<b>CNDO/SCF molecular orbital structural studies and charge transfer complex formation between 4,4’-dimethoxydiquinone and uracil</b>

Through CNDO/SCF molecular orbital calculations, the structure of 4,4’-dimethoxy- diquinone (DQ) has been discussed and compared with some related compounds. The electron transfer between DQ and uracil was studied in ethanol as an interaction medium. The ionization potentials and the electron affinities of the studied molecules have been calculated in addition to their charge densities giving the columbic potential energy of the donor and acceptor. The experimental charge transfer band lies at 500 nm. The electronic transitions have been calculated for the singlet and triplet transitions in uracil and DQ molecules using the SCF eigenvectors of the two HOMO’s, &psi;n-1 and &psi; n, and the two LUMO’s, &psi; n+1 and &psi; n+2, using CI theory. The calculated electronic transitions are compared with those of the experimental data to verify the non-planar structure of the DQ molecule

Spectrophotometric study of acid-base equilibria of 4-(2-benzothiazolylazo)resorcinol and 4-(2-benzothiazolylazo)salicylic acid

789-793The visible absorption spectra of 4-(2-benzothiazolylazo)resorcinol and 4-(2-benzothiazolylazo) salicyclic acid have been recorded in aquo-organic solvent mixtures in the pH range 0.5-12.0. The spectral changes have been explained in terms of shifts in equilibria amongst different molecular and ionic species of BTAR and BTAS existing in solution. The pKa values corresponding to the different ionisation steps have been determined at 25°C and 1=0.1 M (KNO3) by graphical analysis of the absorbance-pH curves

Spectroscopic Studies on 4-(p-Dimethylamino)benzylidene/phenylimino-3-methyl-1-phenyl-2-pyrazolin-5-ones

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