Coordination complexes and polymers from the initial application of phenyl-2-pyridyl ketone azine in mercury chemistry

Abstract A series of new mercury(II) azine Schiff base complexes have been synthesized and characterized from the initial use of phenyl-2-pyridyl ketone azine in Hg II chemistry. The synthetic/crystallization technique utilized involved the use of a branched tube, where temperature differential allowed for the slow crystallization of the products. The synthesized compounds are the mononuclear [Hg(L)Cl 2 ] ( 1 ), [Hg(L)Br 2 ] ( 2 ), [Hg(L)(NO 2 ) 2 ] ( 3 ), and the dinuclear [Hg 2 (μ-L)(SCN) 4 ] ( 4 ) coordination compounds, as well as a 1D coordination polymer [Hg(L)(μ-I) 2 HgI 2 ] n ( 5 ) (L = phenyl-2-pyridyl ketone azine). From the X-ray data, it is evident that this versatile ligand functions as a bi- or tridentate chelate, and is also able to bridge two Hg II centers. The crystal structures of 1 and 2 are similar, both containing two crystallographically independent Hg II molecules, one tetrahedrally coordinated and one exhibiting trigonal bipyramidal geometry. The heptacoordinated Hg II center in 3 adopts a distorted capped trigonal prismatic coordination sphere, while in the dinuclear complex 4 , the metal ions are bridged via the bis(bidentate) L and each center is also bound to two S-bonded thiocyanate units. The one-dimensional coordination polymer in 5 consists of a tetrahedral HgI 4 and a trigonal bipyramidal HgN 3 I 2 chromophore unit, bridged by μ-I − bridges. The thermal stability of the crystal lattice in 1 – 5 follows the pattern 3  >  1  >  2  >  5  >  4 , as studied by TG/DTA, while the TG data of 1 , 2 , and 5 are similar, but different than the respective ones for 3 and 4 , between which important similarities are observed. In the solid state, the ligand and compounds 1 – 5 exhibit intraligand π → π ∗ fluorescence at room temperature.