A STUDY ON THE DONATING PROPERTIES OF 4,5,6,7-TETRATHIOCINO[1,2-B,3,4-B']-DIIMIDAZOLYL-1,3,8,10-TETRAPHENYL-2,9-DITHIONE(PH4TODIT) TOWARDS I2 - CRYSTAL AND MOLECULAR-STRUCTURE OF PH4TODIT.CHCL3

The X-ray structure of Ph4todit · CHC13 (the title molecule) has shown that the crystals are monoclinic, space group P21/n, a = 13. 393(5), b = 20. 764(6), c = 12. 286(5) Å, β = 97. 88(2)°, V = 3384(2) Å3, Z = 4. Solution and refinement of intensity data gave final residuals of R = 0.0551 and Rw = 0.0680, using 2958 observed reflections [I ≥ 2σ;(I)]. A comparison with the previously reported structural data of the corresponding tetraethyl substituted compound (Et4todit) shows that the only significant differences are observed for the N-C-C-N torsion angle (63. 5(7)°, -70(1)° in the Et derivative), and for the values of the torsion angles indicating the orientation of the substituents with respect to the imidazoline ring plane. A spectrophotometric study on the reaction between diiodine and Ph4todit in CHC13 has shown the formation of a 1:1 charge-transfer complex. A computer program has been used to refine the formation constant at six different temperatures and the extinction coefficients in the 260-520 nm range. The enthalpy of formation (δH° = -3. 9(2) Kcal mol-1) falls in usual thione-diiodine complexes range. In the solid state a microcrystalline solid characterized as Ph4todit · 2I2. 2CHC13 has been isolated. FT-Raman spectra on this solid compound show a very strong band attributed to v(I-I) at 172 cm-1. A comparison with the donor behaviour of Et4todit shows that the very small differences detected by means of u. v. visible measurements, suggesting the sequence order Et4todit > Ph4todit, are supported by FT-Raman results, which indicate that the donation of Et4todit produces a lengthening of the I-I distance (v(I-I) at 147 cm-1) larger than in Ph4todit. © 1991, Taylor & Francis Group, LLC. All rights reserved.