Exploring supramolecular C-Br•••Br-C interactions as organizing tools in a novel Ni(II)-tetrabromophthalate complex. Crystal structure and solvatochromism studies

The understanding of the non-covalent halogen.halogen interaction inside coordination complexes has special interest as design tools in crystal engineering and coordination chemistry. In this work, we show the use of the supramolecular C-(BrBr)-Br-center dot center dot center dot-C interactions as a tool in the crystalline organization of a Ni(II) complex and its solvatochromic properties. To do so, we selected the 3,4,5,6-tetrabromophthalate (TBrPh) ligand where the Br atoms pointing outside to favor their self-assembly through these interactions. Thus, a novel complex, [Ni(tmeda)(TBrPh)(H2O)(3)]center dot CH3OH was synthesized by the reaction between [Ni(tmeda)].(NO3)(2) (tmeda = N, N, N', N'-tetramethylethylenediamine) and K2TBrPh. The Ni(II)-complex was structurally analyzed by single-crystal X-ray diffraction, Hirshfeld surfaces, multiple analytical tools and DFT calculations. Structural analysis shows that Ni(II)-complex has 1D supramolecular chains based on the cooperativity of intra/inter-molecular charged-assisted hydrogen bonds of type Ni-(OH2O)-O-center dot center dot center dot and C-sp2-(BrBr)-Br-center dot center dot center dot-C-sp2 interactions into 2D networks. These Br.Br interactions organize the crystal packing in the solid state as is evidenced by the molecular electrostatic potential studies and Plot of Hirsfeld surface. This Ni(II)-complex displays solvatochromism with a wide range of solvents (alcohols, DMF, CH3CN, chlorinated solvents), and solvent-dependent absorption maxima presents linear behavior as a function of their dielectric constant.