Non-transition Ions Research Articles

Synthesis and Characterization of Metal Complexes of Schiff's Base Ligands Derived from 4-Carboxy Hydrazide-5, 6-Diphenyl-3[2-H]Pyridazone

A new ligand, 4-[carboxy-α-(2-hydroxyphenyl) ethylidene hydrazide-5,6-diphenyl-3(2H) pyridazinone (CHDP), were synthesized and characterized by 1H-NMR, IR spectra and elemental analysis. The dissociation equilibrium constant of CHEDP as well as the equilibrium constant for different M+n-CHEDP complexes were reported at different temperatures in 75% (v/v) dioxane-water media and constant ionic strength. The stability constants of CHDP complexes with transition and non-transition ions were evaluated. The thermodynamic parameters were also calculated and discussed. A series of mono nuclear protic M(HL), M(HL)2, ML(HL) and non-protic ML2 complex species were formed in solutions. The structure of the solid complexes formed between CHEDP and cobalt (II), copper (II) and iron (III) are substantiated by elemental analysis, mass spectra, thermal studies (TG and DSC) and IR spectra.

Vibrational study of ionic association in polar aprotic solvents. Isocyanate complexes of non-transition-metal ions

Complexes between alkaline-earth-metal ions M2+ and cyanate OCN− in aprotic solvents are studied by infrared spectrometry in the ν(CN) region (2150–2250 cm−1). In dimethylsulphoxide (DMSO) and hexamethylphosphotriamide (HMPT) isocyanate MNCO ion pairs exhibit a specific ν(CN) band while M(NCO)2 species usually have two ν(CN) bands. Pure alkaline earth cyanates are in part dissociated into MNCO+ and OCN− in DMSO. When they are soluble they are not dissociated in N,N-dimethylformanride (DMF) and in pyridine. The Mg2+-OCN− system in HMPT is the only case where two different ion pairs are observed: p1 at 2205 cm−1 and p2 at 2213 cm−1. The high temperature species p2 is tighter than p1. The reaction p1 → p2 is a desolvation reaction as shown by the large values of ΔH and ΔS (ΔH = 37 kJ.mol−1 and ΔS = 100 J.K−1.mol−1). Similar results are obtained with other non-transition ions (Al3+, Zn2+, Cd2+, Hg2+, Ag+, Tl+). The Δν(CN) wavenumber shift of an ion pair relative to free OCN− (≈ 2137 cm1−) is always positive and roughly proportional to the polarizing power of Mz+. This is in agreement with an isocyanate bonding MNCO. When Mz+ is a soft cation Δν(CN) is smaller than expected. This effect is common to all cases of M…CN bonding. The i.r. spectrum of AgOCN in tetrahydrothiophene (THT) exhibits two bands at 2162 cm' (AgNCO) and 2250 cm−1. The second band is assigned to a bridging group AgOCNAg in (AgNCO)2.

Effects of Some Inorganic Divalent Cations and Protein Kinase C Inhibitors on Endothelium-Dependent Relaxation in Rat Isolated Aorta and Mesenteric Arteries

The effects of nitrendipine and several metal ions possessing Ca2+ antagonistic activity were examined on acetylcholine (ACh) and histamine-induced endothelium-dependent relaxations in norepinephrine (NE)-precontracted rat aortic rings and perfused mesenteric arteries. Nitrendipine (1 nM) profoundly attenuated ACh and histamine-induced relaxations of perfused mesenteric arteries but was ineffective against either agonist in aorta. The transition metal ions Co2+, Mn2+, and Ni2+, but not the nontransition ions (Cd2+, Sn2+, and Zn2+), markedly inhibited ACh and histamine relaxations in the aorta, whereas all metal ions antagonized KCl contractions. At the highest concentration devoid of effect on arterial perfusion pressure, none of the transition metal ions altered endothelium-dependent relaxations in the mesenteric arteries. Endothelium-independent relaxations induced by sodium nitroprusside (SNP) were attenuated by Mn2+ but not by Co2+ or Ni2+. Calmidazolium or W-7 inhibited ACh- and histamine-induced relaxations in both aorta and mesenteric arteries, whereas staurosporine and H-7 were ineffective against aortic relaxations; in mesenteric arteries, staurosporine but not H-7 attenuated both endothelium-dependent and -independent relaxations. We conclude (a) that the transition metal ions most likely inhibit endothelium-derived relaxing factor (EDRF) (NO) release in the aorta through endothelial receptor-operated Ca2+ channels; (b) that the effects of nitrendipine (shared by nifedipine) in mesenteric arteries result from an interaction with a site that may have structural similarities with, but is distinct from, the L-type Ca2+ channel; and (c) that the inhibitory effects of the calmodulin antagonists may reflect an action on endothelial NO synthase.