摘要
利用DFT B_3LYP/4-31G^(?)方法,对2-硝基-5-(N-甲基-N-十八烷基)氨基苯甲酸(NMOB)进行研究.计算结果发现,苯环的5位碳原子、氨基氮原子以及十八烷基链上与其最临近的两个碳原子所组成的两面角(D)约为90°时,NMOB有最稳构象,在NMOB自交替膜中,NMOB即以这种构象存在;而D=180°时,体系总能量较最稳构象高出31.57kJ/mol,这种构象存在于NMOB/花生酸镉(CdA)交替膜中.较小的能量差异使NMOB容易在两种构象之间进行转化,在NMOB/花生酸镉(CdA)交替膜中因受到花生酸直立构象紧密排列的诱导作用,NMOB分子以能量相对较高的构象存在.
In this paper, the NMOB molecule is studied in terms of DFT B3LYP method using 4 - 31G* basis set. The geometry of NMOB was obtained by replacing the ethyl in 2 - nitro - 5 - ( N - methyl - N - ethyl)amino benzoic acid (NMEB) whose geometry was optimized by B3LYP/3 - 21G* with octadecyl from dimethyloctadecylamine (DMOA) optimized by PM3. We defined the dihedral angle as D, which was composed of the amino nitrogen atom, the carbon atom in benzene ring connecting directly to the amino nitrogen atom and the two carbon atoms in octadecyl group nearest to the nitrogen atom. It was found that the system potential curve had minimums when the D of NMOB was equal to about 90° or 270°. There was a maximum at 180° whose system potential was 31 kJ/mol higher than that of 90° and 28 kJ/mol than that of 270°(shown in Tab. 2 and Fig. 2) . The most stable conformation of NMOB ( D≈90° or 270°) exists in its self- alternated multilayer. In NMOB/Cadmium arachidate(CdA) alternated film, NMOB exists in the form of vertical conformation (D = 180°). We suggested the unstable vertical conformation of NMOB come from the inducement of CdA, which stood, vertically on the substrate.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
1999年第4期372-376,共5页
Acta Chimica Sinica
基金
教育部重点科技项目资助
关键词
LB膜
构象
NMOB
自交替膜
LB film, conformation, ab initio, 2 - nitro - 5 - (N - methyl - N - octadecyl) amino benzoic acid (NMOB)
