Department of Chemistry, The University of Burdwan, Golapbag, Burdwan 713 104, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2014 Jan 3;117:686-95. doi: 10.1016/j.saa.2013.08.107. Epub 2013 Aug 31.
The photophysical features of non-covalently linked fullerenes C60 and C70 with a designed free-base phthalocyanine, namely, 2,3,9,10,16,17,23,24-octakis-(octyloxy)-29H,31H-phthalocyanine (1) have been investigated employing various spectroscopic tools like UV-vis absorption spectrophotometry, steady state and time resolved fluorescence along with proton NMR measurements in toluene. The ground state interaction between fullerenes and 1 is nicely demonstrated with the appearance of well defined charge transfer absorption bands in the visible region of the electronic spectra. Steady state fluorescence experiment reveals efficient quenching of the excited singlet state of 1 in presence of both C60 and C70. The average values of binding constants for the non-covalent complexes of C60 and C70 with 1 are determined to be 18,150 and ~32,000 dm(3) mol(-1), respectively. The magnitude of K suggests that 1 preferentially binds C70 in comparison to C60 although average value of selectivity in binding is measured to be low (1.75). Time resolved emission measurements establish photoinduced energy transfer from the excited singlet state of 1 to fullerene in toluene. Measurements of free energy of electron transfer and free energy of radical ion-pair formation elicit that C70/1 complex is stabilized more in comparison to C60/1 complex regarding generation of charge-separated state. Proton NMR studies provide very good support in favor of effective ground state complexation between fullerenes and 1. Semi empirical theoretical calculations on fullerene/1 systems in vacuo substantiate the stronger binding between C70 and 1 in comparison to C60/1 system in terms of heat of formation value of the respective complexes, and determine the orientation of bound guest (here C70) towards the plane of 1 during complexation.
采用各种光谱技术，如紫外可见吸收光谱法、稳态和时间分辨荧光光谱法以及质子 NMR 测量法，研究了非共价键合的富勒烯 C60 和 C70 与设计的自由碱酞菁，即 2,3,9,10,16,17,23,24-八（辛氧基）-29H,31H-酞菁（1）的光物理特性。在可见电子光谱区域中出现了定义明确的电荷转移吸收带，很好地证明了富勒烯和 1 在基态下的相互作用。稳态荧光实验表明，在 C60 和 C70 的存在下，1 的激发单重态有效地猝灭。非共价配合物的结合常数的平均值为18,150 和32,000 dm(3) mol(-1)，分别为 C60 和 C70。K 的大小表明，与 C60 相比，1 更倾向于与 C70 结合，尽管结合的平均选择性值较低（~1.75）。时间分辨发射测量表明，在甲苯中，从 1 的激发单重态向富勒烯发生光诱导能量转移。电子转移自由能和自由基离子对形成自由能的测量表明，与 C60/1 相比，C70/1 复合物在生成电荷分离态时更稳定。质子 NMR 研究为富勒烯和 1 之间有效的基态配合提供了很好的支持。真空状态下的富勒烯/1 体系的半经验理论计算，从各自配合物的形成热值方面证实了 C70 与 1 的结合比 C60/1 更强，并确定了在配合过程中结合客体（这里是 C70）相对于 1 平面的取向。
