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چکیده
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A new 2D coordination polymer of lead(II) with N'-isonicotinoylpyrazine-2-carbohydrazonamide (HL) was readily produced by reacting with an equimolar amount of Pb(ClO4)2 in aqueous methanol solution. The resulting metallocomplex was isolated in the form of yellow prism-like crystals of {[PbL](ClO4)·0.4H2O}n, suitable for a single crystal X-ray diffraction analysis, and was studied using FTIR and 1H NMR spectroscopy, and single crystal X-ray diffraction. The oxygen atoms of the ClO4− anion are disordered over two positions with an occupancy ratio of 60 % to 40 %. The minor occupancy is accompanied with the crystal water molecule, which, thus, yields 0.4 molecule per one [PbL](ClO4). Analysis of the crystal structure of the discussed complex allowed to reveal the formation of a dinuclear dimeric species [Pb2L2]2+ from the [PbL]+ cations through a pair of Pb···N tetrel bonds formed with the amide nitrogen atoms, which is further reinforced by a pair of π···π interactions formed between the pyrazine and pyridine rings. Three oxygen atoms from two perchlorate anions complete the coordination sphere (N4O4) of the metal cation, yielding an anionic {[PbL]2(ClO4)4}2− species, which is stabilized by a pair of N–H···O hydrogen bonds, formed by one of the NH2 hydrogen atoms and one of the oxygen atoms of the major occupancy of an adjacent perchlorate anion. In the crystal packing, the cations [PbL]+ are linked through the Pb–N coordination bonds formed with the pyridine nitrogen atom, yielding a 1D cationic coordination polymers {[PbL]n}n+ of a zig-zag structure, which, in turn, are linked into a 2D coordination network. The topology of this 2D network disclosed a uninodal 3-connected net of fes with the point symbol of (4·82). 2D layers are stacked with each other int a 3D supramolecular framework, which voids are filled by the perchlorate anions and crystal water molecules. DFT calculations have been performed to characterize the Pb···N/O tetrel bonding interactions along with more conventional hydrogen bonding that are crucial in the generation of the coordination polymer and its final 3D architecture.
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