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

We report a heteroleptic complex [PbCl2(HL ')]center dot MeOH (1 center dot 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 center dot center dot center dot Cl tetrel bonds of similar to 3.41 angstrom. As a result, a supramolecular dimeric species [PbCl2(HL ')](2) is formed, which is stabilized by two C-H center dot center dot center dot Pb anagostic and two C-H center dot center dot center dot Cl interactions. The coordination sphere of the Pb2+ cation is completed by the formation of the Pb center dot center dot center dot O tetrel bond with the methanolic oxygen atom. The supramolecular dimeric species are linked through pi center dot center dot center dot pi(chelate ring) and pi center dot center dot center dot pi interactions, yielding a 1D supramolecular chain, which is strengthened by N-H center dot center dot center dot 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 center dot center dot center dot O > Pb center dot center dot center dot Cl > N-H center dot center dot center dot Cl > C-H center dot center dot center dot Pb > C-H center dot center dot center dot Cl. Cooperative action of pi center dot center dot center dot pi and N-H center dot center dot center dot Cl provides an extraordinary dimeric stabilization energy of about -75 kcal mol-1. Finally, an unusual C-H center dot center dot center dot Pb interaction was identified to be attractive despite its long distance (>3.7 angstrom). Methanol species is found to be engaged not only in Pb center dot center dot center dot O tetrel bonds, but also in hydrogen N-H center dot center dot center dot O bonds and untypical homopolar dihydrogen interactions C-H center dot center dot center dot H-C.