The solvatochromism and other spectroscopic properties of seven azo dyes were studied, with a particular respect to the role of the solvent basicity, and interpreted with the aid of experimental findings and semiempirical data. The electronic absorption spectra of the dyes examined in different solvents combined with theoretical calculations showed that most of the investigated compounds coexist in the hydrazone and/or azo-enamine-common anion equilibrium or in the solely anionic form depending upon the nature of the solvent employed. These interesting features open up possibilities for the use of these compounds in analytical chemistry as acid-base indicators. Furthermore, both of intermolecular and intramolecular charge transfer equilibria have been reflected by experimental absorption spectra of compounds 4 and 5. The enthalpies of formation predicted at PM6 (COSMO) and PM6/CI (COSMO) for the ground (S(0)) and excited (S(1)) states, respectively have been successfully used for the explanation of the observed bathchromic shift in non-polar solvents. The effect of time on the longer wavelength visible band of compound 7 has been thoroughly investigated.

A series of new azo dyes derived from cyclohexane- 1,3-dione have been synthesized and studied as regards the existence of prototropic tautomerism both in gas phase and in solution. The calculated equilibrium constants predicted by DFT method are in agreement with the NMR experimental results, predicting the existence of all newly studied dyes predominantly or completely in their hydrazone forms. The positions of 1H signals in NMR spectra compare qualitatively with those predicted computationally at the GIAO/DFT level of theory. Different bands observed in electronic absorption spectra have been assigned to the proper electronic transitions. The new band displayed by compound 5 in proton accepting solvents was regarded as a result of ionization. This characteristic band could be useful if the compound was used as analytical indicator. Analysis of electronic absorption spectra confirms the conclusions drawn from calculations and examination of 1H NMR as well as FT-IR spectra.

A series of novel complexes of 4-amino-5-benzyl-4H-1,2,4-triazole-3-thione (ABT), 5-benzyl-4-(benzylideneamino)-4H-1,2,4-triazole-3-thione (BBT), 5-benzyl-4-[(2-hydroxybenzylidene)amino]-4H-1,2,4-triazole-3-thione (HBHT) and 5-benzyl-4-[(4-methoxybenzylidene)amino]-4H-1,2,4-triazole-3-thione (BMT) with the divalent ions Co(II), Ni(II), Cu(II) and Cd(II) have been prepared by direct combination of the ligand and metal chloride salt in ethanol. The structures were determined by elemental analysis, molar conductance, magnetic measurements, thermal behaviour, infrared and electronic spectral data. ABT involves N (amino group) and S donor atoms, BBT and BMT involve N (azomethine) and S donor atoms, both act as neutral bidentate ligands. HBHT involves N, O and S donor atoms, acting as monobasic tridentate ligands. The stoichiometry of these complexes is M:L = 1:1 and/or 1:2. The geometry of the complexes was assigned on the basis of magnetic and electronic spectral data. Tetrahedral and octahedral structures were proposed for the metal complexes. The ligands and their complexes were screened for their antibacterial activity.

An indirect format enzyme-linked immuno-sorbent assay (ELISA) on graphite rods (∅ 0.8 mm x 20 mm) and, for comparison, on microtiter plates has been developed against terbuthylazine. For this purpose, a series of 2-aminoalkyl-4-chloro-6-terbuthyl-s-triazine-2,6-diamine ELISA haptens with alkyl spacer lengths of 2, 4, 6, and 8 CH2 groups has been synthesized. The graphite rods or the microtiter plates were covered by a polymerized glutaraldehyde network, and the ELISA haptens have been coupled by imino coupling to the free aldehyde groups of that network. ε-Aminocaproic acid has been used as an agent to block unspecific binding sites. The ELISA was run in a competitive mode, where the immobilized ELISA hapten and the solute terbuthylazine as a target analyte compete for the solute antibody.

An indirect format enzyme-linked immuno-sorbent assay (ELISA) on graphite rods (∅ 0.8 mm x 20 mm) and, for comparison, on microtiter plates has been developed against terbuthylazine. For this purpose, a series of 2-aminoalkyl-4-chloro-6-terbuthyl-s-triazine-2,6-diamine ELISA haptens with alkyl spacer lengths of 2, 4, 6, and 8 CH2 groups has been synthesized. The graphite rods or the microtiter plates were covered by a polymerized glutaraldehyde network, and the ELISA haptens have been coupled by imino coupling to the free aldehyde groups of that network. ε-Aminocaproic acid has been used as an agent to block unspecific binding sites. The ELISA was run in a competitive mode, where the immobilized ELISA hapten and the solute terbuthylazine as a target analyte compete for the solute antibody.

