(d-p)π共轭作用对簇合物Mo_2S_4(dtp)_2和Mo_3S_4(dtp)_4·Py电子光谱的影响

比较了含有配位不饱和过渡金属原子簇合物Mo_2S_4(dtp)_2,(Ⅰ)和Mo_3S_4(dtp)_4·Py,(Ⅱ)的紫外—可见电子吸收光谱实验数据和半经验的量子化学方法INDO计算得到的电子跃迁能,讨论了(d-p)π型共轭作用对其电子吸收光谱位移的影响。结果表明,过渡金属簇合物中电子吸收光谱位移,与有机共轭体系有着类似的变化规律,即随着共轭π键数目增加,π-π电子跃迁的吸收光谱红移。

Influence of d-p π Conjugate Interaction upon Electronic Spectrum in Clusters Mo_2S_4(dtp)_2 and Mo_3S_4(dtp)_4·Py

The UV-vis electronic absorption spectra have been observed for the transition metal clusters Mo2S4(dtp)2,(I)and Mo3S4(dtp)4 Py,(II),and the electronic excitation energies have been calculated of the core model Mo2S42+and Mo3S44+using INDO/S-CI method.According to the observed and calculated results it has been assigned for the three types of electronic transfer excitations,ligand-metal charge transfer;d-d electronic transfer within [Mo2] and [Mo3] skeleton;d electron transfer into an unoccupied(d-p)π orbital constructed by Mo and S atoms.We have also discussed how the strength of(d-p)π conjugate interaction influence the electronic absorption spectrum.Comparing the observed results of cluster II with those of I,we will find that the first π→π* energy of d-p type transition decreases as the number of conjugateed bonds increases if the direct interactions between Mo-Mo are considered as non-bonding interactions within puckered rings [Mo2S2]and [Mo3S3],This means that increasing conjugation in an unsaturated cluster compound will lead the first π→π* absorption maximum to shift towards longer wavelengths.The trend is the same as aromatic hydrocarbons.The electronic absorption band with larger π-conjugate interaction over Mo3S3 causes red shift compared with that with smaller π-conjugated interaction,over Mo2S2.