A Mononuclear Homoleptic Complex of N '-(4-Hydroxybenzylidene)isonicotinohydrazide with Lead(II): Experimental and In Silico Studies

In this work, we report on the facile one-pot synthesis of a mononuclear homoleptic complex of N'-(4-hydroxybenzylidene)isonicotinohydrazide with lead(II) [PbL₂] in MeOH. Our newly developed synthetic approach allowed to obtain the title compound with a good yield of 79%, which is somewhat higher in comparison to the previously reported synthesis using the branched tube method from an equimolar mixture of Pb(ClO₄)₂, KSCN and HL in EtOH. A molecular structure of [PbL₂] is characterized by intramolecular two anagostic C–H⋅⋅⋅Pb and one C–H⋅⋅⋅O interactions, which stabilize a highly bent hemidirected geometry of a molecule. The title complex was studied in detail using the DFT/B3LYP/6-311++G(d,p)/LANL2DZ theoretical calculations. The optimized structure of [PbL₂] was found to be very similar to its crystal structure and is also stabilized by two anagostic C–H⋅⋅⋅Pb and one C–H⋅⋅⋅O interactions. Further, the optimized molecule is a pronounced electrophile in an internal side of the bent molecule of [PbL₂] being much more nucleophilic in comparison to the external site, which is mainly electrophilic. The metal cation is also highly nucleophilic facilitating the Pb⋅⋅⋅N teterel bonds, which is reflected in the formation of a 1D supramolecular polymeric chain in the crystal structure of [PbL₂]. The optical properties of complex were revealed by UV‒Vis spectroscopy and spectrofluorimetry in MeOH. It was established that complex is emissive with a band from about 450 to 580 nm.