Halogen complexes theoretical studies

Haber process, 116 Hafnium complexes alkyl alkoxy reactions, 358 phthalocyanines, 865 porphyrins, 823 pseudohalides, 228 Hafnium(IV) complexes cupferron, 512 Haloarsine compounds, 1004 Halogen complexes, 675-687 bridge systems, 677-684 asymmetry, 678 theoretical studies, 682 double bridged, 681... 

There have been both experimental and theoretical studies to probe the degree of concertedness in gas-phase substitutions as shown in Scheme 1. Is (2) an intermediate with a finite lifetime, or are the addition and elimination steps concerted so that (2) is a transition state Experimental molecular beam studies on the femtosecond time-scale have been reported for the reaction of chloride ions with the iodobenzene cation to yield chlorobenzene and iodine. The results show an 880 fs reaction time for the elimination process, indicating a highly non-concerted process, so that here the er-complex is an intermediate rather than a transition state.12 The reactions of halobenzene cations with ammonia have been interpreted in terms of the formation of an addition complex which may eliminate either halogen, X, or hydrogen halide, HX, depending on the nature of the halogen.13... 

A theoretical study of [CpsReSOS ] has led to the prediction of a triplet ground state.The study also examined the related [ (hmb) 3M3X5 ](X=halogen) complexes of the early transition elements. 

It can be mentioned the work of Cerecetto et al. [ 133,134] where the anti-7 cruzi activities of a series of QDO and its vanadyl complexes were correlated with theoretical physicochemical descriptors. On the one hand, a clear two-variable correlation was found between both QDO-antiparasite activity and theoretical lipophilicity and LUMO energy [133]. The equation confirms some previously observed aspects, i.e., that the presence of an electron-withdrawing substituent, like halogen, in 5-8-positions produces more active compounds. On the other hand, it was found that the anti-T. cruzi response of a family of QDO-vanadyl complexes depends on the lipophilic properties and the electronic properties, am, of 6-7-substituents [134], Another QSAR study involving PDO derivatives with selective hypoxic cytotoxicity was performed by these researchers [145]. In this case, electrochemical properties, expressed as pc, together with lipophilicity correlated to the fraction of cell survival in hypoxia finding that when the redox potential of the N-oxidc moiety decreases the hypoxic cytotoxicity increase. 

The complexity of individual halogenation mechanisms has become clear in more recent years from the diverse isomer distributions observed under different reaction conditions. Quantitative product studies are beginning to make a welcome appearance, but kinetic studies are almost wholly lacking. The recent kinetic work on the iodination of imidazole may signal the onset of improvement in this aspect. On the theoretical side, much attention has been given to the several possible quantum mechanical approximations applicable to heterocyclic substitution. Here again the lack of ample quantitative... 

The next chapter reviews the reactions of free atoms and radicals which play an important role in the modeling of complex processes occurring in the polluted atmosphere and in combustion chemistry. J. Jodkowski discusses the computational models of the reaction rate theory most frequently used in the theoretical analysis of gas-phase reaction kinetics and presents examples of the reactions of reactive components of the polluted atmosphere, such as 02, NOx, OH, NH2, alkyl radicals, and halogen atoms. Kinetic parameters of the reactions under investigation are provided in an analytical form convenient for kinetic modeling studies. The presented expressions allow for a successful description of the kinetics of the reaction systems in a wide temperature range and could be used in kinetic studies of related species. 

---