Charge transfer complexes between I2 and selenoamido entity contained in some pentaatomic rings

Spectrophotometric studies on the charge transfer complexes between molecular iodine and some pentaatomic rings containing the selenoamido entity, i.e. $\text{X · CH}{}_2\text{· CH}{}_2\text{· NR · C}$ = Se (where for R = H, X = CH₂, NH, NMe, NEt, S; for R = Me, X = NMe, S; for R = Et, X = NEt) have been carried out in CCl₄ and CH₂Cl₂ solutions. The presence of isosbestic points are indicative of 1:1 molecular adducts.The simultaneous determination of the stability constants (K) and molar extinction coefficients (?) has been carried out by using no linear least square methods. In order to improve the reliability of K and ? a criterion for selecting the experimental points is reported. The association constants obtained for the present compounds and the thioketonic isologues are correlated with the ionization energies of the lone pairs of the exoatom.