An Experimental and Theoretical Study on Some Thiocarbonyl−I₂Molecular Complexes

Abstract

Intermolecular charge-transfer (CT) spectra of several complexes between thiocarbonyl compounds and molecular iodine were studied in the UV-visible region. Equilibrium constants and Gibbs energy changes of 1:1 charge-transfer complexes were determined in solution. Two different kinds of complexes were detected, those which present the CT band in the 300 nm region and those which absorb around 350 nm. Ab initio calculations at HF/LANL2DZ* and MP2(full)/LANL2DZ*//LANL2DZ* were carried out to clarify their structure. Complexes with the CT band around 300 nm correspond to those where the molecule of iodine lies in the same plane of the CdS group, while in those absorbing in the 350 nm region the I 2 moiety is almost perpendicular to that plane. These perpendicular complexes are formed when the substituents around the thiocarbonyl group are voluminous, due to steric hindrance and to the different nature of the HOMO. In both kinds of complexes, the thiocarbonyl-iodine interaction is essentially electrostatic. The substituent effects were analyzed by Taft-Topsom's model. Experimental data in solution and theoretical estimates were found to follow a good linear relationship. The gas-phase basicity of the set of thiocarbonyl compounds investigated toward proton is linearly correlated with their basicity toward molecular iodine in solution. This finding strongly supports previous conclusions regarding the relationship between gas-phase and solution reactivity data.

Theoretical study of quinolines–I2 intermolecular interaction and implications on dye‐sensitized solar cell performance

“…Therefore, the BSSE cannot be neglected. 32 In particular, the value from the MP2 level is larger than those from HF and B3LYP, which agrees with previous papers. 19,35 Consequently, the ⌬E b CP value increases in the following order: HF Ͻ MP2 Ͻ B3LYP.…”

Synthesis, Spectroscopic and Structural Characterization of Novel Diiodine Adducts with the Heterocyclic Thioamides, Thiazolidine-2-thione (tzdtH), Benzothiazole-2-thione (bztzdtH) and Benzimidazole-2-thione (bzimtH)

“…[11,12,17] D·nI 2 complexes may also form where the bonded I 2 molecule interacts with the other diiodine molecules. [11,16,27,28] In our case, thiazolidine-2-thione causes the heterolytic cleavage of the IϪI bond resulting in the formation of the SϪI ϩ ϪS and I 3 Ϫ as a counter anion. This is a rather rare structure and the second according to the best of our knowledge of an anti-thyroidal agent, the first being the one with thiourea (tu).…”

The Diiodine Basicity Scale: Toward a General Halogen‐Bond Basicity Scale

“…The concept of a halogen bond [14] has emerged in recent years [15] from the structures of complexes formed between halogen Lewis acids and Lewis bases in the solid state [16][17][18][19][20] and in the gas phase, [21,22] searches in the Cambridge Structural Database of contacts X···E (in which X = halogen and E = atom of groups 15, 16 and 17) [23,24] and theoretical calculations in vacuo. [25][26][27][28][29][30][31] The halogen bond may be defined [32] as the attractive interaction in which halogen atoms function as electropositive sites. In halogen-bonded complexes YÀX···B, Y is preferably an electron-withdrawing group that may be inorganic (e.g., F, Cl, Br, I or N 3 ) or organic (e.g., CF 3 , C N, C 6 F 5 or C CR).…”

“…[23,25,27,29,[33][34][35][36][37][38][39] Halogen bonding has recently been recognised as a significant interaction in molecular recognition and self-assembly processes, [40,41] and is therefore employed for a wide range of applications in materials, [42][43][44][45] synthetic [46][47][48] and medicinal chemistry. [49][50][51][52] Concerning the fundamentals of halogen bonding, recent studies have focused mainly on structural determinations [18][19][20][21][22] and on quantum mechanical calculations of the bond energy in vacuo at 0 K. [25][26][27][28][29][30][31][53][54][55][56][57][58][59][60] The experimental knowledge of the thermodynamics of the halogen bond at room temperature in solution shows a marked contrast between inorganic and organic halogen-bond donors. In addition to the thousand complexation constants for diiodine, [1] about ...…”