Synthesis, characterization and thermodynamic studies of complexes of dimethyl, diethyl, and diphenyltin(IV) dichlorides with (2H)-1,4-benzothiazine-2,3-(4H)-dione dioxime

The diorganotin(IV) compounds, [Me2SnCl2(H2L)], [Et2SnCl2(H2L)] and [Ph2SnCl2(H2L)] (H2L = (2H)-1,4-benzothiazine-2,3-(4H)-dione dioxime), were synthesized by treating the appropriate diorganotin(IV) dichloride with H2L in anhydrous ethanol. These complexes were characterized by IR, MS, UV-Vis, and 1H NMR. Thermodynamic studies of the reported complexes have been carried out and their stability were found in the order: [Me2SnCl2(H2L)] > [Et2SnCl2(H2L)] > [Ph2SnCl2(H2L)]. Theoretical calculations at the HF/3-21G* level showed that structures with alkyl groups at axial positions are more stable than their counterparts having alkyl groups at equatorial. KEY WORDS: Diorganotin(IV) dichloride, vic-Dioxime, (2H)-1,4-Benzothiazine-2,3-(4H)-dionedioxime, Thermodynamic studies Bull. Chem. Soc. Ethiop. 2012, 26(1), 85-94.DOI: http://dx.doi.org/10.4314/bcse.v26i1.

A new approach on diminutive effects for non-covalent interactions: fused bicyclic hydrogen-bonded complexes of hypohalous acids with fluoromethanol

<p>The computational study of dimer and trimer complexes of fluoromethanol (CH₂FOH) with one or two molecules of hypohalous acids (HOX; X = F, Cl or Br) was carried out at the MP2/aug-cc-pVDZ computational level. Also to show the reliability of these results, the binding distance and interaction energy have been compared with large basis set aug-cc-pVTZ level for some systems. The 1:1 ratio gives two different hexagonal and heptagonal ring complexes and the 1:2 ratio of CH₂FOH/HOX leads to fused bicyclic hydrogen-bonded trimer adducts constructed from hexagonal and heptagonal rings. The results show diminutive effects in the range of 0.36–0.78 kcal/mol for the trimer bicyclic systems. Redshifts with bond elongations were observed for H–O and C–F bonds, while blueshifts along with bond contractions were seen for the C–H and the X–O bonds. The CH₂FOH/HOX complexes were analysed using the Quantum Theory of Atoms in Molecules (QTAIM) and natural bond orbital methodologies.</p> <p></p

Theoretical Study of Mixed Hydrogen and Dihydrogen Bond Interactions in BH 4 (NH 3 ) n − Clusters

Ab initio calculations were used to analyze interactions of BH 4 − with 1-4 molecules of NH 3 at the MP2/6-311++G(d,p) and the B3LYP/6-311++G(d,p) computational levels. In addition to H 3 B-H⋅ ⋅ ⋅ H-NH 2 dihydrogen bond, the H 2 N-H⋅ ⋅ ⋅ NH 3 hydrogen bonds were also predicted in clusters. Negative cooperativity in clusters constructed from mixed H 3 B-H⋅ ⋅ ⋅ H-NH 2 dihydrogen and H 2 N-H⋅ ⋅ ⋅ NH 3 hydrogen bonds are more remarkable. The negative cooperativity increases with size and number of hydrogen bonds in cluster. The B-H stretching frequencies show blue shifts with respect to cluster formation. Greater blue shift in stretching frequencies was predicted for B-H bonds which did not contribute to dihydrogen bonding with NH 3 molecules. The structures were analyzed with the atoms in molecules (AIM) methodology

<b>Comparison of acceptor properties for interaction of TCNE and DDQ with some free base porphyrins</b>

The interactions of free base porphyrins with tetracyanoethylene and 2,3-dichloro-5,6-dicyanobezoquinone as acceptors result in charge-transfer adducts of composition 2:1 of acceptor to donor, [(acceptor)2 (donor)]. Formation constants, K, as well as the thermodynamic parameters, ΔHº, ΔSº, and ΔGº were determined by UV-Vis titration method for the adducts. Surprisingly, the values of ΔSº &rsaquo; 0 and ΔHº &rsaquo; 0 for TCNE are in contrast to ΔHº &rsaquo; 0 and ΔSº &rsaquo; 0 for DDQ. Negative values of ΔGº make these interactions favorable in the both cases

Theoretical investigation of molecular interactions between sulfur ylide and hypohalous acids (HOX, X═F, Cl, Br, and I)

<p>In the present study, the complexes of sulfur ylide (SY) with hypohalous acids (HOX; X═F, Cl, Br, and I) were theoretically studied using the MP2/aug-cc-pVTZ computational level. Four types of structures were obtained for these complexes including two kinds of hydrogen bonds (HBs) (SY: HOX─I and SY: HOX─II) and two kinds of halogen bonds (SY: XOH─I and SY: XOH─II). According to the energetic results, the SY:XOH─I complexes are stronger for X═Br and I, while the SY:HOX─I complexes are favorable for X═Cl and Br; also, the SY:HOX─II complexes are stronger than SY:XOH─II except for SY:IOH─II, which is stronger than its counterpart (SY:HOI─II). Moreover, on comparing SY:HOX─I and II HBs complexes, the former is more stable than the latter, while between the SY:XOH─I and II halogen bond complexes (X═Cl, Br, and I), the SY:XOH─I ones are more stable. The strength, properties, and nature of interactions were also analyzed using the natural bond orbital and atoms in molecules theories.</p