Spectrophotometric study of the reaction of iodine and bromine with two new macrocycle diamides and di-ortho methoxybenzoyl thiourea in chloroform solution

• Published in: Talanta (Oxford) 1999-07, Vol.49 (3), p.531-538
• Main Authors: Sharghi, Hashem, Massah, Ahmad R, Abedi, Mohamad
• Format: Article
• Language: English
• Subjects: Chemistry; Complexation; Elements and non-metal compounds (oxides, hydroxides, hydrides, sulfides, carbides, ...); Exact sciences and technology; Hallogen; Inorganic chemistry and origins of life; Macrocyclic diamide; Preparations and properties; Spectrophotometry
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/S0039-9140(99)00011-9

The complex formation reactions of iodine and bromine with two new macrocycle diamides ( 1 and 2) and di-ortho methoxybenzoyl thiourea (DOMBT) ( 3) have been studied spectrophotometrically at various temperatures in chloroform solution. In all cases the resulting 1:2 (macrocycle to halogen) or (DOMBT to halogen) molecular complexes were formulated as (macrocycle...X +) X 3 − or (DOMBT... X +) X 3 −. The formation constants of the resulting molecular complexes were evaluated from computer fitting of the absorbance-mole ratio data. For iodine complexes we found that the values of K f vary in the order of 1≈ 2> 3. In the case of bromine complexes the values of K f are larger (>10 8) and vary in the order of 1> 2> 3. The enthalpy and entropy of complexation reactions of iodine with 1, 2 and 3 were determined from the temperature dependence of the formation constants. In all cases it was found that the complexation reactions are enthalpy stabilized, but entropy destabilized.