iron(II) complex [Fe(4-qtrz)2(tcm)2(H2O)2] are reported where 4-qtrz = 4-quinolin-3-yl-4H-1,2,4-triazole and tcm = tricyanomethide. The complex was prepared solvothermally and crystallizes in the triclinic space group P1¯ with Z = 1, a = 8.5221(3) Å, b = 8.9343(5) Å, c = 10.0081(5) Å, α = 85.147(2)°, β = 77.166(2)°, γ = 83.784(2)°. The complex is centrosymmetric, with mutually trans pairs of water molecules, of tcm, and monodentate 4-qtrz coordinated via the triazole unit and a combination of O–H⋅⋅⋅N and C–H⋅⋅⋅N hydrogen bonds, forming a three-dimensional framework structure in which the shortest Fe⋅⋅⋅Fe distance is 8.5221(3) Å. An analysis of non-covalent interactions was conducted through reduced density gradient, quantum theory of atoms in molecules and natural bond orbitals. Accordingly, the important contributions of several intra- and inter-molecular hydrogen bonds stabilize the supramolecular structure. The hydrogen bonds occur by electron transfer from the tricyanomethanide nitrogen lone pairs to σ* orbitals in the triazole, quinoline and water moieties. Other hydrogen bonds are attributed to π(CN) → σ*, in triazole and quinoline, transfer. Additionally, a set of π⋅⋅⋅π* interactions between cyano groups (CN⋅⋅⋅CN), π(phenyl of quinoline)⋅⋅⋅π*(CN), and π[CC of C(CN)3] to π*(phenyl of quinoline) were also observed.