Spectrophotometometric and potentiometric studies on cr [lll], Mn [ll], Fe[III], Co [ll] and Ni [ll] complexes with 5,7-dinitroso-6-hydroxy-4-methylcoumarin

The composition, stability constants and optimal formation conditions of the complexes of Cr3+, Mn2+, Fe3+, Co2+ and Ni2+ with 5, 7-dinitroso-6-hydroxy-4-methylcoumarin have been studied spectrophotometrically. The stoichiometries of the complexes showed that 1: 1 and 1: 2 [M: L] species were formed and the influence of foreign ions was investigated. The ionization constants [pKa] of the investigated ligand and stability constants of the metal ions complexes were determined, potentiometrically, in 40% ethanolic solution

Ionization constants and spectral properties of some chromone azo dyes

Some new chromone containing azo dyes were prepared. The ionization constants of the chromone and its azo dyes were determined potentiometrically and spectrophotometrically. The effects of substituent, medium, and temperature on the ionization of these compounds were discussed. The effect of solvent polarity on electronic absorption spectra was discussed also. The IR spectra of the compounds have been investigated and discussed in relation to molecular structure

Molecular complexes of some sulfa drugs with chloro-p benzoquinones

The molecular complexes of sulfanilamide, sulfaguanidine, sulfapyridine, sulfadiazine, sulfamerazine, sulfadimidine and sulfathizole with chloranil and dichlorodicyano-p-benzoqunone have been prepared and investigated by IR, electronic absorption and proton magnetic resonance spectroscopy. Primary interaction between the different donors and acceptors is through pi-pi* electron transfer from the HOMO on the donor to the LUMO on the acceptor. In addition, pi-pi* and/or hydrogen bonding can be operative within the molecular complexes

Structure and substituent effect on the characteristics of some lanthanide chelates with 3-acetyl-1,5-diarylformazans

The ionization constants of a homologous series of 1-[0- carboxyphenyl]-3-acetyl-5-arylformazans have been determined potentiometrically. The substituent effect on the pK values was discussed. Furthermore, the stability constants of the formazan chelates with trivalent La, Gd and Er ions were determined. Linear relation between sigma pK of the formazans and log K of their chelates was established. The chelation affinities of formazans towards La, Gd, Er were discussed in relation to the metal ionic size, basicity and number of donor atoms in the formazan molecule. The 1: 2 [M: L] solid chelates were isolated and characterized by several techniques as ML HL.nH2O where HL = formazan, M = La, Gd or Er ion and n = 0-6

Spectroscopic studies on schiff bases containing pyrimidine and pyrazine nucleus

Schiff bases of 2-aminopyrimidine and 2-aminopyrazine with benzaldehyde and its derivatives have been prepared and investigated by IR, UV and 1H-NMR spectroscopy. The results are discussed in terms of molecular structure and substituent effects. It is found that the CH=N linkage is coplanar with the benzal ring. The ionization potentials of the Schiff bases are determined using absorption spectra

Novel substituted-aminocoumarins as potential antimicrobial agents

The synthesis of a novel series of substituted-aminocoumarins [II], [III] and [IV] and the preliminary evaluation of their in vitro antimicrobial activity are described. The reaction of 4- hydroxycoumarin [I] with a number of primary or cyclic secondary amines afforded the corresponding 4-aminocoumarins derivatives [II]. Likewise, reacting the same substrate with different sulpha-drugs furnished the respective 4-[4-[N-substituted-sulphamoylphenyl]] -aminocoumarins [III]. On the other hand, Mannich reaction of [I] with formaldehyde and certain amines yielded the desired 4-hydroxy 3- substituted-aminomethyl-coumarins [IV]. The antimicrobial screening has revealed that some of these novel compounds possess moderate activity against Bacillus subtilis and Bacillus pumitis

Spectrophotometric studies of V [IV], Co [II], Ni [II], Cu [II] and Zn [II] complexes with 8- [o-hydroxyphenylazo] 7-hydroxy-4- methyl-coumarin

The complexes formed between 8-[o-hydroxyphenylazo] - 7 -hydroxy-4-methylcoumarin [I] and V [IV], Co [II], Ni [II], Cu [II] and Zn [II] were studied spectrophotometrically in solutions. The different complexes were characterized and their stoichiometric ratios were thoroughly investigated. Methods for the spectrophoto-metric determination of these metals and Spectrophotometric titration using EDTA were reported. The interference of several metal ions was reported