AMI semi-empirical method was used to optimize the barbituric acid derivatives substituted with glucosyl B1-5 （series B）, and the thiobarbituric acid derivatives substituted with glucosyl T1-5 （series T）. Based on the optimized structures, INDO/CI method was adopted to calculate the electronic spectra. Meanwhile, the second-order nonlinear optical （NLO） coefficients βμ were calculated with the sum-over-state （SOS） formula. The results show that when the number of glucosyl units was increased, ｜βμ｜ values of the barbituric and thiobarbituric acid derivatives were both enhanced, especially for thiobarbituric acid derivatives. It indicates that non-conjugated substituted group could also improve NLO properties of materials when the number of repeated units was increased. Additionally, the absorption bands appearing in UV area are consistent with the proper change of the number of glucosyl units, and consequently it can be concluded that the high transparencies of all systems were scarcely varied.
There are several paths for synthesizing 4,4′ bis(hydroxymethyl) 2,2′ bipyridine, but most of them need strict experimental conditions that are not easy to be overcome. We designed a simple way to prepare this product via the oxidation of 4,4′ bismethyl 2,2′ bipyridine, followed by esterification and reduction. The yield increases and the reaction conditions become genial in contrast to those of other methods. The molecular structure of the final product was confirmed by means of elemental analysis, IR, 1H NMR and MS spectra.
SU Zhong minCHEN Li huaWU Li xinXU Hong binZHU Dong xiaWANG Rong shun
The structures of barbituric acid derivatives substituted with Schiff base were optimized using ab initio HF method at 6-31G basis set. Based on the optimized structures, the electronic spectra were obtained by INDO/CI method. The second-order nonlinear optical (NLO) coefficients βμ were calculated according to the sum-over-states (SOS) formula. In addition, the effect of conjugation on electronic specra and second-order NLO coefficients was investigated. The influence of exchange between C and N atoms as well as the substituted effect on the barbituric acid was discussed. It was indicated that the exchange between C and N atoms on Schiff base is important for enhancing the NLO coefficient of the whole molecule with donor and acceptor (D-A). Meanwhile significant changes in electron donation and acception were observed as substituents changes positions. Among the designed models, molecule lb has maximal βμ value of 124.65×10?-30 esu. About molecule lb, barbituric acid is considered as an accepted electronic group and the position of N atom on Schiff base is close to it.
