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91.
Jeong Hee Kim Sungwoo Yoon Sang-deok Mun Junseong Lee Soo Han Kwon Chanhong Lee 《Journal of organometallic chemistry》2011,696(9):1729-670
A series of monomeric pentamethylcyclopentadienyltitanatranes, [n = 0, 1; n = 1, 2; n = 2, 3], were synthesized by the reaction of Cp∗TiCl3 with corresponding triethanolamines such as (HOCH2CH2)nN(CH2CMe2OH)3 − n (n = 0, L1H3; n = 1, L2H3; n = 2, L3H3), which varied by the number of CMe2 groups adjacent to an OH functionality from 3 (L1H3) to 2 (L2H3) to 1 (L3H3), in the presence of NEt3. All complexes were characterized by elemental analysis and solution 1H and 13C{1H} NMR spectroscopy. Moreover, their solid state structures, which are slightly distorted three-legged piano stool geometry, have been confirmed by single crystal X-ray diffraction analysis. On activation with methylaluminoxane (MAO), these complexes showed good catalytic activity for the polymerization of styrene producing syndiotactic polystyrene (SPS) with high molecular weights. Compounds 1 and 2 bearing more than two pairs of methyl substituents on the side arms of triethanolamines showed the enhanced catalytic activities as the polymerization temperature went up from 50 °C to 110 °C, whereas less bulky complexes 3 and Cp∗Ti(OCH2CH2)3N (4) gave the decreased activities as polymerization temperature rose. Unlike 3 and 4, complexes 1 and 2 in the presence of MAO as a cocatalyst gave SPS with controlled bimodal molecular weight distribution. Bimodal properties were much distinct at low polymerization temperature. 相似文献
92.
采用密度泛函的B3LYP和UB3LYP方法分别优化了一系列[Ru(iph)(L)2]2+ (L=cpy (1), mpy (2), npy (3); 其中iph为2,9-双(1′-甲基-2′-咪唑)-1,10-邻二氮杂菲, cpy为4-氰基嘧啶, mpy为4-甲基嘧啶, npy为4-氮二甲基嘧啶)配合物的基态和激发态结构. 利用含时密度泛函理论(TD-DFT)方法, 结合极化连续介质(PCM)模型计算了它们在丙酮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. 1和2的最高占据分子轨道主要由金属的d轨道和iph配体的π轨道构成, 但是3主要占据在npy配体上, 而它们的最低空轨道主要由iph配体的π反键轨道占据. 因此, 1和2的最低能吸收和发射属于金属到配体(MLCT)和配体内部(ILCT)的电荷转移跃迁, 而3属于两个配体之间的电荷转移(LLCT)跃迁. 三个配合物的最低能吸收分别在509 nm (1), 527 nm (2)和563 nm (3), 其磷光发射分别在683 nm (1), 852 nm (2)和757 nm (3). 这显示出通过调节L配体的π电子给予能力可以改变最低能吸收和发射的跃迁性质和发光颜色. 相似文献