利用B3 LYP/6-31 G(d)方法优化了一系列 N取代1,8-萘酰亚胺类物质的结构,利用含时密度泛函TD-B3 LYP/6-31+G(d)方法及C-PCM模式,计算了它们在气相及二氯甲烷溶剂中的吸收和发射光谱。利用计算得出的前线轨道电子云分布及其对应的能级对它们的取代基对电子吸收光谱的影响进行了讨论。结果表明：此种方法计算出的二氯甲烷溶剂中的1,8-萘酰亚胺的吸收光谱与实验光谱比较吻和。取代 C—O 基团的 C—N 基团及其成环在吸收光谱和发射光谱中发挥了重要的作用。酰亚胺结构上的改性即 C—N 基团的引入及在萘环上取代基一方面引入了结构上的不对称性,导致了衍生物的偶极矩的增大；同时结构上的改性扩展了萘酰亚胺共轭结构。4位取代 NO2衍生物从基态到第一激发态的 Mulliken原子电荷比5位多一些,这意味着5位取代 NO2衍生物提供了较多的电子。对 N(Ph)2和 N(Me)2衍生物而言,他们4位取代衍生物提供了更多的电荷。前线轨道电子云表明： O—C N C—N 基团改性扩展和 N(Me)2,N(Ph)2和NO2取代基拓展了这类分子的π—π∗跃迁范围,从而使得前线轨道能级差降低,它们的吸收和发射光谱也发生了一定程度的红移。对给体取代基而言,它们的4位是电子传输态；对受体取代基 NO2而言,它们的5位是电荷传输态。当NO2基团与 C—O 基团在同一侧及当N(Me)2和N(Ph)2与在 C—N 在同一侧时,此类化合物具有较好的传导特性。从化合物1到4,吸收光谱红移了139 nm。电荷传输越明显,吸收光谱红移的就越多。 O—CNC—O 的结构改性及其电荷传输机理为今后的萘酰亚胺类物质的分子设计提供了设计理论依据。%Using B3LYP/6-31G(d)model,time depended(TD)-B3LYP/6-31+G(d)method and Conductor-like Polarizable Continuum Model (C-PCM)-TD-B3LYP/6-31+G(d)method,we calculated the structure and the absorption and emission spectra of a series of N-substituted 1 ,8-naphthalimides in both gas-phase and di-chloromethane.The influence of the substituents on the electronic absorption spectra and their emission spectra has been discussed on their calculated frontier molecular orbitals contour and their energy levels.Results show that their rings extension from C—N group and the substituents on their naphthalimic ring play an important role in the absorption spectra and the emission spectra properties.Modification of O—C N C—O group and the substituents in their naphthalimic rings breaks the structural symmetry.The Mulliken atomic charges values of NO2 groups from S0 to S1 in 4 positions are a little greater than the 5-positions,which also mean that the 5 position provide more electrons.For MACs of N(Ph)2 and N(Me)2 ,the 4 position substituents provide more charges than that of 5 position.They not only lead to bigger dipole moments,but also extend frontier or-bital contour.Frontier orbitals also show that the modification of O—C N C—N and the introduction N (Me)2 ,N(Ph)2 and NO2 groups extends theirπ—π∗ excitation scope and decreases their energy gap accord-ingly.Besides,those kinds of molecular design enhance intra molecular charge transfer between substituent and naphthalimic ring.Therefore,redshift are shown in their absorption and emission spectra,which is also verified by calculated results.Their absorption and emission spectra in solvent redshift compared with their gas spectra.For the NO2 derivatives,the charge transfer state is in the 5 position substituent compounds.For do-nor substituents,charge transfer state lies in their 4 position compounds.When the C—O group is in the same side with the NO2 group,and the N(Me)2 and the N(Ph)2 are in the different side with the C—O group,compounds have better conduction properties.From compound 1 to compound 4,the redshift of the ab-sorption spectra in dichloromethane is about 1 3 9 nm.The more intramolecular charge transfer,the bigger ab-sorption maximum those compounds shown.Above result is in good agreement with the 5-position NO2 deriva-tives and the 4-position N(Me)2 ,N(Ph)2 derivatives.Above O—C N C—O structural change and their charge transfer mechanism provide design basis for further 1 ,8-naphthalmic derivatives.
展开▼