An indirect format enzyme-linked immuno-sorbent assay (ELISA) on graphite rods (∅ 0.8 mm x 20 mm) and, for comparison, on microtiter plates has been developed against terbuthylazine. For this purpose, a series of 2-aminoalkyl-4-chloro-6-terbuthyl-s-triazine-2,6-diamine ELISA haptens with alkyl spacer lengths of 2, 4, 6, and 8 CH2 groups has been synthesized. The graphite rods or the microtiter plates were covered by a polymerized glutaraldehyde network, and the ELISA haptens have been coupled by imino coupling to the free aldehyde groups of that network. ε-Aminocaproic acid has been used as an agent to block unspecific binding sites. The ELISA was run in a competitive mode, where the immobilized ELISA hapten and the solute terbuthylazine as a target analyte compete for the solute antibody.

Co[(CH3PO3)(H2O)] (1) and Co[(C2H5PO3)(H2O)] (2) were prepared by the hydrothermal method and isolated as blue-violet platelet crystals. They were characterized by X-ray diffraction, FT-IR, TGA-DSC techniques and their magnetic properties studied by a dc-SQUID magnetometer. Compound (1) shows an hybrid layered structure, made of alternating inorganic and organic layers along the a-direction of the unit cell. The inorganic layers contain Co(II) ions six-coordinated by five phosphonate oxygen atoms and one from the water molecule. These layers are separated by bi-layers of methyl groups and van der Waals contacts are established between them. In compound (2), the layered hybrid structure is rather similar to that described for compound (1), but the alternation of the inorganic and organic layers is along the b-direction of the unit cell. The magnetic behavior of (1) and (2) as function of temperature and magnetic field was studied. The compounds obey the Curie-Weiss law at temperatures above 100 K, the Curie C, and Weiss 0 constants for the methyl derivative being C = 3.36 cm3 Kmol-1 and 0 = -53 K and for the ethyl derivative C = 3.62 cm3 K mol-1and 0 = -75 K, respectively. The observed magnetic moments for Co atom at room temperature (i.e. μeff = 5.18 and 5.38 BM, respectively) are higher than those expected for a spin-only value for high spin Co(II) (S = 3/2), revealing a substantial orbital contribution to the magnetic moment. The negative values of 0 are an indication of the presence of antiferromagnetic exchange couplings between the near-neighbors Co(II) ions, within the layers. [Co(CnH2n +1PO3)(H2O)] (n = 1,2) are 2D Ising antiferromagnets at low temperatures.

Co[(CH3PO3)(H2O)] (1) and Co[(C2H5PO3)(H2O)] (2) were prepared by the hydrothermal method and isolated as blue-violet platelet crystals. They were characterized by X-ray diffraction, FT-IR, TGA-DSC techniques and their magnetic properties studied by a dc-SQUID magnetometer. Compound (1) shows an hybrid layered structure, made of alternating inorganic and organic layers along the a-direction of the unit cell. The inorganic layers contain Co(II) ions six-coordinated by five phosphonate oxygen atoms and one from the water molecule. These layers are separated by bi-layers of methyl groups and van der Waals contacts are established between them. In compound (2), the layered hybrid structure is rather similar to that described for compound (1), but the alternation of the inorganic and organic layers is along the b-direction of the unit cell. The magnetic behavior of (1) and (2) as function of temperature and magnetic field was studied. The compounds obey the Curie-Weiss law at temperatures above 100 K, the Curie C, and Weiss 0 constants for the methyl derivative being C = 3.36 cm3 Kmol-1 and 0 = -53 K and for the ethyl derivative C = 3.62 cm3 K mol-1and 0 = -75 K, respectively. The observed magnetic moments for Co atom at room temperature (i.e. μeff = 5.18 and 5.38 BM, respectively) are higher than those expected for a spin-only value for high spin Co(II) (S = 3/2), revealing a substantial orbital contribution to the magnetic moment. The negative values of 0 are an indication of the presence of antiferromagnetic exchange couplings between the near-neighbors Co(II) ions, within the layers. [Co(CnH2n +1PO3)(H2O)] (n = 1,2) are 2D Ising antiferromagnets at low temperatures.