[Os(PH_3)_2(CN)_2(N^N)]配合物的溶剂化显色效应

The solvatochromism effect on a series of [Os(PH_3)_2(CN)_2(N^N)]complexes

采用HF/DFT的混合泛函PBE0和UPBE0优化了配合物[Os(PH3)2(CN)2(N^N)](其中N^N=2,2′-吡啶)的基态和激发态结构.在基态和激发态结构的基础上,利用含时密度泛函理论(TD-DFT)方法,结合极化连续介质(PCM)模型分别计算了它在二氯甲烷(1)、甲醇(2)、气态(3)和乙腈(4)溶液中的吸收和发射光谱.研究结果表明:优化得到的几何结构参数和相应的实验值符合得非常好.在极性较大的溶剂(2和4)中Os—P(1)和Os—C(1)键较长,Os—N(3)键较短,溶剂的极性会影响配合物的电子云分布.配合物在1-4溶剂中的最低能吸收和发射均来自分子轨道68→71的激发,该激发被指认为[d(Os)+π(CN)+π(N^N)→π*(N^N)]的跃迁具有混合的MLCT/LLCT特征.配合物在1-4溶剂中的最低能吸收和发射分别在471,410,488和445nm以及598,536,634和545nm,表明随着溶剂极性的逐渐增大(3<1<4<2),最低能吸收和发射发生明显的蓝移.这显示出通过改变溶剂极性可以调节配合物的发光颜色.

The geometries of ground and excited states of Os complexes [Os（PH_3）_2（CN）_2（N^N）] （N^N=2,2′-bipyridine） were optimized by a hybrid Hartree-Fock/density functional model approach based on the Perdew- Burke-Erzenrhof （PBE0） and UPBE0 functional, respectively. Time-dependent density functional theory （TD-DFT） method together with the polarized continuum model （PCM） were used to obtain their absorption and phosphorescent emission spectra in dichloromethane （1）, methanol （2）, gaseous （3） and acetonitrile （4） media based on their optimized ground and excited- state geometries. The results revealed that the optimized structural parameters agreed well with the corresponding experimental results. In more polar solvent （2 and 4 ）, the bond length of the Os-P （1） and Os-C（1） were longer, the bond length of the Os-N（3） was shorter, the polarity of solvent could affect the distribution of electron cloud of complexes. The lowest-lying absorptions and emis- sions of complexes at 1 -4 solvent are contributed by the electron excitation from 68→71（LUMO）, and the transitions are all attributed to [d（Os）＋π（CN）＋π（N^N）→π＊（N^N）] transition with MLCT/ LLCT character. At the TD-DFT and PCM levels, 1-4 solvent give rise to lowest-lying absorptions at 471, 410, 488 and 445 nm and phosphorescent emissions at 598, 536, 634 and 545 nm, respectively. The calculation results show that the lowest-energy absorptions and emissions are blue-shifted with the increasing of the polarity of solvent in the order of 3 〈1〈4 〈2. It is shown that the phospho- rescent color can be tuned by changing the polarity of solvent.