| 520 |
|
|
|a In first Part of this research, the effect of the solvent in the UV absorption bands of a number of Schiff 's bases substituted With different groups directing towards (Ortho, Meta, Para)Positions has been Studied by different theoretical calculations using quantum mechanics methods, such as semi –emperical method ( AM1)) and abintio( HF, MP2) In different polar solvents (CCl4, C6H12, C2H5OH, DMSO) to demonstrate the effect of the solvent on the absorption band of these compounds where the impact of these variables calculated on the transfer of electronic n → π *, π → π* clearly and especially on the transfer of n → π * where the effect of solvent and substitute groups for Schiff bases compounds studied through the values of good correlation coefficient between the values of Δλ with these variables, and physical variables that are calculated include two types of variables, including inductive variables (bond length, angles, charge on the atoms of the functional group) and variables energy or stereochemistry (higher energy Orbital molecular occupied HOMO and lowest energy Orbital molecular unoccupied LUMO, energy disability stereochemistry) In solvents and in different ways and through results that have been obtained and that are consistent with the chemical foundation known where we note the increase in the values of charges on atoms (N, O) with high electro negativity and incompleteness on carbon C atoms, also note the significant increase in the value of S.E. on substituted compounds with groups on the site Ortho for the formation of Hydrogen bonds as well as for the rest of the other values, second step was the statistical analysis of the relationship between the variables calculated with each other and most of the results were good, including the relationship between Δ (L-H), η in the way HF , as the value of R is equal to 1.00 and the relationship between ω, Δ (L-H) be the value of R is equal to 1.00 in the MP2 method and , and then was a statistical analysis of the difference in bands absorbing compounds in cyclohexan reference and other solvent to a statement effect of solvent on these bands, and different ways .
|a where we note that there is good results of the relationship between the values of Δλ and theoretically calculated variables and the relationship of LUMO with Δλ in CCl4 solvent where the value of R = 0.602 in HF method and the highest value of R in MP2 method in DMSO solvent of the elationship between HOMO and Δλ R=0.811either statistical analysis multi eviation MP2 be higher R value in the solvent CCl4 of the relationship between LUMO, C7 as are the R is equal to 0.796 As for the three variables (LUMO, C7, N8-C7-C6 ) in the same solvent shall be the value of R = 816, the mother of four variables in the same solvent and note that the R-value increase of the relationship between the variables (LUMO, C7, N8-C7-C6, N8), which become the value of R is equal to 0.934, and increase its value when introduction of variable ((LHΔ which become 0.951 and this for the way HF, either way MP2 shall be the highest values of R in the solvent CCl4 for two variables (N8, HOMO) as equal to 0.796, and the three variables (N8, HOMO, μ) becomes 0.843, and four variables ( N8, C7, N8-C7-C6, Homo) in the solvent DMSO be the value of R = 0.866, and five variables are the highest value in the solvent ethanol as the value of R = 881 variables (μ, H16-C7-C6, C9-N8-C7 , SE), we note that the relationship be a good way HF greater than the way MP2, and this goes back to the appropriate compounds studied with this method and Tgaribadtha, and we note that the variables affecting the packages absorption in the solvent ethanol was more than other solvent due to the formation of these solvents for the bonds of hydrogen, which works to offset absorbance values towards the wavelength Top (offset red) and this for the results of statistical analysis simple, and the results of statistical analysis of multi were differentiated by the method and the solvent, and in general we note that the most important variables affecting packages absorption was (cargo on an atom of nitrogen and values, HOMO, LUMO, SE) η (M, W, ) on the whole the impact of these variables on the absorption packages good through good correlation coefficient values, and this indicates the presence of some other factors relating to the physical characteristics of the solvent
|
