An extended supramolecular coordination compound produced from PbCl2 and N′-isonicotinoylpicolinohydrazonamide

Abstract

We report a heteroleptic complex [PbCl₂(HL′)]·MeOH (1·MeOH), obtained from N′-isonicotinoylpicolinohydrazonamide (HL) and PbCl₂, where HL′ is a zwitterionic form of HL with the protonated 4-pyridyl and deprotonated amide nitrogen atoms. All the coordination bonds around the Pb²⁺ cation are collected in one hemisphere, yielding a large space gap, which allows two molecules of 1 to come into close proximity to each other and linked through two Pb⋯Cl tetrel bonds of ∼3.41 Å. As a result, a supramolecular dimeric species [PbCl₂(HL′)]₂ is formed, which is stabilized by two C–H⋯Pb anagostic and two C–H⋯Cl interactions. The coordination sphere of the Pb²⁺ cation is completed by the formation of the Pb⋯O tetrel bond with the methanolic oxygen atom. The supramolecular dimeric species are linked through π⋯π(chelate ring) and π⋯π interactions, yielding a 1D supramolecular chain, which is strengthened by N–H⋯Cl hydrogen bonds. These chains are interlinked through a set of hydrogen bonds and weaker interactions. Extensive computational analyses by charge and energy decomposition scheme ETS-NOCV as well as interacting quantum atoms (IQA) allowed us to conclude that most electrostatically dominated noncovalent interactions follow the strength order: Pb⋯O > Pb⋯Cl > N–H⋯Cl > C–H⋯Pb > C–H⋯Cl. Cooperative action of π⋯π and N–H⋯Cl provides an extraordinary dimeric stabilization energy of about −75 kcal mol⁻¹. Finally, an unusual C–H⋯Pb interaction was identified to be attractive despite its long distance (>3.7 Å). Methanol species is found to be engaged not only in Pb⋯O tetrel bonds, but also in hydrogen N–H⋯O bonds and untypical homopolar dihydrogen interactions C–H⋯H–C.