Template synthesis, spectroscopic studies and biological screening of macrocyclic complexes derived from thiocarbohydrazide and benzil

Abstract

A novel series of complexes of the type [M(TML)X 2 ]; where TML is a tetradentate macrocyclic ligand; M = Co(II), Ni(II), Cu(II) or Zn(II); X = Cl ) , CH 3 COO ) or NO 3 ) have been synthesized by template condensation of benzil and thiocarbohydrazide in the presence of divalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analyses, conductance measurements, molecular weight determination, magnetic measurements, electronic, NMR, infrared and far infrared spectral studies. Electronic spectra along with magnetic moments suggest the six coordinate octahedral geometry for these complexes. The low value of molar conductance indicates them to be non-electrolytes. The biological activities of metal complexes have been tested in vitro against a number of pathogenic bacteria to assess their inhibiting potential.

Antibacterial and antifungal studies of macrocyclic complexes of trivalent transition metal ions with their spectroscopic approach

“…Further, no strong absorption band was observed near 1715 cm −1 , indicating the absence of the >C=O group of the glyoxal moiety. The disappearance of these bands and the appearance of a new, strong absorption band near 1590-1629 cm −1 confirmed condensation of the carbonyl group of glyoxal and the amino group of diaminonaphthalene and the formation of a macrocyclic Schiff base 30 , as these bands may be ascribed to the (C=N) stretching vibrations 31,32 . The lower value of the (C=N) stretching vibrations may be explained on the basis of drift of the lone pair density of the azomethine nitrogen toward the metal atom 33,34 , indicating that coordination takes place through the nitrogen of the C=N group.…”

Antibacterial activity and spectral studies of trivalent chromium, manganese, iron macrocyclic complexes derived from oxalyldihydrazide and glyoxal

“…It was noted that a pair of bands corresponding to n(NH 2 ) at ,3300 cm 21 and 3310 cm 21 were present in the spectrum of oxalyldihydrazide but were absent in the infrared spectra of all the complexes. The disappearance of these bands and appearance of absorption band near ,1600-1615 cm 21 indicates the formation of macrocyclic Schiff's base [23,24] as these bands may be assigned due to n(CvN) [25,26]. The value of n(CvN) is lower than that usually found for azomethine linkage, may be explained on the basis of a drift of lone pair density of azomethine nitrogen towards the metal atom [27,28] indicating the involvement of the pi electrons throughout the macrocyclic framework [16] and confirm that coordination takes place through nitrogen of CvN groups.…”

Mn(II), Co(II), Ni(II) and Cu(II) complexes of a tertraaza macrocyclic ligand: Synthesis, characterization and biological screening

“…It is due to their resemblance with natural proteins like hemerythrin and enzymes. The chemistry of macrocyclic compounds in particular is also important due to their catalytic [8] and biological applications [9].…”