Aggregation of malonic acid dihydrazide with thymine and 2,6-diaminopyridine in the presence of copper(II) and zinc(II) chlorides: Synthesis, characterization and molecular conducting properties

Abstract

Malonic acid dihydrazide (MADH) earlier condensed with thymine (Thy) and 2,6-diaminopyridine (DAP) separately has been complexed with CuCl₂.2H₂O and ZnCl₂. Resulting solids have been assigned the compositions Cu(MADH)₂Cl₂.2Thy.5H₂O, (1); Cu(MADH)₂Cl₂.2DAP.8H₂O, (2); Zn(MADH)vCl₂.2Thy.2H₂O, (3); and Zn(MADH)₂Cl₂.2DAP.10H₂O, (4) on the basis of elemental analysis and FAB mass data, and further characterized by the IR, NMR, UV-vis and EPR spectra together with their powder X-ray diffraction and microstructures. Peak widths in almost all complexes have been found to be higher than those introduced by instrumental broadening in their XRD data which clearly indicates size restriction on the coherently scattering domain, thus characterizing the complexes with larger motifs. Significant differences in solid-state electrical conductances between Thy-based complexes and DAP-based complexes are noted as closer linear fit of log σ versus 1000/T curve is observed for the former whereas polynomial relationship is being followed by the latter. In optical micrographs, MADH.DAP consists of lamellae and connected network of granules in local regions. However, the addition of Zn(II) chloride in this system leads to the formation of fine colonies which totally disappear in the Cu(II) complex. Presence of H-donors in DAP and both the H-donor and H-acceptors in Thy-based complexes have been observed as a variable parameter in their structural networking.