Interactions Between [PdX] (X=Cl, Br) Dianions in Presence of Counterions.

The interaction between two square palladium (II) dianions PdX (X=Cl, Br) is evaluated by crystal study and analyzed by quantum chemical means. The arrangement within the crystal between each pair of PdX neighbors is suggestive of a Pd⋅⋅⋅X noncovalent bond, which is verified by a battery of computational protocols. While the potential between these two bare dianions is computed to be highly repulsive, the introduction of even just two counterions makes this interaction attractive, as does the presence of a constellation of point charges.

Unique Use of Dibromo-L-Tyrosine Ligand in Building of Cu(II) Coordination Polymer-Experimental and Theoretical Investigations.

Although the crystals of coordination polymer {[CuCl(O,O'-L-BrTyr)]}n (1) (L-BrTyr = 3,5-dibromo-L-tyrosine) were formed under basic conditions, crystallographic studies revealed that the OH group of the ligand remained protonated. Two adjacent [CuCl(L-BrTyr)] monomers, bridged by the carboxylate group of the ligand in the bidentate bridging mode, are differently oriented to form a polymeric chain; this specific bridging was detected also by FT-IR and EPR spectroscopy. Each Cu(II) ion in polymeric compound 1 is coordinated in the xy plane by the amino nitrogen and carboxyl oxygen of the parent ligand and the oxygen of the carboxyl group from the symmetry related ligand of the adjacent [Cu(L-BrTyr)Cl] monomer, as well as an independent chlorine ion.

Anion⋯anion interaction within Ch(CH)X (Ch = S, Se, Te; X = Cl, Br, I) dimers stabilized by chalcogen bonds.

In a crystal, a pair of homoanions (Te(CH)Cl) are arranged in a parallel manner, close enough to interact with each other. Quantum chemical analysis indicates the existence of two strong noncovalent chalcogen bonds engaging the σ-hole of the chalcogen atoms from one unit and electron density accumulated on the Cl atom of the neighboring unit. In a solid, chalcogen bonds are supported by a multitude of HBs between interacting (Te(CH)Cl) anions and the CHNBr counterions.

The Role of Hydrogen Bonds in Interactions between [PdCl] Dianions in Crystal.

[PdCl] dianions are oriented within a crystal in such a way that a Cl of one unit approaches the Pd of another from directly above. Quantum calculations find this interaction to be highly repulsive with a large positive interaction energy. The placement of neutral ligands in their vicinity reduces the repulsion, but the interaction remains highly endothermic.