Wu Jian-Jun, Li Na, Li Ke-An, Liu Feng
Beijing National Laboratory for Molecular Sciences, The Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China.
J Phys Chem B. 2008 Jul 10;112(27):8134-8. doi: 10.1021/jp802482f. Epub 2008 Jun 18.
The J-aggregation behavior of diprotonated tetrakis(4-sulfonatophenyl)porphyrin (H2TPPS4(2-)) in aqueous solution in the presence of the hydrophilic ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) was investigated in detail using UV-vis absorption spectroscopy, fluorescence spectroscopy, resonance light scattering (RLS) spectroscopy, Raman spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. With the addition of bmimBF4, increasing peaks appeared at a wavelength of 490 nm in the absorption spectra to account for the formation of H 2TPPS4(2-) J-aggregates. In addition, the experimental results also showed decreased fluorescence emission, enhanced RLS signals, intensified Raman scattering peaks, and the disappearance of NMR signals to further indicate that porphyrin J-aggregates exist in the studied system. NMR shifts of bmimBF 4 toward high field occurred corresponding to H2, H4, and H5 in the cationic imidazolium ring (bmim+), suggesting that bmim+ enters the magnetic shielding domain of the anionic phenyl sulfonate ion owing to the association process between the "large" cation and anion. Additionally, the fact that the absorption spectral shifts occurred in the nonprotonated porphyrin TPPS4(4-) further indicates the existence of the ion association effect of bmim+, which functions as an important factor in porphyrin aggregation.
利用紫外可见吸收光谱、荧光光谱、共振光散射（RLS）光谱、拉曼光谱和核磁共振（NMR）光谱，详细研究了在亲水性离子液体1-丁基-3-甲基咪唑四氟硼酸盐（bmimBF4）存在下，双质子化四（4-磺基苯基）卟啉（H2TPPS4(2-)）在水溶液中的J-聚集行为。随着bmimBF4的加入，吸收光谱中在490 nm波长处出现了越来越多的峰，这说明形成了H2TPPS4(2-) J-聚集体。此外，实验结果还表明荧光发射降低、RLS信号增强、拉曼散射峰增强以及NMR信号消失，进一步表明在所研究的体系中存在卟啉J-聚集体。阳离子咪唑环（bmim+）中的H2、H4和H5对应的bmimBF4的NMR位移向高场发生，这表明由于“大”阳离子与阴离子之间的缔合过程，bmim+进入了阴离子苯基磺酸根离子的磁屏蔽区域。此外，非质子化卟啉TPPS4(4-)的吸收光谱发生位移这一事实进一步表明了bmim+的离子缔合效应的存在，这是卟啉聚集的一个重要因素。
