the formation of charge-transfer complexation between dibenzo-15-crown-5 (db15c5) and benzo-12-crown-4 (b12c4) (donor) and iodine is investigated spectrophotometrically in three chlorinated solvents,chloroform, dichloromethane (dcm) and 1,2-dichloroethane (dce) solution at 25°c. the change in polarityof the solvent also doesn’t affect the stoichiometry of the complexes. values of formation cons...

The synthesis and isolation of the sodium salt of cyclo-tri-μ-imidotetraphosphate, i.e. Na4cP4O9(NH)3·H2O, were achieved by the hydrolysis of Na4cP4O8(NH)4·2H2O under very weak acidic conditions, i.e. using 0.2 mol L(-1) propionic acid and the pH-controlled recrystallization procedure. The purity of Na4cP4O9(NH)3·H2O was improved from 2% to 95% by the pH-controlled recrystallization only two ti...

Thermodynamic parameters for protonation of 1,4-bis(3-aminopropyl)-piperazine (BAPP) and its metal complexation with some divalent metal ions were determined in aqueous solution at constant ionic strength (0.1 M NaNO(3)) using a potentiometric technique. The order of -ΔG(0) and -ΔH(0) was found to obey Co(2+) < Ni(2+) < Cu(2+) > Zn(2+), in accordance with the Irving-Williams order. The formatio...

Two calixpyrrole derivatives were synthesised. A p-dimethylaminobenzoyl group was electronically attached to a pyrrole ring, establishing an intramolecular hydrogen bond in a 1,3-alternate conformation. The formation of the H-bond was corroborated by IR, NMR, and X-ray measurements. NMR titration studies reveal that the H-bond is strong enough to block the conversion to a cone conformation, all...

The electric field gradient (EFG) has been calculated in zeolite clusters at the aluminium site surrounded by four SiO4 tetrahedra. Density functional theory (DFT) with the 6-31G** basis set has been employed. Formation of a Brønsted acid site by protonation of one oxygen atom of the AlO4 tetrahedron perturbs the coordination of aluminium, i.e., the corresponding Al-O bond is considerably weake...

The review is mainly concerned with the protonation equilibria of biologically active ligands like amino acids, peptides, DNA constituents, and amino acid esters in nonaqueous media. Equilibrium concentrations of proton-ligand formation as a function of pH were investigated. Also, thermodynamics associated with protonation equilibria were also discussed.

the formation constants and gibbs free energy for the interaction of rnsnclm (n = m = 2, r = me, ph, n-bu or n = 4, m = 0, r = ph) compounds as acceptors, with ml complexes (h2l = n,n'-bis(salicylidene)-2-aminobenzylamine (salabza-h2) and its derivatives, m = mn2+ or zn2+), as donors in n,n'-dimethylformamide (dmf) as solvent were studied. these parameters were measured by using uv-vis spectrop...