A new coordination polymer constructed from Pb(NO3)2 and a benzylideneisonicotinohydrazide derivative: Coordination-induced generation of a π-hole towards a tetrel-bonding stabilized structure

Abstract

We report on a new Pb(II) coordination polymer [Pb(HL)(NO3)2]n (1), obtained from a direct reaction of Pb(NO3)2 with N'-4-(dimethylamino)benzylideneisonicotinohydrazide (HL). The coordination sphere around the Pb(II) cation is built by the 1,4-N,O-chelating neutral HL, by six oxygen atoms from three chelating nitrate anions, and by the pyridyl nitrogen donor from a symmetry related molecule. The ligand HL and one of the nitrate anions, acting as bridging species, yield two 1D zig-zag polymeric chains along the crystallographic axes b and c, respectively. As a result, the overall structural architecture of 1 is a 2D layer, which is reinforced by the N–H···O hydrogen bonds and by π···π interactions, resulting in a 4-connected uninodal sql/Shubnikov tetragonal plane net topology or a 3,5-connected binodal 3,5L1 net, once the N–H···O hydrogen bonds are considered. In addition of these conventional interactions, the coordination of the hydrazide group to the Pb(II) ion provokes the formation of a π-hole at the carbonyl group that establishes a tetrel bond with the oxygen atom of a nearby nitrato-ligand belonging to another polymeric chain. This interaction has been studied energetically at the PBE0-D3/def2-TZVP level of theory and also characterized by using a combination of MEP, QTAIM and NCIplot computational tools.