Quantum mechanical study of tautomerism of methimazole and the stability of methimazole–I2 complexes

Quantum mechanical investigation of the charge transfer molecular complexes of methimazole with I2, IBr and ICl

“…The inner iodine atom shows an amphoteric behaviour in the planar complexes and acts simultaneously as an electron acceptor from sulfur and electron donor to the acidic H of the amidic NH group. The unscaled harmonic frequency shift Dm(NH) = 103.7 cm À1 for M-I 2 (planar), presently calculated, is close to the experimental value, 90 cm À1 [4] and closer than other computational studies [12], confirming the reliability of the level of theory employed in the present work. Good consistency is also observed between the Dm(NH) values of the M 0 -IY complexes calculated in the present work, $60 cm À1 , and the experimental results ranging from 52 to 61 cm À1 for the diiodine complexes of a series of compounds belonging to the imidazolidine family [23].…”

“…The 6-31G+(d) basis set was used for sulfur and the 6-31G(d,p) one for all other Table 2 The occupation numbers of NBOs in atomic units atoms. Taking into account the large size of the molecules under consideration and the high number of atoms involved, the level of theory employed in the present study may be considered to be satisfactory and comparable or even higher than the levels of theory employed in the study of similar systems by other workers [12]. The NBO analysis was performed with version 3.1 of the Gaussian98 algorithm at the same level of theory for both isolated M, M 0 compounds and M-IY, M 0 -IY (Y = Cl, Br, I) complexes.…”

“…They also present a great deal of interest from the purely scientific point of view as two electronic structures of different connectivity and stability are possible to be formed, the charge transfer (CT) complexes bearing a linear E-X-Y arrangement and the hypervalent T-shaped adducts presenting a X-E-Y geometry [7,8]. The many crystallographic and theoretical investigations carried out on these systems [9][10][11][12][13][14] have revealed quite interesting correlations between the kind of the adduct formed and its various physicochemical properties from one side and the electronegativity of the halogen and the feasibility for the LEX + +Y À dissociation channel on the other [15,16]. The formation of T-shaped adducts was suggested to prevail if the electronegativity value of the halogen is higher than that of E, while charge transfer (CT) adducts are formed in the reverse case.…”

Simultaneous Interactions of Ru Dye with Iodide Ions and Nitrogen-Containing Heterocycles in Dye-Sensitized Solar Cells

“…This interaction can be considered as a measure of the relative stability of these complexes. 37 The values of the charge-transfer energy, E (2) , corresponding to this interaction in the vertical complexes are smaller than those in the horizontal complexes. Therefore, the σ*(1)I-I antibond occupancies in the vertical complexes diminish with respect to the values in the horizontal complexes.…”

Quantum mechanical investigation of 2,3-dihydro-1-methyl-2-thioxopyrimidin-4(1H)-one tautomers and their complexes with iodine.

“…Methimazole, carbimazole and propyltiouracilare anti-thyroid drug which depress the formation of thyroid hormones by inhibiting the first step of the hormonal biosynthesis which is the incorporation of oxidized iodine into tyrosine residues in the large thyroid hormone precursor molecule, thyroglobulin [1][2][3][4] .Pyrimidinderivates too, are known as iodine absorbent in a human body [5][6][7][8][9][10] . Each compound with a powerful complex with…”